How to use CARingBuffer class in an iOS (iPhone, iPad) project? - iphone

Question

I'm currently trying to create an iOS audio project and I need to use the CARingBuffer class available in the Extras/CoreAudio/PublicUtility folder of XCode.
The problem is when I include the CARingBuffer.h in the header of my viewController and I declare a CARingBuffer object, I receive 4 compile errors.
To reproduce my problem it's pretty simple. Just create a new view based application and try to #include "CARingBuffer.h" in the header of your viewController.
Here's the content of my testViewController.h :
#import <UIKit/UIKit.h>
#include "CARingBuffer.h"
#interface testViewController : UIViewController {
}
#end
Here's the content of my testViewController.m :
#import "testViewController.h"
#implementation testViewController
- (void)dealloc
{
[super dealloc];
}
- (void)didReceiveMemoryWarning
{
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
#pragma mark - View lifecycle
/*
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad
{
[super viewDidLoad];
}
*/
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
#end
Bellow the 4 compile errors located (strangely) in the CARingBuffer according to XCode 4 :
1) Initializer element is not a constant on line :
const UInt32 kGeneralRingTimeBoundsQueueMask = kGeneralRingTimeBoundsQueueSize - 1;
2) Expected ';' after top level declarator, Expected '='... or 'atribute' before 'CARingBuffer' :
class CARingBuffer {
3) Initializer element is not a constant on line :
const UInt32 kGeneralRingTimeBoundsQueueMask = kGeneralRingTimeBoundsQueueSize - 1;
4) Expected ';' after top level declarator, Expected '='... or 'atribute' before 'CARingBuffer' :
class CARingBuffer {
Thanks in advance for your help.

Answer 1

Also take a look at this alternative

Answer 2

You need to rename the class that you are including the ring buffer in to be a .mm file.
This tells the compiler to use objective c++ .

Answer 3

You need change your testViewController.m to testViewController.mm because CARingBuffer is c++ class.
About how to use it, here is an extend of CARingBuffer : CARingBufferEx
//header file
#include "CARingBuffer.h"
class CARingBufferEx : public CARingBuffer {
public:
CARingBufferEx();
~CARingBufferEx();
CARingBufferError Store(const AudioBufferList *abl, UInt32 nFrames, SampleTime frameNumber);
CARingBufferError Fetch(AudioBufferList *abl, UInt32 nFrames, SampleTime frameNumber);
private:
SInt64 firstInputSampleTime;
SInt64 firstOutputSampleTime;
SInt64 offset;
};
//Class
#include "CARingBufferEx.h"
#include "stdio.h"
CARingBufferEx::CARingBufferEx():firstInputSampleTime(-1), firstOutputSampleTime(-1), offset(0) {
}
CARingBufferEx::~CARingBufferEx() {
}
CARingBufferError CARingBufferEx::Store(const AudioBufferList *abl, UInt32 nFrames, SampleTime frameNumber) {
if (firstInputSampleTime < 0) {
firstInputSampleTime = frameNumber;
if (firstOutputSampleTime > 0 && offset == 0) {
offset = firstInputSampleTime - firstOutputSampleTime;
}
}
return CARingBuffer::Store(abl, nFrames, frameNumber);
}
CARingBufferError CARingBufferEx::Fetch(AudioBufferList *abl, UInt32 nFrames, SampleTime frameNumber) {
if (firstOutputSampleTime < 0) {
firstOutputSampleTime = frameNumber;
if (firstInputSampleTime > 0 && offset == 0) {
offset = firstInputSampleTime - firstOutputSampleTime;
}
}
return CARingBuffer::Fetch(abl, nFrames, frameNumber + offset);
}
Usage:
CARingBufferEx* _musicMixerRingBuffer;
_musicMixerRingBuffer = new CARingBufferEx();
_musicMixerRingBuffer->Allocate(2, sizeof(AudioUnitSampleType), 1024 * 50);
//1024 is length for one package. and 50 means this buffer contains 50 packages at most.
//store
//ioData is AudioBufferList ,inTimeStamp is AudioTimeStamp
musicMixerRingBuffer->Store(ioData, inNumberFrames, inTimeStamp->mSampleTime);
//Fetch
musicMixerRingBuffer->Fetch(ioData, inNumberFrames, inTimeStamp->mSampleTime);