Add ecs ComponentListener

- Add ecs ComponentListener which listens to Component addition and
  removal
- Add RefCounter class used to keep track of moves and copies

CopiumEngine/CopiumEngine.vcxproj

@@ -180,6 +180,7 @@
     <ClCompile Include="src\copium\core\Scene.cpp" />
     <ClCompile Include="src\copium\core\Vulkan.cpp" />
     <ClCompile Include="src\copium\core\Window.cpp" />
+    <ClCompile Include="src\copium\ecs\ComponentListener.cpp" />
     <ClCompile Include="src\copium\ecs\ComponentPoolBase.cpp" />
     <ClCompile Include="src\copium\ecs\ECSManager.cpp" />
     <ClCompile Include="src\copium\ecs\Entity.cpp" />
@@ -213,6 +214,7 @@
     <ClCompile Include="src\copium\pipeline\DescriptorSet.cpp" />
     <ClCompile Include="src\copium\sampler\Font.cpp" />
     <ClCompile Include="src\copium\util\BoundingBox.cpp" />
+    <ClCompile Include="src\copium\util\RefCounter.cpp" />
     <ClCompile Include="src\copium\util\RuntimeException.cpp" />
     <ClCompile Include="src\copium\util\FileSystem.cpp" />
     <ClCompile Include="src\copium\buffer\Framebuffer.cpp" />
@@ -249,6 +251,7 @@
     <ClInclude Include="src\copium\core\Scene.h" />
     <ClInclude Include="src\copium\core\Vulkan.h" />
     <ClInclude Include="src\copium\core\Window.h" />
+    <ClInclude Include="src\copium\ecs\ComponentListener.h" />
     <ClInclude Include="src\copium\ecs\ComponentPool.h" />
     <ClInclude Include="src\copium\ecs\ComponentPoolBase.h" />
     <ClInclude Include="src\copium\ecs\Config.h" />
@@ -280,6 +283,9 @@
     <ClInclude Include="src\copium\example\CameraUpdateSystem.h" />
     <ClInclude Include="src\copium\example\Components.h" />
     <ClInclude Include="src\copium\example\FrameCountSystem.h" />
+    <ClInclude Include="src\copium\example\HealthChangeSystem.h" />
+    <ClInclude Include="src\copium\example\HealthComponentListener.h" />
+    <ClInclude Include="src\copium\example\HealthDisplaySystem.h" />
     <ClInclude Include="src\copium\example\PhysicsSystem.h" />
     <ClInclude Include="src\copium\example\PlayerControllerSystem.h" />
     <ClInclude Include="src\copium\example\RenderSystem.h" />
@@ -302,6 +308,7 @@
     <ClInclude Include="src\copium\pipeline\DescriptorSet.h" />
     <ClInclude Include="src\copium\pipeline\DescriptorPool.h" />
     <ClInclude Include="src\copium\util\Enum.h" />
+    <ClInclude Include="src\copium\util\RefCounter.h" />
     <ClInclude Include="src\copium\util\RuntimeException.h" />
     <ClInclude Include="src\copium\util\FileSystem.h" />
     <ClInclude Include="src\copium\buffer\Framebuffer.h" />

CopiumEngine/CopiumEngine.vcxproj.filters

@@ -219,6 +219,12 @@
     <ClCompile Include="src\copium\event\Input.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="src\copium\util\RefCounter.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="src\copium\ecs\ComponentListener.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="src\copium\sampler\DepthAttachment.h">
@@ -485,5 +491,20 @@
     <ClInclude Include="src\copium\example\CameraFollowPlayerSystem.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="src\copium\example\HealthDisplaySystem.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="src\copium\example\HealthChangeSystem.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="src\copium\util\RefCounter.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="src\copium\ecs\ComponentListener.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="src\copium\example\HealthComponentListener.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>

CopiumEngine/src/copium/asset/AssetRef.cpp

@@ -5,51 +5,17 @@
 namespace Copium
 {
   AssetRef::AssetRef(AssetHandle handle)
-    : handle{handle}, refCounter{new int{1}}
+    : handle{handle}
   {}
 
