swift：将字符串进行MD5加密，解决MD5加密造成的内存泄漏

extension String {
    //MARK: MD5加密
    public func addMD5() -> String {
        let str = self.cString(using: .utf8)
        let strLen = CUnsignedInt(self.lengthOfBytes(using: .utf8))
        let digestLen = Int(CC_MD5_DIGEST_LENGTH)
        let result = UnsafeMutablePointer<CUnsignedChar>.allocate(capacity:digestLen)
        CC_MD5(str!, strLen, result)
            
        let hash = NSMutableString()
        for i in 0 ..< digestLen {
            hash.appendFormat("%02X", result[i])
        }
        free(result)//解决MD5加密造成的内存泄漏问题
        return String(format: hash as String)
    }
}

使用：let res = resStr.addMD5()