New cpp folder structure

Signed-off-by: Alexander Borsuk <me@alex.bio>

libs/drape_frontend/drape_engine_safe_ptr.hpp

@@ -0,0 +1,75 @@
+#pragma once
+
+#include "base/macros.hpp"
+
+#include "drape/drape_global.hpp"
+#include "drape/pointers.hpp"
+
+#include <mutex>
+
+namespace df
+{
+class DrapeEngine;
+
+class DrapeEngineSafePtr
+{
+public:
+  void Set(ref_ptr<DrapeEngine> engine)
+  {
+    std::lock_guard<std::mutex> lock(m_mutex);
+    m_engine = engine;
+  }
+
+  explicit operator bool()
+  {
+    std::lock_guard<std::mutex> lock(m_mutex);
+    return m_engine != nullptr;
+  }
+
+  template <typename Function, typename ... Args>
+  void SafeCall(Function && f, Args && ... functionArgs)
+  {
+    std::lock_guard<std::mutex> lock(m_mutex);
+    if (m_engine != nullptr)
+      (m_engine.get()->*f)(std::forward<Args>(functionArgs)...);
+  }
+
+  template <typename Function, typename ... Args>
+  dp::DrapeID SafeCallWithResult(Function && f, Args && ... functionArgs)
+  {
+    std::lock_guard<std::mutex> lock(m_mutex);
+    if (m_engine != nullptr)
+      return (m_engine.get()->*f)(std::forward<Args>(functionArgs)...);
+    return dp::DrapeID();
+  }
+
+private:
+  ref_ptr<DrapeEngine> m_engine;
+  std::mutex m_mutex;
+
+  friend class DrapeEngineLockGuard;
+};
+
+class DrapeEngineLockGuard
+{
+public:
+  explicit DrapeEngineLockGuard(DrapeEngineSafePtr & enginePtr)
+    : m_ptr(enginePtr)
+  {
+    m_ptr.m_mutex.lock();
+  }
+
+  ~DrapeEngineLockGuard()
+  {
+    m_ptr.m_mutex.unlock();
+  }
+
+  explicit operator bool() { return m_ptr.m_engine != nullptr; }
+
+  ref_ptr<DrapeEngine> Get() { return m_ptr.m_engine; }
+
+private:
+  DrapeEngineSafePtr & m_ptr;
+  DISALLOW_COPY_AND_MOVE(DrapeEngineLockGuard);
+};
+}  // namespace df