   AssetRef::~AssetRef()
   {
-    if (refCounter == nullptr)
+    if (refCounter.LastRef())
-      return;
-
-    (*refCounter)--;
-    if (*refCounter == 0) 
     {
       AssetManager::UnloadAsset(handle);
-      delete refCounter;
     }
   }
 
-  AssetRef::AssetRef(const AssetRef& other)
-    : handle{other.handle}, refCounter{other.refCounter}
-  {
-    (*refCounter)++;
-  }
-
-  AssetRef::AssetRef(AssetRef&& other)
-    : handle{other.handle}, refCounter{other.refCounter}
-  {
-    other.refCounter = nullptr;
-  }
-
-  AssetRef& AssetRef::operator=(const AssetRef& rhs)
-  {
-    handle = rhs.handle;
-    refCounter = rhs.refCounter;
-
-    (*refCounter)++;
-    return *this;
-  }
-
-  AssetRef& AssetRef::operator=(AssetRef&& rhs)
-  {
-    handle = rhs.handle;
-    refCounter = rhs.refCounter;
-    rhs.refCounter = nullptr;
-    return *this;
-  }
-
   AssetRef::operator AssetHandle() const
   {
     return handle;

CopiumEngine/src/copium/asset/AssetRef.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "copium/asset/AssetMeta.h"
+#include "copium/util/RefCounter.h"
 
 namespace Copium
 {
@@ -8,18 +9,12 @@ namespace Copium
   {
   private:
     AssetHandle handle;
-    int* refCounter;
+    RefCounter refCounter;
 
   public:
     AssetRef(AssetHandle handle);
     ~AssetRef();
 
-    AssetRef(const AssetRef& other);
-    AssetRef(AssetRef&& other);
-
-    AssetRef& operator=(const AssetRef& rhs);
-    AssetRef& operator=(AssetRef&& rhs);
-
     operator AssetHandle() const;
   };
 

CopiumEngine/src/copium/core/Application.cpp

@@ -77,7 +77,7 @@ namespace Copium
     Vulkan::GetSwapChain().SubmitToGraphicsQueue(*commandBuffer);
 
     Vulkan::GetSwapChain().EndPresent();
-    return !glfwWindowShouldClose(Vulkan::GetWindow().GetWindow());
+    return !Vulkan::GetWindow().ShouldClose();
   }
 
   EventResult Application::OnEvent(const Event& event)
@@ -100,13 +100,6 @@ namespace Copium
 
       return EventResult::Focus;
     }
-    case EventType::KeyPress:
-    {
-      const KeyPressEvent& keyPressEvent = static_cast<const KeyPressEvent&>(event);
-      CP_INFO("%d", keyPressEvent.GetButton());
-
-      return EventResult::Handled;
-    }
     case EventType::MouseScroll:
     {
       const MouseScrollEvent& mouseScrollEvent = static_cast<const MouseScrollEvent&>(event);

CopiumEngine/src/copium/core/Scene.cpp

@@ -7,14 +7,17 @@
 #include "copium/ecs/Entity.h"
 #include "copium/ecs/System.h"
 #include "copium/event/MouseMoveEvent.h"
+#include "copium/example/CameraFollowPlayerSystem.h"
 #include "copium/example/CameraUpdateSystem.h"
 #include "copium/example/Components.h"
 #include "copium/example/FrameCountSystem.h"
+#include "copium/example/HealthChangeSystem.h"
+#include "copium/example/HealthComponentListener.h"
+#include "copium/example/HealthDisplaySystem.h"
 #include "copium/example/MouseFollowSystem.h"
-#include "copium/example/RenderSystem.h"
 #include "copium/example/PhysicsSystem.h"
 #include "copium/example/PlayerControllerSystem.h"
-#include "copium/example/CameraFollowPlayerSystem.h"
+#include "copium/example/RenderSystem.h"
 
