1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
|
/*!
Types and routines specific to sparse DFAs.
This module is the home of [`sparse::DFA`](DFA).
Unlike the [`dense`](super::dense) module, this module does not contain a
builder or configuration specific for sparse DFAs. Instead, the intended
way to build a sparse DFA is either by using a default configuration with
its constructor [`sparse::DFA::new`](DFA::new), or by first configuring the
construction of a dense DFA with [`dense::Builder`](super::dense::Builder)
and then calling [`dense::DFA::to_sparse`](super::dense::DFA::to_sparse). For
example, this configures a sparse DFA to do an overlapping search:
```
use regex_automata::{
dfa::{Automaton, OverlappingState, dense},
HalfMatch, Input, MatchKind,
};
let dense_re = dense::Builder::new()
.configure(dense::Config::new().match_kind(MatchKind::All))
.build(r"Samwise|Sam")?;
let sparse_re = dense_re.to_sparse()?;
// Setup our haystack and initial start state.
let input = Input::new("Samwise");
let mut state = OverlappingState::start();
// First, 'Sam' will match.
sparse_re.try_search_overlapping_fwd(&input, &mut state)?;
assert_eq!(Some(HalfMatch::must(0, 3)), state.get_match());
// And now 'Samwise' will match.
sparse_re.try_search_overlapping_fwd(&input, &mut state)?;
assert_eq!(Some(HalfMatch::must(0, 7)), state.get_match());
# Ok::<(), Box<dyn std::error::Error>>(())
```
*/
#[cfg(feature = "dfa-build")]
use core::iter;
use core::{
convert::{TryFrom, TryInto},
fmt,
mem::size_of,
};
#[cfg(feature = "dfa-build")]
use alloc::{vec, vec::Vec};
#[cfg(feature = "dfa-build")]
use crate::dfa::dense::{self, BuildError};
use crate::{
dfa::{
automaton::{fmt_state_indicator, Automaton},
dense::Flags,
special::Special,
StartKind, DEAD,
},
util::{
alphabet::{ByteClasses, ByteSet},
escape::DebugByte,
int::{Pointer, Usize, U16, U32},
prefilter::Prefilter,
primitives::{PatternID, StateID},
search::{Anchored, Input, MatchError},
start::{Start, StartByteMap},
wire::{self, DeserializeError, Endian, SerializeError},
},
};
const LABEL: &str = "rust-regex-automata-dfa-sparse";
const VERSION: u32 = 2;
/// A sparse deterministic finite automaton (DFA) with variable sized states.
///
/// In contrast to a [dense::DFA](crate::dfa::dense::DFA), a sparse DFA uses
/// a more space efficient representation for its transitions. Consequently,
/// sparse DFAs may use much less memory than dense DFAs, but this comes at a
/// price. In particular, reading the more space efficient transitions takes
/// more work, and consequently, searching using a sparse DFA is typically
/// slower than a dense DFA.
///
/// A sparse DFA can be built using the default configuration via the
/// [`DFA::new`] constructor. Otherwise, one can configure various aspects
/// of a dense DFA via [`dense::Builder`](crate::dfa::dense::Builder),
/// and then convert a dense DFA to a sparse DFA using
/// [`dense::DFA::to_sparse`](crate::dfa::dense::DFA::to_sparse).
///
/// In general, a sparse DFA supports all the same search operations as a dense
/// DFA.
///
/// Making the choice between a dense and sparse DFA depends on your specific
/// work load. If you can sacrifice a bit of search time performance, then a
/// sparse DFA might be the best choice. In particular, while sparse DFAs are
/// probably always slower than dense DFAs, you may find that they are easily
/// fast enough for your purposes!
///
/// # Type parameters
///
/// A `DFA` has one type parameter, `T`, which is used to represent the parts
/// of a sparse DFA. `T` is typically a `Vec<u8>` or a `&[u8]`.
///
/// # The `Automaton` trait
///
/// This type implements the [`Automaton`] trait, which means it can be used
/// for searching. For example:
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse::DFA}, HalfMatch, Input};
///
/// let dfa = DFA::new("foo[0-9]+")?;
/// let expected = Some(HalfMatch::must(0, 8));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[derive(Clone)]
pub struct DFA<T> {
// When compared to a dense DFA, a sparse DFA *looks* a lot simpler
// representation-wise. In reality, it is perhaps more complicated. Namely,
// in a dense DFA, all information needs to be very cheaply accessible
// using only state IDs. In a sparse DFA however, each state uses a
// variable amount of space because each state encodes more information
// than just its transitions. Each state also includes an accelerator if
// one exists, along with the matching pattern IDs if the state is a match
// state.
//
// That is, a lot of the complexity is pushed down into how each state
// itself is represented.
tt: Transitions<T>,
st: StartTable<T>,
special: Special,
pre: Option<Prefilter>,
quitset: ByteSet,
flags: Flags,
}
#[cfg(feature = "dfa-build")]
impl DFA<Vec<u8>> {
/// Parse the given regular expression using a default configuration and
/// return the corresponding sparse DFA.
///
/// If you want a non-default configuration, then use
/// the [`dense::Builder`](crate::dfa::dense::Builder)
/// to set your own configuration, and then call
/// [`dense::DFA::to_sparse`](crate::dfa::dense::DFA::to_sparse) to create
/// a sparse DFA.
///
/// # Example
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse}, HalfMatch, Input};
///
/// let dfa = sparse::DFA::new("foo[0-9]+bar")?;
///
/// let expected = Some(HalfMatch::must(0, 11));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345bar"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[cfg(feature = "syntax")]
pub fn new(pattern: &str) -> Result<DFA<Vec<u8>>, BuildError> {
dense::Builder::new()
.build(pattern)
.and_then(|dense| dense.to_sparse())
}
/// Parse the given regular expressions using a default configuration and
/// return the corresponding multi-DFA.
///
/// If you want a non-default configuration, then use
/// the [`dense::Builder`](crate::dfa::dense::Builder)
/// to set your own configuration, and then call
/// [`dense::DFA::to_sparse`](crate::dfa::dense::DFA::to_sparse) to create
/// a sparse DFA.
///
/// # Example
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse}, HalfMatch, Input};
///
/// let dfa = sparse::DFA::new_many(&["[0-9]+", "[a-z]+"])?;
/// let expected = Some(HalfMatch::must(1, 3));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345bar"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[cfg(feature = "syntax")]
pub fn new_many<P: AsRef<str>>(
patterns: &[P],
) -> Result<DFA<Vec<u8>>, BuildError> {
dense::Builder::new()
.build_many(patterns)
.and_then(|dense| dense.to_sparse())
}
}
#[cfg(feature = "dfa-build")]
impl DFA<Vec<u8>> {
/// Create a new DFA that matches every input.
///
/// # Example
///
/// ```
/// use regex_automata::{
/// dfa::{Automaton, sparse},
/// HalfMatch, Input,
/// };
///
/// let dfa = sparse::DFA::always_match()?;
///
/// let expected = Some(HalfMatch::must(0, 0));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new(""))?);
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn always_match() -> Result<DFA<Vec<u8>>, BuildError> {
dense::DFA::always_match()?.to_sparse()
}
/// Create a new sparse DFA that never matches any input.
///
/// # Example
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse}, Input};
///
/// let dfa = sparse::DFA::never_match()?;
/// assert_eq!(None, dfa.try_search_fwd(&Input::new(""))?);
/// assert_eq!(None, dfa.try_search_fwd(&Input::new("foo"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn never_match() -> Result<DFA<Vec<u8>>, BuildError> {
dense::DFA::never_match()?.to_sparse()
}
/// The implementation for constructing a sparse DFA from a dense DFA.
pub(crate) fn from_dense<T: AsRef<[u32]>>(
dfa: &dense::DFA<T>,
) -> Result<DFA<Vec<u8>>, BuildError> {
// In order to build the transition table, we need to be able to write
// state identifiers for each of the "next" transitions in each state.
// Our state identifiers correspond to the byte offset in the
// transition table at which the state is encoded. Therefore, we do not
// actually know what the state identifiers are until we've allocated
// exactly as much space as we need for each state. Thus, construction
// of the transition table happens in two passes.
//
// In the first pass, we fill out the shell of each state, which
// includes the transition length, the input byte ranges and
// zero-filled space for the transitions and accelerators, if present.
// In this first pass, we also build up a map from the state identifier
// index of the dense DFA to the state identifier in this sparse DFA.
//
// In the second pass, we fill in the transitions based on the map
// built in the first pass.
// The capacity given here reflects a minimum. (Well, the true minimum
// is likely even bigger, but hopefully this saves a few reallocs.)
let mut sparse = Vec::with_capacity(StateID::SIZE * dfa.state_len());
// This maps state indices from the dense DFA to StateIDs in the sparse
// DFA. We build out this map on the first pass, and then use it in the
// second pass to back-fill our transitions.
let mut remap: Vec<StateID> = vec![DEAD; dfa.state_len()];
for state in dfa.states() {
let pos = sparse.len();
remap[dfa.to_index(state.id())] = StateID::new(pos)
.map_err(|_| BuildError::too_many_states())?;
// zero-filled space for the transition length
sparse.push(0);
sparse.push(0);
let mut transition_len = 0;
for (unit1, unit2, _) in state.sparse_transitions() {
match (unit1.as_u8(), unit2.as_u8()) {
(Some(b1), Some(b2)) => {
transition_len += 1;
sparse.push(b1);
sparse.push(b2);
}
(None, None) => {}
(Some(_), None) | (None, Some(_)) => {
// can never occur because sparse_transitions never
// groups EOI with any other transition.
unreachable!()
}
}
}
// Add dummy EOI transition. This is never actually read while
// searching, but having space equivalent to the total number
// of transitions is convenient. Otherwise, we'd need to track
// a different number of transitions for the byte ranges as for
// the 'next' states.
//
// N.B. The loop above is not guaranteed to yield the EOI
// transition, since it may point to a DEAD state. By putting
// it here, we always write the EOI transition, and thus
// guarantee that our transition length is >0. Why do we always
// need the EOI transition? Because in order to implement
// Automaton::next_eoi_state, this lets us just ask for the last
// transition. There are probably other/better ways to do this.
transition_len += 1;
sparse.push(0);
sparse.push(0);
// Check some assumptions about transition length.
assert_ne!(
transition_len, 0,
"transition length should be non-zero",
);
assert!(
transition_len <= 257,
"expected transition length {} to be <= 257",
transition_len,
);
// Fill in the transition length.
// Since transition length is always <= 257, we use the most
// significant bit to indicate whether this is a match state or
// not.
let ntrans = if dfa.is_match_state(state.id()) {
transition_len | (1 << 15)
} else {
transition_len
};
wire::NE::write_u16(ntrans, &mut sparse[pos..]);
// zero-fill the actual transitions.
