summaryrefslogtreecommitdiffstats
path: root/intl/icu/source/common/unisetspan.cpp
blob: 2e77dfd548aaa8eb0cb446c65094dd918c99da06 (plain)
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
// Copyright (C) 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
******************************************************************************
*
*   Copyright (C) 2007-2012, International Business Machines
*   Corporation and others.  All Rights Reserved.
*
******************************************************************************
*   file name:  unisetspan.cpp
*   encoding:   US-ASCII
*   tab size:   8 (not used)
*   indentation:4
*
*   created on: 2007mar01
*   created by: Markus W. Scherer
*/

#include "unicode/utypes.h"
#include "unicode/uniset.h"
#include "unicode/ustring.h"
#include "unicode/utf8.h"
#include "unicode/utf16.h"
#include "cmemory.h"
#include "uvector.h"
#include "unisetspan.h"

U_NAMESPACE_BEGIN

/*
 * List of offsets from the current position from where to try matching
 * a code point or a string.
 * Store offsets rather than indexes to simplify the code and use the same list
 * for both increments (in span()) and decrements (in spanBack()).
 *
 * Assumption: The maximum offset is limited, and the offsets that are stored
 * at any one time are relatively dense, that is, there are normally no gaps of
 * hundreds or thousands of offset values.
 *
 * The implementation uses a circular buffer of byte flags,
 * each indicating whether the corresponding offset is in the list.
 * This avoids inserting into a sorted list of offsets (or absolute indexes) and
 * physically moving part of the list.
 *
 * Note: In principle, the caller should setMaxLength() to the maximum of the
 * max string length and U16_LENGTH/U8_LENGTH to account for
 * "long" single code points.
 * However, this implementation uses at least a staticList with more than
 * U8_LENGTH entries anyway.
 *
 * Note: If maxLength were guaranteed to be no more than 32 or 64,
 * the list could be stored as bit flags in a single integer.
 * Rather than handling a circular buffer with a start list index,
 * the integer would simply be shifted when lower offsets are removed.
 * UnicodeSet does not have a limit on the lengths of strings.
 */
class OffsetList {  // Only ever stack-allocated, does not need to inherit UMemory.
public:
    OffsetList() : list(staticList), capacity(0), length(0), start(0) {}

    ~OffsetList() {
        if(list!=staticList) {
            uprv_free(list);
        }
    }

    // Call exactly once if the list is to be used.
    void setMaxLength(int32_t maxLength) {
        if(maxLength<=(int32_t)sizeof(staticList)) {
            capacity=(int32_t)sizeof(staticList);
        } else {
            UBool *l=(UBool *)uprv_malloc(maxLength);
            if(l!=NULL) {
                list=l;
                capacity=maxLength;
            }
        }
        uprv_memset(list, 0, capacity);
    }

    void clear() {
        uprv_memset(list, 0, capacity);
        start=length=0;
    }

    UBool isEmpty() const {
        return (UBool)(length==0);
    }

    // Reduce all stored offsets by delta, used when the current position
    // moves by delta.
    // There must not be any offsets lower than delta.
    // If there is an offset equal to delta, it is removed.
    // delta=[1..maxLength]
    void shift(int32_t delta) {
        int32_t i=start+delta;
        if(i>=capacity) {
            i-=capacity;
        }
        if(list[i]) {
            list[i]=FALSE;
            --length;
        }
        start=i;
    }

    // Add an offset. The list must not contain it yet.
    // offset=[1..maxLength]
    void addOffset(int32_t offset) {
        int32_t i=start+offset;
        if(i>=capacity) {
            i-=capacity;
        }
        list[i]=TRUE;
        ++length;
    }

    // offset=[1..maxLength]
    UBool containsOffset(int32_t offset) const {
        int32_t i=start+offset;
        if(i>=capacity) {
            i-=capacity;
        }
        return list[i];
    }

    // Find the lowest stored offset from a non-empty list, remove it,
    // and reduce all other offsets by this minimum.
    // Returns [1..maxLength].
    int32_t popMinimum() {
        // Look for the next offset in list[start+1..capacity-1].
        int32_t i=start, result;
        while(++i<capacity) {
            if(list[i]) {
                list[i]=FALSE;
                --length;
                result=i-start;
                start=i;
                return result;
            }
        }
        // i==capacity

        // Wrap around and look for the next offset in list[0..start].
        // Since the list is not empty, there will be one.
        result=capacity-start;
        i=0;
        while(!list[i]) {
            ++i;
        }
        list[i]=FALSE;
        --length;
        start=i;
        return result+=i;
    }

private:
    UBool *list;
    int32_t capacity;
    int32_t length;
    int32_t start;

    UBool staticList[16];
};

// Get the number of UTF-8 bytes for a UTF-16 (sub)string.
static int32_t
getUTF8Length(const UChar *s, int32_t length) {
    UErrorCode errorCode=U_ZERO_ERROR;
    int32_t length8=0;
    u_strToUTF8(NULL, 0, &length8, s, length, &errorCode);
    if(U_SUCCESS(errorCode) || errorCode==U_BUFFER_OVERFLOW_ERROR) {
        return length8;
    } else {
        // The string contains an unpaired surrogate.
        // Ignore this string.
        return 0;
    }
}

// Append the UTF-8 version of the string to t and return the appended UTF-8 length.
static int32_t
appendUTF8(const UChar *s, int32_t length, uint8_t *t, int32_t capacity) {
    UErrorCode errorCode=U_ZERO_ERROR;
    int32_t length8=0;
    u_strToUTF8((char *)t, capacity, &length8, s, length, &errorCode);
    if(U_SUCCESS(errorCode)) {
        return length8;
    } else {
        // The string contains an unpaired surrogate.
        // Ignore this string.
        return 0;
    }
}

static inline uint8_t
makeSpanLengthByte(int32_t spanLength) {
    // 0xfe==UnicodeSetStringSpan::LONG_SPAN
    return spanLength<0xfe ? (uint8_t)spanLength : (uint8_t)0xfe;
}

// Construct for all variants of span(), or only for any one variant.
// Initialize as little as possible, for single use.
UnicodeSetStringSpan::UnicodeSetStringSpan(const UnicodeSet &set,
                                           const UVector &setStrings,
                                           uint32_t which)
        : spanSet(0, 0x10ffff), pSpanNotSet(NULL), strings(setStrings),
          utf8Lengths(NULL), spanLengths(NULL), utf8(NULL),
          utf8Length(0),
          maxLength16(0), maxLength8(0),
          all((UBool)(which==ALL)) {
    spanSet.retainAll(set);
    if(which&NOT_CONTAINED) {
        // Default to the same sets.
        // addToSpanNotSet() will create a separate set if necessary.
        pSpanNotSet=&spanSet;
    }

