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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
00039  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
00040  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
00041  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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00045  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00046  * SUCH DAMAGE.
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
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00054  * <http://www.apache.org/>.
00055  */
00056 
00057 /*
00058  * $Id: XMLRegisterCleanup.hpp,v 1.2 2002/11/04 15:22:05 tng Exp $
00059  * $Log: XMLRegisterCleanup.hpp,v $
00060  * Revision 1.2  2002/11/04 15:22:05  tng
00061  * C++ Namespace Support.
00062  *
00063  * Revision 1.1.1.1  2002/02/01 22:22:15  peiyongz
00064  * sane_include
00065  *
00066  * Revision 1.4  2001/10/25 21:55:29  peiyongz
00067  * copy ctor explicity declared private to prevent supprise.
00068  *
00069  * Revision 1.3  2001/10/24 18:13:06  peiyongz
00070  * CVS tag added
00071  *
00072  *
00073  */
00074 
00075 #if !defined(XMLREGISTERCLEANUP_HPP)
00076 #define XMLREGISTERCLEANUP_HPP
00077 
00078 #include <xercesc/util/Mutexes.hpp>
00079 
00080 XERCES_CPP_NAMESPACE_BEGIN
00081 
00082 // This is a mutex for exclusive use by this class
00083 extern XMLMutex* gXMLCleanupListMutex;
00084 
00085 // This is the head of a list of XMLRegisterCleanup objects that
00086 // is used during XMLPlatformUtils::Terminate() to find objects to
00087 // clean up
00088 class XMLRegisterCleanup;
00089 extern XMLRegisterCleanup* gXMLCleanupList;
00090 
00091 //
00092 //  For internal use only.
00093 //
00094 //  This class is used by the platform utilities class to support
00095 //  reinitialisation of global/static data which is lazily created.
00096 //  Since that data is widely spread out the platform utilities
00097 //  class cannot know about them directly. So, the code that creates such
00098 //  objects creates an registers a cleanup for the object. The platform
00099 //  termination call will iterate the list and delete the objects.
00100 //
00101 //  N.B. These objects need to be statically allocated.  I couldn't think
00102 //  of a neat way of ensuring this - can anyone else?
00103 
00104 class XMLRegisterCleanup
00105 {
00106 public :
00107     // The cleanup function to be called on XMLPlatformUtils::Terminate()
00108     typedef void (*XMLCleanupFn)();
00109     
00110     void doCleanup() {
00111         // When performing cleanup, we only do this once, but we can
00112         // cope if somehow we have been called twice.
00113         if (m_cleanupFn)
00114             m_cleanupFn();
00115 
00116         // We need to remove "this" from the list
00117         // irregardless of the cleanup Function
00118         unregisterCleanup();
00119     }
00120 
00121     // This function is called during initialisation of static data to
00122     // register a function to be called on XMLPlatformUtils::Terminate.
00123     // It gives an object that uses static data an opportunity to reset
00124     // such data.
00125     void registerCleanup(XMLCleanupFn cleanupFn) {
00126         // Store the cleanup function
00127         m_cleanupFn = cleanupFn;
00128         
00129         // Add this object to the list head, if it is not already
00130         // present - which it shouldn't be.
00131         // This is done under a mutex to ensure thread safety.
00132         gXMLCleanupListMutex->lock();
00133         if (!m_nextCleanup && !m_prevCleanup) {
00134             m_nextCleanup = gXMLCleanupList;
00135             gXMLCleanupList = this;
00136 
00137             if (m_nextCleanup)
00138                 m_nextCleanup->m_prevCleanup = this;
00139         }
00140         gXMLCleanupListMutex->unlock();
00141     }
00142 
00143     // This function can be called either from XMLPlatformUtils::Terminate
00144     // to state that the cleanup has been performed and should not be
00145     // performed again, or from code that you have written that determines
00146     // that cleanup is no longer necessary.
00147     void unregisterCleanup() {
00148         gXMLCleanupListMutex->lock();
00149 
00150         //
00151         // To protect against some compiler's (eg hp11) optimization
00152         // to change "this" as they update gXMLCleanupList
00153         //
00154         // refer to
00155         // void XMLPlatformUtils::Terminate()
00156         //       ...
00157         //       while (gXMLCleanupList)
00158         //            gXMLCleanupList->doCleanup();
00159         //
00160 
00161         XMLRegisterCleanup *tmpThis = (XMLRegisterCleanup*) this;
00162 
00163         // Unlink this object from the cleanup list
00164         if (m_nextCleanup) m_nextCleanup->m_prevCleanup = m_prevCleanup;
00165         
00166         if (!m_prevCleanup) gXMLCleanupList = m_nextCleanup;
00167         else m_prevCleanup->m_nextCleanup = m_nextCleanup;
00168 
00169         gXMLCleanupListMutex->unlock();
00170         
00171         // Reset the object to the default state
00172         tmpThis->resetCleanup();
00173     }
00174 
00175     // The default constructor sets a state that ensures that this object
00176     // will do nothing
00177     XMLRegisterCleanup()
00178     {
00179         resetCleanup();
00180     }
00181 
00182 private:
00183 
00184     //
00185     // unsupported ctor and operator
00186     //
00187     XMLRegisterCleanup(const XMLRegisterCleanup&)
00188     {}
00189 
00190     // This is the cleanup function to be called
00191     XMLCleanupFn m_cleanupFn;
00192 
00193     // These are list pointers to the next/prev cleanup function to be called
00194     XMLRegisterCleanup *m_nextCleanup, *m_prevCleanup;
00195 
00196     // This function reinitialises the object to the default state
00197     void resetCleanup() {
00198         m_nextCleanup = 0;
00199         m_prevCleanup = 0;
00200         m_cleanupFn = 0;
00201     }
00202 };
00203 
00204 XERCES_CPP_NAMESPACE_END
00205 
00206 #endif


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