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/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ANDROID_AUDIO_MONO_PIPE_H
#define ANDROID_AUDIO_MONO_PIPE_H
#include <time.h>
#include "NBAIO.h"
namespace android {
// MonoPipe is similar to Pipe except:
// - supports only a single reader, called MonoPipeReader
// - write() cannot overrun; instead it will return a short actual count if insufficient space
// - write() can optionally block if the pipe is full
// Like Pipe, it is not multi-thread safe for either writer or reader
// but writer and reader can be different threads.
class MonoPipe : public NBAIO_Sink {
friend class MonoPipeReader;
public:
// maxFrames will be rounded up to a power of 2, and all slots are available. Must be >= 2.
// Note: whatever shares this object with another thread needs to do so in an SMP-safe way (like
// creating it the object before creating the other thread, or storing the object with a
// release_store). Otherwise the other thread could see a partially-constructed object.
MonoPipe(size_t maxFrames, NBAIO_Format format, bool writeCanBlock = false);
virtual ~MonoPipe();
// NBAIO_Port interface
//virtual ssize_t negotiate(const NBAIO_Format offers[], size_t numOffers,
// NBAIO_Format counterOffers[], size_t& numCounterOffers);
//virtual NBAIO_Format format() const;
// NBAIO_Sink interface
//virtual size_t framesWritten() const;
//virtual size_t framesUnderrun() const;
//virtual size_t underruns() const;
virtual ssize_t availableToWrite() const;
virtual ssize_t write(const void *buffer, size_t count);
//virtual ssize_t writeVia(writeVia_t via, size_t total, void *user, size_t block);
private:
const size_t mMaxFrames; // always a power of 2
void * const mBuffer;
// mFront and mRear will never be separated by more than mMaxFrames.
// 32-bit overflow is possible if the pipe is active for a long time, but if that happens it's
// safe because we "&" with (mMaxFrames-1) at end of computations to calculate a buffer index.
volatile int32_t mFront; // written by reader with android_atomic_release_store,
// read by writer with android_atomic_acquire_load
volatile int32_t mRear; // written by writer with android_atomic_release_store,
// read by reader with android_atomic_acquire_load
const bool mWriteCanBlock; // whether write() should block if the pipe is full
};
} // namespace android
#endif // ANDROID_AUDIO_MONO_PIPE_H
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