    // Determine if the strings even need to be taken into account at all for span() etc.
    // If any string is relevant, then all strings need to be used for
    // span(longest match) but only the relevant ones for span(while contained).
    // TODO: Possible optimization: Distinguish CONTAINED vs. LONGEST_MATCH
    //   and do not store UTF-8 strings if !thisRelevant and CONTAINED.
    //   (Only store irrelevant UTF-8 strings for LONGEST_MATCH where they are relevant after all.)
    // Also count the lengths of the UTF-8 versions of the strings for memory allocation.
    int32_t stringsLength=strings.size();

    int32_t i, spanLength;
    UBool someRelevant=FALSE;
    for(i=0; i<stringsLength; ++i) {
        const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
        const UChar *s16=string.getBuffer();
        int32_t length16=string.length();
        UBool thisRelevant;
        spanLength=spanSet.span(s16, length16, USET_SPAN_CONTAINED);
        if(spanLength<length16) {  // Relevant string.
            someRelevant=thisRelevant=TRUE;
        } else {
            thisRelevant=FALSE;
        }
        if((which&UTF16) && length16>maxLength16) {
            maxLength16=length16;
        }
        if((which&UTF8) && (thisRelevant || (which&CONTAINED))) {
            int32_t length8=getUTF8Length(s16, length16);
            utf8Length+=length8;
            if(length8>maxLength8) {
                maxLength8=length8;
            }
        }
    }
    if(!someRelevant) {
        maxLength16=maxLength8=0;
        return;
    }

    // Freeze after checking for the need to use strings at all because freezing
    // a set takes some time and memory which are wasted if there are no relevant strings.
    if(all) {
        spanSet.freeze();
    }

    uint8_t *spanBackLengths;
    uint8_t *spanUTF8Lengths;
    uint8_t *spanBackUTF8Lengths;

    // Allocate a block of meta data.
    int32_t allocSize;
    if(all) {
        // UTF-8 lengths, 4 sets of span lengths, UTF-8 strings.
        allocSize=stringsLength*(4+1+1+1+1)+utf8Length;
    } else {
        allocSize=stringsLength;  // One set of span lengths.
        if(which&UTF8) {
            // UTF-8 lengths and UTF-8 strings.
            allocSize+=stringsLength*4+utf8Length;
        }
    }
    if(allocSize<=(int32_t)sizeof(staticLengths)) {
        utf8Lengths=staticLengths;
    } else {
        utf8Lengths=(int32_t *)uprv_malloc(allocSize);
        if(utf8Lengths==NULL) {
            maxLength16=maxLength8=0;  // Prevent usage by making needsStringSpanUTF16/8() return FALSE.
            return;  // Out of memory.
        }
    }

    if(all) {
        // Store span lengths for all span() variants.
        spanLengths=(uint8_t *)(utf8Lengths+stringsLength);
        spanBackLengths=spanLengths+stringsLength;
        spanUTF8Lengths=spanBackLengths+stringsLength;
        spanBackUTF8Lengths=spanUTF8Lengths+stringsLength;
        utf8=spanBackUTF8Lengths+stringsLength;
    } else {
        // Store span lengths for only one span() variant.
        if(which&UTF8) {
            spanLengths=(uint8_t *)(utf8Lengths+stringsLength);
            utf8=spanLengths+stringsLength;
        } else {
            spanLengths=(uint8_t *)utf8Lengths;
        }
        spanBackLengths=spanUTF8Lengths=spanBackUTF8Lengths=spanLengths;
    }

    // Set the meta data and pSpanNotSet and write the UTF-8 strings.
    int32_t utf8Count=0;  // Count UTF-8 bytes written so far.

    for(i=0; i<stringsLength; ++i) {
        const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
        const UChar *s16=string.getBuffer();
        int32_t length16=string.length();
        spanLength=spanSet.span(s16, length16, USET_SPAN_CONTAINED);
        if(spanLength<length16) {  // Relevant string.
            if(which&UTF16) {
                if(which&CONTAINED) {
                    if(which&FWD) {
                        spanLengths[i]=makeSpanLengthByte(spanLength);
                    }
                    if(which&BACK) {
                        spanLength=length16-spanSet.spanBack(s16, length16, USET_SPAN_CONTAINED);
                        spanBackLengths[i]=makeSpanLengthByte(spanLength);
                    }
                } else /* not CONTAINED, not all, but NOT_CONTAINED */ {
                    spanLengths[i]=spanBackLengths[i]=0;  // Only store a relevant/irrelevant flag.
                }
            }
            if(which&UTF8) {
                uint8_t *s8=utf8+utf8Count;
                int32_t length8=appendUTF8(s16, length16, s8, utf8Length-utf8Count);
                utf8Count+=utf8Lengths[i]=length8;
                if(length8==0) {  // Irrelevant for UTF-8 because not representable in UTF-8.
                    spanUTF8Lengths[i]=spanBackUTF8Lengths[i]=(uint8_t)ALL_CP_CONTAINED;
                } else {  // Relevant for UTF-8.
                    if(which&CONTAINED) {
                        if(which&FWD) {
                            spanLength=spanSet.spanUTF8((const char *)s8, length8, USET_SPAN_CONTAINED);
                            spanUTF8Lengths[i]=makeSpanLengthByte(spanLength);
                        }
                        if(which&BACK) {
                            spanLength=length8-spanSet.spanBackUTF8((const char *)s8, length8, USET_SPAN_CONTAINED);
                            spanBackUTF8Lengths[i]=makeSpanLengthByte(spanLength);
                        }
                    } else /* not CONTAINED, not all, but NOT_CONTAINED */ {
                        spanUTF8Lengths[i]=spanBackUTF8Lengths[i]=0;  // Only store a relevant/irrelevant flag.
                    }
                }
            }
            if(which&NOT_CONTAINED) {
                // Add string start and end code points to the spanNotSet so that
                // a span(while not contained) stops before any string.
                UChar32 c;
                if(which&FWD) {
                    int32_t len=0;
                    U16_NEXT(s16, len, length16, c);
                    addToSpanNotSet(c);
                }
                if(which&BACK) {
                    int32_t len=length16;
                    U16_PREV(s16, 0, len, c);
                    addToSpanNotSet(c);
                }
            }
        } else {  // Irrelevant string.
            if(which&UTF8) {
                if(which&CONTAINED) {  // Only necessary for LONGEST_MATCH.
                    uint8_t *s8=utf8+utf8Count;
                    int32_t length8=appendUTF8(s16, length16, s8, utf8Length-utf8Count);
                    utf8Count+=utf8Lengths[i]=length8;
                } else {
                    utf8Lengths[i]=0;
                }
            }
            if(all) {
                spanLengths[i]=spanBackLengths[i]=
                    spanUTF8Lengths[i]=spanBackUTF8Lengths[i]=
                        (uint8_t)ALL_CP_CONTAINED;
            } else {
                // All spanXYZLengths pointers contain the same address.
                spanLengths[i]=(uint8_t)ALL_CP_CONTAINED;
            }
        }
    }

