aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/icu/common/umutablecptrie.cpp
blob: cdbe27080b491cb652fafefa596199ce278ffa96 (plain) (blame)
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
// © 2017 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html

// umutablecptrie.cpp (inspired by utrie2_builder.cpp)
// created: 2017dec29 Markus W. Scherer

// #define UCPTRIE_DEBUG
#ifdef UCPTRIE_DEBUG
#   include <stdio.h>
#endif

#include "unicode/utypes.h"
#include "unicode/ucptrie.h"
#include "unicode/umutablecptrie.h"
#include "unicode/uobject.h"
#include "unicode/utf16.h"
#include "cmemory.h"
#include "uassert.h"
#include "ucptrie_impl.h"

// ICU-20235 In case Microsoft math.h has defined this, undefine it.
#ifdef OVERFLOW
#undef OVERFLOW
#endif

U_NAMESPACE_BEGIN

namespace {

constexpr int32_t MAX_UNICODE = 0x10ffff;

constexpr int32_t UNICODE_LIMIT = 0x110000;
constexpr int32_t BMP_LIMIT = 0x10000;
constexpr int32_t ASCII_LIMIT = 0x80;

constexpr int32_t I_LIMIT = UNICODE_LIMIT >> UCPTRIE_SHIFT_3;
constexpr int32_t BMP_I_LIMIT = BMP_LIMIT >> UCPTRIE_SHIFT_3;
constexpr int32_t ASCII_I_LIMIT = ASCII_LIMIT >> UCPTRIE_SHIFT_3;

constexpr int32_t SMALL_DATA_BLOCKS_PER_BMP_BLOCK = (1 << (UCPTRIE_FAST_SHIFT - UCPTRIE_SHIFT_3));

// Flag values for data blocks.
constexpr uint8_t ALL_SAME = 0;
constexpr uint8_t MIXED = 1;
constexpr uint8_t SAME_AS = 2;

/** Start with allocation of 16k data entries. */
constexpr int32_t INITIAL_DATA_LENGTH = ((int32_t)1 << 14);

/** Grow about 8x each time. */
constexpr int32_t MEDIUM_DATA_LENGTH = ((int32_t)1 << 17);

/**
 * Maximum length of the build-time data array.
 * One entry per 0x110000 code points.
 */
constexpr int32_t MAX_DATA_LENGTH = UNICODE_LIMIT;

// Flag values for index-3 blocks while compacting/building.
constexpr uint8_t I3_NULL = 0;
constexpr uint8_t I3_BMP = 1;
constexpr uint8_t I3_16 = 2;
constexpr uint8_t I3_18 = 3;

constexpr int32_t INDEX_3_18BIT_BLOCK_LENGTH = UCPTRIE_INDEX_3_BLOCK_LENGTH + UCPTRIE_INDEX_3_BLOCK_LENGTH / 8;

class AllSameBlocks;
class MixedBlocks;

class MutableCodePointTrie : public UMemory {
public:
    MutableCodePointTrie(uint32_t initialValue, uint32_t errorValue, UErrorCode &errorCode);
    MutableCodePointTrie(const MutableCodePointTrie &other, UErrorCode &errorCode);
    MutableCodePointTrie(const MutableCodePointTrie &other) = delete;
    ~MutableCodePointTrie();

    MutableCodePointTrie &operator=(const MutableCodePointTrie &other) = delete;

    static MutableCodePointTrie *fromUCPMap(const UCPMap *map, UErrorCode &errorCode);
    static MutableCodePointTrie *fromUCPTrie(const UCPTrie *trie, UErrorCode &errorCode);

    uint32_t get(UChar32 c) const;
    int32_t getRange(UChar32 start, UCPMapValueFilter *filter, const void *context,
                     uint32_t *pValue) const;

    void set(UChar32 c, uint32_t value, UErrorCode &errorCode);
    void setRange(UChar32 start, UChar32 end, uint32_t value, UErrorCode &errorCode);

    UCPTrie *build(UCPTrieType type, UCPTrieValueWidth valueWidth, UErrorCode &errorCode);

private:
    void clear();

    bool ensureHighStart(UChar32 c);
    int32_t allocDataBlock(int32_t blockLength);
    int32_t getDataBlock(int32_t i);

    void maskValues(uint32_t mask);
    UChar32 findHighStart() const;
    int32_t compactWholeDataBlocks(int32_t fastILimit, AllSameBlocks &allSameBlocks);
    int32_t compactData(
            int32_t fastILimit, uint32_t *newData, int32_t newDataCapacity,
            int32_t dataNullIndex, MixedBlocks &mixedBlocks, UErrorCode &errorCode);
    int32_t compactIndex(int32_t fastILimit, MixedBlocks &mixedBlocks, UErrorCode &errorCode);
    int32_t compactTrie(int32_t fastILimit, UErrorCode &errorCode);

    uint32_t *index = nullptr;
    int32_t indexCapacity = 0;
    int32_t index3NullOffset = -1;
    uint32_t *data = nullptr;
    int32_t dataCapacity = 0;
    int32_t dataLength = 0;
    int32_t dataNullOffset = -1;

    uint32_t origInitialValue;
    uint32_t initialValue;
    uint32_t errorValue;
    UChar32 highStart;
    uint32_t highValue;
#ifdef UCPTRIE_DEBUG
public:
    const char *name;
#endif
private:
    /** Temporary array while building the final data. */
    uint16_t *index16 = nullptr;
    uint8_t flags[UNICODE_LIMIT >> UCPTRIE_SHIFT_3];
};

MutableCodePointTrie::MutableCodePointTrie(uint32_t iniValue, uint32_t errValue, UErrorCode &errorCode) :
        origInitialValue(iniValue), initialValue(iniValue), errorValue(errValue),
        highStart(0), highValue(initialValue)
#ifdef UCPTRIE_DEBUG
        , name("open")
#endif
        {
    if (U_FAILURE(errorCode)) { return; }
    index = (uint32_t *)uprv_malloc(BMP_I_LIMIT * 4);
    data = (uint32_t *)uprv_malloc(INITIAL_DATA_LENGTH * 4);
    if (index == nullptr || data == nullptr) {
        errorCode = U_MEMORY_ALLOCATION_ERROR;
        return;
    }
    indexCapacity = BMP_I_LIMIT;
    dataCapacity = INITIAL_DATA_LENGTH;
}

