| // class template regex -*- C++ -*- |
| |
| // Copyright (C) 2013-2014 Free Software Foundation, Inc. |
| // |
| // This file is part of the GNU ISO C++ Library. This library is free |
| // software; you can redistribute it and/or modify it under the |
| // terms of the GNU General Public License as published by the |
| // Free Software Foundation; either version 3, or (at your option) |
| // any later version. |
| |
| // This library is distributed in the hope that it will be useful, |
| // but WITHOUT ANY WARRANTY; without even the implied warranty of |
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| // GNU General Public License for more details. |
| |
| // Under Section 7 of GPL version 3, you are granted additional |
| // permissions described in the GCC Runtime Library Exception, version |
| // 3.1, as published by the Free Software Foundation. |
| |
| // You should have received a copy of the GNU General Public License and |
| // a copy of the GCC Runtime Library Exception along with this program; |
| // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
| // <http://www.gnu.org/licenses/>. |
| |
| /** |
| * @file bits/regex_executor.tcc |
| * This is an internal header file, included by other library headers. |
| * Do not attempt to use it directly. @headername{regex} |
| */ |
| |
| namespace std _GLIBCXX_VISIBILITY(default) |
| { |
| namespace __detail |
| { |
| _GLIBCXX_BEGIN_NAMESPACE_VERSION |
| |
| template<typename _BiIter, typename _Alloc, typename _TraitsT, |
| bool __dfs_mode> |
| bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
| _M_search() |
| { |
| if (_M_flags & regex_constants::match_continuous) |
| return _M_search_from_first(); |
| auto __cur = _M_begin; |
| do |
| { |
| _M_current = __cur; |
| if (_M_main<false>()) |
| return true; |
| } |
| // Continue when __cur == _M_end |
| while (__cur++ != _M_end); |
| return false; |
| } |
| |
| // This function operates in different modes, DFS mode or BFS mode, indicated |
| // by template parameter __dfs_mode. See _M_main for details. |
| // |
| // ------------------------------------------------------------ |
| // |
| // DFS mode: |
| // |
| // It applies a Depth-First-Search (aka backtracking) on given NFA and input |
| // string. |
| // At the very beginning the executor stands in the start state, then it tries |
| // every possible state transition in current state recursively. Some state |
| // transitions consume input string, say, a single-char-matcher or a |
| // back-reference matcher; some don't, like assertion or other anchor nodes. |
| // When the input is exhausted and/or the current state is an accepting state, |
| // the whole executor returns true. |
| // |
| // TODO: This approach is exponentially slow for certain input. |
| // Try to compile the NFA to a DFA. |
| // |
| // Time complexity: \Omega(match_length), O(2^(_M_nfa.size())) |
| // Space complexity: \theta(match_results.size() + match_length) |
| // |
| // ------------------------------------------------------------ |
| // |
| // BFS mode: |
| // |
| // Russ Cox's article (http://swtch.com/~rsc/regexp/regexp1.html) |
| // explained this algorithm clearly. |
| // |
| // It first computes epsilon closure (states that can be achieved without |
| // consuming characters) for every state that's still matching, |
| // using the same DFS algorithm, but doesn't re-enter states (find a true in |
| // _M_visited), nor follows _S_opcode_match. |
| // |
| // Then apply DFS using every _S_opcode_match (in _M_match_queue) as the start |
| // state. |
| // |
| // It significantly reduces potential duplicate states, so has a better |
| // upper bound; but it requires more overhead. |
| // |
| // Time complexity: \Omega(match_length * match_results.size()) |
| // O(match_length * _M_nfa.size() * match_results.size()) |
| // Space complexity: \Omega(_M_nfa.size() + match_results.size()) |
