改进Javascript Base64编码传送
(2011-11-09 09:14)
今天更新博客时，顺便翻看了一下以前写的的东西，发现08年写的一篇用Javascript进行Base64编码传送数据的文章。说实在的，当初写这篇东西的时候，自己几乎是不懂Javascript的，只是看到公司的产品在应对各种Location, Language以及各种页面编码设置，存在大量的bug时，有心尝试一下用Base64解决的可能性，而最终并没有在产品中采用。
而如今（我指的是三年后的今天），我们的确在最新的产品中，成功使用了这一方案，并彻底摆脱了各种编码传送的问题。算法方面还是和以前一模一样，只不过，性能上做了局部优化，并在封装形式上有些变化，一如我提倡的Javascript用Java like的风格来写出Java程序员可以维护的代码一样，封装出一个js.util.Base64类：
- $package("js.util");
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js.util.Base64 = new function (){
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var base64chars = "ABCDEFGHIJKLMNOP" +
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"QRSTUVWXYZabcdef"+
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"ghijklmnopqrstuv"+
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"wxyz0123456789@*"+
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"-";
-
-
/**
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* Encode a string to a Base64 string follow Bse64 regular.
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* @param s, a normal string
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* @return a Base64 string
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*/
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this.encode = function(s){
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if(!s || s.length == 0) return s;
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var d = [], b = ucs2_utf8(s), len = b.length,
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b0, b1, b2, b3, i = 0, tmp;
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while(i < len){
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tmp = b[i++];
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b0 = (tmp & 0xfc) >> 2;
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b1 = (tmp & 0x03) << 4;
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if(i < len){
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tmp = b[i++];
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b1 |= (tmp & 0xf0) >> 4;
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b2 = (tmp & 0x0f) << 2;
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if(i< len){
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tmp = b[i++];
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b2 |= (tmp & 0xc0) >> 6;
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b3 = tmp & 0x3f;
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}else{
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b3 = 64; // 1 byte "-" is supplement
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}
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}else{
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b2 = b3 = 64; // 2 bytes "-" are supplement
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}
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d.push(base64chars.charAt(b0));
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d.push(base64chars.charAt(b1));
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d.push(base64chars.charAt(b2));
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d.push(base64chars.charAt(b3));
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}
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return d.join("");
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};
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/**
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* Decode a Base64 string to a string follow Base64 regular.
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* @param s, a Base64 string
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* @return a normal string
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*/
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this.decode = function(s){
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if(!s) return null;
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var len = s.length;
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if(len%4 != 0)
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throw new Error(s+" is not a valid Base64 string.");
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var b = [], i=0, j=0, e=0, c, tmp;
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while(i < len){
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c = base64chars.indexOf(s.charAt(i++));
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tmp = c << 18;
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c = base64chars.indexOf(s.charAt(i++));
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tmp |= c << 12;
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c = base64chars.indexOf(s.charAt(i++));
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if(c < 64){
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tmp |= c << 6;
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c = base64chars.indexOf(s.charAt(i++));
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if(c < 64){
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tmp |= c;
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}else{
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e = 1;
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}
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}else{
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e = 2;
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i++;
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}
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b[j+2] = tmp & 0xff;
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tmp >>= 8;
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b[j+1] = tmp & 0xff;
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tmp >>= 8;
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b[j+0] = tmp & 0xff;
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j += 3;
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}
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b.splice(b.length-e, e);
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return utf8_ucs2(b);
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};
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/**
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* Encodes a utf8 integer array to a ucs2 string.
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* @param s, an integer array
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* @return a string
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*/
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var utf8_ucs2 = function(s){
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if(!s) return null;
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var len = s.length;
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if(len == 0) return "";
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var d = [], c = 0, i = 0, tmp = 0;
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while(i < len){
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c = s[i++];
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if((c & 0xe0) == 0xe0){
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// 3 bytes
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tmp = (c & 0x0f) << 12;
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c = s[i++];
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tmp |= ((c & 0x3f) << 6);
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c = s[i++];
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tmp |= (c & 0x3f);
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}else
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if((c & 0xc0) == 0xc0){
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// 2 bytes
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tmp = (c & 0x1f) << 6;
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c = s[i++];
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tmp |= (c & 0x3f);
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}else{
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// 1 byte
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tmp = c;
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}
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d.push(String.fromCharCode(tmp));
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}
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return d.join("");
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};
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/**
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* Encodes a ucs2 string to a utf8 integer array.
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* @param s, a string
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* @return an integer array
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*/
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var ucs2_utf8 = function(s){
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if (!s) return null;
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var d = [];
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if (s == "") return d;
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var c = 0, i = 0, j = 0, len = s.length;
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while(i < len){
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c = s.charCodeAt(i++);
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if(c <= 0x7f){
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// 1 byte
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d[j++] = c;
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}else
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if((c >= 0x80) && (c <= 0x7ff)){
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// 2 bytes
-
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d[j++] = ((c >> 6) & 0x1f) | 0xc0;
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d[j++] = (c & 0x3f) | 0x80;
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}else{
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// 3 bytes
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d[j++] = (c >> 12) | 0xe0;
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d[j++] = ((c >> 6) & 0x3f) | 0x80;
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d[j++] = (c & 0x3f) | 0x80;
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}
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}
-
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return d;
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};
-
- }();
