HexNSStringFromBytes

gistfile1.m

NSString *HexNSStringFromBytes(uint8_t *bytes, NSUInteger count) {
    char *hexCString = calloc(count * 2 + 1, sizeof(char *));

    static char hexLookup[] = "0123456789abcdef";

    NSMutableString* testString = [NSMutableString string];
    for (int i = 0; i < count; ++i) {
        uint8_t fullByte = bytes[i];

        // each byte converts to two hex characters
        hexCString[2 * i] = hexLookup[fullByte >> 4];          // high-order nibble first
        hexCString[2 * i + 1] = hexLookup[fullByte & 0x0F];    // low-order
        [testString appendFormat:@"%02x", bytes[i]];
    }
    NSString *hexString = [NSString stringWithUTF8String:hexCString];
    free(hexCString);

    assert([hexString isEqualToString:testString]);

    return hexString;
}