    // Finish.
    if(all) {
        pSpanNotSet->freeze();
    }
}

// Copy constructor. Assumes which==ALL for a frozen set.
UnicodeSetStringSpan::UnicodeSetStringSpan(const UnicodeSetStringSpan &otherStringSpan,
                                           const UVector &newParentSetStrings)
        : spanSet(otherStringSpan.spanSet), pSpanNotSet(NULL), strings(newParentSetStrings),
          utf8Lengths(NULL), spanLengths(NULL), utf8(NULL),
          utf8Length(otherStringSpan.utf8Length),
          maxLength16(otherStringSpan.maxLength16), maxLength8(otherStringSpan.maxLength8),
          all(TRUE) {
    if(otherStringSpan.pSpanNotSet==&otherStringSpan.spanSet) {
        pSpanNotSet=&spanSet;
    } else {
        pSpanNotSet=(UnicodeSet *)otherStringSpan.pSpanNotSet->clone();
    }

    // Allocate a block of meta data.
    // UTF-8 lengths, 4 sets of span lengths, UTF-8 strings.
    int32_t stringsLength=strings.size();
    int32_t allocSize=stringsLength*(4+1+1+1+1)+utf8Length;
    if(allocSize<=(int32_t)sizeof(staticLengths)) {
        utf8Lengths=staticLengths;
    } else {
        utf8Lengths=(int32_t *)uprv_malloc(allocSize);
        if(utf8Lengths==NULL) {
            maxLength16=maxLength8=0;  // Prevent usage by making needsStringSpanUTF16/8() return FALSE.
            return;  // Out of memory.
        }
    }

    spanLengths=(uint8_t *)(utf8Lengths+stringsLength);
    utf8=spanLengths+stringsLength*4;
    uprv_memcpy(utf8Lengths, otherStringSpan.utf8Lengths, allocSize);
}

UnicodeSetStringSpan::~UnicodeSetStringSpan() {
    if(pSpanNotSet!=NULL && pSpanNotSet!=&spanSet) {
        delete pSpanNotSet;
    }
    if(utf8Lengths!=NULL && utf8Lengths!=staticLengths) {
        uprv_free(utf8Lengths);
    }
}

void UnicodeSetStringSpan::addToSpanNotSet(UChar32 c) {
    if(pSpanNotSet==NULL || pSpanNotSet==&spanSet) {
        if(spanSet.contains(c)) {
            return;  // Nothing to do.
        }
        UnicodeSet *newSet=(UnicodeSet *)spanSet.cloneAsThawed();
        if(newSet==NULL) {
            return;  // Out of memory.
        } else {
            pSpanNotSet=newSet;
        }
    }
    pSpanNotSet->add(c);
}

// Compare strings without any argument checks. Requires length>0.
static inline UBool
matches16(const UChar *s, const UChar *t, int32_t length) {
    do {
        if(*s++!=*t++) {
            return FALSE;
        }
    } while(--length>0);
    return TRUE;
}

static inline UBool
matches8(const uint8_t *s, const uint8_t *t, int32_t length) {
    do {
        if(*s++!=*t++) {
            return FALSE;
        }
    } while(--length>0);
    return TRUE;
}

// Compare 16-bit Unicode strings (which may be malformed UTF-16)
// at code point boundaries.
// That is, each edge of a match must not be in the middle of a surrogate pair.
static inline UBool
matches16CPB(const UChar *s, int32_t start, int32_t limit, const UChar *t, int32_t length) {
    s+=start;
    limit-=start;
    return matches16(s, t, length) &&
           !(0<start && U16_IS_LEAD(s[-1]) && U16_IS_TRAIL(s[0])) &&
           !(length<limit && U16_IS_LEAD(s[length-1]) && U16_IS_TRAIL(s[length]));
}

// Does the set contain the next code point?
// If so, return its length; otherwise return its negative length.
static inline int32_t
spanOne(const UnicodeSet &set, const UChar *s, int32_t length) {
    UChar c=*s, c2;
    if(c>=0xd800 && c<=0xdbff && length>=2 && U16_IS_TRAIL(c2=s[1])) {
        return set.contains(U16_GET_SUPPLEMENTARY(c, c2)) ? 2 : -2;
    }
    return set.contains(c) ? 1 : -1;
}

static inline int32_t
spanOneBack(const UnicodeSet &set, const UChar *s, int32_t length) {
    UChar c=s[length-1], c2;
    if(c>=0xdc00 && c<=0xdfff && length>=2 && U16_IS_LEAD(c2=s[length-2])) {
        return set.contains(U16_GET_SUPPLEMENTARY(c2, c)) ? 2 : -2;
    }
    return set.contains(c) ? 1 : -1;
}

static inline int32_t
spanOneUTF8(const UnicodeSet &set, const uint8_t *s, int32_t length) {
    UChar32 c=*s;
    if((int8_t)c>=0) {
        return set.contains(c) ? 1 : -1;
    }
    // Take advantage of non-ASCII fastpaths in U8_NEXT_OR_FFFD().
    int32_t i=0;
    U8_NEXT_OR_FFFD(s, i, length, c);
    return set.contains(c) ? i : -i;
}

static inline int32_t
spanOneBackUTF8(const UnicodeSet &set, const uint8_t *s, int32_t length) {
    UChar32 c=s[length-1];
    if((int8_t)c>=0) {
        return set.contains(c) ? 1 : -1;
    }
    int32_t i=length-1;
    c=utf8_prevCharSafeBody(s, 0, &i, c, -3);
    length-=i;
    return set.contains(c) ? length : -length;
}

/*
 * Note: In span() when spanLength==0 (after a string match, or at the beginning
 * after an empty code point span) and in spanNot() and spanNotUTF8(),
 * string matching could use a binary search
 * because all string matches are done from the same start index.
 *
 * For UTF-8, this would require a comparison function that returns UTF-16 order.
 *
 * This optimization should not be necessary for normal UnicodeSets because
 * most sets have no strings, and most sets with strings have
 * very few very short strings.
 * For cases with many strings, it might be better to use a different API
 * and implementation with a DFA (state machine).
 */

