Noissue - generalize storing of `JsValue`s in `JsEngine`

include/AdblockPlus/JsEngine.h

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 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 71 matching lines @@
   typedef std::shared_ptr<ScopedV8Isolate> ScopedV8IsolatePtr;
 
   /**
    * JavaScript engine used by `FilterEngine`, wraps v8.
    */
   class JsEngine : public std::enable_shared_from_this<JsEngine>
   {
     friend class JsValue;
     friend class JsContext;
 
+    struct JsWeakValuesList
+    {
+      ~JsWeakValuesList();
+      std::vector<std::unique_ptr<v8::Persistent<v8::Value>>> values;
+    };
+    typedef std::list<JsWeakValuesList> JsWeakValuesLists;
   public:
     /**
      * Event callback function.
      */
     typedef std::function<void(JsValueList&& params)> EventCallback;
 
     /**
     * Callback function returning false when current connection is not allowed
     * e.g. because it is a metered connection.
     */
     typedef std::function<bool()> IsConnectionAllowedCallback;
 
     /**
      * Maps events to callback functions.
      */
     typedef std::map<std::string, EventCallback> EventMap;
 
     /**
+     * An opaque structure representing ID of stored JsValueList.
+     * 
+     */
+    class JsWeakValuesID
+    {
+      friend class JsEngine;
+      JsWeakValuesLists::const_iterator iterator;
+    };
+
+    /**
      * Creates a new JavaScript engine instance.
      * @param appInfo Information about the app.
      * @param timer Implementation of timer.
      * @param isolate v8::Isolate wrapper. This parameter should be considered
      *        as a temporary hack for tests, it will go away. Issue #3593.
      * @return New `JsEngine` instance.
      */
     static JsEnginePtr New(const AppInfo& appInfo = AppInfo(),
       TimerPtr timer = CreateDefaultTimer(),
       const ScopedV8IsolatePtr& isolate = ScopedV8IsolatePtr(new ScopedV8Isolate()));
@@ skipping 77 matching lines @@
     /**
      * Returns a `JsEngine` instance contained in a `v8::Arguments` object.
      * Use this in callbacks created via `NewCallback()` to retrieve the current
      * `JsEngine`.
      * @param arguments `v8::Arguments` object containing the `JsEngine`
      *        instance.
      * @return `JsEngine` instance from `v8::Arguments`.
      */
     static JsEnginePtr FromArguments(const v8::Arguments& arguments);
 
+    /**
+     * Stores `JsValue`s in a way they don't keep a strong reference to
+     * `JsEngine` and which are destroyed when `JsEngine` is destroyed. These
+     * methods should be used when one needs to carry a JsValue in a callback
+     * directly or indirectly passed to `JsEngine`.
+     * The method is thread-safe.
+     * @param `JsValueList` to store.
+     * @return `JsWeakValuesID` of stored values which allows to restore them
+     * later.
+     */
+    JsWeakValuesID StoreJsValues(const JsValueList& values);
+    /**
+     * Extracts and removes from `JsEngine` earlier stored `JsValue`s.
+     * The method is thread-safe.
+     * @param id `JsWeakValuesID` of values.
+     * @return `JsValueList` of stored values.
+     */
+    JsValueList TakeJsValues(const JsWeakValuesID& id);
+
     /*
      * Private functionality required to implement timers.
      * @param arguments `v8::Arguments` is the arguments received in C++
      * callback associated for global setTimeout method.
      */
     static void ScheduleTimer(const v8::Arguments& arguments);
 
     /**
      * Converts v8 arguments to `JsValue` objects.
      * @param arguments `v8::Arguments` object containing the arguments to
@@ skipping 64 matching lines @@
 
     /**
      * Returns a pointer to associated v8::Isolate.
      */
     v8::Isolate* GetIsolate()
     {
       return isolate->Get();
     }
 
   private:
-    struct TimerTask
-    {
-      ~TimerTask();
-      std::vector<std::unique_ptr<v8::Persistent<v8::Value>>> arguments;
-    };
-    typedef std::list<TimerTask> TimerTasks;
-    void CallTimerTask(const TimerTasks::const_iterator& timerTaskIterator);
+    void CallTimerTask(const JsWeakValuesID& timerParamsID);
 
     explicit JsEngine(const ScopedV8IsolatePtr& isolate, TimerPtr timer);
 
     JsValue GetGlobalObject();
 
     /// Isolate must be disposed only after disposing of all objects which are
     /// using it.
     ScopedV8IsolatePtr isolate;
 
     FileSystemPtr fileSystem;
     WebRequestPtr webRequest;
     LogSystemPtr logSystem;
     std::unique_ptr<v8::Persistent<v8::Context>> context;
     EventMap eventCallbacks;
     std::mutex eventCallbacksMutex;
     mutable std::mutex isConnectionAllowedMutex;
     IsConnectionAllowedCallback isConnectionAllowed;
-    TimerTasks timerTasks;
+    JsWeakValuesLists jsWeakValuesLists;
+    std::mutex jsWeakValuesListsMutex;
     TimerPtr timer;
   };
 }
 
 #endif