The Tor Browser: ipc/chromium/src/base/waitable_event

ipc/chromium/src/base/waitable_event_watcher.h@6474c204b198 (annotated)

ipc/chromium/src/base/waitable_event_watcher.h

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 #ifndef BASE_WAITABLE_EVENT_WATCHER_H_
 #define BASE_WAITABLE_EVENT_WATCHER_H_
 #include "build/build_config.h"
 #if defined(OS_WIN)
 #include "base/object_watcher.h"
 #else
 #include "base/message_loop.h"
 #include "base/waitable_event.h"
 #endif
 namespace base {
 class Flag;
 class AsyncWaiter;
 class AsyncCallbackTask;
 class WaitableEvent;
 // -----------------------------------------------------------------------------
 // This class provides a way to wait on a WaitableEvent asynchronously.
 //
 // Each instance of this object can be waiting on a single WaitableEvent. When
 // the waitable event is signaled, a callback is made in the thread of a given
 // MessageLoop. This callback can be deleted by deleting the waiter.
 //
 // Typical usage:
 //
 //   class MyClass : public base::WaitableEventWatcher::Delegate {
 //    public:
 //     void DoStuffWhenSignaled(WaitableEvent *waitable_event) {
 //       watcher_.StartWatching(waitable_event, this);
 //     }
 //     virtual void OnWaitableEventSignaled(WaitableEvent* waitable_event) {
 //       // OK, time to do stuff!
 //     }
 //    private:
 //     base::WaitableEventWatcher watcher_;
 //   };
 //
 // In the above example, MyClass wants to "do stuff" when waitable_event
 // becomes signaled. WaitableEventWatcher makes this task easy. When MyClass
 // goes out of scope, the watcher_ will be destroyed, and there is no need to
 // worry about OnWaitableEventSignaled being called on a deleted MyClass
 // pointer.
 //
 // BEWARE: With automatically reset WaitableEvents, a signal may be lost if it
 // occurs just before a WaitableEventWatcher is deleted. There is currently no
 // safe way to stop watching an automatic reset WaitableEvent without possibly
 // missing a signal.
 //
 // NOTE: you /are/ allowed to delete the WaitableEvent while still waiting on
 // it with a Watcher. It will act as if the event was never signaled.
 // -----------------------------------------------------------------------------
 class WaitableEventWatcher
 #if defined(OS_POSIX)
     : public MessageLoop::DestructionObserver
 #endif
 {
  public:
   WaitableEventWatcher();
   ~WaitableEventWatcher();
   class Delegate {
    public:
     virtual ~Delegate() { }
     // -------------------------------------------------------------------------
     // This is called on the MessageLoop thread when WaitableEvent has been
     // signaled.
     //
     // Note: the event may not be signaled by the time that this function is
     // called. This indicates only that it has been signaled at some point in
     // the past.
     // -------------------------------------------------------------------------
     virtual void OnWaitableEventSignaled(WaitableEvent* waitable_event) = 0;
   };
   // ---------------------------------------------------------------------------
   // When @event is signaled, the given delegate is called on the thread of the
   // current message loop when StartWatching is called. The delegate is not
   // deleted.
   // ---------------------------------------------------------------------------
   bool StartWatching(WaitableEvent* event, Delegate* delegate);
   // ---------------------------------------------------------------------------
   // Cancel the current watch. Must be called from the same thread which
   // started the watch.
   //
   // Does nothing if no event is being watched, nor if the watch has completed.
   // The delegate will *not* be called for the current watch after this
   // function returns. Since the delegate runs on the same thread as this
   // function, it cannot be called during this function either.
   // ---------------------------------------------------------------------------
   void StopWatching();
   // ---------------------------------------------------------------------------
   // Return the currently watched event, or NULL if no object is currently being
   // watched.
   // ---------------------------------------------------------------------------
   WaitableEvent* GetWatchedEvent();
  private:
   WaitableEvent* event_;
 #if defined(OS_WIN)
   // ---------------------------------------------------------------------------
   // The helper class exists because, if WaitableEventWatcher were to inherit
   // from ObjectWatcher::Delegate, then it couldn't also have an inner class
   // called Delegate (at least on Windows). Thus this object exists to proxy
   // the callback function
   // ---------------------------------------------------------------------------
   class ObjectWatcherHelper : public ObjectWatcher::Delegate {
    public:
     ObjectWatcherHelper(WaitableEventWatcher* watcher);
     // -------------------------------------------------------------------------
     // Implementation of ObjectWatcher::Delegate
     // -------------------------------------------------------------------------
     void OnObjectSignaled(HANDLE h);
    private:
     WaitableEventWatcher *const watcher_;
   };
   void OnObjectSignaled();
   Delegate* delegate_;
   ObjectWatcherHelper helper_;
   ObjectWatcher watcher_;
 #else
   // ---------------------------------------------------------------------------
   // Implementation of MessageLoop::DestructionObserver
   // ---------------------------------------------------------------------------
   void WillDestroyCurrentMessageLoop();
   MessageLoop* message_loop_;
   scoped_refptr<Flag> cancel_flag_;
   AsyncWaiter* waiter_;
   AsyncCallbackTask* callback_task_;
   scoped_refptr<WaitableEvent::WaitableEventKernel> kernel_;
 #endif
 };
 }  // namespace base
 #endif  // BASE_WAITABLE_EVENT_WATCHER_H_

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ipc/chromium/src/base/waitable_event_watcher.h@6474c204b198 (annotated)

ipc/chromium/src/base/waitable_event_watcher.h