MutableCodePointTrie::MutableCodePointTrie(const MutableCodePointTrie &other, UErrorCode &errorCode) :
        index3NullOffset(other.index3NullOffset),
        dataNullOffset(other.dataNullOffset),
        origInitialValue(other.origInitialValue), initialValue(other.initialValue),
        errorValue(other.errorValue),
        highStart(other.highStart), highValue(other.highValue)
#ifdef UCPTRIE_DEBUG
        , name("mutable clone")
#endif
        {
    if (U_FAILURE(errorCode)) { return; }
    int32_t iCapacity = highStart <= BMP_LIMIT ? BMP_I_LIMIT : I_LIMIT;
    index = (uint32_t *)uprv_malloc(iCapacity * 4);
    data = (uint32_t *)uprv_malloc(other.dataCapacity * 4);
    if (index == nullptr || data == nullptr) {
        errorCode = U_MEMORY_ALLOCATION_ERROR;
        return;
    }
    indexCapacity = iCapacity;
    dataCapacity = other.dataCapacity;

    int32_t iLimit = highStart >> UCPTRIE_SHIFT_3;
    uprv_memcpy(flags, other.flags, iLimit);
    uprv_memcpy(index, other.index, iLimit * 4);
    uprv_memcpy(data, other.data, (size_t)other.dataLength * 4);
    dataLength = other.dataLength;
    U_ASSERT(other.index16 == nullptr);
}

MutableCodePointTrie::~MutableCodePointTrie() {
    uprv_free(index);
    uprv_free(data);
    uprv_free(index16);
}

MutableCodePointTrie *MutableCodePointTrie::fromUCPMap(const UCPMap *map, UErrorCode &errorCode) {
    // Use the highValue as the initialValue to reduce the highStart.
    uint32_t errorValue = ucpmap_get(map, -1);
    uint32_t initialValue = ucpmap_get(map, 0x10ffff);
    LocalPointer<MutableCodePointTrie> mutableTrie(
        new MutableCodePointTrie(initialValue, errorValue, errorCode),
        errorCode);
    if (U_FAILURE(errorCode)) {
        return nullptr;
    }
    UChar32 start = 0, end;
    uint32_t value;
    while ((end = ucpmap_getRange(map, start, UCPMAP_RANGE_NORMAL, 0,
                                  nullptr, nullptr, &value)) >= 0) {
        if (value != initialValue) {
            if (start == end) {
                mutableTrie->set(start, value, errorCode);
            } else {
                mutableTrie->setRange(start, end, value, errorCode);
            }
        }
        start = end + 1;
    }
    if (U_SUCCESS(errorCode)) {
        return mutableTrie.orphan();
    } else {
        return nullptr;
    }
}

MutableCodePointTrie *MutableCodePointTrie::fromUCPTrie(const UCPTrie *trie, UErrorCode &errorCode) {
    // Use the highValue as the initialValue to reduce the highStart.
    uint32_t errorValue;
    uint32_t initialValue;
    switch (trie->valueWidth) {
    case UCPTRIE_VALUE_BITS_16:
        errorValue = trie->data.ptr16[trie->dataLength - UCPTRIE_ERROR_VALUE_NEG_DATA_OFFSET];
        initialValue = trie->data.ptr16[trie->dataLength - UCPTRIE_HIGH_VALUE_NEG_DATA_OFFSET];
        break;
    case UCPTRIE_VALUE_BITS_32:
        errorValue = trie->data.ptr32[trie->dataLength - UCPTRIE_ERROR_VALUE_NEG_DATA_OFFSET];
        initialValue = trie->data.ptr32[trie->dataLength - UCPTRIE_HIGH_VALUE_NEG_DATA_OFFSET];
        break;
    case UCPTRIE_VALUE_BITS_8:
        errorValue = trie->data.ptr8[trie->dataLength - UCPTRIE_ERROR_VALUE_NEG_DATA_OFFSET];
        initialValue = trie->data.ptr8[trie->dataLength - UCPTRIE_HIGH_VALUE_NEG_DATA_OFFSET];
        break;
    default:
        // Unreachable if the trie is properly initialized.
        errorCode = U_ILLEGAL_ARGUMENT_ERROR;
        return nullptr;
    }
    LocalPointer<MutableCodePointTrie> mutableTrie(
        new MutableCodePointTrie(initialValue, errorValue, errorCode),
        errorCode);
    if (U_FAILURE(errorCode)) {
        return nullptr;
    }
    UChar32 start = 0, end;
    uint32_t value;
    while ((end = ucptrie_getRange(trie, start, UCPMAP_RANGE_NORMAL, 0,
                                   nullptr, nullptr, &value)) >= 0) {
        if (value != initialValue) {
            if (start == end) {
                mutableTrie->set(start, value, errorCode);
            } else {
                mutableTrie->setRange(start, end, value, errorCode);
            }
        }
        start = end + 1;
    }
    if (U_SUCCESS(errorCode)) {
        return mutableTrie.orphan();
    } else {
        return nullptr;
    }
}

void MutableCodePointTrie::clear() {
    index3NullOffset = dataNullOffset = -1;
    dataLength = 0;
    highValue = initialValue = origInitialValue;
    highStart = 0;
    uprv_free(index16);
    index16 = nullptr;
}

uint32_t MutableCodePointTrie::get(UChar32 c) const {
    if ((uint32_t)c > MAX_UNICODE) {
        return errorValue;
    }
    if (c >= highStart) {
        return highValue;
    }
    int32_t i = c >> UCPTRIE_SHIFT_3;
    if (flags[i] == ALL_SAME) {
        return index[i];
    } else {
        return data[index[i] + (c & UCPTRIE_SMALL_DATA_MASK)];
    }
}

inline uint32_t maybeFilterValue(uint32_t value, uint32_t initialValue, uint32_t nullValue,
                                 UCPMapValueFilter *filter, const void *context) {
    if (value == initialValue) {
        value = nullValue;
    } else if (filter != nullptr) {
        value = filter(context, value);
    }
    return value;
}

