Ext base64函数

同样是在Extjs 论坛弄来的
原帖
http://extjs.com/forum/showthread.php?p=167166#post167166

Ext.util.base64 = {

    base64s : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
    
    encode: function(decStr){
        if (typeof btoa === 'function') {
             return btoa(decStr);            
        }
        var base64s = this.base64s;
        var bits;
        var dual;
        var i = 0;
        var encOut = "";
        while(decStr.length >= i + 3){
            bits = (decStr.charCodeAt(i++) & 0xff) <<16 | (decStr.charCodeAt(i++) & 0xff) <<8 | decStr.charCodeAt(i++) & 0xff;
            encOut += base64s.charAt((bits & 0x00fc0000) >>18) + base64s.charAt((bits & 0x0003f000) >>12) + base64s.charAt((bits & 0x00000fc0) >> 6) + base64s.charAt((bits & 0x0000003f));
        }
        if(decStr.length -i > 0 && decStr.length -i < 3){
            dual = Boolean(decStr.length -i -1);
            bits = ((decStr.charCodeAt(i++) & 0xff) <<16) |    (dual ? (decStr.charCodeAt(i) & 0xff) <<8 : 0);
            encOut += base64s.charAt((bits & 0x00fc0000) >>18) + base64s.charAt((bits & 0x0003f000) >>12) + (dual ? base64s.charAt((bits & 0x00000fc0) >>6) : '=') + '=';
        }
        return(encOut);
    },
    
    decode: function(encStr){
        if (typeof atob === 'function') {
            return atob(encStr); 
        }
        var base64s = this.base64s;        
        var bits;
        var decOut = "";
        var i = 0;
        for(; i<encStr.length; i += 4){
            bits = (base64s.indexOf(encStr.charAt(i)) & 0xff) <<18 | (base64s.indexOf(encStr.charAt(i +1)) & 0xff) <<12 | (base64s.indexOf(encStr.charAt(i +2)) & 0xff) << 6 | base64s.indexOf(encStr.charAt(i +3)) & 0xff;
            decOut += String.fromCharCode((bits & 0xff0000) >>16, (bits & 0xff00) >>8, bits & 0xff);
        }
        if(encStr.charCodeAt(i -2) == 61){
            return(decOut.substring(0, decOut.length -2));
        }
        else if(encStr.charCodeAt(i -1) == 61){
            return(decOut.substring(0, decOut.length -1));
        }
        else {
            return(decOut);
        }
    }

};