How to Base64 encoding on the iPhone

Question

How do I do Base64 encoding on the iPhone?

I have found a few examples that looked promising, but could never get any of them to work on the phone.

Answer 1

I did my own implementation, where has been removed all checks inside the loop. So on big amount of data, it works faster. You can take it as a basis for own solution.

static char *alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

+ (NSString *)encodeString:(NSString *)data
{
    const char *input = [data cStringUsingEncoding:NSUTF8StringEncoding];
    unsigned long inputLength = [data length];
    unsigned long modulo = inputLength % 3;
    unsigned long outputLength = (inputLength / 3) * 4 + (modulo ? 4 : 0);
    unsigned long j = 0;

    // Do not forget about trailing zero
    unsigned char *output = malloc(outputLength + 1);
    output[outputLength] = 0;

    // Here are no checks inside the loop, so it works much faster than other implementations
    for (unsigned long i = 0; i < inputLength; i += 3) {
        output[j++] = alphabet[ (input[i] & 0xFC) >> 2 ];
        output[j++] = alphabet[ ((input[i] & 0x03) << 4) | ((input[i + 1] & 0xF0) >> 4) ];
        output[j++] = alphabet[ ((input[i + 1] & 0x0F)) << 2 | ((input[i + 2] & 0xC0) >> 6) ];
        output[j++] = alphabet[ (input[i + 2] & 0x3F) ];
    }
    // Padding in the end of encoded string directly depends of modulo
    if (modulo > 0) {
        output[outputLength - 1] = '=';
        if (modulo == 1)
            output[outputLength - 2] = '=';
    }
    NSString *s = [NSString stringWithUTF8String:(const char *)output];
    free(output);
    return s;
}