520 lines
17 KiB
C++
520 lines
17 KiB
C++
// class template regex -*- C++ -*-
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// Copyright (C) 2013-2017 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/**
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* @file bits/regex_executor.tcc
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* This is an internal header file, included by other library headers.
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* Do not attempt to use it directly. @headername{regex}
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*/
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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namespace __detail
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_search()
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{
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if (_M_search_from_first())
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return true;
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if (_M_flags & regex_constants::match_continuous)
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return false;
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_M_flags |= regex_constants::match_prev_avail;
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while (_M_begin != _M_end)
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{
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++_M_begin;
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if (_M_search_from_first())
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return true;
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}
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return false;
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}
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// The _M_main function operates in different modes, DFS mode or BFS mode,
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// indicated by template parameter __dfs_mode, and dispatches to one of the
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// _M_main_dispatch overloads.
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//
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// ------------------------------------------------------------
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//
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// DFS mode:
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//
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// It applies a Depth-First-Search (aka backtracking) on given NFA and input
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// string.
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// At the very beginning the executor stands in the start state, then it
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// tries every possible state transition in current state recursively. Some
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// state transitions consume input string, say, a single-char-matcher or a
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// back-reference matcher; some don't, like assertion or other anchor nodes.
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// When the input is exhausted and/or the current state is an accepting
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// state, the whole executor returns true.
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//
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// TODO: This approach is exponentially slow for certain input.
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// Try to compile the NFA to a DFA.
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//
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// Time complexity: \Omega(match_length), O(2^(_M_nfa.size()))
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// Space complexity: \theta(match_results.size() + match_length)
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//
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_main_dispatch(_Match_mode __match_mode, __dfs)
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{
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_M_has_sol = false;
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*_M_states._M_get_sol_pos() = _BiIter();
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_M_cur_results = _M_results;
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_M_dfs(__match_mode, _M_states._M_start);
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return _M_has_sol;
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}
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// ------------------------------------------------------------
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//
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// BFS mode:
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//
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// Russ Cox's article (http://swtch.com/~rsc/regexp/regexp1.html)
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// explained this algorithm clearly.
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//
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// It first computes epsilon closure (states that can be achieved without
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// consuming characters) for every state that's still matching,
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// using the same DFS algorithm, but doesn't re-enter states (using
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// _M_states._M_visited to check), nor follow _S_opcode_match.
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//
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// Then apply DFS using every _S_opcode_match (in _M_states._M_match_queue)
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// as the start state.
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//
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// It significantly reduces potential duplicate states, so has a better
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// upper bound; but it requires more overhead.
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//
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// Time complexity: \Omega(match_length * match_results.size())
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// O(match_length * _M_nfa.size() * match_results.size())
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// Space complexity: \Omega(_M_nfa.size() + match_results.size())
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// O(_M_nfa.size() * match_results.size())
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_main_dispatch(_Match_mode __match_mode, __bfs)
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{
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_M_states._M_queue(_M_states._M_start, _M_results);
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bool __ret = false;
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while (1)
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{
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_M_has_sol = false;
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if (_M_states._M_match_queue.empty())
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break;
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std::fill_n(_M_states._M_visited_states.get(), _M_nfa.size(), false);
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auto __old_queue = std::move(_M_states._M_match_queue);
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for (auto& __task : __old_queue)
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{
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_M_cur_results = std::move(__task.second);
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_M_dfs(__match_mode, __task.first);
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}
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if (__match_mode == _Match_mode::_Prefix)
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__ret |= _M_has_sol;
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if (_M_current == _M_end)
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break;
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++_M_current;
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}
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if (__match_mode == _Match_mode::_Exact)
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__ret = _M_has_sol;
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_M_states._M_match_queue.clear();
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return __ret;
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}
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// Return whether now match the given sub-NFA.
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_lookahead(_StateIdT __next)
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{
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// Backreferences may refer to captured content.
