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6cb784b6 TS |
1 | // class template regex -*- C++ -*- |
2 | ||
5624e564 | 3 | // Copyright (C) 2013-2015 Free Software Foundation, Inc. |
6cb784b6 TS |
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 | // <http://www.gnu.org/licenses/>. | |
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 | ||
9f0d9611 | 37 | template<typename _BiIter, typename _Alloc, typename _TraitsT, |
097f0bcf | 38 | bool __dfs_mode> |
9f0d9611 | 39 | bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
18971f1f TS |
40 | _M_search() |
41 | { | |
02ba3fc2 TS |
42 | if (_M_search_from_first()) |
43 | return true; | |
18971f1f | 44 | if (_M_flags & regex_constants::match_continuous) |
02ba3fc2 TS |
45 | return false; |
46 | _M_flags |= regex_constants::match_prev_avail; | |
47 | while (_M_begin != _M_end) | |
18971f1f | 48 | { |
02ba3fc2 TS |
49 | ++_M_begin; |
50 | if (_M_search_from_first()) | |
18971f1f TS |
51 | return true; |
52 | } | |
18971f1f TS |
53 | return false; |
54 | } | |
55 | ||
097f0bcf JW |
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. | |
caaf33fa TS |
59 | // |
60 | // ------------------------------------------------------------ | |
61 | // | |
62 | // DFS mode: | |
63 | // | |
64 | // It applies a Depth-First-Search (aka backtracking) on given NFA and input | |
65 | // string. | |
097f0bcf JW |
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 | |
caaf33fa | 69 | // back-reference matcher; some don't, like assertion or other anchor nodes. |
097f0bcf JW |
70 | // When the input is exhausted and/or the current state is an accepting |
71 | // state, the whole executor returns true. | |
caaf33fa TS |
72 | // |
73 | // TODO: This approach is exponentially slow for certain input. | |
74 | // Try to compile the NFA to a DFA. | |
75 | // | |
ee54a3b3 | 76 | // Time complexity: \Omega(match_length), O(2^(_M_nfa.size())) |
caaf33fa TS |
77 | // Space complexity: \theta(match_results.size() + match_length) |
78 | // | |
097f0bcf JW |
79 | template<typename _BiIter, typename _Alloc, typename _TraitsT, |
80 | bool __dfs_mode> | |
81 | bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: | |
82 | _M_main_dispatch(_Match_mode __match_mode, __dfs) | |
83 | { | |
84 | _M_has_sol = false; | |
ad9ec7b3 | 85 | *_M_states._M_get_sol_pos() = _BiIter(); |
097f0bcf JW |
86 | _M_cur_results = _M_results; |
87 | _M_dfs(__match_mode, _M_states._M_start); | |
88 | return _M_has_sol; | |
89 | } | |
90 | ||
caaf33fa TS |
91 | // ------------------------------------------------------------ |
92 | // | |
93 | // BFS mode: | |
94 | // | |
95 | // Russ Cox's article (http://swtch.com/~rsc/regexp/regexp1.html) | |
96 | // explained this algorithm clearly. | |
97 | // | |
ee54a3b3 TS |
98 | // It first computes epsilon closure (states that can be achieved without |
99 | // consuming characters) for every state that's still matching, | |
097f0bcf JW |
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. | |
caaf33fa | 102 | // |
097f0bcf JW |
103 | // Then apply DFS using every _S_opcode_match (in _M_states._M_match_queue) |
104 | // as the start state. | |
caaf33fa TS |
105 | // |
106 | // It significantly reduces potential duplicate states, so has a better | |
107 | // upper bound; but it requires more overhead. | |
108 | // | |
ee54a3b3 | 109 | // Time complexity: \Omega(match_length * match_results.size()) |
