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livetrax/libs/appleutility/CoreAudio/PublicUtility/CARingBuffer.h

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/*
File: CARingBuffer.h
Abstract: Part of CoreAudio Utility Classes
Version: 1.1
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*/
#if !defined(__COREAUDIO_USE_FLAT_INCLUDES__)
#include <CoreAudio/CoreAudioTypes.h>
#else
#include <CoreAudioTypes.h>
#endif
#ifndef CARingBuffer_Header
#define CARingBuffer_Header
enum {
kCARingBufferError_OK = 0,
kCARingBufferError_TooMuch = 3, // fetch start time is earlier than buffer start time and fetch end time is later than buffer end time
kCARingBufferError_CPUOverload = 4 // the reader is unable to get enough CPU cycles to capture a consistent snapshot of the time bounds
};
typedef SInt32 CARingBufferError;
const UInt32 kGeneralRingTimeBoundsQueueSize = 32;
const UInt32 kGeneralRingTimeBoundsQueueMask = kGeneralRingTimeBoundsQueueSize - 1;
class CARingBuffer {
public:
typedef SInt64 SampleTime;
CARingBuffer();
~CARingBuffer();
void Allocate(int nChannels, UInt32 bytesPerFrame, UInt32 capacityFrames);
// capacityFrames will be rounded up to a power of 2
void Deallocate();
CARingBufferError Store(const AudioBufferList *abl, UInt32 nFrames, SampleTime frameNumber);
// Copy nFrames of data into the ring buffer at the specified sample time.
// The sample time should normally increase sequentially, though gaps
// are filled with zeroes. A sufficiently large gap effectively empties
// the buffer before storing the new data.
// If frameNumber is less than the previous frame number, the behavior is undefined.
// Return false for failure (buffer not large enough).
CARingBufferError Fetch(AudioBufferList *abl, UInt32 nFrames, SampleTime frameNumber);
// will alter mNumDataBytes of the buffers
CARingBufferError GetTimeBounds(SampleTime &startTime, SampleTime &endTime);
protected:
int FrameOffset(SampleTime frameNumber) { return (frameNumber & mCapacityFramesMask) * mBytesPerFrame; }
CARingBufferError ClipTimeBounds(SampleTime& startRead, SampleTime& endRead);
// these should only be called from Store.
SampleTime StartTime() const { return mTimeBoundsQueue[mTimeBoundsQueuePtr & kGeneralRingTimeBoundsQueueMask].mStartTime; }
SampleTime EndTime() const { return mTimeBoundsQueue[mTimeBoundsQueuePtr & kGeneralRingTimeBoundsQueueMask].mEndTime; }
void SetTimeBounds(SampleTime startTime, SampleTime endTime);
protected:
Byte ** mBuffers; // allocated in one chunk of memory
int mNumberChannels;
UInt32 mBytesPerFrame; // within one deinterleaved channel
UInt32 mCapacityFrames; // per channel, must be a power of 2
UInt32 mCapacityFramesMask;
UInt32 mCapacityBytes; // per channel
// range of valid sample time in the buffer
typedef struct {
volatile SampleTime mStartTime;
volatile SampleTime mEndTime;
volatile UInt32 mUpdateCounter;
} TimeBounds;
CARingBuffer::TimeBounds mTimeBoundsQueue[kGeneralRingTimeBoundsQueueSize];
UInt32 mTimeBoundsQueuePtr;
};
#endif