root / trunk / web / dojo / dojox / encoding / compression / lzw.js @ 12
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/*
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Copyright (c) 2004-2010, The Dojo Foundation All Rights Reserved.
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Available via Academic Free License >= 2.1 OR the modified BSD license.
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see: http://dojotoolkit.org/license for details
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*/
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if(!dojo._hasResource["dojox.encoding.compression.lzw"]){ |
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dojo._hasResource["dojox.encoding.compression.lzw"]=true; |
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dojo.provide("dojox.encoding.compression.lzw");
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dojo.require("dojox.encoding.bits");
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(function(){
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var _1=function(x){ |
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var w=1; |
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for(var v=2;x>=v;v<<=1,++w){ |
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} |
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return w;
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}; |
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dojox.encoding.compression.lzw.Encoder=function(n){ |
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this.size=n;
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this.init();
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}; |
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dojo.extend(dojox.encoding.compression.lzw.Encoder,{init:function(){ |
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this.dict={};
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for(var i=0;i<this.size;++i){ |
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this.dict[String.fromCharCode(i)]=i;
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} |
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this.width=_1(this.code=this.size); |
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this.p=""; |
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},encode:function(_2,_3){ |
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var c=String.fromCharCode(_2),p=this.p+c,r=0; |
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if(p in this.dict){ |
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this.p=p;
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return r;
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} |
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_3.putBits(this.dict[this.p],this.width); |
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if((this.code&(this.code+1))==0){ |
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_3.putBits(this.code++,r=this.width++); |
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} |
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this.dict[p]=this.code++; |
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this.p=c;
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return r+this.width; |
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},flush:function(_4){ |
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if(this.p.length==0){ |
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return 0; |
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} |
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_4.putBits(this.dict[this.p],this.width); |
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this.p=""; |
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return this.width; |
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}}); |
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dojox.encoding.compression.lzw.Decoder=function(n){ |
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this.size=n;
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this.init();
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}; |
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dojo.extend(dojox.encoding.compression.lzw.Decoder,{init:function(){ |
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this.codes=new Array(this.size); |
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for(var i=0;i<this.size;++i){ |
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this.codes[i]=String.fromCharCode(i);
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} |
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this.width=_1(this.size); |
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this.p=-1; |
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},decode:function(_5){ |
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var c=_5.getBits(this.width),v; |
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if(c<this.codes.length){ |
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v=this.codes[c];
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if(this.p>=0){ |
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this.codes.push(this.codes[this.p]+v.substr(0,1)); |
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} |
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}else{
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if((c&(c+1))==0){ |
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this.codes.push(""); |
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++this.width;
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return ""; |
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} |
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var x=this.codes[this.p]; |
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v=x+x.substr(0,1); |
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this.codes.push(v);
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} |
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this.p=c;
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return v;
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}}); |
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})(); |
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} |