 #include <glm/glm.hpp>
 #include <glm/gtc/matrix_transform.hpp>
@@ -30,11 +33,14 @@ namespace Copium
 
     ecs->AddSystem<PlayerControllerSystem>();
     ecs->AddSystem<PhysicsSystem>();
+    ecs->AddSystem<HealthChangeSystem>();
+    ecs->AddSystem<HealthDisplaySystem>();
     ecs->AddSystem<CameraFollowPlayerSystem>();
     ecs->AddSystem<CameraUpdateSystem>(&viewMatrix, &projectionMatrix, &invPvMatrix);
     ecs->AddSystem<MouseFollowSystem>(&invPvMatrix);
     ecs->AddSystem<FrameCountSystem>();
     ecs->AddSystem<RenderSystem>(renderer.get(), descriptorSetRenderer.get(), &commandBuffer, &viewMatrix, &projectionMatrix); // better way to store the RenderSystem data?
+    ecs->SetComponentListener<HealthComponentListener>();
 
     // TODO: Load from scene file
     for (int y = 0; y < 10; y++)
@@ -72,6 +78,7 @@ namespace Copium
 
     Entity entityPlayer = Entity::Create(ecs.get());
     entityPlayer.AddComponent<PlayerC>(entityCamera);
+    entityPlayer.AddComponent<HealthC>(10, 10);
     entityPlayer.AddComponent<PhysicsC>(0.1f, glm::vec2{0.0f, 0.0f}, glm::vec2{0.0f, 0.0f});
     entityPlayer.AddComponent<TransformC>(glm::vec2{0.0f}, glm::vec2{1.0f});
     entityPlayer.AddComponent<TextureC>(AssetRef{AssetManager::LoadAsset("fox2.meta")}, glm::vec2{0.0f, 0.0f}, glm::vec2{1.0f, 1.0f});

CopiumEngine/src/copium/core/SwapChain.cpp

@@ -4,6 +4,8 @@
 #include "copium/core/Vulkan.h"
 #include "copium/sampler/Image.h"
 
+#include <GLFW/glfw3.h>
+
 namespace Copium
 {
   SwapChainSupportDetails::SwapChainSupportDetails(VkSurfaceKHR surface, VkPhysicalDevice physicalDevice)

CopiumEngine/src/copium/core/Window.cpp

@@ -12,6 +12,8 @@
 #include "copium/event/WindowResizeEvent.h"
 #include "copium/event/WindowFocusEvent.h"
 
+#include <GLFW/glfw3.h>
+
 namespace Copium
 {
   Window::Window(const std::string& windowName, int width, int height, WindowMode mode)
@@ -27,6 +29,22 @@ namespace Copium
     glfwDestroyWindow(window);
   }
 
+  bool Window::ShouldClose() const
+  {
+    return glfwWindowShouldClose(window);
+
+  }
+
+  int Window::GetWidth() const
+  {
+    return width;
+  }
+
+  int Window::GetHeight() const
+  {
+    return height;
+  }
+
   VkSurfaceKHR Window::GetSurface() const
   {
     return surface;

CopiumEngine/src/copium/core/Window.h

@@ -3,11 +3,17 @@
 #include "copium/util/Common.h"
 #include "copium/util/Enum.h"
 
-#include <GLFW/glfw3.h>
+#include <vulkan/vulkan.hpp>
+
+#define CP_WINDOW_MODE_ENUMS \
+        Fullscreen, \
+        BorderlessWindowed, \
+        Windowed
 
-#define CP_WINDOW_MODE_ENUMS Fullscreen, BorderlessWindowed, Windowed
 CP_ENUM_CREATOR(Copium, WindowMode, CP_WINDOW_MODE_ENUMS);
 
+struct GLFWwindow;
+
 namespace Copium
 {
   class Window final
@@ -24,6 +30,10 @@ namespace Copium
     Window(const std::string& windowName, int width, int height, WindowMode mode);
     ~Window();
 
+    bool ShouldClose() const;
+
+    int GetWidth() const;
+    int GetHeight() const;
     VkSurfaceKHR GetSurface() const;
     GLFWwindow* GetWindow();
 

CopiumEngine/src/copium/ecs/ComponentListener.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "copium/ecs/ECSManager.h"
+
+namespace Copium
+{
+  template <typename Component>
+  class ComponentListener
+  {
+  public:
+    using component_type = Component;
+    friend class ECSManager;
+  protected:
+    ECSManager* manager;
+  public:
+    virtual void Added(EntityId entityId, Component& component) {}
+    virtual void Removed(EntityId entityId, Component& component) {}
+  };
+}

