1 | /* |
2 | * Copyright (c) 2015-2018, 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: |
6 | * |
7 | * * Redistributions of source code must retain the above copyright notice, |
8 | * this list of conditions and the following disclaimer. |
9 | * * Redistributions in binary form must reproduce the above copyright |
10 | * notice, this list of conditions and the following disclaimer in the |
11 | * documentation and/or other materials provided with the distribution. |
12 | * * Neither the name of Intel Corporation nor the names of its contributors |
13 | * may be used to endorse or promote products derived from this software |
14 | * without specific prior written permission. |
15 | * |
16 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
17 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
18 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
19 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
20 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
21 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
22 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
23 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
24 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
25 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
26 | * POSSIBILITY OF SUCH DAMAGE. |
27 | */ |
28 | |
29 | /** \file |
30 | * \brief Stop Alphabet calculation. |
31 | */ |
32 | #include "ng_stop.h" |
33 | |
34 | #include "ng_depth.h" |
35 | #include "ng_holder.h" |
36 | #include "ng_misc_opt.h" |
37 | #include "ng_util.h" |
38 | #include "ue2common.h" |
39 | #include "nfa/castlecompile.h" |
40 | #include "som/som.h" |
41 | #include "util/charreach.h" |
42 | #include "util/container.h" |
43 | #include "util/dump_charclass.h" |
44 | #include "util/graph.h" |
45 | #include "util/graph_range.h" |
46 | #include "util/verify_types.h" |
47 | |
48 | #include <map> |
49 | #include <set> |
50 | #include <vector> |
51 | |
52 | using namespace std; |
53 | |
54 | namespace ue2 { |
55 | |
56 | /** Stop alphabet depth threshold. */ |
57 | static const u32 MAX_STOP_DEPTH = 8; |
58 | |
59 | namespace { |
60 | |
61 | /** Depths from start, startDs for this graph. */ |
62 | struct InitDepths { |
63 | explicit InitDepths(const NGHolder &g) |
64 | : start(calcDepthsFrom(g, g.start)), |
65 | startDs(calcDepthsFrom(g, g.startDs)) {} |
66 | |
67 | depth maxDist(const NGHolder &g, NFAVertex v) const { |
68 | u32 idx = g[v].index; |
69 | assert(idx < start.size() && idx < startDs.size()); |
70 | const depth &d_start = start.at(idx).max; |
71 | const depth &d_startDs = startDs.at(idx).max; |
72 | if (d_start.is_unreachable()) { |
73 | return d_startDs; |
74 | } else if (d_startDs.is_unreachable()) { |
75 | return d_start; |
76 | } |
77 | return max(d_start, d_startDs); |
78 | } |
79 | |
80 | private: |
81 | vector<DepthMinMax> start; |
82 | vector<DepthMinMax> startDs; |
83 | }; |
84 | |
85 | } // namespace |
86 | |
87 | /** Find the set of characters that are not present in the reachability of |
88 | * graph \p g after a certain depth (currently 8). If a character in this set |
89 | * is encountered, it means that the NFA is either dead or has not progressed |
90 | * more than 8 characters from its start states. |
91 | * |
92 | * This is only used to guide merging heuristics, use |
93 | * findLeftOffsetStopAlphabet for real uses. |
94 | */ |
95 | CharReach findStopAlphabet(const NGHolder &g, som_type som) { |
96 | const depth max_depth(MAX_STOP_DEPTH); |
97 | const InitDepths depths(g); |
98 | const map<NFAVertex, BoundedRepeatSummary> no_vertices; |
99 | |
100 | CharReach stopcr; |
101 | |
102 | for (auto v : vertices_range(g)) { |
103 | if (is_special(v, g)) { |
104 | continue; |
105 | } |
106 | |
107 | if (depths.maxDist(g, v) >= max_depth) { |
108 | if (som == SOM_NONE) { |
109 | stopcr |= reduced_cr(v, g, no_vertices); |
110 | } else { |
111 | stopcr |= g[v].char_reach; |
112 | } |
113 | } |
114 | } |
115 | |
116 | // Turn alphabet into stops. |
117 | stopcr.flip(); |
118 | |
119 | return stopcr; |
120 | } |
121 | |
122 | /** Calculate the stop alphabet for each depth from 0 to MAX_STOP_DEPTH. Then |
123 | * build an eight-bit mask per character C, with each bit representing the |
124 | * depth before the location of character C (if encountered) that the NFA would |
125 | * be in a predictable start state. */ |
126 | vector<u8> findLeftOffsetStopAlphabet(const NGHolder &g, som_type som) { |
127 | const depth max_depth(MAX_STOP_DEPTH); |
128 | const InitDepths depths(g); |
129 | const map<NFAVertex, BoundedRepeatSummary> no_vertices; |
130 | |
131 | vector<CharReach> reach(MAX_STOP_DEPTH); |
132 | |
133 | for (auto v : vertices_range(g)) { |
134 | if (is_special(v, g)) { |
135 | continue; |
136 | } |
137 | CharReach v_cr; |
138 | if (som == SOM_NONE) { |
139 | v_cr = reduced_cr(v, g, no_vertices); |
140 | } else { |
141 | v_cr = g[v].char_reach; |
142 | } |
143 | |
144 | u32 d = min(max_depth, depths.maxDist(g, v)); |
145 | for (u32 i = 0; i < d; i++) { |
146 | reach[i] |= v_cr; |
147 | } |
148 | } |
149 | |
150 | #ifdef DEBUG |
151 | for (u32 i = 0; i < MAX_STOP_DEPTH; i++) { |
152 | DEBUG_PRINTF("depth %u, stop chars: " , i); |
153 | describeClass(stdout, ~reach[i], 20, CC_OUT_TEXT); |
154 | printf("\n" ); |
155 | } |
156 | #endif |
157 | |
158 | vector<u8> stop(N_CHARS, 0); |
159 | |
160 | for (u32 i = 0; i < MAX_STOP_DEPTH; i++) { |
161 | CharReach cr = ~reach[i]; // invert reach for stop chars. |
162 | const u8 mask = 1U << i; |
163 | for (size_t c = cr.find_first(); c != cr.npos; c = cr.find_next(c)) { |
164 | stop[c] |= mask; |
165 | } |
166 | } |
167 | |
168 | return stop; |
169 | } |
170 | |
171 | vector<u8> findLeftOffsetStopAlphabet(const CastleProto &castle, |
172 | UNUSED som_type som) { |
173 | const depth max_width = findMaxWidth(castle); |
174 | DEBUG_PRINTF("castle has reach %s and max width %s\n" , |
175 | describeClass(castle.reach()).c_str(), |
176 | max_width.str().c_str()); |
177 | |
178 | const CharReach escape = ~castle.reach(); // invert reach for stop chars. |
179 | |
180 | u32 d = min(max_width, depth(MAX_STOP_DEPTH)); |
181 | const u8 mask = verify_u8((1U << d) - 1); |
182 | |
183 | vector<u8> stop(N_CHARS, 0); |
184 | |
185 | for (size_t c = escape.find_first(); c != escape.npos; |
186 | c = escape.find_next(c)) { |
187 | stop[c] |= mask; |
188 | } |
189 | |
190 | return stop; |
191 | } |
192 | |
193 | } // namespace ue2 |
194 | |