Home | History | Annotate | Download | only in base 
      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_PROXY_H_
      6 #define BASE_MESSAGE_LOOP_PROXY_H_
      7 #pragma once
      8 
      9 #include "base/base_api.h"
     10 #include "base/basictypes.h"
     11 #include "base/memory/ref_counted.h"
     12 #include "base/task.h"
     13 
     14 namespace base {
     15 
     16 struct MessageLoopProxyTraits;
     17 
     18 // This class provides a thread-safe refcounted interface to the Post* methods
     19 // of a message loop. This class can outlive the target message loop. You can
     20 // obtain a MessageLoopProxy via Thread::message_loop_proxy() or
     21 // MessageLoopProxy::CreateForCurrentThread().
     22 class BASE_API MessageLoopProxy
     23     : public base::RefCountedThreadSafe<MessageLoopProxy,
     24                                         MessageLoopProxyTraits> {
     25  public:
     26   // These methods are the same as in message_loop.h, but are guaranteed to
     27   // either post the Task to the MessageLoop (if it's still alive), or to
     28   // delete the Task otherwise.
     29   // They return true iff the thread existed and the task was posted.  Note that
     30   // even if the task is posted, there's no guarantee that it will run; for
     31   // example the target loop may already be quitting, or in the case of a
     32   // delayed task a Quit message may preempt it in the message loop queue.
     33   // Conversely, a return value of false is a guarantee the task will not run.
     34   virtual bool PostTask(const tracked_objects::Location& from_here,
     35                         Task* task) = 0;
     36   virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
     37                                Task* task, int64 delay_ms) = 0;
     38   virtual bool PostNonNestableTask(const tracked_objects::Location& from_here,
     39                                    Task* task) = 0;
     40   virtual bool PostNonNestableDelayedTask(
     41       const tracked_objects::Location& from_here,
     42       Task* task,
     43       int64 delay_ms) = 0;
     44   // A method which checks if the caller is currently running in the thread that
     45   // this proxy represents.
     46   virtual bool BelongsToCurrentThread() = 0;
     47 
     48   template <class T>
     49   bool DeleteSoon(const tracked_objects::Location& from_here,
     50                   T* object) {
     51     return PostNonNestableTask(from_here, new DeleteTask<T>(object));
     52   }
     53   template <class T>
     54   bool ReleaseSoon(const tracked_objects::Location& from_here,
     55                    T* object) {
     56     return PostNonNestableTask(from_here, new ReleaseTask<T>(object));
     57   }
     58 
     59   // Factory method for creating an implementation of MessageLoopProxy
     60   // for the current thread.
     61   static scoped_refptr<MessageLoopProxy> CreateForCurrentThread();
     62 
     63  protected:
     64   friend class RefCountedThreadSafe<MessageLoopProxy, MessageLoopProxyTraits>;
     65   friend struct MessageLoopProxyTraits;
     66 
     67   MessageLoopProxy();
     68   virtual ~MessageLoopProxy();
     69 
     70   // Called when the proxy is about to be deleted. Subclasses can override this
     71   // to provide deletion on specific threads.
     72   virtual void OnDestruct() const;
     73 };
     74 
     75 struct MessageLoopProxyTraits {
     76   static void Destruct(const MessageLoopProxy* proxy) {
     77     proxy->OnDestruct();
     78   }
     79 };
     80 
     81 }  // namespace base
     82 
     83 #endif  // BASE_MESSAGE_LOOP_PROXY_H_
     84