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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Atomic.h>
#include <AK/StdLibExtras.h>
#include <Kernel/FileSystem/FIFO.h>
#include <Kernel/FileSystem/FileDescription.h>
#include <Kernel/Locking/Mutex.h>
#include <Kernel/Process.h>
#include <Kernel/Thread.h>
namespace Kernel {
static Atomic<int> s_next_fifo_id = 1;
RefPtr<FIFO> FIFO::try_create(uid_t uid)
{
auto buffer = DoubleBuffer::try_create();
if (buffer)
return adopt_ref_if_nonnull(new (nothrow) FIFO(uid, buffer.release_nonnull()));
return {};
}
KResultOr<NonnullRefPtr<FileDescription>> FIFO::open_direction(FIFO::Direction direction)
{
auto description = FileDescription::create(*this);
if (!description.is_error()) {
attach(direction);
description.value()->set_fifo_direction({}, direction);
}
return description;
}
KResultOr<NonnullRefPtr<FileDescription>> FIFO::open_direction_blocking(FIFO::Direction direction)
{
MutexLocker locker(m_open_lock);
auto description = open_direction(direction);
if (description.is_error())
return description;
if (direction == Direction::Reader) {
m_read_open_queue.wake_all();
if (m_writers == 0) {
locker.unlock();
m_write_open_queue.wait_forever("FIFO");
locker.lock();
}
}
if (direction == Direction::Writer) {
m_write_open_queue.wake_all();
if (m_readers == 0) {
locker.unlock();
m_read_open_queue.wait_forever("FIFO");
locker.lock();
}
}
return description;
}
FIFO::FIFO(uid_t uid, NonnullOwnPtr<DoubleBuffer> buffer)
: m_buffer(move(buffer))
, m_uid(uid)
{
m_fifo_id = ++s_next_fifo_id;
// Use the same block condition for read and write
m_buffer->set_unblock_callback([this]() {
evaluate_block_conditions();
});
}
FIFO::~FIFO()
{
}
void FIFO::attach(Direction direction)
{
if (direction == Direction::Reader) {
++m_readers;
} else if (direction == Direction::Writer) {
++m_writers;
}
evaluate_block_conditions();
}
void FIFO::detach(Direction direction)
{
if (direction == Direction::Reader) {
VERIFY(m_readers);
--m_readers;
} else if (direction == Direction::Writer) {
VERIFY(m_writers);
--m_writers;
}
evaluate_block_conditions();
}
bool FIFO::can_read(const FileDescription&, size_t) const
{
return !m_buffer->is_empty() || !m_writers;
}
bool FIFO::can_write(const FileDescription&, size_t) const
{
return m_buffer->space_for_writing() || !m_readers;
}
KResultOr<size_t> FIFO::read(FileDescription& fd, u64, UserOrKernelBuffer& buffer, size_t size)
{
if (m_buffer->is_empty()) {
if (!m_writers)
return 0;
if (m_writers && !fd.is_blocking())
return EAGAIN;
}
return m_buffer->read(buffer, size);
}
KResultOr<size_t> FIFO::write(FileDescription& fd, u64, const UserOrKernelBuffer& buffer, size_t size)
{
if (!m_readers) {
Thread::current()->send_signal(SIGPIPE, &Process::current());
return EPIPE;
}
if (!fd.is_blocking() && m_buffer->space_for_writing() == 0)
return EAGAIN;
return m_buffer->write(buffer, size);
}
String FIFO::absolute_path(const FileDescription&) const
{
return String::formatted("fifo:{}", m_fifo_id);
}
KResult FIFO::stat(::stat& st) const
{
memset(&st, 0, sizeof(st));
st.st_mode = S_IFIFO;
return KSuccess;
}
}
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