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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
00042  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
00043  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
00044  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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
00053  * on the Apache Software Foundation, please see
00054  * <http://www.apache.org/>.
00055  */
00056 
00057 /*
00058  * $Id: XMLRegisterCleanup.hpp,v 1.3 2004/01/29 11:48:47 cargilld Exp $
00059  * $Log: XMLRegisterCleanup.hpp,v $
00060  * Revision 1.3  2004/01/29 11:48:47  cargilld
00061  * Code cleanup changes to get rid of various compiler diagnostic messages.
00062  *
00063  * Revision 1.2  2002/11/04 15:22:05  tng
00064  * C++ Namespace Support.
00065  *
00066  * Revision 1.1.1.1  2002/02/01 22:22:15  peiyongz
00067  * sane_include
00068  *
00069  * Revision 1.4  2001/10/25 21:55:29  peiyongz
00070  * copy ctor explicity declared private to prevent supprise.
00071  *
00072  * Revision 1.3  2001/10/24 18:13:06  peiyongz
00073  * CVS tag added
00074  *
00075  *
00076  */
00077 
00078 #if !defined(XMLREGISTERCLEANUP_HPP)
00079 #define XMLREGISTERCLEANUP_HPP
00080 
00081 #include <xercesc/util/Mutexes.hpp>
00082 
00083 XERCES_CPP_NAMESPACE_BEGIN
00084 
00085 // This is a mutex for exclusive use by this class
00086 extern XMLMutex* gXMLCleanupListMutex;
00087 
00088 // This is the head of a list of XMLRegisterCleanup objects that
00089 // is used during XMLPlatformUtils::Terminate() to find objects to
00090 // clean up
00091 class XMLRegisterCleanup;
00092 extern XMLRegisterCleanup* gXMLCleanupList;
00093 
00094 //
00095 //  For internal use only.
00096 //
00097 //  This class is used by the platform utilities class to support
00098 //  reinitialisation of global/static data which is lazily created.
00099 //  Since that data is widely spread out the platform utilities
00100 //  class cannot know about them directly. So, the code that creates such
00101 //  objects creates an registers a cleanup for the object. The platform
00102 //  termination call will iterate the list and delete the objects.
00103 //
00104 //  N.B. These objects need to be statically allocated.  I couldn't think
00105 //  of a neat way of ensuring this - can anyone else?
00106 
00107 class XMLRegisterCleanup
00108 {
00109 public :
00110     // The cleanup function to be called on XMLPlatformUtils::Terminate()
00111     typedef void (*XMLCleanupFn)();
00112     
00113     void doCleanup() {
00114         // When performing cleanup, we only do this once, but we can
00115         // cope if somehow we have been called twice.
00116         if (m_cleanupFn)
00117             m_cleanupFn();
00118 
00119         // We need to remove "this" from the list
00120         // irregardless of the cleanup Function
00121         unregisterCleanup();
00122     }
00123 
00124     // This function is called during initialisation of static data to
00125     // register a function to be called on XMLPlatformUtils::Terminate.
00126     // It gives an object that uses static data an opportunity to reset
00127     // such data.
00128     void registerCleanup(XMLCleanupFn cleanupFn) {
00129         // Store the cleanup function
00130         m_cleanupFn = cleanupFn;
00131         
00132         // Add this object to the list head, if it is not already
00133         // present - which it shouldn't be.
00134         // This is done under a mutex to ensure thread safety.
00135         gXMLCleanupListMutex->lock();
00136         if (!m_nextCleanup && !m_prevCleanup) {
00137             m_nextCleanup = gXMLCleanupList;
00138             gXMLCleanupList = this;
00139 
00140             if (m_nextCleanup)
00141                 m_nextCleanup->m_prevCleanup = this;
00142         }
00143         gXMLCleanupListMutex->unlock();
00144     }
00145 
00146     // This function can be called either from XMLPlatformUtils::Terminate
00147     // to state that the cleanup has been performed and should not be
00148     // performed again, or from code that you have written that determines
00149     // that cleanup is no longer necessary.
00150     void unregisterCleanup() {
00151         gXMLCleanupListMutex->lock();
00152 
00153         //
00154         // To protect against some compiler's (eg hp11) optimization
00155         // to change "this" as they update gXMLCleanupList
00156         //
00157         // refer to
00158         // void XMLPlatformUtils::Terminate()
00159         //       ...
00160         //       while (gXMLCleanupList)
00161         //            gXMLCleanupList->doCleanup();
00162         //
00163 
00164         XMLRegisterCleanup *tmpThis = (XMLRegisterCleanup*) this;
00165 
00166         // Unlink this object from the cleanup list
00167         if (m_nextCleanup) m_nextCleanup->m_prevCleanup = m_prevCleanup;
00168         
00169         if (!m_prevCleanup) gXMLCleanupList = m_nextCleanup;
00170         else m_prevCleanup->m_nextCleanup = m_nextCleanup;
00171 
00172         gXMLCleanupListMutex->unlock();
00173         
00174         // Reset the object to the default state
00175         tmpThis->resetCleanup();
00176     }
00177 
00178     // The default constructor sets a state that ensures that this object
00179     // will do nothing
00180     XMLRegisterCleanup()
00181     {
00182         resetCleanup();
00183     }
00184 
00185 private:
00186     // -----------------------------------------------------------------------
00187     //  Unimplemented constructors and operators
00188     // -----------------------------------------------------------------------
00189     XMLRegisterCleanup(const XMLRegisterCleanup&);
00190     XMLRegisterCleanup& operator=(const XMLRegisterCleanup&);
00191 
00192     // This is the cleanup function to be called
00193     XMLCleanupFn m_cleanupFn;
00194 
00195     // These are list pointers to the next/prev cleanup function to be called
00196     XMLRegisterCleanup *m_nextCleanup, *m_prevCleanup;
00197 
00198     // This function reinitialises the object to the default state
00199     void resetCleanup() {
00200         m_nextCleanup = 0;
00201         m_prevCleanup = 0;
00202         m_cleanupFn = 0;
00203     }
00204 };
00205 
00206 XERCES_CPP_NAMESPACE_END
00207 
00208 #endif


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