cc/CCCompletionEvent.h

   1 // Copyright 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 CCCompletionEvent_h
   6 #define CCCompletionEvent_h
   7
   8 #include "base/synchronization/waitable_event.h"
   9
  10 namespace cc {
  11
  12 // Used for making blocking calls from one thread to another. Use only when
  13 // absolutely certain that doing-so will not lead to a deadlock.
  14 //
  15 // It is safe to destroy this object as soon as wait() returns.
  16 class CCCompletionEvent {
  17 public:
  18     CCCompletionEvent()
  19         : m_event(false /* manual_reset */, false /* initially_signaled */)
  20     {
  21 #ifndef NDEBUG
  22         m_waited = false;
  23         m_signaled = false;
  24 #endif
  25     }
  26
  27     ~CCCompletionEvent()
  28     {
  29         ASSERT(m_waited);
  30         ASSERT(m_signaled);
  31     }
  32
  33     void wait()
  34     {
  35         ASSERT(!m_waited);
  36 #ifndef NDEBUG
  37         m_waited = true;
  38 #endif
  39         m_event.Wait();
  40     }
  41
  42     void signal()
  43     {
  44         ASSERT(!m_signaled);
  45 #ifndef NDEBUG
  46         m_signaled = true;
  47 #endif
  48         m_event.Signal();
  49     }
  50
  51 private:
  52     base::WaitableEvent m_event;
  53 #ifndef NDEBUG
  54     // Used to assert that wait() and signal() are each called exactly once.
  55     bool m_waited;
  56     bool m_signaled;
  57 #endif
  58 };
  59
  60 }
  61
  62 #endif