       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

    use std::io;

    use automaton::Automaton;
    use buffer::Buffer;
    use dfa::{self, DFA};
    use error::Result;
    use nfa::{self, NFA};
    use prefilter::PrefilterState;
    use state_id::StateID;
    use Match;

    /// An automaton for searching multiple strings in linear time.
    ///
    /// The `AhoCorasick` type supports a few basic ways of constructing an
    /// automaton, including
    /// [`AhoCorasick::new`](struct.AhoCorasick.html#method.new)
    /// and
    /// [`AhoCorasick::new_auto_configured`](struct.AhoCorasick.html#method.new_auto_configured).
    /// However, there are a fair number of configurable options that can be set
    /// by using
    /// [`AhoCorasickBuilder`](struct.AhoCorasickBuilder.html)
    /// instead. Such options include, but are not limited to, how matches are
    /// determined, simple case insensitivity, whether to use a DFA or not and
    /// various knobs for controlling the space-vs-time trade offs taken when
    /// building the automaton.
    ///
    /// If you aren't sure where to start, try beginning with
    /// [`AhoCorasick::new_auto_configured`](struct.AhoCorasick.html#method.new_auto_configured).
    ///
    /// # Resource usage
    ///
    /// Aho-Corasick automatons are always constructed in `O(p)` time, where `p`
    /// is the combined length of all patterns being searched. With that said,
    /// building an automaton can be fairly costly because of high constant
    /// factors, particularly when enabling the
    /// [DFA](struct.AhoCorasickBuilder.html#method.dfa)
    /// option (which is disabled by default). For this reason, it's generally a
    /// good idea to build an automaton once and reuse it as much as possible.
    ///
    /// Aho-Corasick automatons can also use a fair bit of memory. To get a
    /// concrete idea of how much memory is being used, try using the
    /// [`AhoCorasick::heap_bytes`](struct.AhoCorasick.html#method.heap_bytes)
    /// method.
    ///
    /// # Examples
    ///
    /// This example shows how to search for occurrences of multiple patterns
    /// simultaneously in a case insensitive fashion. Each match includes the
    /// pattern that matched along with the byte offsets of the match.
    ///
    /// ```
    /// use aho_corasick::AhoCorasickBuilder;
    ///
    /// let patterns = &["apple", "maple", "snapple"];
    /// let haystack = "Nobody likes maple in their apple flavored Snapple.";
    ///
    /// let ac = AhoCorasickBuilder::new()
    ///     .ascii_case_insensitive(true)
    ///     .build(patterns);
    /// let mut matches = vec![];
    /// for mat in ac.find_iter(haystack) {
    ///     matches.push((mat.pattern(), mat.start(), mat.end()));
    /// }
    /// assert_eq!(matches, vec![
    ///     (1, 13, 18),
    ///     (0, 28, 33),
    ///     (2, 43, 50),
    /// ]);
    /// ```
    ///
    /// This example shows how to replace matches with some other string:
    ///
    /// ```
    /// use aho_corasick::AhoCorasick;
    ///
    /// let patterns = &["fox", "brown", "quick"];
    /// let haystack = "The quick brown fox.";
    /// let replace_with = &["sloth", "grey", "slow"];
    ///
    /// let ac = AhoCorasick::new(patterns);
    /// let result = ac.replace_all(haystack, replace_with);
    /// assert_eq!(result, "The slow grey sloth.");
    /// ```
    #[derive(Clone, Debug)]
    pub struct AhoCorasick<S: StateID = usize> {
        imp: Imp<S>,
        match_kind: MatchKind,
    }

    impl AhoCorasick {
        /// Create a new Aho-Corasick automaton using the default configuration.
        ///
        /// The default configuration optimizes for less space usage, but at the
        /// expense of longer search times. To change the configuration, use
        /// [`AhoCorasickBuilder`](struct.AhoCorasickBuilder.html)
        /// for fine-grained control, or
        /// [`AhoCorasick::new_auto_configured`](struct.AhoCorasick.html#method.new_auto_configured)
        /// for automatic configuration if you aren't sure which settings to pick.
        ///
        /// This uses the default
        /// [`MatchKind::Standard`](enum.MatchKind.html#variant.Standard)
        /// match semantics, which reports a match as soon as it is found. This
        /// corresponds to the standard match semantics supported by textbook
        /// descriptions of the Aho-Corasick algorithm.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::AhoCorasick;
        ///
        /// let ac = AhoCorasick::new(&[
        ///     "foo", "bar", "baz",
        /// ]);
        /// assert_eq!(Some(1), ac.find("xxx bar xxx").map(|m| m.pattern()));
        /// ```
        pub fn new<I, P>(
            patterns: I,
        ) -> AhoCorasick
        where I: IntoIterator<Item=P>,
              P: AsRef<[u8]>
        {
            AhoCorasickBuilder::new().build(patterns)
        }

        /// Build an Aho-Corasick automaton with an automatically determined
        /// configuration.
        ///
        /// Specifically, this requires a slice of patterns instead of an iterator
        /// since the configuration is determined by looking at the patterns before
        /// constructing the automaton. The idea here is to balance space and time
        /// automatically. That is, when searching a small number of patterns, this
        /// will attempt to use the fastest possible configuration since the total
        /// space required will be small anyway. As the number of patterns grows,
        /// this will fall back to slower configurations that use less space.
        ///
        /// If you want auto configuration but with match semantics different from
        /// the default `MatchKind::Standard`, then use
        /// [`AhoCorasickBuilder::auto_configure`](struct.AhoCorasickBuilder.html#method.auto_configure).
        ///
        /// # Examples
        ///
        /// Basic usage is just like `new`, except you must provide a slice:
        ///
        /// ```
        /// use aho_corasick::AhoCorasick;
        ///
        /// let ac = AhoCorasick::new_auto_configured(&[
        ///     "foo", "bar", "baz",
        /// ]);
        /// assert_eq!(Some(1), ac.find("xxx bar xxx").map(|m| m.pattern()));
        /// ```
        pub fn new_auto_configured<B>(
            patterns: &[B],
        ) -> AhoCorasick
        where B: AsRef<[u8]>
        {
            AhoCorasickBuilder::new().auto_configure(patterns).build(patterns)
        }
    }

    impl<S: StateID> AhoCorasick<S> {
        /// Returns true if and only if this automaton matches the haystack at any
        /// position.
        ///
        /// `haystack` may be any type that is cheaply convertible to a `&[u8]`.
        /// This includes, but is not limited to, `String`, `&str`, `Vec<u8>`, and
        /// `&[u8]` itself.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::AhoCorasick;
        ///
        /// let ac = AhoCorasick::new(&[
        ///     "foo", "bar", "quux", "baz",
        /// ]);
        /// assert!(ac.is_match("xxx bar xxx"));
        /// assert!(!ac.is_match("xxx qux xxx"));
        /// ```
        pub fn is_match<B: AsRef<[u8]>>(&self, haystack: B) -> bool {
            self.earliest_find(haystack).is_some()
        }

        /// Returns the location of the first detected match in `haystack`.
        ///
        /// This method has the same behavior regardless of the
        /// [`MatchKind`](enum.MatchKind.html)
        /// of this automaton.
        ///
        /// `haystack` may be any type that is cheaply convertible to a `&[u8]`.
        /// This includes, but is not limited to, `String`, `&str`, `Vec<u8>`, and
        /// `&[u8]` itself.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::AhoCorasick;
        ///
        /// let ac = AhoCorasick::new(&[
        ///     "abc", "b",
        /// ]);
        /// let mat = ac.earliest_find("abcd").expect("should have match");
        /// assert_eq!(1, mat.pattern());
        /// assert_eq!((1, 2), (mat.start(), mat.end()));
        /// ```
        pub fn earliest_find<B: AsRef<[u8]>>(&self, haystack: B) -> Option<Match> {
            let mut prestate = PrefilterState::new(self.max_pattern_len());
            let mut start = self.imp.start_state();
            self.imp.earliest_find_at(
                &mut prestate, haystack.as_ref(), 0, &mut start,
            )
        }

