Libraries: Move to Userland/Libraries/

Userland/Libraries/LibCore/Account.cpp

@@ -0,0 +1,316 @@
+/*
+ * Copyright (c) 2020, Peter Elliott <pelliott@ualberta.ca>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Base64.h>
+#include <AK/Random.h>
+#include <LibCore/Account.h>
+#include <LibCore/File.h>
+#include <grp.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+namespace Core {
+
+static String get_salt()
+{
+    char random_data[12];
+    AK::fill_with_random(random_data, sizeof(random_data));
+
+    StringBuilder builder;
+    builder.append("$5$");
+    builder.append(encode_base64(ReadonlyBytes(random_data, sizeof(random_data))));
+
+    return builder.build();
+}
+
+static Vector<gid_t> get_gids(const StringView& username)
+{
+    Vector<gid_t> extra_gids;
+    for (auto* group = getgrent(); group; group = getgrent()) {
+        for (size_t i = 0; group->gr_mem[i]; ++i) {
+            if (username == group->gr_mem[i]) {
+                extra_gids.append(group->gr_gid);
+                break;
+            }
+        }
+    }
+    endgrent();
+    return extra_gids;
+}
+
+Result<Account, String> Account::from_passwd(const passwd& pwd, Core::Account::OpenPasswdFile open_passwd_file, Core::Account::OpenShadowFile open_shadow_file)
+{
+    RefPtr<Core::File> passwd_file;
+    if (open_passwd_file != Core::Account::OpenPasswdFile::No) {
+        auto open_mode = open_passwd_file == Core::Account::OpenPasswdFile::ReadOnly
+            ? Core::File::OpenMode::ReadOnly
+            : Core::File::OpenMode::ReadWrite;
+        auto file_or_error = Core::File::open("/etc/passwd", open_mode);
+        if (file_or_error.is_error())
+            return file_or_error.error();
+        passwd_file = file_or_error.value();
+    }
+
+    RefPtr<Core::File> shadow_file;
+    if (open_shadow_file != Core::Account::OpenShadowFile::No) {
+        auto open_mode = open_shadow_file == Core::Account::OpenShadowFile::ReadOnly
+            ? Core::File::OpenMode::ReadOnly
+            : Core::File::OpenMode::ReadWrite;
+        auto file_or_error = Core::File::open("/etc/shadow", open_mode);
+        if (file_or_error.is_error())
+            return file_or_error.error();
+        shadow_file = file_or_error.value();
+    }
+
+    Account account(pwd, get_gids(pwd.pw_name), move(passwd_file), move(shadow_file));
+    endpwent();
+    return account;
+}
+
+Result<Account, String> Account::from_name(const char* username, Core::Account::OpenPasswdFile open_passwd_file, Core::Account::OpenShadowFile open_shadow_file)
+{
+    struct passwd* pwd = nullptr;
+    errno = 0;
+    pwd = getpwnam(username);
+    if (!pwd) {
+        if (errno == 0)
+            return String("No such user");
+
+        return String(strerror(errno));
+    }
+    return from_passwd(*pwd, open_passwd_file, open_shadow_file);
+}
+
+Result<Account, String> Account::from_uid(uid_t uid, Core::Account::OpenPasswdFile open_passwd_file, Core::Account::OpenShadowFile open_shadow_file)
+{
+    struct passwd* pwd = nullptr;
+    errno = 0;
+    pwd = getpwuid(uid);
+    if (!pwd) {
+        if (errno == 0)
+            return String("No such user");
+
+        return String(strerror(errno));
+    }
+    return from_passwd(*pwd, open_passwd_file, open_shadow_file);
+}
+
+bool Account::authenticate(const char* password) const
+{
+    // An empty passwd field indicates that no password is required to log in.
+    if (m_password_hash.is_empty())
+        return true;
+
+    // FIXME: Use crypt_r if it can be built in lagom.
+    char* hash = crypt(password, m_password_hash.characters());
+    return hash != nullptr && strcmp(hash, m_password_hash.characters()) == 0;
+}
+
+bool Account::login() const
+{
+    if (setgroups(m_extra_gids.size(), m_extra_gids.data()) < 0)
+        return false;
+
+    if (setgid(m_gid) < 0)
+        return false;
+
+    if (setuid(m_uid) < 0)
+        return false;
+
+    return true;
+}
+
+void Account::set_password(const char* password)
+{
+    m_password_hash = crypt(password, get_salt().characters());
+}
+
+void Account::set_password_enabled(bool enabled)
+{
+    if (enabled && m_password_hash != "" && m_password_hash[0] == '!') {
+        m_password_hash = m_password_hash.substring(1, m_password_hash.length() - 1);
+    } else if (!enabled && (m_password_hash == "" || m_password_hash[0] != '!')) {
+        StringBuilder builder;
+        builder.append('!');
+        builder.append(m_password_hash);
+        m_password_hash = builder.build();
+    }
+}
+
+void Account::delete_password()
+{
+    m_password_hash = "";
+}
+
+Account::Account(const passwd& pwd, Vector<gid_t> extra_gids, RefPtr<Core::File> passwd_file, RefPtr<Core::File> shadow_file)
+    : m_passwd_file(move(passwd_file))
+    , m_shadow_file(move(shadow_file))
+    , m_username(pwd.pw_name)
+    , m_uid(pwd.pw_uid)
+    , m_gid(pwd.pw_gid)
+    , m_gecos(pwd.pw_gecos)
+    , m_home_directory(pwd.pw_dir)
+    , m_shell(pwd.pw_shell)
+    , m_extra_gids(extra_gids)
+{
+    if (m_shadow_file) {
+        load_shadow_file();
+    }
+}
+
+String Account::generate_passwd_file() const
+{
+    StringBuilder builder;
+
+    setpwent();
+
+    struct passwd* p;
+    errno = 0;
+    while ((p = getpwent())) {
+        if (p->pw_uid == m_uid) {
+            builder.appendff("{}:!:{}:{}:{}:{}:{}\n",
+                m_username,
+                m_uid, m_gid,
+                m_gecos,
+                m_home_directory,
+                m_shell);
+
+        } else {
+            builder.appendff("{}:!:{}:{}:{}:{}:{}\n",
+                p->pw_name, p->pw_uid,
+                p->pw_gid, p->pw_gecos, p->pw_dir,
+                p->pw_shell);
+        }
+    }
+    endpwent();
+
+    if (errno) {
+        dbgln("errno was non-zero after generating new passwd file.");
+        return {};
+    }
+
+    return builder.to_string();
+}
+
+void Account::load_shadow_file()
+{
+    ASSERT(m_shadow_file);
+    ASSERT(m_shadow_file->is_open());
+
+    if (!m_shadow_file->seek(0)) {
+        ASSERT_NOT_REACHED();
+    }
+
+    Vector<ShadowEntry> entries;
+
+    for (;;) {
+        auto line = m_shadow_file->read_line();
+        if (line.is_null())
+            break;
+        auto parts = line.split(':');
+        if (parts.size() != 2) {
+            dbgln("Malformed shadow entry, ignoring.");
+            continue;
+        }
+        const auto& username = parts[0];
+        const auto& password_hash = parts[1];
+        entries.append({ username, password_hash });
+
+        if (username == m_username) {
+            m_password_hash = password_hash;
+        }
+    }
+
+    m_shadow_entries = move(entries);
+}
+
+String Account::generate_shadow_file() const
+{
+    StringBuilder builder;
+    bool updated_entry_in_place = false;
+    for (auto& entry : m_shadow_entries) {
+        if (entry.username == m_username) {
+            updated_entry_in_place = true;
+            builder.appendff("{}:{}\n", m_username, m_password_hash);
+        } else {
+            builder.appendff("{}:{}\n", entry.username, entry.password_hash);
+        }
+    }
+    if (!updated_entry_in_place)
+        builder.appendff("{}:{}\n", m_username, m_password_hash);
+    return builder.to_string();
+}
+
+bool Account::sync()
+{
+    ASSERT(m_passwd_file);
+    ASSERT(m_passwd_file->mode() == Core::File::OpenMode::ReadWrite);
+    ASSERT(m_shadow_file);
+    ASSERT(m_shadow_file->mode() == Core::File::OpenMode::ReadWrite);
+
+    // FIXME: Maybe reorganize this to create temporary files and finish it completely before renaming them to /etc/{passwd,shadow}
+    //        If truncation succeeds but write fails, we'll have an empty file :(
+
+    auto new_passwd_file = generate_passwd_file();
+    auto new_shadow_file = generate_shadow_file();
+
+    if (new_passwd_file.is_null() || new_shadow_file.is_null()) {
+        ASSERT_NOT_REACHED();
+    }
+
+    if (!m_passwd_file->seek(0) || !m_shadow_file->seek(0)) {
+        ASSERT_NOT_REACHED();
+    }
+
+    if (!m_passwd_file->truncate(0)) {
+        dbgln("Truncating passwd file failed.");
+        return false;
+    }
+
+    if (!m_passwd_file->write(new_passwd_file)) {
+        // FIXME: Improve Core::File::write() error reporting.
+        dbgln("Writing to passwd file failed.");
+        return false;
+    }
+
+    if (!m_shadow_file->truncate(0)) {
+        dbgln("Truncating shadow file failed.");
+        return false;
+    }
+
+    if (!m_shadow_file->write(new_shadow_file)) {
+        // FIXME: Improve Core::File::write() error reporting.
+        dbgln("Writing to shadow file failed.");
+        return false;
+    }
+
+    return true;
+    // FIXME: Sync extra groups.
+}
+
+}

Userland/Libraries/LibCore/Account.h

@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2020, Peter Elliott <pelliott@ualberta.ca>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Result.h>
+#include <AK/String.h>
+#include <AK/Types.h>
+#include <AK/Vector.h>
+#include <LibCore/File.h>
+#include <pwd.h>
+#include <sys/types.h>
+
+namespace Core {
+
+class Account {
+public:
+    enum class OpenPasswdFile {
+        No,
+        ReadOnly,
+        ReadWrite,
+    };
+
+    enum class OpenShadowFile {
+        No,
+        ReadOnly,
+        ReadWrite,
+    };
+
+    static Result<Account, String> from_name(const char* username, OpenPasswdFile = OpenPasswdFile::No, OpenShadowFile = OpenShadowFile::No);
+    static Result<Account, String> from_uid(uid_t uid, OpenPasswdFile = OpenPasswdFile::No, OpenShadowFile = OpenShadowFile::No);
+
+    bool authenticate(const char* password) const;
+    bool login() const;
+
+    String username() const { return m_username; }
+    String password_hash() const { return m_password_hash; }
+
+    // Setters only affect in-memory copy of password.
+    // You must call sync to apply changes.
+    void set_password(const char* password);
+    void set_password_enabled(bool enabled);
+    void delete_password();
+    bool has_password() const { return !m_password_hash.is_empty(); }
+
+    uid_t uid() const { return m_uid; }
+    gid_t gid() const { return m_gid; }
+    const String& gecos() const { return m_gecos; }
+    const String& home_directory() const { return m_home_directory; }
+    const String& shell() const { return m_shell; }
+    const Vector<gid_t>& extra_gids() const { return m_extra_gids; }
+
+    bool sync();
+
+private:
+    static Result<Account, String> from_passwd(const passwd&, OpenPasswdFile, OpenShadowFile);
+
+    Account(const passwd& pwd, Vector<gid_t> extra_gids, RefPtr<Core::File> passwd_file, RefPtr<Core::File> shadow_file);
+    void load_shadow_file();
+
+    String generate_passwd_file() const;
+    String generate_shadow_file() const;
+
+    RefPtr<Core::File> m_passwd_file;
+    RefPtr<Core::File> m_shadow_file;
+
+    String m_username;
+
+    // Contents of passwd field in passwd entry.
+    // Can be empty, "x", or contain a leading '!'
+    String m_password_hash;
+    uid_t m_uid { 0 };
+    gid_t m_gid { 0 };
+    String m_gecos;
+    String m_home_directory;
+    String m_shell;
+    Vector<gid_t> m_extra_gids;
+
+    struct ShadowEntry {
+        String username;
+        String password_hash;
+    };
+    Vector<ShadowEntry> m_shadow_entries;
+};
+
+}

Userland/Libraries/LibCore/ArgsParser.cpp

@@ -0,0 +1,392 @@
+/*
+ * Copyright (c) 2020, Sergey Bugaev <bugaevc@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Format.h>
+#include <AK/StringBuilder.h>
+#include <LibCore/ArgsParser.h>
+#include <getopt.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+
+static constexpr bool isnan(double __x) { return __builtin_isnan(__x); }
+
+static Optional<double> convert_to_double(const char* s)
+{
+    char* p;
+    double v = strtod(s, &p);
+    if (isnan(v) || p == s)
+        return {};
+    return v;
+}
+
+namespace Core {
+
+ArgsParser::ArgsParser()
+{
+    add_option(m_show_help, "Display this message", "help", 0);
+}
+
+bool ArgsParser::parse(int argc, char** argv, bool exit_on_failure)
+{
+    auto print_usage_and_exit = [this, argv, exit_on_failure] {
+        print_usage(stderr, argv[0]);
+        if (exit_on_failure)
+            exit(1);
+    };
+
+    Vector<option> long_options;
+    StringBuilder short_options_builder;
+
+    int index_of_found_long_option = -1;
+
+    // Tell getopt() to reset its internal state, and start scanning from optind = 1.
+    // We could also set optreset = 1, but the host platform may not support that.
+    optind = 0;
+
+    for (size_t i = 0; i < m_options.size(); i++) {
+        auto& opt = m_options[i];
+        if (opt.long_name) {
+            option long_opt {
+                opt.long_name,
+                opt.requires_argument ? required_argument : no_argument,
+                &index_of_found_long_option,
+                static_cast<int>(i)
+            };
+            long_options.append(long_opt);
+        }
+        if (opt.short_name) {
+            short_options_builder.append(opt.short_name);
+            if (opt.requires_argument)
+                short_options_builder.append(':');
+        }
+    }
+    long_options.append({ 0, 0, 0, 0 });
+
+    String short_options = short_options_builder.build();
+
+    while (true) {
+        int c = getopt_long(argc, argv, short_options.characters(), long_options.data(), nullptr);
+        if (c == -1) {
+            // We have reached the end.
+            break;
+        } else if (c == '?') {
+            // There was an error, and getopt() has already
+            // printed its error message.
+            print_usage_and_exit();
+            return false;
+        }
+
+        // Let's see what option we just found.
+        Option* found_option = nullptr;
+        if (c == 0) {
+            // It was a long option.
+            ASSERT(index_of_found_long_option >= 0);
+            found_option = &m_options[index_of_found_long_option];
+            index_of_found_long_option = -1;
+        } else {
+            // It was a short option, look it up.
+            auto it = m_options.find_if([c](auto& opt) { return c == opt.short_name; });
+            ASSERT(!it.is_end());
+            found_option = &*it;
+        }
+        ASSERT(found_option);
+
+        const char* arg = found_option->requires_argument ? optarg : nullptr;
+        if (!found_option->accept_value(arg)) {
+            warnln("\033[31mInvalid value for option \033[1m{}\033[22m, dude\033[0m", found_option->name_for_display());
+            print_usage_and_exit();
+            return false;
+        }
+    }
+
+    // We're done processing options, now let's parse positional arguments.
+
+    int values_left = argc - optind;
+    int num_values_for_arg[m_positional_args.size()];
+    int total_values_required = 0;
+    for (size_t i = 0; i < m_positional_args.size(); i++) {
+        auto& arg = m_positional_args[i];
+        num_values_for_arg[i] = arg.min_values;
+        total_values_required += arg.min_values;
+    }
+
+    if (total_values_required > values_left) {
+        print_usage_and_exit();
+        return false;
+    }
+    int extra_values_to_distribute = values_left - total_values_required;
+
+    for (size_t i = 0; i < m_positional_args.size(); i++) {
+        auto& arg = m_positional_args[i];
+        int extra_values_to_this_arg = min(arg.max_values - arg.min_values, extra_values_to_distribute);
+        num_values_for_arg[i] += extra_values_to_this_arg;
+        extra_values_to_distribute -= extra_values_to_this_arg;
+        if (extra_values_to_distribute == 0)
+            break;
+    }
+
+    if (extra_values_to_distribute > 0) {
+        // We still have too many values :(
+        print_usage_and_exit();
+        return false;
+    }
+
+    for (size_t i = 0; i < m_positional_args.size(); i++) {
+        auto& arg = m_positional_args[i];
+        for (int j = 0; j < num_values_for_arg[i]; j++) {
+            const char* value = argv[optind++];
+            if (!arg.accept_value(value)) {
+                warnln("Invalid value for argument {}", arg.name);
+                print_usage_and_exit();
+                return false;
+            }
+        }
+    }
+
+    // We're done parsing! :)
+    // Now let's show help if requested.
+    if (m_show_help) {
+        print_usage(stdout, argv[0]);
+        if (exit_on_failure)
+            exit(0);
+        return false;
+    }
+
+    return true;
+}
+
+void ArgsParser::print_usage(FILE* file, const char* argv0)
+{
+    out(file, "Usage:\n\t\033[1m{}\033[0m", argv0);
+
+    for (auto& opt : m_options) {
+        if (opt.long_name && !strcmp(opt.long_name, "help"))
+            continue;
+        if (opt.requires_argument)
+            out(file, " [{} {}]", opt.name_for_display(), opt.value_name);
+        else
+            out(file, " [{}]", opt.name_for_display());
+    }
+    for (auto& arg : m_positional_args) {
+        bool required = arg.min_values > 0;
+        bool repeated = arg.max_values > 1;
+
+        if (required && repeated)
+            out(file, " <{}...>", arg.name);
+        else if (required && !repeated)
+            out(file, " <{}>", arg.name);
+        else if (!required && repeated)
+            out(file, " [{}...]", arg.name);
+        else if (!required && !repeated)
+            out(file, " [{}]", arg.name);
+    }
+    outln(file);
+
+    if (m_general_help != nullptr && m_general_help[0] != '\0') {
+        outln(file, "\nDescription:");
+        outln(file, m_general_help);
+    }
+
+    if (!m_options.is_empty())
+        outln(file, "\nOptions:");
+    for (auto& opt : m_options) {
+        auto print_argument = [&]() {
+            if (opt.value_name) {
+                if (opt.requires_argument)
+                    out(file, " {}", opt.value_name);
+                else
+                    out(file, " [{}]", opt.value_name);
+            }
+        };
+        out(file, "\t");
+        if (opt.short_name) {
+            out(file, "\033[1m-{}\033[0m", opt.short_name);
+            print_argument();
+        }
+        if (opt.short_name && opt.long_name)
+            out(file, ", ");
+        if (opt.long_name) {
+            out(file, "\033[1m--{}\033[0m", opt.long_name);
+            print_argument();
+        }
+
+        if (opt.help_string)
+            out(file, "\t{}", opt.help_string);
+        outln(file);
+    }
+
+    if (!m_positional_args.is_empty())
+        outln(file, "\nArguments:");
+
+    for (auto& arg : m_positional_args) {
+        out(file, "\t\033[1m{}\033[0m", arg.name);
+        if (arg.help_string)
+            out(file, "\t{}", arg.help_string);
+        outln(file);
+    }
+}
+
+void ArgsParser::add_option(Option&& option)
+{
+    m_options.append(move(option));
+}
+
+void ArgsParser::add_option(bool& value, const char* help_string, const char* long_name, char short_name)
+{
+    Option option {
+        false,
+        help_string,
+        long_name,
+        short_name,
+        nullptr,
+        [&value](const char* s) {
+            ASSERT(s == nullptr);
+            value = true;
+            return true;
+        }
+    };
+    add_option(move(option));
+}
+
+void ArgsParser::add_option(const char*& value, const char* help_string, const char* long_name, char short_name, const char* value_name)
+{
+    Option option {
+        true,
+        help_string,
+        long_name,
+        short_name,
+        value_name,
+        [&value](const char* s) {
+            value = s;
+            return true;
+        }
+    };
+    add_option(move(option));
+}
+
+void ArgsParser::add_option(int& value, const char* help_string, const char* long_name, char short_name, const char* value_name)
+{
+    Option option {
+        true,
+        help_string,
+        long_name,
+        short_name,
+        value_name,
+        [&value](const char* s) {
+            auto opt = StringView(s).to_int();
+            value = opt.value_or(0);
+            return opt.has_value();
+        }
+    };
+    add_option(move(option));
+}
+
+void ArgsParser::add_option(double& value, const char* help_string, const char* long_name, char short_name, const char* value_name)
+{
+    Option option {
+        true,
+        help_string,
+        long_name,
+        short_name,
+        value_name,
+        [&value](const char* s) {
+            auto opt = convert_to_double(s);
+            value = opt.value_or(0.0);
+            return opt.has_value();
+        }
+    };
+    add_option(move(option));
+}
+
+void ArgsParser::add_positional_argument(Arg&& arg)
+{
+    m_positional_args.append(move(arg));
+}
+
+void ArgsParser::add_positional_argument(const char*& value, const char* help_string, const char* name, Required required)
+{
+    Arg arg {
+        help_string,
+        name,
+        required == Required::Yes ? 1 : 0,
+        1,
+        [&value](const char* s) {
+            value = s;
+            return true;
+        }
+    };
+    add_positional_argument(move(arg));
+}
+
+void ArgsParser::add_positional_argument(int& value, const char* help_string, const char* name, Required required)
+{
+    Arg arg {
+        help_string,
+        name,
+        required == Required::Yes ? 1 : 0,
+        1,
+        [&value](const char* s) {
+            auto opt = StringView(s).to_int();
+            value = opt.value_or(0);
+            return opt.has_value();
+        }
+    };
+    add_positional_argument(move(arg));
+}
+
+void ArgsParser::add_positional_argument(double& value, const char* help_string, const char* name, Required required)
+{
+    Arg arg {
+        help_string,
+        name,
+        required == Required::Yes ? 1 : 0,
+        1,
+        [&value](const char* s) {
+            auto opt = convert_to_double(s);
+            value = opt.value_or(0.0);
+            return opt.has_value();
+        }
+    };
+    add_positional_argument(move(arg));
+}
+
+void ArgsParser::add_positional_argument(Vector<const char*>& values, const char* help_string, const char* name, Required required)
+{
+    Arg arg {
+        help_string,
+        name,
+        required == Required::Yes ? 1 : 0,
+        INT_MAX,
+        [&values](const char* s) {
+            values.append(s);
+            return true;
+        }
+    };
+    add_positional_argument(move(arg));
+}
+
+}

Userland/Libraries/LibCore/ArgsParser.h

@@ -0,0 +1,94 @@
+/*
+ * Copyright (c) 2020, Sergey Bugaev <bugaevc@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/String.h>
+#include <AK/Vector.h>
+#include <stdio.h>
+
+namespace Core {
+
+class ArgsParser {
+public:
+    ArgsParser();
+
+    enum class Required {
+        Yes,
+        No
+    };
+
+    struct Option {
+        bool requires_argument { true };
+        const char* help_string { nullptr };
+        const char* long_name { nullptr };
+        char short_name { 0 };
+        const char* value_name { nullptr };
+        Function<bool(const char*)> accept_value;
+
+        String name_for_display() const
+        {
+            if (long_name)
+                return String::format("--%s", long_name);
+            return String::format("-%c", short_name);
+        }
+    };
+
+    struct Arg {
+        const char* help_string { nullptr };
+        const char* name { nullptr };
+        int min_values { 0 };
+        int max_values { 1 };
+        Function<bool(const char*)> accept_value;
+    };
+
+    bool parse(int argc, char** argv, bool exit_on_failure = true);
+    // *Without* trailing newline!
+    void set_general_help(const char* help_string) { m_general_help = help_string; };
+    void print_usage(FILE*, const char* argv0);
+
+    void add_option(Option&&);
+    void add_option(bool& value, const char* help_string, const char* long_name, char short_name);
+    void add_option(const char*& value, const char* help_string, const char* long_name, char short_name, const char* value_name);
+    void add_option(int& value, const char* help_string, const char* long_name, char short_name, const char* value_name);
+    void add_option(double& value, const char* help_string, const char* long_name, char short_name, const char* value_name);
+
+    void add_positional_argument(Arg&&);
+    void add_positional_argument(const char*& value, const char* help_string, const char* name, Required required = Required::Yes);
+    void add_positional_argument(int& value, const char* help_string, const char* name, Required required = Required::Yes);
+    void add_positional_argument(double& value, const char* help_string, const char* name, Required required = Required::Yes);
+    void add_positional_argument(Vector<const char*>& value, const char* help_string, const char* name, Required required = Required::Yes);
+
+private:
+    Vector<Option> m_options;
+    Vector<Arg> m_positional_args;
+
+    bool m_show_help { false };
+    const char* m_general_help { nullptr };
+};
+
+}

Userland/Libraries/LibCore/CMakeLists.txt

@@ -0,0 +1,37 @@
+set(SOURCES
+    Account.cpp
+    ArgsParser.cpp
+    ConfigFile.cpp
+    Command.cpp
+    DateTime.cpp
+    DirectoryWatcher.cpp
+    DirIterator.cpp
+    ElapsedTimer.cpp
+    Event.cpp
+    EventLoop.cpp
+    File.cpp
+    GetPassword.cpp
+    Gzip.cpp
+    IODevice.cpp
+    LocalServer.cpp
+    LocalSocket.cpp
+    MimeData.cpp
+    NetworkJob.cpp
+    NetworkResponse.cpp
+    Notifier.cpp
+    Object.cpp
+    ProcessStatisticsReader.cpp
+    Property.cpp
+    puff.cpp
+    SocketAddress.cpp
+    Socket.cpp
+    StandardPaths.cpp
+    TCPServer.cpp
+    TCPSocket.cpp
+    Timer.cpp
+    UDPServer.cpp
+    UDPSocket.cpp
+)
+
+serenity_lib(LibCore core)
+target_link_libraries(LibCore LibC LibCrypt)

Userland/Libraries/LibCore/Command.cpp

@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Command.h"
+#include <AK/ByteBuffer.h>
+#include <AK/LogStream.h>
+#include <AK/ScopeGuard.h>
+#include <LibCore/File.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+// #define DBG_FAILED_COMMANDS
+
+namespace Core {
+
+// Only supported in serenity mode because we use `posix_spawn_file_actions_addchdir`
+#ifdef __serenity__
+
+String command(const String& command_string, Optional<LexicalPath> chdir)
+{
+    auto parts = command_string.split(' ');
+    if (parts.is_empty())
+        return {};
+    auto program = parts[0];
+    parts.remove(0);
+    return command(program, parts, chdir);
+}
+
+String command(const String& program, const Vector<String>& arguments, Optional<LexicalPath> chdir)
+{
+    int stdout_pipe[2] = {};
+    int stderr_pipe[2] = {};
+    if (pipe2(stdout_pipe, O_CLOEXEC)) {
+        perror("pipe2");
+        ASSERT_NOT_REACHED();
+    }
+    if (pipe2(stderr_pipe, O_CLOEXEC)) {
+        perror("pipe2");
+        ASSERT_NOT_REACHED();
+    }
+
+    auto close_pipes = ScopeGuard([stderr_pipe, stdout_pipe] {
+        // The write-ends of these pipes are closed manually
+        close(stdout_pipe[0]);
+        close(stderr_pipe[0]);
+    });
+
+    Vector<const char*> parts = { program.characters() };
+    for (const auto& part : arguments) {
+        parts.append(part.characters());
+    }
+    parts.append(nullptr);
+
+    const char** argv = parts.data();
+
+    posix_spawn_file_actions_t action;
+    posix_spawn_file_actions_init(&action);
+    if (chdir.has_value()) {
+        posix_spawn_file_actions_addchdir(&action, chdir.value().string().characters());
+    }
+    posix_spawn_file_actions_adddup2(&action, stdout_pipe[1], STDOUT_FILENO);
+    posix_spawn_file_actions_adddup2(&action, stderr_pipe[1], STDERR_FILENO);
+
+    pid_t pid;
+    if ((errno = posix_spawnp(&pid, program.characters(), &action, nullptr, const_cast<char**>(argv), environ))) {
+        perror("posix_spawn");
+        ASSERT_NOT_REACHED();
+    }
+    int wstatus;
+    waitpid(pid, &wstatus, 0);
+    posix_spawn_file_actions_destroy(&action);
+
+    // close the write-ends so reading wouldn't block
+    close(stdout_pipe[1]);
+    close(stderr_pipe[1]);
+
+    auto read_all_from_pipe = [](int pipe[2]) {
+        auto result_file = Core::File::construct();
+        if (!result_file->open(pipe[0], Core::IODevice::ReadOnly, Core::File::ShouldCloseFileDescriptor::Yes)) {
+            perror("open");
+            ASSERT_NOT_REACHED();
+        }
+        return String::copy(result_file->read_all());
+    };
+
+    if (WEXITSTATUS(wstatus) != 0) {
+#    ifdef DBG_FAILED_COMMANDS
+        dbgln("command failed. stderr: {}", read_all_from_pipe(stderr_pipe));
+#    endif
+        return {};
+    }
+
+    auto result = read_all_from_pipe(stdout_pipe);
+    if (result.is_null())
+        return "";
+    return result;
+}
+
+#endif
+
+}

