base/memory/ref_counted_delete_on_message_loop.h

   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 #ifndef BASE_MEMORY_REF_COUNTED_DELETE_ON_MESSAGE_LOOP_H_
   6 #define BASE_MEMORY_REF_COUNTED_DELETE_ON_MESSAGE_LOOP_H_
   7
   8 #include "base/location.h"
   9 #include "base/logging.h"
  10 #include "base/memory/ref_counted.h"
  11 // TODO(ricea): Remove the following include once all callers have been fixed.
  12 #include "base/message_loop/message_loop_proxy.h"
  13 #include "base/single_thread_task_runner.h"
  14
  15 namespace base {
  16
  17 // RefCountedDeleteOnMessageLoop is similar to RefCountedThreadSafe, and ensures
  18 // that the object will be deleted on a specified message loop.
  19 //
  20 // Sample usage:
  21 // class Foo : public RefCountedDeleteOnMessageLoop<Foo> {
  22 //
  23 //   Foo(const scoped_refptr<SingleThreadTaskRunner>& loop)
  24 //       : RefCountedDeleteOnMessageLoop<Foo>(loop) {
  25 //     ...
  26 //   }
  27 //   ...
  28 //  private:
  29 //   friend class RefCountedDeleteOnMessageLoop<Foo>;
  30 //   friend class DeleteHelper<Foo>;
  31 //
  32 //   ~Foo();
  33 // };
  34
  35 // TODO(skyostil): Rename this to RefCountedDeleteOnTaskRunner.
  36 template <class T>
  37 class RefCountedDeleteOnMessageLoop : public subtle::RefCountedThreadSafeBase {
  38  public:
  39   // This constructor will accept a MessageL00pProxy object, but new code should
  40   // prefer a SingleThreadTaskRunner. A SingleThreadTaskRunner for the
  41   // MessageLoop on the current thread can be acquired by calling
  42   // MessageLoop::current()->task_runner().
  43   RefCountedDeleteOnMessageLoop(
  44       const scoped_refptr<SingleThreadTaskRunner>& task_runner)
  45       : task_runner_(task_runner) {
  46     DCHECK(task_runner_);
  47   }
  48
  49   void AddRef() const {
  50     subtle::RefCountedThreadSafeBase::AddRef();
  51   }
  52
  53   void Release() const {
  54     if (subtle::RefCountedThreadSafeBase::Release())
  55       DestructOnMessageLoop();
  56   }
  57
  58  protected:
  59   friend class DeleteHelper<RefCountedDeleteOnMessageLoop>;
  60   ~RefCountedDeleteOnMessageLoop() {}
  61
  62   void DestructOnMessageLoop() const {
  63     const T* t = static_cast<const T*>(this);
  64     if (task_runner_->BelongsToCurrentThread())
  65       delete t;
  66     else
  67       task_runner_->DeleteSoon(FROM_HERE, t);
  68   }
  69
  70   scoped_refptr<SingleThreadTaskRunner> task_runner_;
  71
  72  private:
  73   DISALLOW_COPY_AND_ASSIGN(RefCountedDeleteOnMessageLoop);
  74 };
  75
  76 }  // namespace base
  77
  78 #endif  // BASE_MEMORY_REF_COUNTED_DELETE_ON_MESSAGE_LOOP_H_