        /// Returns the location of the first match according to the match
        /// semantics that this automaton was constructed with.
        ///
        /// When using `MatchKind::Standard`, this corresponds precisely to the
        /// same behavior as
        /// [`earliest_find`](struct.AhoCorasick.html#method.earliest_find).
        /// Otherwise, match semantics correspond to either
        /// [leftmost-first](enum.MatchKind.html#variant.LeftmostFirst)
        /// or
        /// [leftmost-longest](enum.MatchKind.html#variant.LeftmostLongest).
        ///
        /// `haystack` may be any type that is cheaply convertible to a `&[u8]`.
        /// This includes, but is not limited to, `String`, `&str`, `Vec<u8>`, and
        /// `&[u8]` itself.
        ///
        /// # Examples
        ///
        /// Basic usage, with standard semantics:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["b", "abc", "abcd"];
        /// let haystack = "abcd";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::Standard) // default, not necessary
        ///     .build(patterns);
        /// let mat = ac.find(haystack).expect("should have a match");
        /// assert_eq!("b", &haystack[mat.start()..mat.end()]);
        /// ```
        ///
        /// Now with leftmost-first semantics:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["b", "abc", "abcd"];
        /// let haystack = "abcd";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostFirst)
        ///     .build(patterns);
        /// let mat = ac.find(haystack).expect("should have a match");
        /// assert_eq!("abc", &haystack[mat.start()..mat.end()]);
        /// ```
        ///
        /// And finally, leftmost-longest semantics:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["b", "abc", "abcd"];
        /// let haystack = "abcd";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostLongest)
        ///     .build(patterns);
        /// let mat = ac.find(haystack).expect("should have a match");
        /// assert_eq!("abcd", &haystack[mat.start()..mat.end()]);
        /// ```
        pub fn find<B: AsRef<[u8]>>(&self, haystack: B) -> Option<Match> {
            let mut prestate = PrefilterState::new(self.max_pattern_len());
            let mut start = self.imp.start_state();
            self.imp.find_at(&mut prestate, haystack.as_ref(), 0, &mut start)
        }

        /// Returns an iterator of non-overlapping matches, using the match
        /// semantics that this automaton was constructed with.
        ///
        /// `haystack` may be any type that is cheaply convertible to a `&[u8]`.
        /// This includes, but is not limited to, `String`, `&str`, `Vec<u8>`, and
        /// `&[u8]` itself.
        ///
        /// # Examples
        ///
        /// Basic usage, with standard semantics:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["append", "appendage", "app"];
        /// let haystack = "append the app to the appendage";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::Standard) // default, not necessary
        ///     .build(patterns);
        /// let matches: Vec<usize> = ac
        ///     .find_iter(haystack)
        ///     .map(|mat| mat.pattern())
        ///     .collect();
        /// assert_eq!(vec![2, 2, 2], matches);
        /// ```
        ///
        /// Now with leftmost-first semantics:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["append", "appendage", "app"];
        /// let haystack = "append the app to the appendage";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostFirst)
        ///     .build(patterns);
        /// let matches: Vec<usize> = ac
        ///     .find_iter(haystack)
        ///     .map(|mat| mat.pattern())
        ///     .collect();
        /// assert_eq!(vec![0, 2, 0], matches);
        /// ```
        ///
        /// And finally, leftmost-longest semantics:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["append", "appendage", "app"];
        /// let haystack = "append the app to the appendage";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostLongest)
        ///     .build(patterns);
        /// let matches: Vec<usize> = ac
        ///     .find_iter(haystack)
        ///     .map(|mat| mat.pattern())
        ///     .collect();
        /// assert_eq!(vec![0, 2, 1], matches);
        /// ```
        pub fn find_iter<'a, 'b, B: ?Sized + AsRef<[u8]>>(
            &'a self,
            haystack: &'b B,
        ) -> FindIter<'a, 'b, S> {
            FindIter::new(self, haystack.as_ref())
        }

        /// Returns an iterator of overlapping matches in the given `haystack`.
        ///
        /// Overlapping matches can _only_ be detected using
        /// `MatchKind::Standard` semantics. If this automaton was constructed with
        /// leftmost semantics, then this method will panic. To determine whether
        /// this will panic at runtime, use the
        /// [`AhoCorasick::supports_overlapping`](struct.AhoCorasick.html#method.supports_overlapping)
        /// method.
        ///
        /// `haystack` may be any type that is cheaply convertible to a `&[u8]`.
        /// This includes, but is not limited to, `String`, `&str`, `Vec<u8>`, and
        /// `&[u8]` itself.
        ///
        /// # Panics
        ///
        /// This panics when `AhoCorasick::supports_overlapping` returns `false`.
        /// That is, this panics when this automaton's match semantics are not
        /// `MatchKind::Standard`.
        ///
        /// # Examples
        ///
        /// Basic usage, with standard semantics:
        ///
        /// ```
        /// use aho_corasick::AhoCorasick;
        ///
        /// let patterns = &["append", "appendage", "app"];
        /// let haystack = "append the app to the appendage";
        ///
        /// let ac = AhoCorasick::new(patterns);
        /// let matches: Vec<usize> = ac
        ///     .find_overlapping_iter(haystack)
        ///     .map(|mat| mat.pattern())
        ///     .collect();
        /// assert_eq!(vec![2, 0, 2, 2, 0, 1], matches);
        /// ```
        pub fn find_overlapping_iter<'a, 'b, B: ?Sized + AsRef<[u8]>>(
            &'a self,
            haystack: &'b B,
        ) -> FindOverlappingIter<'a, 'b, S> {
            FindOverlappingIter::new(self, haystack.as_ref())
        }

        /// Replace all matches with a corresponding value in the `replace_with`
        /// slice given. Matches correspond to the same matches as reported by
        /// [`find_iter`](struct.AhoCorasick.html#method.find_iter).
        ///
        /// Replacements are determined by the index of the matching pattern.
        /// For example, if the pattern with index `2` is found, then it is
        /// replaced by `replace_with[2]`.
        ///
        /// # Panics
        ///
        /// This panics when `replace_with.len()` does not equal the total number
        /// of patterns that are matched by this automaton.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["append", "appendage", "app"];
        /// let haystack = "append the app to the appendage";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostFirst)
        ///     .build(patterns);
        /// let result = ac.replace_all(haystack, &["x", "y", "z"]);
        /// assert_eq!("x the z to the xage", result);
        /// ```
        pub fn replace_all<B>(
            &self,
            haystack: &str,
            replace_with: &[B],
        ) -> String
        where B: AsRef<str>
        {
            assert_eq!(
                replace_with.len(), self.pattern_count(),
                "replace_all requires a replacement for every pattern \
                 in the automaton"
            );
            let mut dst = String::with_capacity(haystack.len());
            self.replace_all_with(haystack, &mut dst, |mat, _, dst| {
                dst.push_str(replace_with[mat.pattern()].as_ref());
                true
            });
            dst
        }

        /// Replace all matches using raw bytes with a corresponding value in the
        /// `replace_with` slice given. Matches correspond to the same matches as
        /// reported by [`find_iter`](struct.AhoCorasick.html#method.find_iter).
        ///
        /// Replacements are determined by the index of the matching pattern.
        /// For example, if the pattern with index `2` is found, then it is
        /// replaced by `replace_with[2]`.
        ///
        /// # Panics
        ///
        /// This panics when `replace_with.len()` does not equal the total number
        /// of patterns that are matched by this automaton.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["append", "appendage", "app"];
        /// let haystack = b"append the app to the appendage";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostFirst)
        ///     .build(patterns);
        /// let result = ac.replace_all_bytes(haystack, &["x", "y", "z"]);
        /// assert_eq!(b"x the z to the xage".to_vec(), result);
        /// ```
        pub fn replace_all_bytes<B>(
            &self,
            haystack: &[u8],
            replace_with: &[B],
        ) -> Vec<u8>
        where B: AsRef<[u8]>
        {
            assert_eq!(
                replace_with.len(), self.pattern_count(),
                "replace_all_bytes requires a replacement for every pattern \
                 in the automaton"
            );
            let mut dst = Vec::with_capacity(haystack.len());
            self.replace_all_with_bytes(haystack, &mut dst, |mat, _, dst| {
                dst.extend(replace_with[mat.pattern()].as_ref());
                true
            });
            dst
        }

        /// Replace all matches using a closure called on each match.
        /// Matches correspond to the same matches as reported by
        /// [`find_iter`](struct.AhoCorasick.html#method.find_iter).
        ///
        /// The closure accepts three parameters: the match found, the text of
        /// the match and a string buffer with which to write the replaced text
        /// (if any). If the closure returns `true`, then it continues to the next
        /// match. If the closure returns false, then searching is stopped.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["append", "appendage", "app"];
        /// let haystack = "append the app to the appendage";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostFirst)
        ///     .build(patterns);
        /// let mut result = String::new();
        /// ac.replace_all_with(haystack, &mut result, |mat, _, dst| {
        ///     dst.push_str(&mat.pattern().to_string());
        ///     true
        /// });
        /// assert_eq!("0 the 2 to the 0age", result);
        /// ```
        pub fn replace_all_with<F>(
            &self,
            haystack: &str,
            dst: &mut String,
            mut replace_with: F,
        ) where F: FnMut(&Match, &str, &mut String) -> bool
        {
            let mut last_match = 0;
            for mat in self.find_iter(haystack) {
                dst.push_str(&haystack[last_match..mat.start()]);
                last_match = mat.end();
                replace_with(&mat, &haystack[mat.start()..mat.end()], dst);
            }
            dst.push_str(&haystack[last_match..]);
        }

