finder.hpp

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                    return M;
                }


            private:
                iterator_range<search_iterator_type> m_Search;
                int m_Nth;
                PredicateT m_Comp;
            };

//  find head/tail implementation helpers ---------------------------//

            template<typename ForwardIteratorT>
                iterator_range<ForwardIteratorT>
            find_head_impl(
                ForwardIteratorT Begin,
                ForwardIteratorT End,
                unsigned int N,
                std::forward_iterator_tag )
            {
                typedef ForwardIteratorT input_iterator_type;
                typedef iterator_range<ForwardIteratorT> result_type;

                input_iterator_type It=Begin;
                for(
                    unsigned int Index=0;
                    Index<N && It!=End; ++Index,++It ) {};

                return result_type( Begin, It );
            }

            template< typename ForwardIteratorT >
                iterator_range<ForwardIteratorT>
            find_head_impl(
                ForwardIteratorT Begin,
                ForwardIteratorT End,
                unsigned int N,
                std::random_access_iterator_tag )
            {
                typedef ForwardIteratorT input_iterator_type;
                typedef iterator_range<ForwardIteratorT> result_type;

                if ( (End<=Begin) || ( static_cast<unsigned int>(End-Begin) < N ) )
                    return result_type( Begin, End );

                return result_type(Begin,Begin+N);
            }

            // Find head implementation
            template<typename ForwardIteratorT>
                iterator_range<ForwardIteratorT>
            find_head_impl(
                ForwardIteratorT Begin,
                ForwardIteratorT End,
                unsigned int N )
            {
                typedef BOOST_STRING_TYPENAME boost::detail::
                    iterator_traits<ForwardIteratorT>::iterator_category category;

                return find_head_impl( Begin, End, N, category() );
            }

            template< typename ForwardIteratorT >
                iterator_range<ForwardIteratorT>
            find_tail_impl(
                ForwardIteratorT Begin,
                ForwardIteratorT End,
                unsigned int N,
                std::forward_iterator_tag )
            {
                typedef ForwardIteratorT input_iterator_type;
                typedef iterator_range<ForwardIteratorT> result_type;

                unsigned int Index=0;
                input_iterator_type It=Begin;
                input_iterator_type It2=Begin;

                // Advance It2 by N increments
                for( Index=0; Index<N && It2!=End; ++Index,++It2 ) {};

                // Advance It, It2 to the end
                for(; It2!=End; ++It,++It2 ) {};

                return result_type( It, It2 );
            }

            template< typename ForwardIteratorT >
                iterator_range<ForwardIteratorT>
            find_tail_impl(
                ForwardIteratorT Begin,
                ForwardIteratorT End,
                unsigned int N,
                std::bidirectional_iterator_tag )
            {
                typedef ForwardIteratorT input_iterator_type;
                typedef iterator_range<ForwardIteratorT> result_type;

                input_iterator_type It=End;
                for(
                    unsigned int Index=0;
                    Index<N && It!=Begin; ++Index,--It ) {};

                return result_type( It, End );
            }

            template< typename ForwardIteratorT >
                iterator_range<ForwardIteratorT>
            find_tail_impl(
                ForwardIteratorT Begin,
                ForwardIteratorT End,
                unsigned int N,
                std::random_access_iterator_tag )
            {
                typedef ForwardIteratorT input_iterator_type;
                typedef iterator_range<ForwardIteratorT> result_type;

                if ( (End<=Begin) || ( static_cast<unsigned int>(End-Begin) < N ) )
                    return result_type( Begin, End );

                return result_type( End-N, End );
            }

                        // Operation
            template< typename ForwardIteratorT >
            iterator_range<ForwardIteratorT>
            find_tail_impl(
                ForwardIteratorT Begin,
                ForwardIteratorT End,
                unsigned int N )
            {
                typedef BOOST_STRING_TYPENAME boost::detail::
                    iterator_traits<ForwardIteratorT>::iterator_category category;

                return find_tail_impl( Begin, End, N, category() );
            }



//  find head functor -----------------------------------------------//


            // find a head in the sequence ( functor )
            /*
                This functor find a head of the specified range. For
                a specified N, the head is a subsequence of N starting
                elements of the range.
            */
            struct head_finderF
            {
                // Construction
                head_finderF( int N ) : m_N(N) {}

