null_iterator.h

// Description: NullIterator class
// Detail: An iterator for sending data into oblivion.
// Documentation: iterator.txt

#ifndef PASTELSYS_NULL_ITERATOR_H
#define PASTELSYS_NULL_ITERATOR_H

#include "pastel/sys/mytypes.h"

#include <boost/operators.hpp>

#include <iterator>

namespace Pastel
{

    namespace NullIterator_
    {

        class NullObject
        {
        public:
            template <typename Type>
            void operator=(const Type&)
            {
            }
        };

        template <typename Derived, typename ValueType>
        class NullIteratorBase
            : public boost::random_access_iterator_helper<Derived, ValueType, integer>
        {
        private:
            typedef boost::random_access_iterator_helper<Derived, ValueType, integer>
                Base;

        public:
            // Using default copy constructor.
            // Using default assignment.
            // Using default destructor.

            NullIteratorBase()
                : data_()
            {
            }

            Derived& operator++()
            {
                return (Derived&)*this;
            }

            Derived& operator--()
            {
                return (Derived&)*this;
            }

            Derived& operator+=(
                integer)
            {
                return (Derived&)*this;
            }

            Derived& operator-=(
                integer)
            {
                return (Derived&)*this;
            }

            friend typename Base::difference_type operator-(
                const Derived&, const Derived&)
            {
                return 0;
            }

            typename Base::reference operator*() const
            {
                return (typename Base::reference)data_;
            }

            friend bool operator==(
                const Derived&, const Derived&)
            {
                return true;
            }

            friend bool operator<(
                const Derived&, const Derived&)
            {
                return false;
            }

        protected:
            ValueType data_;
        };

    }

    class NullIterator
        : public NullIterator_::NullIteratorBase<NullIterator, NullIterator_::NullObject>
    {
    };

    class ConstNullIterator
        : public NullIterator_::NullIteratorBase<ConstNullIterator, const NullIterator_::NullObject>
    {
    public:
        ConstNullIterator()
        {
        }

        ConstNullIterator(
            const NullIterator& that)
        {
        }
    };

}

#endif