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1 // Copyright 2013 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 // Helper class used to find the RenderFrameObservers for a given RenderFrame.
6 //
7 // Example usage:
8 //
9 //   class MyRFO : public RenderFrameObserver,
10 //                 public RenderFrameObserverTracker<MyRFO> {
11 //     ...
12 //   };
13 //
14 //   MyRFO::MyRFO(RenderFrame* render_frame)
15 //       : RenderFrameObserver(render_frame),
16 //         RenderFrameObserverTracker<MyRFO>(render_frame) {
17 //     ...
18 //   }
19 //
20 //  void SomeFunction(RenderFrame* rf) {
21 //    MyRFO* my_rfo = new MyRFO(rf);
22 //    MyRFO* my_rfo_tracked = MyRFO::Get(rf);
23 //    // my_rfo == my_rfo_tracked
24 //  }
25 
26 #ifndef CONTENT_PUBLIC_RENDERER_RENDER_FRAME_OBSERVER_TRACKER_H_
27 #define CONTENT_PUBLIC_RENDERER_RENDER_FRAME_OBSERVER_TRACKER_H_
28 
29 #include <map>
30 
31 #include "base/lazy_instance.h"
32 
33 namespace content {
34 
35 class RenderFrame;
36 
37 template <class T>
38 class RenderFrameObserverTracker {
39  public:
Get(const RenderFrame * render_frame)40   static T* Get(const RenderFrame* render_frame) {
41     return render_frame_map_.Get()[render_frame];
42   }
43 
RenderFrameObserverTracker(const RenderFrame * render_frame)44   explicit RenderFrameObserverTracker(const RenderFrame* render_frame)
45       : render_frame_(render_frame) {
46     render_frame_map_.Get()[render_frame] = static_cast<T*>(this);
47   }
~RenderFrameObserverTracker()48   ~RenderFrameObserverTracker() {
49     render_frame_map_.Get().erase(render_frame_);
50   }
51 
52  private:
53   const RenderFrame* render_frame_;
54 
55   static base::LazyInstance<std::map<const RenderFrame*, T*> >
56     render_frame_map_;
57 
58   DISALLOW_COPY_AND_ASSIGN(RenderFrameObserverTracker<T>);
59 };
60 
61 template <class T>
62 base::LazyInstance<std::map<const RenderFrame*, T*> >
63     RenderFrameObserverTracker<T>::render_frame_map_ =
64         LAZY_INSTANCE_INITIALIZER;
65 
66 }  // namespace content
67 
68 #endif  // CONTENT_PUBLIC_RENDERER_RENDER_FRAME_OBSERVER_TRACKER_H_
69