iOS:MD5加密

使用Swift的方法来加密的时候存在内存泄露的问题，但是在OC上使用就不会出现内存泄露；Swift为何会泄露这个还未知、尽请告知。
(直接正文)
先添加头文件：<CommonCrypto/CommonDigest.h>
OC方式

- (NSString *)md5OC:(NSString *)string {
    const char *cStr = [string UTF8String];
    unsigned char digest[CC_MD5_DIGEST_LENGTH];
    CC_MD5(cStr, (int)strlen(cStr), digest);

    NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i++) {
        [output appendFormat:@"%02x", digest[i]];
    }
    return output;
}

Swift方式

func md5() -> String {
    let str = self.cStringUsingEncoding(NSUTF8StringEncoding)
    let strLen = CUnsignedInt(self.lengthOfBytesUsingEncoding(NSUTF8StringEncoding))
    let digestLen = Int(CC_MD5_DIGEST_LENGTH)
    let result = UnsafeMutablePointer<CUnsignedChar>.alloc(digestLen)
    CC_MD5(str!, UInt32(strLen), result)
    let hash = NSMutableString.init(capacity: Int(CC_MD5_DIGEST_LENGTH) * 2)
    for i in 0 ..< digestLen {
        hash.appendFormat("%02x", result[i])
    }
    result.destroy()
    return hash as String
  }

第三方MD5加密库：CryptoSwift