// Unwraps are OK since transition_length <= 257 and our minimum
// support usize size is 16-bits.
let zeros = usize::try_from(transition_len)
.unwrap()
.checked_mul(StateID::SIZE)
.unwrap();
sparse.extend(iter::repeat(0).take(zeros));
// If this is a match state, write the pattern IDs matched by this
// state.
if dfa.is_match_state(state.id()) {
let plen = dfa.match_pattern_len(state.id());
// Write the actual pattern IDs with a u32 length prefix.
// First, zero-fill space.
let mut pos = sparse.len();
// Unwraps are OK since it's guaranteed that plen <=
// PatternID::LIMIT, which is in turn guaranteed to fit into a
// u32.
let zeros = size_of::<u32>()
.checked_mul(plen)
.unwrap()
.checked_add(size_of::<u32>())
.unwrap();
sparse.extend(iter::repeat(0).take(zeros));
// Now write the length prefix.
wire::NE::write_u32(
// Will never fail since u32::MAX is invalid pattern ID.
// Thus, the number of pattern IDs is representable by a
// u32.
plen.try_into().expect("pattern ID length fits in u32"),
&mut sparse[pos..],
);
pos += size_of::<u32>();
// Now write the pattern IDs.
for &pid in dfa.pattern_id_slice(state.id()) {
pos += wire::write_pattern_id::<wire::NE>(
pid,
&mut sparse[pos..],
);
}
}
// And now add the accelerator, if one exists. An accelerator is
// at most 4 bytes and at least 1 byte. The first byte is the
// length, N. N bytes follow the length. The set of bytes that
// follow correspond (exhaustively) to the bytes that must be seen
// to leave this state.
let accel = dfa.accelerator(state.id());
sparse.push(accel.len().try_into().unwrap());
sparse.extend_from_slice(accel);
}
let mut new = DFA {
tt: Transitions {
sparse,
classes: dfa.byte_classes().clone(),
state_len: dfa.state_len(),
pattern_len: dfa.pattern_len(),
},
st: StartTable::from_dense_dfa(dfa, &remap)?,
special: dfa.special().remap(|id| remap[dfa.to_index(id)]),
pre: dfa.get_prefilter().map(|p| p.clone()),
quitset: dfa.quitset().clone(),
flags: dfa.flags().clone(),
};
// And here's our second pass. Iterate over all of the dense states
// again, and update the transitions in each of the states in the
// sparse DFA.
for old_state in dfa.states() {
let new_id = remap[dfa.to_index(old_state.id())];
let mut new_state = new.tt.state_mut(new_id);
let sparse = old_state.sparse_transitions();
for (i, (_, _, next)) in sparse.enumerate() {
let next = remap[dfa.to_index(next)];
new_state.set_next_at(i, next);
}
}
debug!(
"created sparse DFA, memory usage: {} (dense memory usage: {})",
new.memory_usage(),
dfa.memory_usage(),
);
Ok(new)
}
}
impl<T: AsRef<[u8]>> DFA<T> {
/// Cheaply return a borrowed version of this sparse DFA. Specifically, the
/// DFA returned always uses `&[u8]` for its transitions.
pub fn as_ref<'a>(&'a self) -> DFA<&'a [u8]> {
DFA {
tt: self.tt.as_ref(),
st: self.st.as_ref(),
special: self.special,
pre: self.pre.clone(),
quitset: self.quitset,
flags: self.flags,
}
}
/// Return an owned version of this sparse DFA. Specifically, the DFA
/// returned always uses `Vec<u8>` for its transitions.
///
/// Effectively, this returns a sparse DFA whose transitions live on the
/// heap.
#[cfg(feature = "alloc")]
pub fn to_owned(&self) -> DFA<alloc::vec::Vec<u8>> {
DFA {
tt: self.tt.to_owned(),
st: self.st.to_owned(),
special: self.special,
pre: self.pre.clone(),
quitset: self.quitset,
flags: self.flags,
}
}
/// Returns the starting state configuration for this DFA.
///
/// The default is [`StartKind::Both`], which means the DFA supports both
/// unanchored and anchored searches. However, this can generally lead to
/// bigger DFAs. Therefore, a DFA might be compiled with support for just
/// unanchored or anchored searches. In that case, running a search with
/// an unsupported configuration will panic.
pub fn start_kind(&self) -> StartKind {
self.st.kind
}
/// Returns true only if this DFA has starting states for each pattern.
///
/// When a DFA has starting states for each pattern, then a search with the
/// DFA can be configured to only look for anchored matches of a specific
/// pattern. Specifically, APIs like [`Automaton::try_search_fwd`] can
/// accept a [`Anchored::Pattern`] if and only if this method returns true.
/// Otherwise, an error will be returned.
///
/// Note that if the DFA is empty, this always returns false.
pub fn starts_for_each_pattern(&self) -> bool {
self.st.pattern_len.is_some()
}
/// Returns the equivalence classes that make up the alphabet for this DFA.
///
/// Unless [`dense::Config::byte_classes`] was disabled, it is possible
/// that multiple distinct bytes are grouped into the same equivalence
/// class if it is impossible for them to discriminate between a match and
/// a non-match. This has the effect of reducing the overall alphabet size
/// and in turn potentially substantially reducing the size of the DFA's
/// transition table.
///
/// The downside of using equivalence classes like this is that every state
/// transition will automatically use this map to convert an arbitrary
/// byte to its corresponding equivalence class. In practice this has a
/// negligible impact on performance.
pub fn byte_classes(&self) -> &ByteClasses {
&self.tt.classes
}
/// Returns the memory usage, in bytes, of this DFA.
///
/// The memory usage is computed based on the number of bytes used to
/// represent this DFA.
///
/// This does **not** include the stack size used up by this DFA. To
/// compute that, use `std::mem::size_of::<sparse::DFA>()`.
pub fn memory_usage(&self) -> usize {
self.tt.memory_usage() + self.st.memory_usage()
}
}
/// Routines for converting a sparse DFA to other representations, such as raw
/// bytes suitable for persistent storage.
impl<T: AsRef<[u8]>> DFA<T> {
/// Serialize this DFA as raw bytes to a `Vec<u8>` in little endian
/// format.
///
/// The written bytes are guaranteed to be deserialized correctly and
/// without errors in a semver compatible release of this crate by a
/// `DFA`'s deserialization APIs (assuming all other criteria for the
/// deserialization APIs has been satisfied):
///
/// * [`DFA::from_bytes`]
/// * [`DFA::from_bytes_unchecked`]
///
/// Note that unlike a [`dense::DFA`](crate::dfa::dense::DFA)'s
/// serialization methods, this does not add any initial padding to the
/// returned bytes. Padding isn't required for sparse DFAs since they have
/// no alignment requirements.
///
/// # Example
///
/// This example shows how to serialize and deserialize a DFA:
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse::DFA}, HalfMatch, Input};
///
/// // Compile our original DFA.
/// let original_dfa = DFA::new("foo[0-9]+")?;
///
/// // N.B. We use native endianness here to make the example work, but
/// // using to_bytes_little_endian would work on a little endian target.
/// let buf = original_dfa.to_bytes_native_endian();
/// // Even if buf has initial padding, DFA::from_bytes will automatically
/// // ignore it.
/// let dfa: DFA<&[u8]> = DFA::from_bytes(&buf)?.0;
///
/// let expected = Some(HalfMatch::must(0, 8));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[cfg(feature = "dfa-build")]
pub fn to_bytes_little_endian(&self) -> Vec<u8> {
self.to_bytes::<wire::LE>()
}
/// Serialize this DFA as raw bytes to a `Vec<u8>` in big endian
/// format.
///
/// The written bytes are guaranteed to be deserialized correctly and
/// without errors in a semver compatible release of this crate by a
/// `DFA`'s deserialization APIs (assuming all other criteria for the
/// deserialization APIs has been satisfied):
///
/// * [`DFA::from_bytes`]
/// * [`DFA::from_bytes_unchecked`]
///
/// Note that unlike a [`dense::DFA`](crate::dfa::dense::DFA)'s
/// serialization methods, this does not add any initial padding to the
/// returned bytes. Padding isn't required for sparse DFAs since they have
/// no alignment requirements.
///
/// # Example
///
/// This example shows how to serialize and deserialize a DFA:
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse::DFA}, HalfMatch, Input};
///
/// // Compile our original DFA.
/// let original_dfa = DFA::new("foo[0-9]+")?;
///
/// // N.B. We use native endianness here to make the example work, but
/// // using to_bytes_big_endian would work on a big endian target.
/// let buf = original_dfa.to_bytes_native_endian();
/// // Even if buf has initial padding, DFA::from_bytes will automatically
/// // ignore it.
/// let dfa: DFA<&[u8]> = DFA::from_bytes(&buf)?.0;
///
/// let expected = Some(HalfMatch::must(0, 8));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[cfg(feature = "dfa-build")]
pub fn to_bytes_big_endian(&self) -> Vec<u8> {
self.to_bytes::<wire::BE>()
}
/// Serialize this DFA as raw bytes to a `Vec<u8>` in native endian
/// format.
///
/// The written bytes are guaranteed to be deserialized correctly and
/// without errors in a semver compatible release of this crate by a
/// `DFA`'s deserialization APIs (assuming all other criteria for the
/// deserialization APIs has been satisfied):
///
/// * [`DFA::from_bytes`]
/// * [`DFA::from_bytes_unchecked`]
///
/// Note that unlike a [`dense::DFA`](crate::dfa::dense::DFA)'s
/// serialization methods, this does not add any initial padding to the
/// returned bytes. Padding isn't required for sparse DFAs since they have
/// no alignment requirements.
///
/// Generally speaking, native endian format should only be used when
/// you know that the target you're compiling the DFA for matches the
/// endianness of the target on which you're compiling DFA. For example,
/// if serialization and deserialization happen in the same process or on
/// the same machine. Otherwise, when serializing a DFA for use in a
/// portable environment, you'll almost certainly want to serialize _both_
/// a little endian and a big endian version and then load the correct one
/// based on the target's configuration.
///
/// # Example
///
/// This example shows how to serialize and deserialize a DFA:
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse::DFA}, HalfMatch, Input};
///
/// // Compile our original DFA.
/// let original_dfa = DFA::new("foo[0-9]+")?;
///
/// let buf = original_dfa.to_bytes_native_endian();
/// // Even if buf has initial padding, DFA::from_bytes will automatically
/// // ignore it.
/// let dfa: DFA<&[u8]> = DFA::from_bytes(&buf)?.0;
///
/// let expected = Some(HalfMatch::must(0, 8));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[cfg(feature = "dfa-build")]
pub fn to_bytes_native_endian(&self) -> Vec<u8> {
self.to_bytes::<wire::NE>()
}
/// The implementation of the public `to_bytes` serialization methods,
/// which is generic over endianness.
