CGDataProvider and callback

Question

Hi,

I am creating a very big buffer (called buffer2 in the code) using CGDataProviderRef with the following code:

-(UIImage *) glToUIImage {
 NSInteger myDataLength = 768 * 1024 * 4;
 // allocate array and read pixels into it.
 GLubyte *buffer = (GLubyte *) malloc(myDataLength);
 glReadPixels(0, 0, 768, 1024, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

 // gl renders "upside down" so swap top to bottom into new array.
 // there's gotta be a better way, but this works.
 GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);
 for(int y = 0; y <1024; y++)
 {
   for(int x = 0; x <768 * 4; x++)
   {
     buffer2[(1023 - y) * 768 * 4 + x] = buffer[y * 4 * 768 + x];
   }
 }

  // make data provider with data.
 CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, &releaseBufferData);

 // prep the ingredients
 int bitsPerComponent = 8;
 int bitsPerPixel = 32;
 int bytesPerRow = 4 * 768;
 CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
 CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
 CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;

 // make the cgimage
 CGImageRef imageRef = CGImageCreate(768, 1024, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);

 // then make the uiimage from that
 UIImage *myImage = [UIImage imageWithCGImage:imageRef];

 free(buffer);
 //[provider autorelease];
 CGDataProviderRelease(provider);
 CGColorSpaceRelease(colorSpaceRef);
 CGImageRelease(imageRef);

 return myImage;
}

I expect CGProvider to call back the releaseBufferData method when it is done with buffer2 so that I can free up the memory it's taken. The code for this method is:

static void releaseBufferData (void *info, const void *data, size_t size){  
 free(data);  
}

However, even though my callback method is called, the memory that data (buffer2) takes is never freed and hence it results in massive memory leaks. What am I doing wrong?