| // O(_M_nfa.size() * match_results.size()) |
| template<typename _BiIter, typename _Alloc, typename _TraitsT, |
| bool __dfs_mode> |
| template<bool __match_mode> |
| bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
| _M_main() |
| { |
| if (__dfs_mode) |
| { |
| _M_has_sol = false; |
| _M_cur_results = _M_results; |
| _M_dfs<__match_mode>(_M_start_state); |
| return _M_has_sol; |
| } |
| else |
| { |
| _M_match_queue->push_back(make_pair(_M_start_state, _M_results)); |
| bool __ret = false; |
| while (1) |
| { |
| _M_has_sol = false; |
| if (_M_match_queue->empty()) |
| break; |
| _M_visited->assign(_M_visited->size(), false); |
| auto __old_queue = std::move(*_M_match_queue); |
| for (auto& __task : __old_queue) |
| { |
| _M_cur_results = std::move(__task.second); |
| _M_dfs<__match_mode>(__task.first); |
| } |
| if (!__match_mode) |
| __ret |= _M_has_sol; |
| if (_M_current == _M_end) |
| break; |
| ++_M_current; |
| } |
| if (__match_mode) |
| __ret = _M_has_sol; |
| return __ret; |
| } |
| } |
| |
| // Return whether now match the given sub-NFA. |
| template<typename _BiIter, typename _Alloc, typename _TraitsT, |
| bool __dfs_mode> |
| bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
| _M_lookahead(_State<_TraitsT> __state) |
| { |
| _ResultsVec __what(_M_cur_results.size()); |
| auto __sub = std::unique_ptr<_Executor>(new _Executor(_M_current, |
| _M_end, |
| __what, |
| _M_re, |
| _M_flags)); |
| __sub->_M_start_state = __state._M_alt; |
| if (__sub->_M_search_from_first()) |
| { |
| for (size_t __i = 0; __i < __what.size(); __i++) |
| if (__what[__i].matched) |
| _M_cur_results[__i] = __what[__i]; |
| return true; |
| } |
| return false; |
| } |
| |
| // TODO: Use a function vector to dispatch, instead of using switch-case. |
| template<typename _BiIter, typename _Alloc, typename _TraitsT, |
| bool __dfs_mode> |
| template<bool __match_mode> |
| void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
| _M_dfs(_StateIdT __i) |
| { |
| if (!__dfs_mode) |
| { |
| if ((*_M_visited)[__i]) |
| return; |
| (*_M_visited)[__i] = true; |
| } |
| |
| const auto& __state = _M_nfa[__i]; |
| // Every change on _M_cur_results and _M_current will be rolled back after |
| // finishing the recursion step. |
| switch (__state._M_opcode) |
| { |
| // _M_alt branch is "match once more", while _M_next is "get me out |
| // of this quantifier". Executing _M_next first or _M_alt first don't |
| // mean the same thing, and we need to choose the correct order under |
| // given greedy mode. |
| case _S_opcode_alternative: |
| // Greedy. |
| if (!__state._M_neg) |
| { |
| // "Once more" is preferred in greedy mode. |
| _M_dfs<__match_mode>(__state._M_alt); |
| // If it's DFS executor and already accepted, we're done. |
| if (!__dfs_mode || !_M_has_sol) |
| _M_dfs<__match_mode>(__state._M_next); |
| } |
| else // Non-greedy mode |
| { |
| if (__dfs_mode) |
| { |
| // vice-versa. |
| _M_dfs<__match_mode>(__state._M_next); |
| if (!_M_has_sol) |
| _M_dfs<__match_mode>(__state._M_alt); |
| } |
| else |
| { |
| // DON'T attempt anything, because there's already another |
| // state with higher priority accepted. This state cannot be |
| // better by attempting its next node. |
| if (!_M_has_sol) |
| { |
| _M_dfs<__match_mode>(__state._M_next); |
| // DON'T attempt anything if it's already accepted. An |
| // accepted state *must* be better than a solution that |
| // matches a non-greedy quantifier one more time. |
| if (!_M_has_sol) |
| _M_dfs<__match_mode>(__state._M_alt); |
| } |
| } |
| } |
| break; |
| case _S_opcode_subexpr_begin: |
| // If there's nothing changed since last visit, do NOT continue. |
| // This prevents the executor from get into infinite loop when using |
| // "()*" to match "". |
| if (!_M_cur_results[__state._M_subexpr].matched |
| || _M_cur_results[__state._M_subexpr].first != _M_current) |