caaf33fa | 110 | // O(match_length * _M_nfa.size() * match_results.size()) |
ee54a3b3 | 111 | // Space complexity: \Omega(_M_nfa.size() + match_results.size()) |
caaf33fa | 112 | // O(_M_nfa.size() * match_results.size()) |
9f0d9611 | 113 | template<typename _BiIter, typename _Alloc, typename _TraitsT, |
097f0bcf | 114 | bool __dfs_mode> |
9f0d9611 | 115 | bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
097f0bcf | 116 | _M_main_dispatch(_Match_mode __match_mode, __bfs) |
9f0d9611 | 117 | { |
097f0bcf JW |
118 | _M_states._M_queue(_M_states._M_start, _M_results); |
119 | bool __ret = false; | |
120 | while (1) | |
9f0d9611 TS |
121 | { |
122 | _M_has_sol = false; | |
097f0bcf JW |
123 | if (_M_states._M_match_queue.empty()) |
124 | break; | |
125 | std::fill_n(_M_states._M_visited_states.get(), _M_nfa.size(), false); | |
126 | auto __old_queue = std::move(_M_states._M_match_queue); | |
127 | for (auto& __task : __old_queue) | |
9f0d9611 | 128 | { |
097f0bcf JW |
129 | _M_cur_results = std::move(__task.second); |
130 | _M_dfs(__match_mode, __task.first); | |
9f0d9611 | 131 | } |
097f0bcf JW |
132 | if (__match_mode == _Match_mode::_Prefix) |
133 | __ret |= _M_has_sol; | |
134 | if (_M_current == _M_end) | |
135 | break; | |
136 | ++_M_current; | |
9f0d9611 | 137 | } |
097f0bcf JW |
138 | if (__match_mode == _Match_mode::_Exact) |
139 | __ret = _M_has_sol; | |
4228f932 | 140 | _M_states._M_match_queue.clear(); |
097f0bcf | 141 | return __ret; |
9f0d9611 TS |
142 | } |
143 | ||
144 | // Return whether now match the given sub-NFA. | |
145 | template<typename _BiIter, typename _Alloc, typename _TraitsT, | |
097f0bcf | 146 | bool __dfs_mode> |
9f0d9611 | 147 | bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
68e69ce2 | 148 | _M_lookahead(_State<_TraitsT> __state) |
9f0d9611 TS |
149 | { |
150 | _ResultsVec __what(_M_cur_results.size()); | |
097f0bcf JW |
151 | _Executor __sub(_M_current, _M_end, __what, _M_re, _M_flags); |
152 | __sub._M_states._M_start = __state._M_alt; | |
153 | if (__sub._M_search_from_first()) | |
9f0d9611 TS |
154 | { |
155 | for (size_t __i = 0; __i < __what.size(); __i++) | |
156 | if (__what[__i].matched) | |
157 | _M_cur_results[__i] = __what[__i]; | |
158 | return true; | |
159 | } | |
160 | return false; | |
161 | } | |
162 | ||
a670a9bb TS |
163 | // __rep_count records how many times (__rep_count.second) |
164 | // this node is visited under certain input iterator | |
165 | // (__rep_count.first). This prevent the executor from entering | |
166 | // infinite loop by refusing to continue when it's already been | |
167 | // visited more than twice. It's `twice` instead of `once` because | |
168 | // we need to spare one more time for potential group capture. | |
169 | template<typename _BiIter, typename _Alloc, typename _TraitsT, | |
170 | bool __dfs_mode> | |
a670a9bb | 171 | void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
097f0bcf | 172 | _M_rep_once_more(_Match_mode __match_mode, _StateIdT __i) |
a670a9bb TS |
173 | { |
174 | const auto& __state = _M_nfa[__i]; | |
175 | auto& __rep_count = _M_rep_count[__i]; | |
176 | if (__rep_count.second == 0 || __rep_count.first != _M_current) | |
177 | { | |
178 | auto __back = __rep_count; | |
179 | __rep_count.first = _M_current; | |
180 | __rep_count.second = 1; | |
097f0bcf | 181 | _M_dfs(__match_mode, __state._M_alt); |
