ついカッとなって勢いで書いた奴

gistfile1.m

- (NSString*)base64:(NSData*)fromData {
	static unsigned char base64Table[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	const unsigned char *data = fromData.bytes;
	char *buff = NSZoneMalloc(self.zone, fromData.length * 4 / 3 + 4);
	int o = 0, i;
	for (i = 0; i <= fromData.length; i++, o++) {
		switch (i % 3) {
			case 0:
				if (i < fromData.length) {
					buff[o] = base64Table[(data[i] >> 2) & 0x3f];
				}
				break;
			case 1:
				buff[o] = base64Table[((data[i - 1] << 4) | ((i < fromData.length ? data[i] : 0) >> 4)) & 0x3f];
				break;
			case 2:
				buff[o] = base64Table[((data[i - 1] << 2) | ((i < fromData.length ? data[i] : 0) >> 6)) & 0x3f];
				if (i < fromData.length) {
					o++;
					buff[o] = base64Table[data[i] & 0x3f];
				}
				break;
			default:
				break;
		}
	}
	buff[o] = '\0';
	NSString *ret = [NSString stringWithCString:buff encoding:NSASCIIStringEncoding];
	NSZoneFree(self.zone, buff);
	return ret;
}