CopiumEngine/src/copium/ecs/ComponentPool.h

@@ -3,6 +3,7 @@
 #include "copium/ecs/Config.h"
 #include "copium/ecs/EntitySet.h"
 #include "copium/ecs/ComponentPoolBase.h"
+#include "copium/ecs/ComponentListener.h"
 
 #include <vector>
 
@@ -14,8 +15,18 @@ namespace Copium
     using Iterator = typename std::vector<Component>::iterator;
   private:
     std::vector<Component> components;
+    ComponentListener<Component>* listener = nullptr;
 
   public:
+    ComponentPool()
+    {}
+
+    ~ComponentPool() override
+    {
+      if(listener)
+        delete listener;
+    }
+
     ComponentPool(EntityId entity, const Component& component)
     {
       Emplace(entity, component);
@@ -25,21 +36,27 @@ namespace Copium
     {
       components.push_back(component);
       entities.Emplace(entity);
+      if(listener)
+        listener->Added(entity, components.back());
       return components.back();
     }
 
-    void Pop()
+    bool Erase(EntityId entity) override
-    {
-      components.pop_back();
-      entities.Pop();
-    }
-
-    bool Erase(EntityId entity)
     {
       size_t index = entities.Find(entity);
       if (!entities.Erase(entity))
         return false;
+      if (listener)
+      {
+        auto it = components.begin() + index;
+        Component component = *it;
+        components.erase(it);
+        listener->Removed(entity, component);
+      }
+      else
+      {
         components.erase(components.begin() + index);
+      }
       return true;
     }
 
@@ -61,13 +78,18 @@ namespace Copium
       return nullptr;
     }
 
+    void SetComponentListener(ComponentListener<Component>* listener)
+    {
+      ComponentPool::listener = listener;
+    }
+
     Component& operator[](size_t index)
     {
       CP_ASSERT(index < components.size(), "Index Out of Bound Exception");
       return components[index];
     }
 
-    size_t Size()
+    size_t Size() override
     {
       return components.size();
     }

CopiumEngine/src/copium/ecs/ComponentPoolBase.h

@@ -15,7 +15,6 @@ namespace Copium
     virtual ~ComponentPoolBase() = default;
 
     virtual size_t Size() = 0;
-    virtual void Pop() = 0;
     virtual bool Erase(EntityId entity) = 0;
     std::vector<EntityId>& GetEntities();
     const std::vector<EntityId>& GetEntities() const;

CopiumEngine/src/copium/ecs/ECSManager.h

@@ -48,6 +48,25 @@ namespace Copium
     bool ValidEntity(EntityId entity);
     void Each(std::function<void(EntityId)> function);
 
+    template <typename Listener, typename... Args>
+    void SetComponentListener(const Args&... args)
+    {
+      using Component = typename Listener::component_type;
+      auto pool = GetComponentPool<Component>();
+      Listener* listener = new Listener{args...};
+      listener->manager = this;
+      if (pool)
+      {
+        pool->SetComponentListener(listener);
+      }
+      else
+      {
+        ComponentPool<Component>* pool{new ComponentPool<Component>{}};
+        componentPool.emplace(GetComponentId<Component>(), pool);
+        pool->SetComponentListener(listener);
+      }
+    }
+
     template <typename... Components>
     std::tuple<Components&...> AddComponents(EntityId entity, Components&&... components)
     {

CopiumEngine/src/copium/event/Input.cpp

@@ -1,6 +1,9 @@
 #include "copium/event/Input.h"
 
 #include "copium/util/Common.h"
+#include "copium/core/Vulkan.h"
+
+#include <glm/gtc/matrix_transform.hpp>
 
 namespace Copium
 {
@@ -63,6 +66,11 @@ namespace Copium
     return mousePos;
   }
 
