repeat_end_matcher.hpp

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///////////////////////////////////////////////////////////////////////////////
// repeat_end_matcher.hpp
//
//  Copyright 2008 Eric Niebler. Distributed under the Boost
//  Software License, Version 1.0. (See accompanying file
//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_XPRESSIVE_DETAIL_CORE_MATCHER_REPEAT_END_MATCHER_HPP_EAN_10_04_2005
#define BOOST_XPRESSIVE_DETAIL_CORE_MATCHER_REPEAT_END_MATCHER_HPP_EAN_10_04_2005

// MS compatible compilers support #pragma once
#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif

#include <boost/mpl/bool.hpp>
#include <boost/xpressive/detail/detail_fwd.hpp>
#include <boost/xpressive/detail/core/quant_style.hpp>
#include <boost/xpressive/detail/core/state.hpp>

namespace boost { namespace xpressive { namespace detail
{

    ///////////////////////////////////////////////////////////////////////////////
    // repeat_end_matcher
    //
    template<typename Greedy>
    struct repeat_end_matcher
      : quant_style<quant_none, 0, false>
    {
        typedef Greedy greedy_type;
        int mark_number_;
        unsigned int min_, max_;
        mutable void const *back_;

        repeat_end_matcher(int mark_number, unsigned int min, unsigned int max)
          : mark_number_(mark_number)
          , min_(min)
          , max_(max)
          , back_(0)
        {
        }

        template<typename BidiIter, typename Next>
        bool match(match_state<BidiIter> &state, Next const &next) const
        {
            // prevent repeated zero-width sub-matches from causing infinite recursion
            sub_match_impl<BidiIter> &br = state.sub_match(this->mark_number_);

            if(br.zero_width_ && br.begin_ == state.cur_)
            {
                return next.skip_match(state);
            }

            bool old_zero_width = br.zero_width_;
            br.zero_width_ = (br.begin_ == state.cur_);

            if(this->match_(state, next, greedy_type()))
            {
                return true;
            }

            br.zero_width_ = old_zero_width;
            return false;
        }

        // greedy, variable-width quantifier
        template<typename BidiIter, typename Next>
        bool match_(match_state<BidiIter> &state, Next const &next, mpl::true_) const
        {
            sub_match_impl<BidiIter> &br = state.sub_match(this->mark_number_);

            if(this->max_ > br.repeat_count_)
            {
                ++br.repeat_count_;
                // loop back to the expression "pushed" in repeat_begin_matcher::match
                if(next.top_match(state, this->back_))
                {
                    return true;
                }
                else if(--br.repeat_count_ < this->min_)
                {
                    return false;
                }
            }

            // looping finished, continue matching the rest of the pattern
            return next.skip_match(state);
        }

        // non-greedy, variable-width quantifier
        template<typename BidiIter, typename Next>
        bool match_(match_state<BidiIter> &state, Next const &next, mpl::false_) const
        {
            sub_match_impl<BidiIter> &br = state.sub_match(this->mark_number_);

            if(this->min_ <= br.repeat_count_)
            {
                if(next.skip_match(state))
                {
                    return true;
                }
            }

            if(this->max_ > br.repeat_count_)
            {
                ++br.repeat_count_;
                if(next.top_match(state, this->back_))
                {
                    return true;
                }
                --br.repeat_count_;
            }

            return false;
        }
    };

}}}

#endif