/****  Base64 encode / decode*  文字采用utf-8方式进行Base64编码
**/function Base64() {    // private property    _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";    // public method for encoding    this.encode = function (input) {        var output=new Array();
        var chr1, chr2, chr3;
        var enc1, enc2, enc3, enc4;        var i = 0;        input = _utf8_encode(input);        while (i < input.length)        {            chr1 = input[i++];
            chr2 = input[i++];
            chr3 = input[i++];
            enc1 = chr1 >> 2;            enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);            enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);            enc4 = chr3 & 63;            if (isNaN(chr2)) {                enc3 = enc4 = 64;            } else if (isNaN(chr3)) {                enc4 = 64;            }            output.push(_keyStr.charAt(enc1) + _keyStr.charAt(enc2) + _keyStr.charAt(enc3) + _keyStr.charAt(enc4));        }        return output.join('');
    }    // public method for decoding    this.decode = function (input) {        var output = "";        var chr1, chr2, chr3;        var enc1, enc2, enc3, enc4;        var i = 0;        input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");        while (i < input.length) {            enc1 = _keyStr.indexOf(input.charAt(i++));            enc2 = _keyStr.indexOf(input.charAt(i++));            enc3 = _keyStr.indexOf(input.charAt(i++));            enc4 = _keyStr.indexOf(input.charAt(i++));            chr1 = (enc1 << 2) | (enc2 >> 4);            chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);            chr3 = ((enc3 & 3) << 6) | enc4;            output = output + String.fromCharCode(chr1);            if (enc3 != 64) {                output = output + String.fromCharCode(chr2);            }            if (enc4 != 64) {                output = output + String.fromCharCode(chr3);            }        }        output = _utf8_decode(output);        return output;    }    // private method for utf-8 encoding    _utf8_encode = function (string) {        string = string.replace(/\r\n/g,"\n");        var utftext = new Array();
        var utftextlen=0;
        for (var n = 0; n < string.length; n++) {            var c = string.charCodeAt(n);            if (c < 128) {                utftext[utftextlen++] = c;
            } else if((c > 127) && (c < 2048)) {                utftext[utftextlen++] = (c >> 6) | 192;
                utftext[utftextlen++] = (c & 63) | 128;
            } else {                utftext[utftextlen++] = (c >> 12) | 224;
                utftext[utftextlen++] = ((c >> 6) & 63) | 128;
                utftext[utftextlen++] = (c & 63) | 128;            }        }        return utftext;    }    // private method for utf-8 decoding    _utf8_decode = function (utftext) {        var string = "";        var i = 0;        var c = c1 = c2 = 0;        while ( i < utftext.length ) {            c = utftext.charCodeAt(i);            if (c < 128) {                string += String.fromCharCode(c);                i++;            } else if((c > 191) && (c < 224)) {                c2 = utftext.charCodeAt(i+1);                string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));                i += 2;            } else {                c2 = utftext.charCodeAt(i+1);                c3 = utftext.charCodeAt(i+2);                string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));                i += 3;            }        }        return string;    }    _exchange_character = function(charArray){
    	charArray=charArray.split("");
		for (var i = 0; i < charArray.length; i++)
		{
			// 互换相邻的字符
			if (i > 0 && i % 2 == 0)
			{
				var c = charArray[i];
				charArray[i] = charArray[i - 1];
				charArray[i - 1] = c;
			}
		}
		return charArray.join("");
    }
    //参数需要绕过防火墙可使用此方法加密
    this.encodePostParam = function(input) {
    	input=this.encode(input).split("").reverse().join("");
    	return _exchange_character(input);
    }
    this.decodePostParam = function(input) {
    	input=_exchange_character(input).split("").reverse().join("");
    	return this.decode(input);
    }
}