JavaScript二进制接口，LZW 压缩解压算法_计算转换特效

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一个JavaScript二进制接口源码，LZW 压缩解压算法，压缩比确实不错，代码不超过200行，使用理解修改，运行代码可看效果。

<html>
<head>
<meta http-equiv="mrc-type" mrc="text/html; charset=utf-8">
<title>LZW 压缩解压</title>
<style>
* { font-size:12px}
body { overflow:auto; border-style:none; background-color:buttonface; }
#source, #result { overflow:auto; width:100%; height:300px; }
</style>
<script>
function $(s){ return document.getElementById(s); }
window.onload = function(){
	$("source").focus();
	$("source").onkeydown = function(e){
		e = window.event || e;
		if(e.keyCode == 13 && e.ctrlKey)doit();
	}
	
	$("result").onkeydown = function(e){
		e = window.event || e;
		if(e.keyCode == 13 && e.ctrlKey)doit2();
	}
	
	$("source").value = document.getElementsByTagName("script")[0].innerHTML;
	
}
function doit(){
	$("result").value = $("chkSE").checked?("eval(("+String(lzw_decompress)+")(\""+lzw_compress($("source").value)+"\"))"):(lzw_compress($("source").value));
	$("info").innerHTML = "源："+$("source").value.length + "，值：" + $("result").value.length + "，压缩比" + ($("result").value.length / $("source").value.length).toFixed(3);
}
function doit2(){
	$("source").value = $("chkSE").checked?(eval($("result").value.substring(4))):(lzw_decompress($("result").value));
}
function Binary(initData, p, l, bl){
	var data=initData&&initData.constructor==Array?initData.slice():[], p=p|0, l=l|0, bl=Math.max((bl||8)|0,1), mask=m(bl), _m = 0xFFFFFFFF; //数据，指针，长度，位长度，遮罩
	this.data = function(index, value){ if(!isNaN(value))data[index]=(value|0)||0; if(!isNaN(index))return data[index];else return data.slice(); }
	
	this.read = function(){
		var re;
		if(p >= l)return 0;
		if(32 - (p % 32) < bl){
			re = (((data[p>>5] & m(32 - (p%32))) << ((p+bl)%32)) | (data[(p>>5)+1]>>>(32 - ((p+bl)%32)))) & mask;
		}else{
			re = (data[p>>5] >>> (32 - (p+bl)%32)) & mask;
		}
		p+=bl;
		return re;
	}
	
	this.write = function(i){
		var i, hi, li;
		i &= mask;
		if(32 - (l % 32) < bl){
			data[l>>5] |= i >>> (bl - (32 - (l % 32)));
			data[(l>>5)+1] |= (i << (32 - ((l+bl)%32))) & _m;
		}else{
			data[l>>5] |= (i << (32 - ((l+bl)%32))) & _m;
		}
		l += bl;
	}
	
	this.eof = function(){ return p >= l; }
	
	this.reset = function(){ p=0; mask=m(bl); }
	this.resetAll = function(){ data=[]; p=0; l=0; bl=8; mask=m(bl); _m = 0xFFFFFFFF; }
	
	this.setBitLength = function(len){
		bl = Math.max(len|0, 1);
		mask=m(bl);
	}
	
	this.toHexString = function(){
		var re = [];
		for(var i=0; i<data.length; i++){
			if(data[i] < 0){
				re.push(pad((data[i]>>>16).toString(16), 4) + pad((data[i] & 0xFFFF).toString(16), 4));
			}else{
				re.push(pad(data[i].toString(16), 8));
			}
		}
		return re.join("");
	}
	
	this.toBinaryString = function(){
		var re = [];
		for(var i=0; i<data.length; i++){
			if(data[i] < 0){
				re.push(pad((data[i]>>>1).toString(2), 31) + (data[i] & 1));
			}else{
				re.push(pad(data[i].toString(2), 32));
			}
		}
		return re.join("").substring(0, l);
	}
	
	this.toCString = function(){
		var _p = p, _bl = bl, re = [];
		this.setBitLength(13);
		this.reset();
		while(p < l)re.push(C(this.read()));
		this.setBitLength(_bl);
		p = _p;
		return C(l>>>13) + C(l & m(13)) + re.join("");
	}
	
	this.fromCString = function(str){
		this.resetAll();
		this.setBitLength(13);
		for(var i=2; i<str.length; i++)this.write(D(str, i));
		l = (D(str, 0) << 13) | (D(str, 1) & m(13));
		return this;
	}
	
	this.clone = function(){ return new Binary(data, p, l, bl); }
	function m(len){ return (1<<len)-1; }
	function pad(s, len){ return (new Array(len+1)).join("0").substring(s.length) + s; }
	function C(i){ return String.fromCharCode(i + 0x4e00); }
	function D(s, i){ return s.charCodeAt(i) - 0x4e00; }
}
function lzw_compress(str){
	var b = new Binary(), code_index = -1, char_len = 8;
	var str = str.replace(/[\u0100-\uFFFF]/g, function(s){
		return "\&\#u"+pad(s.charCodeAt(0).toString(16), 4)+";";
	});
	var dic = {}, cp = [], cpi, bl = 8;
	b.setBitLength(bl);
	for(var i=0; i<(1<<char_len)+2; i++)dic[i] = ++code_index;
	cp[0] = str.charCodeAt(0);
	for(var i=1; i<str.length; i++){
		cp[1] = str.charCodeAt(i);
		cpi = (cp[0]<<16) | cp[1];
		if(dic[cpi]==undefined){
			dic[cpi] = (++code_index);
			if(cp[0] > m(bl)){ b.write(0x80); b.setBitLength(++bl); }
			b.write(cp[0]);
			cp[0] = cp[1];
		}else{
			cp[0] = dic[cpi];
		}
	}
	b.write(cp[0]);
	function pad(s, len){ return (new Array(len+1)).join("0").substring(s.length) + s; }
	function m(len){ return (1<<len)-1; }
	return b.toCString();
}

所属频道：计算转换特效/更新时间：2012-09-16

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