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// class template regex -*- C++ -*- |
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|
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// Copyright (C) 2013-2021 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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|
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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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|
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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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|
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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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/** |
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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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|
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namespace std _GLIBCXX_VISIBILITY(default) |
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{ |
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_GLIBCXX_BEGIN_NAMESPACE_VERSION |
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|
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namespace __detail |
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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_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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|
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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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// |
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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template<typename _BiIter, typename _TraitsT> |
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struct _Backref_matcher |
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{ |
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_Backref_matcher(bool __icase, const _TraitsT& __traits) |
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: _M_traits(__traits) { } |
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|
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bool |
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_M_apply(_BiIter __expected_begin, |
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_BiIter __expected_end, _BiIter __actual_begin, |
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_BiIter __actual_end) |
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{ |
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return _M_traits.transform(__expected_begin, __expected_end) |
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== _M_traits.transform(__actual_begin, __actual_end); |
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} |
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|
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const _TraitsT& _M_traits; |
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}; |
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|
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template<typename _BiIter, typename _CharT> |
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struct _Backref_matcher<_BiIter, std::regex_traits<_CharT>> |
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{ |
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using _TraitsT = std::regex_traits<_CharT>; |
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_Backref_matcher(bool __icase, const _TraitsT& __traits) |
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: _M_icase(__icase), _M_traits(__traits) { } |
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|
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bool |
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_M_apply(_BiIter __expected_begin, |
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_BiIter __expected_end, _BiIter __actual_begin, |
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_BiIter __actual_end) |
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{ |
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if (!_M_icase) |
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return _GLIBCXX_STD_A::__equal4(__expected_begin, __expected_end, |
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__actual_begin, __actual_end); |
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typedef std::ctype<_CharT> __ctype_type; |
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const auto& __fctyp = use_facet<__ctype_type>(_M_traits.getloc()); |
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return _GLIBCXX_STD_A::__equal4(__expected_begin, __expected_end, |
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__actual_begin, __actual_end, |
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[this, &__fctyp](_CharT __lhs, _CharT __rhs) |
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{ |
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return __fctyp.tolower(__lhs) |
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== __fctyp.tolower(__rhs); |
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}); |
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} |
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|
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bool _M_icase; |
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const _TraitsT& _M_traits; |
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}; |
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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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|
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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 (_Backref_matcher<_BiIter, _TraitsT>( |
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_M_re.flags() & regex_constants::icase, |
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_M_re._M_automaton->_M_traits)._M_apply( |