Userland/Libraries/LibCore/Command.h

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/LexicalPath.h>
+#include <AK/Optional.h>
+#include <AK/String.h>
+#include <spawn.h>
+
+namespace Core {
+
+// If the executed command fails, the returned String will be in the null state.
+String command(const String& program, const Vector<String>& arguments, Optional<LexicalPath> chdir);
+String command(const String& command_string, Optional<LexicalPath> chdir);
+
+}

Userland/Libraries/LibCore/ConfigFile.cpp

@@ -0,0 +1,242 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/ByteBuffer.h>
+#include <AK/StringBuilder.h>
+#include <LibCore/ConfigFile.h>
+#include <LibCore/File.h>
+#include <LibCore/StandardPaths.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <unistd.h>
+
+namespace Core {
+
+NonnullRefPtr<ConfigFile> ConfigFile::get_for_lib(const String& lib_name)
+{
+    String directory = StandardPaths::config_directory();
+    auto path = String::formatted("{}/lib/{}.ini", directory, lib_name);
+
+    return adopt(*new ConfigFile(path));
+}
+
+NonnullRefPtr<ConfigFile> ConfigFile::get_for_app(const String& app_name)
+{
+    String directory = StandardPaths::config_directory();
+    auto path = String::formatted("{}/{}.ini", directory, app_name);
+    return adopt(*new ConfigFile(path));
+}
+
+NonnullRefPtr<ConfigFile> ConfigFile::get_for_system(const String& app_name)
+{
+    auto path = String::formatted("/etc/{}.ini", app_name);
+    return adopt(*new ConfigFile(path));
+}
+
+NonnullRefPtr<ConfigFile> ConfigFile::open(const String& path)
+{
+    return adopt(*new ConfigFile(path));
+}
+
+ConfigFile::ConfigFile(const String& file_name)
+    : m_file_name(file_name)
+{
+    reparse();
+}
+
+ConfigFile::~ConfigFile()
+{
+    sync();
+}
+
+void ConfigFile::reparse()
+{
+    m_groups.clear();
+
+    auto file = File::construct(m_file_name);
+    if (!file->open(IODevice::OpenMode::ReadOnly))
+        return;
+
+    HashMap<String, String>* current_group = nullptr;
+
+    while (file->can_read_line()) {
+        auto line = file->read_line();
+        auto* cp = line.characters();
+
+        while (*cp && (*cp == ' ' || *cp == '\t' || *cp == '\n'))
+            ++cp;
+
+        switch (*cp) {
+        case '\0': // EOL...
+        case '#':  // Comment, skip entire line.
+        case ';':  // -||-
+            continue;
+        case '[': { // Start of new group.
+            StringBuilder builder;
+            ++cp; // Skip the '['
+            while (*cp && (*cp != ']'))
+                builder.append(*(cp++));
+            current_group = &m_groups.ensure(builder.to_string());
+            break;
+        }
+        default: { // Start of key{
+            StringBuilder key_builder;
+            StringBuilder value_builder;
+            while (*cp && (*cp != '='))
+                key_builder.append(*(cp++));
+            ++cp; // Skip the '='
+            while (*cp && (*cp != '\n'))
+                value_builder.append(*(cp++));
+            if (!current_group) {
+                // We're not in a group yet, create one with the name ""...
+                current_group = &m_groups.ensure("");
+            }
+            current_group->set(key_builder.to_string(), value_builder.to_string());
+        }
+        }
+    }
+}
+
+String ConfigFile::read_entry(const String& group, const String& key, const String& default_value) const
+{
+    if (!has_key(group, key)) {
+        return default_value;
+    }
+    auto it = m_groups.find(group);
+    auto jt = it->value.find(key);
+    return jt->value;
+}
+
+int ConfigFile::read_num_entry(const String& group, const String& key, int default_value) const
+{
+    if (!has_key(group, key)) {
+        return default_value;
+    }
+
+    return read_entry(group, key).to_int().value_or(default_value);
+}
+
+bool ConfigFile::read_bool_entry(const String& group, const String& key, bool default_value) const
+{
+    auto value = read_entry(group, key, default_value ? "1" : "0");
+    if (value == "1" || value.to_lowercase() == "true")
+        return 1;
+    return 0;
+}
+
+void ConfigFile::write_entry(const String& group, const String& key, const String& value)
+{
+    m_groups.ensure(group).ensure(key) = value;
+    m_dirty = true;
+}
+
+void ConfigFile::write_num_entry(const String& group, const String& key, int value)
+{
+    write_entry(group, key, String::number(value));
+}
+void ConfigFile::write_bool_entry(const String& group, const String& key, bool value)
+{
+    write_entry(group, key, value ? "1" : "0");
+}
+void ConfigFile::write_color_entry(const String& group, const String& key, Color value)
+{
+    write_entry(group, key, String::formatted("{},{},{},{}", value.red(), value.green(), value.blue(), value.alpha()));
+}
+
+bool ConfigFile::sync()
+{
+    if (!m_dirty)
+        return true;
+
+    FILE* fp = fopen(m_file_name.characters(), "wb");
+    if (!fp)
+        return false;
+
+    for (auto& it : m_groups) {
+        outln(fp, "[{}]", it.key);
+        for (auto& jt : it.value)
+            outln(fp, "{}={}", jt.key, jt.value);
+        outln(fp);
+    }
+
+    fclose(fp);
+
+    m_dirty = false;
+    return true;
+}
+
+void ConfigFile::dump() const
+{
+    for (auto& it : m_groups) {
+        outln("[{}]", it.key);
+        for (auto& jt : it.value)
+            outln("{}={}", jt.key, jt.value);
+        outln();
+    }
+}
+
+Vector<String> ConfigFile::groups() const
+{
+    return m_groups.keys();
+}
+
+Vector<String> ConfigFile::keys(const String& group) const
+{
+    auto it = m_groups.find(group);
+    if (it == m_groups.end())
+        return {};
+    return it->value.keys();
+}
+
+bool ConfigFile::has_key(const String& group, const String& key) const
+{
+    auto it = m_groups.find(group);
+    if (it == m_groups.end())
+        return {};
+    return it->value.contains(key);
+}
+
+bool ConfigFile::has_group(const String& group) const
+{
+    return m_groups.contains(group);
+}
+
+void ConfigFile::remove_group(const String& group)
+{
+    m_groups.remove(group);
+    m_dirty = true;
+}
+
+void ConfigFile::remove_entry(const String& group, const String& key)
+{
+    auto it = m_groups.find(group);
+    if (it == m_groups.end())
+        return;
+    it->value.remove(key);
+    m_dirty = true;
+}
+
+}

Userland/Libraries/LibCore/ConfigFile.h

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/HashMap.h>
+#include <AK/RefCounted.h>
+#include <AK/RefPtr.h>
+#include <AK/String.h>
+#include <AK/Vector.h>
+#include <LibGfx/Color.h>
+
+namespace Core {
+
+class ConfigFile : public RefCounted<ConfigFile> {
+public:
+    static NonnullRefPtr<ConfigFile> get_for_lib(const String& lib_name);
+    static NonnullRefPtr<ConfigFile> get_for_app(const String& app_name);
+    static NonnullRefPtr<ConfigFile> get_for_system(const String& app_name);
+    static NonnullRefPtr<ConfigFile> open(const String& path);
+    ~ConfigFile();
+
+    bool has_group(const String&) const;
+    bool has_key(const String& group, const String& key) const;
+
+    Vector<String> groups() const;
+    Vector<String> keys(const String& group) const;
+
+    String read_entry(const String& group, const String& key, const String& default_value = String()) const;
+    int read_num_entry(const String& group, const String& key, int default_value = 0) const;
+    bool read_bool_entry(const String& group, const String& key, bool default_value = false) const;
+
+    void write_entry(const String& group, const String& key, const String& value);
+    void write_num_entry(const String& group, const String& key, int value);
+    void write_bool_entry(const String& group, const String& key, bool value);
+    void write_color_entry(const String& group, const String& key, Color value);
+
+    void dump() const;
+
+    bool is_dirty() const { return m_dirty; }
+
+    bool sync();
+
+    void remove_group(const String& group);
+    void remove_entry(const String& group, const String& key);
+
+    String file_name() const { return m_file_name; }
+
+private:
+    explicit ConfigFile(const String& file_name);
+
+    void reparse();
+
+    String m_file_name;
+    HashMap<String, HashMap<String, String>> m_groups;
+    bool m_dirty { false };
+};
+
+}

Userland/Libraries/LibCore/DateTime.cpp

@@ -0,0 +1,263 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/StringBuilder.h>
+#include <AK/Time.h>
+#include <LibCore/DateTime.h>
+#include <sys/time.h>
+#include <time.h>
+
+namespace Core {
+
+DateTime DateTime::now()
+{
+    return from_timestamp(time(nullptr));
+}
+
+DateTime DateTime::create(unsigned year, unsigned month, unsigned day, unsigned hour, unsigned minute, unsigned second)
+{
+    DateTime dt;
+    dt.set_time(year, month, day, hour, minute, second);
+    return dt;
+}
+
+DateTime DateTime::from_timestamp(time_t timestamp)
+{
+    struct tm tm;
+    localtime_r(&timestamp, &tm);
+    DateTime dt;
+    dt.m_year = tm.tm_year + 1900;
+    dt.m_month = tm.tm_mon + 1;
+    dt.m_day = tm.tm_mday;
+    dt.m_hour = tm.tm_hour;
+    dt.m_minute = tm.tm_min;
+    dt.m_second = tm.tm_sec;
+    dt.m_timestamp = timestamp;
+    return dt;
+}
+
+unsigned DateTime::weekday() const
+{
+    return ::day_of_week(m_year, m_month, m_day);
+}
+
+unsigned DateTime::days_in_month() const
+{
+    return ::days_in_month(m_year, m_month);
+}
+
+unsigned DateTime::day_of_year() const
+{
+    return ::day_of_year(m_year, m_month, m_day);
+}
+
+bool DateTime::is_leap_year() const
+{
+    return ::is_leap_year(m_year);
+}
+
+void DateTime::set_time(unsigned year, unsigned month, unsigned day, unsigned hour, unsigned minute, unsigned second)
+{
+    struct tm tm = {};
+    tm.tm_sec = (int)second;
+    tm.tm_min = (int)minute;
+    tm.tm_hour = (int)hour;
+    tm.tm_mday = (int)day;
+    tm.tm_mon = (int)month - 1;
+    tm.tm_year = (int)year - 1900;
+    tm.tm_isdst = -1;
+    // mktime() doesn't read tm.tm_wday and tm.tm_yday, no need to fill them in.
+
+    m_timestamp = mktime(&tm);
+
+    // mktime() normalizes the components to the right ranges (Jan 32 -> Feb 1 etc), so read fields back out from tm.
+    m_year = tm.tm_year + 1900;
+    m_month = tm.tm_mon + 1;
+    m_day = tm.tm_mday;
+    m_hour = tm.tm_hour;
+    m_minute = tm.tm_min;
+    m_second = tm.tm_sec;
+}
+
+String DateTime::to_string(const String& format) const
+{
+
+    const char wday_short_names[7][4] = {
+        "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
+    };
+    const char wday_long_names[7][10] = {
+        "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"
+    };
+    const char mon_short_names[12][4] = {
+        "Jan", "Feb", "Mar", "Apr", "May", "Jun",
+        "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
+    };
+    const char mon_long_names[12][10] = {
+        "January", "February", "March", "April", "May", "June",
+        "July", "August", "September", "October", "November", "December"
+    };
+
+    struct tm tm;
+    localtime_r(&m_timestamp, &tm);
+    StringBuilder builder;
+    const int format_len = format.length();
+
+    for (int i = 0; i < format_len; ++i) {
+        if (format[i] != '%') {
+            builder.append(format[i]);
+        } else {
+            if (++i == format_len)
+                return String();
+
+            switch (format[i]) {
+            case 'a':
+                builder.append(wday_short_names[tm.tm_wday]);
+                break;
+            case 'A':
+                builder.append(wday_long_names[tm.tm_wday]);
+                break;
+            case 'b':
+                builder.append(mon_short_names[tm.tm_mon]);
+                break;
+            case 'B':
+                builder.append(mon_long_names[tm.tm_mon]);
+                break;
+            case 'C':
+                builder.appendf("%02d", (tm.tm_year + 1900) / 100);
+                break;
+            case 'd':
+                builder.appendf("%02d", tm.tm_mday);
+                break;
+            case 'D':
+                builder.appendf("%02d/%02d/%02d", tm.tm_mon + 1, tm.tm_mday, (tm.tm_year + 1900) % 100);
+                break;
+            case 'e':
+                builder.appendf("%2d", tm.tm_mday);
+                break;
+            case 'h':
+                builder.append(mon_short_names[tm.tm_mon]);
+                break;
+            case 'H':
+                builder.appendf("%02d", tm.tm_hour);
+                break;
+            case 'I':
+                builder.appendf("%02d", tm.tm_hour % 12);
+                break;
+            case 'j':
+                builder.appendf("%03d", tm.tm_yday + 1);
+                break;
+            case 'm':
+                builder.appendf("%02d", tm.tm_mon + 1);
+                break;
+            case 'M':
+                builder.appendf("%02d", tm.tm_min);
+                break;
+            case 'n':
+                builder.append('\n');
+                break;
+            case 'p':
+                builder.append(tm.tm_hour < 12 ? "a.m." : "p.m.");
+                break;
+            case 'r':
+                builder.appendf("%02d:%02d:%02d %s", tm.tm_hour % 12, tm.tm_min, tm.tm_sec, tm.tm_hour < 12 ? "a.m." : "p.m.");
+                break;
+            case 'R':
+                builder.appendf("%02d:%02d", tm.tm_hour, tm.tm_min);
+                break;
+            case 'S':
+                builder.appendf("%02d", tm.tm_sec);
+                break;
+            case 't':
+                builder.append('\t');
+                break;
+            case 'T':
+                builder.appendf("%02d:%02d:%02d", tm.tm_hour, tm.tm_min, tm.tm_sec);
+                break;
+            case 'u':
+                builder.appendf("%d", tm.tm_wday ? tm.tm_wday : 7);
+                break;
+            case 'U': {
+                const int wday_of_year_beginning = (tm.tm_wday + 6 * tm.tm_yday) % 7;
+                const int week_number = (tm.tm_yday + wday_of_year_beginning) / 7;
+                builder.appendf("%02d", week_number);
+                break;
+            }
+            case 'V': {
+                const int wday_of_year_beginning = (tm.tm_wday + 6 + 6 * tm.tm_yday) % 7;
+                int week_number = (tm.tm_yday + wday_of_year_beginning) / 7 + 1;
+                if (wday_of_year_beginning > 3) {
+                    if (tm.tm_yday >= 7 - wday_of_year_beginning)
+                        --week_number;
+                    else {
+                        const int days_of_last_year = days_in_year(tm.tm_year + 1900 - 1);
+                        const int wday_of_last_year_beginning = (wday_of_year_beginning + 6 * days_of_last_year) % 7;
+                        week_number = (days_of_last_year + wday_of_last_year_beginning) / 7 + 1;
+                        if (wday_of_last_year_beginning > 3)
+                            --week_number;
+                    }
+                }
+                builder.appendf("%02d", week_number);
+                break;
+            }
+            case 'w':
+                builder.appendf("%d", tm.tm_wday);
+                break;
+            case 'W': {
+                const int wday_of_year_beginning = (tm.tm_wday + 6 + 6 * tm.tm_yday) % 7;
+                const int week_number = (tm.tm_yday + wday_of_year_beginning) / 7;
+                builder.appendf("%02d", week_number);
+                break;
+            }
+            case 'y':
+                builder.appendf("%02d", (tm.tm_year + 1900) % 100);
+                break;
+            case 'Y':
+                builder.appendf("%d", tm.tm_year + 1900);
+                break;
+            case '%':
+                builder.append('%');
+                break;
+            default:
+                return String();
+            }
+        }
+    }
+
+    return builder.build();
+}
+
+bool DateTime::is_before(const String& other) const
+{
+    auto now_string = String::formatted("{:04}{:02}{:02}{:02}{:02}{:02}Z", year(), month(), weekday(), hour(), minute(), second());
+    return __builtin_strcasecmp(now_string.characters(), other.characters()) < 0;
+}
+
+const LogStream& operator<<(const LogStream& stream, const DateTime& value)
+{
+    return stream << value.to_string();
+}
+
+}

Userland/Libraries/LibCore/DateTime.h

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/String.h>
+#include <time.h>
+
+namespace Core {
+
+// Represents a time in local time.
+class DateTime {
+public:
+    time_t timestamp() const { return m_timestamp; }
+
+    unsigned year() const { return m_year; }
+    unsigned month() const { return m_month; }
+    unsigned day() const { return m_day; }
+
+    unsigned hour() const { return m_hour; }
+    unsigned minute() const { return m_minute; }
+    unsigned second() const { return m_second; }
+    unsigned weekday() const;
+    unsigned days_in_month() const;
+    unsigned day_of_year() const;
+    bool is_leap_year() const;
+
+    void set_time(unsigned year, unsigned month = 1, unsigned day = 0, unsigned hour = 0, unsigned minute = 0, unsigned second = 0);
+    String to_string(const String& format = "%Y-%m-%d %H:%M:%S") const;
+
+    static DateTime create(unsigned year, unsigned month = 1, unsigned day = 0, unsigned hour = 0, unsigned minute = 0, unsigned second = 0);
+    static DateTime now();
+    static DateTime from_timestamp(time_t);
+
+    // FIXME: This should be replaced with a proper comparison
+    //        operator when we get the equivalent of strptime
+    bool is_before(const String&) const;
+
+private:
+    time_t m_timestamp { 0 };
+    unsigned m_year { 0 };
+    unsigned m_month { 0 };
+    unsigned m_day { 0 };
+    unsigned m_hour { 0 };
+    unsigned m_minute { 0 };
+    unsigned m_second { 0 };
+};
+
+const LogStream& operator<<(const LogStream&, const DateTime&);
+
+}

Userland/Libraries/LibCore/DirIterator.cpp

@@ -0,0 +1,121 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Vector.h>
+#include <LibCore/DirIterator.h>
+#include <errno.h>
+
+namespace Core {
+
+DirIterator::DirIterator(const StringView& path, Flags flags)
+    : m_path(path)
+    , m_flags(flags)
+{
+    m_dir = opendir(path.to_string().characters());
+    if (!m_dir) {
+        m_error = errno;
+    }
+}
+
+DirIterator::~DirIterator()
+{
+    if (m_dir) {
+        closedir(m_dir);
+        m_dir = nullptr;
+    }
+}
+
+bool DirIterator::advance_next()
+{
+    if (!m_dir)
+        return false;
+
+    while (true) {
+        errno = 0;
+        auto* de = readdir(m_dir);
+        if (!de) {
+            m_error = errno;
+            m_next = String();
+            return false;
+        }
+
+        m_next = de->d_name;
+        if (m_next.is_null())
+            return false;
+
+        if (m_flags & Flags::SkipDots && m_next.starts_with('.'))
+            continue;
+
+        if (m_flags & Flags::SkipParentAndBaseDir && (m_next == "." || m_next == ".."))
+            continue;
+
+        return !m_next.is_empty();
+    }
+}
+
+bool DirIterator::has_next()
+{
+    if (!m_next.is_null())
+        return true;
+
+    return advance_next();
+}
+
+String DirIterator::next_path()
+{
+    if (m_next.is_null())
+        advance_next();
+
+    auto tmp = m_next;
+    m_next = String();
+    return tmp;
+}
+
+String DirIterator::next_full_path()
+{
+    return String::formatted("{}/{}", m_path, next_path());
+}
+
+String find_executable_in_path(String filename)
+{
+    if (filename.starts_with('/')) {
+        if (access(filename.characters(), X_OK) == 0)
+            return filename;
+
+        return {};
+    }
+
+    for (auto directory : String { getenv("PATH") }.split(':')) {
+        auto fullpath = String::formatted("{}/{}", directory, filename);
+
+        if (access(fullpath.characters(), X_OK) == 0)
+            return fullpath;
+    }
+
+    return {};
+}
+
+}

Userland/Libraries/LibCore/DirIterator.h

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/String.h>
+#include <dirent.h>
+#include <string.h>
+
+namespace Core {
+
+class DirIterator {
+public:
+    enum Flags {
+        NoFlags = 0x0,
+        SkipDots = 0x1,
+        SkipParentAndBaseDir = 0x2,
+    };
+
+    DirIterator(const StringView& path, Flags = Flags::NoFlags);
+    ~DirIterator();
+
+    bool has_error() const { return m_error != 0; }
+    int error() const { return m_error; }
+    const char* error_string() const { return strerror(m_error); }
+    bool has_next();
+    String next_path();
+    String next_full_path();
+
+private:
+    DIR* m_dir = nullptr;
+    int m_error = 0;
+    String m_next;
+    String m_path;
+    int m_flags;
+
+    bool advance_next();
+};
+
+String find_executable_in_path(String filename);
+
+}

Userland/Libraries/LibCore/DirectoryWatcher.cpp

@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "DirectoryWatcher.h"
+#include <AK/LexicalPath.h>
+#include <AK/Optional.h>
+#include <LibCore/DirIterator.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+
+namespace Core {
+
+// Only supported in serenity mode because we use `watch_file`
+#ifdef __serenity__
+
+DirectoryWatcher::DirectoryWatcher(const String& path)
+    : m_path(path)
+{
+    m_watcher_fd = watch_file(path.characters(), path.length());
+    ASSERT(m_watcher_fd != -1);
+}
+
+DirectoryWatcher::~DirectoryWatcher()
+{
+    close(m_watcher_fd);
+}
+
+Optional<DirectoryWatcher::Event> DirectoryWatcher::wait_for_event()
+{
+    InodeWatcherEvent event {};
+    int rc = read(m_watcher_fd, &event, sizeof(event));
+    if (rc <= 0)
+        return {};
+
+    Event result;
+    if (event.type == InodeWatcherEvent::Type::ChildAdded)
+        result.type = Event::Type::ChildAdded;
+    else if (event.type == InodeWatcherEvent::Type::ChildRemoved)
+        result.type = Event::Type::ChildRemoved;
+    else
+        return {};
+
+    auto child_path = get_child_with_inode_index(event.inode_index);
+    if (!LexicalPath(child_path).is_valid())
+        return {};
+
+    result.child_path = child_path;
+    return result;
+}
+
+String DirectoryWatcher::get_child_with_inode_index(unsigned child_inode_index) const
+{
+    DirIterator iterator(m_path, Core::DirIterator::SkipDots);
+    if (iterator.has_error()) {
+        return {};
+    }
+
+    while (iterator.has_next()) {
+        auto child_full_path = String::formatted("{}/{}", m_path, iterator.next_path());
+        struct stat st;
+
+        if (lstat(child_full_path.characters(), &st)) {
+            return {};
+        }
+
+        if (st.st_ino == child_inode_index) {
+            return child_full_path;
+        }
+    }
+    return {};
+}
+
+#endif
+
+}

Userland/Libraries/LibCore/DirectoryWatcher.h

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/Noncopyable.h>
+#include <AK/String.h>
+#include <Kernel/API/InodeWatcherEvent.h>
+
+namespace Core {
+
+class DirectoryWatcher {
+    AK_MAKE_NONCOPYABLE(DirectoryWatcher);
+
+public:
+    explicit DirectoryWatcher(const String& path);
+    ~DirectoryWatcher();
+
+    struct Event {
+        enum class Type {
+            ChildAdded,
+            ChildRemoved,
+        };
+        Type type;
+        String child_path;
+    };
+
+    Optional<Event> wait_for_event();
+
+private:
+    String get_child_with_inode_index(unsigned) const;
+
+    String m_path;
+    int m_watcher_fd { -1 };
+};
+
+}

Userland/Libraries/LibCore/ElapsedTimer.cpp

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Assertions.h>
+#include <AK/Time.h>
+#include <LibCore/ElapsedTimer.h>
+#include <sys/time.h>
+#include <time.h>
+
+namespace Core {
+
+void ElapsedTimer::start()
+{
+    m_valid = true;
+    timespec now_spec;
+    clock_gettime(m_precise ? CLOCK_MONOTONIC : CLOCK_MONOTONIC_COARSE, &now_spec);
+    m_origin_time.tv_sec = now_spec.tv_sec;
+    m_origin_time.tv_usec = now_spec.tv_nsec / 1000;
+}
+
+int ElapsedTimer::elapsed() const
+{
+    ASSERT(is_valid());
+    struct timeval now;
+    timespec now_spec;
+    clock_gettime(m_precise ? CLOCK_MONOTONIC : CLOCK_MONOTONIC_COARSE, &now_spec);
+    now.tv_sec = now_spec.tv_sec;
+    now.tv_usec = now_spec.tv_nsec / 1000;
+    struct timeval diff;
+    timeval_sub(now, m_origin_time, diff);
+    return diff.tv_sec * 1000 + diff.tv_usec / 1000;
+}
+
+}

Userland/Libraries/LibCore/ElapsedTimer.h

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <sys/time.h>
+
+namespace Core {
+
+class ElapsedTimer {
+public:
+    ElapsedTimer(bool precise = false)
+        : m_precise(precise)
+    {
+    }
+
+    bool is_valid() const { return m_valid; }
+    void start();
+    int elapsed() const;
+
+    const struct timeval& origin_time() const { return m_origin_time; }
+
+private:
+    bool m_precise { false };
+    bool m_valid { false };
+    struct timeval m_origin_time {
+        0, 0
+    };
+};
+
+}

Userland/Libraries/LibCore/Event.cpp

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/WeakPtr.h>
+#include <LibCore/Event.h>
+#include <LibCore/Object.h>
+
+namespace Core {
+
+ChildEvent::ChildEvent(Type type, Object& child, Object* insertion_before_child)
+    : Core::Event(type)
+    , m_child(child.make_weak_ptr())
+    , m_insertion_before_child(AK::try_make_weak_ptr(insertion_before_child))
+{
+}
+
+ChildEvent::~ChildEvent()
+{
+}
+
+Object* ChildEvent::child()
+{
+    if (auto ref = m_child.strong_ref())
+        return ref.ptr();
+    return nullptr;
+}
+
+const Object* ChildEvent::child() const
+{
+    if (auto ref = m_child.strong_ref())
+        return ref.ptr();
+    return nullptr;
+}
+
+Object* ChildEvent::insertion_before_child()
+{
+    if (auto ref = m_insertion_before_child.strong_ref())
+        return ref.ptr();
+    return nullptr;
+}
+
+const Object* ChildEvent::insertion_before_child() const
+{
+    if (auto ref = m_insertion_before_child.strong_ref())
+        return ref.ptr();
+    return nullptr;
+}
+
+}

