Saving a file in chunks using a buffer

save.m

ALAssetRepresentation *video = [asset defaultRepresentation];
NSUInteger chunkSize = 100 * 1024;
uint8_t *buffer = malloc(chunkSize * sizeof(uint8_t));

long length = [video size];

NSFileHandle *file = [NSFileHandle fileHandleForWritingAtPath: videoPath];
if(file == nil) {
    [[NSFileManager defaultManager] createFileAtPath:videoPath contents:nil attributes:nil];
    file = [NSFileHandle fileHandleForWritingAtPath:videoPath];
}

NSUInteger offset = 0;
do {
    NSUInteger bytesCopied = [video getBytes:buffer fromOffset:offset length:chunkSize error:nil];
    offset += bytesCopied;
    NSData *data = [[NSData alloc] initWithBytes:buffer length:bytesCopied];
    [file writeData:data];
} while (offset < length);
[file closeFile];
free(buffer);
buffer = NULL;