Issue 4067 - Make filter "keys" generated for element hiding filters numeric

lib/elemHide.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 13 matching lines @@
 var {Utils} = require("utils");
 var {IO} = require("io");
 var {Prefs} = require("prefs");
 var {ElemHideException} = require("filterClasses");
 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
  * @type Object
  */
 var keyByFilter = Object.create(null);
 
 /**
  * Nested lookup table, filter (or false if inactive) by filter text by domain
  * @type Object
@@ skipping 64 matching lines @@
     let styleFile = IO.resolveFilePath(Prefs.data_directory);
     styleFile.append("elemhide.css");
     styleURL = Services.io.newFileURI(styleFile).QueryInterface(Ci.nsIFileURL);
   },
 
   /**
    * Removes all known filters
    */
   clear: function()
   {
-    filterByKey = Object.create(null);
+    filterByKey = [];
     keyByFilter = Object.create(null);
     filtersByDomain = Object.create(null);
     knownExceptions = Object.create(null);
     exceptions = Object.create(null);
     ElemHide.isDirty = false;
     ElemHide.unapply();
   },
 
   /**
    * Add a new element hiding filter
@@ skipping 10 matching lines @@
       if (!(selector in exceptions))
         exceptions[selector] = [];
       exceptions[selector].push(filter);
       knownExceptions[filter.text] = true;
     }
     else
     {
       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 (usingFiltersByDomain)
       {
         let domains = filter.domains || defaultDomains;
         for (let domain in domains)
         {
           let filters = filtersByDomain[domain];
           if (!filters)
             filters = filtersByDomain[domain] = Object.create(null);
@@ skipping 161 matching lines @@
   },
 
   _generateCSSContent: function*()
   {
     // Grouping selectors by domains
     let domains = Object.create(null);
     let hasFilters = false;
     for (let key in filterByKey)
     {
       let filter = filterByKey[key];
+      let selector = filter.selector;
+      if (!selector)

[kzar, 2016/05/24 12:36:49]

I'm curious why you added this check? Wont all element hiding filters have a
selector?

[Wladimir Palant, 2016/05/24 12:49:50]

From
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/...:
Luckily, array properties like join() aren't enumerable and shouldn't show up
here. Still, I thought it's a good idea to verify that we actually have a filter
here, not some method.

[kzar, 2016/05/24 12:57:45]

Acknowledged.

+        continue;
+
       let domain = filter.selectorDomain || "";
 
       let list;
       if (domain in domains)
         list = domains[domain];
       else
       {
         list = Object.create(null);
         domains[domain] = list;
       }
-      list[filter.selector] = key;
+      list[selector] = key;
       hasFilters = true;
     }
 
     if (!hasFilters)
       throw Cr.NS_ERROR_NOT_AVAILABLE;
 
     function escapeChar(match)
     {
       return "\\" + match.charCodeAt(0).toString(16) + " ";
     }
@@ skipping 93 matching lines @@
       if (currentDomain == "")
         break;
 
       let nextDot = currentDomain.indexOf(".");
       currentDomain = nextDot == -1 ? "" : currentDomain.substr(nextDot + 1);
     }
 
     return selectors;
   }
 };