Userland/Libraries/LibCore/Event.h

@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/String.h>
+#include <AK/Types.h>
+#include <AK/WeakPtr.h>
+#include <LibCore/Forward.h>
+
+namespace Core {
+
+class Event {
+public:
+    enum Type {
+        Invalid = 0,
+        Quit,
+        Timer,
+        NotifierRead,
+        NotifierWrite,
+        DeferredInvoke,
+        ChildAdded,
+        ChildRemoved,
+        Custom,
+    };
+
+    Event() { }
+    explicit Event(unsigned type)
+        : m_type(type)
+    {
+    }
+    virtual ~Event() { }
+
+    unsigned type() const { return m_type; }
+
+    bool is_accepted() const { return m_accepted; }
+    void accept() { m_accepted = true; }
+    void ignore() { m_accepted = false; }
+
+private:
+    unsigned m_type { Type::Invalid };
+    bool m_accepted { true };
+};
+
+class DeferredInvocationEvent : public Event {
+    friend class EventLoop;
+
+public:
+    DeferredInvocationEvent(Function<void(Object&)> invokee)
+        : Event(Event::Type::DeferredInvoke)
+        , m_invokee(move(invokee))
+    {
+    }
+
+private:
+    Function<void(Object&)> m_invokee;
+};
+
+class TimerEvent final : public Event {
+public:
+    explicit TimerEvent(int timer_id)
+        : Event(Event::Timer)
+        , m_timer_id(timer_id)
+    {
+    }
+    ~TimerEvent() { }
+
+    int timer_id() const { return m_timer_id; }
+
+private:
+    int m_timer_id;
+};
+
+class NotifierReadEvent final : public Event {
+public:
+    explicit NotifierReadEvent(int fd)
+        : Event(Event::NotifierRead)
+        , m_fd(fd)
+    {
+    }
+    ~NotifierReadEvent() { }
+
+    int fd() const { return m_fd; }
+
+private:
+    int m_fd;
+};
+
+class NotifierWriteEvent final : public Event {
+public:
+    explicit NotifierWriteEvent(int fd)
+        : Event(Event::NotifierWrite)
+        , m_fd(fd)
+    {
+    }
+    ~NotifierWriteEvent() { }
+
+    int fd() const { return m_fd; }
+
+private:
+    int m_fd;
+};
+
+class ChildEvent final : public Event {
+public:
+    ChildEvent(Type, Object& child, Object* insertion_before_child = nullptr);
+    ~ChildEvent();
+
+    Object* child();
+    const Object* child() const;
+
+    Object* insertion_before_child();
+    const Object* insertion_before_child() const;
+
+private:
+    WeakPtr<Object> m_child;
+    WeakPtr<Object> m_insertion_before_child;
+};
+
+class CustomEvent : public Event {
+public:
+    CustomEvent(int custom_type)
+        : Event(Event::Type::Custom)
+        , m_custom_type(custom_type)
+    {
+    }
+    ~CustomEvent() { }
+
+    int custom_type() const { return m_custom_type; }
+
+private:
+    int m_custom_type { 0 };
+};
+
+}

Userland/Libraries/LibCore/EventLoop.cpp

@@ -0,0 +1,835 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Badge.h>
+#include <AK/ByteBuffer.h>
+#include <AK/IDAllocator.h>
+#include <AK/JsonObject.h>
+#include <AK/JsonValue.h>
+#include <AK/NeverDestroyed.h>
+#include <AK/Singleton.h>
+#include <AK/TemporaryChange.h>
+#include <AK/Time.h>
+#include <LibCore/Event.h>
+#include <LibCore/EventLoop.h>
+#include <LibCore/LocalServer.h>
+#include <LibCore/LocalSocket.h>
+#include <LibCore/Notifier.h>
+#include <LibCore/Object.h>
+#include <LibCore/SyscallUtils.h>
+#include <LibThread/Lock.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/select.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <time.h>
+#include <unistd.h>
+
+//#define EVENTLOOP_DEBUG
+//#define DEFERRED_INVOKE_DEBUG
+
+namespace Core {
+
+class RPCClient;
+
+struct EventLoopTimer {
+    int timer_id { 0 };
+    int interval { 0 };
+    timeval fire_time { 0, 0 };
+    bool should_reload { false };
+    TimerShouldFireWhenNotVisible fire_when_not_visible { TimerShouldFireWhenNotVisible::No };
+    WeakPtr<Object> owner;
+
+    void reload(const timeval& now);
+    bool has_expired(const timeval& now) const;
+};
+
+struct EventLoop::Private {
+    LibThread::Lock lock;
+};
+
+static EventLoop* s_main_event_loop;
+static Vector<EventLoop*>* s_event_loop_stack;
+static NeverDestroyed<IDAllocator> s_id_allocator;
+static HashMap<int, NonnullOwnPtr<EventLoopTimer>>* s_timers;
+static HashTable<Notifier*>* s_notifiers;
+int EventLoop::s_wake_pipe_fds[2];
+static RefPtr<LocalServer> s_rpc_server;
+HashMap<int, RefPtr<RPCClient>> s_rpc_clients;
+
+class SignalHandlers : public RefCounted<SignalHandlers> {
+    AK_MAKE_NONCOPYABLE(SignalHandlers);
+    AK_MAKE_NONMOVABLE(SignalHandlers);
+
+public:
+    SignalHandlers(int signo, void (*handle_signal)(int));
+    ~SignalHandlers();
+
+    void dispatch();
+    int add(Function<void(int)>&& handler);
+    bool remove(int handler_id);
+
+    bool is_empty() const
+    {
+        if (m_calling_handlers) {
+            for (auto& handler : m_handlers_pending) {
+                if (handler.value)
+                    return false; // an add is pending
+            }
+        }
+        return m_handlers.is_empty();
+    }
+
+    bool have(int handler_id) const
+    {
+        if (m_calling_handlers) {
+            auto it = m_handlers_pending.find(handler_id);
+            if (it != m_handlers_pending.end()) {
+                if (!it->value)
+                    return false; // a deletion is pending
+            }
+        }
+        return m_handlers.contains(handler_id);
+    }
+
+    int m_signo;
+    void (*m_original_handler)(int); // TODO: can't use sighandler_t?
+    HashMap<int, Function<void(int)>> m_handlers;
+    HashMap<int, Function<void(int)>> m_handlers_pending;
+    bool m_calling_handlers { false };
+};
+
+struct SignalHandlersInfo {
+    HashMap<int, NonnullRefPtr<SignalHandlers>> signal_handlers;
+    int next_signal_id { 0 };
+};
+
+template<bool create_if_null = true>
+inline SignalHandlersInfo* signals_info()
+{
+    static SignalHandlersInfo* s_signals;
+    return AK::Singleton<SignalHandlersInfo>::get(s_signals);
+}
+
+pid_t EventLoop::s_pid;
+
+class RPCClient : public Object {
+    C_OBJECT(RPCClient)
+public:
+    explicit RPCClient(RefPtr<LocalSocket> socket)
+        : m_socket(move(socket))
+        , m_client_id(s_id_allocator->allocate())
+    {
+        s_rpc_clients.set(m_client_id, this);
+        add_child(*m_socket);
+        m_socket->on_ready_to_read = [this] {
+            u32 length;
+            int nread = m_socket->read((u8*)&length, sizeof(length));
+            if (nread == 0) {
+#ifdef EVENTLOOP_DEBUG
+                dbgln("RPC client disconnected");
+#endif
+                shutdown();
+                return;
+            }
+            ASSERT(nread == sizeof(length));
+            auto request = m_socket->read(length);
+
+            auto request_json = JsonValue::from_string(request);
+            if (!request_json.has_value() || !request_json.value().is_object()) {
+                dbgln("RPC client sent invalid request");
+                shutdown();
+                return;
+            }
+
+            handle_request(request_json.value().as_object());
+        };
+    }
+    virtual ~RPCClient() override
+    {
+        if (auto inspected_object = m_inspected_object.strong_ref())
+            inspected_object->decrement_inspector_count({});
+    }
+
+    void send_response(const JsonObject& response)
+    {
+        auto serialized = response.to_string();
+        u32 length = serialized.length();
+        m_socket->write((const u8*)&length, sizeof(length));
+        m_socket->write(serialized);
+    }
+
+    void handle_request(const JsonObject& request)
+    {
+        auto type = request.get("type").as_string_or({});
+
+        if (type.is_null()) {
+            dbgln("RPC client sent request without type field");
+            return;
+        }
+
+        if (type == "Identify") {
+            JsonObject response;
+            response.set("type", type);
+            response.set("pid", getpid());
+#ifdef __serenity__
+            char buffer[1024];
+            if (get_process_name(buffer, sizeof(buffer)) >= 0) {
+                response.set("process_name", buffer);
+            } else {
+                response.set("process_name", JsonValue());
+            }
+#endif
+            send_response(response);
+            return;
+        }
+
+        if (type == "GetAllObjects") {
+            JsonObject response;
+            response.set("type", type);
+            JsonArray objects;
+            for (auto& object : Object::all_objects()) {
+                JsonObject json_object;
+                object.save_to(json_object);
+                objects.append(move(json_object));
+            }
+            response.set("objects", move(objects));
+            send_response(response);
+            return;
+        }
+
+        if (type == "SetInspectedObject") {
+            auto address = request.get("address").to_number<FlatPtr>();
+            for (auto& object : Object::all_objects()) {
+                if ((FlatPtr)&object == address) {
+                    if (auto inspected_object = m_inspected_object.strong_ref())
+                        inspected_object->decrement_inspector_count({});
+                    m_inspected_object = object;
+                    object.increment_inspector_count({});
+                    break;
+                }
+            }
+            return;
+        }
+
+        if (type == "SetProperty") {
+            auto address = request.get("address").to_number<FlatPtr>();
+            for (auto& object : Object::all_objects()) {
+                if ((FlatPtr)&object == address) {
+                    bool success = object.set_property(request.get("name").to_string(), request.get("value"));
+                    JsonObject response;
+                    response.set("type", "SetProperty");
+                    response.set("success", success);
+                    send_response(response);
+                    break;
+                }
+            }
+            return;
+        }
+
+        if (type == "Disconnect") {
+            shutdown();
+            return;
+        }
+    }
+
+    void shutdown()
+    {
+        s_rpc_clients.remove(m_client_id);
+        s_id_allocator->deallocate(m_client_id);
+    }
+
+private:
+    RefPtr<LocalSocket> m_socket;
+    WeakPtr<Object> m_inspected_object;
+    int m_client_id { -1 };
+};
+
+EventLoop::EventLoop()
+    : m_private(make<Private>())
+{
+    if (!s_event_loop_stack) {
+        s_event_loop_stack = new Vector<EventLoop*>;
+        s_timers = new HashMap<int, NonnullOwnPtr<EventLoopTimer>>;
+        s_notifiers = new HashTable<Notifier*>;
+    }
+
+    if (!s_main_event_loop) {
+        s_main_event_loop = this;
+        s_pid = getpid();
+#if defined(SOCK_NONBLOCK)
+        int rc = pipe2(s_wake_pipe_fds, O_CLOEXEC);
+#else
+        int rc = pipe(s_wake_pipe_fds);
+        fcntl(s_wake_pipe_fds[0], F_SETFD, FD_CLOEXEC);
+        fcntl(s_wake_pipe_fds[1], F_SETFD, FD_CLOEXEC);
+
+#endif
+        ASSERT(rc == 0);
+        s_event_loop_stack->append(this);
+
+        if (!s_rpc_server) {
+            if (!start_rpc_server())
+                dbgln("Core::EventLoop: Failed to start an RPC server");
+        }
+    }
+
+#ifdef EVENTLOOP_DEBUG
+    dbgln("{} Core::EventLoop constructed :)", getpid());
+#endif
+}
+
+EventLoop::~EventLoop()
+{
+}
+
+bool EventLoop::start_rpc_server()
+{
+    s_rpc_server = LocalServer::construct();
+    s_rpc_server->set_name("Core::EventLoop_RPC_server");
+    s_rpc_server->on_ready_to_accept = [&] {
+        RPCClient::construct(s_rpc_server->accept());
+    };
+    return s_rpc_server->listen(String::formatted("/tmp/rpc/{}", getpid()));
+}
+
+EventLoop& EventLoop::main()
+{
+    ASSERT(s_main_event_loop);
+    return *s_main_event_loop;
+}
+
+EventLoop& EventLoop::current()
+{
+    EventLoop* event_loop = s_event_loop_stack->last();
+    ASSERT(event_loop != nullptr);
+    return *event_loop;
+}
+
+void EventLoop::quit(int code)
+{
+#ifdef EVENTLOOP_DEBUG
+    dbgln("Core::EventLoop::quit({})", code);
+#endif
+    m_exit_requested = true;
+    m_exit_code = code;
+}
+
+void EventLoop::unquit()
+{
+#ifdef EVENTLOOP_DEBUG
+    dbgln("Core::EventLoop::unquit()");
+#endif
+    m_exit_requested = false;
+    m_exit_code = 0;
+}
+
+struct EventLoopPusher {
+public:
+    EventLoopPusher(EventLoop& event_loop)
+        : m_event_loop(event_loop)
+    {
+        if (&m_event_loop != s_main_event_loop) {
+            m_event_loop.take_pending_events_from(EventLoop::current());
+            s_event_loop_stack->append(&event_loop);
+        }
+    }
+    ~EventLoopPusher()
+    {
+        if (&m_event_loop != s_main_event_loop) {
+            s_event_loop_stack->take_last();
+            EventLoop::current().take_pending_events_from(m_event_loop);
+        }
+    }
+
+private:
+    EventLoop& m_event_loop;
+};
+
+int EventLoop::exec()
+{
+    EventLoopPusher pusher(*this);
+    for (;;) {
+        if (m_exit_requested)
+            return m_exit_code;
+        pump();
+    }
+    ASSERT_NOT_REACHED();
+}
+
+void EventLoop::pump(WaitMode mode)
+{
+    wait_for_event(mode);
+
+    decltype(m_queued_events) events;
+    {
+        LOCKER(m_private->lock);
+        events = move(m_queued_events);
+    }
+
+    for (size_t i = 0; i < events.size(); ++i) {
+        auto& queued_event = events.at(i);
+        auto receiver = queued_event.receiver.strong_ref();
+        auto& event = *queued_event.event;
+#ifdef EVENTLOOP_DEBUG
+        if (receiver)
+            dbgln("Core::EventLoop: {} event {}", *receiver, event.type());
+#endif
+        if (!receiver) {
+            switch (event.type()) {
+            case Event::Quit:
+                ASSERT_NOT_REACHED();
+                return;
+            default:
+#ifdef EVENTLOOP_DEBUG
+                dbgln("Event type {} with no receiver :(", event.type());
+#endif
+                break;
+            }
+        } else if (event.type() == Event::Type::DeferredInvoke) {
+#ifdef DEFERRED_INVOKE_DEBUG
+            dbgln("DeferredInvoke: receiver = {}", *receiver);
+#endif
+            static_cast<DeferredInvocationEvent&>(event).m_invokee(*receiver);
+        } else {
+            NonnullRefPtr<Object> protector(*receiver);
+            receiver->dispatch_event(event);
+        }
+
+        if (m_exit_requested) {
+            LOCKER(m_private->lock);
+#ifdef EVENTLOOP_DEBUG
+            dbgln("Core::EventLoop: Exit requested. Rejigging {} events.", events.size() - i);
+#endif
+            decltype(m_queued_events) new_event_queue;
+            new_event_queue.ensure_capacity(m_queued_events.size() + events.size());
+            for (++i; i < events.size(); ++i)
+                new_event_queue.unchecked_append(move(events[i]));
+            new_event_queue.append(move(m_queued_events));
+            m_queued_events = move(new_event_queue);
+            return;
+        }
+    }
+}
+
+void EventLoop::post_event(Object& receiver, NonnullOwnPtr<Event>&& event)
+{
+    LOCKER(m_private->lock);
+#ifdef EVENTLOOP_DEBUG
+    dbgln("Core::EventLoop::post_event: ({}) << receivier={}, event={}", m_queued_events.size(), receiver, event);
+#endif
+    m_queued_events.empend(receiver, move(event));
+}
+
+SignalHandlers::SignalHandlers(int signo, void (*handle_signal)(int))
+    : m_signo(signo)
+    , m_original_handler(signal(signo, handle_signal))
+{
+#ifdef EVENTLOOP_DEBUG
+    dbgln("Core::EventLoop: Registered handler for signal {}", m_signo);
+#endif
+}
+
+SignalHandlers::~SignalHandlers()
+{
+#ifdef EVENTLOOP_DEBUG
+    dbgln("Core::EventLoop: Unregistering handler for signal {}", m_signo);
+#endif
+    signal(m_signo, m_original_handler);
+}
+
+void SignalHandlers::dispatch()
+{
+    TemporaryChange change(m_calling_handlers, true);
+    for (auto& handler : m_handlers)
+        handler.value(m_signo);
+    if (!m_handlers_pending.is_empty()) {
+        // Apply pending adds/removes
+        for (auto& handler : m_handlers_pending) {
+            if (handler.value) {
+                auto result = m_handlers.set(handler.key, move(handler.value));
+                ASSERT(result == AK::HashSetResult::InsertedNewEntry);
+            } else {
+                m_handlers.remove(handler.key);
+            }
+        }
+        m_handlers_pending.clear();
+    }
+}
+
+int SignalHandlers::add(Function<void(int)>&& handler)
+{
+    int id = ++signals_info()->next_signal_id; // TODO: worry about wrapping and duplicates?
+    if (m_calling_handlers)
+        m_handlers_pending.set(id, move(handler));
+    else
+        m_handlers.set(id, move(handler));
+    return id;
+}
+
+bool SignalHandlers::remove(int handler_id)
+{
+    ASSERT(handler_id != 0);
+    if (m_calling_handlers) {
+        auto it = m_handlers.find(handler_id);
+        if (it != m_handlers.end()) {
+            // Mark pending remove
+            m_handlers_pending.set(handler_id, {});
+            return true;
+        }
+        it = m_handlers_pending.find(handler_id);
+        if (it != m_handlers_pending.end()) {
+            if (!it->value)
+                return false; // already was marked as deleted
+            it->value = nullptr;
+            return true;
+        }
+        return false;
+    }
+    return m_handlers.remove(handler_id);
+}
+
+void EventLoop::dispatch_signal(int signo)
+{
+    auto& info = *signals_info();
+    auto handlers = info.signal_handlers.find(signo);
+    if (handlers != info.signal_handlers.end()) {
+        // Make sure we bump the ref count while dispatching the handlers!
+        // This allows a handler to unregister/register while the handlers
+        // are being called!
+        auto handler = handlers->value;
+#ifdef EVENTLOOP_DEBUG
+        dbgln("Core::EventLoop: dispatching signal {}", signo);
+#endif
+        handler->dispatch();
+    }
+}
+
+void EventLoop::handle_signal(int signo)
+{
+    ASSERT(signo != 0);
+    // We MUST check if the current pid still matches, because there
+    // is a window between fork() and exec() where a signal delivered
+    // to our fork could be inadvertedly routed to the parent process!
+    if (getpid() == s_pid) {
+        int nwritten = write(s_wake_pipe_fds[1], &signo, sizeof(signo));
+        if (nwritten < 0) {
+            perror("EventLoop::register_signal: write");
+            ASSERT_NOT_REACHED();
+        }
+    } else {
+        // We're a fork who received a signal, reset s_pid
+        s_pid = 0;
+    }
+}
+
+int EventLoop::register_signal(int signo, Function<void(int)> handler)
+{
+    ASSERT(signo != 0);
+    auto& info = *signals_info();
+    auto handlers = info.signal_handlers.find(signo);
+    if (handlers == info.signal_handlers.end()) {
+        auto signal_handlers = adopt(*new SignalHandlers(signo, EventLoop::handle_signal));
+        auto handler_id = signal_handlers->add(move(handler));
+        info.signal_handlers.set(signo, move(signal_handlers));
+        return handler_id;
+    } else {
+        return handlers->value->add(move(handler));
+    }
+}
+
+void EventLoop::unregister_signal(int handler_id)
+{
+    ASSERT(handler_id != 0);
+    int remove_signo = 0;
+    auto& info = *signals_info();
+    for (auto& h : info.signal_handlers) {
+        auto& handlers = *h.value;
+        if (handlers.remove(handler_id)) {
+            if (handlers.is_empty())
+                remove_signo = handlers.m_signo;
+            break;
+        }
+    }
+    if (remove_signo != 0)
+        info.signal_handlers.remove(remove_signo);
+}
+
+void EventLoop::notify_forked(ForkEvent event)
+{
+    switch (event) {
+    case ForkEvent::Child:
+        s_main_event_loop = nullptr;
+        s_event_loop_stack->clear();
+        s_timers->clear();
+        s_notifiers->clear();
+        if (auto* info = signals_info<false>()) {
+            info->signal_handlers.clear();
+            info->next_signal_id = 0;
+        }
+        s_pid = 0;
+        s_rpc_server = nullptr;
+        s_rpc_clients.clear();
+        return;
+    }
+
+    ASSERT_NOT_REACHED();
+}
+
+void EventLoop::wait_for_event(WaitMode mode)
+{
+    fd_set rfds;
+    fd_set wfds;
+retry:
+    FD_ZERO(&rfds);
+    FD_ZERO(&wfds);
+
+    int max_fd = 0;
+    auto add_fd_to_set = [&max_fd](int fd, fd_set& set) {
+        FD_SET(fd, &set);
+        if (fd > max_fd)
+            max_fd = fd;
+    };
+
+    int max_fd_added = -1;
+    add_fd_to_set(s_wake_pipe_fds[0], rfds);
+    max_fd = max(max_fd, max_fd_added);
+    for (auto& notifier : *s_notifiers) {
+        if (notifier->event_mask() & Notifier::Read)
+            add_fd_to_set(notifier->fd(), rfds);
+        if (notifier->event_mask() & Notifier::Write)
+            add_fd_to_set(notifier->fd(), wfds);
+        if (notifier->event_mask() & Notifier::Exceptional)
+            ASSERT_NOT_REACHED();
+    }
+
+    bool queued_events_is_empty;
+    {
+        LOCKER(m_private->lock);
+        queued_events_is_empty = m_queued_events.is_empty();
+    }
+
+    timeval now;
+    struct timeval timeout = { 0, 0 };
+    bool should_wait_forever = false;
+    if (mode == WaitMode::WaitForEvents && queued_events_is_empty) {
+        auto next_timer_expiration = get_next_timer_expiration();
+        if (next_timer_expiration.has_value()) {
+            timespec now_spec;
+            clock_gettime(CLOCK_MONOTONIC_COARSE, &now_spec);
+            now.tv_sec = now_spec.tv_sec;
+            now.tv_usec = now_spec.tv_nsec / 1000;
+            timeval_sub(next_timer_expiration.value(), now, timeout);
+            if (timeout.tv_sec < 0 || (timeout.tv_sec == 0 && timeout.tv_usec < 0)) {
+                timeout.tv_sec = 0;
+                timeout.tv_usec = 0;
+            }
+        } else {
+            should_wait_forever = true;
+        }
+    }
+
+try_select_again:
+    int marked_fd_count = select(max_fd + 1, &rfds, &wfds, nullptr, should_wait_forever ? nullptr : &timeout);
+    if (marked_fd_count < 0) {
+        int saved_errno = errno;
+        if (saved_errno == EINTR) {
+            if (m_exit_requested)
+                return;
+            goto try_select_again;
+        }
+#ifdef EVENTLOOP_DEBUG
+        dbgln("Core::EventLoop::wait_for_event: {} ({}: {})", marked_fd_count, saved_errno, strerror(saved_errno));
+#endif
+        // Blow up, similar to Core::safe_syscall.
+        ASSERT_NOT_REACHED();
+    }
+    if (FD_ISSET(s_wake_pipe_fds[0], &rfds)) {
+        int wake_events[8];
+        auto nread = read(s_wake_pipe_fds[0], wake_events, sizeof(wake_events));
+        if (nread < 0) {
+            perror("read from wake pipe");
+            ASSERT_NOT_REACHED();
+        }
+        ASSERT(nread > 0);
+        bool wake_requested = false;
+        int event_count = nread / sizeof(wake_events[0]);
+        for (int i = 0; i < event_count; i++) {
+            if (wake_events[i] != 0)
+                dispatch_signal(wake_events[i]);
+            else
+                wake_requested = true;
+        }
+
+        if (!wake_requested && nread == sizeof(wake_events))
+            goto retry;
+    }
+
+    if (!s_timers->is_empty()) {
+        timespec now_spec;
+        clock_gettime(CLOCK_MONOTONIC_COARSE, &now_spec);
+        now.tv_sec = now_spec.tv_sec;
+        now.tv_usec = now_spec.tv_nsec / 1000;
+    }
+
+    for (auto& it : *s_timers) {
+        auto& timer = *it.value;
+        if (!timer.has_expired(now))
+            continue;
+        auto owner = timer.owner.strong_ref();
+        if (timer.fire_when_not_visible == TimerShouldFireWhenNotVisible::No
+            && owner && !owner->is_visible_for_timer_purposes()) {
+            continue;
+        }
+#ifdef EVENTLOOP_DEBUG
+        dbgln("Core::EventLoop: Timer {} has expired, sending Core::TimerEvent to {}", timer.timer_id, *owner);
+#endif
+        if (owner)
+            post_event(*owner, make<TimerEvent>(timer.timer_id));
+        if (timer.should_reload) {
+            timer.reload(now);
+        } else {
+            // FIXME: Support removing expired timers that don't want to reload.
+            ASSERT_NOT_REACHED();
+        }
+    }
+
+    if (!marked_fd_count)
+        return;
+
+    for (auto& notifier : *s_notifiers) {
+        if (FD_ISSET(notifier->fd(), &rfds)) {
+            if (notifier->event_mask() & Notifier::Event::Read)
+                post_event(*notifier, make<NotifierReadEvent>(notifier->fd()));
+        }
+        if (FD_ISSET(notifier->fd(), &wfds)) {
+            if (notifier->event_mask() & Notifier::Event::Write)
+                post_event(*notifier, make<NotifierWriteEvent>(notifier->fd()));
+        }
+    }
+}
+
+bool EventLoopTimer::has_expired(const timeval& now) const
+{
+    return now.tv_sec > fire_time.tv_sec || (now.tv_sec == fire_time.tv_sec && now.tv_usec >= fire_time.tv_usec);
+}
+
+void EventLoopTimer::reload(const timeval& now)
+{
+    fire_time = now;
+    fire_time.tv_sec += interval / 1000;
+    fire_time.tv_usec += (interval % 1000) * 1000;
+}
+
+Optional<struct timeval> EventLoop::get_next_timer_expiration()
+{
+    Optional<struct timeval> soonest {};
+    for (auto& it : *s_timers) {
+        auto& fire_time = it.value->fire_time;
+        auto owner = it.value->owner.strong_ref();
+        if (it.value->fire_when_not_visible == TimerShouldFireWhenNotVisible::No
+            && owner && !owner->is_visible_for_timer_purposes()) {
+            continue;
+        }
+        if (!soonest.has_value() || fire_time.tv_sec < soonest.value().tv_sec || (fire_time.tv_sec == soonest.value().tv_sec && fire_time.tv_usec < soonest.value().tv_usec))
+            soonest = fire_time;
+    }
+    return soonest;
+}
+
+int EventLoop::register_timer(Object& object, int milliseconds, bool should_reload, TimerShouldFireWhenNotVisible fire_when_not_visible)
+{
+    ASSERT(milliseconds >= 0);
+    auto timer = make<EventLoopTimer>();
+    timer->owner = object;
+    timer->interval = milliseconds;
+    timeval now;
+    timespec now_spec;
+    clock_gettime(CLOCK_MONOTONIC_COARSE, &now_spec);
+    now.tv_sec = now_spec.tv_sec;
+    now.tv_usec = now_spec.tv_nsec / 1000;
+    timer->reload(now);
+    timer->should_reload = should_reload;
+    timer->fire_when_not_visible = fire_when_not_visible;
+    int timer_id = s_id_allocator->allocate();
+    timer->timer_id = timer_id;
+    s_timers->set(timer_id, move(timer));
+    return timer_id;
+}
+
+bool EventLoop::unregister_timer(int timer_id)
+{
+    s_id_allocator->deallocate(timer_id);
+    auto it = s_timers->find(timer_id);
+    if (it == s_timers->end())
+        return false;
+    s_timers->remove(it);
+    return true;
+}
+
+void EventLoop::register_notifier(Badge<Notifier>, Notifier& notifier)
+{
+    s_notifiers->set(&notifier);
+}
+
+void EventLoop::unregister_notifier(Badge<Notifier>, Notifier& notifier)
+{
+    s_notifiers->remove(&notifier);
+}
+
+void EventLoop::wake()
+{
+    int wake_event = 0;
+    int nwritten = write(s_wake_pipe_fds[1], &wake_event, sizeof(wake_event));
+    if (nwritten < 0) {
+        perror("EventLoop::wake: write");
+        ASSERT_NOT_REACHED();
+    }
+}
+
+EventLoop::QueuedEvent::QueuedEvent(Object& receiver, NonnullOwnPtr<Event> event)
+    : receiver(receiver)
+    , event(move(event))
+{
+}
+
+EventLoop::QueuedEvent::QueuedEvent(QueuedEvent&& other)
+    : receiver(other.receiver)
+    , event(move(other.event))
+{
+}
+
+EventLoop::QueuedEvent::~QueuedEvent()
+{
+}
+
+}