#[cfg(feature = "dfa-build")]
fn to_bytes<E: Endian>(&self) -> Vec<u8> {
let mut buf = vec![0; self.write_to_len()];
// This should always succeed since the only possible serialization
// error is providing a buffer that's too small, but we've ensured that
// `buf` is big enough here.
self.write_to::<E>(&mut buf).unwrap();
buf
}
/// Serialize this DFA as raw bytes to the given slice, in little endian
/// format. Upon success, the total number of bytes written to `dst` is
/// returned.
///
/// The written bytes are guaranteed to be deserialized correctly and
/// without errors in a semver compatible release of this crate by a
/// `DFA`'s deserialization APIs (assuming all other criteria for the
/// deserialization APIs has been satisfied):
///
/// * [`DFA::from_bytes`]
/// * [`DFA::from_bytes_unchecked`]
///
/// # Errors
///
/// This returns an error if the given destination slice is not big enough
/// to contain the full serialized DFA. If an error occurs, then nothing
/// is written to `dst`.
///
/// # Example
///
/// This example shows how to serialize and deserialize a DFA without
/// dynamic memory allocation.
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse::DFA}, HalfMatch, Input};
///
/// // Compile our original DFA.
/// let original_dfa = DFA::new("foo[0-9]+")?;
///
/// // Create a 4KB buffer on the stack to store our serialized DFA.
/// let mut buf = [0u8; 4 * (1<<10)];
/// // N.B. We use native endianness here to make the example work, but
/// // using write_to_little_endian would work on a little endian target.
/// let written = original_dfa.write_to_native_endian(&mut buf)?;
/// let dfa: DFA<&[u8]> = DFA::from_bytes(&buf[..written])?.0;
///
/// let expected = Some(HalfMatch::must(0, 8));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn write_to_little_endian(
&self,
dst: &mut [u8],
) -> Result<usize, SerializeError> {
self.write_to::<wire::LE>(dst)
}
/// Serialize this DFA as raw bytes to the given slice, in big endian
/// format. Upon success, the total number of bytes written to `dst` is
/// returned.
///
/// The written bytes are guaranteed to be deserialized correctly and
/// without errors in a semver compatible release of this crate by a
/// `DFA`'s deserialization APIs (assuming all other criteria for the
/// deserialization APIs has been satisfied):
///
/// * [`DFA::from_bytes`]
/// * [`DFA::from_bytes_unchecked`]
///
/// # Errors
///
/// This returns an error if the given destination slice is not big enough
/// to contain the full serialized DFA. If an error occurs, then nothing
/// is written to `dst`.
///
/// # Example
///
/// This example shows how to serialize and deserialize a DFA without
/// dynamic memory allocation.
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse::DFA}, HalfMatch, Input};
///
/// // Compile our original DFA.
/// let original_dfa = DFA::new("foo[0-9]+")?;
///
/// // Create a 4KB buffer on the stack to store our serialized DFA.
/// let mut buf = [0u8; 4 * (1<<10)];
/// // N.B. We use native endianness here to make the example work, but
/// // using write_to_big_endian would work on a big endian target.
/// let written = original_dfa.write_to_native_endian(&mut buf)?;
/// let dfa: DFA<&[u8]> = DFA::from_bytes(&buf[..written])?.0;
///
/// let expected = Some(HalfMatch::must(0, 8));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn write_to_big_endian(
&self,
dst: &mut [u8],
) -> Result<usize, SerializeError> {
self.write_to::<wire::BE>(dst)
}
/// Serialize this DFA as raw bytes to the given slice, in native endian
/// format. Upon success, the total number of bytes written to `dst` is
/// returned.
///
/// The written bytes are guaranteed to be deserialized correctly and
/// without errors in a semver compatible release of this crate by a
/// `DFA`'s deserialization APIs (assuming all other criteria for the
/// deserialization APIs has been satisfied):
///
/// * [`DFA::from_bytes`]
/// * [`DFA::from_bytes_unchecked`]
///
/// Generally speaking, native endian format should only be used when
/// you know that the target you're compiling the DFA for matches the
/// endianness of the target on which you're compiling DFA. For example,
/// if serialization and deserialization happen in the same process or on
/// the same machine. Otherwise, when serializing a DFA for use in a
/// portable environment, you'll almost certainly want to serialize _both_
/// a little endian and a big endian version and then load the correct one
/// based on the target's configuration.
///
/// # Errors
///
/// This returns an error if the given destination slice is not big enough
/// to contain the full serialized DFA. If an error occurs, then nothing
/// is written to `dst`.
///
/// # Example
///
/// This example shows how to serialize and deserialize a DFA without
/// dynamic memory allocation.
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse::DFA}, HalfMatch, Input};
///
/// // Compile our original DFA.
/// let original_dfa = DFA::new("foo[0-9]+")?;
///
/// // Create a 4KB buffer on the stack to store our serialized DFA.
/// let mut buf = [0u8; 4 * (1<<10)];
/// let written = original_dfa.write_to_native_endian(&mut buf)?;
/// let dfa: DFA<&[u8]> = DFA::from_bytes(&buf[..written])?.0;
///
/// let expected = Some(HalfMatch::must(0, 8));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn write_to_native_endian(
&self,
dst: &mut [u8],
) -> Result<usize, SerializeError> {
self.write_to::<wire::NE>(dst)
}
/// The implementation of the public `write_to` serialization methods,
/// which is generic over endianness.
fn write_to<E: Endian>(
&self,
dst: &mut [u8],
) -> Result<usize, SerializeError> {
let mut nw = 0;
nw += wire::write_label(LABEL, &mut dst[nw..])?;
nw += wire::write_endianness_check::<E>(&mut dst[nw..])?;
nw += wire::write_version::<E>(VERSION, &mut dst[nw..])?;
nw += {
// Currently unused, intended for future flexibility
E::write_u32(0, &mut dst[nw..]);
size_of::<u32>()
};
nw += self.flags.write_to::<E>(&mut dst[nw..])?;
nw += self.tt.write_to::<E>(&mut dst[nw..])?;
nw += self.st.write_to::<E>(&mut dst[nw..])?;
nw += self.special.write_to::<E>(&mut dst[nw..])?;
nw += self.quitset.write_to::<E>(&mut dst[nw..])?;
Ok(nw)
}
/// Return the total number of bytes required to serialize this DFA.
///
/// This is useful for determining the size of the buffer required to pass
/// to one of the serialization routines:
///
/// * [`DFA::write_to_little_endian`]
/// * [`DFA::write_to_big_endian`]
/// * [`DFA::write_to_native_endian`]
///
/// Passing a buffer smaller than the size returned by this method will
/// result in a serialization error.
///
/// # Example
///
/// This example shows how to dynamically allocate enough room to serialize
/// a sparse DFA.
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse::DFA}, HalfMatch, Input};
///
/// // Compile our original DFA.
/// let original_dfa = DFA::new("foo[0-9]+")?;
///
/// let mut buf = vec![0; original_dfa.write_to_len()];
/// let written = original_dfa.write_to_native_endian(&mut buf)?;
/// let dfa: DFA<&[u8]> = DFA::from_bytes(&buf[..written])?.0;
///
/// let expected = Some(HalfMatch::must(0, 8));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn write_to_len(&self) -> usize {
wire::write_label_len(LABEL)
+ wire::write_endianness_check_len()
+ wire::write_version_len()
+ size_of::<u32>() // unused, intended for future flexibility
+ self.flags.write_to_len()
+ self.tt.write_to_len()
+ self.st.write_to_len()
+ self.special.write_to_len()
+ self.quitset.write_to_len()
}
}
impl<'a> DFA<&'a [u8]> {
/// Safely deserialize a sparse DFA with a specific state identifier
/// representation. Upon success, this returns both the deserialized DFA
/// and the number of bytes read from the given slice. Namely, the contents
/// of the slice beyond the DFA are not read.
///
/// Deserializing a DFA using this routine will never allocate heap memory.
/// For safety purposes, the DFA's transitions will be verified such that
/// every transition points to a valid state. If this verification is too
/// costly, then a [`DFA::from_bytes_unchecked`] API is provided, which
/// will always execute in constant time.
///
/// The bytes given must be generated by one of the serialization APIs
/// of a `DFA` using a semver compatible release of this crate. Those
/// include:
///
/// * [`DFA::to_bytes_little_endian`]
/// * [`DFA::to_bytes_big_endian`]
/// * [`DFA::to_bytes_native_endian`]
/// * [`DFA::write_to_little_endian`]
/// * [`DFA::write_to_big_endian`]
/// * [`DFA::write_to_native_endian`]
///
/// The `to_bytes` methods allocate and return a `Vec<u8>` for you. The
/// `write_to` methods do not allocate and write to an existing slice
/// (which may be on the stack). Since deserialization always uses the
/// native endianness of the target platform, the serialization API you use
/// should match the endianness of the target platform. (It's often a good
/// idea to generate serialized DFAs for both forms of endianness and then
/// load the correct one based on endianness.)
///
/// # Errors
///
/// Generally speaking, it's easier to state the conditions in which an
/// error is _not_ returned. All of the following must be true:
///
/// * The bytes given must be produced by one of the serialization APIs
/// on this DFA, as mentioned above.
/// * The endianness of the target platform matches the endianness used to
/// serialized the provided DFA.
///
/// If any of the above are not true, then an error will be returned.
///
/// Note that unlike deserializing a
/// [`dense::DFA`](crate::dfa::dense::DFA), deserializing a sparse DFA has
/// no alignment requirements. That is, an alignment of `1` is valid.
///
/// # Panics
///
/// This routine will never panic for any input.
///
/// # Example
///
/// This example shows how to serialize a DFA to raw bytes, deserialize it
/// and then use it for searching.
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse::DFA}, HalfMatch, Input};
///
/// let initial = DFA::new("foo[0-9]+")?;
/// let bytes = initial.to_bytes_native_endian();
/// let dfa: DFA<&[u8]> = DFA::from_bytes(&bytes)?.0;
///
/// let expected = Some(HalfMatch::must(0, 8));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: loading a DFA from static memory
///
/// One use case this library supports is the ability to serialize a
/// DFA to disk and then use `include_bytes!` to store it in a compiled
/// Rust program. Those bytes can then be cheaply deserialized into a
/// `DFA` structure at runtime and used for searching without having to
/// re-compile the DFA (which can be quite costly).
///
/// We can show this in two parts. The first part is serializing the DFA to
/// a file:
///
/// ```no_run
/// use regex_automata::dfa::sparse::DFA;
///
/// let dfa = DFA::new("foo[0-9]+")?;
///
/// // Write a big endian serialized version of this DFA to a file.
/// let bytes = dfa.to_bytes_big_endian();
/// std::fs::write("foo.bigendian.dfa", &bytes)?;
///
/// // Do it again, but this time for little endian.
/// let bytes = dfa.to_bytes_little_endian();
/// std::fs::write("foo.littleendian.dfa", &bytes)?;
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// And now the second part is embedding the DFA into the compiled program
/// and deserializing it at runtime on first use. We use conditional
/// compilation to choose the correct endianness. We do not need to employ
/// any special tricks to ensure a proper alignment, since a sparse DFA has
/// no alignment requirements.
