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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/OpenFileDescription.h>
#include <Kernel/Locking/Mutex.h>
#include <Kernel/Process.h>
#include <Kernel/Thread.h>
namespace Kernel {
static Atomic<int> s_next_fifo_id = 1;
ErrorOr<NonnullRefPtr<FIFO>> FIFO::try_create(UserID uid)
{
auto buffer = TRY(DoubleBuffer::try_create());
return adopt_nonnull_ref_or_enomem(new (nothrow) FIFO(uid, move(buffer)));
}
ErrorOr<NonnullRefPtr<OpenFileDescription>> FIFO::open_direction(FIFO::Direction direction)
{
auto description = TRY(OpenFileDescription::try_create(*this));
attach(direction);
description->set_fifo_direction({}, direction);
return description;
}
ErrorOr<NonnullRefPtr<OpenFileDescription>> FIFO::open_direction_blocking(FIFO::Direction direction)
{
MutexLocker locker(m_open_lock);
auto description = TRY(open_direction(direction));
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(UserID 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() = default;
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 OpenFileDescription&, u64) const
{
return !m_buffer->is_empty() || !m_writers;
}
bool FIFO::can_write(const OpenFileDescription&, u64) const
{
return m_buffer->space_for_writing() || !m_readers;
}
ErrorOr<size_t> FIFO::read(OpenFileDescription& fd, u64, UserOrKernelBuffer& buffer, size_t size)
{
if (m_buffer->is_empty()) {
if (!m_writers)
return 0;
if (!fd.is_blocking())
return EAGAIN;
}
return m_buffer->read(buffer, size);
}
ErrorOr<size_t> FIFO::write(OpenFileDescription& 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);
}
ErrorOr<NonnullOwnPtr<KString>> FIFO::pseudo_path(const OpenFileDescription&) const
{
return KString::formatted("fifo:{}", m_fifo_id);
}
ErrorOr<struct stat> FIFO::stat() const
{
struct stat st = {};
st.st_mode = S_IFIFO;
return st;
}
}
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