root / trunk / web / dojo / dojox / encoding / compression / lzw.js @ 12
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| 1 | 9 | andrej.cim | /*
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| 2 | Copyright (c) 2004-2010, The Dojo Foundation All Rights Reserved.
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| 3 | Available via Academic Free License >= 2.1 OR the modified BSD license.
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| 4 | see: http://dojotoolkit.org/license for details
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| 5 | */
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| 6 | |||
| 7 | |||
| 8 | if(!dojo._hasResource["dojox.encoding.compression.lzw"]){ |
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| 9 | dojo._hasResource["dojox.encoding.compression.lzw"]=true; |
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| 10 | dojo.provide("dojox.encoding.compression.lzw");
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| 11 | dojo.require("dojox.encoding.bits");
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| 12 | (function(){
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| 13 | var _1=function(x){ |
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| 14 | var w=1; |
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| 15 | for(var v=2;x>=v;v<<=1,++w){ |
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| 16 | } |
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| 17 | return w;
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| 18 | }; |
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| 19 | dojox.encoding.compression.lzw.Encoder=function(n){ |
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| 20 | this.size=n;
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| 21 | this.init();
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| 22 | }; |
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| 23 | dojo.extend(dojox.encoding.compression.lzw.Encoder,{init:function(){
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| 24 | this.dict={};
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| 25 | for(var i=0;i<this.size;++i){ |
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| 26 | this.dict[String.fromCharCode(i)]=i;
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| 27 | } |
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| 28 | this.width=_1(this.code=this.size); |
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| 29 | this.p=""; |
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| 30 | },encode:function(_2,_3){ |
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| 31 | var c=String.fromCharCode(_2),p=this.p+c,r=0; |
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| 32 | if(p in this.dict){ |
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| 33 | this.p=p;
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| 34 | return r;
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| 35 | } |
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| 36 | _3.putBits(this.dict[this.p],this.width); |
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| 37 | if((this.code&(this.code+1))==0){ |
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| 38 | _3.putBits(this.code++,r=this.width++); |
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| 39 | } |
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| 40 | this.dict[p]=this.code++; |
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| 41 | this.p=c;
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| 42 | return r+this.width; |
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| 43 | },flush:function(_4){ |
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| 44 | if(this.p.length==0){ |
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| 45 | return 0; |
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| 46 | } |
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| 47 | _4.putBits(this.dict[this.p],this.width); |
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| 48 | this.p=""; |
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| 49 | return this.width; |
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| 50 | }}); |
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| 51 | dojox.encoding.compression.lzw.Decoder=function(n){ |
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| 52 | this.size=n;
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| 53 | this.init();
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| 54 | }; |
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| 55 | dojo.extend(dojox.encoding.compression.lzw.Decoder,{init:function(){
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| 56 | this.codes=new Array(this.size); |
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| 57 | for(var i=0;i<this.size;++i){ |
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| 58 | this.codes[i]=String.fromCharCode(i);
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| 59 | } |
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| 60 | this.width=_1(this.size); |
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| 61 | this.p=-1; |
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| 62 | },decode:function(_5){ |
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| 63 | var c=_5.getBits(this.width),v; |
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| 64 | if(c<this.codes.length){ |
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| 65 | v=this.codes[c];
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| 66 | if(this.p>=0){ |
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| 67 | this.codes.push(this.codes[this.p]+v.substr(0,1)); |
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| 68 | } |
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| 69 | }else{
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| 70 | if((c&(c+1))==0){ |
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| 71 | this.codes.push(""); |
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| 72 | ++this.width;
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| 73 | return ""; |
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| 74 | } |
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| 75 | var x=this.codes[this.p]; |
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| 76 | v=x+x.substr(0,1); |
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| 77 | this.codes.push(v);
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| 78 | } |
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| 79 | this.p=c;
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| 80 | return v;
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| 81 | }}); |
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| 82 | })(); |
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| 83 | } |