File Coverage

/usr/include/c++/5/bits/regex_executor.tcc
Criterion Covered Total %
statement 0 166 0.0
branch 0 232 0.0
condition n/a
subroutine n/a
pod n/a
total 0 398 0.0


line stmt bran cond sub pod time code
1             // class template regex -*- C++ -*-
2              
3             // Copyright (C) 2013-2015 Free Software Foundation, Inc.
4             //
5             // This file is part of the GNU ISO C++ Library. This library is free
6             // software; you can redistribute it and/or modify it under the
7             // terms of the GNU General Public License as published by the
8             // Free Software Foundation; either version 3, or (at your option)
9             // any later version.
10              
11             // This library is distributed in the hope that it will be useful,
12             // but WITHOUT ANY WARRANTY; without even the implied warranty of
13             // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14             // GNU General Public License for more details.
15              
16             // Under Section 7 of GPL version 3, you are granted additional
17             // permissions described in the GCC Runtime Library Exception, version
18             // 3.1, as published by the Free Software Foundation.
19              
20             // You should have received a copy of the GNU General Public License and
21             // a copy of the GCC Runtime Library Exception along with this program;
22             // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23             // .
24              
25             /**
26             * @file bits/regex_executor.tcc
27             * This is an internal header file, included by other library headers.
28             * Do not attempt to use it directly. @headername{regex}
29             */
30              
31             namespace std _GLIBCXX_VISIBILITY(default)
32             {
33             namespace __detail
34             {
35             _GLIBCXX_BEGIN_NAMESPACE_VERSION
36              
37             template
38             bool __dfs_mode>
39             bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
40             _M_search()
41             {
42             if (_M_search_from_first())
43             return true;
44             if (_M_flags & regex_constants::match_continuous)
45             return false;
46             _M_flags |= regex_constants::match_prev_avail;
47             while (_M_begin != _M_end)
48             {
49             ++_M_begin;
50             if (_M_search_from_first())
51             return true;
52             }
53             return false;
54             }
55              
56             // The _M_main function operates in different modes, DFS mode or BFS mode,
57             // indicated by template parameter __dfs_mode, and dispatches to one of the
58             // _M_main_dispatch overloads.
59             //
60             // ------------------------------------------------------------
61             //
62             // DFS mode:
63             //
64             // It applies a Depth-First-Search (aka backtracking) on given NFA and input
65             // string.
66             // At the very beginning the executor stands in the start state, then it
67             // tries every possible state transition in current state recursively. Some
68             // state transitions consume input string, say, a single-char-matcher or a
69             // back-reference matcher; some don't, like assertion or other anchor nodes.
70             // When the input is exhausted and/or the current state is an accepting
71             // state, the whole executor returns true.
72             //
73             // TODO: This approach is exponentially slow for certain input.
74             // Try to compile the NFA to a DFA.
75             //
76             // Time complexity: \Omega(match_length), O(2^(_M_nfa.size()))
77             // Space complexity: \theta(match_results.size() + match_length)
78             //
79             template
80             bool __dfs_mode>
81 0           bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
82             _M_main_dispatch(_Match_mode __match_mode, __dfs)
83             {
84 0           _M_has_sol = false;
85 0           *_M_states._M_get_sol_pos() = _BiIter();
86 0           _M_cur_results = _M_results;
87 0           _M_dfs(__match_mode, _M_states._M_start);
88 0           return _M_has_sol;
89             }
90              
91             // ------------------------------------------------------------
92             //
93             // BFS mode:
94             //
95             // Russ Cox's article (http://swtch.com/~rsc/regexp/regexp1.html)
96             // explained this algorithm clearly.
97             //
98             // It first computes epsilon closure (states that can be achieved without
99             // consuming characters) for every state that's still matching,
100             // using the same DFS algorithm, but doesn't re-enter states (using
101             // _M_states._M_visited to check), nor follow _S_opcode_match.
102             //
103             // Then apply DFS using every _S_opcode_match (in _M_states._M_match_queue)
104             // as the start state.
105             //
106             // It significantly reduces potential duplicate states, so has a better
107             // upper bound; but it requires more overhead.
