Libraries: Move to Userland/Libraries/

Userland/Libraries/LibC/dirent.cpp

@@ -0,0 +1,200 @@
+/*
+ * 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/StdLibExtras.h>
+#include <Kernel/API/Syscall.h>
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+extern "C" {
+
+DIR* opendir(const char* name)
+{
+    int fd = open(name, O_RDONLY | O_DIRECTORY);
+    if (fd == -1)
+        return nullptr;
+    DIR* dirp = (DIR*)malloc(sizeof(DIR));
+    dirp->fd = fd;
+    dirp->buffer = nullptr;
+    dirp->buffer_size = 0;
+    dirp->nextptr = nullptr;
+    return dirp;
+}
+
+int closedir(DIR* dirp)
+{
+    if (!dirp || dirp->fd == -1)
+        return -EBADF;
+    if (dirp->buffer)
+        free(dirp->buffer);
+    int rc = close(dirp->fd);
+    if (rc == 0)
+        dirp->fd = -1;
+    free(dirp);
+    return rc;
+}
+
+struct [[gnu::packed]] sys_dirent {
+    ino_t ino;
+    u8 file_type;
+    size_t namelen;
+    char name[];
+    size_t total_size()
+    {
+        return sizeof(ino_t) + sizeof(u8) + sizeof(size_t) + sizeof(char) * namelen;
+    }
+};
+
+static void create_struct_dirent(sys_dirent* sys_ent, struct dirent* str_ent)
+{
+    str_ent->d_ino = sys_ent->ino;
+    str_ent->d_type = sys_ent->file_type;
+    str_ent->d_off = 0;
+    str_ent->d_reclen = sys_ent->total_size();
+    for (size_t i = 0; i < sys_ent->namelen; ++i)
+        str_ent->d_name[i] = sys_ent->name[i];
+    // FIXME: I think this null termination behavior is not supposed to be here.
+    str_ent->d_name[sys_ent->namelen] = '\0';
+}
+
+static int allocate_dirp_buffer(DIR* dirp)
+{
+    if (dirp->buffer) {
+        return 0;
+    }
+
+    struct stat st;
+    // preserve errno since this could be a reentrant call
+    int old_errno = errno;
+    int rc = fstat(dirp->fd, &st);
+    if (rc < 0) {
+        int new_errno = errno;
+        errno = old_errno;
+        return new_errno;
+    }
+    size_t size_to_allocate = max(st.st_size, static_cast<off_t>(4096));
+    dirp->buffer = (char*)malloc(size_to_allocate);
+    ssize_t nread = syscall(SC_get_dir_entries, dirp->fd, dirp->buffer, size_to_allocate);
+    if (nread < 0) {
+        // uh-oh, the syscall returned an error
+        free(dirp->buffer);
+        dirp->buffer = nullptr;
+        return -nread;
+    }
+    dirp->buffer_size = nread;
+    dirp->nextptr = dirp->buffer;
+    return 0;
+}
+
+dirent* readdir(DIR* dirp)
+{
+    if (!dirp)
+        return nullptr;
+    if (dirp->fd == -1)
+        return nullptr;
+
+    if (int new_errno = allocate_dirp_buffer(dirp)) {
+        // readdir is allowed to mutate errno
+        errno = new_errno;
+        return nullptr;
+    }
+
+    if (dirp->nextptr >= (dirp->buffer + dirp->buffer_size))
+        return nullptr;
+
+    auto* sys_ent = (sys_dirent*)dirp->nextptr;
+    create_struct_dirent(sys_ent, &dirp->cur_ent);
+
+    dirp->nextptr += sys_ent->total_size();
+    return &dirp->cur_ent;
+}
+
+static bool compare_sys_struct_dirent(sys_dirent* sys_ent, struct dirent* str_ent)
+{
+    size_t namelen = min((size_t)256, sys_ent->namelen);
+    // These fields are guaranteed by create_struct_dirent to be the same
+    return sys_ent->ino == str_ent->d_ino
+        && sys_ent->file_type == str_ent->d_type
+        && sys_ent->total_size() == str_ent->d_reclen
+        && strncmp(sys_ent->name, str_ent->d_name, namelen) == 0;
+}
+
+int readdir_r(DIR* dirp, struct dirent* entry, struct dirent** result)
+{
+    if (!dirp || dirp->fd == -1) {
+        *result = nullptr;
+        return EBADF;
+    }
+
+    if (int new_errno = allocate_dirp_buffer(dirp)) {
+        *result = nullptr;
+        return new_errno;
+    }
+
+    // This doesn't care about dirp state; seek until we find the entry.
+    // Unfortunately, we can't just compare struct dirent to sys_dirent, so
+    // manually compare the fields. This seems a bit risky, but could work.
+    auto* buffer = dirp->buffer;
+    auto* sys_ent = (sys_dirent*)buffer;
+    bool found = false;
+    while (!(found || buffer >= dirp->buffer + dirp->buffer_size)) {
+        found = compare_sys_struct_dirent(sys_ent, entry);
+
+        // Make sure if we found one, it's the one after (end of buffer or not)
+        buffer += sys_ent->total_size();
+        sys_ent = (sys_dirent*)buffer;
+    }
+
+    // If we found one, but hit end of buffer, then EOD
+    if (found && buffer >= dirp->buffer + dirp->buffer_size) {
+        *result = nullptr;
+        return 0;
+    }
+    // If we never found a match for entry in buffer, start from the beginning
+    else if (!found) {
+        buffer = dirp->buffer;
+        sys_ent = (sys_dirent*)buffer;
+    }
+
+    *result = entry;
+    create_struct_dirent(sys_ent, entry);
+
+    return 0;
+}
+
+int dirfd(DIR* dirp)
+{
+    ASSERT(dirp);
+    return dirp->fd;
+}
+}