javascript 使用数据加密跟base64 编码

   下面的js代码首先将给定的数据字符串,跟指定的密匙字符串做异或运算,接着将结果序列进行base64编码,
 下面同时给出了解密算法跟,base64还原函数

代码如下:

  function secode(opArray) {
        var _local2 = opArray;
        var strEnd="=";
        var _local3 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
        var bits;
        var decOut = new Array ();
        var _local1 = 0;
        var j = 0;
        _local1 = 0;
        while (_local1 < _local2.length) {

           //第一个元素(这里前提是单字节)向前移动2个字节,
           //第二个移动1字节,第三个不移动
          //那么 | 后的结果是,形成一个 3字节的数据如下
          //xxxxxxxx0000000000000000
          //00000000xxxxxxxx00000000
          //0000000000000000xxxxxxxx
          //注意bits是一个正整数,其值等与上面3组数 |(异)  后的数值
          //16515072的二进制表示为:1111 1100, 0000 0000 ,0000 0000
          //那么 bits & 16515072 后,就是取bits的前6位
          //>>18 表示右移动 18为注意 bits & 16515072 后是正数,那么>>18时高位补的是00,
          // 正数高位第一位为0,负数为1
         //这样((bits & 16515072)>>18)的值就是其在_local3中对应字的符位置.
            bits = ((_local2[_local1]<<16) | (_local2[_local1+1]<<8) | (_local2[_local1+2]));
            decOut[j++] = _local3.charAt((bits & 16515072) >> 18);
            decOut[j++] = _local3.charAt((bits & 258048) >> 12);
            decOut[j++] = _local3.charAt((bits & 4032) >> 6);
            decOut[j++] = _local3.charAt(bits & 63);
            _local1 = _local1 + 3;
        }

        //另外258048其二进制表示为 11 ,1111 0000 ,0000 0000
       // 等价于0000 0011 ,1111 0000 ,0000 0000 (正数高位为0)
       //当字节数不是3的整数倍时,_local2[_local1+1],或_local2[_local1+2] 其值(下标已经超标)是0,
      //也正好符合base64不足补零的定义
        switch(_local2.length%3){
                 //多一个字节时映射成的4字接有2个字节里无数据(纯零)应此丢弃
                 //多2个字节时,丢弃一个,而正好是,末尾不加"=",故将strEnd="" 设置为空.
                case 1:decOut.pop();decOut.pop();break;
                case 2:decOut.pop();break;
                case 0:strEnd="";break;
        }
        decOut.push(strEnd);
        return (decOut.join(""));
    }
    function encode(var1, key) {
        var _local3 = var1;
        var2 = new Array();
        var _local2 = 0;
        var _local1 = 0;
        while (_local1 < _local3.length) {
            var2.push(_local3.charCodeAt(_local1) ^ key.charCodeAt(_local2++));

           //当key序列不够长时循环使用
            if (_local2 >= key.length) {
                _local2 = 0;
            }
            _local1++;
        }
        var2=secode(var2);
        return (var2);
    }
   function decode(var1, key) {
        var _local3 = var1;
        _local3 = becode(_local3);
        var2 = "";
        var _local2 = 0;
        var _local1 = 0;
        while (_local1 < _local3.length) {
            var2 = var2.concat(String.fromCharCode(_local3[_local1] ^ key.charCodeAt(_local2++)));
            if (_local2 >= key.length) {
                _local2 = 0;
            }
            _local1++;
        }
        return (var2);
    }
    function becode(opString) {
        var _local2 = opString;
        var _local3 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
        var bits;
        var decOut = new Array ();
        var _local1 = 0;
        var j = 0;
        _local1 = 0;
        while (_local1 < _local2.length) {
            bits = ((((_local3.indexOf(_local2.charAt(_local1)) & 255) << 18) | ((_local3.indexOf(_local2.charAt(_local1 + 1)) & 255) << 12)) | ((_local3.indexOf(_local2.charAt(_local1 + 2)) & 255) << 6)) | (_local3.indexOf(_local2.charAt(_local1 + 3)) & 255);
            decOut[j++] = (bits & 16711680) >> 16;
            decOut[j++] = (bits & 65280) >> 8;
            decOut[j++] = bits & 255;
            _local1 = _local1 + 4;
        }
        if (_local2.charCodeAt(_local1 - 2) == 61) {
            decOut.pop();
            decOut.pop();
        } else if (_local2.charCodeAt(_local1 - 1) == 61) {
            decOut.pop();
            //
        }
        return (decOut);
    }
 function base64(str){
  var d=new Array();
  for(var i=0;i<str.length;i++){
    d.push(str.charCodeAt(i));
  }alert(d);
   return secode(d);
 }

//说明,首先获取字符串的字节序列(Array) 使用 str.charCodeAt(i), 这里需要注意的是, charCodeAt(i)获取的值应该<=255 (单字节) 如果str中含有中文等双字节码,那么请先使用str=escape(str)对其进行编码(还原时使用unescape).

encode函数, encode里将待处理字符序列(假设已经为单字节序列),与给顶的key序列,将每个字符的Unicode值做^操作,获得一个待base64编码数组.

secode函数, 根据base64编码,将每3个字节映射成4个字节,当字节数不是3的倍数时尾部补0(bit),形成的base64字符串最后加"="

后面的两个是相应的还原函数