        /// Replace all matches using raw bytes with a closure called on each
        /// match. Matches correspond to the same matches as reported by
        /// [`find_iter`](struct.AhoCorasick.html#method.find_iter).
        ///
        /// The closure accepts three parameters: the match found, the text of
        /// the match and a byte buffer with which to write the replaced text
        /// (if any). If the closure returns `true`, then it continues to the next
        /// match. If the closure returns false, then searching is stopped.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["append", "appendage", "app"];
        /// let haystack = b"append the app to the appendage";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostFirst)
        ///     .build(patterns);
        /// let mut result = vec![];
        /// ac.replace_all_with_bytes(haystack, &mut result, |mat, _, dst| {
        ///     dst.extend(mat.pattern().to_string().bytes());
        ///     true
        /// });
        /// assert_eq!(b"0 the 2 to the 0age".to_vec(), result);
        /// ```
        pub fn replace_all_with_bytes<F>(
            &self,
            haystack: &[u8],
            dst: &mut Vec<u8>,
            mut replace_with: F,
        ) where F: FnMut(&Match, &[u8], &mut Vec<u8>) -> bool
        {
            let mut last_match = 0;
            for mat in self.find_iter(haystack) {
                dst.extend(&haystack[last_match..mat.start()]);
                last_match = mat.end();
                replace_with(&mat, &haystack[mat.start()..mat.end()], dst);
            }
            dst.extend(&haystack[last_match..]);
        }

        /// Returns an iterator of non-overlapping matches in the given
        /// stream. Matches correspond to the same matches as reported by
        /// [`find_iter`](struct.AhoCorasick.html#method.find_iter).
        ///
        /// The matches yielded by this iterator use absolute position offsets in
        /// the stream given, where the first byte has index `0`. Matches are
        /// yieled until the stream is exhausted.
        ///
        /// Each item yielded by the iterator is an `io::Result<Match>`, where an
        /// error is yielded if there was a problem reading from the reader given.
        ///
        /// When searching a stream, an internal buffer is used. Therefore, callers
        /// should avoiding providing a buffered reader, if possible.
        ///
        /// Searching a stream requires that the automaton was built with
        /// `MatchKind::Standard` semantics. If this automaton was constructed
        /// with leftmost semantics, then this method will panic. To determine
        /// whether this will panic at runtime, use the
        /// [`AhoCorasick::supports_stream`](struct.AhoCorasick.html#method.supports_stream)
        /// method.
        ///
        /// # Memory usage
        ///
        /// In general, searching streams will use a constant amount of memory for
        /// its internal buffer. The one requirement is that the internal buffer
        /// must be at least the size of the longest possible match. In most use
        /// cases, the default buffer size will be much larger than any individual
        /// match.
        ///
        /// # Panics
        ///
        /// This panics when `AhoCorasick::supports_stream` returns `false`.
        /// That is, this panics when this automaton's match semantics are not
        /// `MatchKind::Standard`. This restriction may be lifted in the future.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::AhoCorasick;
        ///
        /// # fn example() -> Result<(), ::std::io::Error> {
        /// let patterns = &["append", "appendage", "app"];
        /// let haystack = "append the app to the appendage";
        ///
        /// let ac = AhoCorasick::new(patterns);
        /// let mut matches = vec![];
        /// for result in ac.stream_find_iter(haystack.as_bytes()) {
        ///     let mat = result?;
        ///     matches.push(mat.pattern());
        /// }
        /// assert_eq!(vec![2, 2, 2], matches);
        /// # Ok(()) }; example().unwrap()
        /// ```
        pub fn stream_find_iter<'a, R: io::Read>(
            &'a self,
            rdr: R,
        ) -> StreamFindIter<'a, R, S> {
            StreamFindIter::new(self, rdr)
        }

        /// Search for and replace all matches of this automaton in
        /// the given reader, and write the replacements to the given
        /// writer. Matches correspond to the same matches as reported by
        /// [`find_iter`](struct.AhoCorasick.html#method.find_iter).
        ///
        /// Replacements are determined by the index of the matching pattern.
        /// For example, if the pattern with index `2` is found, then it is
        /// replaced by `replace_with[2]`.
        ///
        /// After all matches are replaced, the writer is _not_ flushed.
        ///
        /// If there was a problem reading from the given reader or writing to the
        /// given writer, then the corresponding `io::Error` is returned and all
        /// replacement is stopped.
        ///
        /// When searching a stream, an internal buffer is used. Therefore, callers
        /// should avoiding providing a buffered reader, if possible. However,
        /// callers may want to provide a buffered writer.
        ///
        /// Searching a stream requires that the automaton was built with
        /// `MatchKind::Standard` semantics. If this automaton was constructed
        /// with leftmost semantics, then this method will panic. To determine
        /// whether this will panic at runtime, use the
        /// [`AhoCorasick::supports_stream`](struct.AhoCorasick.html#method.supports_stream)
        /// method.
        ///
        /// # Memory usage
        ///
        /// In general, searching streams will use a constant amount of memory for
        /// its internal buffer. The one requirement is that the internal buffer
        /// must be at least the size of the longest possible match. In most use
        /// cases, the default buffer size will be much larger than any individual
        /// match.
        ///
        /// # Panics
        ///
        /// This panics when `AhoCorasick::supports_stream` returns `false`.
        /// That is, this panics when this automaton's match semantics are not
        /// `MatchKind::Standard`. This restriction may be lifted in the future.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::AhoCorasick;
        ///
        /// # fn example() -> Result<(), ::std::io::Error> {
        /// let patterns = &["fox", "brown", "quick"];
        /// let haystack = "The quick brown fox.";
        /// let replace_with = &["sloth", "grey", "slow"];
        ///
        /// let ac = AhoCorasick::new(patterns);
        /// let mut result = vec![];
        /// ac.stream_replace_all(haystack.as_bytes(), &mut result, replace_with)?;
        /// assert_eq!(b"The slow grey sloth.".to_vec(), result);
        /// # Ok(()) }; example().unwrap()
        /// ```
        pub fn stream_replace_all<R, W, B>(
            &self,
            rdr: R,
            wtr: W,
            replace_with: &[B],
        ) -> io::Result<()>
        where R: io::Read,
              W: io::Write,
              B: AsRef<[u8]>
        {
            assert_eq!(
                replace_with.len(), self.pattern_count(),
                "stream_replace_all requires a replacement for every pattern \
                 in the automaton"
            );
            self.stream_replace_all_with(rdr, wtr, |mat, _, wtr| {
                wtr.write_all(replace_with[mat.pattern()].as_ref())
            })
        }

        /// Search the given reader and replace all matches of this automaton
        /// using the given closure. The result is written to the given
        /// writer. Matches correspond to the same matches as reported by
        /// [`find_iter`](struct.AhoCorasick.html#method.find_iter).
        ///
        /// The closure accepts three parameters: the match found, the text of
        /// the match and the writer with which to write the replaced text
        /// (if any). If the closure returns `true`, then it continues to the next
        /// match. If the closure returns false, then searching is stopped.
        ///
        /// After all matches are replaced, the writer is _not_ flushed.
        ///
        /// If there was a problem reading from the given reader or writing to the
        /// given writer, then the corresponding `io::Error` is returned and all
        /// replacement is stopped.
        ///
        /// When searching a stream, an internal buffer is used. Therefore, callers
        /// should avoiding providing a buffered reader, if possible. However,
        /// callers may want to provide a buffered writer.
        ///
        /// Searching a stream requires that the automaton was built with
        /// `MatchKind::Standard` semantics. If this automaton was constructed
        /// with leftmost semantics, then this method will panic. To determine
        /// whether this will panic at runtime, use the
        /// [`AhoCorasick::supports_stream`](struct.AhoCorasick.html#method.supports_stream)
        /// method.
        ///
        /// # Memory usage
        ///
        /// In general, searching streams will use a constant amount of memory for
        /// its internal buffer. The one requirement is that the internal buffer
        /// must be at least the size of the longest possible match. In most use
        /// cases, the default buffer size will be much larger than any individual
        /// match.
        ///
        /// # Panics
        ///
        /// This panics when `AhoCorasick::supports_stream` returns `false`.
        /// That is, this panics when this automaton's match semantics are not
        /// `MatchKind::Standard`. This restriction may be lifted in the future.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use std::io::Write;
        /// use aho_corasick::AhoCorasick;
        ///
        /// # fn example() -> Result<(), ::std::io::Error> {
        /// let patterns = &["fox", "brown", "quick"];
        /// let haystack = "The quick brown fox.";
        ///
        /// let ac = AhoCorasick::new(patterns);
        /// let mut result = vec![];
        /// ac.stream_replace_all_with(
        ///     haystack.as_bytes(),
        ///     &mut result,
        ///     |mat, _, wtr| {
        ///         wtr.write_all(mat.pattern().to_string().as_bytes())
        ///     },
        /// )?;
        /// assert_eq!(b"The 2 1 0.".to_vec(), result);
        /// # Ok(()) }; example().unwrap()
        /// ```
        pub fn stream_replace_all_with<R, W, F>(
            &self,
            rdr: R,
            mut wtr: W,
            mut replace_with: F,
        ) -> io::Result<()>
        where R: io::Read,
              W: io::Write,
              F: FnMut(&Match, &[u8], &mut W) -> io::Result<()>
        {
            let mut it = StreamChunkIter::new(self, rdr);
            while let Some(result) = it.next() {
                let chunk = result?;
                match chunk {
                    StreamChunk::NonMatch { bytes, .. } => {
                        wtr.write_all(bytes)?;
                    }
                    StreamChunk::Match { bytes, mat } => {
                        replace_with(&mat, bytes, &mut wtr)?;
                    }
                }
            }
            Ok(())
        }

