WebCore/platform/win/MutexWin.cpp

/*
 * Copyright (C) 2007 Apple Inc. All rights reserved.
 * Copyright (C) 2007 Brent Fulgham
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer. 
 * 2.  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. 
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") 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 APPLE AND ITS 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 APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include "config.h"
#include "Threading.h"

namespace WebCore {

Mutex::Mutex()
{
    m_mutex.m_recursionCount = 0;
    ::InitializeCriticalSection(&m_mutex.m_internalMutex);
}

Mutex::~Mutex()
{
    ::DeleteCriticalSection(&m_mutex.m_internalMutex);
}

void Mutex::lock()
{
    ::EnterCriticalSection(&m_mutex.m_internalMutex);
    ++m_mutex.m_recursionCount;
}
    
bool Mutex::tryLock()
{
    // This method is modeled after the behavior of pthread_mutex_trylock,
    // which will return an error if the lock is already owned by the
    // current thread.  Since the primitive Win32 'TryEnterCriticalSection'
    // treats this as a successful case, it changes the behavior of several
    // tests in WebKit that check to see if the current thread already
    // owned this mutex (see e.g., IconDatabase::getOrCreateIconRecord)
    DWORD result = ::TryEnterCriticalSection(&m_mutex.m_internalMutex);
    
    if (result != 0) {       // We got the lock
        // If this thread already had the lock, we must unlock and
        // return false so that we mimic the behavior of POSIX's
        // pthread_mutex_trylock:
        if (m_mutex.m_recursionCount > 0) {
            ::LeaveCriticalSection(&m_mutex.m_internalMutex);
            return false;
        }

        ++m_mutex.m_recursionCount;
        return true;
    }

    return false;
}

void Mutex::unlock()
{
    --m_mutex.m_recursionCount;
    ::LeaveCriticalSection(&m_mutex.m_internalMutex);
}

} // namespace WebCore