Source/wtf/ThreadRestrictionVerifier.h

/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef ThreadRestrictionVerifier_h
#define ThreadRestrictionVerifier_h

#ifndef NDEBUG

#include "wtf/Assertions.h"
#include "wtf/Threading.h"

namespace WTF {

// Verifies that a class is used in a way that respects its lack of thread-safety.
// The default mode is to verify that the object will only be used on a single thread. The
// thread gets captured when setShared(true) is called.
// The mode may be changed by calling useMutexMode (or turnOffVerification).
class ThreadRestrictionVerifier {
public:
    ThreadRestrictionVerifier()
        : m_shared(false)
        , m_owningThread(0)
    {
    }

    // Indicates that the object may (or may not) be owned by more than one place.
    void setShared(bool shared)
    {
#if !ASSERT_DISABLED
        bool previouslyShared = m_shared;
#endif
        m_shared = shared;

        if (!m_shared)
            return;

        ASSERT(shared != previouslyShared);
        // Capture the current thread to verify that subsequent ref/deref happen on this thread.
        m_owningThread = currentThread();
    }

    // Is it OK to use the object at this moment on the current thread?
    bool isSafeToUse() const
    {
        if (!m_shared)
            return true;

        return m_owningThread == currentThread();
    }

private:
    bool m_shared;

    // Used by SingleThreadVerificationMode
    ThreadIdentifier m_owningThread;
};

}

#endif // !NDEBUG
#endif // ThreadRestrictionVerifier_h