        /// Returns the match kind used by this automaton.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasick, MatchKind};
        ///
        /// let ac = AhoCorasick::new(&[
        ///     "foo", "bar", "quux", "baz",
        /// ]);
        /// assert_eq!(&MatchKind::Standard, ac.match_kind());
        /// ```
        pub fn match_kind(&self) -> &MatchKind {
            self.imp.match_kind()
        }

        /// Returns the length of the longest pattern matched by this automaton.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::AhoCorasick;
        ///
        /// let ac = AhoCorasick::new(&[
        ///     "foo", "bar", "quux", "baz",
        /// ]);
        /// assert_eq!(4, ac.max_pattern_len());
        /// ```
        pub fn max_pattern_len(&self) -> usize {
            self.imp.max_pattern_len()
        }

        /// Return the total number of patterns matched by this automaton.
        ///
        /// This includes patterns that may never participate in a match. For
        /// example, if
        /// [`MatchKind::LeftmostFirst`](enum.MatchKind.html#variant.LeftmostFirst)
        /// match semantics are used, and the patterns `Sam` and `Samwise` were
        /// used to build the automaton, then `Samwise` can never participate in a
        /// match because `Sam` will always take priority.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::AhoCorasick;
        ///
        /// let ac = AhoCorasick::new(&[
        ///     "foo", "bar", "baz",
        /// ]);
        /// assert_eq!(3, ac.pattern_count());
        /// ```
        pub fn pattern_count(&self) -> usize {
            self.imp.pattern_count()
        }

        /// Returns true if and only if this automaton supports reporting
        /// overlapping matches.
        ///
        /// If this returns false and overlapping matches are requested, then it
        /// will result in a panic.
        ///
        /// Since leftmost matching is inherently incompatible with overlapping
        /// matches, only
        /// [`MatchKind::Standard`](enum.MatchKind.html#variant.Standard)
        /// supports overlapping matches. This is unlikely to change in the future.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::Standard)
        ///     .build(&["foo", "bar", "baz"]);
        /// assert!(ac.supports_overlapping());
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostFirst)
        ///     .build(&["foo", "bar", "baz"]);
        /// assert!(!ac.supports_overlapping());
        /// ```
        pub fn supports_overlapping(&self) -> bool {
            self.match_kind.supports_overlapping()
        }

        /// Returns true if and only if this automaton supports stream searching.
        ///
        /// If this returns false and stream searching (or replacing) is attempted,
        /// then it will result in a panic.
        ///
        /// Currently, only
        /// [`MatchKind::Standard`](enum.MatchKind.html#variant.Standard)
        /// supports streaming. This may be expanded in the future.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::Standard)
        ///     .build(&["foo", "bar", "baz"]);
        /// assert!(ac.supports_stream());
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostFirst)
        ///     .build(&["foo", "bar", "baz"]);
        /// assert!(!ac.supports_stream());
        /// ```
        pub fn supports_stream(&self) -> bool {
            self.match_kind.supports_stream()
        }

        /// Returns the total amount of heap used by this automaton, in units of
        /// bytes.
        ///
        /// # Examples
        ///
        /// This example shows the difference in heap usage between a few
        /// configurations:
        ///
        /// ```ignore
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .dfa(false) // default
        ///     .build(&["foo", "bar", "baz"]);
        /// assert_eq!(10_336, ac.heap_bytes());
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .dfa(false) // default
        ///     .ascii_case_insensitive(true)
        ///     .build(&["foo", "bar", "baz"]);
        /// assert_eq!(10_384, ac.heap_bytes());
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .dfa(true)
        ///     .byte_classes(false)
        ///     .build(&["foo", "bar", "baz"]);
        /// assert_eq!(20_768, ac.heap_bytes());
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .dfa(true)
        ///     .byte_classes(true) // default
        ///     .build(&["foo", "bar", "baz"]);
        /// assert_eq!(1_248, ac.heap_bytes());
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .dfa(true)
        ///     .ascii_case_insensitive(true)
        ///     .build(&["foo", "bar", "baz"]);
        /// assert_eq!(1_248, ac.heap_bytes());
        /// ```
        pub fn heap_bytes(&self) -> usize {
            match self.imp {
                Imp::NFA(ref nfa) => nfa.heap_bytes(),
                Imp::DFA(ref dfa) => dfa.heap_bytes(),
            }
        }
    }

    /// The internal implementation of Aho-Corasick, which is either an NFA or
    /// a DFA. The NFA is slower but uses less memory. The DFA is faster but uses
    /// more memory.
    #[derive(Clone, Debug)]
    enum Imp<S: StateID> {
        NFA(NFA<S>),
        DFA(DFA<S>),
    }

    impl<S: StateID> Imp<S> {
        /// Returns the type of match semantics implemented by this automaton.
        fn match_kind(&self) -> &MatchKind {
            match *self {
                Imp::NFA(ref nfa) => nfa.match_kind(),
                Imp::DFA(ref dfa) => dfa.match_kind(),
            }
        }

        /// Returns the identifier of the start state.
        fn start_state(&self) -> S {
            match *self {
                Imp::NFA(ref nfa) => nfa.start_state(),
                Imp::DFA(ref dfa) => dfa.start_state(),
            }
        }

        /// The length, in bytes, of the longest pattern in this automaton. This
        /// information is useful for maintaining correct buffer sizes when
        /// searching on streams.
        fn max_pattern_len(&self) -> usize {
            match *self {
                Imp::NFA(ref nfa) => nfa.max_pattern_len(),
                Imp::DFA(ref dfa) => dfa.max_pattern_len(),
            }
        }

        /// The total number of patterns added to this automaton. This includes
        /// patterns that may never match. The maximum matching pattern that can be
        /// reported is exactly one less than this number.
        fn pattern_count(&self) -> usize {
            match *self {
                Imp::NFA(ref nfa) => nfa.pattern_count(),
                Imp::DFA(ref dfa) => dfa.pattern_count(),
            }
        }

        #[inline(always)]
        fn overlapping_find_at(
            &self,
            prestate: &mut PrefilterState,
            haystack: &[u8],
            at: usize,
            state_id: &mut S,
            match_index: &mut usize,
        ) -> Option<Match> {
            match *self {
                Imp::NFA(ref nfa) => {
                    nfa.overlapping_find_at(
                        prestate, haystack, at, state_id, match_index,
                    )
                }
                Imp::DFA(ref dfa) => {
                    dfa.overlapping_find_at(
                        prestate, haystack, at, state_id, match_index,
                    )
                }
            }
        }

        #[inline(always)]
        fn earliest_find_at(
            &self,
            prestate: &mut PrefilterState,
            haystack: &[u8],
            at: usize,
            state_id: &mut S,
        ) -> Option<Match> {
            match *self {
                Imp::NFA(ref nfa) => {
                    nfa.earliest_find_at(prestate, haystack, at, state_id)
                }
                Imp::DFA(ref dfa) => {
                    dfa.earliest_find_at(prestate, haystack, at, state_id)
                }
            }
        }

        #[inline(always)]
        fn find_at(
            &self,
            prestate: &mut PrefilterState,
            haystack: &[u8],
            at: usize,
            state_id: &mut S,
        ) -> Option<Match> {
            match *self {
                Imp::NFA(ref nfa) => {
                    nfa.find_at(prestate, haystack, at, state_id)
                }
                Imp::DFA(ref dfa) => {
                    dfa.find_at(prestate, haystack, at, state_id)
                }
            }
        }
    }