Userland/Libraries/LibCore/EventLoop.h

@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <AK/Function.h>
+#include <AK/HashMap.h>
+#include <AK/Noncopyable.h>
+#include <AK/NonnullOwnPtr.h>
+#include <AK/Vector.h>
+#include <AK/WeakPtr.h>
+#include <LibCore/Forward.h>
+#include <sys/time.h>
+#include <sys/types.h>
+
+namespace Core {
+
+class EventLoop {
+public:
+    EventLoop();
+    ~EventLoop();
+
+    int exec();
+
+    enum class WaitMode {
+        WaitForEvents,
+        PollForEvents,
+    };
+
+    // processe events, generally called by exec() in a loop.
+    // this should really only be used for integrating with other event loops
+    void pump(WaitMode = WaitMode::WaitForEvents);
+
+    void post_event(Object& receiver, NonnullOwnPtr<Event>&&);
+
+    static EventLoop& main();
+    static EventLoop& current();
+
+    bool was_exit_requested() const { return m_exit_requested; }
+
+    static int register_timer(Object&, int milliseconds, bool should_reload, TimerShouldFireWhenNotVisible);
+    static bool unregister_timer(int timer_id);
+
+    static void register_notifier(Badge<Notifier>, Notifier&);
+    static void unregister_notifier(Badge<Notifier>, Notifier&);
+
+    void quit(int);
+    void unquit();
+
+    void take_pending_events_from(EventLoop& other)
+    {
+        m_queued_events.append(move(other.m_queued_events));
+    }
+
+    static void wake();
+
+    static int register_signal(int signo, Function<void(int)> handler);
+    static void unregister_signal(int handler_id);
+
+    // Note: Boost uses Parent/Child/Prepare, but we don't really have anything
+    //       interesting to do in the parent or before forking.
+    enum class ForkEvent {
+        Child,
+    };
+    static void notify_forked(ForkEvent);
+
+private:
+    bool start_rpc_server();
+    void wait_for_event(WaitMode);
+    Optional<struct timeval> get_next_timer_expiration();
+    static void dispatch_signal(int);
+    static void handle_signal(int);
+
+    struct QueuedEvent {
+        AK_MAKE_NONCOPYABLE(QueuedEvent);
+
+    public:
+        QueuedEvent(Object& receiver, NonnullOwnPtr<Event>);
+        QueuedEvent(QueuedEvent&&);
+        ~QueuedEvent();
+
+        WeakPtr<Object> receiver;
+        NonnullOwnPtr<Event> event;
+    };
+
+    Vector<QueuedEvent, 64> m_queued_events;
+    static pid_t s_pid;
+
+    bool m_exit_requested { false };
+    int m_exit_code { 0 };
+
+    static int s_wake_pipe_fds[2];
+
+    struct Private;
+    NonnullOwnPtr<Private> m_private;
+};
+
+}

Userland/Libraries/LibCore/File.cpp

@@ -0,0 +1,270 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifdef __serenity__
+#    include <Kernel/API/Syscall.h>
+#endif
+#include <AK/ScopeGuard.h>
+#include <LibCore/File.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <libgen.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+namespace Core {
+
+Result<NonnullRefPtr<File>, String> File::open(const String& filename, IODevice::OpenMode mode, mode_t permissions)
+{
+    auto file = File::construct(filename);
+    if (!file->open_impl(mode, permissions))
+        return String(file->error_string());
+    return file;
+}
+
+File::File(const StringView& filename, Object* parent)
+    : IODevice(parent)
+    , m_filename(filename)
+{
+}
+
+File::~File()
+{
+    if (m_should_close_file_descriptor == ShouldCloseFileDescriptor::Yes && mode() != NotOpen)
+        close();
+}
+
+bool File::open(int fd, IODevice::OpenMode mode, ShouldCloseFileDescriptor should_close)
+{
+    set_fd(fd);
+    set_mode(mode);
+    m_should_close_file_descriptor = should_close;
+    return true;
+}
+
+bool File::open(IODevice::OpenMode mode)
+{
+    return open_impl(mode, 0666);
+}
+
+bool File::open_impl(IODevice::OpenMode mode, mode_t permissions)
+{
+    ASSERT(!m_filename.is_null());
+    int flags = 0;
+    if ((mode & IODevice::ReadWrite) == IODevice::ReadWrite) {
+        flags |= O_RDWR | O_CREAT;
+    } else if (mode & IODevice::ReadOnly) {
+        flags |= O_RDONLY;
+    } else if (mode & IODevice::WriteOnly) {
+        flags |= O_WRONLY | O_CREAT;
+        bool should_truncate = !((mode & IODevice::Append) || (mode & IODevice::MustBeNew));
+        if (should_truncate)
+            flags |= O_TRUNC;
+    }
+    if (mode & IODevice::Append)
+        flags |= O_APPEND;
+    if (mode & IODevice::Truncate)
+        flags |= O_TRUNC;
+    if (mode & IODevice::MustBeNew)
+        flags |= O_EXCL;
+    int fd = ::open(m_filename.characters(), flags, permissions);
+    if (fd < 0) {
+        set_error(errno);
+        return false;
+    }
+
+    set_fd(fd);
+    set_mode(mode);
+    return true;
+}
+
+bool File::is_directory() const
+{
+    struct stat stat;
+    if (fstat(fd(), &stat) < 0)
+        return false;
+    return S_ISDIR(stat.st_mode);
+}
+
+bool File::is_directory(const String& filename)
+{
+    struct stat st;
+    if (stat(filename.characters(), &st) < 0)
+        return false;
+    return S_ISDIR(st.st_mode);
+}
+
+bool File::exists(const String& filename)
+{
+    struct stat st;
+    return stat(filename.characters(), &st) == 0;
+}
+
+String File::real_path_for(const String& filename)
+{
+    if (filename.is_null())
+        return {};
+    auto* path = realpath(filename.characters(), nullptr);
+    String real_path(path);
+    free(path);
+    return real_path;
+}
+
+bool File::ensure_parent_directories(const String& path)
+{
+    ASSERT(path.starts_with("/"));
+
+    int saved_errno = 0;
+    ScopeGuard restore_errno = [&saved_errno] { errno = saved_errno; };
+
+    char* parent_buffer = strdup(path.characters());
+    ScopeGuard free_buffer = [parent_buffer] { free(parent_buffer); };
+
+    const char* parent = dirname(parent_buffer);
+
+    int rc = mkdir(parent, 0755);
+    saved_errno = errno;
+
+    if (rc == 0 || errno == EEXIST)
+        return true;
+
+    if (errno != ENOENT)
+        return false;
+
+    bool ok = ensure_parent_directories(parent);
+    saved_errno = errno;
+    if (!ok)
+        return false;
+
+    rc = mkdir(parent, 0755);
+    saved_errno = errno;
+    return rc == 0;
+}
+
+#ifdef __serenity__
+
+String File::read_link(const StringView& link_path)
+{
+    // First, try using a 64-byte buffer, that ought to be enough for anybody.
+    char small_buffer[64];
+    Syscall::SC_readlink_params small_params {
+        { link_path.characters_without_null_termination(), link_path.length() },
+        { small_buffer, sizeof(small_buffer) }
+    };
+    int rc = syscall(SC_readlink, &small_params);
+    if (rc < 0) {
+        errno = -rc;
+        return {};
+    }
+    size_t size = rc;
+    // If the call was successful, the syscall (unlike the LibC wrapper)
+    // returns the full size of the link. Let's see if our small buffer
+    // was enough to read the whole link.
+    if (size <= sizeof(small_buffer))
+        return { small_buffer, size };
+    // Nope, but at least now we know the right size.
+    char* large_buffer_ptr;
+    auto large_buffer = StringImpl::create_uninitialized(size, large_buffer_ptr);
+    Syscall::SC_readlink_params large_params {
+        { link_path.characters_without_null_termination(), link_path.length() },
+        { large_buffer_ptr, (size_t)size }
+    };
+    rc = syscall(SC_readlink, &large_params);
+    if (rc < 0) {
+        errno = -rc;
+        return {};
+    }
+    size_t new_size = rc;
+    if (new_size == size)
+        return { *large_buffer };
+
+    // If we're here, the symlink has changed while we were looking at it.
+    // If it became shorter, our buffer is valid, we just have to trim it a bit.
+    if (new_size < size)
+        return { large_buffer_ptr, new_size };
+    // Otherwise, here's not much we can do, unless we want to loop endlessly
+    // in this case. Let's leave it up to the caller whether to loop.
+    errno = -EAGAIN;
+    return {};
+}
+
+#else
+
+// This is a sad version for other systems. It has to always make a copy of the
+// link path, and to always make two syscalls to get the right size first.
+String File::read_link(const StringView& link_path)
+{
+    String link_path_str = link_path;
+    struct stat statbuf;
+    int rc = lstat(link_path_str.characters(), &statbuf);
+    if (rc < 0)
+        return {};
+    char* buffer_ptr;
+    auto buffer = StringImpl::create_uninitialized(statbuf.st_size, buffer_ptr);
+    rc = readlink(link_path_str.characters(), buffer_ptr, statbuf.st_size);
+    if (rc < 0)
+        return {};
+    // (See above.)
+    if (rc == statbuf.st_size)
+        return { *buffer };
+    return { buffer_ptr, (size_t)rc };
+}
+
+#endif
+
+static RefPtr<File> stdin_file;
+static RefPtr<File> stdout_file;
+static RefPtr<File> stderr_file;
+
+NonnullRefPtr<File> File::standard_input()
+{
+    if (!stdin_file) {
+        stdin_file = File::construct();
+        stdin_file->open(STDIN_FILENO, IODevice::ReadOnly, ShouldCloseFileDescriptor::No);
+    }
+    return *stdin_file;
+}
+
+NonnullRefPtr<File> File::standard_output()
+{
+    if (!stdout_file) {
+        stdout_file = File::construct();
+        stdout_file->open(STDOUT_FILENO, IODevice::WriteOnly, ShouldCloseFileDescriptor::No);
+    }
+    return *stdout_file;
+}
+
+NonnullRefPtr<File> File::standard_error()
+{
+    if (!stderr_file) {
+        stderr_file = File::construct();
+        stderr_file->open(STDERR_FILENO, IODevice::WriteOnly, ShouldCloseFileDescriptor::No);
+    }
+    return *stderr_file;
+}
+}

Userland/Libraries/LibCore/File.h

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Result.h>
+#include <AK/String.h>
+#include <LibCore/IODevice.h>
+
+namespace Core {
+
+class File final : public IODevice {
+    C_OBJECT(File)
+public:
+    virtual ~File() override;
+
+    static Result<NonnullRefPtr<File>, String> open(const String& filename, IODevice::OpenMode, mode_t = 0644);
+
+    String filename() const { return m_filename; }
+    void set_filename(const StringView& filename) { m_filename = filename; }
+
+    bool is_directory() const;
+    static bool is_directory(const String& filename);
+
+    static bool exists(const String& filename);
+    static String real_path_for(const String& filename);
+    static String read_link(const StringView& link_path);
+    static bool ensure_parent_directories(const String& path);
+
+    virtual bool open(IODevice::OpenMode) override;
+
+    enum class ShouldCloseFileDescriptor {
+        No = 0,
+        Yes
+    };
+    bool open(int fd, IODevice::OpenMode, ShouldCloseFileDescriptor);
+
+    static NonnullRefPtr<File> standard_input();
+    static NonnullRefPtr<File> standard_output();
+    static NonnullRefPtr<File> standard_error();
+
+private:
+    File(Object* parent = nullptr)
+        : IODevice(parent)
+    {
+    }
+    explicit File(const StringView&, Object* parent = nullptr);
+
+    bool open_impl(IODevice::OpenMode, mode_t);
+
+    String m_filename;
+    ShouldCloseFileDescriptor m_should_close_file_descriptor { ShouldCloseFileDescriptor::Yes };
+};
+
+}

Userland/Libraries/LibCore/FileStream.h

@@ -0,0 +1,171 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Buffered.h>
+#include <AK/ByteBuffer.h>
+#include <AK/Stream.h>
+#include <LibCore/File.h>
+
+namespace Core {
+
+class InputFileStream final : public InputStream {
+public:
+    explicit InputFileStream(NonnullRefPtr<File> file)
+        : m_file(file)
+    {
+    }
+
+    static Result<InputFileStream, String> open(StringView filename, IODevice::OpenMode mode = IODevice::OpenMode::ReadOnly, mode_t permissions = 0644)
+    {
+        ASSERT((mode & 0xf) == IODevice::OpenMode::ReadOnly || (mode & 0xf) == IODevice::OpenMode::ReadWrite);
+
+        auto file_result = File::open(filename, mode, permissions);
+
+        if (file_result.is_error())
+            return file_result.error();
+
+        return InputFileStream { file_result.value() };
+    }
+
+    static Result<Buffered<InputFileStream>, String> open_buffered(StringView filename, IODevice::OpenMode mode = IODevice::OpenMode::ReadOnly, mode_t permissions = 0644)
+    {
+        ASSERT((mode & 0xf) == IODevice::OpenMode::ReadOnly || (mode & 0xf) == IODevice::OpenMode::ReadWrite);
+
+        auto file_result = File::open(filename, mode, permissions);
+
+        if (file_result.is_error())
+            return file_result.error();
+
+        return Buffered<InputFileStream> { file_result.value() };
+    }
+
+    size_t read(Bytes bytes) override
+    {
+        if (has_any_error())
+            return 0;
+
+        const auto buffer = m_file->read(bytes.size());
+        return buffer.bytes().copy_to(bytes);
+    }
+
+    bool read_or_error(Bytes bytes) override
+    {
+        if (read(bytes) < bytes.size()) {
+            set_fatal_error();
+            return false;
+        }
+
+        return true;
+    }
+
+    bool discard_or_error(size_t count) override { return m_file->seek(count, IODevice::SeekMode::FromCurrentPosition); }
+
+    bool unreliable_eof() const override { return m_file->eof(); }
+
+    void close()
+    {
+        if (!m_file->close())
+            set_fatal_error();
+    }
+
+private:
+    NonnullRefPtr<File> m_file;
+};
+
+class OutputFileStream : public OutputStream {
+public:
+    explicit OutputFileStream(NonnullRefPtr<File> file)
+        : m_file(file)
+    {
+    }
+
+    static Result<OutputFileStream, String> open(StringView filename, IODevice::OpenMode mode = IODevice::OpenMode::WriteOnly, mode_t permissions = 0644)
+    {
+        ASSERT((mode & 0xf) == IODevice::OpenMode::WriteOnly || (mode & 0xf) == IODevice::OpenMode::ReadWrite);
+
+        auto file_result = File::open(filename, mode, permissions);
+
+        if (file_result.is_error())
+            return file_result.error();
+
+        return OutputFileStream { file_result.value() };
+    }
+
+    static Result<Buffered<OutputFileStream>, String> open_buffered(StringView filename, IODevice::OpenMode mode = IODevice::OpenMode::WriteOnly, mode_t permissions = 0644)
+    {
+        ASSERT((mode & 0xf) == IODevice::OpenMode::WriteOnly || (mode & 0xf) == IODevice::OpenMode::ReadWrite);
+
+        auto file_result = File::open(filename, mode, permissions);
+
+        if (file_result.is_error())
+            return file_result.error();
+
+        return Buffered<OutputFileStream> { file_result.value() };
+    }
+
+    static OutputFileStream standard_output()
+    {
+        return OutputFileStream { Core::File::standard_output() };
+    }
+
+    static Buffered<OutputFileStream> stdout_buffered()
+    {
+        return Buffered<OutputFileStream> { Core::File::standard_output() };
+    }
+
+    size_t write(ReadonlyBytes bytes) override
+    {
+        if (!m_file->write(bytes.data(), bytes.size())) {
+            set_fatal_error();
+            return 0;
+        }
+
+        return bytes.size();
+    }
+
+    bool write_or_error(ReadonlyBytes bytes) override
+    {
+        if (write(bytes) < bytes.size()) {
+            set_fatal_error();
+            return false;
+        }
+
+        return true;
+    }
+
+    void close()
+    {
+        if (!m_file->close())
+            set_fatal_error();
+    }
+
+private:
+    NonnullRefPtr<File> m_file;
+};
+
+}

Userland/Libraries/LibCore/Forward.h

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+namespace Core {
+
+class ArgsParser;
+class ChildEvent;
+class ConfigFile;
+class CustomEvent;
+class DateTime;
+class DirIterator;
+class ElapsedTimer;
+class Event;
+class EventLoop;
+class File;
+class IODevice;
+class LocalServer;
+class LocalSocket;
+class MimeData;
+class NetworkJob;
+class NetworkResponse;
+class Notifier;
+class Object;
+class ProcessStatisticsReader;
+class Socket;
+class SocketAddress;
+class TCPServer;
+class TCPSocket;
+class Timer;
+class TimerEvent;
+class UDPServer;
+class UDPSocket;
+
+enum class TimerShouldFireWhenNotVisible;
+
+}

Userland/Libraries/LibCore/GetPassword.cpp

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2020, Peter Elliott <pelliott@ualberta.ca>
+ * Copyright (c) 2021, Emanuele Torre <torreemanuele6@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/GetPassword.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <termios.h>
+
+namespace Core {
+
+Result<String, OSError> get_password(const StringView& prompt)
+{
+    if (write(STDOUT_FILENO, prompt.characters_without_null_termination(), prompt.length()) < 0)
+        return OSError(errno);
+
+    termios original {};
+    if (tcgetattr(STDIN_FILENO, &original) < 0)
+        return OSError(errno);
+
+    termios no_echo = original;
+    no_echo.c_lflag &= ~ECHO;
+    if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &no_echo) < 0)
+        return OSError(errno);
+
+    char* password = nullptr;
+    size_t n = 0;
+
+    auto line_length = getline(&password, &n, stdin);
+    auto saved_errno = errno;
+
+    tcsetattr(STDIN_FILENO, TCSAFLUSH, &original);
+    putchar('\n');
+
+    if (line_length < 0)
+        return OSError(saved_errno);
+
+    ASSERT(line_length != 0);
+
+    // Remove trailing '\n' read by getline().
+    password[line_length - 1] = '\0';
+
+    String s(password);
+    free(password);
+    return s;
+}
+}

Userland/Libraries/LibCore/GetPassword.h

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2020, Peter Elliott <pelliott@ualberta.ca>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/OSError.h>
+#include <AK/Result.h>
+#include <AK/String.h>
+
+namespace Core {
+
+Result<String, OSError> get_password(const StringView& prompt = "Password: ");
+
+}

Userland/Libraries/LibCore/Gzip.cpp

@@ -0,0 +1,165 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/ByteBuffer.h>
+#include <AK/Optional.h>
+#include <LibCore/Gzip.h>
+#include <LibCore/puff.h>
+#include <limits.h>
+#include <stddef.h>
+
+//#define DEBUG_GZIP
+
+namespace Core {
+
+bool Gzip::is_compressed(const ByteBuffer& data)
+{
+    return data.size() > 2 && data[0] == 0x1F && data[1] == 0x8b;
+}
+
+// skips the gzip header
+// see: https://tools.ietf.org/html/rfc1952#page-5
+static Optional<ByteBuffer> get_gzip_payload(const ByteBuffer& data)
+{
+    size_t current = 0;
+    auto read_byte = [&]() {
+        if (current >= data.size()) {
+            ASSERT_NOT_REACHED();
+            return (u8)0;
+        }
+        return data[current++];
+    };
+
+#ifdef DEBUG_GZIP
+    dbgln("get_gzip_payload: Skipping over gzip header.");
+#endif
+
+    // Magic Header
+    if (read_byte() != 0x1F || read_byte() != 0x8B) {
+        dbgln("get_gzip_payload: Wrong magic number.");
+        return Optional<ByteBuffer>();
+    }
+
+    // Compression method
+    auto method = read_byte();
+    if (method != 8) {
+        dbgln("get_gzip_payload: Wrong compression method={}", method);
+        return Optional<ByteBuffer>();
+    }
+
+    u8 flags = read_byte();
+
+    // Timestamp, Extra flags, OS
+    current += 6;
+
+    // FEXTRA
+    if (flags & 4) {
+        u16 length = read_byte() & read_byte() << 8;
+        dbgln("get_gzip_payload: Header has FEXTRA flag set. length={}", length);
+        current += length;
+    }
+
+    // FNAME
+    if (flags & 8) {
+        dbgln("get_gzip_payload: Header has FNAME flag set.");
+        while (read_byte() != '\0')
+            ;
+    }
+
+    // FCOMMENT
+    if (flags & 16) {
+        dbgln("get_gzip_payload: Header has FCOMMENT flag set.");
+        while (read_byte() != '\0')
+            ;
+    }
+
+    // FHCRC
+    if (flags & 2) {
+        dbgln("get_gzip_payload: Header has FHCRC flag set.");
+        current += 2;
+    }
+
+    auto new_size = data.size() - current;
+#ifdef DEBUG_GZIP
+    dbg() << "get_gzip_payload: Returning slice from " << current << " with size " << new_size;
+#endif
+    return data.slice(current, new_size);
+}
+
+Optional<ByteBuffer> Gzip::decompress(const ByteBuffer& data)
+{
+    ASSERT(is_compressed(data));
+
+#ifdef DEBUG_GZIP
+    dbg() << "Gzip::decompress: Decompressing gzip compressed data. Size = " << data.size();
+#endif
+    auto optional_payload = get_gzip_payload(data);
+    if (!optional_payload.has_value()) {
+        return Optional<ByteBuffer>();
+    }
+
+    auto source = optional_payload.value();
+    unsigned long source_len = source.size();
+    auto destination = ByteBuffer::create_uninitialized(1024);
+    while (true) {
+        unsigned long destination_len = destination.size();
+
+#ifdef DEBUG_GZIP
+        dbg() << "Gzip::decompress: Calling puff()\n"
+              << "  destination_data = " << destination.data() << "\n"
+              << "  destination_len = " << destination_len << "\n"
+              << "  source_data = " << source.data() << "\n"
+              << "  source_len = " << source_len;
+#endif
+
+        auto puff_ret = puff(
+            destination.data(), &destination_len,
+            source.data(), &source_len);
+
+        if (puff_ret == 0) {
+#ifdef DEBUG_GZIP
+            dbgln("Gzip::decompress: Decompression success.");
+#endif
+            destination.trim(destination_len);
+            break;
+        }
+
+        if (puff_ret == 1) {
+            // FIXME: Find a better way of decompressing without needing to try over and over again.
+#ifdef DEBUG_GZIP
+            dbgln("Gzip::decompress: Output buffer exhausted. Growing.");
+#endif
+            destination.grow(destination.size() * 2);
+        } else {
+            dbgln("Gzip::decompress: Error. puff() returned: {}", puff_ret);
+            ASSERT_NOT_REACHED();
+        }
+    }
+
+    return destination;
+}
+
+}

Userland/Libraries/LibCore/Gzip.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/ByteBuffer.h>
+#include <AK/Optional.h>
+#include <AK/String.h>
+
+namespace Core {
+
+class Gzip {
+public:
+    static bool is_compressed(const ByteBuffer& data);
+    static Optional<ByteBuffer> decompress(const ByteBuffer& data);
+};
+
+}

Userland/Libraries/LibCore/IODevice.cpp

@@ -0,0 +1,336 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/ByteBuffer.h>
+#include <AK/PrintfImplementation.h>
+#include <LibCore/IODevice.h>
+#include <LibCore/SyscallUtils.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/select.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+namespace Core {
+
+IODevice::IODevice(Object* parent)
+    : Object(parent)
+{
+}
+
+IODevice::~IODevice()
+{
+}
+
+const char* IODevice::error_string() const
+{
+    return strerror(m_error);
+}
+
+int IODevice::read(u8* buffer, int length)
+{
+    auto read_buffer = read(length);
+    if (read_buffer.is_null())
+        return 0;
+    memcpy(buffer, read_buffer.data(), length);
+    return read_buffer.size();
+}
+
+ByteBuffer IODevice::read(size_t max_size)
+{
+    if (m_fd < 0)
+        return {};
+    if (!max_size)
+        return {};
+    auto buffer = ByteBuffer::create_uninitialized(max_size);
+    auto* buffer_ptr = (char*)buffer.data();
+    size_t remaining_buffer_space = buffer.size();
+    size_t taken_from_buffered = 0;
+    if (!m_buffered_data.is_empty()) {
+        taken_from_buffered = min(remaining_buffer_space, m_buffered_data.size());
+        memcpy(buffer_ptr, m_buffered_data.data(), taken_from_buffered);
+        Vector<u8> new_buffered_data;
+        new_buffered_data.append(m_buffered_data.data() + taken_from_buffered, m_buffered_data.size() - taken_from_buffered);
+        m_buffered_data = move(new_buffered_data);
+        remaining_buffer_space -= taken_from_buffered;
+        buffer_ptr += taken_from_buffered;
+    }
+    if (!remaining_buffer_space)
+        return buffer;
+    int nread = ::read(m_fd, buffer_ptr, remaining_buffer_space);
+    if (nread < 0) {
+        if (taken_from_buffered) {
+            buffer.trim(taken_from_buffered);
+            return buffer;
+        }
+        set_error(errno);
+        return {};
+    }
+    if (nread == 0) {
+        set_eof(true);
+        if (taken_from_buffered) {
+            buffer.trim(taken_from_buffered);
+            return buffer;
+        }
+        return {};
+    }
+    buffer.trim(taken_from_buffered + nread);
+    return buffer;
+}
+
+bool IODevice::can_read_from_fd() const
+{
+    // FIXME: Can we somehow remove this once Core::Socket is implemented using non-blocking sockets?
+    fd_set rfds;
+    FD_ZERO(&rfds);
+    FD_SET(m_fd, &rfds);
+    struct timeval timeout {
+        0, 0
+    };
+    int rc = Core::safe_syscall(select, m_fd + 1, &rfds, nullptr, nullptr, &timeout);
+    if (rc < 0) {
+        // NOTE: We don't set m_error here.
+        perror("IODevice::can_read: select");
+        return false;
+    }
+    return FD_ISSET(m_fd, &rfds);
+}
+
+bool IODevice::can_read_line() const
+{
+    if (m_eof && !m_buffered_data.is_empty())
+        return true;
+    if (m_buffered_data.contains_slow('\n'))
+        return true;
+    if (!can_read_from_fd())
+        return false;
+    populate_read_buffer();
+    if (m_eof && !m_buffered_data.is_empty())
+        return true;
+    return m_buffered_data.contains_slow('\n');
+}
+
+bool IODevice::can_read() const
+{
+    return !m_buffered_data.is_empty() || can_read_from_fd();
+}
+
+ByteBuffer IODevice::read_all()
+{
+    off_t file_size = 0;
+    struct stat st;
+    int rc = fstat(fd(), &st);
+    if (rc == 0)
+        file_size = st.st_size;
+
+    Vector<u8> data;
+    data.ensure_capacity(file_size);
+
+    if (!m_buffered_data.is_empty()) {
+        data.append(m_buffered_data.data(), m_buffered_data.size());
+        m_buffered_data.clear();
+    }
+
+    while (true) {
+        char read_buffer[4096];
+        int nread = ::read(m_fd, read_buffer, sizeof(read_buffer));
+        if (nread < 0) {
+            set_error(errno);
+            break;
+        }
+        if (nread == 0) {
+            set_eof(true);
+            break;
+        }
+        data.append((const u8*)read_buffer, nread);
+    }
+    if (data.is_empty())
+        return {};
+    return ByteBuffer::copy(data.data(), data.size());
+}
+
+String IODevice::read_line(size_t max_size)
+{
+    if (m_fd < 0)
+        return {};
+    if (!max_size)
+        return {};
+    if (!can_read_line())
+        return {};
+    if (m_eof) {
+        if (m_buffered_data.size() > max_size) {
+            dbgprintf("IODevice::read_line: At EOF but there's more than max_size(%zu) buffered\n", max_size);
+            return {};
+        }
+        auto line = String((const char*)m_buffered_data.data(), m_buffered_data.size(), Chomp);
+        m_buffered_data.clear();
+        return line;
+    }
+    auto line = ByteBuffer::create_uninitialized(max_size + 1);
+    size_t line_index = 0;
+    while (line_index < max_size) {
+        u8 ch = m_buffered_data[line_index];
+        line[line_index++] = ch;
+        if (ch == '\n') {
+            Vector<u8> new_buffered_data;
+            new_buffered_data.append(m_buffered_data.data() + line_index, m_buffered_data.size() - line_index);
+            m_buffered_data = move(new_buffered_data);
+            line.trim(line_index);
+            return String::copy(line, Chomp);
+        }
+    }
+    return {};
+}
+
+bool IODevice::populate_read_buffer() const
+{
+    if (m_fd < 0)
+        return false;
+    u8 buffer[1024];
+    int nread = ::read(m_fd, buffer, sizeof(buffer));
+    if (nread < 0) {
+        set_error(errno);
+        return false;
+    }
+    if (nread == 0) {
+        set_eof(true);
+        return false;
+    }
+    m_buffered_data.append(buffer, nread);
+    return true;
+}
+
+bool IODevice::close()
+{
+    if (fd() < 0 || mode() == NotOpen)
+        return false;
+    int rc = ::close(fd());
+    if (rc < 0) {
+        set_error(errno);
+        return false;
+    }
+    set_fd(-1);
+    set_mode(IODevice::NotOpen);
+    return true;
+}
+
+bool IODevice::seek(i64 offset, SeekMode mode, off_t* pos)
+{
+    int m = SEEK_SET;
+    switch (mode) {
+    case SeekMode::SetPosition:
+        m = SEEK_SET;
+        break;
+    case SeekMode::FromCurrentPosition:
+        m = SEEK_CUR;
+        break;
+    case SeekMode::FromEndPosition:
+        m = SEEK_END;
+        break;
+    }
+    off_t rc = lseek(m_fd, offset, m);
+    if (rc < 0) {
+        set_error(errno);
+        if (pos)
+            *pos = -1;
+        return false;
+    }
+    m_buffered_data.clear();
+    m_eof = false;
+    if (pos)
+        *pos = rc;
+    return true;
+}
+
+bool IODevice::truncate(off_t size)
+{
+    int rc = ftruncate(m_fd, size);
+    if (rc < 0) {
+        set_error(errno);
+        return false;
+    }
+    return true;
+}
+
+bool IODevice::write(const u8* data, int size)
+{
+    int rc = ::write(m_fd, data, size);
+    if (rc < 0) {
+        perror("IODevice::write: write");
+        set_error(errno);
+        return false;
+    }
+    return rc == size;
+}
+
+int IODevice::printf(const char* format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+    // FIXME: We're not propagating write() failures to client here!
+    int ret = printf_internal([this](char*&, char ch) {
+        write((const u8*)&ch, 1);
+    },
+        nullptr, format, ap);
+    va_end(ap);
+    return ret;
+}
+
+void IODevice::set_fd(int fd)
+{
+    if (m_fd == fd)
+        return;
+
+    m_fd = fd;
+    did_update_fd(fd);
+}
+
+bool IODevice::write(const StringView& v)
+{
+    return write((const u8*)v.characters_without_null_termination(), v.length());
+}
+
+LineIterator::LineIterator(IODevice& device, bool is_end)
+    : m_device(device)
+    , m_is_end(is_end)
+{
+    ++*this;
+}
+
+bool LineIterator::at_end() const
+{
+    return m_device->eof();
+}
+
+LineIterator& LineIterator::operator++()
+{
+    m_buffer = m_device->read_line();
+    return *this;
+}
+
+}