UChar32 MutableCodePointTrie::getRange(
        UChar32 start, UCPMapValueFilter *filter, const void *context,
        uint32_t *pValue) const {
    if ((uint32_t)start > MAX_UNICODE) {
        return U_SENTINEL;
    }
    if (start >= highStart) {
        if (pValue != nullptr) {
            uint32_t value = highValue;
            if (filter != nullptr) { value = filter(context, value); }
            *pValue = value;
        }
        return MAX_UNICODE;
    }
    uint32_t nullValue = initialValue;
    if (filter != nullptr) { nullValue = filter(context, nullValue); }
    UChar32 c = start;
    uint32_t trieValue, value;
    bool haveValue = false;
    int32_t i = c >> UCPTRIE_SHIFT_3;
    do {
        if (flags[i] == ALL_SAME) {
            uint32_t trieValue2 = index[i];
            if (haveValue) {
                if (trieValue2 != trieValue) {
                    if (filter == nullptr ||
                            maybeFilterValue(trieValue2, initialValue, nullValue,
                                             filter, context) != value) {
                        return c - 1;
                    }
                    trieValue = trieValue2;  // may or may not help
                }
            } else {
                trieValue = trieValue2;
                value = maybeFilterValue(trieValue2, initialValue, nullValue, filter, context);
                if (pValue != nullptr) { *pValue = value; }
                haveValue = true;
            }
            c = (c + UCPTRIE_SMALL_DATA_BLOCK_LENGTH) & ~UCPTRIE_SMALL_DATA_MASK;
        } else /* MIXED */ {
            int32_t di = index[i] + (c & UCPTRIE_SMALL_DATA_MASK);
            uint32_t trieValue2 = data[di];
            if (haveValue) {
                if (trieValue2 != trieValue) {
                    if (filter == nullptr ||
                            maybeFilterValue(trieValue2, initialValue, nullValue,
                                             filter, context) != value) {
                        return c - 1;
                    }
                    trieValue = trieValue2;  // may or may not help
                }
            } else {
                trieValue = trieValue2;
                value = maybeFilterValue(trieValue2, initialValue, nullValue, filter, context);
                if (pValue != nullptr) { *pValue = value; }
                haveValue = true;
            }
            while ((++c & UCPTRIE_SMALL_DATA_MASK) != 0) {
                trieValue2 = data[++di];
                if (trieValue2 != trieValue) {
                    if (filter == nullptr ||
                            maybeFilterValue(trieValue2, initialValue, nullValue,
                                             filter, context) != value) {
                        return c - 1;
                    }
                }
                trieValue = trieValue2;  // may or may not help
            }
        }
        ++i;
    } while (c < highStart);
    U_ASSERT(haveValue);
    if (maybeFilterValue(highValue, initialValue, nullValue,
                         filter, context) != value) {
        return c - 1;
    } else {
        return MAX_UNICODE;
    }
}

void
writeBlock(uint32_t *block, uint32_t value) {
    uint32_t *limit = block + UCPTRIE_SMALL_DATA_BLOCK_LENGTH;
    while (block < limit) {
        *block++ = value;
    }
}

bool MutableCodePointTrie::ensureHighStart(UChar32 c) {
    if (c >= highStart) {
        // Round up to a UCPTRIE_CP_PER_INDEX_2_ENTRY boundary to simplify compaction.
        c = (c + UCPTRIE_CP_PER_INDEX_2_ENTRY) & ~(UCPTRIE_CP_PER_INDEX_2_ENTRY - 1);
        int32_t i = highStart >> UCPTRIE_SHIFT_3;
        int32_t iLimit = c >> UCPTRIE_SHIFT_3;
        if (iLimit > indexCapacity) {
            uint32_t *newIndex = (uint32_t *)uprv_malloc(I_LIMIT * 4);
            if (newIndex == nullptr) { return false; }
            uprv_memcpy(newIndex, index, i * 4);
            uprv_free(index);
            index = newIndex;
            indexCapacity = I_LIMIT;
        }
        do {
            flags[i] = ALL_SAME;
            index[i] = initialValue;
        } while(++i < iLimit);
        highStart = c;
    }
    return true;
}

int32_t MutableCodePointTrie::allocDataBlock(int32_t blockLength) {
    int32_t newBlock = dataLength;
    int32_t newTop = newBlock + blockLength;
    if (newTop > dataCapacity) {
        int32_t capacity;
        if (dataCapacity < MEDIUM_DATA_LENGTH) {
            capacity = MEDIUM_DATA_LENGTH;
        } else if (dataCapacity < MAX_DATA_LENGTH) {
            capacity = MAX_DATA_LENGTH;
        } else {
            // Should never occur.
            // Either MAX_DATA_LENGTH is incorrect,
            // or the code writes more values than should be possible.
            return -1;
        }
        uint32_t *newData = (uint32_t *)uprv_malloc(capacity * 4);
        if (newData == nullptr) {
            return -1;
        }
        uprv_memcpy(newData, data, (size_t)dataLength * 4);
        uprv_free(data);
        data = newData;
        dataCapacity = capacity;
    }
    dataLength = newTop;
    return newBlock;
}

/**
 * No error checking for illegal arguments.
 *
 * @return -1 if no new data block available (out of memory in data array)
 * @internal
 */
int32_t MutableCodePointTrie::getDataBlock(int32_t i) {
    if (flags[i] == MIXED) {
        return index[i];
    }
    if (i < BMP_I_LIMIT) {
        int32_t newBlock = allocDataBlock(UCPTRIE_FAST_DATA_BLOCK_LENGTH);
        if (newBlock < 0) { return newBlock; }
        int32_t iStart = i & ~(SMALL_DATA_BLOCKS_PER_BMP_BLOCK -1);
        int32_t iLimit = iStart + SMALL_DATA_BLOCKS_PER_BMP_BLOCK;
        do {
            U_ASSERT(flags[iStart] == ALL_SAME);
            writeBlock(data + newBlock, index[iStart]);
            flags[iStart] = MIXED;
            index[iStart++] = newBlock;
            newBlock += UCPTRIE_SMALL_DATA_BLOCK_LENGTH;
        } while (iStart < iLimit);
        return index[i];
    } else {
        int32_t newBlock = allocDataBlock(UCPTRIE_SMALL_DATA_BLOCK_LENGTH);
        if (newBlock < 0) { return newBlock; }
        writeBlock(data + newBlock, index[i]);
        flags[i] = MIXED;
        index[i] = newBlock;
        return newBlock;
    }
}

void MutableCodePointTrie::set(UChar32 c, uint32_t value, UErrorCode &errorCode) {
    if (U_FAILURE(errorCode)) {
        return;
    }
    if ((uint32_t)c > MAX_UNICODE) {
        errorCode = U_ILLEGAL_ARGUMENT_ERROR;
        return;
    }

