third_party/WebKit/Source/wtf/ThreadRestrictionVerifier.h

   1 /*
   2  * Copyright (C) 2011 Google Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  *     * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *     * Redistributions in binary form must reproduce the above
  11  * copyright notice, this list of conditions and the following disclaimer
  12  * in the documentation and/or other materials provided with the
  13  * distribution.
  14  *     * Neither the name of Google Inc. nor the names of its
  15  * contributors may be used to endorse or promote products derived from
  16  * this software without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #ifndef ThreadRestrictionVerifier_h
  32 #define ThreadRestrictionVerifier_h
  33
  34 #include "wtf/Assertions.h"
  35
  36 #if ENABLE(ASSERT)
  37
  38 #include "wtf/Threading.h"
  39
  40 namespace WTF {
  41
  42 // Verifies that a class is used in a way that respects its lack of thread-safety.
  43 // The default mode is to verify that the object will only be used on a single thread. The
  44 // thread gets captured when setShared(true) is called.
  45 // The mode may be changed by calling useMutexMode (or turnOffVerification).
  46 class ThreadRestrictionVerifier {
  47 public:
  48     ThreadRestrictionVerifier()
  49         : m_shared(false)
  50         , m_owningThread(0)
  51     {
  52     }
  53
  54     // Indicates that the object may (or may not) be owned by more than one place.
  55     void setShared(bool shared)
  56     {
  57         bool previouslyShared = m_shared;
  58         m_shared = shared;
  59
  60         if (!m_shared)
  61             return;
  62
  63         ASSERT_UNUSED(previouslyShared, shared != previouslyShared);
  64         // Capture the current thread to verify that subsequent ref/deref happen on this thread.
  65         m_owningThread = currentThread();
  66     }
  67
  68     // Is it OK to use the object at this moment on the current thread?
  69     bool isSafeToUse() const
  70     {
  71         if (!m_shared)
  72             return true;
  73
  74         return m_owningThread == currentThread();
  75     }
  76
  77 private:
  78     bool m_shared;
  79
  80     // Used by SingleThreadVerificationMode
  81     ThreadIdentifier m_owningThread;
  82 };
  83
  84 }
  85
  86 #endif // ENABLE(ASSERT)
  87 #endif // ThreadRestrictionVerifier_h