sequenced_task_runner_helpers.h (1633B)
1 // Copyright 2012 The Chromium Authors 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_TASK_SEQUENCED_TASK_RUNNER_HELPERS_H_ 6 #define BASE_TASK_SEQUENCED_TASK_RUNNER_HELPERS_H_ 7 8 #include <memory> 9 10 namespace base { 11 12 class SequencedTaskRunner; 13 14 // Template helpers which use function indirection to erase T from the 15 // function signature while still remembering it so we can call the 16 // correct destructor/release function. 17 // 18 // We use this trick so we don't need to include bind.h in a header 19 // file like sequenced_task_runner.h. We also wrap the helpers in a 20 // templated class to make it easier for users of DeleteSoon to 21 // declare the helper as a friend. 22 template <class T> 23 class DeleteHelper { 24 private: 25 static void DoDelete(const void* object) { 26 delete static_cast<const T*>(object); 27 } 28 29 friend class SequencedTaskRunner; 30 }; 31 32 template <class T> 33 class DeleteUniquePtrHelper { 34 private: 35 static void DoDelete(const void* object) { 36 // Carefully unwrap `object`. T could have originally been const-qualified 37 // or not, and it is important to ensure that the constness matches in order 38 // to use the right specialization of std::default_delete<T>... 39 std::unique_ptr<T> destroyer(const_cast<T*>(static_cast<const T*>(object))); 40 } 41 42 friend class SequencedTaskRunner; 43 }; 44 45 template <class T> 46 class ReleaseHelper { 47 private: 48 static void DoRelease(const void* object) { 49 static_cast<const T*>(object)->Release(); 50 } 51 52 friend class SequencedTaskRunner; 53 }; 54 55 } // namespace base 56 57 #endif // BASE_TASK_SEQUENCED_TASK_RUNNER_HELPERS_H_