    int32_t block;
    if (!ensureHighStart(c) || (block = getDataBlock(c >> UCPTRIE_SHIFT_3)) < 0) {
        errorCode = U_MEMORY_ALLOCATION_ERROR;
        return;
    }

    data[block + (c & UCPTRIE_SMALL_DATA_MASK)] = value;
}

void
fillBlock(uint32_t *block, UChar32 start, UChar32 limit, uint32_t value) {
    uint32_t *pLimit = block + limit;
    block += start;
    while (block < pLimit) {
        *block++ = value;
    }
}

void MutableCodePointTrie::setRange(UChar32 start, UChar32 end, uint32_t value, UErrorCode &errorCode) {
    if (U_FAILURE(errorCode)) {
        return;
    }
    if ((uint32_t)start > MAX_UNICODE || (uint32_t)end > MAX_UNICODE || start > end) {
        errorCode = U_ILLEGAL_ARGUMENT_ERROR;
        return;
    }
    if (!ensureHighStart(end)) {
        errorCode = U_MEMORY_ALLOCATION_ERROR;
        return;
    }

    UChar32 limit = end + 1;
    if (start & UCPTRIE_SMALL_DATA_MASK) {
        // Set partial block at [start..following block boundary[.
        int32_t block = getDataBlock(start >> UCPTRIE_SHIFT_3);
        if (block < 0) {
            errorCode = U_MEMORY_ALLOCATION_ERROR;
            return;
        }

        UChar32 nextStart = (start + UCPTRIE_SMALL_DATA_MASK) & ~UCPTRIE_SMALL_DATA_MASK;
        if (nextStart <= limit) {
            fillBlock(data + block, start & UCPTRIE_SMALL_DATA_MASK, UCPTRIE_SMALL_DATA_BLOCK_LENGTH,
                      value);
            start = nextStart;
        } else {
            fillBlock(data + block, start & UCPTRIE_SMALL_DATA_MASK, limit & UCPTRIE_SMALL_DATA_MASK,
                      value);
            return;
        }
    }

    // Number of positions in the last, partial block.
    int32_t rest = limit & UCPTRIE_SMALL_DATA_MASK;

    // Round down limit to a block boundary.
    limit &= ~UCPTRIE_SMALL_DATA_MASK;

    // Iterate over all-value blocks.
    while (start < limit) {
        int32_t i = start >> UCPTRIE_SHIFT_3;
        if (flags[i] == ALL_SAME) {
            index[i] = value;
        } else /* MIXED */ {
            fillBlock(data + index[i], 0, UCPTRIE_SMALL_DATA_BLOCK_LENGTH, value);
        }
        start += UCPTRIE_SMALL_DATA_BLOCK_LENGTH;
    }

    if (rest > 0) {
        // Set partial block at [last block boundary..limit[.
        int32_t block = getDataBlock(start >> UCPTRIE_SHIFT_3);
        if (block < 0) {
            errorCode = U_MEMORY_ALLOCATION_ERROR;
            return;
        }

        fillBlock(data + block, 0, rest, value);
    }
}

/* compaction --------------------------------------------------------------- */

void MutableCodePointTrie::maskValues(uint32_t mask) {
    initialValue &= mask;
    errorValue &= mask;
    highValue &= mask;
    int32_t iLimit = highStart >> UCPTRIE_SHIFT_3;
    for (int32_t i = 0; i < iLimit; ++i) {
        if (flags[i] == ALL_SAME) {
            index[i] &= mask;
        }
    }
    for (int32_t i = 0; i < dataLength; ++i) {
        data[i] &= mask;
    }
}

template<typename UIntA, typename UIntB>
bool equalBlocks(const UIntA *s, const UIntB *t, int32_t length) {
    while (length > 0 && *s == *t) {
        ++s;
        ++t;
        --length;
    }
    return length == 0;
}

bool allValuesSameAs(const uint32_t *p, int32_t length, uint32_t value) {
    const uint32_t *pLimit = p + length;
    while (p < pLimit && *p == value) { ++p; }
    return p == pLimit;
}

/** Search for an identical block. */
int32_t findSameBlock(const uint16_t *p, int32_t pStart, int32_t length,
                      const uint16_t *q, int32_t qStart, int32_t blockLength) {
    // Ensure that we do not even partially get past length.
    length -= blockLength;

    q += qStart;
    while (pStart <= length) {
        if (equalBlocks(p + pStart, q, blockLength)) {
            return pStart;
        }
        ++pStart;
    }
    return -1;
}

int32_t findAllSameBlock(const uint32_t *p, int32_t start, int32_t limit,
                         uint32_t value, int32_t blockLength) {
    // Ensure that we do not even partially get past limit.
    limit -= blockLength;

    for (int32_t block = start; block <= limit; ++block) {
        if (p[block] == value) {
            for (int32_t i = 1;; ++i) {
                if (i == blockLength) {
                    return block;
                }
                if (p[block + i] != value) {
                    block += i;
                    break;
                }
            }
        }
    }
    return -1;
}

/**
 * Look for maximum overlap of the beginning of the other block
 * with the previous, adjacent block.
 */
template<typename UIntA, typename UIntB>
int32_t getOverlap(const UIntA *p, int32_t length,
                   const UIntB *q, int32_t qStart, int32_t blockLength) {
    int32_t overlap = blockLength - 1;
    U_ASSERT(overlap <= length);
    q += qStart;
    while (overlap > 0 && !equalBlocks(p + (length - overlap), q, overlap)) {
        --overlap;
    }
    return overlap;
}

int32_t getAllSameOverlap(const uint32_t *p, int32_t length, uint32_t value,
                          int32_t blockLength) {
    int32_t min = length - (blockLength - 1);
    int32_t i = length;
    while (min < i && p[i - 1] == value) { --i; }
    return length - i;
}

bool isStartOfSomeFastBlock(uint32_t dataOffset, const uint32_t index[], int32_t fastILimit) {
    for (int32_t i = 0; i < fastILimit; i += SMALL_DATA_BLOCKS_PER_BMP_BLOCK) {
        if (index[i] == dataOffset) {
            return true;
        }
    }
    return false;
}