/*
 * Algorithm for span(USET_SPAN_CONTAINED)
 *
 * Theoretical algorithm:
 * - Iterate through the string, and at each code point boundary:
 *   + If the code point there is in the set, then remember to continue after it.
 *   + If a set string matches at the current position, then remember to continue after it.
 *   + Either recursively span for each code point or string match,
 *     or recursively span for all but the shortest one and
 *     iteratively continue the span with the shortest local match.
 *   + Remember the longest recursive span (the farthest end point).
 *   + If there is no match at the current position, neither for the code point there
 *     nor for any set string, then stop and return the longest recursive span length.
 *
 * Optimized implementation:
 *
 * (We assume that most sets will have very few very short strings.
 * A span using a string-less set is extremely fast.)
 *
 * Create and cache a spanSet which contains all of the single code points
 * of the original set but none of its strings.
 *
 * - Start with spanLength=spanSet.span(USET_SPAN_CONTAINED).
 * - Loop:
 *   + Try to match each set string at the end of the spanLength.
 *     ~ Set strings that start with set-contained code points must be matched
 *       with a partial overlap because the recursive algorithm would have tried
 *       to match them at every position.
 *     ~ Set strings that entirely consist of set-contained code points
 *       are irrelevant for span(USET_SPAN_CONTAINED) because the
 *       recursive algorithm would continue after them anyway
 *       and find the longest recursive match from their end.
 *     ~ Rather than recursing, note each end point of a set string match.
 *   + If no set string matched after spanSet.span(), then return
 *     with where the spanSet.span() ended.
 *   + If at least one set string matched after spanSet.span(), then
 *     pop the shortest string match end point and continue
 *     the loop, trying to match all set strings from there.
 *   + If at least one more set string matched after a previous string match,
 *     then test if the code point after the previous string match is also
 *     contained in the set.
 *     Continue the loop with the shortest end point of either this code point
 *     or a matching set string.
 *   + If no more set string matched after a previous string match,
 *     then try another spanLength=spanSet.span(USET_SPAN_CONTAINED).
 *     Stop if spanLength==0, otherwise continue the loop.
 *
 * By noting each end point of a set string match,
 * the function visits each string position at most once and finishes
 * in linear time.
 *
 * The recursive algorithm may visit the same string position many times
 * if multiple paths lead to it and finishes in exponential time.
 */

/*
 * Algorithm for span(USET_SPAN_SIMPLE)
 *
 * Theoretical algorithm:
 * - Iterate through the string, and at each code point boundary:
 *   + If the code point there is in the set, then remember to continue after it.
 *   + If a set string matches at the current position, then remember to continue after it.
 *   + Continue from the farthest match position and ignore all others.
 *   + If there is no match at the current position,
 *     then stop and return the current position.
 *
 * Optimized implementation:
 *
 * (Same assumption and spanSet as above.)
 *
 * - Start with spanLength=spanSet.span(USET_SPAN_CONTAINED).
 * - Loop:
 *   + Try to match each set string at the end of the spanLength.
 *     ~ Set strings that start with set-contained code points must be matched
 *       with a partial overlap because the standard algorithm would have tried
 *       to match them earlier.
 *     ~ Set strings that entirely consist of set-contained code points
 *       must be matched with a full overlap because the longest-match algorithm
 *       would hide set string matches that end earlier.
 *       Such set strings need not be matched earlier inside the code point span
 *       because the standard algorithm would then have continued after
 *       the set string match anyway.
 *     ~ Remember the longest set string match (farthest end point) from the earliest
 *       starting point.
 *   + If no set string matched after spanSet.span(), then return
 *     with where the spanSet.span() ended.
 *   + If at least one set string matched, then continue the loop after the
 *     longest match from the earliest position.
 *   + If no more set string matched after a previous string match,
 *     then try another spanLength=spanSet.span(USET_SPAN_CONTAINED).
 *     Stop if spanLength==0, otherwise continue the loop.
 */

int32_t UnicodeSetStringSpan::span(const UChar *s, int32_t length, USetSpanCondition spanCondition) const {
    if(spanCondition==USET_SPAN_NOT_CONTAINED) {
        return spanNot(s, length);
    }
    int32_t spanLength=spanSet.span(s, length, USET_SPAN_CONTAINED);
    if(spanLength==length) {
        return length;
    }

    // Consider strings; they may overlap with the span.
    OffsetList offsets;
    if(spanCondition==USET_SPAN_CONTAINED) {
        // Use offset list to try all possibilities.
        offsets.setMaxLength(maxLength16);
    }
    int32_t pos=spanLength, rest=length-pos;
    int32_t i, stringsLength=strings.size();
    for(;;) {
        if(spanCondition==USET_SPAN_CONTAINED) {
            for(i=0; i<stringsLength; ++i) {
                int32_t overlap=spanLengths[i];
                if(overlap==ALL_CP_CONTAINED) {
                    continue;  // Irrelevant string.
                }
                const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
                const UChar *s16=string.getBuffer();
                int32_t length16=string.length();

                // Try to match this string at pos-overlap..pos.
                if(overlap>=LONG_SPAN) {
                    overlap=length16;
                    // While contained: No point matching fully inside the code point span.
                    U16_BACK_1(s16, 0, overlap);  // Length of the string minus the last code point.
                }
                if(overlap>spanLength) {
                    overlap=spanLength;
                }
                int32_t inc=length16-overlap;  // Keep overlap+inc==length16.
                for(;;) {
                    if(inc>rest) {
                        break;
                    }
                    // Try to match if the increment is not listed already.
                    if(!offsets.containsOffset(inc) && matches16CPB(s, pos-overlap, length, s16, length16)) {
                        if(inc==rest) {
                            return length;  // Reached the end of the string.
                        }
                        offsets.addOffset(inc);
                    }
                    if(overlap==0) {
                        break;
                    }
                    --overlap;
                    ++inc;
                }
            }
        } else /* USET_SPAN_SIMPLE */ {
            int32_t maxInc=0, maxOverlap=0;
            for(i=0; i<stringsLength; ++i) {
                int32_t overlap=spanLengths[i];
                // For longest match, we do need to try to match even an all-contained string
                // to find the match from the earliest start.

                const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
                const UChar *s16=string.getBuffer();
                int32_t length16=string.length();

                // Try to match this string at pos-overlap..pos.
                if(overlap>=LONG_SPAN) {
                    overlap=length16;
                    // Longest match: Need to match fully inside the code point span
                    // to find the match from the earliest start.
                }
                if(overlap>spanLength) {
                    overlap=spanLength;
                }
                int32_t inc=length16-overlap;  // Keep overlap+inc==length16.
                for(;;) {
                    if(inc>rest || overlap<maxOverlap) {
                        break;
                    }
                    // Try to match if the string is longer or starts earlier.
                    if( (overlap>maxOverlap || /* redundant overlap==maxOverlap && */ inc>maxInc) &&
                        matches16CPB(s, pos-overlap, length, s16, length16)
                    ) {
                        maxInc=inc;  // Longest match from earliest start.
                        maxOverlap=overlap;
                        break;
                    }
                    --overlap;
                    ++inc;
                }
            }

            if(maxInc!=0 || maxOverlap!=0) {
                // Longest-match algorithm, and there was a string match.
                // Simply continue after it.
                pos+=maxInc;
                rest-=maxInc;
                if(rest==0) {
                    return length;  // Reached the end of the string.
                }
                spanLength=0;  // Match strings from after a string match.
                continue;
            }
        }
        // Finished trying to match all strings at pos.

