MD5 encode NSString

// MD5
#import <CommonCrypto/CommonDigest.h>
- (NSString*)getMD5WithString: (NSString*)str{
    // Create pointer to the string as UTF8
    const char *ptr = [str UTF8String];

    // Create byte array of unsigned chars
    unsigned char md5Buffer[CC_MD5_DIGEST_LENGTH];

    // Create 16 byte MD5 hash value, store in buffer
    CC_MD5(ptr, strlen(ptr), md5Buffer);

    // Convert MD5 value in the buffer to NSString of hex values
    NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
        [output appendFormat:@"%02x",md5Buffer[i]];

    return output;
}