a670a9bb TS |
182 | __rep_count = __back; |
183 | } | |
184 | else | |
185 | { | |
186 | if (__rep_count.second < 2) | |
187 | { | |
188 | __rep_count.second++; | |
097f0bcf | 189 | _M_dfs(__match_mode, __state._M_alt); |
a670a9bb TS |
190 | __rep_count.second--; |
191 | } | |
192 | } | |
193 | }; | |
194 | ||
9f0d9611 | 195 | template<typename _BiIter, typename _Alloc, typename _TraitsT, |
097f0bcf | 196 | bool __dfs_mode> |
9f0d9611 | 197 | void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
097f0bcf | 198 | _M_dfs(_Match_mode __match_mode, _StateIdT __i) |
6cb784b6 | 199 | { |
097f0bcf JW |
200 | if (_M_states._M_visited(__i)) |
201 | return; | |
9f0d9611 TS |
202 | |
203 | const auto& __state = _M_nfa[__i]; | |
caaf33fa TS |
204 | // Every change on _M_cur_results and _M_current will be rolled back after |
205 | // finishing the recursion step. | |
6cb784b6 | 206 | switch (__state._M_opcode) |
e280b6ff | 207 | { |
caaf33fa TS |
208 | // _M_alt branch is "match once more", while _M_next is "get me out |
209 | // of this quantifier". Executing _M_next first or _M_alt first don't | |
210 | // mean the same thing, and we need to choose the correct order under | |
211 | // given greedy mode. | |
a670a9bb TS |
212 | case _S_opcode_repeat: |
213 | { | |
214 | // Greedy. | |
215 | if (!__state._M_neg) | |
216 | { | |
097f0bcf | 217 | _M_rep_once_more(__match_mode, __i); |
a670a9bb TS |
218 | // If it's DFS executor and already accepted, we're done. |
219 | if (!__dfs_mode || !_M_has_sol) | |
097f0bcf | 220 | _M_dfs(__match_mode, __state._M_next); |
a670a9bb TS |
221 | } |
222 | else // Non-greedy mode | |
223 | { | |
224 | if (__dfs_mode) | |
225 | { | |
226 | // vice-versa. | |
097f0bcf | 227 | _M_dfs(__match_mode, __state._M_next); |
a670a9bb | 228 | if (!_M_has_sol) |
097f0bcf | 229 | _M_rep_once_more(__match_mode, __i); |
a670a9bb TS |
230 | } |
231 | else | |
232 | { | |
233 | // DON'T attempt anything, because there's already another | |
097f0bcf JW |
234 | // state with higher priority accepted. This state cannot |
235 | // be better by attempting its next node. | |
a670a9bb TS |
236 | if (!_M_has_sol) |
237 | { | |
097f0bcf | 238 | _M_dfs(__match_mode, __state._M_next); |
a670a9bb TS |
239 | // DON'T attempt anything if it's already accepted. An |
240 | // accepted state *must* be better than a solution that | |
241 | // matches a non-greedy quantifier one more time. | |
242 | if (!_M_has_sol) | |
097f0bcf | 243 | _M_rep_once_more(__match_mode, __i); |
a670a9bb TS |
244 | } |
245 | } | |
246 | } | |
9f0d9611 | 247 | } |
e280b6ff TS |
248 | break; |
249 | case _S_opcode_subexpr_begin: | |
a670a9bb TS |
250 | { |
251 | auto& __res = _M_cur_results[__state._M_subexpr]; | |
252 | auto __back = __res.first; | |
253 | __res.first = _M_current; | |
097f0bcf | 254 | _M_dfs(__match_mode, __state._M_next); |
a670a9bb TS |
255 | __res.first = __back; |
256 | } | |
e280b6ff TS |
257 | break; |
258 | case _S_opcode_subexpr_end: | |
a670a9bb TS |
259 | { |
260 | auto& __res = _M_cur_results[__state._M_subexpr]; | |
261 | auto __back = __res; | |
262 | __res.second = _M_current; | |
263 | __res.matched = true; | |
097f0bcf | 264 | _M_dfs(__match_mode, __state._M_next); |
a670a9bb TS |
265 | __res = __back; |
266 | } | |
e280b6ff | 267 | break; |
7b86458e | 268 | case _S_opcode_line_begin_assertion: |
