Issue 5179 - Implement asynchronous executor with a controllable lifetime

include/AdblockPlus/ActiveObject.h

+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-present 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/>.
+ */
+#pragma once
+#include <list>
+#include <thread>
+#include <functional>
+#include "SynchronizedCollection.h"
+
+namespace AdblockPlus
+{
+  /**
+   * The implementation of active object pattern, simply put it sequentially
+   * executes posted callable objects in a single background thread.
+   * In the destructor it waits for the finishing of all already posted calls.
+   */
+  class ActiveObject {
+  public:
+    /**
+     * A callable object type, in fact wrapping std::function.
+     */
+    typedef std::function<void()> Call;
+
+    /**
+     * Constructor, the background thread is started after finishing this call.
+     */
+    ActiveObject();
+
+    /**
+     * Destructor, it waits for finishing of all already posted calls.
+     */
+    ~ActiveObject();
+    /**
+     * Adds the `call`, which should be executed in the worker thread to the
+     * end of the internally held list.
+     * @param call object.
+     */
+    void Post(const Call& call);
+    void Post(Call&& call);
+  private:
+    void ThreadFunc();
+  private:
+    bool isRunning;
+    SynchronizedCollection<std::list<Call>> calls;
+    std::thread thread;
+  };
+}