Userland/Libraries/LibCore/IODevice.h

@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <LibCore/Object.h>
+
+namespace Core {
+
+// This is not necessarily a valid iterator in all contexts,
+// if we had concepts, this would be InputIterator, not Copyable, Movable.
+class LineIterator {
+    AK_MAKE_NONCOPYABLE(LineIterator);
+
+public:
+    explicit LineIterator(IODevice&, bool is_end = false);
+
+    bool operator==(const LineIterator& other) const { return &other == this || (at_end() && other.is_end()) || (other.at_end() && is_end()); }
+    bool is_end() const { return m_is_end; }
+    bool at_end() const;
+
+    LineIterator& operator++();
+
+    StringView operator*() const { return m_buffer; }
+
+private:
+    NonnullRefPtr<IODevice> m_device;
+    bool m_is_end { false };
+    String m_buffer;
+};
+
+class IODevice : public Object {
+    C_OBJECT_ABSTRACT(IODevice)
+public:
+    enum OpenMode {
+        NotOpen = 0,
+        ReadOnly = 1,
+        WriteOnly = 2,
+        ReadWrite = 3,
+        Append = 4,
+        Truncate = 8,
+        MustBeNew = 16,
+    };
+
+    virtual ~IODevice() override;
+
+    int fd() const { return m_fd; }
+    unsigned mode() const { return m_mode; }
+    bool is_open() const { return m_mode != NotOpen; }
+    bool eof() const { return m_eof; }
+
+    int error() const { return m_error; }
+    const char* error_string() const;
+
+    bool has_error() const { return m_error != 0; }
+
+    int read(u8* buffer, int length);
+
+    ByteBuffer read(size_t max_size);
+    ByteBuffer read_all();
+    String read_line(size_t max_size = 16384);
+
+    bool write(const u8*, int size);
+    bool write(const StringView&);
+
+    bool truncate(off_t);
+
+    bool can_read_line() const;
+
+    bool can_read() const;
+
+    enum class SeekMode {
+        SetPosition,
+        FromCurrentPosition,
+        FromEndPosition,
+    };
+
+    bool seek(i64, SeekMode = SeekMode::SetPosition, off_t* = nullptr);
+
+    virtual bool open(IODevice::OpenMode) = 0;
+    virtual bool close();
+
+    int printf(const char*, ...);
+
+    LineIterator line_begin() & { return LineIterator(*this); }
+    LineIterator line_end() { return LineIterator(*this, true); }
+
+protected:
+    explicit IODevice(Object* parent = nullptr);
+
+    void set_fd(int);
+    void set_mode(OpenMode mode) { m_mode = mode; }
+    void set_error(int error) const { m_error = error; }
+    void set_eof(bool eof) const { m_eof = eof; }
+
+    virtual void did_update_fd(int) { }
+
+private:
+    bool populate_read_buffer() const;
+    bool can_read_from_fd() const;
+
+    int m_fd { -1 };
+    OpenMode m_mode { NotOpen };
+    mutable int m_error { 0 };
+    mutable bool m_eof { false };
+    mutable Vector<u8> m_buffered_data;
+};
+
+}

Userland/Libraries/LibCore/IODeviceStreamReader.h

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/StdLibExtras.h>
+#include <LibCore/IODevice.h>
+
+namespace Core {
+
+class IODeviceStreamReader {
+public:
+    IODeviceStreamReader(IODevice& device)
+        : m_device(device)
+    {
+    }
+
+    bool handle_read_failure()
+    {
+        return exchange(m_had_failure, false);
+    }
+
+    template<typename T>
+    IODeviceStreamReader& operator>>(T& value)
+    {
+        int nread = m_device.read((u8*)&value, sizeof(T));
+        ASSERT(nread == sizeof(T));
+        if (nread != sizeof(T))
+            m_had_failure = true;
+        return *this;
+    }
+
+private:
+    IODevice& m_device;
+    bool m_had_failure { false };
+};
+
+}

Userland/Libraries/LibCore/LocalServer.cpp

@@ -0,0 +1,161 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/LocalServer.h>
+#include <LibCore/LocalSocket.h>
+#include <LibCore/Notifier.h>
+#include <stdio.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#ifndef SOCK_NONBLOCK
+#    include <sys/ioctl.h>
+#endif
+
+namespace Core {
+
+LocalServer::LocalServer(Object* parent)
+    : Object(parent)
+{
+}
+
+LocalServer::~LocalServer()
+{
+    if (m_fd >= 0)
+        ::close(m_fd);
+}
+
+bool LocalServer::take_over_from_system_server()
+{
+    if (m_listening)
+        return false;
+
+    constexpr auto socket_takeover = "SOCKET_TAKEOVER";
+
+    if (getenv(socket_takeover)) {
+        // Sanity check: it has to be a socket.
+        struct stat stat;
+        int rc = fstat(3, &stat);
+        if (rc == 0 && S_ISSOCK(stat.st_mode)) {
+            // The SystemServer has passed us the socket as fd 3,
+            // so use that instead of creating our own.
+            m_fd = 3;
+            // It had to be !CLOEXEC for obvious reasons, but we
+            // don't need it to be !CLOEXEC anymore, so set the
+            // CLOEXEC flag now.
+            fcntl(m_fd, F_SETFD, FD_CLOEXEC);
+            // We wouldn't want our children to think we're passing
+            // them a socket either, so unset the env variable.
+            unsetenv(socket_takeover);
+
+            m_listening = true;
+            setup_notifier();
+            return true;
+        } else {
+            if (rc != 0)
+                perror("fstat");
+            dbgln("It's not a socket, what the heck??");
+        }
+    }
+
+    dbgln("Failed to take the socket over from SystemServer");
+
+    return false;
+}
+
+void LocalServer::setup_notifier()
+{
+    m_notifier = Notifier::construct(m_fd, Notifier::Event::Read, this);
+    m_notifier->on_ready_to_read = [this] {
+        if (on_ready_to_accept)
+            on_ready_to_accept();
+    };
+}
+
+bool LocalServer::listen(const String& address)
+{
+    if (m_listening)
+        return false;
+
+    int rc;
+
+#ifdef SOCK_NONBLOCK
+    m_fd = socket(AF_LOCAL, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
+#else
+    m_fd = socket(AF_LOCAL, SOCK_STREAM, 0);
+    int option = 1;
+    ioctl(m_fd, FIONBIO, &option);
+    fcntl(m_fd, F_SETFD, FD_CLOEXEC);
+#endif
+    ASSERT(m_fd >= 0);
+#ifndef __APPLE__
+    rc = fchmod(m_fd, 0600);
+    if (rc < 0) {
+        perror("fchmod");
+        ASSERT_NOT_REACHED();
+    }
+#endif
+
+    auto socket_address = SocketAddress::local(address);
+    auto un_optional = socket_address.to_sockaddr_un();
+    if (!un_optional.has_value()) {
+        perror("bind");
+        return false;
+    }
+    auto un = un_optional.value();
+    rc = ::bind(m_fd, (const sockaddr*)&un, sizeof(un));
+    if (rc < 0) {
+        perror("bind");
+        return false;
+    }
+
+    rc = ::listen(m_fd, 5);
+    if (rc < 0) {
+        perror("listen");
+        return false;
+    }
+
+    m_listening = true;
+    setup_notifier();
+    return true;
+}
+
+RefPtr<LocalSocket> LocalServer::accept()
+{
+    ASSERT(m_listening);
+    sockaddr_un un;
+    socklen_t un_size = sizeof(un);
+    int accepted_fd = ::accept(m_fd, (sockaddr*)&un, &un_size);
+    if (accepted_fd < 0) {
+        perror("accept");
+        return nullptr;
+    }
+
+    return LocalSocket::construct(accepted_fd);
+}
+
+}

Userland/Libraries/LibCore/LocalServer.h

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibCore/Notifier.h>
+#include <LibCore/Object.h>
+
+namespace Core {
+
+class LocalServer : public Object {
+    C_OBJECT(LocalServer)
+public:
+    virtual ~LocalServer() override;
+
+    bool take_over_from_system_server();
+    bool is_listening() const { return m_listening; }
+    bool listen(const String& address);
+
+    RefPtr<LocalSocket> accept();
+
+    Function<void()> on_ready_to_accept;
+
+private:
+    explicit LocalServer(Object* parent = nullptr);
+
+    void setup_notifier();
+
+    int m_fd { -1 };
+    bool m_listening { false };
+    RefPtr<Notifier> m_notifier;
+};
+
+}

Userland/Libraries/LibCore/LocalSocket.cpp

@@ -0,0 +1,107 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/LocalSocket.h>
+#include <errno.h>
+#include <stdio.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+
+#ifndef SOCK_NONBLOCK
+#    include <sys/ioctl.h>
+#endif
+
+namespace Core {
+
+LocalSocket::LocalSocket(int fd, Object* parent)
+    : Socket(Socket::Type::Local, parent)
+{
+    // NOTE: This constructor is used by LocalServer::accept(), so the socket is already connected.
+    m_connected = true;
+    set_fd(fd);
+    set_mode(IODevice::ReadWrite);
+    set_error(0);
+}
+
+LocalSocket::LocalSocket(Object* parent)
+    : Socket(Socket::Type::Local, parent)
+{
+
+#ifdef SOCK_NONBLOCK
+    int fd = socket(AF_LOCAL, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
+#else
+    int fd = socket(AF_LOCAL, SOCK_STREAM, 0);
+    int option = 1;
+    ioctl(fd, FIONBIO, &option);
+    fcntl(fd, F_SETFD, FD_CLOEXEC);
+#endif
+
+    if (fd < 0) {
+        set_error(errno);
+    } else {
+        set_fd(fd);
+        set_mode(IODevice::ReadWrite);
+        set_error(0);
+    }
+}
+
+LocalSocket::~LocalSocket()
+{
+}
+
+RefPtr<LocalSocket> LocalSocket::take_over_accepted_socket_from_system_server()
+{
+    constexpr auto socket_takeover = "SOCKET_TAKEOVER";
+    if (!getenv(socket_takeover))
+        return nullptr;
+
+    // The SystemServer has passed us the socket as fd 3,
+    // so use that instead of creating our own.
+    constexpr int fd = 3;
+
+    // Sanity check: it has to be a socket.
+    struct stat stat;
+    int rc = fstat(fd, &stat);
+    if (rc < 0 || !S_ISSOCK(stat.st_mode)) {
+        if (rc != 0)
+            perror("fstat");
+        dbgln("ERROR: The fd we got from SystemServer is not a socket");
+        return nullptr;
+    }
+
+    auto socket = LocalSocket::construct(fd);
+
+    // It had to be !CLOEXEC for obvious reasons, but we
+    // don't need it to be !CLOEXEC anymore, so set the
+    // CLOEXEC flag now.
+    fcntl(fd, F_SETFD, FD_CLOEXEC);
+    // We wouldn't want our children to think we're passing
+    // them a socket either, so unset the env variable.
+    unsetenv(socket_takeover);
+    return socket;
+}
+
+}

Userland/Libraries/LibCore/LocalSocket.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibCore/Socket.h>
+
+namespace Core {
+
+class LocalSocket final : public Socket {
+    C_OBJECT(LocalSocket)
+public:
+    virtual ~LocalSocket() override;
+
+    static RefPtr<LocalSocket> take_over_accepted_socket_from_system_server();
+
+private:
+    explicit LocalSocket(Object* parent = nullptr);
+    LocalSocket(int fd, Object* parent = nullptr);
+};
+
+}

Userland/Libraries/LibCore/MimeData.cpp

@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/StringBuilder.h>
+#include <LibCore/MimeData.h>
+
+namespace Core {
+
+Vector<String> MimeData::formats() const
+{
+    Vector<String> mime_types;
+    mime_types.ensure_capacity(m_data.size());
+    for (auto it : m_data)
+        mime_types.unchecked_append(it.key);
+    return mime_types;
+}
+
+Vector<URL> MimeData::urls() const
+{
+    auto it = m_data.find("text/uri-list");
+    if (it == m_data.end())
+        return {};
+    Vector<URL> urls;
+    for (auto& line : StringView(it->value).split_view('\n')) {
+        urls.append(URL(line));
+    }
+    return urls;
+}
+
+void MimeData::set_urls(const Vector<URL>& urls)
+{
+    StringBuilder builder;
+    for (auto& url : urls) {
+        builder.append(url.to_string());
+        builder.append('\n');
+    }
+    set_data("text/uri-list", builder.to_byte_buffer());
+}
+
+String MimeData::text() const
+{
+    return String::copy(m_data.get("text/plain").value_or({}));
+}
+
+void MimeData::set_text(const String& text)
+{
+    set_data("text/plain", text.to_byte_buffer());
+}
+
+String guess_mime_type_based_on_filename(const StringView& path)
+{
+    if (path.ends_with(".pbm", CaseSensitivity::CaseInsensitive))
+        return "image/x‑portable‑bitmap";
+    if (path.ends_with(".pgm", CaseSensitivity::CaseInsensitive))
+        return "image/x‑portable‑graymap";
+    if (path.ends_with(".png", CaseSensitivity::CaseInsensitive))
+        return "image/png";
+    if (path.ends_with(".ppm", CaseSensitivity::CaseInsensitive))
+        return "image/x‑portable‑pixmap";
+    if (path.ends_with(".gif", CaseSensitivity::CaseInsensitive))
+        return "image/gif";
+    if (path.ends_with(".bmp", CaseSensitivity::CaseInsensitive))
+        return "image/bmp";
+    if (path.ends_with(".jpg", CaseSensitivity::CaseInsensitive) || path.ends_with(".jpeg", CaseSensitivity::CaseInsensitive))
+        return "image/jpeg";
+    if (path.ends_with(".svg", CaseSensitivity::CaseInsensitive))
+        return "image/svg+xml";
+    if (path.ends_with(".md", CaseSensitivity::CaseInsensitive))
+        return "text/markdown";
+    if (path.ends_with(".html", CaseSensitivity::CaseInsensitive) || path.ends_with(".htm", CaseSensitivity::CaseInsensitive))
+        return "text/html";
+    if (path.ends_with("/", CaseSensitivity::CaseInsensitive))
+        return "text/html";
+    if (path.ends_with(".csv", CaseSensitivity::CaseInsensitive))
+        return "text/csv";
+    return "text/plain";
+}
+
+}

Userland/Libraries/LibCore/MimeData.h

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/ByteBuffer.h>
+#include <AK/HashMap.h>
+#include <AK/URL.h>
+#include <LibCore/Object.h>
+
+namespace Core {
+
+class MimeData : public Object {
+    C_OBJECT(MimeData);
+
+public:
+    virtual ~MimeData() { }
+
+    ByteBuffer data(const String& mime_type) const { return m_data.get(mime_type).value_or({}); }
+    void set_data(const String& mime_type, const ByteBuffer& data) { m_data.set(mime_type, data); }
+
+    bool has_format(const String& mime_type) const { return m_data.contains(mime_type); }
+    Vector<String> formats() const;
+
+    // Convenience helpers for "text/plain"
+    bool has_text() const { return has_format("text/plain"); }
+    String text() const;
+    void set_text(const String&);
+
+    // Convenience helpers for "text/uri-list"
+    bool has_urls() const { return has_format("text/uri-list"); }
+    Vector<URL> urls() const;
+    void set_urls(const Vector<URL>&);
+
+    const HashMap<String, ByteBuffer>& all_data() const { return m_data; }
+
+private:
+    MimeData() { }
+    explicit MimeData(const HashMap<String, ByteBuffer>& data)
+        : m_data(data)
+    {
+    }
+
+    HashMap<String, ByteBuffer> m_data;
+};
+
+String guess_mime_type_based_on_filename(const StringView&);
+
+}

Userland/Libraries/LibCore/NetworkJob.cpp

@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/NetworkJob.h>
+#include <LibCore/NetworkResponse.h>
+#include <stdio.h>
+
+//#define CNETWORKJOB_DEBUG
+
+namespace Core {
+
+NetworkJob::NetworkJob(OutputStream& output_stream)
+    : m_output_stream(output_stream)
+{
+}
+
+NetworkJob::~NetworkJob()
+{
+}
+
+void NetworkJob::start()
+{
+}
+
+void NetworkJob::shutdown()
+{
+}
+
+void NetworkJob::did_finish(NonnullRefPtr<NetworkResponse>&& response)
+{
+    // NOTE: We protect ourselves here, since the on_finish callback may otherwise
+    //       trigger destruction of this job somehow.
+    NonnullRefPtr<NetworkJob> protector(*this);
+
+    m_response = move(response);
+#ifdef CNETWORKJOB_DEBUG
+    dbg() << *this << " job did_finish!";
+#endif
+    ASSERT(on_finish);
+    on_finish(true);
+    shutdown();
+}
+
+void NetworkJob::did_fail(Error error)
+{
+    // NOTE: We protect ourselves here, since the on_finish callback may otherwise
+    //       trigger destruction of this job somehow.
+    NonnullRefPtr<NetworkJob> protector(*this);
+
+    m_error = error;
+#ifdef CNETWORKJOB_DEBUG
+    dbgprintf("%s{%p} job did_fail! error: %u (%s)\n", class_name(), this, (unsigned)error, to_string(error));
+#endif
+    ASSERT(on_finish);
+    on_finish(false);
+    shutdown();
+}
+
+void NetworkJob::did_progress(Optional<u32> total_size, u32 downloaded)
+{
+    // NOTE: We protect ourselves here, since the callback may otherwise
+    //       trigger destruction of this job somehow.
+    NonnullRefPtr<NetworkJob> protector(*this);
+
+    if (on_progress)
+        on_progress(total_size, downloaded);
+}
+
+const char* to_string(NetworkJob::Error error)
+{
+    switch (error) {
+    case NetworkJob::Error::ProtocolFailed:
+        return "ProtocolFailed";
+    case NetworkJob::Error::ConnectionFailed:
+        return "ConnectionFailed";
+    case NetworkJob::Error::TransmissionFailed:
+        return "TransmissionFailed";
+    case NetworkJob::Error::Cancelled:
+        return "Cancelled";
+    default:
+        return "(Unknown error)";
+    }
+}
+
+}

Userland/Libraries/LibCore/NetworkJob.h

@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/Stream.h>
+#include <LibCore/Object.h>
+
+namespace Core {
+
+class NetworkJob : public Object {
+    C_OBJECT_ABSTRACT(NetworkJob)
+public:
+    enum class Error {
+        None,
+        ConnectionFailed,
+        TransmissionFailed,
+        ProtocolFailed,
+        Cancelled,
+    };
+    virtual ~NetworkJob() override;
+
+    // Could fire twice, after Headers and after Trailers!
+    Function<void(const HashMap<String, String, CaseInsensitiveStringTraits>& response_headers, Optional<u32> response_code)> on_headers_received;
+    Function<void(bool success)> on_finish;
+    Function<void(Optional<u32>, u32)> on_progress;
+
+    bool is_cancelled() const { return m_error == Error::Cancelled; }
+    bool has_error() const { return m_error != Error::None; }
+    Error error() const { return m_error; }
+    NetworkResponse* response() { return m_response.ptr(); }
+    const NetworkResponse* response() const { return m_response.ptr(); }
+
+    virtual void start() = 0;
+    virtual void shutdown() = 0;
+
+    void cancel()
+    {
+        shutdown();
+        m_error = Error::Cancelled;
+    }
+
+protected:
+    NetworkJob(OutputStream&);
+    void did_finish(NonnullRefPtr<NetworkResponse>&&);
+    void did_fail(Error);
+    void did_progress(Optional<u32> total_size, u32 downloaded);
+
+    size_t do_write(ReadonlyBytes bytes) { return m_output_stream.write(bytes); }
+
+private:
+    RefPtr<NetworkResponse> m_response;
+    OutputStream& m_output_stream;
+    Error m_error { Error::None };
+};
+
+const char* to_string(NetworkJob::Error);
+
+}

Userland/Libraries/LibCore/NetworkResponse.cpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/NetworkResponse.h>
+
+namespace Core {
+
+NetworkResponse::NetworkResponse()
+{
+}
+
+NetworkResponse::~NetworkResponse()
+{
+}
+
+}

Userland/Libraries/LibCore/NetworkResponse.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/ByteBuffer.h>
+#include <AK/RefCounted.h>
+
+namespace Core {
+
+class NetworkResponse : public RefCounted<NetworkResponse> {
+public:
+    virtual ~NetworkResponse();
+
+    bool is_error() const { return m_error; }
+
+protected:
+    explicit NetworkResponse();
+
+    bool m_error { false };
+};
+
+}

Userland/Libraries/LibCore/Notifier.cpp

@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Badge.h>
+#include <LibCore/Event.h>
+#include <LibCore/EventLoop.h>
+#include <LibCore/Notifier.h>
+
+namespace Core {
+
+Notifier::Notifier(int fd, unsigned event_mask, Object* parent)
+    : Object(parent)
+    , m_fd(fd)
+    , m_event_mask(event_mask)
+{
+    set_enabled(true);
+}
+
+Notifier::~Notifier()
+{
+    set_enabled(false);
+}
+
+void Notifier::set_enabled(bool enabled)
+{
+    if (m_fd < 0)
+        return;
+    if (enabled)
+        Core::EventLoop::register_notifier({}, *this);
+    else
+        Core::EventLoop::unregister_notifier({}, *this);
+}
+
+void Notifier::close()
+{
+    if (m_fd < 0)
+        return;
+    set_enabled(false);
+    m_fd = -1;
+}
+
+void Notifier::event(Core::Event& event)
+{
+    if (event.type() == Core::Event::NotifierRead && on_ready_to_read) {
+        on_ready_to_read();
+    } else if (event.type() == Core::Event::NotifierWrite && on_ready_to_write) {
+        on_ready_to_write();
+    } else {
+        Object::event(event);
+    }
+}
+
+}

Userland/Libraries/LibCore/Notifier.h

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <LibCore/Object.h>
+
+namespace Core {
+
+class Notifier : public Object {
+    C_OBJECT(Notifier)
+public:
+    enum Event {
+        None = 0,
+        Read = 1,
+        Write = 2,
+        Exceptional = 4,
+    };
+
+    virtual ~Notifier() override;
+
+    void set_enabled(bool);
+
+    Function<void()> on_ready_to_read;
+    Function<void()> on_ready_to_write;
+
+    void close();
+
+    int fd() const { return m_fd; }
+    unsigned event_mask() const { return m_event_mask; }
+    void set_event_mask(unsigned event_mask) { m_event_mask = event_mask; }
+
+    void event(Core::Event&) override;
+
+private:
+    Notifier(int fd, unsigned event_mask, Object* parent = nullptr);
+
+    int m_fd { -1 };
+    unsigned m_event_mask { 0 };
+};
+
+}

