Subversion Repositories Applications.papyrus

Rev

Go to most recent revision | Details | Last modification | View Log | RSS feed

Rev Author Line No. Line
2150 mathias 1 
if(!dojo._hasResource["dojox.encoding.lzw"]){ //_hasResource checks added by build. Do not use _hasResource directly in your code.
2 
dojo._hasResource["dojox.encoding.lzw"] = true;
3 
dojo.provide("dojox.encoding.lzw");
4 
 
5 
(function(){
6 
	var _bits = function(x){
7 
		var w = 1;
8 
		for(var v = 2; x >= v; v <<= 1, ++w);
9 
		return w;
10 
	};
11 
 
12 
	dojox.encoding.lzw.Encoder = function(n){
13 
		this.size = n;
14 
		this.init();
15 
	};
16 
 
17 
	dojo.extend(dojox.encoding.lzw.Encoder, {
18 
		init: function(){
19 
			this.dict = {};
20 
			for(var i = 0; i < this.size; ++i){
21 
				this.dict[String.fromCharCode(i)] = i;
22 
			}
23 
			this.width = _bits(this.code = this.size);
24 
			this.p = "";
25 
		},
26 
		encode: function(value, stream){
27 
			var c = String.fromCharCode(value), p = this.p + c, r = 0;
28 
			// if already in the dictionary
29 
			if(p in this.dict){
30 
				this.p = p;
31 
				return r;
32 
			}
33 
			stream.putBits(this.dict[this.p], this.width);
34 
			// if we need to increase the code length
35 
			if((this.code & (this.code + 1)) == 0){
36 
				stream.putBits(this.code++, r = this.width++);
37 
			}
38 
			// add new string
39 
			this.dict[p] = this.code++;
40 
			this.p = c;
41 
			return r + this.width;
42 
		},
43 
		flush: function(stream){
44 
			if(this.p.length == 0){
45 
				return 0;
46 
			}
47 
			stream.putBits(this.dict[this.p], this.width);
48 
			this.p = "";
49 
			return this.width;
50 
		}
51 
	});
52 
 
53 
	dojox.encoding.lzw.Decoder = function(n){
54 
		this.size = n;
55 
		this.init();
56 
	};
57 
 
58 
	dojo.extend(dojox.encoding.lzw.Decoder, {
59 
		init: function(){
60 
			this.codes = new Array(this.size);
61 
			for(var i = 0; i < this.size; ++i){
62 
				this.codes[i] = String.fromCharCode(i);
63 
			}
64 
			this.width = _bits(this.size);
65 
			this.p = -1;
66 
		},
67 
		decode: function(stream){
68 
			var c = stream.getBits(this.width), v;
69 
			if(c < this.codes.length){
70 
				v = this.codes[c];
71 
				if(this.p >= 0){
72 
					this.codes.push(this.codes[this.p] + v.substr(0, 1));
73 
				}
74 
			}else{
75 
				if((c & (c + 1)) == 0){
76 
					this.codes.push("");
77 
					++this.width;
78 
					return "";
79 
				}
80 
				var x = this.codes[this.p];
81 
				v = x + x.substr(0, 1);
82 
				this.codes.push(v);
83 
			}
84 
			this.p = c;
85 
			return v;
86 
		}
87 
	});
88 
})();
89 
 
90 
}