108             //
109             // Time complexity: \Omega(match_length * match_results.size())
110             // O(match_length * _M_nfa.size() * match_results.size())
111             // Space complexity: \Omega(_M_nfa.size() + match_results.size())
112             // O(_M_nfa.size() * match_results.size())
113             template
114             bool __dfs_mode>
115 0           bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
116             _M_main_dispatch(_Match_mode __match_mode, __bfs)
117             {
118 0           _M_states._M_queue(_M_states._M_start, _M_results);
119 0           bool __ret = false;
120 0           while (1)
121             {
122 0           _M_has_sol = false;
123 0 0         if (_M_states._M_match_queue.empty())
124 0           break;
125 0 0         std::fill_n(_M_states._M_visited_states.get(), _M_nfa.size(), false);
126 0           auto __old_queue = std::move(_M_states._M_match_queue);
127 0 0         for (auto& __task : __old_queue)
128             {
129 0           _M_cur_results = std::move(__task.second);
130 0 0         _M_dfs(__match_mode, __task.first);
131             }
132 0 0         if (__match_mode == _Match_mode::_Prefix)
133 0           __ret |= _M_has_sol;
134 0 0         if (_M_current == _M_end)
135 0           break;
136 0 0         ++_M_current;
137             }
138 0 0         if (__match_mode == _Match_mode::_Exact)
139 0           __ret = _M_has_sol;
140 0           _M_states._M_match_queue.clear();
141 0           return __ret;
142             }
143              
144             // Return whether now match the given sub-NFA.
145             template
146             bool __dfs_mode>
147 0           bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
148             _M_lookahead(_State<_TraitsT> __state)
149             {
150             // Backreferences may refer to captured content.
151             // We may want to make this faster by not copying,
152             // but let's not be clever prematurely.
153 0 0         _ResultsVec __what(_M_cur_results);
    0          
154 0 0         _Executor __sub(_M_current, _M_end, __what, _M_re, _M_flags);
    0          
155 0           __sub._M_states._M_start = __state._M_alt;
156 0 0         if (__sub._M_search_from_first())
    0          
    0          
    0          
157             {
158 0 0         for (size_t __i = 0; __i < __what.size(); __i++)
    0          
159 0 0         if (__what[__i].matched)
    0          
160 0 0         _M_cur_results[__i] = __what[__i];
    0          
161 0           return true;
162             }
163 0           return false;
164             }
165              
166             // __rep_count records how many times (__rep_count.second)
167             // this node is visited under certain input iterator
168             // (__rep_count.first). This prevent the executor from entering
169             // infinite loop by refusing to continue when it's already been
170             // visited more than twice. It's `twice` instead of `once` because
171             // we need to spare one more time for potential group capture.
172             template
173             bool __dfs_mode>
174 0           void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
175             _M_rep_once_more(_Match_mode __match_mode, _StateIdT __i)
176             {
177 0           const auto& __state = _M_nfa[__i];
178 0           auto& __rep_count = _M_rep_count[__i];
179 0 0         if (__rep_count.second == 0 || __rep_count.first != _M_current)
    0          
    0          
    0          
180             {
181 0           auto __back = __rep_count;
182 0           __rep_count.first = _M_current;
183 0           __rep_count.second = 1;
184 0 0         _M_dfs(__match_mode, __state._M_alt);
    0          
185 0           __rep_count = __back;
186             }
187             else
188             {
189 0 0         if (__rep_count.second < 2)
    0          
190             {
191 0           __rep_count.second++;
192 0           _M_dfs(__match_mode, __state._M_alt);
193 0           __rep_count.second--;
194             }
195             }
196 0           };
197              
198             template
199             bool __dfs_mode>
200 0           void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
201             _M_dfs(_Match_mode __match_mode, _StateIdT __i)
202             {
203 0 0         if (_M_states._M_visited(__i))
    0          
204 0           return;
205              
206 0           const auto& __state = _M_nfa[__i];
207             // Every change on _M_cur_results and _M_current will be rolled back after
208             // finishing the recursion step.
209 0           switch (__state._M_opcode)
210             {
211             // _M_alt branch is "match once more", while _M_next is "get me out
212             // of this quantifier". Executing _M_next first or _M_alt first don't
213             // mean the same thing, and we need to choose the correct order under
214             // given greedy mode.
215             case _S_opcode_repeat:
216             {
217             // Greedy.
218 0 0         if (!__state._M_neg)
    0          
219             {
220 0           _M_rep_once_more(__match_mode, __i);
221             // If it's DFS executor and already accepted, we're done.