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__submatch.first, __submatch.second, _M_current, __last)) |
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{ |
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if (__last != _M_current) |
| 412 |
{ |
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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); |
| 420 |
} |
| 421 |
} |
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|
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template<typename _BiIter, typename _Alloc, typename _TraitsT, |
| 424 |
bool __dfs_mode> |
| 425 |
void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
| 426 |
_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); |
| 431 |
if (__match_mode == _Match_mode::_Exact) |
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_M_has_sol = _M_current == _M_end; |
| 433 |
else |
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_M_has_sol = true; |
| 435 |
if (_M_current == _M_begin |
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&& (_M_flags & regex_constants::match_not_null)) |
| 437 |
_M_has_sol = false; |
| 438 |
if (_M_has_sol) |
| 439 |
{ |
| 440 |
if (_M_nfa._M_flags & regex_constants::ECMAScript) |
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_M_results = _M_cur_results; |
| 442 |
else // POSIX |
| 443 |
{ |
| 444 |
__glibcxx_assert(_M_states._M_get_sol_pos()); |
| 445 |
// Here's POSIX's logic: match the longest one. However |
| 446 |
// we never know which one (lhs or rhs of "|") is longer |
| 447 |
// unless we try both of them and compare the results. |
| 448 |
// The member variable _M_sol_pos records the end |
| 449 |
// position of the last successful match. It's better |
| 450 |
// to be larger, because POSIX regex is always greedy. |
| 451 |
// TODO: This could be slow. |
| 452 |
if (*_M_states._M_get_sol_pos() == _BiIter() |
| 453 |
|| std::distance(_M_begin, |
| 454 |
*_M_states._M_get_sol_pos()) |
| 455 |
< std::distance(_M_begin, _M_current)) |
| 456 |
{ |
| 457 |
*_M_states._M_get_sol_pos() = _M_current; |
| 458 |
_M_results = _M_cur_results; |
| 459 |
} |
| 460 |
} |
| 461 |
} |
| 462 |
} |
| 463 |
else |
| 464 |
{ |
| 465 |
if (_M_current == _M_begin |
| 466 |
&& (_M_flags & regex_constants::match_not_null)) |
| 467 |
return; |
| 468 |
if (__match_mode == _Match_mode::_Prefix || _M_current == _M_end) |
| 469 |
if (!_M_has_sol) |
| 470 |
{ |
| 471 |
_M_has_sol = true; |
| 472 |
_M_results = _M_cur_results; |
| 473 |
} |
| 474 |
} |
| 475 |
} |
| 476 |
|
| 477 |
template<typename _BiIter, typename _Alloc, typename _TraitsT, |
| 478 |
bool __dfs_mode> |
| 479 |
void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
| 480 |
_M_handle_alternative(_Match_mode __match_mode, _StateIdT __i) |
| 481 |
{ |
| 482 |
const auto& __state = _M_nfa[__i]; |
| 483 |
|
| 484 |
if (_M_nfa._M_flags & regex_constants::ECMAScript) |
| 485 |
{ |
| 486 |
// TODO: Fix BFS support. It is wrong. |
| 487 |
_M_dfs(__match_mode, __state._M_alt); |
| 488 |
// Pick lhs if it matches. Only try rhs if it doesn't. |
| 489 |
if (!_M_has_sol) |
| 490 |
_M_dfs(__match_mode, __state._M_next); |
| 491 |
} |
| 492 |
else |
| 493 |
{ |
| 494 |
// Try both and compare the result. |
| 495 |
// See "case _S_opcode_accept:" handling above. |
| 496 |
_M_dfs(__match_mode, __state._M_alt); |
| 497 |
auto __has_sol = _M_has_sol; |
| 498 |
_M_has_sol = false; |
| 499 |
_M_dfs(__match_mode, __state._M_next); |
| 500 |
_M_has_sol |= __has_sol; |
| 501 |
} |
| 502 |
} |
| 503 |
|
| 504 |
template<typename _BiIter, typename _Alloc, typename _TraitsT, |
| 505 |
bool __dfs_mode> |
| 506 |
void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
| 507 |
_M_dfs(_Match_mode __match_mode, _StateIdT __i) |
| 508 |
{ |
| 509 |
if (_M_states._M_visited(__i)) |
| 510 |
return; |
| 511 |
|
| 512 |
switch (_M_nfa[__i]._M_opcode()) |
| 513 |
{ |
| 514 |
case _S_opcode_repeat: |
| 515 |
_M_handle_repeat(__match_mode, __i); break; |
| 516 |
case _S_opcode_subexpr_begin: |
| 517 |
_M_handle_subexpr_begin(__match_mode, __i); break; |
| 518 |
case _S_opcode_subexpr_end: |
| 519 |
_M_handle_subexpr_end(__match_mode, __i); break; |
| 520 |
case _S_opcode_line_begin_assertion: |
| 521 |
_M_handle_line_begin_assertion(__match_mode, __i); break; |
| 522 |
case _S_opcode_line_end_assertion: |
| 523 |
_M_handle_line_end_assertion(__match_mode, __i); break; |
| 524 |
case _S_opcode_word_boundary: |
| 525 |
_M_handle_word_boundary(__match_mode, __i); break; |
| 526 |
case _S_opcode_subexpr_lookahead: |
| 527 |
_M_handle_subexpr_lookahead(__match_mode, __i); break; |
| 528 |
case _S_opcode_match: |
| 529 |
_M_handle_match(__match_mode, __i); break; |
| 530 |
case _S_opcode_backref: |
| 531 |
_M_handle_backref(__match_mode, __i); break; |
| 532 |
case _S_opcode_accept: |
| 533 |
_M_handle_accept(__match_mode, __i); break; |
| 534 |
case _S_opcode_alternative: |
| 535 |
_M_handle_alternative(__match_mode, __i); break; |
| 536 |
default: |
| 537 |
__glibcxx_assert(false); |
| 538 |
} |
| 539 |
} |
| 540 |
|
| 541 |
// Return whether now is at some word boundary. |
| 542 |
template<typename _BiIter, typename _Alloc, typename _TraitsT, |
| 543 |
bool __dfs_mode> |
| 544 |
bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
| 545 |
_M_word_boundary() const |
| 546 |
{ |
| 547 |
if (_M_current == _M_begin && (_M_flags & regex_constants::match_not_bow)) |
| 548 |
return false; |
| 549 |
if (_M_current == _M_end && (_M_flags & regex_constants::match_not_eow)) |
| 550 |
return false; |
| 551 |
|
| 552 |
bool __left_is_word = false; |
| 553 |
if (_M_current != _M_begin |
| 554 |
|| (_M_flags & regex_constants::match_prev_avail)) |
| 555 |
{ |
| 556 |
auto __prev = _M_current; |
| 557 |
if (_M_is_word(*std::prev(__prev))) |
| 558 |
__left_is_word = true; |
| 559 |
} |
| 560 |
bool __right_is_word = |
| 561 |
_M_current != _M_end && _M_is_word(*_M_current); |
| 562 |
|
| 563 |
return __left_is_word != __right_is_word; |
| 564 |
} |
| 565 |
} // namespace __detail |
| 566 |
|
| 567 |
_GLIBCXX_END_NAMESPACE_VERSION |
| 568 |
} // namespace |
