79 lines
1.7 KiB
C++
79 lines
1.7 KiB
C++
// SPDX-License-Identifier: GPL-2.0-or-later
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// Copyright The Music Player Daemon Project
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#ifndef SHARED_PIPE_CONSUMER_HXX
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#define SHARED_PIPE_CONSUMER_HXX
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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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constexpr void Init(const MusicPipe &_pipe) noexcept {
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pipe = &_pipe;
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chunk = nullptr;
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}
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constexpr const MusicPipe &GetPipe() noexcept {
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assert(pipe != nullptr);
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return *pipe;
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}
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constexpr bool IsInitial() const noexcept {
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return chunk == nullptr;
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}
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constexpr void Cancel() noexcept {
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chunk = nullptr;
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}
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const MusicChunk *Get() noexcept;
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constexpr void Consume([[maybe_unused]] const MusicChunk &_chunk) noexcept {
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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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[[gnu::pure]]
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bool IsConsumed(const MusicChunk &_chunk) const noexcept;
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constexpr 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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