    /// An iterator of non-overlapping matches in a particular haystack.
    ///
    /// This iterator yields matches according to the
    /// [`MatchKind`](enum.MatchKind.html)
    /// used by this automaton.
    ///
    /// This iterator is constructed via the
    /// [`AhoCorasick::find_iter`](struct.AhoCorasick.html#method.find_iter)
    /// method.
    ///
    /// The type variable `S` refers to the representation used for state
    /// identifiers. (By default, this is `usize`.)
    ///
    /// The lifetime `'a` refers to the lifetime of the `AhoCorasick` automaton.
    ///
    /// The lifetime `'b` refers to the lifetime of the haystack being searched.
    #[derive(Debug)]
    pub struct FindIter<'a, 'b, S: 'a + StateID> {
        fsm: &'a Imp<S>,
        prestate: PrefilterState,
        haystack: &'b [u8],
        pos: usize,
        start: S,
    }

    impl<'a, 'b, S: StateID> FindIter<'a, 'b, S> {
        fn new(ac: &'a AhoCorasick<S>, haystack: &'b [u8]) -> FindIter<'a, 'b, S> {
            let prestate = PrefilterState::new(ac.max_pattern_len());
            let start = ac.imp.start_state();
            FindIter { fsm: &ac.imp, prestate, haystack, pos: 0, start }
        }
    }

    impl<'a, 'b, S: StateID> Iterator for FindIter<'a, 'b, S> {
        type Item = Match;

        fn next(&mut self) -> Option<Match> {
            if self.pos > self.haystack.len() {
                return None;
            }
            let mut start = self.start;
            let result = self.fsm.find_at(
                &mut self.prestate, self.haystack, self.pos, &mut start,
            );
            let mat = match result {
                None => return None,
                Some(mat) => mat,
            };
            if mat.end() == self.pos {
                // If the automaton can match the empty string and if we found an
                // empty match, then we need to forcefully move the position.
                self.pos += 1;
            } else {
                self.pos = mat.end();
            }
            Some(mat)
        }
    }

    /// An iterator of overlapping matches in a particular haystack.
    ///
    /// This iterator will report all possible matches in a particular haystack,
    /// even when the matches overlap.
    ///
    /// This iterator is constructed via the
    /// [`AhoCorasick::find_overlapping_iter`](struct.AhoCorasick.html#method.find_overlapping_iter)
    /// method.
    ///
    /// The type variable `S` refers to the representation used for state
    /// identifiers. (By default, this is `usize`.)
    ///
    /// The lifetime `'a` refers to the lifetime of the `AhoCorasick` automaton.
    ///
    /// The lifetime `'b` refers to the lifetime of the haystack being searched.
    #[derive(Debug)]
    pub struct FindOverlappingIter<'a, 'b, S: 'a + StateID> {
        fsm: &'a Imp<S>,
        prestate: PrefilterState,
        haystack: &'b [u8],
        pos: usize,
        last_match_end: usize,
        state_id: S,
        match_index: usize,
    }

    impl<'a, 'b, S: StateID> FindOverlappingIter<'a, 'b, S> {
        fn new(
            ac: &'a AhoCorasick<S>,
            haystack: &'b [u8],
        ) -> FindOverlappingIter<'a, 'b, S> {
            assert!(
                ac.supports_overlapping(),
                "automaton does not support overlapping searches"
            );
            let prestate = PrefilterState::new(ac.max_pattern_len());
            FindOverlappingIter {
                fsm: &ac.imp,
                prestate,
                haystack,
                pos: 0,
                last_match_end: 0,
                state_id: ac.imp.start_state(),
                match_index: 0,
            }
        }
    }

    impl<'a, 'b, S: StateID> Iterator for FindOverlappingIter<'a, 'b, S> {
        type Item = Match;

        fn next(&mut self) -> Option<Match> {
            let result = self.fsm.overlapping_find_at(
                &mut self.prestate,
                self.haystack,
                self.pos,
                &mut self.state_id,
                &mut self.match_index,
            );
            match result {
                None => return None,
                Some(m) => {
                    self.pos = m.end();
                    Some(m)
                }
            }
        }
    }

    /// An iterator that reports Aho-Corasick matches in a stream.
    ///
    /// This iterator yields elements of type `io::Result<Match>`, where an error
    /// is reported if there was a problem reading from the underlying stream.
    /// The iterator terminates only when the underlying stream reaches `EOF`.
    ///
    /// This iterator is constructed via the
    /// [`AhoCorasick::stream_find_iter`](struct.AhoCorasick.html#method.stream_find_iter)
    /// method.
    ///
    /// The type variable `R` refers to the `io::Read` stream that is being read
    /// from.
    ///
    /// The type variable `S` refers to the representation used for state
    /// identifiers. (By default, this is `usize`.)
    ///
    /// The lifetime `'a` refers to the lifetime of the `AhoCorasick` automaton.
    #[derive(Debug)]
    pub struct StreamFindIter<'a, R, S: 'a + StateID> {
        it: StreamChunkIter<'a, R, S>,
    }

    impl<'a, R: io::Read, S: StateID> StreamFindIter<'a, R, S> {
        fn new(ac: &'a AhoCorasick<S>, rdr: R) -> StreamFindIter<'a, R, S> {
            StreamFindIter {
                it: StreamChunkIter::new(ac, rdr),
            }
        }
    }

    impl<'a, R: io::Read, S: StateID> Iterator for StreamFindIter<'a, R, S> {
        type Item = io::Result<Match>;

        fn next(&mut self) -> Option<io::Result<Match>> {
            loop {
                match self.it.next() {
                    None => return None,
                    Some(Err(err)) => return Some(Err(err)),
                    Some(Ok(StreamChunk::NonMatch { .. })) => {}
                    Some(Ok(StreamChunk::Match { mat, .. })) => {
                        return Some(Ok(mat));
                    }
                }
            }
        }
    }

    /// An iterator over chunks in an underlying reader. Each chunk either
    /// corresponds to non-matching bytes or matching bytes, but all bytes from
    /// the underlying reader are reported in sequence. There may be an arbitrary
    /// number of non-matching chunks before seeing a matching chunk.
    ///
    /// N.B. This does not actually implement Iterator because we need to borrow
    /// from the underlying reader. But conceptually, it's still an iterator.
    #[derive(Debug)]
    struct StreamChunkIter<'a, R, S: 'a + StateID> {
        /// The AC automaton.
        fsm: &'a Imp<S>,
        /// State associated with this automaton's prefilter. It is a heuristic
        /// for stopping the prefilter if it's deemed ineffective.
        prestate: PrefilterState,
        /// The source of bytes we read from.
        rdr: R,
        /// A fixed size buffer. This is what we actually search. There are some
        /// invariants around the buffer's size, namely, it must be big enough to
        /// contain the longest possible match.
        buf: Buffer,
        /// The ID of the FSM state we're currently in.
        state_id: S,
        /// The current position at which to start the next search in `buf`.
        search_pos: usize,
        /// The absolute position of `search_pos`, where `0` corresponds to the
        /// position of the first byte read from `rdr`.
        absolute_pos: usize,
        /// The ending position of the last StreamChunk that was returned to the
        /// caller. This position is used to determine whether we need to emit
        /// non-matching bytes before emitting a match.
        report_pos: usize,
        /// A match that should be reported on the next call.
        pending_match: Option<Match>,
        /// Enabled only when the automaton can match the empty string. When
        /// enabled, we need to execute one final search after consuming the
        /// reader to find the trailing empty match.
        has_empty_match_at_end: bool,
    }

    /// A single chunk yielded by the stream chunk iterator.
    ///
    /// The `'r` lifetime refers to the lifetime of the stream chunk iterator.
    #[derive(Debug)]
    enum StreamChunk<'r> {
        /// A chunk that does not contain any matches.
        NonMatch { bytes: &'r [u8], start: usize },
        /// A chunk that precisely contains a match.
        Match { bytes: &'r [u8], mat: Match },
    }

    impl<'a, R: io::Read, S: StateID> StreamChunkIter<'a, R, S> {
        fn new(ac: &'a AhoCorasick<S>, rdr: R) -> StreamChunkIter<'a, R, S> {
            assert!(
                ac.supports_stream(),
                "stream searching is only supported for Standard match semantics"
            );

            let prestate = PrefilterState::new(ac.max_pattern_len());
            let buf = Buffer::new(ac.imp.max_pattern_len());
            let state_id = ac.imp.start_state();
            StreamChunkIter {
                fsm: &ac.imp,
                prestate,
                rdr,
                buf,
                state_id,
                absolute_pos: 0,
                report_pos: 0,
                search_pos: 0,
                pending_match: None,
                has_empty_match_at_end: ac.is_match(""),
            }
        }

        fn next<'r>(&'r mut self) -> Option<io::Result<StreamChunk<'r>>> {
            loop {
                if let Some(mut mat) = self.pending_match.take() {
                    let bytes = &self.buf.buffer()[mat.start()..mat.end()];
                    self.report_pos = mat.end();
                    mat = mat.increment(self.absolute_pos);
                    return Some(Ok(StreamChunk::Match { bytes, mat }));
                }
                if self.search_pos >= self.buf.len() {
                    if let Some(end) = self.unreported() {
                        let bytes = &self.buf.buffer()[self.report_pos..end];
                        let start = self.absolute_pos + self.report_pos;
                        self.report_pos = end;
                        return Some(Ok(StreamChunk::NonMatch { bytes, start }));
                    }
                    if self.buf.len() >= self.buf.min_buffer_len() {
                        // This is the point at which we roll our buffer, which we
                        // only do if our buffer has at least the minimum amount of
                        // bytes in it. Before rolling, we update our various
                        // positions to be consistent with the buffer after it has
                        // been rolled.

