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XMLRegisterCleanup.hpp

/*
 * The Apache Software License, Version 1.1
 * 
 * Copyright (c) 1999-2000 The Apache Software Foundation.  All rights
 * reserved.
 * 
 * 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. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:  
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 * 
 * 4. The names "Xerces" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written 
 *    permission, please contact apache\@apache.org.
 * 
 * 5. Products derived from this software may not be called "Apache",
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 * 
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 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION 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
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 * 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.
 * ====================================================================
 * 
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation, and was
 * originally based on software copyright (c) 1999, International
 * Business Machines, Inc., http://www.ibm.com .  For more information
 * on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

/*
 * $Id: XMLRegisterCleanup.hpp,v 1.1 2002/05/11 21:20:03 bhavani Exp $
 * $Log: XMLRegisterCleanup.hpp,v $
 * Revision 1.1  2002/05/11 21:20:03  bhavani
 * CR#CR062582# adding xercesc 1.7 file
 *
 * Revision 1.1.1.1  2002/02/01 22:22:15  peiyongz
 * sane_include
 *
 * Revision 1.4  2001/10/25 21:55:29  peiyongz
 * copy ctor explicity declared private to prevent supprise.
 *
 * Revision 1.3  2001/10/24 18:13:06  peiyongz
 * CVS tag added
 *
 *
 */

#if !defined(XMLREGISTERCLEANUP_HPP)
#define XMLREGISTERCLEANUP_HPP

#include <xercesc/util/Mutexes.hpp>

// This is a mutex for exclusive use by this class
extern XMLMutex* gXMLCleanupListMutex;

// This is the head of a list of XMLRegisterCleanup objects that
// is used during XMLPlatformUtils::Terminate() to find objects to
// clean up
class XMLRegisterCleanup;
extern XMLRegisterCleanup* gXMLCleanupList;

// 
//  For internal use only.
//
//  This class is used by the platform utilities class to support 
//  reinitialisation of global/static data which is lazily created. 
//  Since that data is widely spread out the platform utilities
//  class cannot know about them directly. So, the code that creates such
//  objects creates an registers a cleanup for the object. The platform
//  termination call will iterate the list and delete the objects.
//
//  N.B. These objects need to be statically allocated.  I couldn't think
//  of a neat way of ensuring this - can anyone else?

class XMLRegisterCleanup
{
public :
        // The cleanup function to be called on XMLPlatformUtils::Terminate()
        typedef void (*XMLCleanupFn)();
        
        void doCleanup() {
                // When performing cleanup, we only do this once, but we can
                // cope if somehow we have been called twice.
                if (m_cleanupFn) 
            m_cleanupFn();

        // We need to remove "this" from the list
        // irregardless of the cleanup Function
        unregisterCleanup();
        }

        // This function is called during initialisation of static data to
        // register a function to be called on XMLPlatformUtils::Terminate.
        // It gives an object that uses static data an opportunity to reset
        // such data.
        void registerCleanup(XMLCleanupFn cleanupFn) {
                // Store the cleanup function
                m_cleanupFn = cleanupFn;
                
                // Add this object to the list head, if it is not already 
                // present - which it shouldn't be.
                // This is done under a mutex to ensure thread safety.
                gXMLCleanupListMutex->lock();
                if (!m_nextCleanup && !m_prevCleanup) {
                        m_nextCleanup = gXMLCleanupList;
                        gXMLCleanupList = this;

                        if (m_nextCleanup) 
                                m_nextCleanup->m_prevCleanup = this;
                }
                gXMLCleanupListMutex->unlock();
        }

        // This function can be called either from XMLPlatformUtils::Terminate
        // to state that the cleanup has been performed and should not be
        // performed again, or from code that you have written that determines
        // that cleanup is no longer necessary.
        void unregisterCleanup() {
                gXMLCleanupListMutex->lock();

        //
        // To protect against some compiler's (eg hp11) optimization
        // to change "this" as they update gXMLCleanupList
        //
        // refer to 
        // void XMLPlatformUtils::Terminate()
        //       ... 
        //       while (gXMLCleanupList)
                //            gXMLCleanupList->doCleanup();
        //

        XMLRegisterCleanup *tmpThis = (XMLRegisterCleanup*) this;

        // Unlink this object from the cleanup list
                if (m_nextCleanup) m_nextCleanup->m_prevCleanup = m_prevCleanup;
                
                if (!m_prevCleanup) gXMLCleanupList = m_nextCleanup;
                else m_prevCleanup->m_nextCleanup = m_nextCleanup;

                gXMLCleanupListMutex->unlock();
                
                // Reset the object to the default state
                tmpThis->resetCleanup();
        }

        // The default constructor sets a state that ensures that this object
        // will do nothing
        XMLRegisterCleanup()
        {
                resetCleanup();
        }

private:

    //
    // unsupported ctor and operator
    //
        XMLRegisterCleanup(const XMLRegisterCleanup&)
        {}

        // This is the cleanup function to be called
        XMLCleanupFn m_cleanupFn;

        // These are list pointers to the next/prev cleanup function to be called
        XMLRegisterCleanup *m_nextCleanup, *m_prevCleanup;

        // This function reinitialises the object to the default state
        void resetCleanup() {
                m_nextCleanup = 0;
                m_prevCleanup = 0;
                m_cleanupFn = 0;
        }
};

#endif

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