Repo created

libs/base/observer_list.hpp

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+#pragma once
+
+#include "base/logging.hpp"
+
+#include <algorithm>
+#include <mutex>
+#include <utility>
+#include <vector>
+
+namespace base
+{
+class DummyLockable
+{
+public:
+  void lock() {}
+  void unlock() {}
+};
+
+template <typename Observer, typename Mutex>
+class ObserverList;
+
+/// This alias represents a thread-safe observers list.  It allows to
+/// add/remove observers as well as trigger them all.
+template <typename Observer>
+using ObserverListSafe = ObserverList<Observer, std::mutex>;
+
+template <typename Observer>
+using ObserverListUnsafe = ObserverList<Observer, DummyLockable>;
+
+template <typename Observer, typename Mutex>
+class ObserverList
+{
+public:
+  bool Add(Observer & observer)
+  {
+    std::lock_guard<Mutex> lock(m_observersLock);
+    auto const it = std::find(m_observers.begin(), m_observers.end(), &observer);
+    if (it != m_observers.end())
+    {
+      LOG(LWARNING, ("Can't add the same observer twice:", &observer));
+      return false;
+    }
+    m_observers.push_back(&observer);
+    return true;
+  }
+
+  bool Remove(Observer const & observer)
+  {
+    std::lock_guard<Mutex> lock(m_observersLock);
+    auto const it = std::find(m_observers.begin(), m_observers.end(), &observer);
+    if (it == m_observers.end())
+    {
+      LOG(LWARNING, ("Can't remove non-registered observer:", &observer));
+      return false;
+    }
+    m_observers.erase(it);
+    return true;
+  }
+
+  template <typename F, typename... Args>
+  void ForEach(F fn, Args const &... args)
+  {
+    std::lock_guard<Mutex> lock(m_observersLock);
+    for (Observer * observer : m_observers)
+      (observer->*fn)(args...);
+  }
+
+private:
+  Mutex m_observersLock;
+  std::vector<Observer *> m_observers;
+};
+}  // namespace base