/**
 * Finds the start of the last range in the trie by enumerating backward.
 * Indexes for code points higher than this will be omitted.
 */
UChar32 MutableCodePointTrie::findHighStart() const {
    int32_t i = highStart >> UCPTRIE_SHIFT_3;
    while (i > 0) {
        bool match;
        if (flags[--i] == ALL_SAME) {
            match = index[i] == highValue;
        } else /* MIXED */ {
            const uint32_t *p = data + index[i];
            for (int32_t j = 0;; ++j) {
                if (j == UCPTRIE_SMALL_DATA_BLOCK_LENGTH) {
                    match = true;
                    break;
                }
                if (p[j] != highValue) {
                    match = false;
                    break;
                }
            }
        }
        if (!match) {
            return (i + 1) << UCPTRIE_SHIFT_3;
        }
    }
    return 0;
}

class AllSameBlocks {
public:
    static constexpr int32_t NEW_UNIQUE = -1;
    static constexpr int32_t OVERFLOW = -2;

    AllSameBlocks() : length(0), mostRecent(-1) {}

    int32_t findOrAdd(int32_t index, int32_t count, uint32_t value) {
        if (mostRecent >= 0 && values[mostRecent] == value) {
            refCounts[mostRecent] += count;
            return indexes[mostRecent];
        }
        for (int32_t i = 0; i < length; ++i) {
            if (values[i] == value) {
                mostRecent = i;
                refCounts[i] += count;
                return indexes[i];
            }
        }
        if (length == CAPACITY) {
            return OVERFLOW;
        }
        mostRecent = length;
        indexes[length] = index;
        values[length] = value;
        refCounts[length++] = count;
        return NEW_UNIQUE;
    }

    /** Replaces the block which has the lowest reference count. */
    void add(int32_t index, int32_t count, uint32_t value) {
        U_ASSERT(length == CAPACITY);
        int32_t least = -1;
        int32_t leastCount = I_LIMIT;
        for (int32_t i = 0; i < length; ++i) {
            U_ASSERT(values[i] != value);
            if (refCounts[i] < leastCount) {
                least = i;
                leastCount = refCounts[i];
            }
        }
        U_ASSERT(least >= 0);
        mostRecent = least;
        indexes[least] = index;
        values[least] = value;
        refCounts[least] = count;
    }

    int32_t findMostUsed() const {
        if (length == 0) { return -1; }
        int32_t max = -1;
        int32_t maxCount = 0;
        for (int32_t i = 0; i < length; ++i) {
            if (refCounts[i] > maxCount) {
                max = i;
                maxCount = refCounts[i];
            }
        }
        return indexes[max];
    }

private:
    static constexpr int32_t CAPACITY = 32;

    int32_t length;
    int32_t mostRecent;

    int32_t indexes[CAPACITY];
    uint32_t values[CAPACITY];
    int32_t refCounts[CAPACITY];
};

// Custom hash table for mixed-value blocks to be found anywhere in the
// compacted data or index so far.
class MixedBlocks {
public:
    MixedBlocks() {}
    ~MixedBlocks() {
        uprv_free(table);
    }

    bool init(int32_t maxLength, int32_t newBlockLength) {
        // We store actual data indexes + 1 to reserve 0 for empty entries.
        int32_t maxDataIndex = maxLength - newBlockLength + 1;
        int32_t newLength;
        if (maxDataIndex <= 0xfff) {  // 4k
            newLength = 6007;
            shift = 12;
            mask = 0xfff;
        } else if (maxDataIndex <= 0x7fff) {  // 32k
            newLength = 50021;
            shift = 15;
            mask = 0x7fff;
        } else if (maxDataIndex <= 0x1ffff) {  // 128k
            newLength = 200003;
            shift = 17;
            mask = 0x1ffff;
        } else {
            // maxDataIndex up to around MAX_DATA_LENGTH, ca. 1.1M
            newLength = 1500007;
            shift = 21;
            mask = 0x1fffff;
        }
        if (newLength > capacity) {
            uprv_free(table);
            table = (uint32_t *)uprv_malloc(newLength * 4);
            if (table == nullptr) {
                return false;
            }
            capacity = newLength;
        }
        length = newLength;
        uprv_memset(table, 0, length * 4);

        blockLength = newBlockLength;
        return true;
    }

    template<typename UInt>
    void extend(const UInt *data, int32_t minStart, int32_t prevDataLength, int32_t newDataLength) {
        int32_t start = prevDataLength - blockLength;
        if (start >= minStart) {
            ++start;  // Skip the last block that we added last time.
        } else {
            start = minStart;  // Begin with the first full block.
        }
        for (int32_t end = newDataLength - blockLength; start <= end; ++start) {
            uint32_t hashCode = makeHashCode(data, start);
            addEntry(data, start, hashCode, start);
        }
    }

    template<typename UIntA, typename UIntB>
    int32_t findBlock(const UIntA *data, const UIntB *blockData, int32_t blockStart) const {
        uint32_t hashCode = makeHashCode(blockData, blockStart);
        int32_t entryIndex = findEntry(data, blockData, blockStart, hashCode);
        if (entryIndex >= 0) {
            return (table[entryIndex] & mask) - 1;
        } else {
            return -1;
        }
    }

    int32_t findAllSameBlock(const uint32_t *data, uint32_t blockValue) const {
        uint32_t hashCode = makeHashCode(blockValue);
        int32_t entryIndex = findEntry(data, blockValue, hashCode);
        if (entryIndex >= 0) {
            return (table[entryIndex] & mask) - 1;
        } else {
            return -1;
        }
    }

private:
    template<typename UInt>
    uint32_t makeHashCode(const UInt *blockData, int32_t blockStart) const {
        int32_t blockLimit = blockStart + blockLength;
        uint32_t hashCode = blockData[blockStart++];
        do {
            hashCode = 37 * hashCode + blockData[blockStart++];
        } while (blockStart < blockLimit);
        return hashCode;
    }

    uint32_t makeHashCode(uint32_t blockValue) const {
        uint32_t hashCode = blockValue;
        for (int32_t i = 1; i < blockLength; ++i) {
            hashCode = 37 * hashCode + blockValue;
        }
        return hashCode;
    }

    template<typename UInt>
    void addEntry(const UInt *data, int32_t blockStart, uint32_t hashCode, int32_t dataIndex) {
        U_ASSERT(0 <= dataIndex && dataIndex < (int32_t)mask);
        int32_t entryIndex = findEntry(data, data, blockStart, hashCode);
        if (entryIndex < 0) {
            table[~entryIndex] = (hashCode << shift) | (dataIndex + 1);
        }
    }