                        self.report_pos -=
                            self.buf.len() - self.buf.min_buffer_len();
                        self.absolute_pos +=
                            self.search_pos - self.buf.min_buffer_len();
                        self.search_pos = self.buf.min_buffer_len();
                        self.buf.roll();
                    }
                    match self.buf.fill(&mut self.rdr) {
                        Err(err) => return Some(Err(err)),
                        Ok(false) => {
                            // We've hit EOF, but if there are still some
                            // unreported bytes remaining, return them now.
                            if self.report_pos < self.buf.len() {
                                let bytes = &self.buf.buffer()[self.report_pos..];
                                let start = self.absolute_pos + self.report_pos;
                                self.report_pos = self.buf.len();

                                let chunk = StreamChunk::NonMatch { bytes, start };
                                return Some(Ok(chunk));
                            } else {
                                // We've reported everything, but there might still
                                // be a match at the very last position.
                                if !self.has_empty_match_at_end {
                                    return None;
                                }
                                // fallthrough for another search to get trailing
                                // empty matches
                                self.has_empty_match_at_end = false;
                            }
                        }
                        Ok(true) => {}
                    }
                }
                let result = self.fsm.earliest_find_at(
                    &mut self.prestate,
                    self.buf.buffer(),
                    self.search_pos,
                    &mut self.state_id,
                );
                match result {
                    None => {
                        self.search_pos = self.buf.len();
                    }
                    Some(mat) => {
                        self.state_id = self.fsm.start_state();
                        if mat.end() == self.search_pos {
                            // If the automaton can match the empty string and if
                            // we found an empty match, then we need to forcefully
                            // move the position.
                            self.search_pos += 1;
                        } else {
                            self.search_pos = mat.end();
                        }
                        self.pending_match = Some(mat.clone());
                        if self.report_pos < mat.start() {
                            let bytes =
                                &self.buf.buffer()[self.report_pos..mat.start()];
                            let start = self.absolute_pos + self.report_pos;
                            self.report_pos = mat.start();

                            let chunk = StreamChunk::NonMatch { bytes, start };
                            return Some(Ok(chunk));
                        }
                    }
                }
            }
        }

        fn unreported(&self) -> Option<usize> {
            let end = self.search_pos.saturating_sub(self.buf.min_buffer_len());
            if self.report_pos < end {
                Some(end)
            } else {
                None
            }
        }
    }

    /// A builder for configuring an Aho-Corasick automaton.
    #[derive(Clone, Debug)]
    pub struct AhoCorasickBuilder {
        nfa_builder: nfa::Builder,
        dfa_builder: dfa::Builder,
        dfa: bool,
    }

    impl Default for AhoCorasickBuilder {
        fn default() -> AhoCorasickBuilder {
            AhoCorasickBuilder::new()
        }
    }

    impl AhoCorasickBuilder {
        /// Create a new builder for configuring an Aho-Corasick automaton.
        ///
        /// If you don't need fine grained configuration or aren't sure which knobs
        /// to set, try using
        /// [`AhoCorasick::new_auto_configured`](struct.AhoCorasick.html#method.new_auto_configured)
        /// instead.
        pub fn new() -> AhoCorasickBuilder {
            AhoCorasickBuilder {
                nfa_builder: nfa::Builder::new(),
                dfa_builder: dfa::Builder::new(),
                dfa: false,
            }
        }

        /// Build an Aho-Corasick automaton using the configuration set on this
        /// builder.
        ///
        /// A builder may be reused to create more automatons.
        ///
        /// This method will use the default for representing internal state
        /// identifiers, which is `usize`. This guarantees that building the
        /// automaton will succeed and is generally a good default, but can make
        /// the size of the automaton 2-8 times bigger than it needs to be,
        /// depending on your target platform.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::AhoCorasickBuilder;
        ///
        /// let patterns = &["foo", "bar", "baz"];
        /// let ac = AhoCorasickBuilder::new()
        ///     .build(patterns);
        /// assert_eq!(Some(1), ac.find("xxx bar xxx").map(|m| m.pattern()));
        /// ```
        pub fn build<I, P>(
            &self,
            patterns: I,
        ) -> AhoCorasick
        where I: IntoIterator<Item=P>,
              P: AsRef<[u8]>
        {
            // The builder only returns an error if the chosen state ID
            // representation is too small to fit all of the given patterns. In
            // this case, since we fix the representation to usize, it will always
            // work because it's impossible to overflow usize since the underlying
            // storage would OOM long before that happens.
            self.build_with_size::<usize, I, P>(patterns)
                .expect("usize state ID type should always work")
        }

        /// Build an Aho-Corasick automaton using the configuration set on this
        /// builder with a specific state identifier representation. This only has
        /// an effect when the `dfa` option is enabled.
        ///
        /// Generally, the choices for a state identifier representation are
        /// `u8`, `u16`, `u32`, `u64` or `usize`, with `usize` being the default.
        /// The advantage of choosing a smaller state identifier representation
        /// is that the automaton produced will be smaller. This might be
        /// beneficial for just generally using less space, or might even allow it
        /// to fit more of the automaton in your CPU's cache, leading to overall
        /// better search performance.
        ///
        /// Unlike the standard `build` method, this can report an error if the
        /// state identifier representation cannot support the size of the
        /// automaton.
        ///
        /// Note that the state identifier representation is determined by the
        /// `S` type variable. This requires a type hint of some sort, either
        /// by specifying the return type or using the turbofish, e.g.,
        /// `build_with_size::<u16, _, _>(...)`.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasick, AhoCorasickBuilder};
        ///
        /// # fn example() -> Result<(), ::aho_corasick::Error> {
        /// let patterns = &["foo", "bar", "baz"];
        /// let ac: AhoCorasick<u8> = AhoCorasickBuilder::new()
        ///     .build_with_size(patterns)?;
        /// assert_eq!(Some(1), ac.find("xxx bar xxx").map(|m| m.pattern()));
        /// # Ok(()) }; example().unwrap()
        /// ```
        ///
        /// Or alternatively, with turbofish:
        ///
        /// ```
        /// use aho_corasick::AhoCorasickBuilder;
        ///
        /// # fn example() -> Result<(), ::aho_corasick::Error> {
        /// let patterns = &["foo", "bar", "baz"];
        /// let ac = AhoCorasickBuilder::new()
        ///     .build_with_size::<u8, _, _>(patterns)?;
        /// assert_eq!(Some(1), ac.find("xxx bar xxx").map(|m| m.pattern()));
        /// # Ok(()) }; example().unwrap()
        /// ```
        pub fn build_with_size<S, I, P>(
            &self,
            patterns: I,
        ) -> Result<AhoCorasick<S>>
        where S: StateID,
              I: IntoIterator<Item=P>,
              P: AsRef<[u8]>
        {
            let nfa = self.nfa_builder.build(patterns)?;
            let match_kind = nfa.match_kind().clone();
            let imp =
                if self.dfa {
                    let dfa = self.dfa_builder.build(&nfa)?;
                    Imp::DFA(dfa)
                } else {
                    Imp::NFA(nfa)
                };
            Ok(AhoCorasick { imp, match_kind })
        }