Userland/Libraries/LibCore/Object.cpp

@@ -0,0 +1,270 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Assertions.h>
+#include <AK/Badge.h>
+#include <AK/JsonObject.h>
+#include <LibCore/Event.h>
+#include <LibCore/EventLoop.h>
+#include <LibCore/Object.h>
+#include <stdio.h>
+
+namespace Core {
+
+IntrusiveList<Object, &Object::m_all_objects_list_node>& Object::all_objects()
+{
+    static IntrusiveList<Object, &Object::m_all_objects_list_node> objects;
+    return objects;
+}
+
+Object::Object(Object* parent)
+    : m_parent(parent)
+{
+    all_objects().append(*this);
+    if (m_parent)
+        m_parent->add_child(*this);
+
+    REGISTER_READONLY_STRING_PROPERTY("class_name", class_name);
+    REGISTER_STRING_PROPERTY("name", name, set_name);
+
+    register_property(
+        "address", [this] { return FlatPtr(this); },
+        [](auto&) { return false; });
+
+    register_property(
+        "parent", [this] { return FlatPtr(this->parent()); },
+        [](auto&) { return false; });
+}
+
+Object::~Object()
+{
+    // NOTE: We move our children out to a stack vector to prevent other
+    //       code from trying to iterate over them.
+    auto children = move(m_children);
+    // NOTE: We also unparent the children, so that they won't try to unparent
+    //       themselves in their own destructors.
+    for (auto& child : children)
+        child.m_parent = nullptr;
+
+    all_objects().remove(*this);
+    stop_timer();
+    if (m_parent)
+        m_parent->remove_child(*this);
+}
+
+void Object::event(Core::Event& event)
+{
+    switch (event.type()) {
+    case Core::Event::Timer:
+        return timer_event(static_cast<TimerEvent&>(event));
+    case Core::Event::ChildAdded:
+    case Core::Event::ChildRemoved:
+        return child_event(static_cast<ChildEvent&>(event));
+    case Core::Event::Invalid:
+        ASSERT_NOT_REACHED();
+        break;
+    case Core::Event::Custom:
+        return custom_event(static_cast<CustomEvent&>(event));
+    default:
+        break;
+    }
+}
+
+void Object::add_child(Object& object)
+{
+    // FIXME: Should we support reparenting objects?
+    ASSERT(!object.parent() || object.parent() == this);
+    object.m_parent = this;
+    m_children.append(object);
+    Core::ChildEvent child_event(Core::Event::ChildAdded, object);
+    event(child_event);
+}
+
+void Object::insert_child_before(Object& new_child, Object& before_child)
+{
+    // FIXME: Should we support reparenting objects?
+    ASSERT(!new_child.parent() || new_child.parent() == this);
+    new_child.m_parent = this;
+    m_children.insert_before_matching(new_child, [&](auto& existing_child) { return existing_child.ptr() == &before_child; });
+    Core::ChildEvent child_event(Core::Event::ChildAdded, new_child, &before_child);
+    event(child_event);
+}
+
+void Object::remove_child(Object& object)
+{
+    for (size_t i = 0; i < m_children.size(); ++i) {
+        if (m_children.ptr_at(i).ptr() == &object) {
+            // NOTE: We protect the child so it survives the handling of ChildRemoved.
+            NonnullRefPtr<Object> protector = object;
+            object.m_parent = nullptr;
+            m_children.remove(i);
+            Core::ChildEvent child_event(Core::Event::ChildRemoved, object);
+            event(child_event);
+            return;
+        }
+    }
+    ASSERT_NOT_REACHED();
+}
+
+void Object::remove_all_children()
+{
+    while (!m_children.is_empty())
+        m_children.first().remove_from_parent();
+}
+
+void Object::timer_event(Core::TimerEvent&)
+{
+}
+
+void Object::child_event(Core::ChildEvent&)
+{
+}
+
+void Object::custom_event(CustomEvent&)
+{
+}
+
+void Object::start_timer(int ms, TimerShouldFireWhenNotVisible fire_when_not_visible)
+{
+    if (m_timer_id) {
+        dbgln("{} {:p} already has a timer!", class_name(), this);
+        ASSERT_NOT_REACHED();
+    }
+
+    m_timer_id = Core::EventLoop::register_timer(*this, ms, true, fire_when_not_visible);
+}
+
+void Object::stop_timer()
+{
+    if (!m_timer_id)
+        return;
+    bool success = Core::EventLoop::unregister_timer(m_timer_id);
+    ASSERT(success);
+    m_timer_id = 0;
+}
+
+void Object::dump_tree(int indent)
+{
+    for (int i = 0; i < indent; ++i) {
+        printf(" ");
+    }
+    printf("%s{%p}", class_name(), this);
+    if (!name().is_null())
+        printf(" %s", name().characters());
+    printf("\n");
+
+    for_each_child([&](auto& child) {
+        child.dump_tree(indent + 2);
+        return IterationDecision::Continue;
+    });
+}
+
+void Object::deferred_invoke(Function<void(Object&)> invokee)
+{
+    Core::EventLoop::current().post_event(*this, make<Core::DeferredInvocationEvent>(move(invokee)));
+}
+
+void Object::save_to(JsonObject& json)
+{
+    for (auto& it : m_properties) {
+        auto& property = it.value;
+        json.set(property->name(), property->get());
+    }
+}
+
+JsonValue Object::property(const StringView& name) const
+{
+    auto it = m_properties.find(name);
+    if (it == m_properties.end())
+        return JsonValue();
+    return it->value->get();
+}
+
+bool Object::set_property(const StringView& name, const JsonValue& value)
+{
+    auto it = m_properties.find(name);
+    if (it == m_properties.end())
+        return false;
+    return it->value->set(value);
+}
+
+bool Object::is_ancestor_of(const Object& other) const
+{
+    if (&other == this)
+        return false;
+    for (auto* ancestor = other.parent(); ancestor; ancestor = ancestor->parent()) {
+        if (ancestor == this)
+            return true;
+    }
+    return false;
+}
+
+void Object::dispatch_event(Core::Event& e, Object* stay_within)
+{
+    ASSERT(!stay_within || stay_within == this || stay_within->is_ancestor_of(*this));
+    auto* target = this;
+    do {
+        target->event(e);
+        target = target->parent();
+        if (target == stay_within) {
+            // Prevent the event from bubbling any further.
+            return;
+        }
+    } while (target && !e.is_accepted());
+}
+
+bool Object::is_visible_for_timer_purposes() const
+{
+    if (parent())
+        return parent()->is_visible_for_timer_purposes();
+    return true;
+}
+
+void Object::increment_inspector_count(Badge<RPCClient>)
+{
+    ++m_inspector_count;
+    if (m_inspector_count == 1)
+        did_begin_inspection();
+}
+
+void Object::decrement_inspector_count(Badge<RPCClient>)
+{
+    --m_inspector_count;
+    if (!m_inspector_count)
+        did_end_inspection();
+}
+
+void Object::register_property(const String& name, Function<JsonValue()> getter, Function<bool(const JsonValue&)> setter)
+{
+    m_properties.set(name, make<Property>(name, move(getter), move(setter)));
+}
+
+const LogStream& operator<<(const LogStream& stream, const Object& object)
+{
+    return stream << object.class_name() << '{' << &object << '}';
+}
+
+}

Userland/Libraries/LibCore/Object.h

@@ -0,0 +1,346 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <AK/HashMap.h>
+#include <AK/IntrusiveList.h>
+#include <AK/Noncopyable.h>
+#include <AK/NonnullRefPtrVector.h>
+#include <AK/String.h>
+#include <AK/TypeCasts.h>
+#include <AK/Weakable.h>
+#include <LibCore/Forward.h>
+#include <LibCore/Property.h>
+
+namespace Core {
+
+class RPCClient;
+
+enum class TimerShouldFireWhenNotVisible {
+    No = 0,
+    Yes
+};
+
+#define C_OBJECT(klass)                                                \
+public:                                                                \
+    virtual const char* class_name() const override { return #klass; } \
+    template<class... Args>                                            \
+    static inline NonnullRefPtr<klass> construct(Args&&... args)       \
+    {                                                                  \
+        return adopt(*new klass(forward<Args>(args)...));              \
+    }
+
+#define C_OBJECT_ABSTRACT(klass) \
+public:                          \
+    virtual const char* class_name() const override { return #klass; }
+
+class Object
+    : public RefCounted<Object>
+    , public Weakable<Object> {
+    // NOTE: No C_OBJECT macro for Core::Object itself.
+
+    AK_MAKE_NONCOPYABLE(Object);
+    AK_MAKE_NONMOVABLE(Object);
+
+    IntrusiveListNode m_all_objects_list_node;
+
+public:
+    virtual ~Object();
+
+    virtual const char* class_name() const = 0;
+    virtual void event(Core::Event&);
+
+    const String& name() const { return m_name; }
+    void set_name(const StringView& name) { m_name = name; }
+
+    NonnullRefPtrVector<Object>& children() { return m_children; }
+    const NonnullRefPtrVector<Object>& children() const { return m_children; }
+
+    template<typename Callback>
+    void for_each_child(Callback callback)
+    {
+        for (auto& child : m_children) {
+            if (callback(child) == IterationDecision::Break)
+                return;
+        }
+    }
+
+    template<typename T, typename Callback>
+    void for_each_child_of_type(Callback callback) requires IsBaseOf<Object, T>::value;
+
+    template<typename T>
+    T* find_child_of_type_named(const String&) requires IsBaseOf<Object, T>::value;
+
+    template<typename T>
+    T* find_descendant_of_type_named(const String&) requires IsBaseOf<Object, T>::value;
+
+    bool is_ancestor_of(const Object&) const;
+
+    Object* parent() { return m_parent; }
+    const Object* parent() const { return m_parent; }
+
+    void start_timer(int ms, TimerShouldFireWhenNotVisible = TimerShouldFireWhenNotVisible::No);
+    void stop_timer();
+    bool has_timer() const { return m_timer_id; }
+
+    void add_child(Object&);
+    void insert_child_before(Object& new_child, Object& before_child);
+    void remove_child(Object&);
+    void remove_all_children();
+
+    void dump_tree(int indent = 0);
+
+    void deferred_invoke(Function<void(Object&)>);
+
+    void save_to(AK::JsonObject&);
+
+    bool set_property(const StringView& name, const JsonValue& value);
+    JsonValue property(const StringView& name) const;
+    const HashMap<String, NonnullOwnPtr<Property>>& properties() const { return m_properties; }
+
+    static IntrusiveList<Object, &Object::m_all_objects_list_node>& all_objects();
+
+    void dispatch_event(Core::Event&, Object* stay_within = nullptr);
+
+    void remove_from_parent()
+    {
+        if (m_parent)
+            m_parent->remove_child(*this);
+    }
+
+    template<class T, class... Args>
+    inline T& add(Args&&... args)
+    {
+        auto child = T::construct(forward<Args>(args)...);
+        add_child(*child);
+        return child;
+    }
+
+    virtual bool is_visible_for_timer_purposes() const;
+
+    bool is_being_inspected() const { return m_inspector_count; }
+
+    void increment_inspector_count(Badge<RPCClient>);
+    void decrement_inspector_count(Badge<RPCClient>);
+
+protected:
+    explicit Object(Object* parent = nullptr);
+
+    void register_property(const String& name, Function<JsonValue()> getter, Function<bool(const JsonValue&)> setter = nullptr);
+
+    virtual void timer_event(TimerEvent&);
+    virtual void custom_event(CustomEvent&);
+
+    // NOTE: You may get child events for children that are not yet fully constructed!
+    virtual void child_event(ChildEvent&);
+
+    virtual void did_begin_inspection() { }
+    virtual void did_end_inspection() { }
+
+private:
+    Object* m_parent { nullptr };
+    String m_name;
+    int m_timer_id { 0 };
+    unsigned m_inspector_count { 0 };
+    HashMap<String, NonnullOwnPtr<Property>> m_properties;
+    NonnullRefPtrVector<Object> m_children;
+};
+
+}
+
+template<>
+struct AK::Formatter<Core::Object> : AK::Formatter<FormatString> {
+    void format(FormatBuilder& builder, const Core::Object& value)
+    {
+        return AK::Formatter<FormatString>::format(builder, "{}({})", value.class_name(), &value);
+    }
+};
+
+namespace Core {
+template<typename T, typename Callback>
+inline void Object::for_each_child_of_type(Callback callback) requires IsBaseOf<Object, T>::value
+{
+    for_each_child([&](auto& child) {
+        if (auto* child_as_t = dynamic_cast<T*>(&child); child_as_t)
+            return callback(*child_as_t);
+        return IterationDecision::Continue;
+    });
+}
+
+template<typename T>
+T* Object::find_child_of_type_named(const String& name) requires IsBaseOf<Object, T>::value
+{
+    T* found_child = nullptr;
+    for_each_child_of_type<T>([&](auto& child) {
+        if (child.name() == name) {
+            found_child = &child;
+            return IterationDecision::Break;
+        }
+        return IterationDecision::Continue;
+    });
+
+    return found_child;
+}
+
+template<typename T>
+T* Object::find_descendant_of_type_named(const String& name) requires IsBaseOf<Object, T>::value
+{
+    auto* this_as_t = dynamic_cast<T*>(this);
+    if (this_as_t && this->name() == name)
+        return this_as_t;
+    T* found_child = nullptr;
+    for_each_child([&](auto& child) {
+        found_child = child.template find_descendant_of_type_named<T>(name);
+        if (found_child)
+            return IterationDecision::Break;
+        return IterationDecision::Continue;
+    });
+    return found_child;
+}
+
+const LogStream& operator<<(const LogStream&, const Object&);
+
+#define REGISTER_INT_PROPERTY(property_name, getter, setter) \
+    register_property(                                       \
+        property_name,                                       \
+        [this] { return this->getter(); },                   \
+        [this](auto& value) {                                \
+            this->setter(value.template to_number<int>());   \
+            return true;                                     \
+        });
+
+#define REGISTER_BOOL_PROPERTY(property_name, getter, setter) \
+    register_property(                                        \
+        property_name,                                        \
+        [this] { return this->getter(); },                    \
+        [this](auto& value) {                                 \
+            this->setter(value.to_bool());                    \
+            return true;                                      \
+        });
+
+#define REGISTER_STRING_PROPERTY(property_name, getter, setter) \
+    register_property(                                          \
+        property_name,                                          \
+        [this] { return this->getter(); },                      \
+        [this](auto& value) {                                   \
+            this->setter(value.to_string());                    \
+            return true;                                        \
+        });
+
+#define REGISTER_READONLY_STRING_PROPERTY(property_name, getter) \
+    register_property(                                           \
+        property_name,                                           \
+        [this] { return this->getter(); },                       \
+        {});
+
+#define REGISTER_RECT_PROPERTY(property_name, getter, setter)          \
+    register_property(                                                 \
+        property_name,                                                 \
+        [this] {                                                       \
+            auto rect = this->getter();                                \
+            JsonObject rect_object;                                    \
+            rect_object.set("x", rect.x());                            \
+            rect_object.set("y", rect.y());                            \
+            rect_object.set("width", rect.width());                    \
+            rect_object.set("height", rect.height());                  \
+            return rect_object;                                        \
+        },                                                             \
+        [this](auto& value) {                                          \
+            if (!value.is_object())                                    \
+                return false;                                          \
+            Gfx::IntRect rect;                                         \
+            rect.set_x(value.as_object().get("x").to_i32());           \
+            rect.set_y(value.as_object().get("y").to_i32());           \
+            rect.set_width(value.as_object().get("width").to_i32());   \
+            rect.set_height(value.as_object().get("height").to_i32()); \
+            setter(rect);                                              \
+            return true;                                               \
+        });
+
+#define REGISTER_SIZE_PROPERTY(property_name, getter, setter)          \
+    register_property(                                                 \
+        property_name,                                                 \
+        [this] {                                                       \
+            auto size = this->getter();                                \
+            JsonObject size_object;                                    \
+            size_object.set("width", size.width());                    \
+            size_object.set("height", size.height());                  \
+            return size_object;                                        \
+        },                                                             \
+        [this](auto& value) {                                          \
+            if (!value.is_object())                                    \
+                return false;                                          \
+            Gfx::IntSize size;                                         \
+            size.set_width(value.as_object().get("width").to_i32());   \
+            size.set_height(value.as_object().get("height").to_i32()); \
+            setter(size);                                              \
+            return true;                                               \
+        });
+
+#define REGISTER_ENUM_PROPERTY(property_name, getter, setter, EnumType, ...) \
+    register_property(                                                       \
+        property_name,                                                       \
+        [this]() -> JsonValue {                                              \
+            struct {                                                         \
+                EnumType enum_value;                                         \
+                String string_value;                                         \
+            } options[] = { __VA_ARGS__ };                                   \
+            auto enum_value = getter();                                      \
+            for (size_t i = 0; i < array_size(options); ++i) {               \
+                auto& option = options[i];                                   \
+                if (enum_value == option.enum_value)                         \
+                    return option.string_value;                              \
+            }                                                                \
+            return JsonValue();                                              \
+        },                                                                   \
+        [this](auto& value) {                                                \
+            struct {                                                         \
+                EnumType enum_value;                                         \
+                String string_value;                                         \
+            } options[] = { __VA_ARGS__ };                                   \
+            auto string_value = value.as_string();                           \
+            for (size_t i = 0; i < array_size(options); ++i) {               \
+                auto& option = options[i];                                   \
+                if (string_value == option.string_value) {                   \
+                    setter(option.enum_value);                               \
+                    return true;                                             \
+                }                                                            \
+            }                                                                \
+            return false;                                                    \
+        })
+
+#define REGISTER_TEXT_ALIGNMENT_PROPERTY(property_name, getter, setter) \
+    REGISTER_ENUM_PROPERTY(                                             \
+        property_name, getter, setter, Gfx::TextAlignment,              \
+        { Gfx::TextAlignment::TopLeft, "TopLeft" },                     \
+        { Gfx::TextAlignment::CenterLeft, "CenterLeft" },               \
+        { Gfx::TextAlignment::Center, "Center" },                       \
+        { Gfx::TextAlignment::CenterRight, "CenterRight" },             \
+        { Gfx::TextAlignment::TopRight, "TopRight" },                   \
+        { Gfx::TextAlignment::BottomRight, "BottomRight" })
+}

Userland/Libraries/LibCore/ProcessStatisticsReader.cpp

@@ -0,0 +1,142 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/ByteBuffer.h>
+#include <AK/JsonArray.h>
+#include <AK/JsonObject.h>
+#include <AK/JsonValue.h>
+#include <LibCore/File.h>
+#include <LibCore/ProcessStatisticsReader.h>
+#include <pwd.h>
+#include <stdio.h>
+
+namespace Core {
+
+HashMap<uid_t, String> ProcessStatisticsReader::s_usernames;
+
+Optional<HashMap<pid_t, Core::ProcessStatistics>> ProcessStatisticsReader::get_all(RefPtr<Core::File>& proc_all_file)
+{
+    if (proc_all_file) {
+        if (!proc_all_file->seek(0, Core::File::SeekMode::SetPosition)) {
+            fprintf(stderr, "ProcessStatisticsReader: Failed to refresh /proc/all: %s\n", proc_all_file->error_string());
+            return {};
+        }
+    } else {
+        proc_all_file = Core::File::construct("/proc/all");
+        if (!proc_all_file->open(Core::IODevice::ReadOnly)) {
+            fprintf(stderr, "ProcessStatisticsReader: Failed to open /proc/all: %s\n", proc_all_file->error_string());
+            return {};
+        }
+    }
+
+    HashMap<pid_t, Core::ProcessStatistics> map;
+
+    auto file_contents = proc_all_file->read_all();
+    auto json = JsonValue::from_string(file_contents);
+    if (!json.has_value())
+        return {};
+    json.value().as_array().for_each([&](auto& value) {
+        const JsonObject& process_object = value.as_object();
+        Core::ProcessStatistics process;
+
+        // kernel data first
+        process.pid = process_object.get("pid").to_u32();
+        process.pgid = process_object.get("pgid").to_u32();
+        process.pgp = process_object.get("pgp").to_u32();
+        process.sid = process_object.get("sid").to_u32();
+        process.uid = process_object.get("uid").to_u32();
+        process.gid = process_object.get("gid").to_u32();
+        process.ppid = process_object.get("ppid").to_u32();
+        process.nfds = process_object.get("nfds").to_u32();
+        process.name = process_object.get("name").to_string();
+        process.executable = process_object.get("executable").to_string();
+        process.tty = process_object.get("tty").to_string();
+        process.pledge = process_object.get("pledge").to_string();
+        process.veil = process_object.get("veil").to_string();
+        process.amount_virtual = process_object.get("amount_virtual").to_u32();
+        process.amount_resident = process_object.get("amount_resident").to_u32();
+        process.amount_shared = process_object.get("amount_shared").to_u32();
+        process.amount_dirty_private = process_object.get("amount_dirty_private").to_u32();
+        process.amount_clean_inode = process_object.get("amount_clean_inode").to_u32();
+        process.amount_purgeable_volatile = process_object.get("amount_purgeable_volatile").to_u32();
+        process.amount_purgeable_nonvolatile = process_object.get("amount_purgeable_nonvolatile").to_u32();
+
+        auto& thread_array = process_object.get_ptr("threads")->as_array();
+        process.threads.ensure_capacity(thread_array.size());
+        thread_array.for_each([&](auto& value) {
+            auto& thread_object = value.as_object();
+            Core::ThreadStatistics thread;
+            thread.tid = thread_object.get("tid").to_u32();
+            thread.times_scheduled = thread_object.get("times_scheduled").to_u32();
+            thread.name = thread_object.get("name").to_string();
+            thread.state = thread_object.get("state").to_string();
+            thread.ticks_user = thread_object.get("ticks_user").to_u32();
+            thread.ticks_kernel = thread_object.get("ticks_kernel").to_u32();
+            thread.cpu = thread_object.get("cpu").to_u32();
+            thread.priority = thread_object.get("priority").to_u32();
+            thread.effective_priority = thread_object.get("effective_priority").to_u32();
+            thread.syscall_count = thread_object.get("syscall_count").to_u32();
+            thread.inode_faults = thread_object.get("inode_faults").to_u32();
+            thread.zero_faults = thread_object.get("zero_faults").to_u32();
+            thread.cow_faults = thread_object.get("cow_faults").to_u32();
+            thread.unix_socket_read_bytes = thread_object.get("unix_socket_read_bytes").to_u32();
+            thread.unix_socket_write_bytes = thread_object.get("unix_socket_write_bytes").to_u32();
+            thread.ipv4_socket_read_bytes = thread_object.get("ipv4_socket_read_bytes").to_u32();
+            thread.ipv4_socket_write_bytes = thread_object.get("ipv4_socket_write_bytes").to_u32();
+            thread.file_read_bytes = thread_object.get("file_read_bytes").to_u32();
+            thread.file_write_bytes = thread_object.get("file_write_bytes").to_u32();
+            process.threads.append(move(thread));
+        });
+
+        // and synthetic data last
+        process.username = username_from_uid(process.uid);
+        map.set(process.pid, process);
+    });
+
+    return map;
+}
+
+Optional<HashMap<pid_t, Core::ProcessStatistics>> ProcessStatisticsReader::get_all()
+{
+    RefPtr<Core::File> proc_all_file;
+    return get_all(proc_all_file);
+}
+
+String ProcessStatisticsReader::username_from_uid(uid_t uid)
+{
+    if (s_usernames.is_empty()) {
+        setpwent();
+        while (auto* passwd = getpwent())
+            s_usernames.set(passwd->pw_uid, passwd->pw_name);
+        endpwent();
+    }
+
+    auto it = s_usernames.find(uid);
+    if (it != s_usernames.end())
+        return (*it).value;
+    return String::number(uid);
+}
+}

Userland/Libraries/LibCore/ProcessStatisticsReader.h

@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/HashMap.h>
+#include <AK/String.h>
+#include <LibCore/File.h>
+#include <unistd.h>
+
+namespace Core {
+
+struct ThreadStatistics {
+    pid_t tid;
+    unsigned times_scheduled;
+    unsigned ticks_user;
+    unsigned ticks_kernel;
+    unsigned syscall_count;
+    unsigned inode_faults;
+    unsigned zero_faults;
+    unsigned cow_faults;
+    unsigned unix_socket_read_bytes;
+    unsigned unix_socket_write_bytes;
+    unsigned ipv4_socket_read_bytes;
+    unsigned ipv4_socket_write_bytes;
+    unsigned file_read_bytes;
+    unsigned file_write_bytes;
+    String state;
+    u32 cpu;
+    u32 priority;
+    u32 effective_priority;
+    String name;
+};
+
+struct ProcessStatistics {
+    // Keep this in sync with /proc/all.
+    // From the kernel side:
+    pid_t pid;
+    pid_t pgid;
+    pid_t pgp;
+    pid_t sid;
+    uid_t uid;
+    gid_t gid;
+    pid_t ppid;
+    unsigned nfds;
+    String name;
+    String executable;
+    String tty;
+    String pledge;
+    String veil;
+    size_t amount_virtual;
+    size_t amount_resident;
+    size_t amount_shared;
+    size_t amount_dirty_private;
+    size_t amount_clean_inode;
+    size_t amount_purgeable_volatile;
+    size_t amount_purgeable_nonvolatile;
+
+    Vector<Core::ThreadStatistics> threads;
+
+    // synthetic
+    String username;
+};
+
+class ProcessStatisticsReader {
+public:
+    static Optional<HashMap<pid_t, Core::ProcessStatistics>> get_all(RefPtr<Core::File>&);
+    static Optional<HashMap<pid_t, Core::ProcessStatistics>> get_all();
+
+private:
+    static String username_from_uid(uid_t);
+    static HashMap<uid_t, String> s_usernames;
+};
+
+}

Userland/Libraries/LibCore/Property.cpp

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/Property.h>
+
+namespace Core {
+
+Property::Property(String name, Function<JsonValue()> getter, Function<bool(const JsonValue&)> setter)
+    : m_name(move(name))
+    , m_getter(move(getter))
+    , m_setter(move(setter))
+{
+}
+
+Property::~Property()
+{
+}
+
+}

Userland/Libraries/LibCore/Property.h

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/JsonValue.h>
+
+namespace Core {
+
+class Property {
+    AK_MAKE_NONCOPYABLE(Property);
+
+public:
+    Property(String name, Function<JsonValue()> getter, Function<bool(const JsonValue&)> setter = nullptr);
+    ~Property();
+
+    bool set(const JsonValue& value)
+    {
+        if (!m_setter)
+            return false;
+        return m_setter(value);
+    }
+
+    JsonValue get() const { return m_getter(); }
+
+    const String& name() const { return m_name; }
+    bool is_readonly() const { return !m_setter; }
+
+private:
+    String m_name;
+    Function<JsonValue()> m_getter;
+    Function<bool(const JsonValue&)> m_setter;
+};
+
+}

Userland/Libraries/LibCore/Socket.cpp

@@ -0,0 +1,236 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/ByteBuffer.h>
+#include <LibCore/Notifier.h>
+#include <LibCore/Socket.h>
+#include <arpa/inet.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+//#define CSOCKET_DEBUG
+
+namespace Core {
+
+Socket::Socket(Type type, Object* parent)
+    : IODevice(parent)
+    , m_type(type)
+{
+    register_property(
+        "source_address", [this] { return m_source_address.to_string(); },
+        [](auto&) { return false; });
+
+    register_property(
+        "destination_address", [this] { return m_destination_address.to_string(); },
+        [](auto&) { return false; });
+
+    register_property(
+        "source_port", [this] { return m_source_port; },
+        [](auto&) { return false; });
+
+    register_property(
+        "destination_port", [this] { return m_destination_port; },
+        [](auto&) { return false; });
+
+    register_property(
+        "connected", [this] { return m_connected; },
+        [](auto&) { return false; });
+}
+
+Socket::~Socket()
+{
+    close();
+}
+
+bool Socket::connect(const String& hostname, int port)
+{
+    auto* hostent = gethostbyname(hostname.characters());
+    if (!hostent) {
+        dbgln("Socket::connect: Unable to resolve '{}'", hostname);
+        return false;
+    }
+
+    IPv4Address host_address((const u8*)hostent->h_addr_list[0]);
+#ifdef CSOCKET_DEBUG
+    dbg() << "Socket::connect: Resolved '" << hostname << "' to " << host_address;
+#endif
+    return connect(host_address, port);
+}
+
+void Socket::set_blocking(bool blocking)
+{
+    int flags = fcntl(fd(), F_GETFL, 0);
+    ASSERT(flags >= 0);
+    if (blocking)
+        flags = fcntl(fd(), F_SETFL, flags & ~O_NONBLOCK);
+    else
+        flags = fcntl(fd(), F_SETFL, flags | O_NONBLOCK);
+    ASSERT(flags == 0);
+}
+
+bool Socket::connect(const SocketAddress& address, int port)
+{
+    ASSERT(!is_connected());
+    ASSERT(address.type() == SocketAddress::Type::IPv4);
+#ifdef CSOCKET_DEBUG
+    dbg() << *this << " connecting to " << address << "...";
+#endif
+
+    ASSERT(port > 0 && port <= 65535);
+
+    struct sockaddr_in addr;
+    memset(&addr, 0, sizeof(addr));
+    auto ipv4_address = address.ipv4_address();
+    memcpy(&addr.sin_addr.s_addr, &ipv4_address, sizeof(IPv4Address));
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(port);
+
+    m_destination_address = address;
+    m_destination_port = port;
+
+    return common_connect((struct sockaddr*)&addr, sizeof(addr));
+}
+
+bool Socket::connect(const SocketAddress& address)
+{
+    ASSERT(!is_connected());
+    ASSERT(address.type() == SocketAddress::Type::Local);
+#ifdef CSOCKET_DEBUG
+    dbg() << *this << " connecting to " << address << "...";
+#endif
+
+    sockaddr_un saddr;
+    saddr.sun_family = AF_LOCAL;
+    auto dest_address = address.to_string();
+    bool fits = dest_address.copy_characters_to_buffer(saddr.sun_path, sizeof(saddr.sun_path));
+    if (!fits) {
+        fprintf(stderr, "Core::Socket: Failed to connect() to %s: Path is too long!\n", dest_address.characters());
+        errno = EINVAL;
+        return false;
+    }
+    m_destination_address = address;
+
+    return common_connect((const sockaddr*)&saddr, sizeof(saddr));
+}
+
+bool Socket::common_connect(const struct sockaddr* addr, socklen_t addrlen)
+{
+    auto connected = [this] {
+#ifdef CSOCKET_DEBUG
+        dbg() << *this << " connected!";
+#endif
+        if (!m_connected) {
+            m_connected = true;
+            ensure_read_notifier();
+            if (m_notifier) {
+                m_notifier->remove_from_parent();
+                m_notifier = nullptr;
+            }
+            if (on_connected)
+                on_connected();
+        }
+    };
+    int rc = ::connect(fd(), addr, addrlen);
+    if (rc < 0) {
+        if (errno == EINPROGRESS) {
+#ifdef CSOCKET_DEBUG
+            dbg() << *this << " connection in progress (EINPROGRESS)";
+#endif
+            m_notifier = Notifier::construct(fd(), Notifier::Event::Write, this);
+            m_notifier->on_ready_to_write = move(connected);
+            return true;
+        }
+        int saved_errno = errno;
+        fprintf(stderr, "Core::Socket: Failed to connect() to %s: %s\n", destination_address().to_string().characters(), strerror(saved_errno));
+        errno = saved_errno;
+        return false;
+    }
+#ifdef CSOCKET_DEBUG
+    dbg() << *this << " connected ok!";
+#endif
+    connected();
+    return true;
+}
+
+ByteBuffer Socket::receive(int max_size)
+{
+    auto buffer = read(max_size);
+    if (eof())
+        m_connected = false;
+    return buffer;
+}
+
+bool Socket::send(ReadonlyBytes data)
+{
+    ssize_t nsent = ::send(fd(), data.data(), data.size(), 0);
+    if (nsent < 0) {
+        set_error(errno);
+        return false;
+    }
+    ASSERT(static_cast<size_t>(nsent) == data.size());
+    return true;
+}
+
+void Socket::did_update_fd(int fd)
+{
+    if (fd < 0) {
+        if (m_read_notifier) {
+            m_read_notifier->remove_from_parent();
+            m_read_notifier = nullptr;
+        }
+        if (m_notifier) {
+            m_notifier->remove_from_parent();
+            m_notifier = nullptr;
+        }
+        return;
+    }
+    if (m_connected) {
+        ensure_read_notifier();
+    } else {
+        // I don't think it would be right if we updated the fd while not connected *but* while having a notifier..
+        ASSERT(!m_read_notifier);
+    }
+}
+
+void Socket::ensure_read_notifier()
+{
+    ASSERT(m_connected);
+    m_read_notifier = Notifier::construct(fd(), Notifier::Event::Read, this);
+    m_read_notifier->on_ready_to_read = [this] {
+        if (!can_read())
+            return;
+        if (on_ready_to_read)
+            on_ready_to_read();
+    };
+}
+
+}

