you should have done something like this:
NSData *_data = // ... whatever
NSMutableString *_string = [NSMutableString stringWithString:@""];
for (int i = 0; i < _data.length; i++) {
unsigned char _byte;
[_data getBytes:&_byte range:NSMakeRange(i, 1)];
if (_byte >= 32 && _byte < 127) {
[_string appendFormat:@"%c", _byte];
} else {
[_string appendFormat:@"[%d]", _byte];
}
}
NSLog(@"%@", _string);