        /// Automatically configure the settings on this builder according to the
        /// patterns that will be used to construct the automaton.
        ///
        /// The idea here is to balance space and time automatically. That is, when
        /// searching a small number of patterns, this will attempt to use the
        /// fastest possible configuration since the total space required will be
        /// small anyway. As the number of patterns grows, this will fall back to
        /// slower configurations that use less space.
        ///
        /// This is guaranteed to never set `match_kind`, but any other option may
        /// be overridden.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::AhoCorasickBuilder;
        ///
        /// let patterns = &["foo", "bar", "baz"];
        /// let ac = AhoCorasickBuilder::new()
        ///     .auto_configure(patterns)
        ///     .build(patterns);
        /// assert_eq!(Some(1), ac.find("xxx bar xxx").map(|m| m.pattern()));
        /// ```
        pub fn auto_configure<B: AsRef<[u8]>>(
            &mut self,
            patterns: &[B],
        ) -> &mut AhoCorasickBuilder {
            // N.B. Currently we only use the length of `patterns` to make a
            // decision here, and could therefore ask for an `ExactSizeIterator`
            // instead. But it's conceivable that we might adapt this to look at
            // the total number of bytes, which would requires a second pass.
            //
            // The logic here is fairly rudimentary at the moment, but probably
            // OK. The idea here is to use the fastest thing possible for a small
            // number of patterns. That is, a DFA with no byte classes, since byte
            // classes require an extra indirection for every byte searched. With a
            // moderate number of patterns, we still want a DFA, but save on both
            // space and compilation time by enabling byte classes. Finally, fall
            // back to the slower but smaller NFA.
            if patterns.len() <= 100 {
                // N.B. Using byte classes can actually be faster by improving
                // locality, but this only really applies for multi-megabyte
                // automata (i.e., automata that don't fit in your CPU's cache).
                self.dfa(true).byte_classes(false);
            } else if patterns.len() <= 5000 {
                self.dfa(true);
            }
            self
        }

        /// Set the desired match semantics.
        ///
        /// The default is `MatchKind::Standard`, which corresponds to the match
        /// semantics supported by the standard textbook description of the
        /// Aho-Corasick algorithm. Namely, matches are reported as soon as they
        /// are found. Moreover, this is the only way to get overlapping matches
        /// or do stream searching.
        ///
        /// The other kinds of match semantics that are supported are
        /// `MatchKind::LeftmostFirst` and `MatchKind::LeftmostLongest`. The former
        /// corresponds to the match you would get if you were to try to match
        /// each pattern at each position in the haystack in the same order that
        /// you give to the automaton. That is, it returns the leftmost match
        /// corresponding the earliest pattern given to the automaton. The latter
        /// corresponds to finding the longest possible match among all leftmost
        /// matches.
        ///
        /// For more details on match semantics, see the
        /// [documentation for `MatchKind`](enum.MatchKind.html).
        ///
        /// # Examples
        ///
        /// In these examples, we demonstrate the differences between match
        /// semantics for a particular set of patterns in a specific order:
        /// `b`, `abc`, `abcd`.
        ///
        /// Standard semantics:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["b", "abc", "abcd"];
        /// let haystack = "abcd";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::Standard) // default, not necessary
        ///     .build(patterns);
        /// let mat = ac.find(haystack).expect("should have a match");
        /// assert_eq!("b", &haystack[mat.start()..mat.end()]);
        /// ```
        ///
        /// Leftmost-first semantics:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["b", "abc", "abcd"];
        /// let haystack = "abcd";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostFirst)
        ///     .build(patterns);
        /// let mat = ac.find(haystack).expect("should have a match");
        /// assert_eq!("abc", &haystack[mat.start()..mat.end()]);
        /// ```
        ///
        /// Leftmost-longest semantics:
        ///
        /// ```
        /// use aho_corasick::{AhoCorasickBuilder, MatchKind};
        ///
        /// let patterns = &["b", "abc", "abcd"];
        /// let haystack = "abcd";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .match_kind(MatchKind::LeftmostLongest)
        ///     .build(patterns);
        /// let mat = ac.find(haystack).expect("should have a match");
        /// assert_eq!("abcd", &haystack[mat.start()..mat.end()]);
        /// ```
        pub fn match_kind(&mut self, kind: MatchKind) -> &mut AhoCorasickBuilder {
            self.nfa_builder.match_kind(kind);
            self
        }

        /// Enable ASCII-aware case insensitive matching.
        ///
        /// When this option is enabled, searching will be performed without
        /// respect to case for ASCII letters (`a-z` and `A-Z`) only.
        ///
        /// Enabling this option does not change the search algorithm, but it may
        /// increase the size of the automaton.
        ///
        /// **NOTE:** In the future, support for full Unicode case insensitivity
        /// may be added, but ASCII case insensitivity is comparatively much
        /// simpler to add.
        ///
        /// # Examples
        ///
        /// Basic usage:
        ///
        /// ```
        /// use aho_corasick::AhoCorasickBuilder;
        ///
        /// let patterns = &["FOO", "bAr", "BaZ"];
        /// let haystack = "foo bar baz";
        ///
        /// let ac = AhoCorasickBuilder::new()
        ///     .ascii_case_insensitive(true)
        ///     .build(patterns);
        /// assert_eq!(3, ac.find_iter(haystack).count());
        /// ```
        pub fn ascii_case_insensitive(
            &mut self,
            yes: bool,
        ) -> &mut AhoCorasickBuilder {
            self.nfa_builder.ascii_case_insensitive(yes);
            self
        }

        /// Set the limit on how many NFA states use a dense representation for
        /// their transitions.
        ///
        /// A dense representation uses more space, but supports faster access to
        /// transitions at search time. Thus, this setting permits the control of a
        /// space vs time trade off when using the NFA variant of Aho-Corasick.
        ///
        /// This limit is expressed in terms of the depth of a state, i.e., the
        /// number of transitions from the starting state of the NFA. The idea is
        /// that most of the time searching will be spent near the starting state
        /// of the automaton, so states near the start state should use a dense
        /// representation. States further away from the start state would then use
        /// a sparse representation, which uses less space but is slower to access
        /// transitions at search time.
        ///
        /// By default, this is set to a low but non-zero number.
        ///
        /// This setting has no effect if the `dfa` option is enabled.
        pub fn dense_depth(&mut self, depth: usize) -> &mut AhoCorasickBuilder {
            self.nfa_builder.dense_depth(depth);
            self
        }

        /// Compile the standard Aho-Corasick automaton into a deterministic finite
        /// automaton (DFA).
        ///
        /// When this is disabled (which is the default), then a non-deterministic
        /// finite automaton (NFA) is used instead.
        ///
        /// The main benefit to a DFA is that it can execute searches more quickly
        /// than a DFA (perhaps 2-4 times as fast). The main drawback is that the
        /// DFA uses more space and can take much longer to build.
        ///
        /// Enabling this option does not change the time complexity for
        /// constructing the Aho-Corasick automaton (which is `O(p)` where
        /// `p` is the total number of patterns being compiled). Enabling this
        /// option does however reduce the time complexity of non-overlapping
        /// searches from `O(n + p)` to `O(n)`, where `n` is the length of the
        /// haystack.
        ///
        /// In general, it's a good idea to enable this if you're searching a
        /// small number of fairly short patterns (~1000), or if you want the
        /// fastest possible search without regard to compilation time or space
        /// usage.
        pub fn dfa(&mut self, yes: bool) -> &mut AhoCorasickBuilder {
            self.dfa = yes;
            self
        }

        /// Enable heuristic prefilter optimizations.
        ///
        /// When enabled, searching will attempt to quickly skip to match
        /// candidates using specialized literal search routines. A prefilter
        /// cannot always be used, and is generally treated as a heuristic. It
        /// can be useful to disable this if the prefilter is observed to be
        /// sub-optimal for a particular workload.
        ///
        /// This is enabled by default.
        pub fn prefilter(&mut self, yes: bool) -> &mut AhoCorasickBuilder {
            self.nfa_builder.prefilter(yes);
            self
        }

        /// Shrink the size of the transition alphabet by mapping bytes to their
        /// equivalence classes. This only has an effect when the `dfa` option is
        /// enabled.
        ///
        /// When enabled, each a DFA will use a map from all possible bytes
        /// to their corresponding equivalence class. Each equivalence class
        /// represents a set of bytes that does not discriminate between a match
        /// and a non-match in the DFA. For example, the patterns `bar` and `baz`
        /// have at least five equivalence classes: singleton sets of `b`, `a`, `r`
        /// and `z`, and a final set that contains every other byte.
        ///
        /// The advantage of this map is that the size of the transition table can
        /// be reduced drastically from `#states * 256 * sizeof(id)` to
        /// `#states * k * sizeof(id)` where `k` is the number of equivalence
        /// classes. As a result, total space usage can decrease substantially.
        /// Moreover, since a smaller alphabet is used, compilation becomes faster
        /// as well.
        ///
        /// The disadvantage of this map is that every byte searched must be
        /// passed through this map before it can be used to determine the next
        /// transition. This has a small match time performance cost. However, if
        /// the DFA is otherwise very large without byte classes, then using byte
        /// classes can greatly improve memory locality and thus lead to better
        /// overall performance.
        ///
        /// This option is enabled by default.
        pub fn byte_classes(&mut self, yes: bool) -> &mut AhoCorasickBuilder {
            self.dfa_builder.byte_classes(yes);
            self
        }

