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author | Ben Cheng <bccheng@google.com> | 2014-03-25 22:37:19 -0700 |
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committer | Ben Cheng <bccheng@google.com> | 2014-03-25 22:37:19 -0700 |
commit | 1bc5aee63eb72b341f506ad058502cd0361f0d10 (patch) | |
tree | c607e8252f3405424ff15bc2d00aa38dadbb2518 /gcc-4.9/libstdc++-v3/include/bits/regex_executor.tcc | |
parent | 283a0bf58fcf333c58a2a92c3ebbc41fb9eb1fdb (diff) | |
download | toolchain_gcc-1bc5aee63eb72b341f506ad058502cd0361f0d10.zip toolchain_gcc-1bc5aee63eb72b341f506ad058502cd0361f0d10.tar.gz toolchain_gcc-1bc5aee63eb72b341f506ad058502cd0361f0d10.tar.bz2 |
Initial checkin of GCC 4.9.0 from trunk (r208799).
Change-Id: I48a3c08bb98542aa215912a75f03c0890e497dba
Diffstat (limited to 'gcc-4.9/libstdc++-v3/include/bits/regex_executor.tcc')
-rw-r--r-- | gcc-4.9/libstdc++-v3/include/bits/regex_executor.tcc | 374 |
1 files changed, 374 insertions, 0 deletions
diff --git a/gcc-4.9/libstdc++-v3/include/bits/regex_executor.tcc b/gcc-4.9/libstdc++-v3/include/bits/regex_executor.tcc new file mode 100644 index 0000000..68a5e04 --- /dev/null +++ b/gcc-4.9/libstdc++-v3/include/bits/regex_executor.tcc @@ -0,0 +1,374 @@ +// 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 _M_old_queue = std::move(*_M_match_queue); + for (auto __task : _M_old_queue) + { + _M_cur_results = __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 |