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 <wtf/ThreadingPrimitives.h>
   9
  10 namespace WebCore {
  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     {
  20 #ifndef NDEBUG
  21         m_waited = false;
  22         m_signaled = false;
  23 #endif
  24         m_mutex.lock();
  25     }
  26
  27     ~CCCompletionEvent()
  28     {
  29         m_mutex.unlock();
  30         ASSERT(m_waited);
  31         ASSERT(m_signaled);
  32     }
  33
  34     void wait()
  35     {
  36         ASSERT(!m_waited);
  37 #ifndef NDEBUG
  38         m_waited = true;
  39 #endif
  40         m_condition.wait(m_mutex);
  41     }
  42
  43     void signal()
  44     {
  45         MutexLocker lock(m_mutex);
  46         ASSERT(!m_signaled);
  47 #ifndef NDEBUG
  48         m_signaled = true;
  49 #endif
  50         m_condition.signal();
  51     }
  52
  53 private:
  54     Mutex m_mutex;
  55     ThreadCondition m_condition;
  56 #ifndef NDEBUG
  57     // Used to assert that wait() and signal() are each called exactly once.
  58     bool m_waited;
  59     bool m_signaled;
  60 #endif
  61 };
  62
  63 }
  64
  65 #endif