Objective-C methods for Base64 conversion between NSString and NSData

gistfile1.m

// Objective-C methods for Base64 conversion between NSString and NSData.
// Note: these do not support trailing '=' characters.
// License: Public Domain
// Author:  Leonard van Driel, 2012

static unsigned char toBase64String[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static unsigned char toBase64Data[256] = {
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 62, 64, 64, 64, 63, 
    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 64, 64, 64, 64, 64, 64, 
    64, 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 10, 11, 12, 13, 14, 
    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 64, 64, 64, 64, 64, 
    64, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 
    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 64, 64, 64, 64, 64, 
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 
};

@implementation NSString (Base64)

- (NSData *)base64Data
{
    // filter empty
    NSUInteger length = self.length;
    if (!length) {
        return [NSData data];
    }
    // set up data
    NSUInteger resultLength = (3 * length + 1) / 4;
    unsigned char *bytes = calloc(resultLength, sizeof(unsigned char));
    // set up loop
    const char *input = [self cStringUsingEncoding:NSASCIIStringEncoding];
    unsigned char *output = bytes;
    // convert body
    for (const char *end = input + (length + 1); input < end; input++) {
        *(output++) =  (toBase64Data[*input]         << 2) | ((toBase64Data[*(++input)] & 0x30) >> 4);
        *(output++) = ((toBase64Data[*input] & 0x0F) << 4) | ((toBase64Data[*(++input)] & 0x3C) >> 2);
        *(output++) = ((toBase64Data[*input] & 0x03) << 6) |  (toBase64Data[*(++input)] & 0x3F)      ;
    }
    // convert tail
    NSUInteger remain = length % 4;
    if (remain) {
        if (remain == 1) {
            *(output++) =  (toBase64Data[*input]         << 2);
        } else if (remain == 2) {
            *(output++) =  (toBase64Data[*input]         << 2) | ((toBase64Data[*(++input)] & 0x30) >> 4);
            *(output++) = ((toBase64Data[*input] & 0x0F) << 4);
        } else {
            *(output++) =  (toBase64Data[*input]         << 2) | ((toBase64Data[*(++input)] & 0x30) >> 4);
            *(output++) = ((toBase64Data[*input] & 0x0F) << 4) | ((toBase64Data[*(++input)] & 0x3C) >> 2);
            *(output++) = ((toBase64Data[*input] & 0x03) << 6);
        }
    }
    // init string
    NSData *result = [[NSData alloc] initWithBytesNoCopy:bytes length:resultLength freeWhenDone:YES];
    return result;
}

@end

@implementation NSData (Base64)

- (NSString *)base64String
{
    // filter empty
    NSUInteger length = self.length;
    if (!length) {
        return [NSString string];
    }
    // set up string
    NSUInteger resultLength = (4 * length + 2) / 3;
    char *chars = calloc(resultLength, sizeof(char));
    // set up loop
    const unsigned char *input = self.bytes;
    char *output = chars;
    // convert body
    for (const unsigned char *end = input + length; input + 2 < end; input++) {
        *(output++) = toBase64String[                          *   input  >> 2 ];
        *(output++) = toBase64String[((*input & 0x03) << 4) | (*(++input) >> 4)];
        *(output++) = toBase64String[((*input & 0x0F) << 2) | (*(++input) >> 6)];
        *(output++) = toBase64String[  *input & 0x3F                           ];
    }
    // convert tail
    NSUInteger remain = length % 3;
    if (remain) {
        *(output++) = toBase64String[*input >> 2];
        if (remain == 1) {
            *(output++) = toBase64String[((*input & 0x03) << 4)];
        } else {
            *(output++) = toBase64String[((*input & 0x03) << 4) | (*(++input) >> 4)];
            *(output++) = toBase64String[((*input & 0x0F) << 2)];
        }
    }
    // init string
    NSString *result = [[NSString alloc] initWithBytesNoCopy:chars length:resultLength encoding:NSASCIIStringEncoding freeWhenDone:YES];
    return result;
}

@end