LibC: Implement {f,}getwc()

Userland/Libraries/LibC/bits/stdio_file_implementation.h

@@ -0,0 +1,141 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Types.h>
+#include <LibC/bits/FILE.h>
+#include <LibC/bits/pthread_integration.h>
+#include <sys/types.h>
+
+#pragma once
+
+struct FILE {
+public:
+    FILE(int fd, int mode)
+        : m_fd(fd)
+        , m_mode(mode)
+    {
+        __pthread_mutex_init(&m_mutex, nullptr);
+    }
+    ~FILE();
+
+    static FILE* create(int fd, int mode);
+
+    void setbuf(u8* data, int mode, size_t size) { m_buffer.setbuf(data, mode, size); }
+
+    bool flush();
+    void purge();
+    bool close();
+
+    int fileno() const { return m_fd; }
+    bool eof() const { return m_eof; }
+    int mode() const { return m_mode; }
+    u8 flags() const { return m_flags; }
+
+    int error() const { return m_error; }
+    void clear_err() { m_error = 0; }
+
+    size_t read(u8*, size_t);
+    size_t write(const u8*, size_t);
+
+    bool gets(u8*, size_t);
+    bool ungetc(u8 byte) { return m_buffer.enqueue_front(byte); }
+
+    int seek(off_t offset, int whence);
+    off_t tell();
+
+    pid_t popen_child() { return m_popen_child; }
+    void set_popen_child(pid_t child_pid) { m_popen_child = child_pid; }
+
+    void reopen(int fd, int mode);
+
+    enum Flags : u8 {
+        None = 0,
+        LastRead = 1,
+        LastWrite = 2,
+    };
+
+private:
+    struct Buffer {
+        // A ringbuffer that also transparently implements ungetc().
+    public:
+        ~Buffer();
+
+        int mode() const { return m_mode; }
+        void setbuf(u8* data, int mode, size_t size);
+        // Make sure to call realize() before enqueuing any data.
+        // Dequeuing can be attempted without it.
+        void realize(int fd);
+        void drop();
+
+        bool may_use() const { return m_ungotten || m_mode != _IONBF; }
+        bool is_not_empty() const { return m_ungotten || !m_empty; }
+        size_t buffered_size() const;
+
+        const u8* begin_dequeue(size_t& available_size) const;
+        void did_dequeue(size_t actual_size);
+
+        u8* begin_enqueue(size_t& available_size) const;
+        void did_enqueue(size_t actual_size);
+
+        bool enqueue_front(u8 byte);
+
+    private:
+        // Note: the fields here are arranged this way
+        // to make sizeof(Buffer) smaller.
+        u8* m_data { nullptr };
+        size_t m_capacity { BUFSIZ };
+        size_t m_begin { 0 };
+        size_t m_end { 0 };
+
+        int m_mode { -1 };
+        u8 m_unget_buffer { 0 };
+        bool m_ungotten : 1 { false };
+        bool m_data_is_malloced : 1 { false };
+        // When m_begin == m_end, we want to distinguish whether
+        // the buffer is full or empty.
+        bool m_empty : 1 { true };
+    };
+
+    // Read or write using the underlying fd, bypassing the buffer.
+    ssize_t do_read(u8*, size_t);
+    ssize_t do_write(const u8*, size_t);
+
+    // Read some data into the buffer.
+    bool read_into_buffer();
+    // Flush *some* data from the buffer.
+    bool write_from_buffer();
+
+    void lock();
+    void unlock();
+
+    int m_fd { -1 };
+    int m_mode { 0 };
+    u8 m_flags { Flags::None };
+    int m_error { 0 };
+    bool m_eof { false };
+    pid_t m_popen_child { -1 };
+    Buffer m_buffer;
+    __pthread_mutex_t m_mutex;
+
+    friend class ScopedFileLock;
+};
+
+class ScopedFileLock {
+public:
+    ScopedFileLock(FILE* file)
+        : m_file(file)
+    {
+        m_file->lock();
+    }
+
+    ~ScopedFileLock()
+    {
+        m_file->unlock();
+    }
+
+private:
+    FILE* m_file;
+};