1 | /* |
2 | * Copyright (c) 2015-2017, Intel Corporation |
3 | * |
4 | * Redistribution and use in source and binary forms, with or without |
5 | * modification, are permitted provided that the following conditions are met: |
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14 | * without specific prior written permission. |
15 | * |
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27 | */ |
28 | |
29 | /** \file |
30 | * \brief DFA determinisation code. |
31 | */ |
32 | |
33 | #ifndef DETERMINISE_H |
34 | #define DETERMINISE_H |
35 | |
36 | #include "nfagraph/ng_holder.h" |
37 | #include "charreach.h" |
38 | #include "container.h" |
39 | #include "ue2common.h" |
40 | |
41 | #include <algorithm> |
42 | #include <array> |
43 | #include <queue> |
44 | #include <vector> |
45 | |
46 | namespace ue2 { |
47 | |
48 | /* Automaton details: |
49 | * |
50 | * const vector<StateSet> initial() |
51 | * returns initial states to start determinising from. StateSets in the |
52 | * initial() vector will given consecutive ids starting from 1, in the order |
53 | * that they appear. |
54 | * |
55 | * void reports(StateSet s, flat_set<ReportID> *out) |
56 | * fills out with any reports that need to be raised for stateset. |
57 | * |
58 | * void reportsEod(StateSet s, flat_set<ReportID> *out) |
59 | * fills out with any reports that need to be raised for stateset at EOD. |
60 | * |
61 | * void transition(const StateSet &in, StateSet *next) |
62 | * fills the next array such next[i] is the stateset that in transitions to |
63 | * on seeing symbol i (i is in the compressed alphabet of the automaton). |
64 | * |
65 | * u16 alphasize |
66 | * size of the compressed alphabet |
67 | */ |
68 | |
69 | /** \brief determinises some sort of nfa |
70 | * \param n the automaton to determinise |
71 | * \param dstates_out output dfa states |
72 | * \param state_limit limit on the number of dfa states to construct |
73 | * \param statesets_out a mapping from DFA state to the set of NFA states in |
74 | * the automaton |
75 | * \return true on success, false if state limit exceeded |
76 | */ |
77 | template<class Auto, class ds> |
78 | never_inline |
79 | bool determinise(Auto &n, std::vector<ds> &dstates, size_t state_limit, |
80 | std::vector<typename Auto::StateSet> *statesets_out = nullptr) { |
81 | DEBUG_PRINTF("the determinator\n" ); |
82 | using StateSet = typename Auto::StateSet; |
83 | typename Auto::StateMap dstate_ids; |
84 | |
85 | const size_t alphabet_size = n.alphasize; |
86 | |
87 | dstates.clear(); |
88 | dstates.reserve(state_limit); |
89 | |
90 | dstate_ids.emplace(n.dead, DEAD_STATE); |
91 | dstates.push_back(ds(alphabet_size)); |
92 | std::fill_n(dstates[0].next.begin(), alphabet_size, DEAD_STATE); |
93 | |
94 | std::queue<std::pair<StateSet, dstate_id_t>> q; |
95 | q.emplace(n.dead, DEAD_STATE); |
96 | |
97 | const std::vector<StateSet> &init = n.initial(); |
98 | for (u32 i = 0; i < init.size(); i++) { |
99 | q.emplace(init[i], dstates.size()); |
100 | assert(!contains(dstate_ids, init[i])); |
101 | dstate_ids.emplace(init[i], dstates.size()); |
102 | dstates.push_back(ds(alphabet_size)); |
103 | } |
104 | |
