107 lines
4.9 KiB
C++
107 lines
4.9 KiB
C++
/*
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* Copyright (C) 2012 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ANDROID_AUDIO_MONO_PIPE_H
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#define ANDROID_AUDIO_MONO_PIPE_H
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#include <time.h>
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#include "NBAIO.h"
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#include <media/SingleStateQueue.h>
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namespace android {
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typedef SingleStateQueue<ExtendedTimestamp> ExtendedTimestampSingleStateQueue;
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// MonoPipe is similar to Pipe except:
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// - supports only a single reader, called MonoPipeReader
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// - write() cannot overrun; instead it will return a short actual count if insufficient space
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// - write() can optionally block if the pipe is full
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// Like Pipe, it is not multi-thread safe for either writer or reader
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// but writer and reader can be different threads.
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class MonoPipe : public NBAIO_Sink {
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friend class MonoPipeReader;
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public:
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// reqFrames will be rounded up to a power of 2, and all slots are available. Must be >= 2.
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// Note: whatever shares this object with another thread needs to do so in an SMP-safe way (like
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// creating it the object before creating the other thread, or storing the object with a
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// release_store). Otherwise the other thread could see a partially-constructed object.
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MonoPipe(size_t reqFrames, const NBAIO_Format& format, bool writeCanBlock = false);
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virtual ~MonoPipe();
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// NBAIO_Port interface
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//virtual ssize_t negotiate(const NBAIO_Format offers[], size_t numOffers,
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// NBAIO_Format counterOffers[], size_t& numCounterOffers);
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//virtual NBAIO_Format format() const;
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// NBAIO_Sink interface
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//virtual int64_t framesWritten() const;
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//virtual int64_t framesUnderrun() const;
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//virtual int64_t underruns() const;
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virtual ssize_t availableToWrite() const;
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virtual ssize_t write(const void *buffer, size_t count);
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//virtual ssize_t writeVia(writeVia_t via, size_t total, void *user, size_t block);
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// average number of frames present in the pipe under normal conditions.
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// See throttling mechanism in MonoPipe::write()
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size_t getAvgFrames() const { return mSetpoint; }
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void setAvgFrames(size_t setpoint);
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size_t maxFrames() const { return mMaxFrames; }
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// Set the shutdown state for the write side of a pipe.
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// This may be called by an unrelated thread. When shutdown state is 'true',
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// a write that would otherwise block instead returns a short transfer count.
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// There is no guarantee how long it will take for the shutdown to be recognized,
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// but it will not be an unbounded amount of time.
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// The state can be restored to normal by calling shutdown(false).
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void shutdown(bool newState = true);
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// Return true if the write side of a pipe is currently shutdown.
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bool isShutdown();
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// Return NO_ERROR if there is a timestamp available
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status_t getTimestamp(ExtendedTimestamp ×tamp);
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private:
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const size_t mReqFrames; // as requested in constructor, unrounded
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const size_t mMaxFrames; // always a power of 2
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void * const mBuffer;
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// mFront and mRear will never be separated by more than mMaxFrames.
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// 32-bit overflow is possible if the pipe is active for a long time, but if that happens it's
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// safe because we "&" with (mMaxFrames-1) at end of computations to calculate a buffer index.
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volatile int32_t mFront; // written by reader with android_atomic_release_store,
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// read by writer with android_atomic_acquire_load
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volatile int32_t mRear; // written by writer with android_atomic_release_store,
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// read by reader with android_atomic_acquire_load
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bool mWriteTsValid; // whether mWriteTs is valid
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struct timespec mWriteTs; // time that the previous write() completed
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size_t mSetpoint; // target value for pipe fill depth
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const bool mWriteCanBlock; // whether write() should block if the pipe is full
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bool mIsShutdown; // whether shutdown(true) was called, no barriers are needed
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ExtendedTimestampSingleStateQueue::Shared mTimestampShared;
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ExtendedTimestampSingleStateQueue::Mutator mTimestampMutator;
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ExtendedTimestampSingleStateQueue::Observer mTimestampObserver;
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};
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} // namespace android
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#endif // ANDROID_AUDIO_MONO_PIPE_H
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