        if(spanLength!=0 || pos==0) {
            // The position is after an unlimited code point span (spanLength!=0),
            // not after a string match.
            // The only position where spanLength==0 after a span is pos==0.
            // Otherwise, an unlimited code point span is only tried again when no
            // strings match, and if such a non-initial span fails we stop.
            if(offsets.isEmpty()) {
                return pos;  // No strings matched after a span.
            }
            // Match strings from after the next string match.
        } else {
            // The position is after a string match (or a single code point).
            if(offsets.isEmpty()) {
                // No more strings matched after a previous string match.
                // Try another code point span from after the last string match.
                spanLength=spanSet.span(s+pos, rest, USET_SPAN_CONTAINED);
                if( spanLength==rest || // Reached the end of the string, or
                    spanLength==0       // neither strings nor span progressed.
                ) {
                    return pos+spanLength;
                }
                pos+=spanLength;
                rest-=spanLength;
                continue;  // spanLength>0: Match strings from after a span.
            } else {
                // Try to match only one code point from after a string match if some
                // string matched beyond it, so that we try all possible positions
                // and don't overshoot.
                spanLength=spanOne(spanSet, s+pos, rest);
                if(spanLength>0) {
                    if(spanLength==rest) {
                        return length;  // Reached the end of the string.
                    }
                    // Match strings after this code point.
                    // There cannot be any increments below it because UnicodeSet strings
                    // contain multiple code points.
                    pos+=spanLength;
                    rest-=spanLength;
                    offsets.shift(spanLength);
                    spanLength=0;
                    continue;  // Match strings from after a single code point.
                }
                // Match strings from after the next string match.
            }
        }
        int32_t minOffset=offsets.popMinimum();
        pos+=minOffset;
        rest-=minOffset;
        spanLength=0;  // Match strings from after a string match.
    }
}

int32_t UnicodeSetStringSpan::spanBack(const UChar *s, int32_t length, USetSpanCondition spanCondition) const {
    if(spanCondition==USET_SPAN_NOT_CONTAINED) {
        return spanNotBack(s, length);
    }
    int32_t pos=spanSet.spanBack(s, length, USET_SPAN_CONTAINED);
    if(pos==0) {
        return 0;
    }
    int32_t spanLength=length-pos;

    // Consider strings; they may overlap with the span.
    OffsetList offsets;
    if(spanCondition==USET_SPAN_CONTAINED) {
        // Use offset list to try all possibilities.
        offsets.setMaxLength(maxLength16);
    }
    int32_t i, stringsLength=strings.size();
    uint8_t *spanBackLengths=spanLengths;
    if(all) {
        spanBackLengths+=stringsLength;
    }
    for(;;) {
        if(spanCondition==USET_SPAN_CONTAINED) {
            for(i=0; i<stringsLength; ++i) {
                int32_t overlap=spanBackLengths[i];
                if(overlap==ALL_CP_CONTAINED) {
                    continue;  // Irrelevant string.
                }
                const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
                const UChar *s16=string.getBuffer();
                int32_t length16=string.length();

                // Try to match this string at pos-(length16-overlap)..pos-length16.
                if(overlap>=LONG_SPAN) {
                    overlap=length16;
                    // While contained: No point matching fully inside the code point span.
                    int32_t len1=0;
                    U16_FWD_1(s16, len1, overlap);
                    overlap-=len1;  // Length of the string minus the first code point.
                }
                if(overlap>spanLength) {
                    overlap=spanLength;
                }
                int32_t dec=length16-overlap;  // Keep dec+overlap==length16.
                for(;;) {
                    if(dec>pos) {
                        break;
                    }
                    // Try to match if the decrement is not listed already.
                    if(!offsets.containsOffset(dec) && matches16CPB(s, pos-dec, length, s16, length16)) {
                        if(dec==pos) {
                            return 0;  // Reached the start of the string.
                        }
                        offsets.addOffset(dec);
                    }
                    if(overlap==0) {
                        break;
                    }
                    --overlap;
                    ++dec;
                }
            }
        } else /* USET_SPAN_SIMPLE */ {
            int32_t maxDec=0, maxOverlap=0;
            for(i=0; i<stringsLength; ++i) {
                int32_t overlap=spanBackLengths[i];
                // For longest match, we do need to try to match even an all-contained string
                // to find the match from the latest end.

                const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
                const UChar *s16=string.getBuffer();
                int32_t length16=string.length();

                // Try to match this string at pos-(length16-overlap)..pos-length16.
                if(overlap>=LONG_SPAN) {
                    overlap=length16;
                    // Longest match: Need to match fully inside the code point span
                    // to find the match from the latest end.
                }
                if(overlap>spanLength) {
                    overlap=spanLength;
                }
                int32_t dec=length16-overlap;  // Keep dec+overlap==length16.
                for(;;) {
                    if(dec>pos || overlap<maxOverlap) {
                        break;
                    }
                    // Try to match if the string is longer or ends later.
                    if( (overlap>maxOverlap || /* redundant overlap==maxOverlap && */ dec>maxDec) &&
                        matches16CPB(s, pos-dec, length, s16, length16)
                    ) {
                        maxDec=dec;  // Longest match from latest end.
                        maxOverlap=overlap;
                        break;
                    }
                    --overlap;
                    ++dec;
                }
            }

            if(maxDec!=0 || maxOverlap!=0) {
                // Longest-match algorithm, and there was a string match.
                // Simply continue before it.
                pos-=maxDec;
                if(pos==0) {
                    return 0;  // Reached the start of the string.
                }
                spanLength=0;  // Match strings from before a string match.
                continue;
            }
        }
        // Finished trying to match all strings at pos.

        if(spanLength!=0 || pos==length) {
            // The position is before an unlimited code point span (spanLength!=0),
            // not before a string match.
            // The only position where spanLength==0 before a span is pos==length.
            // Otherwise, an unlimited code point span is only tried again when no
            // strings match, and if such a non-initial span fails we stop.
            if(offsets.isEmpty()) {
                return pos;  // No strings matched before a span.
            }
            // Match strings from before the next string match.
        } else {
            // The position is before a string match (or a single code point).
            if(offsets.isEmpty()) {
                // No more strings matched before a previous string match.
                // Try another code point span from before the last string match.
                int32_t oldPos=pos;
                pos=spanSet.spanBack(s, oldPos, USET_SPAN_CONTAINED);
                spanLength=oldPos-pos;
                if( pos==0 ||           // Reached the start of the string, or
                    spanLength==0       // neither strings nor span progressed.
                ) {
                    return pos;
                }
                continue;  // spanLength>0: Match strings from before a span.
            } else {
                // Try to match only one code point from before a string match if some
                // string matched beyond it, so that we try all possible positions
                // and don't overshoot.
                spanLength=spanOneBack(spanSet, s, pos);
                if(spanLength>0) {
                    if(spanLength==pos) {
                        return 0;  // Reached the start of the string.
                    }
                    // Match strings before this code point.
                    // There cannot be any decrements below it because UnicodeSet strings
                    // contain multiple code points.
                    pos-=spanLength;
                    offsets.shift(spanLength);
                    spanLength=0;
                    continue;  // Match strings from before a single code point.
                }
                // Match strings from before the next string match.
            }
        }
        pos-=offsets.popMinimum();
        spanLength=0;  // Match strings from before a string match.
    }
}

