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