function utf16to8(str) 
{
    var out;
    var len;
    var c;
    var idx=0;
    out = "";
    len = str.length;
    for(idx = 0; idx < len; idx++) 
    {
        c = str.charCodeAt(idx);
        if ((c >= 0x0001) && (c <= 0x007F)) 
        {
            out += str.charAt(idx);
        } else if (c > 0x07FF)
        {
            out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
            out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));
            out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
        }else
        {
            out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));
            out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
        }
    }
    return out;
}



function utf8to16(str) 
{
    var out;
    var idx2=0;
    var  len;
    var c;
    var char2, char3;
    out = "";
    len = str.length;
    idx2 = 0;
    while(idx2 < len)
    {
        c = str.charCodeAt(idx2++);
        switch(c >> 4)
        {
            case 0: 
            case 1: 
            case 2: 
            case 3: 
            case 4: 
            case 5: 
            case 6: 
            case 7:
            {// 0xxxxxxx
                out += str.charAt(idx2-1);
            }
            break;
            case 12: 
            case 13:
            {// 110x xxxx 10xx xxxx
                char2 = str.charCodeAt(idx2++);
                out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
            }
            break;
            case 14:
            {// 1110 xxxx 10xx xxxx 10xx xxxx
                char2 = str.charCodeAt(idx2++);
                char3 = str.charCodeAt(idx2++);
                out += String.fromCharCode(((c & 0x0F) << 12) |
                ((char2 & 0x3F) << 6) |
                ((char3 & 0x3F) << 0));
            }
            break;
        }
    }
    return out;
}


var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
var base64DecodeChars = new Array(
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1);


//客户端Base64编码
function base64encode(str)
{
    var out;
    var i;
    var len;
    var c1;
    var c2;
    var  c3;
    str=utf16to8(str);
    len = str.length;
    i = 0;
    out = "";
    while(i < len)
    {
        c1 = str.charCodeAt(i++);
        if(i == len)
        {
            out += base64EncodeChars.charAt(c1 >> 2);
            out += base64EncodeChars.charAt((c1 & 0x3) << 4);
            out += "==";
            break;
        }
        c2 = str.charCodeAt(i++);
        if(i == len)
        {
            out += base64EncodeChars.charAt(c1 >> 2);
            out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));
            out += base64EncodeChars.charAt((c2 & 0xF) << 2);
            out += "=";
            break;
        }
        c3 = str.charCodeAt(i++);
        out += base64EncodeChars.charAt(c1 >> 2);
        out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));
        out += base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >>6));
        out += base64EncodeChars.charAt(c3 & 0x3F);
    }
    return out;
}



//客户端Base64解码
function base64decode(str) 
{
    var c1;
    var c2;
    var c3;
    var c4;
    var i;
    var len;
    var out;
    len = str.length;
    i = 0;
    out = "";
    while(i < len)
    {
        /* c1 */
        do
        {
            c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
        } while(i < len && c1 == -1);
        if(c1 == -1)
        {
            break;
        }

        /* c2 */
        do
        {
            c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
        } while(i < len && c2 == -1);
        if(c2 == -1)
        {
            break;
        }

        out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));

        /* c3 */
        do 
        {
            c3 = str.charCodeAt(i++) & 0xff;
            if(c3 == 61)
            {
                out=utf8to16(out);
                return out;
            }
            c3 = base64DecodeChars[c3];
        } while(i < len && c3 == -1);
        if(c3 == -1)
        {
            break;
        }
        
        out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));

        /* c4 */
        do
        {
            c4 = str.charCodeAt(i++) & 0xff;
            if(c4 == 61)
            {  
                out=utf8to16(out);
                return out;
            }
            c4 = base64DecodeChars[c4];
        }while(i < len && c4 == -1);
        
        if(c4 == -1)
        {
            break;
        }
        out += String.fromCharCode(((c3 & 0x03) << 6) | c4);
    }
    out=utf8to16(out);
    return out;
}