int32_t UnicodeSetStringSpan::spanUTF8(const uint8_t *s, int32_t length, USetSpanCondition spanCondition) const {
    if(spanCondition==USET_SPAN_NOT_CONTAINED) {
        return spanNotUTF8(s, length);
    }
    int32_t spanLength=spanSet.spanUTF8((const char *)s, length, USET_SPAN_CONTAINED);
    if(spanLength==length) {
        return length;
    }

    // Consider strings; they may overlap with the span.
    OffsetList offsets;
    if(spanCondition==USET_SPAN_CONTAINED) {
        // Use offset list to try all possibilities.
        offsets.setMaxLength(maxLength8);
    }
    int32_t pos=spanLength, rest=length-pos;
    int32_t i, stringsLength=strings.size();
    uint8_t *spanUTF8Lengths=spanLengths;
    if(all) {
        spanUTF8Lengths+=2*stringsLength;
    }
    for(;;) {
        const uint8_t *s8=utf8;
        int32_t length8;
        if(spanCondition==USET_SPAN_CONTAINED) {
            for(i=0; i<stringsLength; ++i) {
                length8=utf8Lengths[i];
                if(length8==0) {
                    continue;  // String not representable in UTF-8.
                }
                int32_t overlap=spanUTF8Lengths[i];
                if(overlap==ALL_CP_CONTAINED) {
                    s8+=length8;
                    continue;  // Irrelevant string.
                }

                // Try to match this string at pos-overlap..pos.
                if(overlap>=LONG_SPAN) {
                    overlap=length8;
                    // While contained: No point matching fully inside the code point span.
                    U8_BACK_1(s8, 0, overlap);  // Length of the string minus the last code point.
                }
                if(overlap>spanLength) {
                    overlap=spanLength;
                }
                int32_t inc=length8-overlap;  // Keep overlap+inc==length8.
                for(;;) {
                    if(inc>rest) {
                        break;
                    }
                    // Try to match if the increment is not listed already.
                    // Match at code point boundaries. (The UTF-8 strings were converted
                    // from UTF-16 and are guaranteed to be well-formed.)
                    if( !U8_IS_TRAIL(s[pos-overlap]) &&
                        !offsets.containsOffset(inc) &&
                        matches8(s+pos-overlap, s8, length8)
                        
                    ) {
                        if(inc==rest) {
                            return length;  // Reached the end of the string.
                        }
                        offsets.addOffset(inc);
                    }
                    if(overlap==0) {
                        break;
                    }
                    --overlap;
                    ++inc;
                }
                s8+=length8;
            }
        } else /* USET_SPAN_SIMPLE */ {
            int32_t maxInc=0, maxOverlap=0;
            for(i=0; i<stringsLength; ++i) {
                length8=utf8Lengths[i];
                if(length8==0) {
                    continue;  // String not representable in UTF-8.
                }
                int32_t overlap=spanUTF8Lengths[i];
                // For longest match, we do need to try to match even an all-contained string
                // to find the match from the earliest start.

                // Try to match this string at pos-overlap..pos.
                if(overlap>=LONG_SPAN) {
                    overlap=length8;
                    // Longest match: Need to match fully inside the code point span
                    // to find the match from the earliest start.
                }
                if(overlap>spanLength) {
                    overlap=spanLength;
                }
                int32_t inc=length8-overlap;  // Keep overlap+inc==length8.
                for(;;) {
                    if(inc>rest || overlap<maxOverlap) {
                        break;
                    }
                    // Try to match if the string is longer or starts earlier.
                    // Match at code point boundaries. (The UTF-8 strings were converted
                    // from UTF-16 and are guaranteed to be well-formed.)
                    if( !U8_IS_TRAIL(s[pos-overlap]) &&
                        (overlap>maxOverlap || /* redundant overlap==maxOverlap && */ inc>maxInc) &&
                        matches8(s+pos-overlap, s8, length8)
                        
                    ) {
                        maxInc=inc;  // Longest match from earliest start.
                        maxOverlap=overlap;
                        break;
                    }
                    --overlap;
                    ++inc;
                }
                s8+=length8;
            }

            if(maxInc!=0 || maxOverlap!=0) {
                // Longest-match algorithm, and there was a string match.
                // Simply continue after it.
                pos+=maxInc;
                rest-=maxInc;
                if(rest==0) {
                    return length;  // Reached the end of the string.
                }
                spanLength=0;  // Match strings from after a string match.
                continue;
            }
        }
        // Finished trying to match all strings at pos.

        if(spanLength!=0 || pos==0) {
            // The position is after an unlimited code point span (spanLength!=0),
            // not after a string match.
            // The only position where spanLength==0 after a span is pos==0.
            // Otherwise, an unlimited code point span is only tried again when no
            // strings match, and if such a non-initial span fails we stop.
            if(offsets.isEmpty()) {
                return pos;  // No strings matched after a span.
            }
            // Match strings from after the next string match.
        } else {
            // The position is after a string match (or a single code point).
            if(offsets.isEmpty()) {
                // No more strings matched after a previous string match.
                // Try another code point span from after the last string match.
                spanLength=spanSet.spanUTF8((const char *)s+pos, rest, USET_SPAN_CONTAINED);
                if( spanLength==rest || // Reached the end of the string, or
                    spanLength==0       // neither strings nor span progressed.
                ) {
                    return pos+spanLength;
                }
                pos+=spanLength;
                rest-=spanLength;
                continue;  // spanLength>0: Match strings from after a span.
            } else {
                // Try to match only one code point from after a string match if some
                // string matched beyond it, so that we try all possible positions
                // and don't overshoot.
                spanLength=spanOneUTF8(spanSet, s+pos, rest);
                if(spanLength>0) {
                    if(spanLength==rest) {
                        return length;  // Reached the end of the string.
                    }
                    // Match strings after this code point.
                    // There cannot be any increments below it because UnicodeSet strings
                    // contain multiple code points.
                    pos+=spanLength;
                    rest-=spanLength;
                    offsets.shift(spanLength);
                    spanLength=0;
                    continue;  // Match strings from after a single code point.
                }
                // Match strings from after the next string match.
            }
        }
        int32_t minOffset=offsets.popMinimum();
        pos+=minOffset;
        rest-=minOffset;
        spanLength=0;  // Match strings from after a string match.
    }
}

int32_t UnicodeSetStringSpan::spanBackUTF8(const uint8_t *s, int32_t length, USetSpanCondition spanCondition) const {
    if(spanCondition==USET_SPAN_NOT_CONTAINED) {
        return spanNotBackUTF8(s, length);
    }
    int32_t pos=spanSet.spanBackUTF8((const char *)s, length, USET_SPAN_CONTAINED);
    if(pos==0) {
        return 0;
    }
    int32_t spanLength=length-pos;