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// We may want to make this faster by not copying,
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// but let's not be clever prematurely.
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_ResultsVec __what(_M_cur_results);
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_Executor __sub(_M_current, _M_end, __what, _M_re, _M_flags);
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__sub._M_states._M_start = __next;
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if (__sub._M_search_from_first())
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{
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for (size_t __i = 0; __i < __what.size(); __i++)
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if (__what[__i].matched)
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_M_cur_results[__i] = __what[__i];
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return true;
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}
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return false;
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}
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// __rep_count records how many times (__rep_count.second)
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// this node is visited under certain input iterator
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// (__rep_count.first). This prevent the executor from entering
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// infinite loop by refusing to continue when it's already been
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// visited more than twice. It's `twice` instead of `once` because
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// we need to spare one more time for potential group capture.
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_rep_once_more(_Match_mode __match_mode, _StateIdT __i)
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{
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const auto& __state = _M_nfa[__i];
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auto& __rep_count = _M_rep_count[__i];
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if (__rep_count.second == 0 || __rep_count.first != _M_current)
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{
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auto __back = __rep_count;
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__rep_count.first = _M_current;
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__rep_count.second = 1;
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_M_dfs(__match_mode, __state._M_alt);
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__rep_count = __back;
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}
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else
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{
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if (__rep_count.second < 2)
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{
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__rep_count.second++;
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_M_dfs(__match_mode, __state._M_alt);
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__rep_count.second--;
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}
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}
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};
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// _M_alt branch is "match once more", while _M_next is "get me out
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// of this quantifier". Executing _M_next first or _M_alt first don't
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// mean the same thing, and we need to choose the correct order under
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// given greedy mode.
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_handle_repeat(_Match_mode __match_mode, _StateIdT __i)
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{
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const auto& __state = _M_nfa[__i];
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// Greedy.
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if (!__state._M_neg)
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{
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_M_rep_once_more(__match_mode, __i);
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// If it's DFS executor and already accepted, we're done.
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if (!__dfs_mode || !_M_has_sol)
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_M_dfs(__match_mode, __state._M_next);
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}
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else // Non-greedy mode
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{
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if (__dfs_mode)
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{
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// vice-versa.
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_M_dfs(__match_mode, __state._M_next);
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if (!_M_has_sol)
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_M_rep_once_more(__match_mode, __i);
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}
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else
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{
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// DON'T attempt anything, because there's already another
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// state with higher priority accepted. This state cannot
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// be better by attempting its next node.
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if (!_M_has_sol)
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{
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_M_dfs(__match_mode, __state._M_next);
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// DON'T attempt anything if it's already accepted. An
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// accepted state *must* be better than a solution that
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// matches a non-greedy quantifier one more time.
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if (!_M_has_sol)
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_M_rep_once_more(__match_mode, __i);
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}
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}
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}
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}
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_handle_subexpr_begin(_Match_mode __match_mode, _StateIdT __i)
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{
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const auto& __state = _M_nfa[__i];
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auto& __res = _M_cur_results[__state._M_subexpr];
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auto __back = __res.first;
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__res.first = _M_current;
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_M_dfs(__match_mode, __state._M_next);
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__res.first = __back;
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}
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_handle_subexpr_end(_Match_mode __match_mode, _StateIdT __i)
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{
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const auto& __state = _M_nfa[__i];
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auto& __res = _M_cur_results[__state._M_subexpr];
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auto __back = __res;
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__res.second = _M_current;
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__res.matched = true;
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_M_dfs(__match_mode, __state._M_next);
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__res = __back;
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}
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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inline void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_handle_line_begin_assertion(_Match_mode __match_mode, _StateIdT __i)
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{
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const auto& __state = _M_nfa[__i];
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if (_M_at_begin())
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_M_dfs(__match_mode, __state._M_next);
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}
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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inline void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_handle_line_end_assertion(_Match_mode __match_mode, _StateIdT __i)
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{
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const auto& __state = _M_nfa[__i];
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if (_M_at_end())
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_M_dfs(__match_mode, __state._M_next);
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}
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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inline void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_handle_word_boundary(_Match_mode __match_mode, _StateIdT __i)
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{
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const auto& __state = _M_nfa[__i];
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if (_M_word_boundary() == !__state._M_neg)
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_M_dfs(__match_mode, __state._M_next);
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}
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// Here __state._M_alt offers a single start node for a sub-NFA.
