Issue 4057 - Use keyByFilter array lookup for seenFilters

Author: kzar

lib/elemHide.js

@@ -31,7 +31,7 @@ var {FilterNotifier} = require("filterNotifier");
  * Lookup table, filters by their associated key
  * @type Object
  */
-var filterByKey = Object.create(null);
+var filterByKey = [];
 
 /**
  * Lookup table, keys of the filters by filter text
@@ -125,7 +125,7 @@ var ElemHide = exports.ElemHide =
    */
   clear: function()
   {
-    filterByKey = Object.create(null);
+    filterByKey = [];
     keyByFilter = Object.create(null);
     filtersByDomain = Object.create(null);
     filtersBySelector = Object.create(null);
@@ -138,6 +138,7 @@ var ElemHide = exports.ElemHide =
 
   _addToFiltersByDomain: function(filter)
   {
+    let key = keyByFilter[filter.text];
     let domains = filter.domains || defaultDomains;
     for (let domain in domains)
     {
@@ -146,9 +147,9 @@ var ElemHide = exports.ElemHide =
         filters = filtersByDomain[domain] = Object.create(null);
 
       if (domains[domain])
-        filters[filter.text] = filter;
+        filters[key] = filter;
       else
-        filters[filter.text] = false;
+        filters[key] = false;
     }
   },
 
@@ -191,12 +192,7 @@ var ElemHide = exports.ElemHide =
       if (filter.text in keyByFilter)
         return;
 
-      let key;
-      do {
-        key = Math.random().toFixed(15).substr(5);
-      } while (key in filterByKey);
-
-      filterByKey[key] = filter;
+      let key = filterByKey.push(filter) - 1;
       keyByFilter[filter.text] = key;
 
       if (usingGetSelectorsForDomain)
@@ -268,7 +264,7 @@ var ElemHide = exports.ElemHide =
           {
             let filters = filtersByDomain[domain];
             if (filters)
-              delete filters[filter.text];
+              delete filters[key];
           }
         }
       }
@@ -496,13 +492,13 @@ var ElemHide = exports.ElemHide =
       let filters = filtersByDomain[currentDomain];
       if (filters)
       {
-        for (let filterText in filters)
+        for (let filterKey in filters)
         {
-          if (filterText in seenFilters)
+          if (filterKey in seenFilters)
             continue;
-          seenFilters[filterText] = true;
+          seenFilters[filterKey] = true;
 
-          let filter = filters[filterText];
+          let filter = filters[filterKey];
           if (filter && !this.getException(filter, domain))
             selectors.push(filter.selector);
         }