                // Operation
                template< typename ForwardIteratorT >
                iterator_range<ForwardIteratorT>
                operator()(
                    ForwardIteratorT Begin,
                    ForwardIteratorT End ) const
                {
                    if(m_N>=0)
                    {
                        return find_head_impl( Begin, End, m_N );
                    }
                    else
                    {
                        iterator_range<ForwardIteratorT> Res=
                            find_tail_impl( Begin, End, -m_N );

                        return make_iterator_range(Begin, Res.begin());
                    }
                }

            private:
                int m_N;
            };

//  find tail functor -----------------------------------------------//


            // find a tail in the sequence ( functor )
            /*
                This functor find a tail of the specified range. For
                a specified N, the head is a subsequence of N starting
                elements of the range.
            */
            struct tail_finderF
            {
                // Construction
                tail_finderF( int N ) : m_N(N) {}

                // Operation
                template< typename ForwardIteratorT >
                iterator_range<ForwardIteratorT>
                operator()(
                    ForwardIteratorT Begin,
                    ForwardIteratorT End ) const
                {
                    if(m_N>=0)
                    {
                        return find_tail_impl( Begin, End, m_N );
                    }
                    else
                    {
                        iterator_range<ForwardIteratorT> Res=
                            find_head_impl( Begin, End, -m_N );

                        return make_iterator_range(Res.end(), End);
                    }
                }

            private:
                int m_N;
            };

//  find token functor -----------------------------------------------//

            // find a token in a sequence ( functor )
            /*
                This find functor finds a token specified be a predicate
                in a sequence. It is equivalent of std::find algorithm,
                with an exception that it return range instead of a single
                iterator.

                If bCompress is set to true, adjacent matching tokens are
                concatenated into one match.
            */
            template< typename PredicateT >
            struct token_finderF
            {
                // Construction
                token_finderF(
                    PredicateT Pred,
                    token_compress_mode_type eCompress=token_compress_off ) :
                        m_Pred(Pred), m_eCompress(eCompress) {}

                // Operation
                template< typename ForwardIteratorT >
                iterator_range<ForwardIteratorT>
                operator()(
                    ForwardIteratorT Begin,
                    ForwardIteratorT End ) const
                {
                    typedef iterator_range<ForwardIteratorT> result_type;

                    ForwardIteratorT It=std::find_if( Begin, End, m_Pred );

                    if( It==End )
                    {
                        return result_type( End, End );
                    }
                    else
                    {
                        ForwardIteratorT It2=It;

                        if( m_eCompress==token_compress_on )
                        {
                            // Find first non-matching character
                            while( It2!=End && m_Pred(*It2) ) ++It2;
                        }
                        else
                        {
                            // Advance by one position
                            ++It2;
                        }

                        return result_type( It, It2 );
                    }
                }

            private:
                PredicateT m_Pred;
                token_compress_mode_type m_eCompress;
            };

//  find range functor -----------------------------------------------//

            // find a range in the sequence ( functor )
            /*
                This functor actually does not perform any find operation.
                It always returns given iterator range as a result.
            */
            template<typename ForwardIterator1T>
            struct range_finderF
            {
                typedef ForwardIterator1T input_iterator_type;
                typedef iterator_range<input_iterator_type> result_type;

                // Construction
                range_finderF(
                    input_iterator_type Begin,
                    input_iterator_type End ) : m_Range(Begin, End) {}

                range_finderF(const iterator_range<input_iterator_type>& Range) :
                    m_Range(Range) {}

                // Operation
                template< typename ForwardIterator2T >
                iterator_range<ForwardIterator2T>
                operator()(
                    ForwardIterator2T,
                    ForwardIterator2T ) const
                {
#if BOOST_WORKAROUND( __MWERKS__, <= 0x3003 ) 
                    return iterator_range<const ForwardIterator2T>(this->m_Range);
#elif BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
                    return iterator_range<ForwardIterator2T>(m_Range.begin(), m_Range.end());
#else
                    return m_Range;
#endif
                }

            private:
                iterator_range<input_iterator_type> m_Range;
            };


        } // namespace detail
    } // namespace algorithm
} // namespace boost

#endif  // BOOST_STRING_FINDER_DETAIL_HPP