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XMLRegisterCleanup.hpp

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00001 /*
00002  * The Apache Software License, Version 1.1
00003  * 
00004  * Copyright (c) 1999-2000 The Apache Software Foundation.  All rights
00005  * reserved.
00006  * 
00007  * Redistribution and use in source and binary forms, with or without
00008  * modification, are permitted provided that the following conditions
00009  * are met:
00010  * 
00011  * 1. Redistributions of source code must retain the above copyright
00012  *    notice, this list of conditions and the following disclaimer. 
00013  * 
00014  * 2. Redistributions in binary form must reproduce the above copyright
00015  *    notice, this list of conditions and the following disclaimer in
00016  *    the documentation and/or other materials provided with the
00017  *    distribution.
00018  * 
00019  * 3. The end-user documentation included with the redistribution,
00020  *    if any, must include the following acknowledgment:  
00021  *       "This product includes software developed by the
00022  *        Apache Software Foundation (http://www.apache.org/)."
00023  *    Alternately, this acknowledgment may appear in the software itself,
00024  *    if and wherever such third-party acknowledgments normally appear.
00025  * 
00026  * 4. The names "Xerces" and "Apache Software Foundation" must
00027  *    not be used to endorse or promote products derived from this
00028  *    software without prior written permission. For written 
00029  *    permission, please contact apache\@apache.org.
00030  * 
00031  * 5. Products derived from this software may not be called "Apache",
00032  *    nor may "Apache" appear in their name, without prior written
00033  *    permission of the Apache Software Foundation.
00034  * 
00035  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
00036  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
00037  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
00038  * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
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00041  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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00047  * ====================================================================
00048  * 
00049  * This software consists of voluntary contributions made by many
00050  * individuals on behalf of the Apache Software Foundation, and was
00051  * originally based on software copyright (c) 1999, International
00052  * Business Machines, Inc., http://www.ibm.com .  For more information
00053  * on the Apache Software Foundation, please see
00054  * <http://www.apache.org/>.
00055  */
00056 
00057 /*
00058  * $Id: XMLRegisterCleanup.hpp,v 1.1.1.1 2002/02/01 22:22:15 peiyongz Exp $
00059  * $Log: XMLRegisterCleanup.hpp,v $
00060  * Revision 1.1.1.1  2002/02/01 22:22:15  peiyongz
00061  * sane_include
00062  *
00063  * Revision 1.4  2001/10/25 21:55:29  peiyongz
00064  * copy ctor explicity declared private to prevent supprise.
00065  *
00066  * Revision 1.3  2001/10/24 18:13:06  peiyongz
00067  * CVS tag added
00068  *
00069  *
00070  */
00071 
00072 #if !defined(XMLREGISTERCLEANUP_HPP)
00073 #define XMLREGISTERCLEANUP_HPP
00074 
00075 #include <xercesc/util/Mutexes.hpp>
00076 
00077 // This is a mutex for exclusive use by this class
00078 extern XMLMutex* gXMLCleanupListMutex;
00079 
00080 // This is the head of a list of XMLRegisterCleanup objects that
00081 // is used during XMLPlatformUtils::Terminate() to find objects to
00082 // clean up
00083 class XMLRegisterCleanup;
00084 extern XMLRegisterCleanup* gXMLCleanupList;
00085 
00086 // 
00087 //  For internal use only.
00088 //
00089 //  This class is used by the platform utilities class to support 
00090 //  reinitialisation of global/static data which is lazily created. 
00091 //  Since that data is widely spread out the platform utilities
00092 //  class cannot know about them directly. So, the code that creates such
00093 //  objects creates an registers a cleanup for the object. The platform
00094 //  termination call will iterate the list and delete the objects.
00095 //
00096 //  N.B. These objects need to be statically allocated.  I couldn't think
00097 //  of a neat way of ensuring this - can anyone else?
00098 
00099 class XMLRegisterCleanup
00100 {
00101 public :
00102     // The cleanup function to be called on XMLPlatformUtils::Terminate()
00103     typedef void (*XMLCleanupFn)();
00104     
00105     void doCleanup() {
00106         // When performing cleanup, we only do this once, but we can
00107         // cope if somehow we have been called twice.
00108         if (m_cleanupFn) 
00109             m_cleanupFn();
00110 
00111         // We need to remove "this" from the list
00112         // irregardless of the cleanup Function
00113         unregisterCleanup();
00114     }
00115 
00116     // This function is called during initialisation of static data to
00117     // register a function to be called on XMLPlatformUtils::Terminate.
00118     // It gives an object that uses static data an opportunity to reset
00119     // such data.
00120     void registerCleanup(XMLCleanupFn cleanupFn) {
00121         // Store the cleanup function
00122         m_cleanupFn = cleanupFn;
00123         
00124         // Add this object to the list head, if it is not already 
00125         // present - which it shouldn't be.
00126         // This is done under a mutex to ensure thread safety.
00127         gXMLCleanupListMutex->lock();
00128         if (!m_nextCleanup && !m_prevCleanup) {
00129             m_nextCleanup = gXMLCleanupList;
00130             gXMLCleanupList = this;
00131 
00132             if (m_nextCleanup) 
00133                 m_nextCleanup->m_prevCleanup = this;
00134         }
00135         gXMLCleanupListMutex->unlock();
00136     }
00137 
00138     // This function can be called either from XMLPlatformUtils::Terminate
00139     // to state that the cleanup has been performed and should not be
00140     // performed again, or from code that you have written that determines
00141     // that cleanup is no longer necessary.
00142     void unregisterCleanup() {
00143         gXMLCleanupListMutex->lock();
00144 
00145         //
00146         // To protect against some compiler's (eg hp11) optimization
00147         // to change "this" as they update gXMLCleanupList
00148         //
00149         // refer to 
00150         // void XMLPlatformUtils::Terminate()
00151         //       ... 
00152         //       while (gXMLCleanupList)
00153         //            gXMLCleanupList->doCleanup();
00154         //
00155 
00156         XMLRegisterCleanup *tmpThis = (XMLRegisterCleanup*) this;
00157 
00158         // Unlink this object from the cleanup list
00159         if (m_nextCleanup) m_nextCleanup->m_prevCleanup = m_prevCleanup;
00160         
00161         if (!m_prevCleanup) gXMLCleanupList = m_nextCleanup;
00162         else m_prevCleanup->m_nextCleanup = m_nextCleanup;
00163 
00164         gXMLCleanupListMutex->unlock();
00165         
00166         // Reset the object to the default state
00167         tmpThis->resetCleanup();
00168     }
00169 
00170     // The default constructor sets a state that ensures that this object
00171     // will do nothing
00172     XMLRegisterCleanup()
00173     {
00174         resetCleanup();
00175     }
00176 
00177 private:
00178 
00179     //
00180     // unsupported ctor and operator
00181     //
00182     XMLRegisterCleanup(const XMLRegisterCleanup&)
00183     {}
00184 
00185     // This is the cleanup function to be called
00186     XMLCleanupFn m_cleanupFn;
00187 
00188     // These are list pointers to the next/prev cleanup function to be called
00189     XMLRegisterCleanup *m_nextCleanup, *m_prevCleanup;
00190 
00191     // This function reinitialises the object to the default state
00192     void resetCleanup() {
00193         m_nextCleanup = 0;
00194         m_prevCleanup = 0;
00195         m_cleanupFn = 0;
00196     }
00197 };
00198 
00199 #endif


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