9f0d9611 | 269 | if (_M_at_begin()) |
097f0bcf | 270 | _M_dfs(__match_mode, __state._M_next); |
7b86458e TS |
271 | break; |
272 | case _S_opcode_line_end_assertion: | |
9f0d9611 | 273 | if (_M_at_end()) |
097f0bcf | 274 | _M_dfs(__match_mode, __state._M_next); |
7b86458e | 275 | break; |
f054ff5b | 276 | case _S_opcode_word_boundary: |
4d838433 | 277 | if (_M_word_boundary() == !__state._M_neg) |
097f0bcf | 278 | _M_dfs(__match_mode, __state._M_next); |
7b86458e | 279 | break; |
caaf33fa TS |
280 | // Here __state._M_alt offers a single start node for a sub-NFA. |
281 | // We recursively invoke our algorithm to match the sub-NFA. | |
7b86458e | 282 | case _S_opcode_subexpr_lookahead: |
9f0d9611 | 283 | if (_M_lookahead(__state) == !__state._M_neg) |
097f0bcf | 284 | _M_dfs(__match_mode, __state._M_next); |
7b86458e | 285 | break; |
e280b6ff | 286 | case _S_opcode_match: |
4d838433 TS |
287 | if (_M_current == _M_end) |
288 | break; | |
9f0d9611 | 289 | if (__dfs_mode) |
e280b6ff | 290 | { |
4d838433 | 291 | if (__state._M_matches(*_M_current)) |
9f0d9611 TS |
292 | { |
293 | ++_M_current; | |
097f0bcf | 294 | _M_dfs(__match_mode, __state._M_next); |
9f0d9611 TS |
295 | --_M_current; |
296 | } | |
e280b6ff | 297 | } |
9f0d9611 TS |
298 | else |
299 | if (__state._M_matches(*_M_current)) | |
097f0bcf | 300 | _M_states._M_queue(__state._M_next, _M_cur_results); |
e280b6ff | 301 | break; |
b21abcee | 302 | // First fetch the matched result from _M_cur_results as __submatch; |
e280b6ff | 303 | // then compare it with |
caaf33fa TS |
304 | // (_M_current, _M_current + (__submatch.second - __submatch.first)). |
305 | // If matched, keep going; else just return and try another state. | |
e280b6ff TS |
306 | case _S_opcode_backref: |
307 | { | |
9f0d9611 | 308 | _GLIBCXX_DEBUG_ASSERT(__dfs_mode); |
b21abcee | 309 | auto& __submatch = _M_cur_results[__state._M_backref_index]; |
e280b6ff TS |
310 | if (!__submatch.matched) |
311 | break; | |
9f0d9611 | 312 | auto __last = _M_current; |
d0cbab5f | 313 | for (auto __tmp = __submatch.first; |
9f0d9611 | 314 | __last != _M_end && __tmp != __submatch.second; |
e280b6ff TS |
315 | ++__tmp) |
316 | ++__last; | |
2bde8cac TS |
317 | if (_M_re._M_automaton->_M_traits.transform(__submatch.first, |
318 | __submatch.second) | |
319 | == _M_re._M_automaton->_M_traits.transform(_M_current, __last)) | |
ab1c993b | 320 | { |
9f0d9611 | 321 | if (__last != _M_current) |
ab1c993b | 322 | { |
9f0d9611 TS |
323 | auto __backup = _M_current; |
324 | _M_current = __last; | |
097f0bcf | 325 | _M_dfs(__match_mode, __state._M_next); |
9f0d9611 | 326 | _M_current = __backup; |
ab1c993b TS |
327 | } |
328 | else | |
097f0bcf | 329 | _M_dfs(__match_mode, __state._M_next); |
ab1c993b | 330 | } |
e280b6ff TS |
331 | } |
332 | break; | |
333 | case _S_opcode_accept: | |
9f0d9611 | 334 | if (__dfs_mode) |
e280b6ff | 335 | { |
9f0d9611 | 336 | _GLIBCXX_DEBUG_ASSERT(!_M_has_sol); |
097f0bcf | 337 | if (__match_mode == _Match_mode::_Exact) |
9f0d9611 TS |
338 | _M_has_sol = _M_current == _M_end; |
339 | else | |
340 | _M_has_sol = true; | |
341 | if (_M_current == _M_begin | |
342 | && (_M_flags & regex_constants::match_not_null)) | |
343 | _M_has_sol = false; | |
344 | if (_M_has_sol) | |
ad9ec7b3 TS |
345 | { |
346 | if (_M_nfa._M_flags & regex_constants::ECMAScript) | |
347 | _M_results = _M_cur_results; | |