+  glm::vec2 Input::GetMouseWindowPos()
+  {
+    return glm::vec2{(mousePos.x + 1.0f) * 0.5f * Vulkan::GetWindow().GetWidth(), (1.0f - mousePos.y) * 0.5f * Vulkan::GetWindow().GetHeight()};
+  }
+
   void Input::OnKey(int keyCode, bool pressed)
   {
     CP_ASSERT(keyCode >= 0 && keyCode < MAX_NUM_KEYS, "KeyCode is out of range");
@@ -85,5 +93,6 @@ namespace Copium
   void Input::Update()
   {
     memset(keyEventList, false, sizeof(keyEventList));
+    memset(mouseEventList, false, sizeof(mouseEventList));
   }
 }

CopiumEngine/src/copium/event/Input.h

@@ -35,6 +35,7 @@ namespace Copium
     static bool IsMouseDown(int button);
     static bool IsMouseUp(int button);
 
+    static glm::vec2 GetMouseWindowPos();
     static glm::vec2 GetMousePos();
 
     static void OnKey(int keyCode, bool pressed);

CopiumEngine/src/copium/example/Components.h

@@ -57,4 +57,13 @@ namespace Copium
   {
     Entity camera;
   };
+
+  struct HealthC
+  {
+    int current;
+    int max;
+
+    Entity background;
+    Entity foreground;
+  };
 }

CopiumEngine/src/copium/example/HealthChangeSystem.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include "copium/ecs/System.h"
+#include "copium/example/Components.h"
+#include "copium/event/Input.h"
+
+namespace Copium
+{
+  class HealthChangeSystem : public System<HealthC>
+  {
+
+    void RunEntity(Entity entity, HealthC& health) override
+    {
+      if (Input::IsKeyPressed(CP_KEY_K))
+        health.current++;
+      if (Input::IsKeyPressed(CP_KEY_J))
+        health.current--;
+      health.current = std::clamp(health.current, 0, health.max);
+    }
+  };
+}

CopiumEngine/src/copium/example/HealthComponentListener.h

@@ -0,0 +1,35 @@
+#pragma once
+
+#include "copium/ecs/ComponentListener.h"
+#include "copium/example/Components.h"
+#include "copium/util/Common.h"
+
+namespace Copium
+{
+  class HealthComponentListener : public ComponentListener<HealthC>
+  {
+    void Added(EntityId entityId, HealthC& health) override
+    {
+      CP_ASSERT(!health.background, "Health already has background entity assigned");
+      CP_ASSERT(!health.foreground, "Health already has foreground entity assigned");
+
+      health.background = Entity::Create(manager);
+      health.background.AddComponent<TransformC>(glm::vec2{0.0f, 0.0f}, glm::vec2{1.0f, 0.2f});
+      health.background.AddComponent<ColorC>(glm::vec3{0.9f, 0.2f, 0.2f});
+
+      health.foreground = Entity::Create(manager);
+      health.foreground.AddComponent<TransformC>(glm::vec2{0.0f, 0.0f}, glm::vec2{std::clamp(health.current, 0, health.max) / (float)health.max, 0.2f});
+      health.foreground.AddComponent<ColorC>(glm::vec3{0.2f, 0.9f, 0.2f});
+    }
+
+    void Removed(EntityId entityId, HealthC& health) override
+    {
+      CP_ASSERT(health.background, "Health already removed background entity");
+      CP_ASSERT(health.foreground, "Health already removed foreground entity");
+
+      health.background.Destroy();
+      health.foreground.Destroy();
+    }
+  };
+
+}

CopiumEngine/src/copium/example/HealthDisplaySystem.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include "copium/ecs/System.h"
+#include "copium/example/Components.h"
+
+
+namespace Copium
+{
+  class HealthDisplaySystem : public System<HealthC, TransformC>
+  {
+    void RunEntity(Entity entity, HealthC& health, TransformC& transform) override
+    {
+      TransformC& foregroundTransform = health.foreground.GetComponent<TransformC>();
+      foregroundTransform.position = transform.position + glm::vec2{0.0f, transform.size.y * 1.13};
+      foregroundTransform.size = glm::vec2{std::clamp(health.current, 0, health.max) / (float)health.max, 0.2f};
+
+      TransformC& backgroundTransform = health.background.GetComponent<TransformC>();
+      backgroundTransform.position = transform.position + glm::vec2{0.0f, transform.size.y * 1.13};
+    }
+  };
+
+}

