mpd/src/output/plugins/FifoOutputPlugin.cxx

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/*
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* Copyright 2003-2020 The Music Player Daemon Project
* http://www.musicpd.org
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
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#include "FifoOutputPlugin.hxx"
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#include "../OutputAPI.hxx"
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#include "../Timer.hxx"
#include "fs/AllocatedPath.hxx"
#include "fs/FileSystem.hxx"
#include "fs/FileInfo.hxx"
#include "util/Domain.hxx"
#include "util/RuntimeError.hxx"
#include "Log.hxx"
#include "open.h"
#include <sys/stat.h>
#include <errno.h>
#include <unistd.h>
class FifoOutput final : AudioOutput {
const AllocatedPath path;
std::string path_utf8;
int input = -1;
int output = -1;
bool created = false;
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Timer *timer;
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public:
FifoOutput(const ConfigBlock &block);
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~FifoOutput() {
CloseFifo();
}
static AudioOutput *Create(EventLoop &,
const ConfigBlock &block) {
return new FifoOutput(block);
}
private:
void Create();
void Check();
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void Delete();
void OpenFifo();
void CloseFifo();
void Open(AudioFormat &audio_format) override;
void Close() noexcept override;
std::chrono::steady_clock::duration Delay() const noexcept override;
size_t Play(const void *chunk, size_t size) override;
void Cancel() noexcept override;
};
static constexpr Domain fifo_output_domain("fifo_output");
FifoOutput::FifoOutput(const ConfigBlock &block)
:AudioOutput(0),
path(block.GetPath("path"))
{
if (path.IsNull())
throw std::runtime_error("No \"path\" parameter specified");
path_utf8 = path.ToUTF8();
OpenFifo();
}
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inline void
FifoOutput::Delete()
{
FormatDebug(fifo_output_domain,
"Removing FIFO \"%s\"", path_utf8.c_str());
try {
RemoveFile(path);
} catch (...) {
LogError(std::current_exception(), "Could not remove FIFO");
return;
}
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created = false;
}
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void
FifoOutput::CloseFifo()
{
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if (input >= 0) {
close(input);
input = -1;
}
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if (output >= 0) {
close(output);
output = -1;
}
FileInfo fi;
if (created && GetFileInfo(path, fi))
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Delete();
}
inline void
FifoOutput::Create()
{
if (!MakeFifo(path, 0666))
throw FormatErrno("Couldn't create FIFO \"%s\"",
path_utf8.c_str());
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created = true;
}
inline void
FifoOutput::Check()
{
struct stat st;
if (!StatFile(path, st)) {
if (errno == ENOENT) {
/* Path doesn't exist */
Create();
return;
}
throw FormatErrno("Failed to stat FIFO \"%s\"",
path_utf8.c_str());
}
if (!S_ISFIFO(st.st_mode))
throw FormatRuntimeError("\"%s\" already exists, but is not a FIFO",
path_utf8.c_str());
}
inline void
FifoOutput::OpenFifo()
try {
Check();
input = OpenFile(path, O_RDONLY|O_NONBLOCK|O_BINARY, 0).Steal();
if (input < 0)
throw FormatErrno("Could not open FIFO \"%s\" for reading",
path_utf8.c_str());
output = OpenFile(path, O_WRONLY|O_NONBLOCK|O_BINARY, 0).Steal();
if (output < 0)
throw FormatErrno("Could not open FIFO \"%s\" for writing",
path_utf8.c_str());
} catch (...) {
CloseFifo();
throw;
}
void
FifoOutput::Open(AudioFormat &audio_format)
{
timer = new Timer(audio_format);
}
void
FifoOutput::Close() noexcept
{
delete timer;
}
void
FifoOutput::Cancel() noexcept
{
timer->Reset();
ssize_t bytes;
do {
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char buffer[16384];
bytes = read(input, buffer, sizeof(buffer));
} while (bytes > 0 && errno != EINTR);
if (bytes < 0 && errno != EAGAIN) {
FormatErrno(fifo_output_domain,
"Flush of FIFO \"%s\" failed",
path_utf8.c_str());
}
}
std::chrono::steady_clock::duration
FifoOutput::Delay() const noexcept
{
return timer->IsStarted()
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? timer->GetDelay()
: std::chrono::steady_clock::duration::zero();
}
size_t
FifoOutput::Play(const void *chunk, size_t size)
{
if (!timer->IsStarted())
timer->Start();
timer->Add(size);
while (true) {
ssize_t bytes = write(output, chunk, size);
if (bytes > 0)
return (size_t)bytes;
if (bytes < 0) {
switch (errno) {
case EAGAIN:
/* The pipe is full, so empty it */
Cancel();
continue;
case EINTR:
continue;
}
throw FormatErrno("Failed to write to FIFO %s",
path_utf8.c_str());
}
}
}
const struct AudioOutputPlugin fifo_output_plugin = {
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"fifo",
nullptr,
&FifoOutput::Create,
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nullptr,
};