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

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+:1a53ebe1ddaf
+// 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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comparison: ipc/chromium/src/base/waitable_event_watcher.h

ipc/chromium/src/base/waitable_event_watcher.h