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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.
*/
#ifndef SHARED_PIPE_CONSUMER_HXX
#define SHARED_PIPE_CONSUMER_HXX
#include "util/Compiler.h"
#include <cassert>
struct MusicChunk;
class MusicPipe;
/**
* A utility class which helps with consuming data from a #MusicPipe.
*
* This class is intentionally not thread-safe. Since it is designed
* to be called from two distinct threads (PlayerThread=feeder and
* OutputThread=consumer), all methods must be called with a mutex
* locked to serialize access. Usually, this is #AudioOutput::mutex.
*/
class SharedPipeConsumer {
/**
* The music pipe which provides music chunks to be played.
*/
const MusicPipe *pipe = nullptr;
/**
* The #MusicChunk which is currently being played. All
* chunks before this one may be returned to the #MusicBuffer,
* because they are not going to be used by this output
* anymore.
*/
const MusicChunk *chunk;
/**
* Has the output finished playing #chunk?
*/
bool consumed;
public:
void Init(const MusicPipe &_pipe) {
pipe = &_pipe;
chunk = nullptr;
}
const MusicPipe &GetPipe() {
assert(pipe != nullptr);
return *pipe;
}
bool IsInitial() {
return chunk == nullptr;
}
void Cancel() {
chunk = nullptr;
}
const MusicChunk *Get() noexcept;
void Consume([[maybe_unused]] const MusicChunk &_chunk) {
assert(chunk != nullptr);
assert(chunk == &_chunk);
consumed = true;
}
gcc_pure
bool IsConsumed(const MusicChunk &_chunk) const noexcept;
void ClearTail([[maybe_unused]] const MusicChunk &_chunk) noexcept {
assert(chunk == &_chunk);
assert(consumed);
chunk = nullptr;
}
};
#endif
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