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#ifndef INCLUDED_SLIDESHOW_STATE_HXX
#define INCLUDED_SLIDESHOW_STATE_HXX

#include <sal/types.h>
#include <boost/shared_ptr.hpp>


/* Definition of State interface */

namespace slideshow
{
    namespace internal
    {

        /** This interface represents a stateful object.

            The state ID returned by the getStateId() method
            abstractly encodes the object's state. When this ID
            changes, clients can assume that the object's state has
            changed.
         */
        class State
        {
        public:
            virtual ~State() {}

            /// Abstract, numerically encoded state ID 
            typedef ::std::size_t StateId;

            /** This method returns a numerical state identifier.

                The state ID returned by this method abstractly
                encodes the object's state. When this ID changes,
                clients can assume that the object's state has
                changed.

                @return an abstract, numerical state ID. 
             */
            virtual StateId getStateId() const = 0;
        };

        typedef ::boost::shared_ptr< State > StateSharedPtr;
    }
}

#endif /* INCLUDED_SLIDESHOW_STATE_HXX */

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