    template<typename UIntA, typename UIntB>
    int32_t findEntry(const UIntA *data, const UIntB *blockData, int32_t blockStart,
                      uint32_t hashCode) const {
        uint32_t shiftedHashCode = hashCode << shift;
        int32_t initialEntryIndex = (hashCode % (length - 1)) + 1;  // 1..length-1
        for (int32_t entryIndex = initialEntryIndex;;) {
            uint32_t entry = table[entryIndex];
            if (entry == 0) {
                return ~entryIndex;
            }
            if ((entry & ~mask) == shiftedHashCode) {
                int32_t dataIndex = (entry & mask) - 1;
                if (equalBlocks(data + dataIndex, blockData + blockStart, blockLength)) {
                    return entryIndex;
                }
            }
            entryIndex = nextIndex(initialEntryIndex, entryIndex);
        }
    }

    int32_t findEntry(const uint32_t *data, uint32_t blockValue, uint32_t hashCode) const {
        uint32_t shiftedHashCode = hashCode << shift;
        int32_t initialEntryIndex = (hashCode % (length - 1)) + 1;  // 1..length-1
        for (int32_t entryIndex = initialEntryIndex;;) {
            uint32_t entry = table[entryIndex];
            if (entry == 0) {
                return ~entryIndex;
            }
            if ((entry & ~mask) == shiftedHashCode) {
                int32_t dataIndex = (entry & mask) - 1;
                if (allValuesSameAs(data + dataIndex, blockLength, blockValue)) {
                    return entryIndex;
                }
            }
            entryIndex = nextIndex(initialEntryIndex, entryIndex);
        }
    }

    inline int32_t nextIndex(int32_t initialEntryIndex, int32_t entryIndex) const {
        // U_ASSERT(0 < initialEntryIndex && initialEntryIndex < length);
        return (entryIndex + initialEntryIndex) % length;
    }

    // Hash table.
    // The length is a prime number, larger than the maximum data length.
    // The "shift" lower bits store a data index + 1.
    // The remaining upper bits store a partial hashCode of the block data values.
    uint32_t *table = nullptr;
    int32_t capacity = 0;
    int32_t length = 0;
    int32_t shift = 0;
    uint32_t mask = 0;

    int32_t blockLength = 0;
};

int32_t MutableCodePointTrie::compactWholeDataBlocks(int32_t fastILimit, AllSameBlocks &allSameBlocks) {
#ifdef UCPTRIE_DEBUG
    bool overflow = false;
#endif

    // ASCII data will be stored as a linear table, even if the following code
    // does not yet count it that way.
    int32_t newDataCapacity = ASCII_LIMIT;
    // Add room for a small data null block in case it would match the start of
    // a fast data block where dataNullOffset must not be set in that case.
    newDataCapacity += UCPTRIE_SMALL_DATA_BLOCK_LENGTH;
    // Add room for special values (errorValue, highValue) and padding.
    newDataCapacity += 4;
    int32_t iLimit = highStart >> UCPTRIE_SHIFT_3;
    int32_t blockLength = UCPTRIE_FAST_DATA_BLOCK_LENGTH;
    int32_t inc = SMALL_DATA_BLOCKS_PER_BMP_BLOCK;
    for (int32_t i = 0; i < iLimit; i += inc) {
        if (i == fastILimit) {
            blockLength = UCPTRIE_SMALL_DATA_BLOCK_LENGTH;
            inc = 1;
        }
        uint32_t value = index[i];
        if (flags[i] == MIXED) {
            // Really mixed?
            const uint32_t *p = data + value;
            value = *p;
            if (allValuesSameAs(p + 1, blockLength - 1, value)) {
                flags[i] = ALL_SAME;
                index[i] = value;
                // Fall through to ALL_SAME handling.
            } else {
                newDataCapacity += blockLength;
                continue;
            }
        } else {
            U_ASSERT(flags[i] == ALL_SAME);
            if (inc > 1) {
                // Do all of the fast-range data block's ALL_SAME parts have the same value?
                bool allSame = true;
                int32_t next_i = i + inc;
                for (int32_t j = i + 1; j < next_i; ++j) {
                    U_ASSERT(flags[j] == ALL_SAME);
                    if (index[j] != value) {
                        allSame = false;
                        break;
                    }
                }
                if (!allSame) {
                    // Turn it into a MIXED block.
                    if (getDataBlock(i) < 0) {
                        return -1;
                    }
                    newDataCapacity += blockLength;
                    continue;
                }
            }
        }
        // Is there another ALL_SAME block with the same value?
        int32_t other = allSameBlocks.findOrAdd(i, inc, value);
        if (other == AllSameBlocks::OVERFLOW) {
            // The fixed-size array overflowed. Slow check for a duplicate block.
#ifdef UCPTRIE_DEBUG
            if (!overflow) {
                puts("UCPTrie AllSameBlocks overflow");
                overflow = true;
            }
#endif
            int32_t jInc = SMALL_DATA_BLOCKS_PER_BMP_BLOCK;
            for (int32_t j = 0;; j += jInc) {
                if (j == i) {
                    allSameBlocks.add(i, inc, value);
                    break;
                }
                if (j == fastILimit) {
                    jInc = 1;
                }
                if (flags[j] == ALL_SAME && index[j] == value) {
                    allSameBlocks.add(j, jInc + inc, value);
                    other = j;
                    break;
                    // We could keep counting blocks with the same value
                    // before we add the first one, which may improve compaction in rare cases,
                    // but it would make it slower.
                }
            }
        }
        if (other >= 0) {
            flags[i] = SAME_AS;
            index[i] = other;
        } else {
            // New unique same-value block.
            newDataCapacity += blockLength;
        }
    }
    return newDataCapacity;
}

#ifdef UCPTRIE_DEBUG
#   define DEBUG_DO(expr) expr
#else
#   define DEBUG_DO(expr)
#endif

