How to code a circular buffer in an external.
Hey everybody, thanks for the help with my float inlet yesterday!
I am now trying to add a circular buffer to my external. The buffer will need to hold something in the order of 2048 samples.
Now Im thinking I need to create this buffer outside the perform routine as this routine only works in chunks of samples as per the Signal Vector size, right? So where do I create the array to store these samples, in the structure defn or in the new instance routine, or where?
As far as I understand it the array/buffer will need to outside the perform routine so it can store samples from previous Signal Vectors. So i guess this needs to be a global variable that can be accessed from the perform routine, but i guess Im not sure where is the best place to do this code in an MSP external.
Your help is greatly appreciated,
cheers,
enda
I think you should allocate the mem in your dsp function.
Put a float* into your main object, like so:
#define kNumSamplesInCircularBuffer 2048;
typedef struct _MyObjName {
t_pxobject xObj; // requred for msp
int curReadIndex;
int curWriteIndex;
float* circularBuffer;
} MyObjName;
...
and then malloc a buffer and give it to your object like so:
void MyObjName_dsp(MyObjName* inObj, t_signal **sp, short* count) {
//allocate the buffer
circularBuffer = (float*)malloc(sizeof(float) *
kNumSamplesInCircularBuffer);
//initialize the read and write index
curReadIndex = 0;
curWriteIndex = 0;
//initialize the buffer with zeros
bzero(circularBuffer, sizeof(float) * kNumSamplesInCircularBuffer);
}
...
and then free the buffer when you're done.
void MyObjName_free(MyObjName* inObj) {
dsp_free((t_pxobject*) xObj);
free(circularBuffer);
//for paranoia's sake I always zero out my structs after I free any
malloc'd members
bzero(inObj, sizeof(MyObjName));
}
then inside of your process function, just make sure you don't access
outside of the bounds of your buffer.
_Mark