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      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 <audio_utils/fifo.h>
     21 #include <media/nbaio/NBAIO.h>
     22 
     23 namespace android {
     24 
     25 // Pipe is multi-thread safe for readers (see PipeReader), but safe for only a single writer thread.
     26 // It cannot UNDERRUN on write, unless we allow designation of a master reader that provides the
     27 // time-base. Readers can be added and removed dynamically, and it's OK to have no readers.
     28 class Pipe : public NBAIO_Sink {
     29 
     30     friend class PipeReader;
     31 
     32 public:
     33     // maxFrames will be rounded up to a power of 2, and all slots are available. Must be >= 2.
     34     // buffer is an optional parameter specifying the virtual address of the pipe buffer,
     35     // which must be of size roundup(maxFrames) * Format_frameSize(format) bytes.
     36     Pipe(size_t maxFrames, const NBAIO_Format& format, void *buffer = NULL);
     37 
     38     // If a buffer was specified in the constructor, it is not automatically freed by destructor.
     39     virtual ~Pipe();
     40 
     41     // NBAIO_Port interface
     42 
     43     //virtual ssize_t negotiate(const NBAIO_Format offers[], size_t numOffers,
     44     //                          NBAIO_Format counterOffers[], size_t& numCounterOffers);
     45     //virtual NBAIO_Format format() const;
     46 
     47     // NBAIO_Sink interface
     48 
     49     //virtual int64_t framesWritten() const;
     50     //virtual int64_t framesUnderrun() const;
     51     //virtual int64_t underruns() const;
     52 
     53     // The write side of a pipe permits overruns; flow control is the caller's responsibility.
     54     // It doesn't return +infinity because that would guarantee an overrun.
     55     virtual ssize_t availableToWrite() { return mMaxFrames; }
     56 
     57     virtual ssize_t write(const void *buffer, size_t count);
     58     //virtual ssize_t writeVia(writeVia_t via, size_t total, void *user, size_t block);
     59 
     60 private:
     61     const size_t    mMaxFrames;     // always a power of 2
     62     void * const    mBuffer;
     63     audio_utils_fifo        mFifo;
     64     audio_utils_fifo_writer mFifoWriter;
     65     volatile int32_t mReaders;      // number of PipeReader clients currently attached to this Pipe
     66     const bool      mFreeBufferInDestructor;
     67 };
     68 
     69 }   // namespace android
     70 
     71 #endif  // ANDROID_AUDIO_PIPE_H
     72