1 /* 2 * Copyright (C) 2012 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ANDROID_AUDIO_PIPE_H 18 #define ANDROID_AUDIO_PIPE_H 19 20 #include "NBAIO.h" 21 22 namespace android { 23 24 // Pipe is multi-thread safe for readers (see PipeReader), but safe for only a single writer thread. 25 // It cannot UNDERRUN on write, unless we allow designation of a master reader that provides the 26 // time-base. Readers can be added and removed dynamically, and it's OK to have no readers. 27 class Pipe : public NBAIO_Sink { 28 29 friend class PipeReader; 30 31 public: 32 // maxFrames will be rounded up to a power of 2, and all slots are available. Must be >= 2. 33 Pipe(size_t maxFrames, NBAIO_Format format); 34 virtual ~Pipe(); 35 36 // NBAIO_Port interface 37 38 //virtual ssize_t negotiate(const NBAIO_Format offers[], size_t numOffers, 39 // NBAIO_Format counterOffers[], size_t& numCounterOffers); 40 //virtual NBAIO_Format format() const; 41 42 // NBAIO_Sink interface 43 44 //virtual size_t framesWritten() const; 45 //virtual size_t framesUnderrun() const; 46 //virtual size_t underruns() const; 47 48 // The write side of a pipe permits overruns; flow control is the caller's responsibility. 49 // It doesn't return +infinity because that would guarantee an overrun. availableToWrite()50 virtual ssize_t availableToWrite() const { return mMaxFrames; } 51 52 virtual ssize_t write(const void *buffer, size_t count); 53 //virtual ssize_t writeVia(writeVia_t via, size_t total, void *user, size_t block); 54 55 private: 56 const size_t mMaxFrames; // always a power of 2 57 void * const mBuffer; 58 volatile int32_t mRear; // written by android_atomic_release_store 59 volatile int32_t mReaders; // number of PipeReader clients currently attached to this Pipe 60 }; 61 62 } // namespace android 63 64 #endif // ANDROID_AUDIO_PIPE_H 65