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// We recursively invoke our algorithm to match the sub-NFA.
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_handle_subexpr_lookahead(_Match_mode __match_mode, _StateIdT __i)
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{
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const auto& __state = _M_nfa[__i];
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if (_M_lookahead(__state._M_alt) == !__state._M_neg)
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_M_dfs(__match_mode, __state._M_next);
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}
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_handle_match(_Match_mode __match_mode, _StateIdT __i)
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{
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const auto& __state = _M_nfa[__i];
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if (_M_current == _M_end)
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return;
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if (__dfs_mode)
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{
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if (__state._M_matches(*_M_current))
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{
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++_M_current;
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_M_dfs(__match_mode, __state._M_next);
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--_M_current;
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}
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}
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else
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if (__state._M_matches(*_M_current))
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_M_states._M_queue(__state._M_next, _M_cur_results);
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}
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// First fetch the matched result from _M_cur_results as __submatch;
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// then compare it with
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// (_M_current, _M_current + (__submatch.second - __submatch.first)).
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// If matched, keep going; else just return and try another state.
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_handle_backref(_Match_mode __match_mode, _StateIdT __i)
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{
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__glibcxx_assert(__dfs_mode);
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const auto& __state = _M_nfa[__i];
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auto& __submatch = _M_cur_results[__state._M_backref_index];
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if (!__submatch.matched)
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return;
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auto __last = _M_current;
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for (auto __tmp = __submatch.first;
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__last != _M_end && __tmp != __submatch.second;
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++__tmp)
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++__last;
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if (_M_re._M_automaton->_M_traits.transform(__submatch.first,
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__submatch.second)
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== _M_re._M_automaton->_M_traits.transform(_M_current, __last))
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{
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if (__last != _M_current)
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{
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auto __backup = _M_current;
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_M_current = __last;
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_M_dfs(__match_mode, __state._M_next);
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_M_current = __backup;
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}
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else
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_M_dfs(__match_mode, __state._M_next);
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}
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}
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_handle_accept(_Match_mode __match_mode, _StateIdT __i)
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{
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if (__dfs_mode)
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{
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__glibcxx_assert(!_M_has_sol);
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if (__match_mode == _Match_mode::_Exact)
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_M_has_sol = _M_current == _M_end;
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else
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_M_has_sol = true;
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if (_M_current == _M_begin
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&& (_M_flags & regex_constants::match_not_null))
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_M_has_sol = false;
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if (_M_has_sol)
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{
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if (_M_nfa._M_flags & regex_constants::ECMAScript)
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_M_results = _M_cur_results;
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else // POSIX
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{
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__glibcxx_assert(_M_states._M_get_sol_pos());
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// Here's POSIX's logic: match the longest one. However
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// we never know which one (lhs or rhs of "|") is longer
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// unless we try both of them and compare the results.
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// The member variable _M_sol_pos records the end
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// position of the last successful match. It's better
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// to be larger, because POSIX regex is always greedy.
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// TODO: This could be slow.