///
/// ```no_run
/// use regex_automata::{
/// dfa::{Automaton, sparse::DFA},
/// util::lazy::Lazy,
/// HalfMatch, Input,
/// };
///
/// // This crate provides its own "lazy" type, kind of like
/// // lazy_static! or once_cell::sync::Lazy. But it works in no-alloc
/// // no-std environments and let's us write this using completely
/// // safe code.
/// static RE: Lazy<DFA<&'static [u8]>> = Lazy::new(|| {
/// # const _: &str = stringify! {
/// #[cfg(target_endian = "big")]
/// static BYTES: &[u8] = include_bytes!("foo.bigendian.dfa");
/// #[cfg(target_endian = "little")]
/// static BYTES: &[u8] = include_bytes!("foo.littleendian.dfa");
/// # };
/// # static BYTES: &[u8] = b"";
///
/// let (dfa, _) = DFA::from_bytes(BYTES)
/// .expect("serialized DFA should be valid");
/// dfa
/// });
///
/// let expected = Ok(Some(HalfMatch::must(0, 8)));
/// assert_eq!(expected, RE.try_search_fwd(&Input::new("foo12345")));
/// ```
///
/// Alternatively, consider using
/// [`lazy_static`](https://crates.io/crates/lazy_static)
/// or
/// [`once_cell`](https://crates.io/crates/once_cell),
/// which will guarantee safety for you.
pub fn from_bytes(
slice: &'a [u8],
) -> Result<(DFA<&'a [u8]>, usize), DeserializeError> {
// SAFETY: This is safe because we validate both the sparse transitions
// (by trying to decode every state) and start state ID list below. If
// either validation fails, then we return an error.
let (dfa, nread) = unsafe { DFA::from_bytes_unchecked(slice)? };
dfa.tt.validate(&dfa.special)?;
dfa.st.validate(&dfa.special, &dfa.tt)?;
// N.B. dfa.special doesn't have a way to do unchecked deserialization,
// so it has already been validated.
Ok((dfa, nread))
}
/// Deserialize a DFA with a specific state identifier representation in
/// constant time by omitting the verification of the validity of the
/// sparse transitions.
///
/// This is just like [`DFA::from_bytes`], except it can potentially return
/// a DFA that exhibits undefined behavior if its transitions contains
/// invalid state identifiers.
///
/// This routine is useful if you need to deserialize a DFA cheaply and
/// cannot afford the transition validation performed by `from_bytes`.
///
/// # Safety
///
/// This routine is not safe because it permits callers to provide
/// arbitrary transitions with possibly incorrect state identifiers. While
/// the various serialization routines will never return an incorrect
/// DFA, there is no guarantee that the bytes provided here are correct.
/// While `from_bytes_unchecked` will still do several forms of basic
/// validation, this routine does not check that the transitions themselves
/// are correct. Given an incorrect transition table, it is possible for
/// the search routines to access out-of-bounds memory because of explicit
/// bounds check elision.
///
/// # Example
///
/// ```
/// use regex_automata::{dfa::{Automaton, sparse::DFA}, HalfMatch, Input};
///
/// let initial = DFA::new("foo[0-9]+")?;
/// let bytes = initial.to_bytes_native_endian();
/// // SAFETY: This is guaranteed to be safe since the bytes given come
/// // directly from a compatible serialization routine.
/// let dfa: DFA<&[u8]> = unsafe { DFA::from_bytes_unchecked(&bytes)?.0 };
///
/// let expected = Some(HalfMatch::must(0, 8));
/// assert_eq!(expected, dfa.try_search_fwd(&Input::new("foo12345"))?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub unsafe fn from_bytes_unchecked(
slice: &'a [u8],
) -> Result<(DFA<&'a [u8]>, usize), DeserializeError> {
let mut nr = 0;
nr += wire::read_label(&slice[nr..], LABEL)?;
nr += wire::read_endianness_check(&slice[nr..])?;
nr += wire::read_version(&slice[nr..], VERSION)?;
let _unused = wire::try_read_u32(&slice[nr..], "unused space")?;
nr += size_of::<u32>();
let (flags, nread) = Flags::from_bytes(&slice[nr..])?;
nr += nread;
let (tt, nread) = Transitions::from_bytes_unchecked(&slice[nr..])?;
nr += nread;
let (st, nread) = StartTable::from_bytes_unchecked(&slice[nr..])?;
nr += nread;
let (special, nread) = Special::from_bytes(&slice[nr..])?;
nr += nread;
if special.max.as_usize() >= tt.sparse().len() {
return Err(DeserializeError::generic(
"max should not be greater than or equal to sparse bytes",
));
}
let (quitset, nread) = ByteSet::from_bytes(&slice[nr..])?;
nr += nread;
// Prefilters don't support serialization, so they're always absent.
let pre = None;
Ok((DFA { tt, st, special, pre, quitset, flags }, nr))
}
}
impl<T: AsRef<[u8]>> fmt::Debug for DFA<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
writeln!(f, "sparse::DFA(")?;
for state in self.tt.states() {
fmt_state_indicator(f, self, state.id())?;
writeln!(f, "{:06?}: {:?}", state.id().as_usize(), state)?;
}
writeln!(f, "")?;
for (i, (start_id, anchored, sty)) in self.st.iter().enumerate() {
if i % self.st.stride == 0 {
match anchored {
Anchored::No => writeln!(f, "START-GROUP(unanchored)")?,
Anchored::Yes => writeln!(f, "START-GROUP(anchored)")?,
Anchored::Pattern(pid) => writeln!(
f,
"START_GROUP(pattern: {:?})",
pid.as_usize()
)?,
}
}
writeln!(f, " {:?} => {:06?}", sty, start_id.as_usize())?;
}
writeln!(f, "state length: {:?}", self.tt.state_len)?;
writeln!(f, "pattern length: {:?}", self.pattern_len())?;
writeln!(f, "flags: {:?}", self.flags)?;
writeln!(f, ")")?;
Ok(())
}
}
// SAFETY: We assert that our implementation of each method is correct.
unsafe impl<T: AsRef<[u8]>> Automaton for DFA<T> {
#[inline]
fn is_special_state(&self, id: StateID) -> bool {
self.special.is_special_state(id)
}
#[inline]
fn is_dead_state(&self, id: StateID) -> bool {
self.special.is_dead_state(id)
}
#[inline]
fn is_quit_state(&self, id: StateID) -> bool {
self.special.is_quit_state(id)
}
#[inline]
fn is_match_state(&self, id: StateID) -> bool {
self.special.is_match_state(id)
}
#[inline]
fn is_start_state(&self, id: StateID) -> bool {
self.special.is_start_state(id)
}
#[inline]
fn is_accel_state(&self, id: StateID) -> bool {
self.special.is_accel_state(id)
}
// This is marked as inline to help dramatically boost sparse searching,
// which decodes each state it enters to follow the next transition.
#[cfg_attr(feature = "perf-inline", inline(always))]
fn next_state(&self, current: StateID, input: u8) -> StateID {
let input = self.tt.classes.get(input);
self.tt.state(current).next(input)
}
#[inline]
unsafe fn next_state_unchecked(
&self,
current: StateID,
input: u8,
) -> StateID {
self.next_state(current, input)
}
#[inline]
fn next_eoi_state(&self, current: StateID) -> StateID {
self.tt.state(current).next_eoi()
}
#[inline]
fn pattern_len(&self) -> usize {
self.tt.pattern_len
}
#[inline]
fn match_len(&self, id: StateID) -> usize {
self.tt.state(id).pattern_len()
}
#[inline]
fn match_pattern(&self, id: StateID, match_index: usize) -> PatternID {
// This is an optimization for the very common case of a DFA with a
// single pattern. This conditional avoids a somewhat more costly path
// that finds the pattern ID from the state machine, which requires
// a bit of slicing/pointer-chasing. This optimization tends to only
// matter when matches are frequent.
if self.tt.pattern_len == 1 {
return PatternID::ZERO;
}
self.tt.state(id).pattern_id(match_index)
}
#[inline]
fn has_empty(&self) -> bool {
self.flags.has_empty
}
#[inline]
fn is_utf8(&self) -> bool {
self.flags.is_utf8
}
#[inline]
fn is_always_start_anchored(&self) -> bool {
self.flags.is_always_start_anchored
}
#[inline]
fn start_state_forward(
&self,
input: &Input<'_>,
) -> Result<StateID, MatchError> {
if !self.quitset.is_empty() && input.start() > 0 {
let offset = input.start() - 1;
let byte = input.haystack()[offset];
if self.quitset.contains(byte) {
return Err(MatchError::quit(byte, offset));
}
}
let start = self.st.start_map.fwd(&input);
self.st.start(input, start)
}
#[inline]
fn start_state_reverse(
&self,
input: &Input<'_>,
) -> Result<StateID, MatchError> {
if !self.quitset.is_empty() && input.end() < input.haystack().len() {
let offset = input.end();
let byte = input.haystack()[offset];
if self.quitset.contains(byte) {
return Err(MatchError::quit(byte, offset));
}
}
let start = self.st.start_map.rev(&input);
self.st.start(input, start)
}
#[inline]
fn universal_start_state(&self, mode: Anchored) -> Option<StateID> {
match mode {
Anchored::No => self.st.universal_start_unanchored,
Anchored::Yes => self.st.universal_start_anchored,
Anchored::Pattern(_) => None,
}
}
#[inline]
fn accelerator(&self, id: StateID) -> &[u8] {
self.tt.state(id).accelerator()
}
#[inline]
fn get_prefilter(&self) -> Option<&Prefilter> {
self.pre.as_ref()
}
}
/// The transition table portion of a sparse DFA.
///
/// The transition table is the core part of the DFA in that it describes how
/// to move from one state to another based on the input sequence observed.
///
/// Unlike a typical dense table based DFA, states in a sparse transition
/// table have variable size. That is, states with more transitions use more
/// space than states with fewer transitions. This means that finding the next
/// transition takes more work than with a dense DFA, but also typically uses
/// much less space.
#[derive(Clone)]
struct Transitions<T> {
/// The raw encoding of each state in this DFA.
///
/// Each state has the following information:
///
/// * A set of transitions to subsequent states. Transitions to the dead
/// state are omitted.
/// * If the state can be accelerated, then any additional accelerator
/// information.
/// * If the state is a match state, then the state contains all pattern
/// IDs that match when in that state.
///
/// To decode a state, use Transitions::state.
