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141 lines
3.4 KiB
C++
141 lines
3.4 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Atomic.h>
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#include <AK/StdLibExtras.h>
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#include <Kernel/FileSystem/FIFO.h>
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#include <Kernel/FileSystem/OpenFileDescription.h>
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#include <Kernel/Locking/Mutex.h>
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#include <Kernel/Tasks/Process.h>
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#include <Kernel/Tasks/Thread.h>
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namespace Kernel {
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static Atomic<int> s_next_fifo_id = 1;
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ErrorOr<NonnullRefPtr<FIFO>> FIFO::try_create(UserID uid)
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{
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auto buffer = TRY(DoubleBuffer::try_create("FIFO: Buffer"sv));
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return adopt_nonnull_ref_or_enomem(new (nothrow) FIFO(uid, move(buffer)));
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}
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ErrorOr<NonnullRefPtr<OpenFileDescription>> FIFO::open_direction(FIFO::Direction direction)
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{
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auto description = TRY(OpenFileDescription::try_create(*this));
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if (direction == Direction::Reader) {
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++m_readers;
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} else if (direction == Direction::Writer) {
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++m_writers;
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}
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evaluate_block_conditions();
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description->set_fifo_direction({}, direction);
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return description;
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}
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ErrorOr<NonnullRefPtr<OpenFileDescription>> FIFO::open_direction_blocking(FIFO::Direction direction)
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{
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MutexLocker locker(m_open_lock);
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auto description = TRY(open_direction(direction));
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if (direction == Direction::Reader) {
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m_read_open_queue.wake_all();
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if (m_writers == 0) {
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locker.unlock();
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m_write_open_queue.wait_forever("FIFO"sv);
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locker.lock();
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}
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}
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if (direction == Direction::Writer) {
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m_write_open_queue.wake_all();
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if (m_readers == 0) {
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locker.unlock();
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m_read_open_queue.wait_forever("FIFO"sv);
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locker.lock();
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}
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}
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return description;
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}
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FIFO::FIFO(UserID uid, NonnullOwnPtr<DoubleBuffer> buffer)
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: m_buffer(move(buffer))
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, m_uid(uid)
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{
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m_fifo_id = ++s_next_fifo_id;
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// Use the same block condition for read and write
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m_buffer->set_unblock_callback([this]() {
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evaluate_block_conditions();
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});
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}
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FIFO::~FIFO() = default;
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void FIFO::detach(OpenFileDescription& description)
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{
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File::detach(description);
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auto direction = description.fifo_direction();
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if (direction == Direction::Reader) {
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VERIFY(m_readers);
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--m_readers;
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} else if (direction == Direction::Writer) {
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VERIFY(m_writers);
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--m_writers;
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}
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evaluate_block_conditions();
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}
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bool FIFO::can_read(OpenFileDescription const&, u64) const
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{
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return !m_buffer->is_empty() || !m_writers;
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}
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bool FIFO::can_write(OpenFileDescription const&, u64) const
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{
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return m_buffer->space_for_writing() || !m_readers;
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}
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ErrorOr<size_t> FIFO::read(OpenFileDescription& fd, u64, UserOrKernelBuffer& buffer, size_t size)
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{
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if (m_buffer->is_empty()) {
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if (!m_writers)
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return 0;
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if (!fd.is_blocking())
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return EAGAIN;
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}
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return m_buffer->read(buffer, size);
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}
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ErrorOr<size_t> FIFO::write(OpenFileDescription& fd, u64, UserOrKernelBuffer const& buffer, size_t size)
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{
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if (!m_readers)
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return EPIPE;
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if (!fd.is_blocking() && m_buffer->space_for_writing() == 0)
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return EAGAIN;
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return m_buffer->write(buffer, size);
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}
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ErrorOr<NonnullOwnPtr<KString>> FIFO::pseudo_path(OpenFileDescription const&) const
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{
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return KString::formatted("fifo:{}", m_fifo_id);
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}
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ErrorOr<struct stat> FIFO::stat() const
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{
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struct stat st = {};
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st.st_mode = S_IFIFO;
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return st;
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}
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}
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