| /////////////////////////////////////////////////////////////////////////////// |
| // lookbehind_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_LOOKBEHIND_MATCHER_HPP_EAN_10_04_2005 |
| #define BOOST_XPRESSIVE_DETAIL_CORE_MATCHER_LOOKBEHIND_MATCHER_HPP_EAN_10_04_2005 |
| |
| // MS compatible compilers support #pragma once |
| #if defined(_MSC_VER) && (_MSC_VER >= 1020) |
| # pragma once |
| #endif |
| |
| #include <boost/assert.hpp> |
| #include <boost/xpressive/regex_error.hpp> |
| #include <boost/xpressive/regex_constants.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/utility/algorithm.hpp> |
| #include <boost/xpressive/detail/utility/save_restore.hpp> |
| #include <boost/xpressive/detail/utility/ignore_unused.hpp> |
| |
| namespace boost { namespace xpressive { namespace detail |
| { |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // lookbehind_matcher |
| // Xpr can be either a static_xpression or a shared_matchable |
| template<typename Xpr> |
| struct lookbehind_matcher |
| : quant_style<quant_none, 0, Xpr::pure> |
| { |
| lookbehind_matcher(Xpr const &xpr, std::size_t wid, bool no, bool pure = Xpr::pure) |
| : xpr_(xpr) |
| , not_(no) |
| , pure_(pure) |
| , width_(wid) |
| { |
| BOOST_XPR_ENSURE_(!is_unknown(this->width_), regex_constants::error_badlookbehind, |
| "Variable-width look-behind assertions are not supported"); |
| } |
| |
| void inverse() |
| { |
| this->not_ = !this->not_; |
| } |
| |
| template<typename BidiIter, typename Next> |
| bool match(match_state<BidiIter> &state, Next const &next) const |
| { |
| return Xpr::pure || this->pure_ |
| ? this->match_(state, next, mpl::true_()) |
| : this->match_(state, next, mpl::false_()); |
| } |
| |
| template<typename BidiIter, typename Next> |
| bool match_(match_state<BidiIter> &state, Next const &next, mpl::true_) const |
| { |
| typedef typename iterator_difference<BidiIter>::type difference_type; |
| BidiIter const tmp = state.cur_; |
| if(!detail::advance_to(state.cur_, -static_cast<difference_type>(this->width_), state.begin_)) |
| { |
| state.cur_ = tmp; |
| return this->not_ ? next.match(state) : false; |
| } |
| |
| if(this->not_) |
| { |
| if(this->xpr_.match(state)) |
| { |
| BOOST_ASSERT(state.cur_ == tmp); |
| return false; |
| } |
| state.cur_ = tmp; |
| if(next.match(state)) |
| { |
| return true; |
| } |
| } |
| else |
| { |
| if(!this->xpr_.match(state)) |
| { |
| state.cur_ = tmp; |
| return false; |
| } |
| BOOST_ASSERT(state.cur_ == tmp); |
| if(next.match(state)) |
| { |
| return true; |
| } |
| } |
| |
| BOOST_ASSERT(state.cur_ == tmp); |
| return false; |
| } |
| |
| template<typename BidiIter, typename Next> |
| bool match_(match_state<BidiIter> &state, Next const &next, mpl::false_) const |
| { |
| typedef typename iterator_difference<BidiIter>::type difference_type; |
| BidiIter const tmp = state.cur_; |
| if(!detail::advance_to(state.cur_, -static_cast<difference_type>(this->width_), state.begin_)) |
| { |
| state.cur_ = tmp; |
| return this->not_ ? next.match(state) : false; |
| } |
| |
| // matching xpr could produce side-effects, save state |
| memento<BidiIter> mem = save_sub_matches(state); |
| |
| if(this->not_) |
| { |
| // negative look-ahead assertions do not trigger partial matches. |
| save_restore<bool> partial_match(state.found_partial_match_); |
| detail::ignore_unused(partial_match); |
| |
| if(this->xpr_.match(state)) |
| { |
| restore_action_queue(mem, state); |
| restore_sub_matches(mem, state); |
| BOOST_ASSERT(state.cur_ == tmp); |
| return false; |
| } |
| state.cur_ = tmp; |
| restore_action_queue(mem, state); |
| if(next.match(state)) |
| { |
| reclaim_sub_matches(mem, state, true); |
| return true; |
| } |
| reclaim_sub_matches(mem, state, false); |
| } |
| else |
| { |
| if(!this->xpr_.match(state)) |
| { |
| state.cur_ = tmp; |
| restore_action_queue(mem, state); |
| reclaim_sub_matches(mem, state, false); |
| return false; |
| } |
| BOOST_ASSERT(state.cur_ == tmp); |
| restore_action_queue(mem, state); |
| if(next.match(state)) |
| { |
| reclaim_sub_matches(mem, state, true); |
| return true; |
| } |
| restore_sub_matches(mem, state); |
| } |
| |
| BOOST_ASSERT(state.cur_ == tmp); |
| return false; |
| } |
| |
| Xpr xpr_; |
| bool not_; |
| bool pure_; // false if matching xpr_ could modify the sub-matches |
| std::size_t width_; |
| }; |
| |
| }}} |
| |
| #endif |