///
/// In practice, T is either Vec<u8> or &[u8].
sparse: T,
/// A set of equivalence classes, where a single equivalence class
/// represents a set of bytes that never discriminate between a match
/// and a non-match in the DFA. Each equivalence class corresponds to a
/// single character in this DFA's alphabet, where the maximum number of
/// characters is 257 (each possible value of a byte plus the special
/// EOI transition). Consequently, the number of equivalence classes
/// corresponds to the number of transitions for each DFA state. Note
/// though that the *space* used by each DFA state in the transition table
/// may be larger. The total space used by each DFA state is known as the
/// stride and is documented above.
///
/// The only time the number of equivalence classes is fewer than 257 is
/// if the DFA's kind uses byte classes which is the default. Equivalence
/// classes should generally only be disabled when debugging, so that
/// the transitions themselves aren't obscured. Disabling them has no
/// other benefit, since the equivalence class map is always used while
/// searching. In the vast majority of cases, the number of equivalence
/// classes is substantially smaller than 257, particularly when large
/// Unicode classes aren't used.
///
/// N.B. Equivalence classes aren't particularly useful in a sparse DFA
/// in the current implementation, since equivalence classes generally tend
/// to correspond to continuous ranges of bytes that map to the same
/// transition. So in a sparse DFA, equivalence classes don't really lead
/// to a space savings. In the future, it would be good to try and remove
/// them from sparse DFAs entirely, but requires a bit of work since sparse
/// DFAs are built from dense DFAs, which are in turn built on top of
/// equivalence classes.
classes: ByteClasses,
/// The total number of states in this DFA. Note that a DFA always has at
/// least one state---the dead state---even the empty DFA. In particular,
/// the dead state always has ID 0 and is correspondingly always the first
/// state. The dead state is never a match state.
state_len: usize,
/// The total number of unique patterns represented by these match states.
pattern_len: usize,
}
impl<'a> Transitions<&'a [u8]> {
unsafe fn from_bytes_unchecked(
mut slice: &'a [u8],
) -> Result<(Transitions<&'a [u8]>, usize), DeserializeError> {
let slice_start = slice.as_ptr().as_usize();
let (state_len, nr) =
wire::try_read_u32_as_usize(&slice, "state length")?;
slice = &slice[nr..];
let (pattern_len, nr) =
wire::try_read_u32_as_usize(&slice, "pattern length")?;
slice = &slice[nr..];
let (classes, nr) = ByteClasses::from_bytes(&slice)?;
slice = &slice[nr..];
let (len, nr) =
wire::try_read_u32_as_usize(&slice, "sparse transitions length")?;
slice = &slice[nr..];
wire::check_slice_len(slice, len, "sparse states byte length")?;
let sparse = &slice[..len];
slice = &slice[len..];
let trans = Transitions { sparse, classes, state_len, pattern_len };
Ok((trans, slice.as_ptr().as_usize() - slice_start))
}
}
impl<T: AsRef<[u8]>> Transitions<T> {
/// Writes a serialized form of this transition table to the buffer given.
/// If the buffer is too small, then an error is returned. To determine
/// how big the buffer must be, use `write_to_len`.
fn write_to<E: Endian>(
&self,
mut dst: &mut [u8],
) -> Result<usize, SerializeError> {
let nwrite = self.write_to_len();
if dst.len() < nwrite {
return Err(SerializeError::buffer_too_small(
"sparse transition table",
));
}
dst = &mut dst[..nwrite];
// write state length
E::write_u32(u32::try_from(self.state_len).unwrap(), dst);
dst = &mut dst[size_of::<u32>()..];
// write pattern length
E::write_u32(u32::try_from(self.pattern_len).unwrap(), dst);
dst = &mut dst[size_of::<u32>()..];
// write byte class map
let n = self.classes.write_to(dst)?;
dst = &mut dst[n..];
// write number of bytes in sparse transitions
E::write_u32(u32::try_from(self.sparse().len()).unwrap(), dst);
dst = &mut dst[size_of::<u32>()..];
// write actual transitions
let mut id = DEAD;
while id.as_usize() < self.sparse().len() {
let state = self.state(id);
let n = state.write_to::<E>(&mut dst)?;
dst = &mut dst[n..];
// The next ID is the offset immediately following `state`.
id = StateID::new(id.as_usize() + state.write_to_len()).unwrap();
}
Ok(nwrite)
}
/// Returns the number of bytes the serialized form of this transition
/// table will use.
fn write_to_len(&self) -> usize {
size_of::<u32>() // state length
+ size_of::<u32>() // pattern length
+ self.classes.write_to_len()
+ size_of::<u32>() // sparse transitions length
+ self.sparse().len()
}
/// Validates that every state ID in this transition table is valid.
///
/// That is, every state ID can be used to correctly index a state in this
/// table.
fn validate(&self, sp: &Special) -> Result<(), DeserializeError> {
// In order to validate everything, we not only need to make sure we
// can decode every state, but that every transition in every state
// points to a valid state. There are many duplicative transitions, so
// we record state IDs that we've verified so that we don't redo the
// decoding work.
//
// Except, when in no_std mode, we don't have dynamic memory allocation
// available to us, so we skip this optimization. It's not clear
// whether doing something more clever is worth it just yet. If you're
// profiling this code and need it to run faster, please file an issue.
//
// OK, so we also use this to record the set of valid state IDs. Since
// it is possible for a transition to point to an invalid state ID that
// still (somehow) deserializes to a valid state. So we need to make
// sure our transitions are limited to actually correct state IDs.
// The problem is, I'm not sure how to do this verification step in
// no-std no-alloc mode. I think we'd *have* to store the set of valid
// state IDs in the DFA itself. For now, we don't do this verification
// in no-std no-alloc mode. The worst thing that can happen is an
// incorrect result. But no panics or memory safety problems should
// result. Because we still do validate that the state itself is
// "valid" in the sense that everything it points to actually exists.
//
// ---AG
struct Seen {
#[cfg(feature = "alloc")]
set: alloc::collections::BTreeSet<StateID>,
#[cfg(not(feature = "alloc"))]
set: core::marker::PhantomData<StateID>,
}
#[cfg(feature = "alloc")]
impl Seen {
fn new() -> Seen {
Seen { set: alloc::collections::BTreeSet::new() }
}
fn insert(&mut self, id: StateID) {
self.set.insert(id);
}
fn contains(&self, id: &StateID) -> bool {
self.set.contains(id)
}
}
#[cfg(not(feature = "alloc"))]
impl Seen {
fn new() -> Seen {
Seen { set: core::marker::PhantomData }
}
fn insert(&mut self, _id: StateID) {}
fn contains(&self, _id: &StateID) -> bool {
false
}
}
let mut verified: Seen = Seen::new();
// We need to make sure that we decode the correct number of states.
// Otherwise, an empty set of transitions would validate even if the
// recorded state length is non-empty.
let mut len = 0;
// We can't use the self.states() iterator because it assumes the state
// encodings are valid. It could panic if they aren't.
let mut id = DEAD;
while id.as_usize() < self.sparse().len() {
// Before we even decode the state, we check that the ID itself
// is well formed. That is, if it's a special state then it must
// actually be a quit, dead, accel, match or start state.
if sp.is_special_state(id) {
let is_actually_special = sp.is_dead_state(id)
|| sp.is_quit_state(id)
|| sp.is_match_state(id)
|| sp.is_start_state(id)
|| sp.is_accel_state(id);
if !is_actually_special {
// This is kind of a cryptic error message...
return Err(DeserializeError::generic(
"found sparse state tagged as special but \
wasn't actually special",
));
}
}
let state = self.try_state(sp, id)?;
verified.insert(id);
// The next ID should be the offset immediately following `state`.
id = StateID::new(wire::add(
id.as_usize(),
state.write_to_len(),
"next state ID offset",
)?)
.map_err(|err| {
DeserializeError::state_id_error(err, "next state ID offset")
})?;
len += 1;
}
// Now that we've checked that all top-level states are correct and
// importantly, collected a set of valid state IDs, we have all the
// information we need to check that all transitions are correct too.
//
// Note that we can't use `valid_ids` to iterate because it will
// be empty in no-std no-alloc contexts. (And yes, that means our
// verification isn't quite as good.) We can use `self.states()`
// though at least, since we know that all states can at least be
// decoded and traversed correctly.
for state in self.states() {
// Check that all transitions in this state are correct.
for i in 0..state.ntrans {
let to = state.next_at(i);
// For no-alloc, we just check that the state can decode. It is
// technically possible that the state ID could still point to
// a non-existent state even if it decodes (fuzzing proved this
// to be true), but it shouldn't result in any memory unsafety
// or panics in non-debug mode.
#[cfg(not(feature = "alloc"))]
{
let _ = self.try_state(sp, to)?;
}
#[cfg(feature = "alloc")]
{
if !verified.contains(&to) {
return Err(DeserializeError::generic(
"found transition that points to a \
non-existent state",
));
}
}
}
}
if len != self.state_len {
return Err(DeserializeError::generic(
"mismatching sparse state length",
));
}
Ok(())
}
/// Converts these transitions to a borrowed value.
fn as_ref(&self) -> Transitions<&'_ [u8]> {
Transitions {
sparse: self.sparse(),
classes: self.classes.clone(),
state_len: self.state_len,
pattern_len: self.pattern_len,
}
}
/// Converts these transitions to an owned value.
#[cfg(feature = "alloc")]
fn to_owned(&self) -> Transitions<alloc::vec::Vec<u8>> {
Transitions {
sparse: self.sparse().to_vec(),
classes: self.classes.clone(),
state_len: self.state_len,
pattern_len: self.pattern_len,
}
}
/// Return a convenient representation of the given state.
///
/// This panics if the state is invalid.
///
/// This is marked as inline to help dramatically boost sparse searching,
/// which decodes each state it enters to follow the next transition. Other
/// functions involved are also inlined, which should hopefully eliminate
/// a lot of the extraneous decoding that is never needed just to follow
/// the next transition.
#[cfg_attr(feature = "perf-inline", inline(always))]
fn state(&self, id: StateID) -> State<'_> {
let mut state = &self.sparse()[id.as_usize()..];
let mut ntrans = wire::read_u16(&state).as_usize();
let is_match = (1 << 15) & ntrans != 0;
ntrans &= !(1 << 15);
state = &state[2..];
let (input_ranges, state) = state.split_at(ntrans * 2);
let (next, state) = state.split_at(ntrans * StateID::SIZE);
let (pattern_ids, state) = if is_match {
let npats = wire::read_u32(&state).as_usize();
state[4..].split_at(npats * 4)
} else {
(&[][..], state)
};
let accel_len = usize::from(state[0]);
let accel = &state[1..accel_len + 1];
State { id, is_match, ntrans, input_ranges, next, pattern_ids, accel }
}
/// Like `state`, but will return an error if the state encoding is
/// invalid. This is useful for verifying states after deserialization,
/// which is required for a safe deserialization API.
