JS BASE64_ENCODE与BASE64_DECODE的实例代码

<script language='javascript'>
/* utf.js - UTF-8 <=> UTF-16 convertion
*
* Copyright (C) 1999 Masanao Izumo <iz@onicos.co.jp>
* Version: 1.0
* LastModified: Dec 25 1999
* This library is free.   You can redistribute it and/or modify it.
*/
/*
* Interfaces:
* utf8 = utf16to8(utf16);
* utf16 = utf16to8(utf8);
*/
function utf16to8(str) {
     var out, i, len, c;
     out = "";
     len = str.length;
     for(i = 0; i < len; i++) {
         c = str.charCodeAt(i);
         if ((c >= 0x0001) && (c <= 0x007F)) {
             out += str.charAt(i);
         } 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, i, len, c;
     var char2, char3;
     out = "";
     len = str.length;
     i = 0;
     while(i < len) {
         c = str.charCodeAt(i++);
         switch(c >> 4)
         {
           case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
             // 0xxxxxxx
             out += str.charAt(i-1);
             break;
           case 12: case 13:
             // 110x xxxx    10xx xxxx
             char2 = str.charCodeAt(i++);
             out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
             break;
           case 14:
             // 1110 xxxx   10xx xxxx   10xx xxxx
             char2 = str.charCodeAt(i++);
             char3 = str.charCodeAt(i++);
             out += String.fromCharCode(((c & 0x0F) << 12) |
                                            ((char2 & 0x3F) << 6) |
                                            ((char3 & 0x3F) << 0));
             break;
         }
     }
     return out;
}
/* Copyright (C) 1999 Masanao Izumo <iz@onicos.co.jp>
* Version: 1.0
* LastModified: Dec 25 1999
* This library is free.   You can redistribute it and/or modify it.
*/
/*
* Interfaces:
* b64 = base64encode(data);
* data = base64decode(b64);
*/

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);
function base64encode(str) {
     var out, i, len;
     var c1, c2, c3;
     len = str.length;
     i = 0;
     out = "";
     while(i < len) {
         c1 = str.charCodeAt(i++) & 0xff;
         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;
}
function base64decode(str) {
     var c1, c2, c3, c4;
     var i, len, 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)
                 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)
                 return out;
             c4 = base64DecodeChars[c4];
         } while(i < len && c4 == -1);
         if(c4 == -1)
             break;
         out += String.fromCharCode(((c3 & 0x03) << 6) | c4);
     }
     return out;
}
//input base64 encode
function strdecode(str){
         return utf8to16(base64decode(str));
}