Issue #1652, #3456 - Replace 's_asyncWebBrowser2' with thread-safe facilities

src/plugin/Instances.h

Index: src/plugin/Instances.h
===================================================================
new file mode 100644
--- /dev/null
+++ b/src/plugin/Instances.h
@@ -0,0 +1,112 @@
+/*

[Oleksandr, 2016/02/01 18:03:14]

Nit: This file is also being added in
https://codereview.adblockplus.org/29330403/. I'm guessing this review builds on
top of that one?

[Eric, 2016/02/03 14:57:28]

No. I made sure they were not interdependent. The idea, though, is that both
'SyncSet' and 'SyncMap' end up in the same source file, since they are related
classes that each deal with containers of BHO instances.

+ * 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/>.
+ */
+
+#ifndef _INSTANCES_H_
+#define _INSTANCES_H_
+
+#include <mutex>
+#include <set>
+
+/**
+ * Template class for a synchronized set of BHO instances
+ */
+template<class T, T nullValue>
+class SyncSet
+{
+  typedef std::lock_guard<std::mutex> SentryType;
+
+  /**
+   * Underlying set container
+   */
+  std::set<T> set;
+
+  /**
+   * Synchronization primitive
+   */
+  mutable std::mutex mutex;
+
+public:
+  /**
+   * \return
+   *   true if (as expected) the argument was not already a member of the set
+   *   false otherwise
+   *
+   * \par Postcondition
+   *   - argument is a member of the set
+   */
+  bool InsertIfAbsent(T p)
+  {
+    SentryType sentry(mutex);
+    auto it = set.find(p);
+    if (it != set.end())
+    {
+      return false;
+    }
+    set.insert(p);
+    return true;
+  }
+
+  /**
+   * \return
+   *   true if (as expected) the argument was already a member of the set
+   *   false otherwise
+   *
+   * \par Postcondition
+   *   - argument is not a member of the set
+   */
+  bool EraseWithCheck(T p)
+  {
+    SentryType sentry(mutex);
+    auto it = set.find(p);
+    if (it == set.end())
+    {
+      return false;
+    }
+    set.erase(it);
+    return true;
+  }
+
+  /**
+   * \param f
+   *   Search criterion is a simple predicate function 
+   *
+   * \return
+   *   - If no member of the set meets the search criterion, the null value
+   *   - Otherwise some member of the set that meets the search criterion
+   */
+  T LinearSearch(std::function<bool(T)> f)
+  {
+    SentryType sentry(mutex);
+    for (auto member : set)
+    {
+      bool b = f(member);
+      if (b)
+      {
+        return member;
+      }
+    }
+    return nullValue;
+  }
+
+  bool Empty() const
+  {
+    SentryType sentry(mutex);
+    return set.empty();
+  }
+};
+
+#endif