base/message_loop_proxy.h

   1 // Copyright (c) 2010 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_PROXY_H_
   6 #define BASE_MESSAGE_LOOP_PROXY_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/ref_counted.h"
  10 #include "base/task.h"
  11
  12 namespace base {
  13
  14 struct MessageLoopProxyTraits;
  15
  16 // This class provides a thread-safe refcounted interface to the Post* methods
  17 // of a message loop. This class can outlive the target message loop.
  18 class MessageLoopProxy
  19     : public base::RefCountedThreadSafe<MessageLoopProxy,
  20                                         MessageLoopProxyTraits> {
  21  public:
  22   // These are the same methods in message_loop.h, but are guaranteed to either
  23   // get posted to the MessageLoop if it's still alive, or be deleted otherwise.
  24   // They return true iff the thread existed and the task was posted.  Note that
  25   // even if the task is posted, there's no guarantee that it will run, since
  26   // the target thread may already have a Quit message in its queue.
  27   virtual bool PostTask(const tracked_objects::Location& from_here,
  28                         Task* task) = 0;
  29   virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
  30                                Task* task, int64 delay_ms) = 0;
  31   virtual bool PostNonNestableTask(const tracked_objects::Location& from_here,
  32                                    Task* task) = 0;
  33   virtual bool PostNonNestableDelayedTask(
  34       const tracked_objects::Location& from_here,
  35       Task* task,
  36       int64 delay_ms) = 0;
  37   // A method which checks if the caller is currently running in the thread that
  38   // this proxy represents.
  39   virtual bool BelongsToCurrentThread() = 0;
  40
  41   template <class T>
  42   bool DeleteSoon(const tracked_objects::Location& from_here,
  43                   T* object) {
  44     return PostNonNestableTask(from_here, new DeleteTask<T>(object));
  45   }
  46   template <class T>
  47   bool ReleaseSoon(const tracked_objects::Location& from_here,
  48                    T* object) {
  49     return PostNonNestableTask(from_here, new ReleaseTask<T>(object));
  50   }
  51
  52   // Factory method for creating an implementation of MessageLoopProxy
  53   // for the current thread.
  54   static scoped_refptr<MessageLoopProxy> CreateForCurrentThread();
  55
  56  protected:
  57   friend struct MessageLoopProxyTraits;
  58   // Called when the proxy is about to be deleted. Subclasses can override this
  59   // to provide deletion on specific threads.
  60   virtual void OnDestruct() {
  61     delete this;
  62   }
  63 };
  64
  65 struct MessageLoopProxyTraits {
  66   static void Destruct(MessageLoopProxy* proxy) {
  67     proxy->OnDestruct();
  68   }
  69 };
  70
  71 }  // namespace base
  72
  73 #endif  // BASE_MESSAGE_LOOP_PROXY_H_
  74