Issue 3251 - Simplify messaging from child scripts to parent

lib/child/bootstrap.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2015 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
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 (function()
 {
   const Cc = Components.classes;
   const Ci = Components.interfaces;
   const Cr = Components.results;
   const Cu = Components.utils;
 
   let {Loader, main, unload} = Cu.import("resource://gre/modules/commonjs/toolkit/loader.js", {});
+  let {Services} = Cu.import("resource://gre/modules/Services.jsm", {});
 
   let loader = null;
 
   let shutdownHandlers = [];
   let onShutdown =
   {
     done: false,
     add: function(handler)
     {
       if (shutdownHandlers.indexOf(handler) < 0)
         shutdownHandlers.push(handler);
     },
     remove: function(handler)
     {
       let index = shutdownHandlers.indexOf(handler);
       if (index >= 0)
         shutdownHandlers.splice(index, 1);
     }
   };
 
   addMessageListener("AdblockPlus:Info", init);
   addMessageListener("AdblockPlus:Shutdown", shutdown);
 
   function init(message)
   {
     removeMessageListener("AdblockPlus:Info", init);
 
+    let callbackPrefix = Services.appinfo.processID + " ";
+    let maxCallbackID = 0;
+    let callbacks = new Map();
+
+    function sendSyncMessageSingleResponse(messageName, data)
+    {
+      let response = sendSyncMessage(messageName, {data})[0];
+      return typeof response == "string" ? JSON.parse(response) : response;
+    }
+
+    function sendAsyncMessageWithResponse(messageName, data, callback)

[Wladimir Palant, 2015/11/04 15:04:09]

Note that normally the third parameter for both sendSyncMessage and
sendAsyncMessage is objects. I think that explicitly disallowing it is a good
idea - with these objects being accessed via CPOWs it's a serious footgun.

+    {
+      data = {data};
+      if (callback)
+      {
+        let callbackID = callbackPrefix + (++maxCallbackID);
+        callbacks.set(callbackID, callback);
+        data.callbackID = callbackID;
+      }
+      sendAsyncMessage(messageName, data);
+    }
+
+    function onResponse(message)
+    {
+      let {callbackID, response} = message.data;
+      if (callbacks.has(callbackID))
+      {
+        let callback = callbacks.get(callbackID);
+        callbacks.delete(callbackID);
+        callback(response);
+      }
+    }
+    addMessageListener("AdblockPlus:Response", onResponse);
+    onShutdown.add(() => removeMessageListener("AdblockPlus:Response", onResponse));
+
     let info = message.data;
     loader = Loader({
       paths: {
         "": info.addonRoot + "lib/"
       },
       globals: {
         Components, Cc, Ci, Cu, Cr, atob, btoa, onShutdown,
-        addMessageListener, removeMessageListener, sendAsyncMessage, sendSyncMessage
+        addMessageListener, removeMessageListener,
+        sendAsyncMessage: sendAsyncMessageWithResponse,
+        sendSyncMessage: sendSyncMessageSingleResponse
       },
       modules: {"info": info},
       id: info.addonID
     });
     onShutdown.add(() => unload(loader, "disable"))
 
     main(loader, "child/main");
   }
 
   function shutdown(message)
@@ skipping 12 matching lines @@
         catch (e)
         {
           Cu.reportError(e);
         }
       }
       shutdownHandlers = null;
     }
   }
 })();