97425d56e7
[[maybe_unused]] (introduced in C++17) is standard C++. https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused says that this is equivalent to the GNU unused attribute. Signed-off-by: Rosen Penev <rosenp@gmail.com>
97 lines
2.3 KiB
C++
97 lines
2.3 KiB
C++
/*
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* Copyright 2003-2020 The Music Player Daemon Project
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* http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef SHARED_PIPE_CONSUMER_HXX
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#define SHARED_PIPE_CONSUMER_HXX
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#include "util/Compiler.h"
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#include <cassert>
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struct MusicChunk;
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class MusicPipe;
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/**
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* A utility class which helps with consuming data from a #MusicPipe.
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*
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* This class is intentionally not thread-safe. Since it is designed
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* to be called from two distinct threads (PlayerThread=feeder and
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* OutputThread=consumer), all methods must be called with a mutex
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* locked to serialize access. Usually, this is #AudioOutput::mutex.
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*/
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class SharedPipeConsumer {
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/**
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* The music pipe which provides music chunks to be played.
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*/
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const MusicPipe *pipe = nullptr;
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/**
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* The #MusicChunk which is currently being played. All
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* chunks before this one may be returned to the #MusicBuffer,
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* because they are not going to be used by this output
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* anymore.
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*/
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const MusicChunk *chunk;
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/**
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* Has the output finished playing #chunk?
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*/
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bool consumed;
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public:
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void Init(const MusicPipe &_pipe) {
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pipe = &_pipe;
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chunk = nullptr;
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}
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const MusicPipe &GetPipe() {
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assert(pipe != nullptr);
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return *pipe;
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}
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bool IsInitial() {
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return chunk == nullptr;
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}
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void Cancel() {
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chunk = nullptr;
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}
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const MusicChunk *Get() noexcept;
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void Consume([[maybe_unused]] const MusicChunk &_chunk) {
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assert(chunk != nullptr);
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assert(chunk == &_chunk);
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consumed = true;
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}
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gcc_pure
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bool IsConsumed(const MusicChunk &_chunk) const noexcept;
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void ClearTail([[maybe_unused]] const MusicChunk &_chunk) noexcept {
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assert(chunk == &_chunk);
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assert(consumed);
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chunk = nullptr;
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}
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};
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#endif
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