Issue 5161 - Use maps and sets where appropriate

ext/background.js

Index: ext/background.js
===================================================================
--- a/ext/background.js
+++ b/ext/background.js
@@ -14,64 +14,67 @@
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 "use strict";
 
 (function()
 {
-  let nonEmptyPageMaps = Object.create(null);
-  let pageMapCounter = 0;
+  let nonEmptyPageMaps = new Set();
 
   let PageMap = ext.PageMap = function()
   {
-    this._map = Object.create(null);
-    this._id = ++pageMapCounter;
+    this._map = new Map();
   };
   PageMap.prototype = {
     _delete(id)
     {
-      delete this._map[id];
-
-      if (Object.keys(this._map).length == 0)
-        delete nonEmptyPageMaps[this._id];
+      if (this._map.delete(id) && this._map.size == 0)
+        nonEmptyPageMaps.delete(this);
     },
     keys()
     {
-      return Object.keys(this._map).map(ext.getPage);
+      return this._map.keys();
     },
     get(page)
     {
-      return this._map[page.id];
+      return this._map.get(page.id);
     },
     set(page, value)
     {
-      this._map[page.id] = value;
-      nonEmptyPageMaps[this._id] = this;
+      let prevSize = this._map.size;
+
+      this._map.set(page.id, value);
+
+      if (prevSize == 0)
+        nonEmptyPageMaps.add(this);
     },
     has(page)
     {
-      return page.id in this._map;
+      return this._map.has(page.id);
     },
     clear()
     {
-      for (let id in this._map)
-        this._delete(id);
+      if (this._map.size == 0)
+        return;
+
+      this._map.clear();
+      nonEmptyPageMaps.delete(this);
     },
     delete(page)
     {
       this._delete(page.id);
     }
   };
 
   ext._removeFromAllPageMaps = pageId =>
   {
-    for (let pageMapId in nonEmptyPageMaps)
-      nonEmptyPageMaps[pageMapId]._delete(pageId);
+    for (let pageMap of nonEmptyPageMaps)
+      pageMap._delete(pageId);
   };
 
   /* Pages */
 
   let Page = ext.Page = function(tab)
   {
     this.id = tab.id;
     this._url = tab.url && new URL(tab.url);
@@ -85,20 +88,20 @@
       // usually our Page objects are created from Chrome's Tab objects, which
       // provide the url. So we can return the url given in the constructor.
       if (this._url)
         return this._url;
 
       // but sometimes we only have the tab id when we create a Page object.
       // In that case we get the url from top frame of the tab, recorded by
       // the onBeforeRequest handler.
-      let frames = framesOfTabs[this.id];
+      let frames = framesOfTabs.get(this.id);
       if (frames)
       {
-        let frame = frames[0];
+        let frame = frames.get(0);
         if (frame)
           return frame.url;
       }
     },
     sendMessage(message, responseCallback)
     {
       chrome.tabs.sendMessage(this.id, message, responseCallback);
     }
@@ -153,23 +156,29 @@
   chrome.tabs.onUpdated.addListener((tabId, changeInfo, tab) =>
   {
     if (changeInfo.status == "loading")
       ext.pages.onLoading._dispatch(new Page(tab));
   });
 
   function createFrame(tabId, frameId)
   {
-    let frames = framesOfTabs[tabId];
+    let frames = framesOfTabs.get(tabId);
     if (!frames)
-      frames = framesOfTabs[tabId] = Object.create(null);
+    {
+      frames = new Map();
+      framesOfTabs.set(tabId, frames);
+    }
 
-    let frame = frames[frameId];
+    let frame = frames.get(frameId);
     if (!frame)
-      frame = frames[frameId] = {};
+    {
+      frame = {};
+      frames.set(frameId, frame);
+    }
 
     return frame;
   }
 
   function updatePageFrameStructure(frameId, tabId, url, parentFrameId)
   {
     if (frameId == 0)
     {
@@ -185,20 +194,23 @@
         // However, we have to keep relying on the unUpdated event for tabs that
         // are already visible. Otherwise browser action changes get overridden
         // when Chrome automatically resets them on navigation.
         if (chrome.runtime.lastError)
           ext.pages.onLoading._dispatch(page);
       });
     }
 
