本文主要是介绍JS LZW算法压缩与解压，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
JS LZW算法压缩与解压，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。
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<head>
<meta http-equiv="content-type" content="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();
}function lzw_decompress(s){var b = new function(){var d=[],p=0,l=0,L=13,k=m(L),_m=0xFFFFFFFF;this.r=function(){var r;if(32-(p%32)<L)r=(((d[p>>5]&m(32-(p%32)))<<((p+L)%32))|(d[(p>>5)+1]>>>(32-((p+L)%32))))&k;else r=(d[p>>5]>>>(32-(p+L)%32))&k;p+=L;return r;};this.w=function(i){i&=k;if(32-(l%32)<L){d[l>>5]|=i>>>(L-(32-(l%32)));d[(l>>5)+1]|=(i<<(32-((l+L)%32)))&_m;}else d[l>>5]|=(i<<(32-((l+L)%32)))&_m;l+=L;};this.e=function(){return p>=l;};this.l=function(len){L=Math.max(len|0, 1);k=m(L);};function m(len){return (1<<len)-1;}function pad(s,l){return (new Array(l+1)).join("0").substring(s.length)+s;}for(var i=2;i<s.length;i++)this.w(s.charCodeAt(i)-0x4e00);l=((s.charCodeAt(0)-0x4e00)<<13)|((s.charCodeAt(1)-0x4e00)&m(13));p=0;};var R=[],C=-1,D={},P=[],L=8;for(i=0; i<(1<<L)+2; i++)D[i]=String.fromCharCode(++C);b.l(L);P[0]=b.r();while(!b.e()){P[1]=b.r();if(P[1]==0x80){ b.l(++L); P[1]=b.r();}if(D[P[1]]==undefined)D[++C]=D[P[0]]+D[P[0]].charAt(0);else D[++C]=D[P[0]]+D[P[1]].charAt(0);R.push(D[P[0]]);P[0]=P[1];}R.push(D[P[0]]);return R.join("").replace(/\&\#u[0-9a-fA-F]{4};/g,function(w){return String.fromCharCode(parseInt(w.substring(3, 7),16));});}
function lzw_decompress_origin(str){var b = new Binary();b.fromCString(str);b.reset();var result = [], dic_code = -1;var dic={},cp=[], bl = 8;for(i=0; i<(1<<bl)+2; i++)dic[i] = String.fromCharCode(++dic_code); //init the dicb.setBitLength(bl);cp[0]=b.read();while(!b.eof()){cp[1]=b.read();if(cp[1] == 0x80){ b.setBitLength(++bl); cp[1]=b.read(); }if(dic[cp[1]]==undefined)dic[++dic_code]=dic[cp[0]]+dic[cp[0]].charAt(0);else dic[++dic_code]=dic[cp[0]]+dic[cp[1]].charAt(0);result.push(dic[cp[0]]);cp[0]=cp[1];}result.push(dic[cp[0]]);return result.join("").replace(/\&\#u[0-9a-fA-F]{4};/g,function(w){return String.fromCharCode(parseInt(w.substring(3, 7),16));});
}
</SCRIPT>
</head>
<body >
<textarea id="source"></textarea>
<textarea id="result"></textarea>
<br/>
<br/>
<input type="button" value="Compress" οnclick="doit();" />
<input type="button" value="DeCompress" οnclick="doit2();" />
<input type="checkbox" id="chkSE" /><label for="chkSE">压缩为自解压格式</label>
<span id="info"></span>
</body>
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