#ifdef UCPTRIE_DEBUG
// Braille symbols: U+28xx = UTF-8 E2 A0 80..E2 A3 BF
int32_t appendValue(char s[], int32_t length, uint32_t value) {
    value ^= value >> 16;
    value ^= value >> 8;
    s[length] = 0xE2;
    s[length + 1] = (char)(0xA0 + ((value >> 6) & 3));
    s[length + 2] = (char)(0x80 + (value & 0x3F));
    return length + 3;
}

void printBlock(const uint32_t *block, int32_t blockLength, uint32_t value,
                UChar32 start, int32_t overlap, uint32_t initialValue) {
    char s[UCPTRIE_FAST_DATA_BLOCK_LENGTH * 3 + 3];
    int32_t length = 0;
    int32_t i;
    for (i = 0; i < overlap; ++i) {
        length = appendValue(s, length, 0);  // Braille blank
    }
    s[length++] = '|';
    for (; i < blockLength; ++i) {
        if (block != nullptr) {
            value = block[i];
        }
        if (value == initialValue) {
            value = 0x40;  // Braille lower left dot
        }
        length = appendValue(s, length, value);
    }
    s[length] = 0;
    start += overlap;
    if (start <= 0xffff) {
        printf("    %04lX  %s|\n", (long)start, s);
    } else if (start <= 0xfffff) {
        printf("   %5lX  %s|\n", (long)start, s);
    } else {
        printf("  %6lX  %s|\n", (long)start, s);
    }
}
#endif

/**
 * Compacts a build-time trie.
 *
 * The compaction
 * - removes blocks that are identical with earlier ones
 * - overlaps each new non-duplicate block as much as possible with the previously-written one
 * - works with fast-range data blocks whose length is a multiple of that of
 *   higher-code-point data blocks
 *
 * It does not try to find an optimal order of writing, deduplicating, and overlapping blocks.
 */
int32_t MutableCodePointTrie::compactData(
        int32_t fastILimit, uint32_t *newData, int32_t newDataCapacity,
        int32_t dataNullIndex, MixedBlocks &mixedBlocks, UErrorCode &errorCode) {
#ifdef UCPTRIE_DEBUG
    int32_t countSame=0, sumOverlaps=0;
    bool printData = dataLength == 29088 /* line.brk */ ||
        // dataLength == 30048 /* CanonIterData */ ||
        dataLength == 50400 /* zh.txt~stroke */;
#endif

    // The linear ASCII data has been copied into newData already.
    int32_t newDataLength = 0;
    for (int32_t i = 0; newDataLength < ASCII_LIMIT;
            newDataLength += UCPTRIE_FAST_DATA_BLOCK_LENGTH, i += SMALL_DATA_BLOCKS_PER_BMP_BLOCK) {
        index[i] = newDataLength;
#ifdef UCPTRIE_DEBUG
        if (printData) {
            printBlock(newData + newDataLength, UCPTRIE_FAST_DATA_BLOCK_LENGTH, 0, newDataLength, 0, initialValue);
        }
#endif
    }

    int32_t blockLength = UCPTRIE_FAST_DATA_BLOCK_LENGTH;
    if (!mixedBlocks.init(newDataCapacity, blockLength)) {
        errorCode = U_MEMORY_ALLOCATION_ERROR;
        return 0;
    }
    mixedBlocks.extend(newData, 0, 0, newDataLength);

    int32_t iLimit = highStart >> UCPTRIE_SHIFT_3;
    int32_t inc = SMALL_DATA_BLOCKS_PER_BMP_BLOCK;
    int32_t fastLength = 0;
    for (int32_t i = ASCII_I_LIMIT; i < iLimit; i += inc) {
        if (i == fastILimit) {
            blockLength = UCPTRIE_SMALL_DATA_BLOCK_LENGTH;
            inc = 1;
            fastLength = newDataLength;
            if (!mixedBlocks.init(newDataCapacity, blockLength)) {
                errorCode = U_MEMORY_ALLOCATION_ERROR;
                return 0;
            }
            mixedBlocks.extend(newData, 0, 0, newDataLength);
        }
        if (flags[i] == ALL_SAME) {
            uint32_t value = index[i];
            // Find an earlier part of the data array of length blockLength
            // that is filled with this value.
            int32_t n = mixedBlocks.findAllSameBlock(newData, value);
            // If we find a match, and the current block is the data null block,
            // and it is not a fast block but matches the start of a fast block,
            // then we need to continue looking.
            // This is because this small block is shorter than the fast block,
            // and not all of the rest of the fast block is filled with this value.
            // Otherwise trie.getRange() would detect that the fast block starts at
            // dataNullOffset and assume incorrectly that it is filled with the null value.
            while (n >= 0 && i == dataNullIndex && i >= fastILimit && n < fastLength &&
                    isStartOfSomeFastBlock(n, index, fastILimit)) {
                n = findAllSameBlock(newData, n + 1, newDataLength, value, blockLength);
            }
            if (n >= 0) {
                DEBUG_DO(++countSame);
                index[i] = n;
            } else {
                n = getAllSameOverlap(newData, newDataLength, value, blockLength);
                DEBUG_DO(sumOverlaps += n);
#ifdef UCPTRIE_DEBUG
                if (printData) {
                    printBlock(nullptr, blockLength, value, i << UCPTRIE_SHIFT_3, n, initialValue);
                }
#endif
                index[i] = newDataLength - n;
                int32_t prevDataLength = newDataLength;
                while (n < blockLength) {
                    newData[newDataLength++] = value;
                    ++n;
                }
                mixedBlocks.extend(newData, 0, prevDataLength, newDataLength);
            }
        } else if (flags[i] == MIXED) {
            const uint32_t *block = data + index[i];
            int32_t n = mixedBlocks.findBlock(newData, block, 0);
            if (n >= 0) {
                DEBUG_DO(++countSame);
                index[i] = n;
            } else {
                n = getOverlap(newData, newDataLength, block, 0, blockLength);
                DEBUG_DO(sumOverlaps += n);
#ifdef UCPTRIE_DEBUG
                if (printData) {
                    printBlock(block, blockLength, 0, i << UCPTRIE_SHIFT_3, n, initialValue);
                }
#endif
                index[i] = newDataLength - n;
                int32_t prevDataLength = newDataLength;
                while (n < blockLength) {
                    newData[newDataLength++] = block[n++];
                }
                mixedBlocks.extend(newData, 0, prevDataLength, newDataLength);
            }
        } else /* SAME_AS */ {
            uint32_t j = index[i];
            index[i] = index[j];
        }
    }

