Function CMBlockBufferAppendMemoryBlock 

pub unsafe extern "C" fn CMBlockBufferAppendMemoryBlock(
    theBuffer: CMBlockBufferRef,
    memoryBlock: *mut c_void,
    blockLength: usize,
    blockAllocator: CFAllocatorRef,
    customBlockSource: *const CMBlockBufferCustomBlockSource,
    offsetToData: usize,
    dataLength: usize,
    flags: CMBlockBufferFlags,
) -> OSStatus

Apple SDK function CMBlockBufferAppendMemoryBlock.