Issue #4694 - Add mutex protection to JS event handling

src/Event.cpp

+/*
+ * 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
+ * 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/>.
+ */
+
+#include "Event.h"
+
+void EventManager::Set(const std::string& eventName, AdblockPlus::JsEngine::EventCallback callback)
+{
+  UniqueLockType ul(m);
+  eventMap[eventName] = callback;
+}
+
+void EventManager::Remove(const std::string& eventName)
+{
+  UniqueLockType ul(m);
+  eventMap.erase(eventName);
+}
+
+/**
+ * \par Implementation Notes
+ *
+ * A triggered event runs with mutex unlocked.

[sergei, 2017/03/15 12:17:20]

I don't think we need this comment.

+ */
+void EventManager::Trigger(const std::string& eventName, AdblockPlus::JsValueList& args)
+{
+  AdblockPlus::JsEngine::EventCallback f;
+  {
+    // Find the callback with mutex locked

[sergei, 2017/03/15 12:17:20]

this comment is superfluous.

+    UniqueLockType ul(m);
+    auto it = eventMap.find(eventName);
+    if (it == eventMap.end())
+    {
+      return;
+    }
+    f = it->second;
+  }
+  // Execute the callback with mutex unlocked

[sergei, 2017/03/15 12:17:20]

this comment is superfluous.

+  f(args);
+}