NSData+FILE contains a single function, CKOpenData which allows an NSData object to be manipulated as a FILE stream.
NSMutableData *mutableData = [NSMutableData data];
FILE *stream = CKOpenData(mutableData);
fputs("Hello World!", stream);
fclose(stream);
NSString *string = [[NSString alloc] initWithData:mutableData encoding:NSUTF8StringEncoding];
NSLog(@"%@", string);Hello World!
NSData+FILE is available under the MIT license. See the LICENSE file for more info.