Userland/Libraries/LibCore/Socket.h

@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/Span.h>
+#include <LibCore/IODevice.h>
+#include <LibCore/SocketAddress.h>
+
+namespace Core {
+
+class Socket : public IODevice {
+    C_OBJECT(Socket)
+public:
+    enum class Type {
+        Invalid,
+        TCP,
+        UDP,
+        Local,
+    };
+    virtual ~Socket() override;
+
+    Type type() const { return m_type; }
+
+    virtual bool connect(const String& hostname, int port);
+    bool connect(const SocketAddress&, int port);
+    bool connect(const SocketAddress&);
+
+    ByteBuffer receive(int max_size);
+    bool send(ReadonlyBytes);
+
+    bool is_connected() const { return m_connected; }
+    void set_blocking(bool blocking);
+
+    SocketAddress source_address() const { return m_source_address; }
+    int source_port() const { return m_source_port; }
+
+    SocketAddress destination_address() const { return m_destination_address; }
+    int destination_port() const { return m_destination_port; }
+
+    Function<void()> on_connected;
+    Function<void()> on_ready_to_read;
+
+protected:
+    Socket(Type, Object* parent);
+
+    SocketAddress m_source_address;
+    SocketAddress m_destination_address;
+    int m_source_port { -1 };
+    int m_destination_port { -1 };
+    bool m_connected { false };
+
+    virtual void did_update_fd(int) override;
+    virtual bool common_connect(const struct sockaddr*, socklen_t);
+
+private:
+    virtual bool open(IODevice::OpenMode) override { ASSERT_NOT_REACHED(); }
+    void ensure_read_notifier();
+
+    Type m_type { Type::Invalid };
+    RefPtr<Notifier> m_notifier;
+    RefPtr<Notifier> m_read_notifier;
+};
+
+}

Userland/Libraries/LibCore/SocketAddress.cpp

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/SocketAddress.h>
+
+namespace Core {
+
+const LogStream& operator<<(const LogStream& stream, const SocketAddress& value)
+{
+    return stream << value.to_string();
+}
+
+}

Userland/Libraries/LibCore/SocketAddress.h

@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/IPv4Address.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+namespace Core {
+
+class SocketAddress {
+public:
+    enum class Type {
+        Invalid,
+        IPv4,
+        Local
+    };
+
+    SocketAddress() { }
+    SocketAddress(const IPv4Address& address)
+        : m_type(Type::IPv4)
+        , m_ipv4_address(address)
+    {
+    }
+
+    SocketAddress(const IPv4Address& address, u16 port)
+        : m_type(Type::IPv4)
+        , m_ipv4_address(address)
+        , m_port(port)
+    {
+    }
+
+    static SocketAddress local(const String& address)
+    {
+        SocketAddress addr;
+        addr.m_type = Type::Local;
+        addr.m_local_address = address;
+        return addr;
+    }
+
+    Type type() const { return m_type; }
+    bool is_valid() const { return m_type != Type::Invalid; }
+    IPv4Address ipv4_address() const { return m_ipv4_address; }
+    u16 port() const { return m_port; }
+
+    String to_string() const
+    {
+        switch (m_type) {
+        case Type::IPv4:
+            return String::format("%s:%d", m_ipv4_address.to_string().characters(), m_port);
+        case Type::Local:
+            return m_local_address;
+        default:
+            return "[SocketAddress]";
+        }
+    }
+
+    Optional<sockaddr_un> to_sockaddr_un() const
+    {
+        ASSERT(type() == Type::Local);
+        sockaddr_un address;
+        address.sun_family = AF_LOCAL;
+        bool fits = m_local_address.copy_characters_to_buffer(address.sun_path, sizeof(address.sun_path));
+        if (!fits)
+            return {};
+        return address;
+    }
+
+    sockaddr_in to_sockaddr_in() const
+    {
+        ASSERT(type() == Type::IPv4);
+        sockaddr_in address {};
+        address.sin_family = AF_INET;
+        address.sin_addr.s_addr = m_ipv4_address.to_in_addr_t();
+        address.sin_port = htons(m_port);
+        return address;
+    }
+
+private:
+    Type m_type { Type::Invalid };
+    IPv4Address m_ipv4_address;
+    u16 m_port { 0 };
+    String m_local_address;
+};
+
+const LogStream& operator<<(const LogStream&, const SocketAddress&);
+
+}

Userland/Libraries/LibCore/StandardPaths.cpp

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/LexicalPath.h>
+#include <AK/String.h>
+#include <AK/StringBuilder.h>
+#include <LibCore/StandardPaths.h>
+#include <pwd.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+namespace Core {
+
+String StandardPaths::home_directory()
+{
+    if (auto* home_env = getenv("HOME"))
+        return LexicalPath::canonicalized_path(home_env);
+
+    auto* pwd = getpwuid(getuid());
+    String path = pwd ? pwd->pw_dir : "/";
+    endpwent();
+    return LexicalPath::canonicalized_path(path);
+}
+
+String StandardPaths::desktop_directory()
+{
+    StringBuilder builder;
+    builder.append(home_directory());
+    builder.append("/Desktop");
+    return LexicalPath::canonicalized_path(builder.to_string());
+}
+
+String StandardPaths::downloads_directory()
+{
+    StringBuilder builder;
+    builder.append(home_directory());
+    builder.append("/Downloads");
+    return LexicalPath::canonicalized_path(builder.to_string());
+}
+
+String StandardPaths::config_directory()
+{
+    StringBuilder builder;
+    builder.append(home_directory());
+    builder.append("/.config");
+    return LexicalPath::canonicalized_path(builder.to_string());
+}
+
+String StandardPaths::tempfile_directory()
+{
+    return "/tmp";
+}
+
+}

Userland/Libraries/LibCore/StandardPaths.h

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+
+namespace Core {
+
+class StandardPaths {
+public:
+    static String home_directory();
+    static String desktop_directory();
+    static String downloads_directory();
+    static String tempfile_directory();
+    static String config_directory();
+};
+
+}

Userland/Libraries/LibCore/SyscallUtils.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/LogStream.h>
+#include <AK/StdLibExtras.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+namespace Core {
+
+template<typename Syscall, class... Args>
+inline int safe_syscall(Syscall syscall, Args&&... args)
+{
+    for (;;) {
+        int sysret = syscall(forward<Args>(args)...);
+        if (sysret == -1) {
+#ifdef SAFE_SYSCALL_DEBUG
+            int saved_errno = errno;
+            dbg() << "Core::safe_syscall: " << sysret << " (" << saved_errno << ": " << strerror(saved_errno) << ")";
+#endif
+            if (errno == EINTR)
+                continue;
+            ASSERT_NOT_REACHED();
+        }
+        return sysret;
+    }
+}
+
+}

Userland/Libraries/LibCore/TCPServer.cpp

@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/IPv4Address.h>
+#include <AK/Types.h>
+#include <LibCore/Notifier.h>
+#include <LibCore/TCPServer.h>
+#include <LibCore/TCPSocket.h>
+#include <stdio.h>
+#include <sys/socket.h>
+
+#ifndef SOCK_NONBLOCK
+#    include <sys/ioctl.h>
+#endif
+namespace Core {
+
+TCPServer::TCPServer(Object* parent)
+    : Object(parent)
+{
+#ifdef SOCK_NONBLOCK
+    m_fd = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
+#else
+    m_fd = socket(AF_INET, SOCK_STREAM, 0);
+    int option = 1;
+    ioctl(m_fd, FIONBIO, &option);
+    fcntl(m_fd, F_SETFD, FD_CLOEXEC);
+#endif
+    ASSERT(m_fd >= 0);
+}
+
+TCPServer::~TCPServer()
+{
+    ::close(m_fd);
+}
+
+bool TCPServer::listen(const IPv4Address& address, u16 port)
+{
+    if (m_listening)
+        return false;
+
+    auto socket_address = SocketAddress(address, port);
+    auto in = socket_address.to_sockaddr_in();
+    if (::bind(m_fd, (const sockaddr*)&in, sizeof(in)) < 0) {
+        perror("TCPServer::listen: bind");
+        return false;
+    }
+
+    if (::listen(m_fd, 5) < 0) {
+        perror("TCPServer::listen: listen");
+        return false;
+    }
+    m_listening = true;
+
+    m_notifier = Notifier::construct(m_fd, Notifier::Event::Read, this);
+    m_notifier->on_ready_to_read = [this] {
+        if (on_ready_to_accept)
+            on_ready_to_accept();
+    };
+    return true;
+}
+
+RefPtr<TCPSocket> TCPServer::accept()
+{
+    ASSERT(m_listening);
+    sockaddr_in in;
+    socklen_t in_size = sizeof(in);
+    int accepted_fd = ::accept(m_fd, (sockaddr*)&in, &in_size);
+    if (accepted_fd < 0) {
+        perror("accept");
+        return nullptr;
+    }
+
+    return TCPSocket::construct(accepted_fd);
+}
+
+Optional<IPv4Address> TCPServer::local_address() const
+{
+    if (m_fd == -1)
+        return {};
+
+    sockaddr_in address;
+    socklen_t len = sizeof(address);
+    if (getsockname(m_fd, (sockaddr*)&address, &len) != 0)
+        return {};
+
+    return IPv4Address(address.sin_addr.s_addr);
+}
+
+Optional<u16> TCPServer::local_port() const
+{
+    if (m_fd == -1)
+        return {};
+
+    sockaddr_in address;
+    socklen_t len = sizeof(address);
+    if (getsockname(m_fd, (sockaddr*)&address, &len) != 0)
+        return {};
+
+    return ntohs(address.sin_port);
+}
+
+}

Userland/Libraries/LibCore/TCPServer.h

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/IPv4Address.h>
+#include <LibCore/Notifier.h>
+#include <LibCore/Object.h>
+
+namespace Core {
+
+class TCPServer : public Object {
+    C_OBJECT(TCPServer)
+public:
+    virtual ~TCPServer() override;
+
+    bool is_listening() const { return m_listening; }
+    bool listen(const IPv4Address& address, u16 port);
+
+    RefPtr<TCPSocket> accept();
+
+    Optional<IPv4Address> local_address() const;
+    Optional<u16> local_port() const;
+
+    Function<void()> on_ready_to_accept;
+
+private:
+    explicit TCPServer(Object* parent = nullptr);
+
+    int m_fd { -1 };
+    bool m_listening { false };
+    RefPtr<Notifier> m_notifier;
+};
+
+}

Userland/Libraries/LibCore/TCPSocket.cpp

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/TCPSocket.h>
+#include <errno.h>
+#include <sys/socket.h>
+
+#ifndef SOCK_NONBLOCK
+#    include <sys/ioctl.h>
+#endif
+
+namespace Core {
+
+TCPSocket::TCPSocket(int fd, Object* parent)
+    : Socket(Socket::Type::TCP, parent)
+{
+    // NOTE: This constructor is used by TCPServer::accept(), so the socket is already connected.
+    m_connected = true;
+    set_fd(fd);
+    set_mode(IODevice::ReadWrite);
+    set_error(0);
+}
+
+TCPSocket::TCPSocket(Object* parent)
+    : Socket(Socket::Type::TCP, parent)
+{
+#ifdef SOCK_NONBLOCK
+    int fd = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);
+#else
+    int fd = socket(AF_INET, SOCK_STREAM, 0);
+    int option = 1;
+    ioctl(fd, FIONBIO, &option);
+#endif
+    if (fd < 0) {
+        set_error(errno);
+    } else {
+        set_fd(fd);
+        set_mode(IODevice::ReadWrite);
+        set_error(0);
+    }
+}
+
+TCPSocket::~TCPSocket()
+{
+}
+
+}

Userland/Libraries/LibCore/TCPSocket.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Badge.h>
+#include <LibCore/Socket.h>
+
+namespace Core {
+
+class TCPSocket final : public Socket {
+    C_OBJECT(TCPSocket)
+public:
+    virtual ~TCPSocket() override;
+
+private:
+    TCPSocket(int fd, Object* parent = nullptr);
+    explicit TCPSocket(Object* parent = nullptr);
+};
+
+}

Userland/Libraries/LibCore/Timer.cpp

@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/Timer.h>
+
+namespace Core {
+
+Timer::Timer(Object* parent)
+    : Object(parent)
+{
+}
+
+Timer::Timer(int interval, Function<void()>&& timeout_handler, Object* parent)
+    : Object(parent)
+    , on_timeout(move(timeout_handler))
+{
+    start(interval);
+}
+
+Timer::~Timer()
+{
+}
+
+void Timer::start()
+{
+    start(m_interval);
+}
+
+void Timer::start(int interval)
+{
+    if (m_active)
+        return;
+    m_interval = interval;
+    start_timer(interval);
+    m_active = true;
+}
+
+void Timer::restart()
+{
+    restart(m_interval);
+}
+
+void Timer::restart(int interval)
+{
+    if (m_active)
+        stop();
+    start(interval);
+}
+
+void Timer::stop()
+{
+    if (!m_active)
+        return;
+    stop_timer();
+    m_active = false;
+}
+
+void Timer::timer_event(TimerEvent&)
+{
+    if (m_single_shot)
+        stop();
+    else {
+        if (m_interval_dirty) {
+            stop();
+            start(m_interval);
+        }
+    }
+
+    if (on_timeout)
+        on_timeout();
+}
+
+}

Userland/Libraries/LibCore/Timer.h

@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <LibCore/Object.h>
+
+namespace Core {
+
+class Timer final : public Object {
+    C_OBJECT(Timer);
+
+public:
+    static NonnullRefPtr<Timer> create_single_shot(int interval, Function<void()>&& timeout_handler, Object* parent = nullptr)
+    {
+        auto timer = adopt(*new Timer(interval, move(timeout_handler), parent));
+        timer->set_single_shot(true);
+        timer->stop();
+        return timer;
+    }
+
+    virtual ~Timer() override;
+
+    void start();
+    void start(int interval);
+    void restart();
+    void restart(int interval);
+    void stop();
+
+    bool is_active() const { return m_active; }
+    int interval() const { return m_interval; }
+    void set_interval(int interval)
+    {
+        if (m_interval == interval)
+            return;
+        m_interval = interval;
+        m_interval_dirty = true;
+    }
+
+    bool is_single_shot() const { return m_single_shot; }
+    void set_single_shot(bool single_shot) { m_single_shot = single_shot; }
+
+    Function<void()> on_timeout;
+
+private:
+    explicit Timer(Object* parent = nullptr);
+    Timer(int interval, Function<void()>&& timeout_handler, Object* parent = nullptr);
+
+    virtual void timer_event(TimerEvent&) override;
+
+    bool m_active { false };
+    bool m_single_shot { false };
+    bool m_interval_dirty { false };
+    int m_interval { 0 };
+};
+
+}

Userland/Libraries/LibCore/UDPServer.cpp

@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/IPv4Address.h>
+#include <AK/Types.h>
+#include <LibCore/Notifier.h>
+#include <LibCore/UDPServer.h>
+#include <LibCore/UDPSocket.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#ifndef SOCK_NONBLOCK
+#    include <sys/ioctl.h>
+#endif
+
+namespace Core {
+
+UDPServer::UDPServer(Object* parent)
+    : Object(parent)
+{
+#ifdef SOCK_NONBLOCK
+    m_fd = socket(AF_INET, SOCK_DGRAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
+#else
+    m_fd = socket(AF_INET, SOCK_DGRAM, 0);
+    int option = 1;
+    ioctl(m_fd, FIONBIO, &option);
+    fcntl(m_fd, F_SETFD, FD_CLOEXEC);
+#endif
+    ASSERT(m_fd >= 0);
+}
+
+UDPServer::~UDPServer()
+{
+    ::close(m_fd);
+}
+
+bool UDPServer::bind(const IPv4Address& address, u16 port)
+{
+    if (m_bound)
+        return false;
+
+    auto saddr = SocketAddress(address, port);
+    auto in = saddr.to_sockaddr_in();
+
+    if (::bind(m_fd, (const sockaddr*)&in, sizeof(in)) != 0) {
+        perror("UDPServer::bind");
+        return false;
+    }
+
+    m_bound = true;
+
+    m_notifier = Notifier::construct(m_fd, Notifier::Event::Read, this);
+    m_notifier->on_ready_to_read = [this] {
+        if (on_ready_to_receive)
+            on_ready_to_receive();
+    };
+    return true;
+}
+
+ByteBuffer UDPServer::receive(size_t size, sockaddr_in& in)
+{
+    auto buf = ByteBuffer::create_uninitialized(size);
+    socklen_t in_len = sizeof(in);
+    ssize_t rlen = ::recvfrom(m_fd, buf.data(), size, 0, (sockaddr*)&in, &in_len);
+    if (rlen < 0) {
+        dbgln("recvfrom: {}", strerror(errno));
+        return {};
+    }
+
+    buf.trim(rlen);
+    return buf;
+}
+
+Optional<IPv4Address> UDPServer::local_address() const
+{
+    if (m_fd == -1)
+        return {};
+
+    sockaddr_in address;
+    socklen_t len = sizeof(address);
+    if (getsockname(m_fd, (sockaddr*)&address, &len) != 0)
+        return {};
+
+    return IPv4Address(address.sin_addr.s_addr);
+}
+
+Optional<u16> UDPServer::local_port() const
+{
+    if (m_fd == -1)
+        return {};
+
+    sockaddr_in address;
+    socklen_t len = sizeof(address);
+    if (getsockname(m_fd, (sockaddr*)&address, &len) != 0)
+        return {};
+
+    return ntohs(address.sin_port);
+}
+
+}

Userland/Libraries/LibCore/UDPServer.h

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/ByteBuffer.h>
+#include <AK/Forward.h>
+#include <AK/Function.h>
+#include <LibCore/Forward.h>
+#include <LibCore/Object.h>
+#include <LibCore/SocketAddress.h>
+
+namespace Core {
+
+class UDPServer : public Object {
+    C_OBJECT(UDPServer)
+public:
+    virtual ~UDPServer() override;
+
+    bool is_bound() const { return m_bound; }
+
+    bool bind(const IPv4Address& address, u16 port);
+    ByteBuffer receive(size_t size, sockaddr_in& from);
+    ByteBuffer receive(size_t size)
+    {
+        struct sockaddr_in saddr;
+        return receive(size, saddr);
+    };
+
+    Optional<IPv4Address> local_address() const;
+    Optional<u16> local_port() const;
+
+    Function<void()> on_ready_to_receive;
+
+private:
+    explicit UDPServer(Object* parent = nullptr);
+
+    int m_fd { -1 };
+    bool m_bound { false };
+    RefPtr<Notifier> m_notifier;
+};
+
+}

Userland/Libraries/LibCore/UDPSocket.cpp

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/UDPSocket.h>
+#include <errno.h>
+#include <sys/socket.h>
+
+#ifndef SOCK_NONBLOCK
+#    include <sys/ioctl.h>
+#endif
+
+namespace Core {
+
+UDPSocket::UDPSocket(Object* parent)
+    : Socket(Socket::Type::UDP, parent)
+{
+#ifdef SOCK_NONBLOCK
+    int fd = socket(AF_INET, SOCK_DGRAM | SOCK_NONBLOCK, 0);
+#else
+    int fd = socket(AF_INET, SOCK_DGRAM, 0);
+    int option = 1;
+    ioctl(fd, FIONBIO, &option);
+#endif
+
+    if (fd < 0) {
+        set_error(errno);
+    } else {
+        set_fd(fd);
+        set_mode(IODevice::ReadWrite);
+        set_error(0);
+    }
+}
+
+UDPSocket::~UDPSocket()
+{
+}
+
+}

Userland/Libraries/LibCore/UDPSocket.h

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibCore/Socket.h>
+
+namespace Core {
+
+class UDPSocket final : public Socket {
+    C_OBJECT(UDPSocket)
+public:
+    virtual ~UDPSocket() override;
+
+private:
+    explicit UDPSocket(Object* parent = nullptr);
+};
+
+}