348 | else // POSIX | |
349 | { | |
350 | _GLIBCXX_DEBUG_ASSERT(_M_states._M_get_sol_pos()); | |
351 | // Here's POSIX's logic: match the longest one. However | |
352 | // we never know which one (lhs or rhs of "|") is longer | |
353 | // unless we try both of them and compare the results. | |
354 | // The member variable _M_sol_pos records the end | |
355 | // position of the last successful match. It's better | |
356 | // to be larger, because POSIX regex is always greedy. | |
357 | // TODO: This could be slow. | |
358 | if (*_M_states._M_get_sol_pos() == _BiIter() | |
359 | || std::distance(_M_begin, | |
360 | *_M_states._M_get_sol_pos()) | |
361 | < std::distance(_M_begin, _M_current)) | |
362 | { | |
363 | *_M_states._M_get_sol_pos() = _M_current; | |
364 | _M_results = _M_cur_results; | |
365 | } | |
366 | } | |
367 | } | |
e280b6ff | 368 | } |
9f0d9611 | 369 | else |
18971f1f | 370 | { |
9f0d9611 TS |
371 | if (_M_current == _M_begin |
372 | && (_M_flags & regex_constants::match_not_null)) | |
373 | break; | |
097f0bcf | 374 | if (__match_mode == _Match_mode::_Prefix || _M_current == _M_end) |
9f0d9611 TS |
375 | if (!_M_has_sol) |
376 | { | |
377 | _M_has_sol = true; | |
378 | _M_results = _M_cur_results; | |
379 | } | |
18971f1f | 380 | } |
9f0d9611 | 381 | break; |
a670a9bb | 382 | case _S_opcode_alternative: |
ad9ec7b3 TS |
383 | if (_M_nfa._M_flags & regex_constants::ECMAScript) |
384 | { | |
e4846be7 | 385 | // TODO: Fix BFS support. It is wrong. |
ad9ec7b3 TS |
386 | _M_dfs(__match_mode, __state._M_alt); |
387 | // Pick lhs if it matches. Only try rhs if it doesn't. | |
388 | if (!_M_has_sol) | |
389 | _M_dfs(__match_mode, __state._M_next); | |
390 | } | |
391 | else | |
392 | { | |
393 | // Try both and compare the result. | |
394 | // See "case _S_opcode_accept:" handling above. | |
395 | _M_dfs(__match_mode, __state._M_alt); | |
396 | auto __has_sol = _M_has_sol; | |
397 | _M_has_sol = false; | |
398 | _M_dfs(__match_mode, __state._M_next); | |
399 | _M_has_sol |= __has_sol; | |
400 | } | |
a670a9bb | 401 | break; |
9f0d9611 TS |
402 | default: |
403 | _GLIBCXX_DEBUG_ASSERT(false); | |
e280b6ff | 404 | } |
6cb784b6 TS |
405 | } |
406 | ||
f054ff5b | 407 | // Return whether now is at some word boundary. |
9f0d9611 | 408 | template<typename _BiIter, typename _Alloc, typename _TraitsT, |
097f0bcf | 409 | bool __dfs_mode> |
9f0d9611 | 410 | bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>:: |
4d838433 | 411 | _M_word_boundary() const |
b21abcee | 412 | { |
4d838433 TS |
413 | bool __left_is_word = false; |
414 | if (_M_current != _M_begin | |
415 | || (_M_flags & regex_constants::match_prev_avail)) | |
ab1c993b | 416 | { |
4d838433 TS |
417 | auto __prev = _M_current; |
418 | if (_M_is_word(*std::prev(__prev))) | |
419 | __left_is_word = true; | |
ab1c993b | 420 | } |
4d838433 TS |
421 | bool __right_is_word = |
422 | _M_current != _M_end && _M_is_word(*_M_current); | |
423 | ||
424 | if (__left_is_word == __right_is_word) | |
425 | return false; | |
426 | if (__left_is_word && !(_M_flags & regex_constants::match_not_eow)) | |
427 | return true; | |
428 | if (__right_is_word && !(_M_flags & regex_constants::match_not_bow)) | |
429 | return true; | |
430 | return false; | |
b21abcee TS |
431 | } |
432 | ||
6cb784b6 TS |
433 | _GLIBCXX_END_NAMESPACE_VERSION |
434 | } // namespace __detail | |
435 | } // namespace |