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1 // Copyright (c) 2011 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 #ifndef BASE_MESSAGE_LOOP_HELPERS_H_ | |
6 #define BASE_MESSAGE_LOOP_HELPERS_H_ | |
7 #pragma once | |
8 | |
9 #include "base/basictypes.h" | |
10 | |
11 namespace tracked_objects { | |
12 class Location; | |
13 } | |
14 | |
15 namespace base { | |
16 | |
17 namespace subtle { | |
18 template <class T, class R> class DeleteHelperInternal; | |
19 } | |
20 | |
21 // This is a template helper which uses a function indirection to erase T from | |
22 // the function signature while still remembering it so we can call the correct | |
23 // destructor. We use this trick so we don't need to include bind.h in a | |
24 // header file. We also embed the function in a class to make it easier for | |
25 // users of DeleteSoon to declare the helper as a friend. | |
26 template <class T> | |
27 class DeleteHelper { | |
28 private: | |
29 // TODO(dcheng): Move the return type back to a function template parameter. | |
30 template <class T2, class R> friend class subtle::DeleteHelperInternal; | |
31 | |
32 static void DoDelete(const void* object) { | |
33 delete reinterpret_cast<const T*>(object); | |
34 } | |
35 | |
36 DISALLOW_COPY_AND_ASSIGN(DeleteHelper); | |
37 }; | |
38 | |
39 namespace subtle { | |
40 | |
41 // An internal MessageLoop-like class helper for DeleteHelper. We don't want to | |
42 // expose DoDelete directly since the void* argument makes it possible to pass | |
43 // an object of the wrong type to delete. Instead, we force callers to go | |
44 // through DeleteHelperInternal for type safety. MessageLoop-like classes which | |
45 // expose a DeleteSoon method should friend this class and implement a | |
46 // DeleteSoonInternal method with the following signature: | |
47 // bool(const tracked_objects::Location&, | |
48 // void(*deleter)(const void*), | |
49 // void* object) | |
50 // An implementation of DeleteSoonInternal should simply create a base::Closure | |
51 // from (deleter, object) and return the result of posting the task. | |
52 template <class T, class ReturnType> | |
53 class DeleteHelperInternal { | |
54 public: | |
55 template <class MessageLoopType> | |
56 static ReturnType DeleteOnMessageLoop( | |
57 MessageLoopType* message_loop, | |
58 const tracked_objects::Location& from_here, | |
59 const T* object) { | |
60 return message_loop->DeleteSoonInternal(from_here, | |
61 &DeleteHelper<T>::DoDelete, | |
62 object); | |
63 } | |
64 | |
65 private: | |
66 DISALLOW_COPY_AND_ASSIGN(DeleteHelperInternal); | |
67 }; | |
68 | |
69 } // namespace subtle | |
70 | |
71 } // namespace base | |
72 | |
73 #endif // BASE_MESSAGE_LOOP_HELPERS_H_ | |
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