CopiumEngine/src/copium/example/PlayerControllerSystem.h

@@ -18,8 +18,19 @@ namespace Copium
       if (Input::IsKeyDown(CP_KEY_A)) force.x -= 1.0f;
       if (Input::IsKeyDown(CP_KEY_D)) force.x += 1.0f;
 
-      glm::normalize(force);
+      if (force.x != 0 || force.y != 0)
+      {
+        force = glm::normalize(force);
         physics.force += force * magnitude;
       }
+
+      if (Input::IsKeyPressed(CP_KEY_H))
+      {
+        if (entity.HasComponent<HealthC>())
+          entity.RemoveComponent<HealthC>();
+        else
+          entity.AddComponent<HealthC>(8, 10);
+      }
+    }
   };
 }

CopiumEngine/src/copium/main.cpp

@@ -16,10 +16,9 @@ int main(int argc, char** argv)
     Copium::Application application;
     while (application.Update())
     {
-      glfwPollEvents();
-
-      Copium::EventDispatcher::Dispatch();
       Copium::Input::Update();
+      glfwPollEvents();
+      Copium::EventDispatcher::Dispatch();
     }
   }
   Copium::Vulkan::Destroy();

CopiumEngine/src/copium/util/RefCounter.cpp

@@ -0,0 +1,72 @@
+#include "copium/util/RefCounter.h"
+
+#include "copium/util/Common.h"
+
+namespace Copium
+{
+  RefCounter::RefCounter()
+    : refCounter{new int{1}}
+  {}
+
+  RefCounter::~RefCounter()
+  {
+    if (Valid())
+    {
+      (*refCounter)--;
+      if (*refCounter == 0)
+      {
+        delete refCounter;
+        refCounter = nullptr;
+      }
+    }
+  }
+
+  RefCounter::RefCounter(RefCounter&& rhs)
+    : refCounter(rhs.refCounter)
+  {
+    CP_ASSERT(Valid(), "RefCounter : Moving a deleted RefCounter");
+    rhs.refCounter = nullptr;
+  }
+
+  RefCounter::RefCounter(const RefCounter& rhs)
+    : refCounter{rhs.refCounter}
+  {
+    CP_ASSERT(Valid(), "RefCounter : Copying a deleted RefCounter");
+    (*refCounter)++;
+  }
+
+  RefCounter& RefCounter::operator=(RefCounter&& rhs)
+  {
+    CP_ASSERT(Valid(), "operator= : Moving a deleted RefCounter");
+
+    refCounter = rhs.refCounter;
+    rhs.refCounter = nullptr;
+    return *this;
+  }
+
+  RefCounter& RefCounter::operator=(const RefCounter& rhs)
+  {
+    CP_ASSERT(Valid(), "operator= : Copying a deleted RefCounter");
+
+    refCounter = rhs.refCounter;
+    (*refCounter)++;
+    return *this;
+  }
+
+  bool RefCounter::Valid() const
+  {
+    return refCounter != nullptr;
+  }
+
+  bool RefCounter::LastRef() const
+  {
+    return Valid() && *refCounter == 1;
+  }
+
+  int RefCounter::Counter() const
+  {
+    CP_ASSERT(Valid(), "Counter : referencing a deleted RefCounter");
+
+    return *refCounter;
+  }
+}

CopiumEngine/src/copium/util/RefCounter.h

@@ -0,0 +1,24 @@
+#pragma once
+
+namespace Copium
+{
+  class RefCounter final
+  {
+  private:
+    int* refCounter;
+
+  public:
+    RefCounter();
+    ~RefCounter();
+
+    RefCounter(RefCounter&& rhs);
+    RefCounter(const RefCounter& rhs);
+
+    RefCounter& operator=(RefCounter&& rhs);
+    RefCounter& operator=(const RefCounter& rhs);
+
+    bool Valid() const;
+    bool LastRef() const;
+    int Counter() const;
+  };
+}