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      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 #ifndef NDEBUG
     35 
     36 #include "wtf/Assertions.h"
     37 #include "wtf/Threading.h"
     38 
     39 namespace WTF {
     40 
     41 // Verifies that a class is used in a way that respects its lack of thread-safety.
     42 // The default mode is to verify that the object will only be used on a single thread. The
     43 // thread gets captured when setShared(true) is called.
     44 // The mode may be changed by calling useMutexMode (or turnOffVerification).
     45 class ThreadRestrictionVerifier {
     46 public:
     47     ThreadRestrictionVerifier()
     48         : m_shared(false)
     49         , m_owningThread(0)
     50     {
     51     }
     52 
     53     // Indicates that the object may (or may not) be owned by more than one place.
     54     void setShared(bool shared)
     55     {
     56 #if !ASSERT_DISABLED
     57         bool previouslyShared = m_shared;
     58 #endif
     59         m_shared = shared;
     60 
     61         if (!m_shared)
     62             return;
     63 
     64         ASSERT(shared != previouslyShared);
     65         // Capture the current thread to verify that subsequent ref/deref happen on this thread.
     66         m_owningThread = currentThread();
     67     }
     68 
     69     // Is it OK to use the object at this moment on the current thread?
     70     bool isSafeToUse() const
     71     {
     72         if (!m_shared)
     73             return true;
     74 
     75         return m_owningThread == currentThread();
     76     }
     77 
     78 private:
     79     bool m_shared;
     80 
     81     // Used by SingleThreadVerificationMode
     82     ThreadIdentifier m_owningThread;
     83 };
     84 
     85 }
     86 
     87 #endif // !NDEBUG
     88 #endif // ThreadRestrictionVerifier_h
     89