ManagedData.h

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/*

License

Menge
Copyright © and trademark ™ 2012-14 University of North Carolina at Chapel Hill. 
All rights reserved.

Permission to use, copy, modify, and distribute this software and its documentation 
for educational, research, and non-profit purposes, without fee, and without a 
written agreement is hereby granted, provided that the above copyright notice, 
this paragraph, and the following four paragraphs appear in all copies.

This software program and documentation are copyrighted by the University of North 
Carolina at Chapel Hill. The software program and documentation are supplied "as is," 
without any accompanying services from the University of North Carolina at Chapel 
Hill or the authors. The University of North Carolina at Chapel Hill and the 
authors do not warrant that the operation of the program will be uninterrupted 
or error-free. The end-user understands that the program was developed for research 
purposes and is advised not to rely exclusively on the program for any reason.

IN NO EVENT SHALL THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL OR THE AUTHORS 
BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL 
DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS 
DOCUMENTATION, EVEN IF THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL OR THE 
AUTHORS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL AND THE AUTHORS SPECIFICALLY 
DISCLAIM ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE AND ANY STATUTORY WARRANTY 
OF NON-INFRINGEMENT. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND 
THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL AND THE AUTHORS HAVE NO OBLIGATIONS 
TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

Any questions or comments should be sent to the authors {menge,geom}@cs.unc.edu

*/

#ifndef __MANAGED_DATA_H__
#define __MANAGED_DATA_H__

#include "CoreConfig.h"
#include <map>
#include <string>

namespace Menge {

    class MENGE_API ManagedData {
    public:
        ManagedData():_refCount(0){}

        virtual ~ManagedData(){}

        int incRef() { return ++_refCount; }

        int decRef() { return --_refCount; }

        bool isUnreferenced() const { return _refCount == 0; }

    protected:
        int _refCount;
    };

    template < class TData >
    class ManagedDataWrapper {
    public:
        ManagedDataWrapper( TData * data ) {
            data->incRef();
            _data = data;
        }

        void freeData() {
            if ( _data->decRef() == 0 ) {
                delete _data;
            }
        }

    protected:
        TData * _data;
    };

    // These templated functions serve as the basis for loading new instances of a resource (or 
    //  grabbing them from the cached database.)
    //
    // To use them the derived class needs to satisfy the following requirements:
    //  1. The class, Data,  must have a PUBLIC static member: std::map< std::string, TData * >
    //      This class is a map that maps filenames to pointers to the corresponding loaded
    //      data.  If the filename is not a key in this map, then the data has never been loaded
    //  2. You must provide a function: Data * readData( const std::string )
    //      This function constructs a new Data, reads the file and populates the data file,
    //      ADDS THE DATA FILE TO THE MAP, and returns the pointer to the data.
    //  3. The wrapper class, T, must instantiate using TData * as the only argument with the
    //      constructor.
    //
    // If I do this, then any final user can simply call "T * myT = loadT( fileName );"  And get
    //      a pointer to the data contained in the fileName which prevents duplicate loading and
    //      automatically tracks references so when all the T's that reference a particular TData
    //      are destroyed.

    template< typename TData >
    TData * getResource( const std::string & name, std::map< std::string, TData * > & map ) {
        if ( map.find( name ) == map.end() ) {
            return 0x0;
        } else {
            return map[ name ];
        }
    }


    template< typename T, typename TData>
    T* loadManagedData( const std::string & fileName, TData * (*reader)(const std::string & ) ) {
        TData * data = getResource<TData>( fileName, TData::RESOURCES );
        if ( data == 0x0 ) {
            data = (*reader)( fileName );
            if ( data != 0x0 ) {
                TData::RESOURCES[ fileName ] = data;
            }
        }
        if ( data == 0x0 ) {
            return 0x0;
        }
        return new T( data );
    }


    template < typename TData >
    void removeResource( TData * data, std::map< std::string, TData * > & map ) {
        // remove self from the resources set
        typename std::map< std::string, TData *>::iterator itr = map.begin();
        for ( ; itr != map.end(); ++itr ) {
            if ( itr->second == data ) {
                map.erase( itr );
                break;
            }
        }
    }
}   // namespace Menge

#endif