///
/// Note that this only verifies that this state is decodable and that
/// all of its data is consistent. It does not verify that its state ID
/// transitions point to valid states themselves, nor does it verify that
/// every pattern ID is valid.
fn try_state(
&self,
sp: &Special,
id: StateID,
) -> Result<State<'_>, DeserializeError> {
if id.as_usize() > self.sparse().len() {
return Err(DeserializeError::generic(
"invalid caller provided sparse state ID",
));
}
let mut state = &self.sparse()[id.as_usize()..];
// Encoding format starts with a u16 that stores the total number of
// transitions in this state.
let (mut ntrans, _) =
wire::try_read_u16_as_usize(state, "state transition length")?;
let is_match = ((1 << 15) & ntrans) != 0;
ntrans &= !(1 << 15);
state = &state[2..];
if ntrans > 257 || ntrans == 0 {
return Err(DeserializeError::generic(
"invalid transition length",
));
}
if is_match && !sp.is_match_state(id) {
return Err(DeserializeError::generic(
"state marked as match but not in match ID range",
));
} else if !is_match && sp.is_match_state(id) {
return Err(DeserializeError::generic(
"state in match ID range but not marked as match state",
));
}
// Each transition has two pieces: an inclusive range of bytes on which
// it is defined, and the state ID that those bytes transition to. The
// pairs come first, followed by a corresponding sequence of state IDs.
let input_ranges_len = ntrans.checked_mul(2).unwrap();
wire::check_slice_len(state, input_ranges_len, "sparse byte pairs")?;
let (input_ranges, state) = state.split_at(input_ranges_len);
// Every range should be of the form A-B, where A<=B.
for pair in input_ranges.chunks(2) {
let (start, end) = (pair[0], pair[1]);
if start > end {
return Err(DeserializeError::generic("invalid input range"));
}
}
// And now extract the corresponding sequence of state IDs. We leave
// this sequence as a &[u8] instead of a &[S] because sparse DFAs do
// not have any alignment requirements.
let next_len = ntrans
.checked_mul(self.id_len())
.expect("state size * #trans should always fit in a usize");
wire::check_slice_len(state, next_len, "sparse trans state IDs")?;
let (next, state) = state.split_at(next_len);
// We can at least verify that every state ID is in bounds.
for idbytes in next.chunks(self.id_len()) {
let (id, _) =
wire::read_state_id(idbytes, "sparse state ID in try_state")?;
wire::check_slice_len(
self.sparse(),
id.as_usize(),
"invalid sparse state ID",
)?;
}
// If this is a match state, then read the pattern IDs for this state.
// Pattern IDs is a u32-length prefixed sequence of native endian
// encoded 32-bit integers.
let (pattern_ids, state) = if is_match {
let (npats, nr) =
wire::try_read_u32_as_usize(state, "pattern ID length")?;
let state = &state[nr..];
if npats == 0 {
return Err(DeserializeError::generic(
"state marked as a match, but has no pattern IDs",
));
}
let pattern_ids_len =
wire::mul(npats, 4, "sparse pattern ID byte length")?;
wire::check_slice_len(
state,
pattern_ids_len,
"sparse pattern IDs",
)?;
let (pattern_ids, state) = state.split_at(pattern_ids_len);
for patbytes in pattern_ids.chunks(PatternID::SIZE) {
wire::read_pattern_id(
patbytes,
"sparse pattern ID in try_state",
)?;
}
(pattern_ids, state)
} else {
(&[][..], state)
};
// Now read this state's accelerator info. The first byte is the length
// of the accelerator, which is typically 0 (for no acceleration) but
// is no bigger than 3. The length indicates the number of bytes that
// follow, where each byte corresponds to a transition out of this
// state.
if state.is_empty() {
return Err(DeserializeError::generic("no accelerator length"));
}
let (accel_len, state) = (usize::from(state[0]), &state[1..]);
if accel_len > 3 {
return Err(DeserializeError::generic(
"sparse invalid accelerator length",
));
} else if accel_len == 0 && sp.is_accel_state(id) {
return Err(DeserializeError::generic(
"got no accelerators in state, but in accelerator ID range",
));
} else if accel_len > 0 && !sp.is_accel_state(id) {
return Err(DeserializeError::generic(
"state in accelerator ID range, but has no accelerators",
));
}
wire::check_slice_len(
state,
accel_len,
"sparse corrupt accelerator length",
)?;
let (accel, _) = (&state[..accel_len], &state[accel_len..]);
let state = State {
id,
is_match,
ntrans,
input_ranges,
next,
pattern_ids,
accel,
};
if sp.is_quit_state(state.next_at(state.ntrans - 1)) {
return Err(DeserializeError::generic(
"state with EOI transition to quit state is illegal",
));
}
Ok(state)
}
/// Return an iterator over all of the states in this DFA.
///
/// The iterator returned yields tuples, where the first element is the
/// state ID and the second element is the state itself.
fn states(&self) -> StateIter<'_, T> {
StateIter { trans: self, id: DEAD.as_usize() }
}
/// Returns the sparse transitions as raw bytes.
fn sparse(&self) -> &[u8] {
self.sparse.as_ref()
}
/// Returns the number of bytes represented by a single state ID.
fn id_len(&self) -> usize {
StateID::SIZE
}
/// Return the memory usage, in bytes, of these transitions.
///
/// This does not include the size of a `Transitions` value itself.
fn memory_usage(&self) -> usize {
self.sparse().len()
}
}
#[cfg(feature = "dfa-build")]
impl<T: AsMut<[u8]>> Transitions<T> {
/// Return a convenient mutable representation of the given state.
/// This panics if the state is invalid.
fn state_mut(&mut self, id: StateID) -> StateMut<'_> {
let mut state = &mut self.sparse_mut()[id.as_usize()..];
let mut ntrans = wire::read_u16(&state).as_usize();
let is_match = (1 << 15) & ntrans != 0;
ntrans &= !(1 << 15);
state = &mut state[2..];
let (input_ranges, state) = state.split_at_mut(ntrans * 2);
let (next, state) = state.split_at_mut(ntrans * StateID::SIZE);
let (pattern_ids, state) = if is_match {
let npats = wire::read_u32(&state).as_usize();
state[4..].split_at_mut(npats * 4)
} else {
(&mut [][..], state)
};
let accel_len = usize::from(state[0]);
let accel = &mut state[1..accel_len + 1];
StateMut {
id,
is_match,
ntrans,
input_ranges,
next,
pattern_ids,
accel,
}
}
/// Returns the sparse transitions as raw mutable bytes.
fn sparse_mut(&mut self) -> &mut [u8] {
self.sparse.as_mut()
}
}
/// The set of all possible starting states in a DFA.
///
/// See the eponymous type in the `dense` module for more details. This type
/// is very similar to `dense::StartTable`, except that its underlying
/// representation is `&[u8]` instead of `&[S]`. (The latter would require
/// sparse DFAs to be aligned, which is explicitly something we do not require
/// because we don't really need it.)
#[derive(Clone)]
struct StartTable<T> {
/// The initial start state IDs as a contiguous table of native endian
/// encoded integers, represented by `S`.
///
/// In practice, T is either Vec<u8> or &[u8] and has no alignment
/// requirements.
///
/// The first `2 * stride` (currently always 8) entries always correspond
/// to the starts states for the entire DFA, with the first 4 entries being
/// for unanchored searches and the second 4 entries being for anchored
/// searches. To keep things simple, we always use 8 entries even if the
/// `StartKind` is not both.
///
/// After that, there are `stride * patterns` state IDs, where `patterns`
/// may be zero in the case of a DFA with no patterns or in the case where
/// the DFA was built without enabling starting states for each pattern.
table: T,
/// The starting state configuration supported. When 'both', both
/// unanchored and anchored searches work. When 'unanchored', anchored
/// searches panic. When 'anchored', unanchored searches panic.
kind: StartKind,
/// The start state configuration for every possible byte.
start_map: StartByteMap,
/// The number of starting state IDs per pattern.
stride: usize,
/// The total number of patterns for which starting states are encoded.
/// This is `None` for DFAs that were built without start states for each
/// pattern. Thus, one cannot use this field to say how many patterns
/// are in the DFA in all cases. It is specific to how many patterns are
/// represented in this start table.
pattern_len: Option<usize>,
/// The universal starting state for unanchored searches. This is only
/// present when the DFA supports unanchored searches and when all starting
/// state IDs for an unanchored search are equivalent.
universal_start_unanchored: Option<StateID>,
/// The universal starting state for anchored searches. This is only
/// present when the DFA supports anchored searches and when all starting
/// state IDs for an anchored search are equivalent.
universal_start_anchored: Option<StateID>,
}
#[cfg(feature = "dfa-build")]
impl StartTable<Vec<u8>> {
fn new<T: AsRef<[u32]>>(
dfa: &dense::DFA<T>,
pattern_len: Option<usize>,
) -> StartTable<Vec<u8>> {
let stride = Start::len();
// This is OK since the only way we're here is if a dense DFA could be
// constructed successfully, which uses the same space.
let len = stride
.checked_mul(pattern_len.unwrap_or(0))
.unwrap()
.checked_add(stride.checked_mul(2).unwrap())
.unwrap()
.checked_mul(StateID::SIZE)
.unwrap();
StartTable {
table: vec![0; len],
kind: dfa.start_kind(),
start_map: dfa.start_map().clone(),
stride,
pattern_len,
universal_start_unanchored: dfa
.universal_start_state(Anchored::No),
universal_start_anchored: dfa.universal_start_state(Anchored::Yes),
}
}
fn from_dense_dfa<T: AsRef<[u32]>>(
dfa: &dense::DFA<T>,
remap: &[StateID],
) -> Result<StartTable<Vec<u8>>, BuildError> {
// Unless the DFA has start states compiled for each pattern, then
// as far as the starting state table is concerned, there are zero
// patterns to account for. It will instead only store starting states
// for the entire DFA.
let start_pattern_len = if dfa.starts_for_each_pattern() {
Some(dfa.pattern_len())
} else {
None
};
let mut sl = StartTable::new(dfa, start_pattern_len);
for (old_start_id, anchored, sty) in dfa.starts() {
let new_start_id = remap[dfa.to_index(old_start_id)];
sl.set_start(anchored, sty, new_start_id);
}
Ok(sl)
}
}
impl<'a> StartTable<&'a [u8]> {
unsafe fn from_bytes_unchecked(
mut slice: &'a [u8],
) -> Result<(StartTable<&'a [u8]>, usize), DeserializeError> {
let slice_start = slice.as_ptr().as_usize();
let (kind, nr) = StartKind::from_bytes(slice)?;
slice = &slice[nr..];
let (start_map, nr) = StartByteMap::from_bytes(slice)?;
slice = &slice[nr..];
let (stride, nr) =
wire::try_read_u32_as_usize(slice, "sparse start table stride")?;
slice = &slice[nr..];
if stride != Start::len() {
return Err(DeserializeError::generic(
"invalid sparse starting table stride",
));
}
let (maybe_pattern_len, nr) =
wire::try_read_u32_as_usize(slice, "sparse start table patterns")?;
slice = &slice[nr..];
let pattern_len = if maybe_pattern_len.as_u32() == u32::MAX {
None
} else {
Some(maybe_pattern_len)
};
if pattern_len.map_or(false, |len| len > PatternID::LIMIT) {
return Err(DeserializeError::generic(
"sparse invalid number of patterns",
));
}
let (universal_unanchored, nr) =
wire::try_read_u32(slice, "universal unanchored start")?;
slice = &slice[nr..];
let universal_start_unanchored = if universal_unanchored == u32::MAX {
None
} else {
Some(StateID::try_from(universal_unanchored).map_err(|e| {
DeserializeError::state_id_error(
e,
"universal unanchored start",
)
})?)
