/*
 * 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",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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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 1.2 2002/11/04 15:22:05 tng Exp $
 * $Log: XMLRegisterCleanup.hpp,v $
 * Revision 1.2  2002/11/04 15:22:05  tng
 * C++ Namespace Support.
 *
 * 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>

XERCES_CPP_NAMESPACE_BEGIN

// 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;
	}
};

XERCES_CPP_NAMESPACE_END

#endif
