glpublisher.h

/*
Copyright (c) 2000-2003 Lee Thomason (www.grinninglizard.com)
Grinning Lizard Utilities.

This software is provided 'as-is', without any express or implied 
warranty. In no event will the authors be held liable for any 
damages arising from the use of this software.

Permission is granted to anyone to use this software for any 
purpose, including commercial applications, and to alter it and 
redistribute it freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must 
not claim that you wrote the original software. If you use this 
software in a product, an acknowledgment in the product documentation 
would be appreciated but is not required.

2. Altered source versions must be plainly marked as such, and 
must not be misrepresented as being the original software.

3. This notice may not be removed or altered from any source 
distribution.
*/


#ifndef GRINLIZ_PUBLISHER_INCLUDED
#define GRINLIZ_PUBLISHER_INCLUDED

#ifdef _MSC_VER
#pragma warning( disable : 4786 )
#endif

//#include <stdlib.h>
//#include <stdio.h>
#include <set>

namespace grinliz {

template< class LISTENER_CLASS >
class Publisher
{
  public:

    typedef typename std::set<LISTENER_CLASS*>::iterator iterator;
    typedef typename std::set<LISTENER_CLASS*>::const_iterator const_iterator;
     
        Publisher() : copyValid( false )        {}
          
        ~Publisher()
        {
                for(    iterator listenerIterator = listeners.begin();
                                listenerIterator != listeners.end();
                                ++listenerIterator )
                {
                        (*listenerIterator)->publishers.erase( this );
                }
        }

        void AddListener( LISTENER_CLASS* add )                 
        { 
                copyValid = false;
                listeners.insert( add ); 
                add->publishers.insert( this );
        }

        void RemoveListener( LISTENER_CLASS* remove )   
        { 
                copyValid = false;
                remove->publishers.erase( this );
                listeners.erase( remove );
        }
 
    const_iterator begin()      {       if ( !copyValid )
                                                                {
                                                                        listenersCopy.clear();
                                                                        listenersCopy = listeners;
                                                                        copyValid = true;
                                                                }
                                                                return listenersCopy.begin(); 
                                                        }

    const_iterator end()      { return listenersCopy.end(); }
 
  private:
        std::set<LISTENER_CLASS*> listeners;
        // Okay, it's very natural to want to Add/Remove while iterating
        // through the set. Even with documentation, it's just too easy
        // a mistake to make. Changing the set while iterating will 
        // crash and invalidate the     set. To overcome this, begin() makes a copy.
        // But we keep a flag around so this doesn't happen unless it needs to.
        bool copyValid;
        std::set<LISTENER_CLASS*> listenersCopy;
};


template <class LISTENER_CLASS>
class Listener
{
        friend class Publisher< LISTENER_CLASS >;

  private:
        std::set< Publisher<LISTENER_CLASS>* > publishers;
    typedef typename std::set< Publisher<LISTENER_CLASS>* >::iterator iterator;

  public:
        virtual ~Listener()
        {
            // This a strange bit of code. The RemoveListener call
            // will result the Publisher class reaching into this class
            // to erase the Publisher*. Therefore, the iterator will 
            // continually be invalidated; hence always use begin() and 
            // break if end().
            //
            // The other odd bit of code is the back-cast to our child
            // type - LISTENER_CLASS. Sleazy c++ trick.
            //
                while ( true )
                {
                        iterator it = publishers.begin();
                        if ( it == publishers.end() ) break;
                        (*it)->RemoveListener( static_cast< LISTENER_CLASS* >( this ) );
                }
        }
};

};      // namespace grinliz
#endif

---