105 | std::vector<StateSet> succs(alphabet_size, n.dead); |
106 | |
107 | while (!q.empty()) { |
108 | auto m = std::move(q.front()); |
109 | q.pop(); |
110 | StateSet &curr = m.first; |
111 | dstate_id_t curr_id = m.second; |
112 | |
113 | DEBUG_PRINTF("curr: %hu\n" , curr_id); |
114 | |
115 | /* fill in accepts */ |
116 | n.reports(curr, dstates[curr_id].reports); |
117 | n.reportsEod(curr, dstates[curr_id].reports_eod); |
118 | |
119 | if (!dstates[curr_id].reports.empty()) { |
120 | DEBUG_PRINTF("curr: %hu: is accept\n" , curr_id); |
121 | } |
122 | |
123 | if (!dstates[curr_id].reports.empty()) { |
124 | /* only external reports set ekeys */ |
125 | if (n.canPrune(dstates[curr_id].reports)) { |
126 | /* we only transition to dead on characters, TOPs leave us |
127 | * alone */ |
128 | std::fill_n(dstates[curr_id].next.begin(), alphabet_size, |
129 | DEAD_STATE); |
130 | dstates[curr_id].next[n.alpha[TOP]] = curr_id; |
131 | continue; |
132 | } |
133 | } |
134 | |
135 | /* fill in successor states */ |
136 | n.transition(curr, &succs[0]); |
137 | for (symbol_t s = 0; s < n.alphasize; s++) { |
138 | dstate_id_t succ_id; |
139 | if (s && succs[s] == succs[s - 1]) { |
140 | succ_id = dstates[curr_id].next[s - 1]; |
141 | } else { |
142 | auto p = dstate_ids.find(succs[s]); |
143 | if (p != dstate_ids.end()) { // succ[s] is already present |
144 | succ_id = p->second; |
145 | if (succ_id > curr_id && !dstates[succ_id].daddy |
146 | && n.unalpha[s] < N_CHARS) { |
147 | dstates[succ_id].daddy = curr_id; |
148 | } |
149 | } else { |
150 | succ_id = dstate_ids.size(); |
151 | dstate_ids.emplace(succs[s], succ_id); |
152 | dstates.push_back(ds(alphabet_size)); |
153 | dstates.back().daddy = n.unalpha[s] < N_CHARS ? curr_id : 0; |
154 | q.emplace(succs[s], succ_id); |
155 | } |
156 | |
157 | DEBUG_PRINTF("-->%hu on %02hx\n" , succ_id, n.unalpha[s]); |
158 | } |
159 | |
160 | if (succ_id >= state_limit) { |
161 | DEBUG_PRINTF("succ_id %hu >= state_limit %zu\n" , |
162 | succ_id, state_limit); |
163 | dstates.clear(); |
164 | return false; |
165 | } |
166 | |
167 | dstates[curr_id].next[s] = succ_id; |
168 | } |
169 | } |
170 | |
171 | // The dstates vector will persist in the raw_dfa. |
172 | dstates.shrink_to_fit(); |
173 | |
174 | if (statesets_out) { |
175 | auto &statesets = *statesets_out; |
176 | statesets.resize(dstate_ids.size()); |
177 | for (auto &m : dstate_ids) { |
178 | statesets[m.second] = std::move(m.first); |
179 | } |
180 | } |
181 | |
182 | DEBUG_PRINTF("ok\n" ); |
183 | return true; |
184 | } |
185 | |
186 | static inline |
187 | std::vector<CharReach> populateCR(const NGHolder &g, |
188 | const std::vector<NFAVertex> &v_by_index, |
189 | const std::array<u16, ALPHABET_SIZE> &alpha) { |
190 | std::vector<CharReach> cr_by_index(v_by_index.size()); |
191 | |
192 | for (size_t i = 0; i < v_by_index.size(); i++) { |
193 | const CharReach &cr = g[v_by_index[i]].char_reach; |
194 | CharReach &cr_out = cr_by_index[i]; |
195 | for (size_t s = cr.find_first(); s != cr.npos; s = cr.find_next(s)) { |
196 | cr_out.set(alpha[s]); |
197 | } |
198 | } |
199 | |
200 | return cr_by_index; |
201 | } |
202 | |
203 | } // namespace ue2 |
204 | |
205 | #endif |
206 | |