-    // Update frame parent and URL in frame structure
+    // Update frame URL and parent in frame structure
     let frame = createFrame(tabId, frameId);
     frame.url = new URL(url);
-    frame.parent = framesOfTabs[tabId][parentFrameId] || null;
+
+    let parentFrame = framesOfTabs.get(tabId).get(parentFrameId);
+    if (parentFrame)
+      frame.parent = parentFrame;
   }
 
   chrome.webRequest.onHeadersReceived.addListener(details =>
   {
     // We have to update the frame structure when switching to a new
     // document, so that we process any further requests made by that
     // document in the right context. Unfortunately, we cannot rely
     // on webNavigation.onCommitted since it isn't guaranteed to fire
@@ -287,17 +299,17 @@
     }
   });
 
   function forgetTab(tabId)
   {
     ext.pages.onRemoved._dispatch(tabId);
 
     ext._removeFromAllPageMaps(tabId);
-    delete framesOfTabs[tabId];
+    framesOfTabs.delete(tabId);
   }
 
   chrome.tabs.onReplaced.addListener((addedTabId, removedTabId) =>
   {
     forgetTab(removedTabId);
   });
 
   chrome.tabs.onRemoved.addListener(forgetTab);
@@ -485,21 +497,22 @@
   {
     if (windowId != chrome.windows.WINDOW_ID_NONE)
       updateContextMenu();
   });
 
 
   /* Web requests */
 
-  let framesOfTabs = Object.create(null);
+  let framesOfTabs = new Map();
 
   ext.getFrame = (tabId, frameId) =>
   {
-    return (framesOfTabs[tabId] || {})[frameId];
+    let frames = framesOfTabs.get(tabId);
+    return frames && frames.get(frameId);
   };
 
   let handlerBehaviorChangedQuota =
     chrome.webRequest.MAX_HANDLER_BEHAVIOR_CHANGED_CALLS_PER_10_MINUTES;
 
   function propagateHandlerBehaviorChange()
   {
     // Make sure to not call handlerBehaviorChanged() more often than allowed
@@ -534,32 +547,28 @@
   chrome.tabs.query({}, tabs =>
   {
     tabs.forEach(tab =>
     {
       chrome.webNavigation.getAllFrames({tabId: tab.id}, details =>
       {
         if (details && details.length > 0)
         {
-          let frames = framesOfTabs[tab.id] = Object.create(null);
+          let frames = new Map();
+          framesOfTabs.set(tab.id, frames);
 
-          for (let i = 0; i < details.length; i++)
+          for (let detail of details)
+            frames.set(detail.frameId, {url: new URL(detail.url)});
+
+          for (let detail of details)
           {
-            frames[details[i].frameId] = {
-              url: new URL(details[i].url),
-              parent: null
-            };
-          }
-
-          for (let i = 0; i < details.length; i++)
-          {
-            let {parentFrameId} = details[i];
+            let {parentFrameId} = detail;
 
             if (parentFrameId != -1)
-              frames[details[i].frameId].parent = frames[parentFrameId];
+              frames.get(detail.frameId).parent = frames.get(parentFrameId);
           }
         }
       });
     });
   });
 
   chrome.webRequest.onBeforeRequest.addListener(details =>
   {
@@ -606,26 +615,26 @@
     // If sent by popup or the background page itself, there is no "tab".
     if ("tab" in rawSender)
     {
       sender.page = new Page(rawSender.tab);
       sender.frame = {
         url: new URL(rawSender.url),
         get parent()
         {
-          let frames = framesOfTabs[rawSender.tab.id];
+          let frames = framesOfTabs.get(rawSender.tab.id);
 
           if (!frames)
             return null;
 
-          let frame = frames[rawSender.frameId];
+          let frame = frames.get(rawSender.frameId);
           if (frame)
-            return frame.parent;
+            return frame.parent || null;
 
-          return frames[0];
+          return frames.get(0) || null;
         }
       };
     }
 
     return ext.onMessage._dispatch(
       message, sender, sendResponse
     ).indexOf(true) != -1;
   });