222 0 0         if (!__dfs_mode || !_M_has_sol)
223 0           _M_dfs(__match_mode, __state._M_next);
224             }
225             else // Non-greedy mode
226             {
227             if (__dfs_mode)
228             {
229             // vice-versa.
230 0           _M_dfs(__match_mode, __state._M_next);
231 0 0         if (!_M_has_sol)
232 0           _M_rep_once_more(__match_mode, __i);
233             }
234             else
235             {
236             // DON'T attempt anything, because there's already another
237             // state with higher priority accepted. This state cannot
238             // be better by attempting its next node.
239 0 0         if (!_M_has_sol)
240             {
241 0           _M_dfs(__match_mode, __state._M_next);
242             // DON'T attempt anything if it's already accepted. An
243             // accepted state *must* be better than a solution that
244             // matches a non-greedy quantifier one more time.
245 0 0         if (!_M_has_sol)
246 0           _M_rep_once_more(__match_mode, __i);
247             }
248             }
249             }
250             }
251 0           break;
252             case _S_opcode_subexpr_begin:
253             {
254 0           auto& __res = _M_cur_results[__state._M_subexpr];
255 0           auto __back = __res.first;
256 0           __res.first = _M_current;
257 0 0         _M_dfs(__match_mode, __state._M_next);
    0          
258 0           __res.first = __back;
259             }
260 0           break;
261             case _S_opcode_subexpr_end:
262             {
263 0           auto& __res = _M_cur_results[__state._M_subexpr];
264 0           auto __back = __res;
265 0           __res.second = _M_current;
266 0           __res.matched = true;
267 0 0         _M_dfs(__match_mode, __state._M_next);
    0          
268 0 0         __res = __back;
    0          
269             }
270 0           break;
271             case _S_opcode_line_begin_assertion:
272 0 0         if (_M_at_begin())
    0          
273 0           _M_dfs(__match_mode, __state._M_next);
274 0           break;
275             case _S_opcode_line_end_assertion:
276 0 0         if (_M_at_end())
    0          
277 0           _M_dfs(__match_mode, __state._M_next);
278 0           break;
279             case _S_opcode_word_boundary:
280 0 0         if (_M_word_boundary() == !__state._M_neg)
    0          
281 0           _M_dfs(__match_mode, __state._M_next);
282 0           break;
283             // Here __state._M_alt offers a single start node for a sub-NFA.
284             // We recursively invoke our algorithm to match the sub-NFA.
285             case _S_opcode_subexpr_lookahead:
286 0 0         if (_M_lookahead(__state) == !__state._M_neg)
    0          
    0          
    0          
287 0           _M_dfs(__match_mode, __state._M_next);
288 0           break;
289             case _S_opcode_match:
290 0 0         if (_M_current == _M_end)
    0          
291 0           break;
292             if (__dfs_mode)
293             {
294 0 0         if (__state._M_matches(*_M_current))
295             {
296 0           ++_M_current;
297 0           _M_dfs(__match_mode, __state._M_next);
298 0           --_M_current;
299             }
300             }
301             else
302 0 0         if (__state._M_matches(*_M_current))
303 0           _M_states._M_queue(__state._M_next, _M_cur_results);
304 0           break;
305             // First fetch the matched result from _M_cur_results as __submatch;
306             // then compare it with
307             // (_M_current, _M_current + (__submatch.second - __submatch.first)).
308             // If matched, keep going; else just return and try another state.
309             case _S_opcode_backref:
310             {
311             _GLIBCXX_DEBUG_ASSERT(__dfs_mode);
312 0           auto& __submatch = _M_cur_results[__state._M_backref_index];
313 0           if (!__submatch.matched)
314 0           break;
315 0           auto __last = _M_current;
316 0 0         for (auto __tmp = __submatch.first;
    0          
317 0           __last != _M_end && __tmp != __submatch.second;
318             ++__tmp)
319 0           ++__last;
320 0 0         if (_M_re._M_automaton->_M_traits.transform(__submatch.first,
    0          
321             __submatch.second)
322 0 0         == _M_re._M_automaton->_M_traits.transform(_M_current, __last))
    0          
    0          
    0          
323             {
324 0 0         if (__last != _M_current)
    0          
325             {
326 0           auto __backup = _M_current;
327 0           _M_current = __last;
328 0 0         _M_dfs(__match_mode, __state._M_next);
    0          
329 0           _M_current = __backup;
330             }
331             else
332 0 0         _M_dfs(__match_mode, __state._M_next);
    0          
333             }
334             }
335 0           break;
336             case _S_opcode_accept:
337             if (__dfs_mode)
338             {
339             _GLIBCXX_DEBUG_ASSERT(!_M_has_sol);
340 0 0         if (__match_mode == _Match_mode::_Exact)
341 0           _M_has_sol = _M_current == _M_end;
342             else
343 0           _M_has_sol = true;
344 0 0         if (_M_current == _M_begin
345 0           && (_M_flags & regex_constants::match_not_null))
346 0           _M_has_sol = false;
347 0 0         if (_M_has_sol)
348             {
349 0 0         if (_M_nfa._M_flags & regex_constants::ECMAScript)
350 0           _M_results = _M_cur_results;
351             else // POSIX
352             {
353             _GLIBCXX_DEBUG_ASSERT(_M_states._M_get_sol_pos());
354             // Here's POSIX's logic: match the longest one. However
355             // we never know which one (lhs or rhs of "|") is longer
356             // unless we try both of them and compare the results.
