boost/xpressive/detail/core/matcher/assert_bol_matcher.hpp

///////////////////////////////////////////////////////////////////////////////
// assert_bol_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_ASSERT_BOL_MATCHER_HPP_EAN_10_04_2005
#define BOOST_XPRESSIVE_DETAIL_CORE_MATCHER_ASSERT_BOL_MATCHER_HPP_EAN_10_04_2005
// MS compatible compilers support #pragma once
#if defined(_MSC_VER)
# pragma once
#endif
#include <boost/next_prior.hpp>
#include <boost/xpressive/detail/detail_fwd.hpp>
#include <boost/xpressive/detail/core/quant_style.hpp>
#include <boost/xpressive/detail/core/state.hpp>
#include <boost/xpressive/detail/core/matcher/assert_line_base.hpp>
namespace boost { namespace xpressive { namespace detail
{
    ///////////////////////////////////////////////////////////////////////////////
    // assert_bol_matcher
    //
    template<typename Traits>
    struct assert_bol_matcher
      : assert_line_base<Traits>
    {
        typedef typename Traits::char_type char_type;
        assert_bol_matcher(Traits const &tr)
          : assert_line_base<Traits>(tr)
        {
        }
        template<typename BidiIter, typename Next>
        bool match(match_state<BidiIter> &state, Next const &next) const
        {
            if(state.bos())
            {
                if(!state.flags_.match_bol_)
                {
                    return false;
                }
            }
            else
            {
                char_type ch = *boost::prior(state.cur_);
                // If the previous character is not a newline, we're not at the start of a line
                if(!traits_cast<Traits>(state).isctype(ch, this->newline_))
                {
                    return false;
                }
                // There is no line-break between \r and \n
                else if(ch == this->cr_ && !state.eos() && *state.cur_ == this->nl_)
                {
                    return false;
                }
            }
            return next.match(state);
        }
    };
}}}
#endif