写的一些常用加解密函数，比如Base64加密与解密，网址转码与解码，MD5加密，HMAC－MD5加密，UTF－8编码与解码等，代码极度优化。-Write some commonly used encryption and decryption functions, such as Base64 encryption and decryption at transcoding and decoding, MD5 encryption, HMAC-MD5 encryption, UTF-8 encoding and decoding, the code is extremely optimized.