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if (*_M_states._M_get_sol_pos() == _BiIter()
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|| std::distance(_M_begin,
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*_M_states._M_get_sol_pos())
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< std::distance(_M_begin, _M_current))
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{
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*_M_states._M_get_sol_pos() = _M_current;
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_M_results = _M_cur_results;
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}
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}
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}
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}
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else
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{
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if (_M_current == _M_begin
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&& (_M_flags & regex_constants::match_not_null))
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return;
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if (__match_mode == _Match_mode::_Prefix || _M_current == _M_end)
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if (!_M_has_sol)
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{
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_M_has_sol = true;
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_M_results = _M_cur_results;
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}
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}
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}
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_handle_alternative(_Match_mode __match_mode, _StateIdT __i)
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{
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const auto& __state = _M_nfa[__i];
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if (_M_nfa._M_flags & regex_constants::ECMAScript)
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{
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// TODO: Fix BFS support. It is wrong.
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_M_dfs(__match_mode, __state._M_alt);
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// Pick lhs if it matches. Only try rhs if it doesn't.
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if (!_M_has_sol)
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_M_dfs(__match_mode, __state._M_next);
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}
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else
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{
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// Try both and compare the result.
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// See "case _S_opcode_accept:" handling above.
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_M_dfs(__match_mode, __state._M_alt);
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auto __has_sol = _M_has_sol;
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_M_has_sol = false;
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_M_dfs(__match_mode, __state._M_next);
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_M_has_sol |= __has_sol;
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}
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}
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template<typename _BiIter, typename _Alloc, typename _TraitsT,
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bool __dfs_mode>
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void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
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_M_dfs(_Match_mode __match_mode, _StateIdT __i)
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{
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if (_M_states._M_visited(__i))
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return;
|
|
|
|
switch (_M_nfa[__i]._M_opcode())
|
|
{
|
|
case _S_opcode_repeat:
|
|
_M_handle_repeat(__match_mode, __i); break;
|
|
case _S_opcode_subexpr_begin:
|
|
_M_handle_subexpr_begin(__match_mode, __i); break;
|
|
case _S_opcode_subexpr_end:
|
|
_M_handle_subexpr_end(__match_mode, __i); break;
|
|
case _S_opcode_line_begin_assertion:
|
|
_M_handle_line_begin_assertion(__match_mode, __i); break;
|
|
case _S_opcode_line_end_assertion:
|
|
_M_handle_line_end_assertion(__match_mode, __i); break;
|
|
case _S_opcode_word_boundary:
|
|
_M_handle_word_boundary(__match_mode, __i); break;
|
|
case _S_opcode_subexpr_lookahead:
|
|
_M_handle_subexpr_lookahead(__match_mode, __i); break;
|
|
case _S_opcode_match:
|
|
_M_handle_match(__match_mode, __i); break;
|
|
case _S_opcode_backref:
|
|
_M_handle_backref(__match_mode, __i); break;
|
|
case _S_opcode_accept:
|
|
_M_handle_accept(__match_mode, __i); break;
|
|
case _S_opcode_alternative:
|
|
_M_handle_alternative(__match_mode, __i); break;
|
|
default:
|
|
__glibcxx_assert(false);
|
|
}
|
|
}
|
|
|
|
// Return whether now is at some word boundary.
|
|
template<typename _BiIter, typename _Alloc, typename _TraitsT,
|
|
bool __dfs_mode>
|
|
bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
|
|
_M_word_boundary() const
|
|
{
|
|
if (_M_current == _M_begin && (_M_flags & regex_constants::match_not_bow))
|
|
return false;
|
|
if (_M_current == _M_end && (_M_flags & regex_constants::match_not_eow))
|
|
return false;
|
|
|
|
bool __left_is_word = false;
|
|
if (_M_current != _M_begin
|
|
|| (_M_flags & regex_constants::match_prev_avail))
|
|
{
|
|
auto __prev = _M_current;
|
|
if (_M_is_word(*std::prev(__prev)))
|
|
__left_is_word = true;
|
|
}
|
|
bool __right_is_word =
|
|
_M_current != _M_end && _M_is_word(*_M_current);
|
|
|
|
return __left_is_word != __right_is_word;
|
|
}
|
|
|
|
_GLIBCXX_END_NAMESPACE_VERSION
|
|
} // namespace __detail
|
|
} // namespace
|