92 lines
2.1 KiB
JavaScript
92 lines
2.1 KiB
JavaScript
|
if(!dojo._hasResource["dojox.encoding.compression.lzw"]){ //_hasResource checks added by build. Do not use _hasResource directly in your code.
|
||
|
|
dojo._hasResource["dojox.encoding.compression.lzw"] = true;
|
||
|
|
dojo.provide("dojox.encoding.compression.lzw");
|
||
|
|
dojo.require("dojox.encoding.bits");
|
||
|
|
|
||
|
|
(function(){
|
||
|
|
var _bits = function(x){
|
||
|
|
var w = 1;
|
||
|
|
for(var v = 2; x >= v; v <<= 1, ++w);
|
||
|
|
return w;
|
||
|
|
};
|
||
|
|
|
||
|
|
dojox.encoding.compression.lzw.Encoder = function(n){
|
||
|
|
this.size = n;
|
||
|
|
this.init();
|
||
|
|
};
|
||
|
|
|
||
|
|
dojo.extend(dojox.encoding.compression.lzw.Encoder, {
|
||
|
|
init: function(){
|
||
|
|
this.dict = {};
|
||
|
|
for(var i = 0; i < this.size; ++i){
|
||
|
|
this.dict[String.fromCharCode(i)] = i;
|
||
|
|
}
|
||
|
|
this.width = _bits(this.code = this.size);
|
||
|
|
this.p = "";
|
||
|
|
},
|
||
|
|
encode: function(value, stream){
|
||
|
|
var c = String.fromCharCode(value), p = this.p + c, r = 0;
|
||
|
|
// if already in the dictionary
|
||
|
|
if(p in this.dict){
|
||
|
|
this.p = p;
|
||
|
|
return r;
|
||
|
|
}
|
||
|
|
stream.putBits(this.dict[this.p], this.width);
|
||
|
|
// if we need to increase the code length
|
||
|
|
if((this.code & (this.code + 1)) == 0){
|
||
|
|
stream.putBits(this.code++, r = this.width++);
|
||
|
|
}
|
||
|
|
// add new string
|
||
|
|
this.dict[p] = this.code++;
|
||
|
|
this.p = c;
|
||
|
|
return r + this.width;
|
||
|
|
},
|
||
|
|
flush: function(stream){
|
||
|
|
if(this.p.length == 0){
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
stream.putBits(this.dict[this.p], this.width);
|
||
|
|
this.p = "";
|
||
|
|
return this.width;
|
||
|
|
}
|
||
|
|
});
|
||
|
|
|
||
|
|
dojox.encoding.compression.lzw.Decoder = function(n){
|
||
|
|
this.size = n;
|
||
|
|
this.init();
|
||
|
|
};
|
||
|
|
|
||
|
|
dojo.extend(dojox.encoding.compression.lzw.Decoder, {
|
||
|
|
init: function(){
|
||
|
|
this.codes = new Array(this.size);
|
||
|
|
for(var i = 0; i < this.size; ++i){
|
||
|
|
this.codes[i] = String.fromCharCode(i);
|
||
|
|
}
|
||
|
|
this.width = _bits(this.size);
|
||
|
|
this.p = -1;
|
||
|
|
},
|
||
|
|
decode: function(stream){
|
||
|
|
var c = stream.getBits(this.width), v;
|
||
|
|
if(c < this.codes.length){
|
||
|
|
v = this.codes[c];
|
||
|
|
if(this.p >= 0){
|
||
|
|
this.codes.push(this.codes[this.p] + v.substr(0, 1));
|
||
|
|
}
|
||
|
|
}else{
|
||
|
|
if((c & (c + 1)) == 0){
|
||
|
|
this.codes.push("");
|
||
|
|
++this.width;
|
||
|
|
return "";
|
||
|
|
}
|
||
|
|
var x = this.codes[this.p];
|
||
|
|
v = x + x.substr(0, 1);
|
||
|
|
this.codes.push(v);
|
||
|
|
}
|
||
|
|
this.p = c;
|
||
|
|
return v;
|
||
|
|
}
|
||
|
|
});
|
||
|
|
})();
|
||
|
|
|
||
|
|
}
|