1function StringMap() {
2    
3      this.stringToIndex = new Map();
4      this.indexToString = [];
5  
6      this.addString = function(str) {
7  
8      // If this string is known, just return its index
9      var index = this.stringToIndex.get(str);
10      if (index !== undefined) {
11          return index;
12      }
13      
14      // This is a new string. Add it to both maps.
15      index = this.indexToString.length;
16      this.indexToString.push(str);
17      this.stringToIndex.set(str, index);
18      return index;
19  };
20  
21  this.getString = function(index) {
22      return this.indexToString[index];
23  };
24  
25  this.addStrings = function(strArray) {
26      var indices = [];
27      for (var i=0; i<strArray.length; i++) {
28          var s = strArray[i];
29          var index = this.addString(s);
30          indices.push(index);
31      }
32      return indices;
33  };
34  
35  this.getStrings = function(indices) {
36      var strArray = [];
37      for (var i=0; i<indices.length; i++) {
38          var index = indices[i];
39          var str   = this.getString(index);
40          strArray.push(str);
41      }
42      return strArray;
43  };
44};
45window.stringMap = new StringMap();
46
47// Adds an array of style strings to the dictionary.
48// Returns an array of indices into the global string dictionary.
49window.packStyles = function(styles) {
50    return window.stringMap.addStrings(styles);
51};
52
53// Gets an array of indices into the string dictionary pointing to style strings.
54// Returns an array containing the original strings.
55window.unpackStyles = function(styles) {
56  
57    // Return identiy if styles is undefined or already unpacked
58    var isPacked = styles && (typeof styles[0] == "number");
59    if (!isPacked) {
60      return styles;
61    }
62    return window.stringMap.getStrings(styles);
63};