Random string generator in ObjC

rand_string.m

#import <Foundation/Foundation.h>
#import <CommonCrypto/CommonCrypto.h>

NSString* randomString(NSUInteger length)
{
    NSMutableData *data = [NSMutableData dataWithLength:length];
    NSInteger result = SecRandomCopyBytes(kSecRandomDefault, length, data.mutableBytes);
    NSLog(@"%ld", (long)result);
    NSMutableString* str = [NSMutableString string];
    for (int i = 0; i < length / 8; i++)
    {
        UInt8 *bytes = (UInt8*)data.bytes;
        const UInt8 ch = bytes[i];
        [str appendFormat:@"0x%02x, ", ch];
    }
    return str;
}

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSLog(@"%@", randomString(256));
    }
    return 0;
}