Userland/Libraries/LibCore/puff.cpp

@@ -0,0 +1,832 @@
+/*
+ * puff.c
+ * Copyright (C) 2002-2013 Mark Adler
+ * For conditions of distribution and use, see copyright notice in puff.h
+ * version 2.3, 21 Jan 2013
+ *
+ * puff.c is a simple inflate written to be an unambiguous way to specify the
+ * deflate format.  It is not written for speed but rather simplicity.  As a
+ * side benefit, this code might actually be useful when small code is more
+ * important than speed, such as bootstrap applications.  For typical deflate
+ * data, zlib's inflate() is about four times as fast as puff().  zlib's
+ * inflate compiles to around 20K on my machine, whereas puff.c compiles to
+ * around 4K on my machine (a PowerPC using GNU cc).  If the faster decode()
+ * function here is used, then puff() is only twice as slow as zlib's
+ * inflate().
+ *
+ * All dynamically allocated memory comes from the stack.  The stack required
+ * is less than 2K bytes.  This code is compatible with 16-bit int's and
+ * assumes that long's are at least 32 bits.  puff.c uses the short data type,
+ * assumed to be 16 bits, for arrays in order to conserve memory.  The code
+ * works whether integers are stored big endian or little endian.
+ *
+ * In the comments below are "Format notes" that describe the inflate process
+ * and document some of the less obvious aspects of the format.  This source
+ * code is meant to supplement RFC 1951, which formally describes the deflate
+ * format:
+ *
+ *    http://www.zlib.org/rfc-deflate.html
+ */
+
+/*
+ * Change history:
+ *
+ * 1.0  10 Feb 2002     - First version
+ * 1.1  17 Feb 2002     - Clarifications of some comments and notes
+ *                      - Update puff() dest and source pointers on negative
+ *                        errors to facilitate debugging deflators
+ *                      - Remove longest from struct huffman -- not needed
+ *                      - Simplify offs[] index in construct()
+ *                      - Add input size and checking, using longjmp() to
+ *                        maintain easy readability
+ *                      - Use short data type for large arrays
+ *                      - Use pointers instead of long to specify source and
+ *                        destination sizes to avoid arbitrary 4 GB limits
+ * 1.2  17 Mar 2002     - Add faster version of decode(), doubles speed (!),
+ *                        but leave simple version for readabilty
+ *                      - Make sure invalid distances detected if pointers
+ *                        are 16 bits
+ *                      - Fix fixed codes table error
+ *                      - Provide a scanning mode for determining size of
+ *                        uncompressed data
+ * 1.3  20 Mar 2002     - Go back to lengths for puff() parameters [Gailly]
+ *                      - Add a puff.h file for the interface
+ *                      - Add braces in puff() for else do [Gailly]
+ *                      - Use indexes instead of pointers for readability
+ * 1.4  31 Mar 2002     - Simplify construct() code set check
+ *                      - Fix some comments
+ *                      - Add FIXLCODES #define
+ * 1.5   6 Apr 2002     - Minor comment fixes
+ * 1.6   7 Aug 2002     - Minor format changes
+ * 1.7   3 Mar 2003     - Added test code for distribution
+ *                      - Added zlib-like license
+ * 1.8   9 Jan 2004     - Added some comments on no distance codes case
+ * 1.9  21 Feb 2008     - Fix bug on 16-bit integer architectures [Pohland]
+ *                      - Catch missing end-of-block symbol error
+ * 2.0  25 Jul 2008     - Add #define to permit distance too far back
+ *                      - Add option in TEST code for puff to write the data
+ *                      - Add option in TEST code to skip input bytes
+ *                      - Allow TEST code to read from piped stdin
+ * 2.1   4 Apr 2010     - Avoid variable initialization for happier compilers
+ *                      - Avoid unsigned comparisons for even happier compilers
+ * 2.2  25 Apr 2010     - Fix bug in variable initializations [Oberhumer]
+ *                      - Add const where appropriate [Oberhumer]
+ *                      - Split if's and ?'s for coverage testing
+ *                      - Break out test code to separate file
+ *                      - Move NIL to puff.h
+ *                      - Allow incomplete code only if single code length is 1
+ *                      - Add full code coverage test to Makefile
+ * 2.3  21 Jan 2013     - Check for invalid code length codes in dynamic blocks
+ */
+
+#include "puff.h"   /* prototype for puff() */
+#include <setjmp.h> /* for setjmp(), longjmp(), and jmp_buf */
+
+#define local static /* for local function definitions */
+
+/*
+ * Maximums for allocations and loops.  It is not useful to change these --
+ * they are fixed by the deflate format.
+ */
+#define MAXBITS 15                       /* maximum bits in a code */
+#define MAXLCODES 286                    /* maximum number of literal/length codes */
+#define MAXDCODES 30                     /* maximum number of distance codes */
+#define MAXCODES (MAXLCODES + MAXDCODES) /* maximum codes lengths to read */
+#define FIXLCODES 288                    /* number of fixed literal/length codes */
+
+/* input and output state */
+struct state {
+    /* output state */
+    unsigned char* out;   /* output buffer */
+    unsigned long outlen; /* available space at out */
+    unsigned long outcnt; /* bytes written to out so far */
+
+    /* input state */
+    const unsigned char* in; /* input buffer */
+    unsigned long inlen;     /* available input at in */
+    unsigned long incnt;     /* bytes read so far */
+    int bitbuf;              /* bit buffer */
+    int bitcnt;              /* number of bits in bit buffer */
+
+    /* input limit error return state for bits() and decode() */
+    jmp_buf env;
+};
+
+/*
+ * Return need bits from the input stream.  This always leaves less than
+ * eight bits in the buffer.  bits() works properly for need == 0.
+ *
+ * Format notes:
+ *
+ * - Bits are stored in bytes from the least significant bit to the most
+ *   significant bit.  Therefore bits are dropped from the bottom of the bit
+ *   buffer, using shift right, and new bytes are appended to the top of the
+ *   bit buffer, using shift left.
+ */
+local int bits(struct state* s, int need)
+{
+    long val; /* bit accumulator (can use up to 20 bits) */
+
+    /* load at least need bits into val */
+    val = s->bitbuf;
+    while (s->bitcnt < need) {
+        if (s->incnt == s->inlen)
+            longjmp(s->env, 1);                        /* out of input */
+        val |= (long)(s->in[s->incnt++]) << s->bitcnt; /* load eight bits */
+        s->bitcnt += 8;
+    }
+
+    /* drop need bits and update buffer, always zero to seven bits left */
+    s->bitbuf = (int)(val >> need);
+    s->bitcnt -= need;
+
+    /* return need bits, zeroing the bits above that */
+    return (int)(val & ((1L << need) - 1));
+}
+
+/*
+ * Process a stored block.
+ *
+ * Format notes:
+ *
+ * - After the two-bit stored block type (00), the stored block length and
+ *   stored bytes are byte-aligned for fast copying.  Therefore any leftover
+ *   bits in the byte that has the last bit of the type, as many as seven, are
+ *   discarded.  The value of the discarded bits are not defined and should not
+ *   be checked against any expectation.
+ *
+ * - The second inverted copy of the stored block length does not have to be
+ *   checked, but it's probably a good idea to do so anyway.
+ *
+ * - A stored block can have zero length.  This is sometimes used to byte-align
+ *   subsets of the compressed data for random access or partial recovery.
+ */
+local int stored(struct state* s)
+{
+    unsigned len; /* length of stored block */
+
+    /* discard leftover bits from current byte (assumes s->bitcnt < 8) */
+    s->bitbuf = 0;
+    s->bitcnt = 0;
+
+    /* get length and check against its one's complement */
+    if (s->incnt + 4 > s->inlen)
+        return 2; /* not enough input */
+    len = s->in[s->incnt++];
+    len |= s->in[s->incnt++] << 8;
+    if (s->in[s->incnt++] != (~len & 0xff) || s->in[s->incnt++] != ((~len >> 8) & 0xff))
+        return -2; /* didn't match complement! */
+
+    /* copy len bytes from in to out */
+    if (s->incnt + len > s->inlen)
+        return 2; /* not enough input */
+    if (s->out != NIL) {
+        if (s->outcnt + len > s->outlen)
+            return 1; /* not enough output space */
+        while (len--)
+            s->out[s->outcnt++] = s->in[s->incnt++];
+    } else { /* just scanning */
+        s->outcnt += len;
+        s->incnt += len;
+    }
+
+    /* done with a valid stored block */
+    return 0;
+}
+
+/*
+ * Huffman code decoding tables.  count[1..MAXBITS] is the number of symbols of
+ * each length, which for a canonical code are stepped through in order.
+ * symbol[] are the symbol values in canonical order, where the number of
+ * entries is the sum of the counts in count[].  The decoding process can be
+ * seen in the function decode() below.
+ */
+struct huffman {
+    short* count;  /* number of symbols of each length */
+    short* symbol; /* canonically ordered symbols */
+};
+
+/*
+ * Decode a code from the stream s using huffman table h.  Return the symbol or
+ * a negative value if there is an error.  If all of the lengths are zero, i.e.
+ * an empty code, or if the code is incomplete and an invalid code is received,
+ * then -10 is returned after reading MAXBITS bits.
+ *
+ * Format notes:
+ *
+ * - The codes as stored in the compressed data are bit-reversed relative to
+ *   a simple integer ordering of codes of the same lengths.  Hence below the
+ *   bits are pulled from the compressed data one at a time and used to
+ *   build the code value reversed from what is in the stream in order to
+ *   permit simple integer comparisons for decoding.  A table-based decoding
+ *   scheme (as used in zlib) does not need to do this reversal.
+ *
+ * - The first code for the shortest length is all zeros.  Subsequent codes of
+ *   the same length are simply integer increments of the previous code.  When
+ *   moving up a length, a zero bit is appended to the code.  For a complete
+ *   code, the last code of the longest length will be all ones.
+ *
+ * - Incomplete codes are handled by this decoder, since they are permitted
+ *   in the deflate format.  See the format notes for fixed() and dynamic().
+ */
+#ifdef SLOW
+local int decode(struct state* s, const struct huffman* h)
+{
+    int len;   /* current number of bits in code */
+    int code;  /* len bits being decoded */
+    int first; /* first code of length len */
+    int count; /* number of codes of length len */
+    int index; /* index of first code of length len in symbol table */
+
+    code = first = index = 0;
+    for (len = 1; len <= MAXBITS; len++) {
+        code |= bits(s, 1); /* get next bit */
+        count = h->count[len];
+        if (code - count < first) /* if length len, return symbol */
+            return h->symbol[index + (code - first)];
+        index += count; /* else update for next length */
+        first += count;
+        first <<= 1;
+        code <<= 1;
+    }
+    return -10; /* ran out of codes */
+}
+
+/*
+ * A faster version of decode() for real applications of this code.   It's not
+ * as readable, but it makes puff() twice as fast.  And it only makes the code
+ * a few percent larger.
+ */
+#else  /* !SLOW */
+local int decode(struct state* s, const struct huffman* h)
+{
+    int len;     /* current number of bits in code */
+    int code;    /* len bits being decoded */
+    int first;   /* first code of length len */
+    int count;   /* number of codes of length len */
+    int index;   /* index of first code of length len in symbol table */
+    int bitbuf;  /* bits from stream */
+    int left;    /* bits left in next or left to process */
+    short* next; /* next number of codes */
+
+    bitbuf = s->bitbuf;
+    left = s->bitcnt;
+    code = first = index = 0;
+    len = 1;
+    next = h->count + 1;
+    while (1) {
+        while (left--) {
+            code |= bitbuf & 1;
+            bitbuf >>= 1;
+            count = *next++;
+            if (code - count < first) { /* if length len, return symbol */
+                s->bitbuf = bitbuf;
+                s->bitcnt = (s->bitcnt - len) & 7;
+                return h->symbol[index + (code - first)];
+            }
+            index += count; /* else update for next length */
+            first += count;
+            first <<= 1;
+            code <<= 1;
+            len++;
+        }
+        left = (MAXBITS + 1) - len;
+        if (left == 0)
+            break;
+        if (s->incnt == s->inlen)
+            longjmp(s->env, 1); /* out of input */
+        bitbuf = s->in[s->incnt++];
+        if (left > 8)
+            left = 8;
+    }
+    return -10; /* ran out of codes */
+}
+#endif /* SLOW */
+
+/*
+ * Given the list of code lengths length[0..n-1] representing a canonical
+ * Huffman code for n symbols, construct the tables required to decode those
+ * codes.  Those tables are the number of codes of each length, and the symbols
+ * sorted by length, retaining their original order within each length.  The
+ * return value is zero for a complete code set, negative for an over-
+ * subscribed code set, and positive for an incomplete code set.  The tables
+ * can be used if the return value is zero or positive, but they cannot be used
+ * if the return value is negative.  If the return value is zero, it is not
+ * possible for decode() using that table to return an error--any stream of
+ * enough bits will resolve to a symbol.  If the return value is positive, then
+ * it is possible for decode() using that table to return an error for received
+ * codes past the end of the incomplete lengths.
+ *
+ * Not used by decode(), but used for error checking, h->count[0] is the number
+ * of the n symbols not in the code.  So n - h->count[0] is the number of
+ * codes.  This is useful for checking for incomplete codes that have more than
+ * one symbol, which is an error in a dynamic block.
+ *
+ * Assumption: for all i in 0..n-1, 0 <= length[i] <= MAXBITS
+ * This is assured by the construction of the length arrays in dynamic() and
+ * fixed() and is not verified by construct().
+ *
+ * Format notes:
+ *
+ * - Permitted and expected examples of incomplete codes are one of the fixed
+ *   codes and any code with a single symbol which in deflate is coded as one
+ *   bit instead of zero bits.  See the format notes for fixed() and dynamic().
+ *
+ * - Within a given code length, the symbols are kept in ascending order for
+ *   the code bits definition.
+ */
+local int construct(struct huffman* h, const short* length, int n)
+{
+    int symbol;              /* current symbol when stepping through length[] */
+    int len;                 /* current length when stepping through h->count[] */
+    int left;                /* number of possible codes left of current length */
+    short offs[MAXBITS + 1]; /* offsets in symbol table for each length */
+
+    /* count number of codes of each length */
+    for (len = 0; len <= MAXBITS; len++)
+        h->count[len] = 0;
+    for (symbol = 0; symbol < n; symbol++)
+        (h->count[length[symbol]])++; /* assumes lengths are within bounds */
+    if (h->count[0] == n)             /* no codes! */
+        return 0;                     /* complete, but decode() will fail */
+
+    /* check for an over-subscribed or incomplete set of lengths */
+    left = 1; /* one possible code of zero length */
+    for (len = 1; len <= MAXBITS; len++) {
+        left <<= 1;            /* one more bit, double codes left */
+        left -= h->count[len]; /* deduct count from possible codes */
+        if (left < 0)
+            return left; /* over-subscribed--return negative */
+    }                    /* left > 0 means incomplete */
+
+    /* generate offsets into symbol table for each length for sorting */
+    offs[1] = 0;
+    for (len = 1; len < MAXBITS; len++)
+        offs[len + 1] = offs[len] + h->count[len];
+
+    /*
+     * put symbols in table sorted by length, by symbol order within each
+     * length
+     */
+    for (symbol = 0; symbol < n; symbol++)
+        if (length[symbol] != 0)
+            h->symbol[offs[length[symbol]]++] = symbol;
+
+    /* return zero for complete set, positive for incomplete set */
+    return left;
+}
+
+/*
+ * Decode literal/length and distance codes until an end-of-block code.
+ *
+ * Format notes:
+ *
+ * - Compressed data that is after the block type if fixed or after the code
+ *   description if dynamic is a combination of literals and length/distance
+ *   pairs terminated by and end-of-block code.  Literals are simply Huffman
+ *   coded bytes.  A length/distance pair is a coded length followed by a
+ *   coded distance to represent a string that occurs earlier in the
+ *   uncompressed data that occurs again at the current location.
+ *
+ * - Literals, lengths, and the end-of-block code are combined into a single
+ *   code of up to 286 symbols.  They are 256 literals (0..255), 29 length
+ *   symbols (257..285), and the end-of-block symbol (256).
+ *
+ * - There are 256 possible lengths (3..258), and so 29 symbols are not enough
+ *   to represent all of those.  Lengths 3..10 and 258 are in fact represented
+ *   by just a length symbol.  Lengths 11..257 are represented as a symbol and
+ *   some number of extra bits that are added as an integer to the base length
+ *   of the length symbol.  The number of extra bits is determined by the base
+ *   length symbol.  These are in the static arrays below, lens[] for the base
+ *   lengths and lext[] for the corresponding number of extra bits.
+ *
+ * - The reason that 258 gets its own symbol is that the longest length is used
+ *   often in highly redundant files.  Note that 258 can also be coded as the
+ *   base value 227 plus the maximum extra value of 31.  While a good deflate
+ *   should never do this, it is not an error, and should be decoded properly.
+ *
+ * - If a length is decoded, including its extra bits if any, then it is
+ *   followed a distance code.  There are up to 30 distance symbols.  Again
+ *   there are many more possible distances (1..32768), so extra bits are added
+ *   to a base value represented by the symbol.  The distances 1..4 get their
+ *   own symbol, but the rest require extra bits.  The base distances and
+ *   corresponding number of extra bits are below in the static arrays dist[]
+ *   and dext[].
+ *
+ * - Literal bytes are simply written to the output.  A length/distance pair is
+ *   an instruction to copy previously uncompressed bytes to the output.  The
+ *   copy is from distance bytes back in the output stream, copying for length
+ *   bytes.
+ *
+ * - Distances pointing before the beginning of the output data are not
+ *   permitted.
+ *
+ * - Overlapped copies, where the length is greater than the distance, are
+ *   allowed and common.  For example, a distance of one and a length of 258
+ *   simply copies the last byte 258 times.  A distance of four and a length of
+ *   twelve copies the last four bytes three times.  A simple forward copy
+ *   ignoring whether the length is greater than the distance or not implements
+ *   this correctly.  You should not use memcpy() since its behavior is not
+ *   defined for overlapped arrays.  You should not use memmove() or bcopy()
+ *   since though their behavior -is- defined for overlapping arrays, it is
+ *   defined to do the wrong thing in this case.
+ */
+local int codes(struct state* s,
+    const struct huffman* lencode,
+    const struct huffman* distcode)
+{
+    int symbol;                     /* decoded symbol */
+    int len;                        /* length for copy */
+    unsigned dist;                  /* distance for copy */
+    static const short lens[29] = { /* Size base for length codes 257..285 */
+        3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
+        35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258
+    };
+    static const short lext[29] = { /* Extra bits for length codes 257..285 */
+        0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
+        3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0
+    };
+    static const short dists[30] = { /* Offset base for distance codes 0..29 */
+        1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
+        257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
+        8193, 12289, 16385, 24577
+    };
+    static const short dext[30] = { /* Extra bits for distance codes 0..29 */
+        0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
+        7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
+        12, 12, 13, 13
+    };
+
+    /* decode literals and length/distance pairs */
+    do {
+        symbol = decode(s, lencode);
+        if (symbol < 0)
+            return symbol;  /* invalid symbol */
+        if (symbol < 256) { /* literal: symbol is the byte */
+            /* write out the literal */
+            if (s->out != NIL) {
+                if (s->outcnt == s->outlen)
+                    return 1;
+                s->out[s->outcnt] = symbol;
+            }
+            s->outcnt++;
+        } else if (symbol > 256) { /* length */
+            /* get and compute length */
+            symbol -= 257;
+            if (symbol >= 29)
+                return -10; /* invalid fixed code */
+            len = lens[symbol] + bits(s, lext[symbol]);
+
+            /* get and check distance */
+            symbol = decode(s, distcode);
+            if (symbol < 0)
+                return symbol; /* invalid symbol */
+            dist = dists[symbol] + bits(s, dext[symbol]);
+#ifndef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
+            if (dist > s->outcnt)
+                return -11; /* distance too far back */
+#endif
+
+            /* copy length bytes from distance bytes back */
+            if (s->out != NIL) {
+                if (s->outcnt + len > s->outlen)
+                    return 1;
+                while (len--) {
+                    s->out[s->outcnt] =
+#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
+                        dist > s->outcnt ? 0 :
+#endif
+                                         s->out[s->outcnt - dist];
+                    s->outcnt++;
+                }
+            } else
+                s->outcnt += len;
+        }
+    } while (symbol != 256); /* end of block symbol */
+
+    /* done with a valid fixed or dynamic block */
+    return 0;
+}
+
+/*
+ * Process a fixed codes block.
+ *
+ * Format notes:
+ *
+ * - This block type can be useful for compressing small amounts of data for
+ *   which the size of the code descriptions in a dynamic block exceeds the
+ *   benefit of custom codes for that block.  For fixed codes, no bits are
+ *   spent on code descriptions.  Instead the code lengths for literal/length
+ *   codes and distance codes are fixed.  The specific lengths for each symbol
+ *   can be seen in the "for" loops below.
+ *
+ * - The literal/length code is complete, but has two symbols that are invalid
+ *   and should result in an error if received.  This cannot be implemented
+ *   simply as an incomplete code since those two symbols are in the "middle"
+ *   of the code.  They are eight bits long and the longest literal/length\
+ *   code is nine bits.  Therefore the code must be constructed with those
+ *   symbols, and the invalid symbols must be detected after decoding.
+ *
+ * - The fixed distance codes also have two invalid symbols that should result
+ *   in an error if received.  Since all of the distance codes are the same
+ *   length, this can be implemented as an incomplete code.  Then the invalid
+ *   codes are detected while decoding.
+ */
+local int fixed(struct state* s)
+{
+    static int virgin = 1;
+    static short lencnt[MAXBITS + 1], lensym[FIXLCODES];
+    static short distcnt[MAXBITS + 1], distsym[MAXDCODES];
+    static struct huffman lencode, distcode;
+
+    /* build fixed huffman tables if first call (may not be thread safe) */
+    if (virgin) {
+        int symbol;
+        short lengths[FIXLCODES];
+
+        /* construct lencode and distcode */
+        lencode.count = lencnt;
+        lencode.symbol = lensym;
+        distcode.count = distcnt;
+        distcode.symbol = distsym;
+
+        /* literal/length table */
+        for (symbol = 0; symbol < 144; symbol++)
+            lengths[symbol] = 8;
+        for (; symbol < 256; symbol++)
+            lengths[symbol] = 9;
+        for (; symbol < 280; symbol++)
+            lengths[symbol] = 7;
+        for (; symbol < FIXLCODES; symbol++)
+            lengths[symbol] = 8;
+        construct(&lencode, lengths, FIXLCODES);
+
+        /* distance table */
+        for (symbol = 0; symbol < MAXDCODES; symbol++)
+            lengths[symbol] = 5;
+        construct(&distcode, lengths, MAXDCODES);
+
+        /* do this just once */
+        virgin = 0;
+    }
+
+    /* decode data until end-of-block code */
+    return codes(s, &lencode, &distcode);
+}
+
+/*
+ * Process a dynamic codes block.
+ *
+ * Format notes:
+ *
+ * - A dynamic block starts with a description of the literal/length and
+ *   distance codes for that block.  New dynamic blocks allow the compressor to
+ *   rapidly adapt to changing data with new codes optimized for that data.
+ *
+ * - The codes used by the deflate format are "canonical", which means that
+ *   the actual bits of the codes are generated in an unambiguous way simply
+ *   from the number of bits in each code.  Therefore the code descriptions
+ *   are simply a list of code lengths for each symbol.
+ *
+ * - The code lengths are stored in order for the symbols, so lengths are
+ *   provided for each of the literal/length symbols, and for each of the
+ *   distance symbols.
+ *
+ * - If a symbol is not used in the block, this is represented by a zero as
+ *   as the code length.  This does not mean a zero-length code, but rather
+ *   that no code should be created for this symbol.  There is no way in the
+ *   deflate format to represent a zero-length code.
+ *
+ * - The maximum number of bits in a code is 15, so the possible lengths for
+ *   any code are 1..15.
+ *
+ * - The fact that a length of zero is not permitted for a code has an
+ *   interesting consequence.  Normally if only one symbol is used for a given
+ *   code, then in fact that code could be represented with zero bits.  However
+ *   in deflate, that code has to be at least one bit.  So for example, if
+ *   only a single distance base symbol appears in a block, then it will be
+ *   represented by a single code of length one, in particular one 0 bit.  This
+ *   is an incomplete code, since if a 1 bit is received, it has no meaning,
+ *   and should result in an error.  So incomplete distance codes of one symbol
+ *   should be permitted, and the receipt of invalid codes should be handled.
+ *
+ * - It is also possible to have a single literal/length code, but that code
+ *   must be the end-of-block code, since every dynamic block has one.  This
+ *   is not the most efficient way to create an empty block (an empty fixed
+ *   block is fewer bits), but it is allowed by the format.  So incomplete
+ *   literal/length codes of one symbol should also be permitted.
+ *
+ * - If there are only literal codes and no lengths, then there are no distance
+ *   codes.  This is represented by one distance code with zero bits.
+ *
+ * - The list of up to 286 length/literal lengths and up to 30 distance lengths
+ *   are themselves compressed using Huffman codes and run-length encoding.  In
+ *   the list of code lengths, a 0 symbol means no code, a 1..15 symbol means
+ *   that length, and the symbols 16, 17, and 18 are run-length instructions.
+ *   Each of 16, 17, and 18 are follwed by extra bits to define the length of
+ *   the run.  16 copies the last length 3 to 6 times.  17 represents 3 to 10
+ *   zero lengths, and 18 represents 11 to 138 zero lengths.  Unused symbols
+ *   are common, hence the special coding for zero lengths.
+ *
+ * - The symbols for 0..18 are Huffman coded, and so that code must be
+ *   described first.  This is simply a sequence of up to 19 three-bit values
+ *   representing no code (0) or the code length for that symbol (1..7).
+ *
+ * - A dynamic block starts with three fixed-size counts from which is computed
+ *   the number of literal/length code lengths, the number of distance code
+ *   lengths, and the number of code length code lengths (ok, you come up with
+ *   a better name!) in the code descriptions.  For the literal/length and
+ *   distance codes, lengths after those provided are considered zero, i.e. no
+ *   code.  The code length code lengths are received in a permuted order (see
+ *   the order[] array below) to make a short code length code length list more
+ *   likely.  As it turns out, very short and very long codes are less likely
+ *   to be seen in a dynamic code description, hence what may appear initially
+ *   to be a peculiar ordering.
+ *
+ * - Given the number of literal/length code lengths (nlen) and distance code
+ *   lengths (ndist), then they are treated as one long list of nlen + ndist
+ *   code lengths.  Therefore run-length coding can and often does cross the
+ *   boundary between the two sets of lengths.
+ *
+ * - So to summarize, the code description at the start of a dynamic block is
+ *   three counts for the number of code lengths for the literal/length codes,
+ *   the distance codes, and the code length codes.  This is followed by the
+ *   code length code lengths, three bits each.  This is used to construct the
+ *   code length code which is used to read the remainder of the lengths.  Then
+ *   the literal/length code lengths and distance lengths are read as a single
+ *   set of lengths using the code length codes.  Codes are constructed from
+ *   the resulting two sets of lengths, and then finally you can start
+ *   decoding actual compressed data in the block.
+ *
+ * - For reference, a "typical" size for the code description in a dynamic
+ *   block is around 80 bytes.
+ */
+local int dynamic(struct state* s)
+{
+    int nlen, ndist, ncode;                         /* number of lengths in descriptor */
+    int index;                                      /* index of lengths[] */
+    int err;                                        /* construct() return value */
+    short lengths[MAXCODES];                        /* descriptor code lengths */
+    short lencnt[MAXBITS + 1], lensym[MAXLCODES];   /* lencode memory */
+    short distcnt[MAXBITS + 1], distsym[MAXDCODES]; /* distcode memory */
+    struct huffman lencode, distcode;               /* length and distance codes */
+    static const short order[19] =                  /* permutation of code length codes */
+        { 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15 };
+
+    /* construct lencode and distcode */
+    lencode.count = lencnt;
+    lencode.symbol = lensym;
+    distcode.count = distcnt;
+    distcode.symbol = distsym;
+
+    /* get number of lengths in each table, check lengths */
+    nlen = bits(s, 5) + 257;
+    ndist = bits(s, 5) + 1;
+    ncode = bits(s, 4) + 4;
+    if (nlen > MAXLCODES || ndist > MAXDCODES)
+        return -3; /* bad counts */
+
+    /* read code length code lengths (really), missing lengths are zero */
+    for (index = 0; index < ncode; index++)
+        lengths[order[index]] = bits(s, 3);
+    for (; index < 19; index++)
+        lengths[order[index]] = 0;
+
+    /* build huffman table for code lengths codes (use lencode temporarily) */
+    err = construct(&lencode, lengths, 19);
+    if (err != 0) /* require complete code set here */
+        return -4;
+
+    /* read length/literal and distance code length tables */
+    index = 0;
+    while (index < nlen + ndist) {
+        int symbol; /* decoded value */
+        int len;    /* last length to repeat */
+
+        symbol = decode(s, &lencode);
+        if (symbol < 0)
+            return symbol; /* invalid symbol */
+        if (symbol < 16)   /* length in 0..15 */
+            lengths[index++] = symbol;
+        else {                  /* repeat instruction */
+            len = 0;            /* assume repeating zeros */
+            if (symbol == 16) { /* repeat last length 3..6 times */
+                if (index == 0)
+                    return -5;            /* no last length! */
+                len = lengths[index - 1]; /* last length */
+                symbol = 3 + bits(s, 2);
+            } else if (symbol == 17) /* repeat zero 3..10 times */
+                symbol = 3 + bits(s, 3);
+            else /* == 18, repeat zero 11..138 times */
+                symbol = 11 + bits(s, 7);
+            if (index + symbol > nlen + ndist)
+                return -6;   /* too many lengths! */
+            while (symbol--) /* repeat last or zero symbol times */
+                lengths[index++] = len;
+        }
+    }
+
+    /* check for end-of-block code -- there better be one! */
+    if (lengths[256] == 0)
+        return -9;
+
+    /* build huffman table for literal/length codes */
+    err = construct(&lencode, lengths, nlen);
+    if (err && (err < 0 || nlen != lencode.count[0] + lencode.count[1]))
+        return -7; /* incomplete code ok only for single length 1 code */
+
+    /* build huffman table for distance codes */
+    err = construct(&distcode, lengths + nlen, ndist);
+    if (err && (err < 0 || ndist != distcode.count[0] + distcode.count[1]))
+        return -8; /* incomplete code ok only for single length 1 code */
+
+    /* decode data until end-of-block code */
+    return codes(s, &lencode, &distcode);
+}
+
+/*
+ * Inflate source to dest.  On return, destlen and sourcelen are updated to the
+ * size of the uncompressed data and the size of the deflate data respectively.
+ * On success, the return value of puff() is zero.  If there is an error in the
+ * source data, i.e. it is not in the deflate format, then a negative value is
+ * returned.  If there is not enough input available or there is not enough
+ * output space, then a positive error is returned.  In that case, destlen and
+ * sourcelen are not updated to facilitate retrying from the beginning with the
+ * provision of more input data or more output space.  In the case of invalid
+ * inflate data (a negative error), the dest and source pointers are updated to
+ * facilitate the debugging of deflators.
+ *
+ * puff() also has a mode to determine the size of the uncompressed output with
+ * no output written.  For this dest must be (unsigned char *)0.  In this case,
+ * the input value of *destlen is ignored, and on return *destlen is set to the
+ * size of the uncompressed output.
+ *
+ * The return codes are:
+ *
+ *   2:  available inflate data did not terminate
+ *   1:  output space exhausted before completing inflate
+ *   0:  successful inflate
+ *  -1:  invalid block type (type == 3)
+ *  -2:  stored block length did not match one's complement
+ *  -3:  dynamic block code description: too many length or distance codes
+ *  -4:  dynamic block code description: code lengths codes incomplete
+ *  -5:  dynamic block code description: repeat lengths with no first length
+ *  -6:  dynamic block code description: repeat more than specified lengths
+ *  -7:  dynamic block code description: invalid literal/length code lengths
+ *  -8:  dynamic block code description: invalid distance code lengths
+ *  -9:  dynamic block code description: missing end-of-block code
+ * -10:  invalid literal/length or distance code in fixed or dynamic block
+ * -11:  distance is too far back in fixed or dynamic block
+ *
+ * Format notes:
+ *
+ * - Three bits are read for each block to determine the kind of block and
+ *   whether or not it is the last block.  Then the block is decoded and the
+ *   process repeated if it was not the last block.
+ *
+ * - The leftover bits in the last byte of the deflate data after the last
+ *   block (if it was a fixed or dynamic block) are undefined and have no
+ *   expected values to check.
+ */
+int puff(unsigned char* dest,    /* pointer to destination pointer */
+    unsigned long* destlen,      /* amount of output space */
+    const unsigned char* source, /* pointer to source data pointer */
+    unsigned long* sourcelen)    /* amount of input available */
+{
+    struct state s; /* input/output state */
+    int last, type; /* block information */
+    int err;        /* return value */
+
+    /* initialize output state */
+    s.out = dest;
+    s.outlen = *destlen; /* ignored if dest is NIL */
+    s.outcnt = 0;
+
+    /* initialize input state */
+    s.in = source;
+    s.inlen = *sourcelen;
+    s.incnt = 0;
+    s.bitbuf = 0;
+    s.bitcnt = 0;
+
+    /* return if bits() or decode() tries to read past available input */
+    if (setjmp(s.env) != 0) /* if came back here via longjmp() */
+        err = 2;            /* then skip do-loop, return error */
+    else {
+        /* process blocks until last block or error */
+        do {
+            last = bits(&s, 1);                                                                      /* one if last block */
+            type = bits(&s, 2);                                                                      /* block type 0..3 */
+            err = type == 0 ? stored(&s) : (type == 1 ? fixed(&s) : (type == 2 ? dynamic(&s) : -1)); /* type == 3, invalid */
+            if (err != 0)
+                break; /* return with error */
+        } while (!last);
+    }
+
+    /* update the lengths and return */
+    if (err <= 0) {
+        *destlen = s.outcnt;
+        *sourcelen = s.incnt;
+    }
+    return err;
+}

Userland/Libraries/LibCore/puff.h

@@ -0,0 +1,44 @@
+#pragma once
+
+/* puff.h
+  Copyright (C) 2002-2013 Mark Adler, all rights reserved
+  version 2.3, 21 Jan 2013
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the author be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+
+  Mark Adler    madler@alumni.caltech.edu
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * See puff.c for purpose and usage.
+ */
+#ifndef NIL
+#    define NIL ((unsigned char*)0) /* for no output option */
+#endif
+
+int puff(unsigned char* dest,    /* pointer to destination pointer */
+    unsigned long* destlen,      /* amount of output space */
+    const unsigned char* source, /* pointer to source data pointer */
+    unsigned long* sourcelen);   /* amount of input available */
+
+#ifdef __cplusplus
+}
+#endif