    // Consider strings; they may overlap with the span.
    OffsetList offsets;
    if(spanCondition==USET_SPAN_CONTAINED) {
        // Use offset list to try all possibilities.
        offsets.setMaxLength(maxLength8);
    }
    int32_t i, stringsLength=strings.size();
    uint8_t *spanBackUTF8Lengths=spanLengths;
    if(all) {
        spanBackUTF8Lengths+=3*stringsLength;
    }
    for(;;) {
        const uint8_t *s8=utf8;
        int32_t length8;
        if(spanCondition==USET_SPAN_CONTAINED) {
            for(i=0; i<stringsLength; ++i) {
                length8=utf8Lengths[i];
                if(length8==0) {
                    continue;  // String not representable in UTF-8.
                }
                int32_t overlap=spanBackUTF8Lengths[i];
                if(overlap==ALL_CP_CONTAINED) {
                    s8+=length8;
                    continue;  // Irrelevant string.
                }

                // Try to match this string at pos-(length8-overlap)..pos-length8.
                if(overlap>=LONG_SPAN) {
                    overlap=length8;
                    // While contained: No point matching fully inside the code point span.
                    int32_t len1=0;
                    U8_FWD_1(s8, len1, overlap);
                    overlap-=len1;  // Length of the string minus the first code point.
                }
                if(overlap>spanLength) {
                    overlap=spanLength;
                }
                int32_t dec=length8-overlap;  // Keep dec+overlap==length8.
                for(;;) {
                    if(dec>pos) {
                        break;
                    }
                    // Try to match if the decrement is not listed already.
                    // Match at code point boundaries. (The UTF-8 strings were converted
                    // from UTF-16 and are guaranteed to be well-formed.)
                    if( !U8_IS_TRAIL(s[pos-dec]) &&
                        !offsets.containsOffset(dec) &&
                        matches8(s+pos-dec, s8, length8)
                    ) {
                        if(dec==pos) {
                            return 0;  // Reached the start of the string.
                        }
                        offsets.addOffset(dec);
                    }
                    if(overlap==0) {
                        break;
                    }
                    --overlap;
                    ++dec;
                }
                s8+=length8;
            }
        } else /* USET_SPAN_SIMPLE */ {
            int32_t maxDec=0, maxOverlap=0;
            for(i=0; i<stringsLength; ++i) {
                length8=utf8Lengths[i];
                if(length8==0) {
                    continue;  // String not representable in UTF-8.
                }
                int32_t overlap=spanBackUTF8Lengths[i];
                // For longest match, we do need to try to match even an all-contained string
                // to find the match from the latest end.

                // Try to match this string at pos-(length8-overlap)..pos-length8.
                if(overlap>=LONG_SPAN) {
                    overlap=length8;
                    // Longest match: Need to match fully inside the code point span
                    // to find the match from the latest end.
                }
                if(overlap>spanLength) {
                    overlap=spanLength;
                }
                int32_t dec=length8-overlap;  // Keep dec+overlap==length8.
                for(;;) {
                    if(dec>pos || overlap<maxOverlap) {
                        break;
                    }
                    // Try to match if the string is longer or ends later.
                    // Match at code point boundaries. (The UTF-8 strings were converted
                    // from UTF-16 and are guaranteed to be well-formed.)
                    if( !U8_IS_TRAIL(s[pos-dec]) &&
                        (overlap>maxOverlap || /* redundant overlap==maxOverlap && */ dec>maxDec) &&
                        matches8(s+pos-dec, s8, length8)
                    ) {
                        maxDec=dec;  // Longest match from latest end.
                        maxOverlap=overlap;
                        break;
                    }
                    --overlap;
                    ++dec;
                }
                s8+=length8;
            }

            if(maxDec!=0 || maxOverlap!=0) {
                // Longest-match algorithm, and there was a string match.
                // Simply continue before it.
                pos-=maxDec;
                if(pos==0) {
                    return 0;  // Reached the start of the string.
                }
                spanLength=0;  // Match strings from before a string match.
                continue;
            }
        }
        // Finished trying to match all strings at pos.

        if(spanLength!=0 || pos==length) {
            // The position is before an unlimited code point span (spanLength!=0),
            // not before a string match.
            // The only position where spanLength==0 before a span is pos==length.
            // Otherwise, an unlimited code point span is only tried again when no
            // strings match, and if such a non-initial span fails we stop.
            if(offsets.isEmpty()) {
                return pos;  // No strings matched before a span.
            }
            // Match strings from before the next string match.
        } else {
            // The position is before a string match (or a single code point).
            if(offsets.isEmpty()) {
                // No more strings matched before a previous string match.
                // Try another code point span from before the last string match.
                int32_t oldPos=pos;
                pos=spanSet.spanBackUTF8((const char *)s, oldPos, USET_SPAN_CONTAINED);
                spanLength=oldPos-pos;
                if( pos==0 ||           // Reached the start of the string, or
                    spanLength==0       // neither strings nor span progressed.
                ) {
                    return pos;
                }
                continue;  // spanLength>0: Match strings from before a span.
            } else {
                // Try to match only one code point from before a string match if some
                // string matched beyond it, so that we try all possible positions
                // and don't overshoot.
                spanLength=spanOneBackUTF8(spanSet, s, pos);
                if(spanLength>0) {
                    if(spanLength==pos) {
                        return 0;  // Reached the start of the string.
                    }
                    // Match strings before this code point.
                    // There cannot be any decrements below it because UnicodeSet strings
                    // contain multiple code points.
                    pos-=spanLength;
                    offsets.shift(spanLength);
                    spanLength=0;
                    continue;  // Match strings from before a single code point.
                }
                // Match strings from before the next string match.
            }
        }
        pos-=offsets.popMinimum();
        spanLength=0;  // Match strings from before a string match.
    }
}