};
let (universal_anchored, nr) =
wire::try_read_u32(slice, "universal anchored start")?;
slice = &slice[nr..];
let universal_start_anchored = if universal_anchored == u32::MAX {
None
} else {
Some(StateID::try_from(universal_anchored).map_err(|e| {
DeserializeError::state_id_error(e, "universal anchored start")
})?)
};
let pattern_table_size = wire::mul(
stride,
pattern_len.unwrap_or(0),
"sparse invalid pattern length",
)?;
// Our start states always start with a single stride of start states
// for the entire automaton which permit it to match any pattern. What
// follows it are an optional set of start states for each pattern.
let start_state_len = wire::add(
wire::mul(2, stride, "start state stride too big")?,
pattern_table_size,
"sparse invalid 'any' pattern starts size",
)?;
let table_bytes_len = wire::mul(
start_state_len,
StateID::SIZE,
"sparse pattern table bytes length",
)?;
wire::check_slice_len(
slice,
table_bytes_len,
"sparse start ID table",
)?;
let table = &slice[..table_bytes_len];
slice = &slice[table_bytes_len..];
let sl = StartTable {
table,
kind,
start_map,
stride,
pattern_len,
universal_start_unanchored,
universal_start_anchored,
};
Ok((sl, slice.as_ptr().as_usize() - slice_start))
}
}
impl<T: AsRef<[u8]>> StartTable<T> {
fn write_to<E: Endian>(
&self,
mut dst: &mut [u8],
) -> Result<usize, SerializeError> {
let nwrite = self.write_to_len();
if dst.len() < nwrite {
return Err(SerializeError::buffer_too_small(
"sparse starting table ids",
));
}
dst = &mut dst[..nwrite];
// write start kind
let nw = self.kind.write_to::<E>(dst)?;
dst = &mut dst[nw..];
// write start byte map
let nw = self.start_map.write_to(dst)?;
dst = &mut dst[nw..];
// write stride
E::write_u32(u32::try_from(self.stride).unwrap(), dst);
dst = &mut dst[size_of::<u32>()..];
// write pattern length
E::write_u32(
u32::try_from(self.pattern_len.unwrap_or(0xFFFF_FFFF)).unwrap(),
dst,
);
dst = &mut dst[size_of::<u32>()..];
// write universal start unanchored state id, u32::MAX if absent
E::write_u32(
self.universal_start_unanchored
.map_or(u32::MAX, |sid| sid.as_u32()),
dst,
);
dst = &mut dst[size_of::<u32>()..];
// write universal start anchored state id, u32::MAX if absent
E::write_u32(
self.universal_start_anchored.map_or(u32::MAX, |sid| sid.as_u32()),
dst,
);
dst = &mut dst[size_of::<u32>()..];
// write start IDs
for (sid, _, _) in self.iter() {
E::write_u32(sid.as_u32(), dst);
dst = &mut dst[StateID::SIZE..];
}
Ok(nwrite)
}
/// Returns the number of bytes the serialized form of this transition
/// table will use.
fn write_to_len(&self) -> usize {
self.kind.write_to_len()
+ self.start_map.write_to_len()
+ size_of::<u32>() // stride
+ size_of::<u32>() // # patterns
+ size_of::<u32>() // universal unanchored start
+ size_of::<u32>() // universal anchored start
+ self.table().len()
}
/// Validates that every starting state ID in this table is valid.
///
/// That is, every starting state ID can be used to correctly decode a
/// state in the DFA's sparse transitions.
fn validate(
&self,
sp: &Special,
trans: &Transitions<T>,
) -> Result<(), DeserializeError> {
for (id, _, _) in self.iter() {
if sp.is_match_state(id) {
return Err(DeserializeError::generic(
"start states cannot be match states",
));
}
// Confirm that the start state points to a valid state.
let state = trans.try_state(sp, id)?;
// And like for the transition table, confirm that the transitions
// on all start states themselves point to a valid state.
//
// It'd probably be better to integrate this validation with the
// transition table, or otherwise store a sorted sequence of all
// valid state IDs in the sparse DFA itself. That way, we could
// check that every pointer to a state corresponds precisely to a
// correct and valid state.
for i in 0..state.ntrans {
let to = state.next_at(i);
let _ = trans.try_state(sp, to)?;
}
}
Ok(())
}
/// Converts this start list to a borrowed value.
fn as_ref(&self) -> StartTable<&'_ [u8]> {
StartTable {
table: self.table(),
kind: self.kind,
start_map: self.start_map.clone(),
stride: self.stride,
pattern_len: self.pattern_len,
universal_start_unanchored: self.universal_start_unanchored,
universal_start_anchored: self.universal_start_anchored,
}
}
/// Converts this start list to an owned value.
#[cfg(feature = "alloc")]
fn to_owned(&self) -> StartTable<alloc::vec::Vec<u8>> {
StartTable {
table: self.table().to_vec(),
kind: self.kind,
start_map: self.start_map.clone(),
stride: self.stride,
pattern_len: self.pattern_len,
universal_start_unanchored: self.universal_start_unanchored,
universal_start_anchored: self.universal_start_anchored,
}
}
/// Return the start state for the given index and pattern ID. If the
/// pattern ID is None, then the corresponding start state for the entire
/// DFA is returned. If the pattern ID is not None, then the corresponding
/// starting state for the given pattern is returned. If this start table
/// does not have individual starting states for each pattern, then this
/// panics.
fn start(
&self,
input: &Input<'_>,
start: Start,
) -> Result<StateID, MatchError> {
let start_index = start.as_usize();
let mode = input.get_anchored();
let index = match mode {
Anchored::No => {
if !self.kind.has_unanchored() {
return Err(MatchError::unsupported_anchored(mode));
}
start_index
}
Anchored::Yes => {
if !self.kind.has_anchored() {
return Err(MatchError::unsupported_anchored(mode));
}
self.stride + start_index
}
Anchored::Pattern(pid) => {
let len = match self.pattern_len {
None => {
return Err(MatchError::unsupported_anchored(mode))
}
Some(len) => len,
};
if pid.as_usize() >= len {
return Ok(DEAD);
}
(2 * self.stride)
+ (self.stride * pid.as_usize())
+ start_index
}
};
let start = index * StateID::SIZE;
// This OK since we're allowed to assume that the start table contains
// valid StateIDs.
Ok(wire::read_state_id_unchecked(&self.table()[start..]).0)
}
/// Return an iterator over all start IDs in this table.
fn iter(&self) -> StartStateIter<'_, T> {
StartStateIter { st: self, i: 0 }
}
/// Returns the total number of start state IDs in this table.
fn len(&self) -> usize {
self.table().len() / StateID::SIZE
}
/// Returns the table as a raw slice of bytes.
fn table(&self) -> &[u8] {
self.table.as_ref()
}
/// Return the memory usage, in bytes, of this start list.
///
/// This does not include the size of a `StartTable` value itself.
fn memory_usage(&self) -> usize {
self.table().len()
}
}
#[cfg(feature = "dfa-build")]
impl<T: AsMut<[u8]>> StartTable<T> {
/// Set the start state for the given index and pattern.
///
/// If the pattern ID or state ID are not valid, then this will panic.
fn set_start(&mut self, anchored: Anchored, start: Start, id: StateID) {
let start_index = start.as_usize();
let index = match anchored {
Anchored::No => start_index,
Anchored::Yes => self.stride + start_index,
Anchored::Pattern(pid) => {
let pid = pid.as_usize();
let len = self
.pattern_len
.expect("start states for each pattern enabled");
assert!(pid < len, "invalid pattern ID {:?}", pid);
self.stride
.checked_mul(pid)
.unwrap()
.checked_add(self.stride.checked_mul(2).unwrap())
.unwrap()
.checked_add(start_index)
.unwrap()
}
};
let start = index * StateID::SIZE;
let end = start + StateID::SIZE;
wire::write_state_id::<wire::NE>(
id,
&mut self.table.as_mut()[start..end],
);
}
}
/// An iterator over all state state IDs in a sparse DFA.
struct StartStateIter<'a, T> {
st: &'a StartTable<T>,
i: usize,
}
impl<'a, T: AsRef<[u8]>> Iterator for StartStateIter<'a, T> {
type Item = (StateID, Anchored, Start);
fn next(&mut self) -> Option<(StateID, Anchored, Start)> {
let i = self.i;
if i >= self.st.len() {
return None;
}
self.i += 1;
// This unwrap is okay since the stride of any DFA must always match
// the number of start state types.
let start_type = Start::from_usize(i % self.st.stride).unwrap();
let anchored = if i < self.st.stride {
Anchored::No
} else if i < (2 * self.st.stride) {
Anchored::Yes
} else {
let pid = (i - (2 * self.st.stride)) / self.st.stride;
Anchored::Pattern(PatternID::new(pid).unwrap())
};
let start = i * StateID::SIZE;
let end = start + StateID::SIZE;
let bytes = self.st.table()[start..end].try_into().unwrap();
// This is OK since we're allowed to assume that any IDs in this start
// table are correct and valid for this DFA.
let id = StateID::from_ne_bytes_unchecked(bytes);
Some((id, anchored, start_type))
}
}
impl<'a, T> fmt::Debug for StartStateIter<'a, T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("StartStateIter").field("i", &self.i).finish()
}
}
/// An iterator over all states in a sparse DFA.
///
/// This iterator yields tuples, where the first element is the state ID and
/// the second element is the state itself.
struct StateIter<'a, T> {
trans: &'a Transitions<T>,
id: usize,
}
impl<'a, T: AsRef<[u8]>> Iterator for StateIter<'a, T> {
type Item = State<'a>;
fn next(&mut self) -> Option<State<'a>> {
if self.id >= self.trans.sparse().len() {
return None;
}
let state = self.trans.state(StateID::new_unchecked(self.id));
self.id = self.id + state.write_to_len();
Some(state)
}
}
impl<'a, T> fmt::Debug for StateIter<'a, T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("StateIter").field("id", &self.id).finish()
}
}
/// A representation of a sparse DFA state that can be cheaply materialized
/// from a state identifier.
#[derive(Clone)]
struct State<'a> {
/// The identifier of this state.
id: StateID,
/// Whether this is a match state or not.
is_match: bool,
/// The number of transitions in this state.
ntrans: usize,
/// Pairs of input ranges, where there is one pair for each transition.