357             // The member variable _M_sol_pos records the end
358             // position of the last successful match. It's better
359             // to be larger, because POSIX regex is always greedy.
360             // TODO: This could be slow.
361 0 0         if (*_M_states._M_get_sol_pos() == _BiIter()
    0          
    0          
    0          
    0          
362 0 0         || std::distance(_M_begin,
363 0           *_M_states._M_get_sol_pos())
364 0 0         < std::distance(_M_begin, _M_current))
365             {
366 0           *_M_states._M_get_sol_pos() = _M_current;
367 0           _M_results = _M_cur_results;
368             }
369             }
370             }
371             }
372             else
373             {
374 0 0         if (_M_current == _M_begin
375 0           && (_M_flags & regex_constants::match_not_null))
376 0           break;
377 0 0         if (__match_mode == _Match_mode::_Prefix || _M_current == _M_end)
    0          
    0          
378 0 0         if (!_M_has_sol)
379             {
380 0           _M_has_sol = true;
381 0           _M_results = _M_cur_results;
382             }
383             }
384 0           break;
385             case _S_opcode_alternative:
386 0 0         if (_M_nfa._M_flags & regex_constants::ECMAScript)
    0          
387             {
388             // TODO: Let BFS support ECMAScript's alternative operation.
389             _GLIBCXX_DEBUG_ASSERT(__dfs_mode);
390 0           _M_dfs(__match_mode, __state._M_alt);
391             // Pick lhs if it matches. Only try rhs if it doesn't.
392 0           if (!_M_has_sol)
393 0           _M_dfs(__match_mode, __state._M_next);
394             }
395             else
396             {
397             // Try both and compare the result.
398             // See "case _S_opcode_accept:" handling above.
399 0           _M_dfs(__match_mode, __state._M_alt);
400 0           auto __has_sol = _M_has_sol;
401 0           _M_has_sol = false;
402 0           _M_dfs(__match_mode, __state._M_next);
403 0           _M_has_sol |= __has_sol;
404             }
405 0           break;
406             default:
407             _GLIBCXX_DEBUG_ASSERT(false);
408             }
409             }
410              
411             // Return whether now is at some word boundary.
412             template
413             bool __dfs_mode>
414 0           bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
415             _M_word_boundary() const
416             {
417 0           bool __left_is_word = false;
418 0 0         if (_M_current != _M_begin
    0          
419 0           || (_M_flags & regex_constants::match_prev_avail))
420             {
421 0           auto __prev = _M_current;
422 0 0         if (_M_is_word(*std::prev(__prev)))
    0          
    0          
    0          
    0          
    0          
423 0           __left_is_word = true;
424             }
425             bool __right_is_word =
426 0 0         _M_current != _M_end && _M_is_word(*_M_current);
    0          
    0          
    0          
427              
428 0 0         if (__left_is_word == __right_is_word)
    0          
429 0           return false;
430 0 0         if (__left_is_word && !(_M_flags & regex_constants::match_not_eow))
    0          
    0          
    0          
    0          
    0          
431 0           return true;
432 0 0         if (__right_is_word && !(_M_flags & regex_constants::match_not_bow))
    0          
    0          
    0          
    0          
    0          
433 0           return true;
434 0           return false;
435             }
436              
437             _GLIBCXX_END_NAMESPACE_VERSION
438             } // namespace __detail
439             } // namespace