/*
 * Algorithm for spanNot()==span(USET_SPAN_NOT_CONTAINED)
 *
 * Theoretical algorithm:
 * - Iterate through the string, and at each code point boundary:
 *   + If the code point there is in the set, then return with the current position.
 *   + If a set string matches at the current position, then return with the current position.
 *
 * Optimized implementation:
 *
 * (Same assumption as for span() above.)
 *
 * Create and cache a spanNotSet which contains all of the single code points
 * of the original set but none of its strings.
 * For each set string add its initial code point to the spanNotSet.
 * (Also add its final code point for spanNotBack().)
 *
 * - Loop:
 *   + Do spanLength=spanNotSet.span(USET_SPAN_NOT_CONTAINED).
 *   + If the current code point is in the original set, then
 *     return the current position.
 *   + If any set string matches at the current position, then
 *     return the current position.
 *   + If there is no match at the current position, neither for the code point there
 *     nor for any set string, then skip this code point and continue the loop.
 *     This happens for set-string-initial code points that were added to spanNotSet
 *     when there is not actually a match for such a set string.
 */

int32_t UnicodeSetStringSpan::spanNot(const UChar *s, int32_t length) const {
    int32_t pos=0, rest=length;
    int32_t i, stringsLength=strings.size();
    do {
        // Span until we find a code point from the set,
        // or a code point that starts or ends some string.
        i=pSpanNotSet->span(s+pos, rest, USET_SPAN_NOT_CONTAINED);
        if(i==rest) {
            return length;  // Reached the end of the string.
        }
        pos+=i;
        rest-=i;

        // Check whether the current code point is in the original set,
        // without the string starts and ends.
        int32_t cpLength=spanOne(spanSet, s+pos, rest);
        if(cpLength>0) {
            return pos;  // There is a set element at pos.
        }

        // Try to match the strings at pos.
        for(i=0; i<stringsLength; ++i) {
            if(spanLengths[i]==ALL_CP_CONTAINED) {
                continue;  // Irrelevant string.
            }
            const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
            const UChar *s16=string.getBuffer();
            int32_t length16=string.length();
            if(length16<=rest && matches16CPB(s, pos, length, s16, length16)) {
                return pos;  // There is a set element at pos.
            }
        }

        // The span(while not contained) ended on a string start/end which is
        // not in the original set. Skip this code point and continue.
        // cpLength<0
        pos-=cpLength;
        rest+=cpLength;
    } while(rest!=0);
    return length;  // Reached the end of the string.
}

int32_t UnicodeSetStringSpan::spanNotBack(const UChar *s, int32_t length) const {
    int32_t pos=length;
    int32_t i, stringsLength=strings.size();
    do {
        // Span until we find a code point from the set,
        // or a code point that starts or ends some string.
        pos=pSpanNotSet->spanBack(s, pos, USET_SPAN_NOT_CONTAINED);
        if(pos==0) {
            return 0;  // Reached the start of the string.
        }

        // Check whether the current code point is in the original set,
        // without the string starts and ends.
        int32_t cpLength=spanOneBack(spanSet, s, pos);
        if(cpLength>0) {
            return pos;  // There is a set element at pos.
        }

        // Try to match the strings at pos.
        for(i=0; i<stringsLength; ++i) {
            // Use spanLengths rather than a spanBackLengths pointer because
            // it is easier and we only need to know whether the string is irrelevant
            // which is the same in either array.
            if(spanLengths[i]==ALL_CP_CONTAINED) {
                continue;  // Irrelevant string.
            }
            const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
            const UChar *s16=string.getBuffer();
            int32_t length16=string.length();
            if(length16<=pos && matches16CPB(s, pos-length16, length, s16, length16)) {
                return pos;  // There is a set element at pos.
            }
        }

        // The span(while not contained) ended on a string start/end which is
        // not in the original set. Skip this code point and continue.
        // cpLength<0
        pos+=cpLength;
    } while(pos!=0);
    return 0;  // Reached the start of the string.
}

int32_t UnicodeSetStringSpan::spanNotUTF8(const uint8_t *s, int32_t length) const {
    int32_t pos=0, rest=length;
    int32_t i, stringsLength=strings.size();
    uint8_t *spanUTF8Lengths=spanLengths;
    if(all) {
        spanUTF8Lengths+=2*stringsLength;
    }
    do {
        // Span until we find a code point from the set,
        // or a code point that starts or ends some string.
        i=pSpanNotSet->spanUTF8((const char *)s+pos, rest, USET_SPAN_NOT_CONTAINED);
        if(i==rest) {
            return length;  // Reached the end of the string.
        }
        pos+=i;
        rest-=i;

        // Check whether the current code point is in the original set,
        // without the string starts and ends.
        int32_t cpLength=spanOneUTF8(spanSet, s+pos, rest);
        if(cpLength>0) {
            return pos;  // There is a set element at pos.
        }

        // Try to match the strings at pos.
        const uint8_t *s8=utf8;
        int32_t length8;
        for(i=0; i<stringsLength; ++i) {
            length8=utf8Lengths[i];
            // ALL_CP_CONTAINED: Irrelevant string.
            if(length8!=0 && spanUTF8Lengths[i]!=ALL_CP_CONTAINED && length8<=rest && matches8(s+pos, s8, length8)) {
                return pos;  // There is a set element at pos.
            }
            s8+=length8;
        }

        // The span(while not contained) ended on a string start/end which is
        // not in the original set. Skip this code point and continue.
        // cpLength<0
        pos-=cpLength;
        rest+=cpLength;
    } while(rest!=0);
    return length;  // Reached the end of the string.
}

int32_t UnicodeSetStringSpan::spanNotBackUTF8(const uint8_t *s, int32_t length) const {
    int32_t pos=length;
    int32_t i, stringsLength=strings.size();
    uint8_t *spanBackUTF8Lengths=spanLengths;
    if(all) {
        spanBackUTF8Lengths+=3*stringsLength;
    }
    do {
        // Span until we find a code point from the set,
        // or a code point that starts or ends some string.
        pos=pSpanNotSet->spanBackUTF8((const char *)s, pos, USET_SPAN_NOT_CONTAINED);
        if(pos==0) {
            return 0;  // Reached the start of the string.
        }

        // Check whether the current code point is in the original set,
        // without the string starts and ends.
        int32_t cpLength=spanOneBackUTF8(spanSet, s, pos);
        if(cpLength>0) {
            return pos;  // There is a set element at pos.
        }

        // Try to match the strings at pos.
        const uint8_t *s8=utf8;
        int32_t length8;
        for(i=0; i<stringsLength; ++i) {
            length8=utf8Lengths[i];
            // ALL_CP_CONTAINED: Irrelevant string.
            if(length8!=0 && spanBackUTF8Lengths[i]!=ALL_CP_CONTAINED && length8<=pos && matches8(s+pos-length8, s8, length8)) {
                return pos;  // There is a set element at pos.
            }
            s8+=length8;
        }

        // The span(while not contained) ended on a string start/end which is
        // not in the original set. Skip this code point and continue.
        // cpLength<0
        pos+=cpLength;
    } while(pos!=0);
    return 0;  // Reached the start of the string.
}

U_NAMESPACE_END