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97 lines
3.0 KiB
97 lines
3.0 KiB
3 years ago
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///////////////////////////////////////////////////////////////////////////////
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// keeper_matcher.hpp
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//
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// Copyright 2008 Eric Niebler. Distributed under the Boost
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// Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_XPRESSIVE_DETAIL_CORE_MATCHER_KEEPER_MATCHER_HPP_EAN_10_04_2005
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#define BOOST_XPRESSIVE_DETAIL_CORE_MATCHER_KEEPER_MATCHER_HPP_EAN_10_04_2005
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// MS compatible compilers support #pragma once
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#if defined(_MSC_VER)
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# pragma once
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#endif
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#include <boost/mpl/bool.hpp>
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#include <boost/xpressive/detail/detail_fwd.hpp>
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#include <boost/xpressive/detail/core/quant_style.hpp>
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#include <boost/xpressive/detail/core/state.hpp>
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namespace boost { namespace xpressive { namespace detail
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{
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///////////////////////////////////////////////////////////////////////////////
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// keeper_matcher
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// Xpr can be either a static_xpression, or a shared_matchable
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template<typename Xpr>
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struct keeper_matcher
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: quant_style<quant_variable_width, unknown_width::value, Xpr::pure>
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{
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keeper_matcher(Xpr const &xpr, bool pure = Xpr::pure)
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: xpr_(xpr)
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, pure_(pure)
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{
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}
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template<typename BidiIter, typename Next>
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bool match(match_state<BidiIter> &state, Next const &next) const
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{
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return Xpr::pure || this->pure_
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? this->match_(state, next, mpl::true_())
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: this->match_(state, next, mpl::false_());
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}
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template<typename BidiIter, typename Next>
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bool match_(match_state<BidiIter> &state, Next const &next, mpl::true_) const
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{
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BidiIter const tmp = state.cur_;
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// matching xpr is guaranteed to not produce side-effects, don't bother saving state
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if(!this->xpr_.match(state))
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{
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return false;
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}
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else if(next.match(state))
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{
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return true;
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}
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state.cur_ = tmp;
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return false;
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}
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template<typename BidiIter, typename Next>
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bool match_(match_state<BidiIter> &state, Next const &next, mpl::false_) const
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{
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BidiIter const tmp = state.cur_;
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// matching xpr could produce side-effects, save state
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memento<BidiIter> mem = save_sub_matches(state);
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if(!this->xpr_.match(state))
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{
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restore_action_queue(mem, state);
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reclaim_sub_matches(mem, state, false);
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return false;
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}
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restore_action_queue(mem, state);
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if(next.match(state))
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{
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reclaim_sub_matches(mem, state, true);
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return true;
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}
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restore_sub_matches(mem, state);
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state.cur_ = tmp;
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return false;
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}
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Xpr xpr_;
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bool pure_; // false if matching xpr_ could modify the sub-matches
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};
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}}}
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#endif
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