PublicUtility/CARingBuffer.h
/* |
File: CARingBuffer.h |
Abstract: Part of CoreAudio Utility Classes |
Version: 1.2.2 |
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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 |
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