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

A method in a NSData category

- (NSString*)encodeBase64 {    
    static char* alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    unsigned int length = self.length;
    unsigned const char* rawData = self.bytes;

    //empty data = empty output
    if (length == 0) {
        return @"";
    }

    unsigned int outputLength = (((length + 2) / 3) * 4);

    //let's allocate buffer for the output
    char* rawOutput = malloc(outputLength + 1);

    //with each step we get 3 bytes from the input and write 4 bytes to the output
    for (unsigned int i = 0, outputIndex = 0; i < length; i += 3, outputIndex += 4) {
        BOOL triple = NO;
        BOOL quad = NO;

        //get 3 bytes (or only 1 or 2 when we have reached the end of input)
        unsigned int value = rawData[i];
        value <<= 8;

        if (i + 1 < length) {
            value |= rawData[i + 1];
            triple = YES;
        }

        value <<= 8;

        if (i + 2 < length) {
            value |= rawData[i + 2];
            quad = YES;
        }

        //3 * 8 bits written as 4 * 6 bits (indexing the 64 chars of the alphabet)
        //write = if end of input reached
        rawOutput[outputIndex + 3] = (quad) ? alphabet[value & 0x3F] : '=';
        value >>= 6;
        rawOutput[outputIndex + 2] = (triple) ? alphabet[value & 0x3F] : '=';
        value >>= 6;
        rawOutput[outputIndex + 1] = alphabet[value & 0x3F];
        value >>= 6;
        rawOutput[outputIndex] = alphabet[value & 0x3F];
    }

    rawOutput[outputLength] = 0;

    NSString* output = [NSString stringWithCString:rawOutput encoding:NSASCIIStringEncoding];

    free(rawOutput);

    return output;
}