ladybird/Kernel/FileSystem/FIFO.h

/*
 * 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 <Kernel/DoubleBuffer.h>
#include <Kernel/FileSystem/File.h>
#include <Kernel/Lock.h>
#include <Kernel/UnixTypes.h>
#include <Kernel/WaitQueue.h>

namespace Kernel {

class FileDescription;

class FIFO final : public File {
public:
    enum class Direction : u8 {
        Neither,
        Reader,
        Writer
    };

    static NonnullRefPtr<FIFO> create(uid_t);
    virtual ~FIFO() override;

    uid_t uid() const { return m_uid; }

    NonnullRefPtr<FileDescription> open_direction(Direction);
    NonnullRefPtr<FileDescription> open_direction_blocking(Direction);

    void attach(Direction);
    void detach(Direction);

private:
    // ^File
    virtual KResultOr<size_t> write(FileDescription&, size_t, const u8*, size_t) override;
    virtual KResultOr<size_t> read(FileDescription&, size_t, u8*, size_t) override;
    virtual bool can_read(const FileDescription&, size_t) const override;
    virtual bool can_write(const FileDescription&, size_t) const override;
    virtual String absolute_path(const FileDescription&) const override;
    virtual const char* class_name() const override { return "FIFO"; }
    virtual bool is_fifo() const override { return true; }

    explicit FIFO(uid_t);

    unsigned m_writers { 0 };
    unsigned m_readers { 0 };
    DoubleBuffer m_buffer;

    uid_t m_uid { 0 };

    int m_fifo_id { 0 };

    WaitQueue m_read_open_queue;
    WaitQueue m_write_open_queue;
    Lock m_open_lock;
};

}