| { |
| auto& __res = _M_cur_results[__state._M_subexpr]; |
| auto __back = __res.first; |
| __res.first = _M_current; |
| _M_dfs<__match_mode>(__state._M_next); |
| __res.first = __back; |
| } |
| break; |
| case _S_opcode_subexpr_end: |
| if (_M_cur_results[__state._M_subexpr].second != _M_current |
| || _M_cur_results[__state._M_subexpr].matched != true) |
| { |
| auto& __res = _M_cur_results[__state._M_subexpr]; |
| auto __back = __res; |
| __res.second = _M_current; |
| __res.matched = true; |
| _M_dfs<__match_mode>(__state._M_next); |
| __res = __back; |
| } |
| else |
| _M_dfs<__match_mode>(__state._M_next); |
| break; |
| case _S_opcode_line_begin_assertion: |
| if (_M_at_begin()) |
| _M_dfs<__match_mode>(__state._M_next); |
| break; |
| case _S_opcode_line_end_assertion: |
| if (_M_at_end()) |
| _M_dfs<__match_mode>(__state._M_next); |
| break; |
| case _S_opcode_word_boundary: |
| if (_M_word_boundary(__state) == !__state._M_neg) |
| _M_dfs<__match_mode>(__state._M_next); |
| break; |
| // Here __state._M_alt offers a single start node for a sub-NFA. |
| // We recursively invoke our algorithm to match the sub-NFA. |
| case _S_opcode_subexpr_lookahead: |
| if (_M_lookahead(__state) == !__state._M_neg) |
| _M_dfs<__match_mode>(__state._M_next); |
| break; |
| case _S_opcode_match: |
| if (__dfs_mode) |
| { |
| if (_M_current != _M_end && __state._M_matches(*_M_current)) |
| { |
| ++_M_current; |
| _M_dfs<__match_mode>(__state._M_next); |
| --_M_current; |
| } |
| } |
| else |
| if (__state._M_matches(*_M_current)) |
| _M_match_queue->push_back(make_pair(__state._M_next, |
| _M_cur_results)); |
| break; |
| // First fetch the matched result from _M_cur_results as __submatch; |
| // then compare it with |
| // (_M_current, _M_current + (__submatch.second - __submatch.first)). |
| // If matched, keep going; else just return and try another state. |
| case _S_opcode_backref: |
| { |
| _GLIBCXX_DEBUG_ASSERT(__dfs_mode); |
| auto& __submatch = _M_cur_results[__state._M_backref_index]; |
| if (!__submatch.matched) |
| break; |
| auto __last = _M_current; |
| for (auto __tmp = __submatch.first; |
| __last != _M_end && __tmp != __submatch.second; |
| ++__tmp) |
| ++__last; |
| if (_M_re._M_traits.transform(__submatch.first, |
| __submatch.second) |
| == _M_re._M_traits.transform(_M_current, __last)) |
| { |
| if (__last != _M_current) |
| { |
| auto __backup = _M_current; |
| _M_current = __last; |
| _M_dfs<__match_mode>(__state._M_next); |
| _M_current = __backup; |
| } |
| else |
| _M_dfs<__match_mode>(__state._M_next); |
| } |
| } |
| break; |
| case _S_opcode_accept: |
| if (__dfs_mode) |
| { |
| _GLIBCXX_DEBUG_ASSERT(!_M_has_sol); |
| if (__match_mode) |
| _M_has_sol = _M_current == _M_end; |
| else |
| _M_has_sol = true; |
| if (_M_current == _M_begin |
| && (_M_flags & regex_constants::match_not_null)) |
| _M_has_sol = false; |
| if (_M_has_sol) |
| _M_results = _M_cur_results; |
| } |
| else |
| { |
| if (_M_current == _M_begin |
| && (_M_flags & regex_constants::match_not_null)) |
| break; |
| if (!__match_mode || _M_current == _M_end) |
| if (!_M_has_sol) |
| { |
| _M_has_sol = true; |
| _M_results = _M_cur_results; |
| } |
| } |
| break; |
| default: |
| _GLIBCXX_DEBUG_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(_State<_TraitsT> __state) const |
| { |
| // By definition. |
| bool __ans = false; |
| auto __pre = _M_current; |
| --__pre; |
| if (!(_M_at_begin() && _M_at_end())) |
| { |
| if (_M_at_begin()) |
| __ans = _M_is_word(*_M_current) |
| && !(_M_flags & regex_constants::match_not_bow); |
| else if (_M_at_end()) |
| __ans = _M_is_word(*__pre) |
| && !(_M_flags & regex_constants::match_not_eow); |
| else |
| __ans = _M_is_word(*_M_current) |
| != _M_is_word(*__pre); |
| } |
| return __ans; |
| } |
| |
| _GLIBCXX_END_NAMESPACE_VERSION |
| } // namespace __detail |
| } // namespace |