        /// Premultiply state identifiers in the transition table. This only has
        /// an effect when the `dfa` option is enabled.
        ///
        /// When enabled, state identifiers are premultiplied to point to their
        /// corresponding row in the transition table. That is, given the `i`th
        /// state, its corresponding premultiplied identifier is `i * k` where `k`
        /// is the alphabet size of the automaton. (The alphabet size is at most
        /// 256, but is in practice smaller if byte classes is enabled.)
        ///
        /// When state identifiers are not premultiplied, then the identifier of
        /// the `i`th state is `i`.
        ///
        /// The advantage of premultiplying state identifiers is that is saves a
        /// multiplication instruction per byte when searching with a DFA. This has
        /// been observed to lead to a 20% performance benefit in micro-benchmarks.
        ///
        /// The primary disadvantage of premultiplying state identifiers is
        /// that they require a larger integer size to represent. For example,
        /// if the DFA has 200 states, then its premultiplied form requires 16
        /// bits to represent every possible state identifier, where as its
        /// non-premultiplied form only requires 8 bits.
        ///
        /// This option is enabled by default.
        pub fn premultiply(&mut self, yes: bool) -> &mut AhoCorasickBuilder {
            self.dfa_builder.premultiply(yes);
            self
        }
    }

    /// A knob for controlling the match semantics of an Aho-Corasick automaton.
    ///
    /// There are two generally different ways that Aho-Corasick automatons can
    /// report matches. The first way is the "standard" approach that results from
    /// implementing most textbook explanations of Aho-Corasick. The second way is
    /// to report only the leftmost non-overlapping matches. The leftmost approach
    /// is in turn split into two different ways of resolving ambiguous matches:
    /// leftmost-first and leftmost-longest.
    ///
    /// The `Standard` match kind is the default and is the only one that supports
    /// overlapping matches and stream searching. (Trying to find overlapping
    /// or streaming matches using leftmost match semantics will result in a
    /// panic.) The `Standard` match kind will report matches as they are seen.
    /// When searching for overlapping matches, then all possible matches are
    /// reported. When searching for non-overlapping matches, the first match seen
    /// is reported. For example, for non-overlapping matches, given the patterns
    /// `abcd` and `b` and the subject string `abcdef`, only a match for `b` is
    /// reported since it is detected first. The `abcd` match is never reported
    /// since it overlaps with the `b` match.
    ///
    /// In contrast, the leftmost match kind always prefers the leftmost match
    /// among all possible matches. Given the same example as above with `abcd` and
    /// `b` as patterns and `abcdef` as the subject string, the leftmost match is
    /// `abcd` since it begins before the `b` match, even though the `b` match is
    /// detected before the `abcd` match. In this case, the `b` match is not
    /// reported at all since it overlaps with the `abcd` match.
    ///
    /// The difference between leftmost-first and leftmost-longest is in how they
    /// resolve ambiguous matches when there are multiple leftmost matches to
    /// choose from. Leftmost-first always chooses the pattern that was provided
    /// earliest, where as leftmost-longest always chooses the longest matching
    /// pattern. For example, given the patterns `a` and `ab` and the subject
    /// string `ab`, the leftmost-first match is `a` but the leftmost-longest match
    /// is `ab`. Conversely, if the patterns were given in reverse order, i.e.,
    /// `ab` and `a`, then both the leftmost-first and leftmost-longest matches
    /// would be `ab`. Stated differently, the leftmost-first match depends on the
    /// order in which the patterns were given to the Aho-Corasick automaton.
    /// Because of that, when leftmost-first matching is used, if a pattern `A`
    /// that appears before a pattern `B` is a prefix of `B`, then it is impossible
    /// to ever observe a match of `B`.
    ///
    /// If you're not sure which match kind to pick, then stick with the standard
    /// kind, which is the default. In particular, if you need overlapping or
    /// streaming matches, then you _must_ use the standard kind. The leftmost
    /// kinds are useful in specific circumstances. For example, leftmost-first can
    /// be very useful as a way to implement match priority based on the order of
    /// patterns given and leftmost-longest can be useful for dictionary searching
    /// such that only the longest matching words are reported.
    ///
    /// # Relationship with regular expression alternations
    ///
    /// Understanding match semantics can be a little tricky, and one easy way
    /// to conceptualize non-overlapping matches from an Aho-Corasick automaton
    /// is to think about them as a simple alternation of literals in a regular
    /// expression. For example, let's say we wanted to match the strings
    /// `Sam` and `Samwise`, which would turn into the regex `Sam|Samwise`. It
    /// turns out that regular expression engines have two different ways of
    /// matching this alternation. The first way, leftmost-longest, is commonly
    /// found in POSIX compatible implementations of regular expressions (such as
    /// `grep`). The second way, leftmost-first, is commonly found in backtracking
    /// implementations such as Perl. (Some regex engines, such as RE2 and Rust's
    /// regex engine do not use backtracking, but still implement leftmost-first
    /// semantics in an effort to match the behavior of dominant backtracking
    /// regex engines such as those found in Perl, Ruby, Python, Javascript and
    /// PHP.)
    ///
    /// That is, when matching `Sam|Samwise` against `Samwise`, a POSIX regex
    /// will match `Samwise` because it is the longest possible match, but a
    /// Perl-like regex will match `Sam` since it appears earlier in the
    /// alternation. Indeed, the regex `Sam|Samwise` in a Perl-like regex engine
    /// will never match `Samwise` since `Sam` will always have higher priority.
    /// Conversely, matching the regex `Samwise|Sam` against `Samwise` will lead to
    /// a match of `Samwise` in both POSIX and Perl-like regexes since `Samwise` is
    /// still longest match, but it also appears earlier than `Sam`.
    ///
    /// The "standard" match semantics of Aho-Corasick generally don't correspond
    /// to the match semantics of any large group of regex implementations, so
    /// there's no direct analogy that can be made here. Standard match semantics
    /// are generally useful for overlapping matches, or if you just want to see
    /// matches as they are detected.
    ///
    /// The main conclusion to draw from this section is that the match semantics
    /// can be tweaked to precisely match either Perl-like regex alternations or
    /// POSIX regex alternations.
    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
    pub enum MatchKind {
        /// Use standard match semantics, which support overlapping matches. When
        /// used with non-overlapping matches, matches are reported as they are
        /// seen.
        Standard,
        /// Use leftmost-first match semantics, which reports leftmost matches.
        /// When there are multiple possible leftmost matches, the match
        /// corresponding to the pattern that appeared earlier when constructing
        /// the automaton is reported.
        ///
        /// This does **not** support overlapping matches or stream searching. If
        /// this match kind is used, attempting to find overlapping matches or
        /// stream matches will panic.
        LeftmostFirst,
        /// Use leftmost-longest match semantics, which reports leftmost matches.
        /// When there are multiple possible leftmost matches, the longest match
        /// is chosen.
        ///
        /// This does **not** support overlapping matches or stream searching. If
        /// this match kind is used, attempting to find overlapping matches or
        /// stream matches will panic.
        LeftmostLongest,
        /// Hints that destructuring should not be exhaustive.
        ///
        /// This enum may grow additional variants, so this makes sure clients
        /// don't count on exhaustive matching. (Otherwise, adding a new variant
        /// could break existing code.)
        #[doc(hidden)]
        __Nonexhaustive,
    }

    /// The default match kind is `MatchKind::Standard`.
    impl Default for MatchKind {
        fn default() -> MatchKind {
            MatchKind::Standard
        }
    }

    impl MatchKind {
        fn supports_overlapping(&self) -> bool {
            self.is_standard()
        }

        fn supports_stream(&self) -> bool {
            // TODO: It may be possible to support this. It's hard.
            //
            // See: https://github.com/rust-lang/regex/issues/425#issuecomment-471367838
            self.is_standard()
        }

        pub(crate) fn is_standard(&self) -> bool {
            *self == MatchKind::Standard
        }

        pub(crate) fn is_leftmost(&self) -> bool {
            *self == MatchKind::LeftmostFirst
            || *self == MatchKind::LeftmostLongest
        }

        pub(crate) fn is_leftmost_first(&self) -> bool {
            *self == MatchKind::LeftmostFirst
        }
    }

    #[cfg(test)]
    mod tests {
        use super::*;

        #[test]
        fn oibits() {
            use std::panic::{RefUnwindSafe, UnwindSafe};

            fn assert_send<T: Send>() {}
            fn assert_sync<T: Sync>() {}
            fn assert_unwind_safe<T: RefUnwindSafe + UnwindSafe>() {}

            assert_send::<AhoCorasick>();
            assert_sync::<AhoCorasick>();
            assert_unwind_safe::<AhoCorasick>();
            assert_send::<AhoCorasickBuilder>();
            assert_sync::<AhoCorasickBuilder>();
            assert_unwind_safe::<AhoCorasickBuilder>();
        }
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)