/// Each pair specifies an inclusive start and end byte range for the
/// corresponding transition.
input_ranges: &'a [u8],
/// Transitions to the next state. This slice contains native endian
/// encoded state identifiers, with `S` as the representation. Thus, there
/// are `ntrans * size_of::<S>()` bytes in this slice.
next: &'a [u8],
/// If this is a match state, then this contains the pattern IDs that match
/// when the DFA is in this state.
///
/// This is a contiguous sequence of 32-bit native endian encoded integers.
pattern_ids: &'a [u8],
/// An accelerator for this state, if present. If this state has no
/// accelerator, then this is an empty slice. When non-empty, this slice
/// has length at most 3 and corresponds to the exhaustive set of bytes
/// that must be seen in order to transition out of this state.
accel: &'a [u8],
}
impl<'a> State<'a> {
/// Searches for the next transition given an input byte. If no such
/// transition could be found, then a dead state is returned.
///
/// This is marked as inline to help dramatically boost sparse searching,
/// which decodes each state it enters to follow the next transition.
#[cfg_attr(feature = "perf-inline", inline(always))]
fn next(&self, input: u8) -> StateID {
// This straight linear search was observed to be much better than
// binary search on ASCII haystacks, likely because a binary search
// visits the ASCII case last but a linear search sees it first. A
// binary search does do a little better on non-ASCII haystacks, but
// not by much. There might be a better trade off lurking here.
for i in 0..(self.ntrans - 1) {
let (start, end) = self.range(i);
if start <= input && input <= end {
return self.next_at(i);
}
// We could bail early with an extra branch: if input < b1, then
// we know we'll never find a matching transition. Interestingly,
// this extra branch seems to not help performance, or will even
// hurt it. It's likely very dependent on the DFA itself and what
// is being searched.
}
DEAD
}
/// Returns the next state ID for the special EOI transition.
fn next_eoi(&self) -> StateID {
self.next_at(self.ntrans - 1)
}
/// Returns the identifier for this state.
fn id(&self) -> StateID {
self.id
}
/// Returns the inclusive input byte range for the ith transition in this
/// state.
fn range(&self, i: usize) -> (u8, u8) {
(self.input_ranges[i * 2], self.input_ranges[i * 2 + 1])
}
/// Returns the next state for the ith transition in this state.
fn next_at(&self, i: usize) -> StateID {
let start = i * StateID::SIZE;
let end = start + StateID::SIZE;
let bytes = self.next[start..end].try_into().unwrap();
StateID::from_ne_bytes_unchecked(bytes)
}
/// Returns the pattern ID for the given match index. If the match index
/// is invalid, then this panics.
fn pattern_id(&self, match_index: usize) -> PatternID {
let start = match_index * PatternID::SIZE;
wire::read_pattern_id_unchecked(&self.pattern_ids[start..]).0
}
/// Returns the total number of pattern IDs for this state. This is always
/// zero when `is_match` is false.
fn pattern_len(&self) -> usize {
assert_eq!(0, self.pattern_ids.len() % 4);
self.pattern_ids.len() / 4
}
/// Return an accelerator for this state.
fn accelerator(&self) -> &'a [u8] {
self.accel
}
/// Write the raw representation of this state to the given buffer using
/// the given endianness.
fn write_to<E: Endian>(
&self,
mut dst: &mut [u8],
) -> Result<usize, SerializeError> {
let nwrite = self.write_to_len();
if dst.len() < nwrite {
return Err(SerializeError::buffer_too_small(
"sparse state transitions",
));
}
let ntrans =
if self.is_match { self.ntrans | (1 << 15) } else { self.ntrans };
E::write_u16(u16::try_from(ntrans).unwrap(), dst);
dst = &mut dst[size_of::<u16>()..];
dst[..self.input_ranges.len()].copy_from_slice(self.input_ranges);
dst = &mut dst[self.input_ranges.len()..];
for i in 0..self.ntrans {
E::write_u32(self.next_at(i).as_u32(), dst);
dst = &mut dst[StateID::SIZE..];
}
if self.is_match {
E::write_u32(u32::try_from(self.pattern_len()).unwrap(), dst);
dst = &mut dst[size_of::<u32>()..];
for i in 0..self.pattern_len() {
let pid = self.pattern_id(i);
E::write_u32(pid.as_u32(), dst);
dst = &mut dst[PatternID::SIZE..];
}
}
dst[0] = u8::try_from(self.accel.len()).unwrap();
dst[1..][..self.accel.len()].copy_from_slice(self.accel);
Ok(nwrite)
}
/// Return the total number of bytes that this state consumes in its
/// encoded form.
fn write_to_len(&self) -> usize {
let mut len = 2
+ (self.ntrans * 2)
+ (self.ntrans * StateID::SIZE)
+ (1 + self.accel.len());
if self.is_match {
len += size_of::<u32>() + self.pattern_ids.len();
}
len
}
}
impl<'a> fmt::Debug for State<'a> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut printed = false;
for i in 0..(self.ntrans - 1) {
let next = self.next_at(i);
if next == DEAD {
continue;
}
if printed {
write!(f, ", ")?;
}
let (start, end) = self.range(i);
if start == end {
write!(f, "{:?} => {:?}", DebugByte(start), next.as_usize())?;
} else {
write!(
f,
"{:?}-{:?} => {:?}",
DebugByte(start),
DebugByte(end),
next.as_usize(),
)?;
}
printed = true;
}
let eoi = self.next_at(self.ntrans - 1);
if eoi != DEAD {
if printed {
write!(f, ", ")?;
}
write!(f, "EOI => {:?}", eoi.as_usize())?;
}
Ok(())
}
}
/// A representation of a mutable sparse DFA state that can be cheaply
/// materialized from a state identifier.
#[cfg(feature = "dfa-build")]
struct StateMut<'a> {
/// The identifier of this state.
id: StateID,
/// Whether this is a match state or not.
is_match: bool,
/// The number of transitions in this state.
ntrans: usize,
/// Pairs of input ranges, where there is one pair for each transition.
/// Each pair specifies an inclusive start and end byte range for the
/// corresponding transition.
input_ranges: &'a mut [u8],
/// Transitions to the next state. This slice contains native endian
/// encoded state identifiers, with `S` as the representation. Thus, there
/// are `ntrans * size_of::<S>()` bytes in this slice.
next: &'a mut [u8],
/// If this is a match state, then this contains the pattern IDs that match
/// when the DFA is in this state.
///
/// This is a contiguous sequence of 32-bit native endian encoded integers.
pattern_ids: &'a [u8],
/// An accelerator for this state, if present. If this state has no
/// accelerator, then this is an empty slice. When non-empty, this slice
/// has length at most 3 and corresponds to the exhaustive set of bytes
/// that must be seen in order to transition out of this state.
accel: &'a mut [u8],
}
#[cfg(feature = "dfa-build")]
impl<'a> StateMut<'a> {
/// Sets the ith transition to the given state.
fn set_next_at(&mut self, i: usize, next: StateID) {
let start = i * StateID::SIZE;
let end = start + StateID::SIZE;
wire::write_state_id::<wire::NE>(next, &mut self.next[start..end]);
}
}
#[cfg(feature = "dfa-build")]
impl<'a> fmt::Debug for StateMut<'a> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let state = State {
id: self.id,
is_match: self.is_match,
ntrans: self.ntrans,
input_ranges: self.input_ranges,
next: self.next,
pattern_ids: self.pattern_ids,
accel: self.accel,
};
fmt::Debug::fmt(&state, f)
}
}
/*
/// A binary search routine specialized specifically to a sparse DFA state's
/// transitions. Specifically, the transitions are defined as a set of pairs
/// of input bytes that delineate an inclusive range of bytes. If the input
/// byte is in the range, then the corresponding transition is a match.
///
/// This binary search accepts a slice of these pairs and returns the position
/// of the matching pair (the ith transition), or None if no matching pair
/// could be found.
///
/// Note that this routine is not currently used since it was observed to
/// either decrease performance when searching ASCII, or did not provide enough
/// of a boost on non-ASCII haystacks to be worth it. However, we leave it here
/// for posterity in case we can find a way to use it.
///
/// In theory, we could use the standard library's search routine if we could
/// cast a `&[u8]` to a `&[(u8, u8)]`, but I don't believe this is currently
/// guaranteed to be safe and is thus UB (since I don't think the in-memory
/// representation of `(u8, u8)` has been nailed down). One could define a
/// repr(C) type, but the casting doesn't seem justified.
#[cfg_attr(feature = "perf-inline", inline(always))]
fn binary_search_ranges(ranges: &[u8], needle: u8) -> Option<usize> {
debug_assert!(ranges.len() % 2 == 0, "ranges must have even length");
debug_assert!(ranges.len() <= 512, "ranges should be short");
let (mut left, mut right) = (0, ranges.len() / 2);
while left < right {
let mid = (left + right) / 2;
let (b1, b2) = (ranges[mid * 2], ranges[mid * 2 + 1]);
if needle < b1 {
right = mid;
} else if needle > b2 {
left = mid + 1;
} else {
return Some(mid);
}
}
None
}
*/
#[cfg(all(test, feature = "syntax", feature = "dfa-build"))]
mod tests {
use crate::{
dfa::{dense::DFA, Automaton},
nfa::thompson,
Input, MatchError,
};
// See the analogous test in src/hybrid/dfa.rs and src/dfa/dense.rs.
#[test]
fn heuristic_unicode_forward() {
let dfa = DFA::builder()
.configure(DFA::config().unicode_word_boundary(true))
.thompson(thompson::Config::new().reverse(true))
.build(r"\b[0-9]+\b")
.unwrap()
.to_sparse()
.unwrap();
let input = Input::new("β123").range(2..);
let expected = MatchError::quit(0xB2, 1);
let got = dfa.try_search_fwd(&input);
assert_eq!(Err(expected), got);
let input = Input::new("123β").range(..3);
let expected = MatchError::quit(0xCE, 3);
let got = dfa.try_search_fwd(&input);
assert_eq!(Err(expected), got);
}
// See the analogous test in src/hybrid/dfa.rs and src/dfa/dense.rs.
#[test]
fn heuristic_unicode_reverse() {
let dfa = DFA::builder()
.configure(DFA::config().unicode_word_boundary(true))
.thompson(thompson::Config::new().reverse(true))
.build(r"\b[0-9]+\b")
.unwrap()
.to_sparse()
.unwrap();
let input = Input::new("β123").range(2..);
let expected = MatchError::quit(0xB2, 1);
let got = dfa.try_search_rev(&input);
assert_eq!(Err(expected), got);
let input = Input::new("123β").range(..3);
let expected = MatchError::quit(0xCE, 3);
let got = dfa.try_search_rev(&input);
assert_eq!(Err(expected), got);
}
}
|