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    00001 /*
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    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.
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    00019  * 3. The end-user documentation included with the redistribution,
    00020  *    if any, must include the following acknowledgment:
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    00024  *    if and wherever such third-party acknowledgments normally appear.
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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
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    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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