#ifdef UCPTRIE_DEBUG
    /* we saved some space */
    printf("compacting UCPTrie: count of 32-bit data words %lu->%lu  countSame=%ld  sumOverlaps=%ld\n",
            (long)dataLength, (long)newDataLength, (long)countSame, (long)sumOverlaps);
#endif
    return newDataLength;
}

int32_t MutableCodePointTrie::compactIndex(int32_t fastILimit, MixedBlocks &mixedBlocks,
                                           UErrorCode &errorCode) {
    int32_t fastIndexLength = fastILimit >> (UCPTRIE_FAST_SHIFT - UCPTRIE_SHIFT_3);
    if ((highStart >> UCPTRIE_FAST_SHIFT) <= fastIndexLength) {
        // Only the linear fast index, no multi-stage index tables.
        index3NullOffset = UCPTRIE_NO_INDEX3_NULL_OFFSET;
        return fastIndexLength;
    }

    // Condense the fast index table.
    // Also, does it contain an index-3 block with all dataNullOffset?
    uint16_t fastIndex[UCPTRIE_BMP_INDEX_LENGTH];  // fastIndexLength
    int32_t i3FirstNull = -1;
    for (int32_t i = 0, j = 0; i < fastILimit; ++j) {
        uint32_t i3 = index[i];
        fastIndex[j] = (uint16_t)i3;
        if (i3 == (uint32_t)dataNullOffset) {
            if (i3FirstNull < 0) {
                i3FirstNull = j;
            } else if (index3NullOffset < 0 &&
                    (j - i3FirstNull + 1) == UCPTRIE_INDEX_3_BLOCK_LENGTH) {
                index3NullOffset = i3FirstNull;
            }
        } else {
            i3FirstNull = -1;
        }
        // Set the index entries that compactData() skipped.
        // Needed when the multi-stage index covers the fast index range as well.
        int32_t iNext = i + SMALL_DATA_BLOCKS_PER_BMP_BLOCK;
        while (++i < iNext) {
            i3 += UCPTRIE_SMALL_DATA_BLOCK_LENGTH;
            index[i] = i3;
        }
    }

    if (!mixedBlocks.init(fastIndexLength, UCPTRIE_INDEX_3_BLOCK_LENGTH)) {
        errorCode = U_MEMORY_ALLOCATION_ERROR;
        return 0;
    }
    mixedBlocks.extend(fastIndex, 0, 0, fastIndexLength);

    // Examine index-3 blocks. For each determine one of:
    // - same as the index-3 null block
    // - same as a fast-index block
    // - 16-bit indexes
    // - 18-bit indexes
    // We store this in the first flags entry for the index-3 block.
    //
    // Also determine an upper limit for the index-3 table length.
    int32_t index3Capacity = 0;
    i3FirstNull = index3NullOffset;
    bool hasLongI3Blocks = false;
    // If the fast index covers the whole BMP, then
    // the multi-stage index is only for supplementary code points.
    // Otherwise, the multi-stage index covers all of Unicode.
    int32_t iStart = fastILimit < BMP_I_LIMIT ? 0 : BMP_I_LIMIT;
    int32_t iLimit = highStart >> UCPTRIE_SHIFT_3;
    for (int32_t i = iStart; i < iLimit;) {
        int32_t j = i;
        int32_t jLimit = i + UCPTRIE_INDEX_3_BLOCK_LENGTH;
        uint32_t oredI3 = 0;
        bool isNull = true;
        do {
            uint32_t i3 = index[j];
            oredI3 |= i3;
            if (i3 != (uint32_t)dataNullOffset) {
                isNull = false;
            }
        } while (++j < jLimit);
        if (isNull) {
            flags[i] = I3_NULL;
            if (i3FirstNull < 0) {
                if (oredI3 <= 0xffff) {
                    index3Capacity += UCPTRIE_INDEX_3_BLOCK_LENGTH;
                } else {
                    index3Capacity += INDEX_3_18BIT_BLOCK_LENGTH;
                    hasLongI3Blocks = true;
                }
                i3FirstNull = 0;
            }
        } else {
            if (oredI3 <= 0xffff) {
                int32_t n = mixedBlocks.findBlock(fastIndex, index, i);
                if (n >= 0) {
                    flags[i] = I3_BMP;
                    index[i] = n;
                } else {
                    flags[i] = I3_16;
                    index3Capacity += UCPTRIE_INDEX_3_BLOCK_LENGTH;
                }
            } else {
                flags[i] = I3_18;
                index3Capacity += INDEX_3_18BIT_BLOCK_LENGTH;
                hasLongI3Blocks = true;
            }
        }
        i = j;
    }

    int32_t index2Capacity = (iLimit - iStart) >> UCPTRIE_SHIFT_2_3;

    // Length of the index-1 table, rounded up.
    int32_t index1Length = (index2Capacity + UCPTRIE_INDEX_2_MASK) >> UCPTRIE_SHIFT_1_2;

    // Index table: Fast index, index-1, index-3, index-2.
    // +1 for possible index table padding.
    int32_t index16Capacity = fastIndexLength + index1Length + index3Capacity + index2Capacity + 1;
    index16 = (uint16_t *)uprv_malloc(index16Capacity * 2);
    if (index16 == nullptr) {
        errorCode = U_MEMORY_ALLOCATION_ERROR;
        return 0;
    }
    uprv_memcpy(index16, fastIndex, fastIndexLength * 2);

    if (!mixedBlocks.init(index16Capacity, UCPTRIE_INDEX_3_BLOCK_LENGTH)) {
        errorCode = U_MEMORY_ALLOCATION_ERROR;
        return 0;
    }
    MixedBlocks longI3Blocks;
    if (hasLongI3Blocks) {
        if (!longI3Blocks.init(index16Capacity, INDEX_3_18BIT_BLOCK_LENGTH)) {
            errorCode = U_MEMORY_ALLOCATION_ERROR;
            return 0;
        }
    }

    // Compact the index-3 table and write an uncompacted version of the index-2 table.
    uint16_t index2[UNICODE_LIMIT >> UCPTRIE_SHIFT_2];  // index2Capacity
    int32_t i2Length = 0;
    i3FirstNull = index3NullOffset;
    int32_t index3Start = fastIndexLength + index1Length;
    int32_t indexLength = index3Start;
    for (int32_t i = iStart; i < iLimit; i += UCPTRIE_INDEX_3_BLOCK_LENGTH) {
        int32_t i3;
        uint8_t f = flags[i];
        if (f == I3_NULL && i3FirstNull < 0) {
            // First index-3 null block. Write & overlap it like a normal block, then remember it.
            f = dataNullOffset <= 0xffff ? I3_16 : I3_18;
            i3FirstNull = 0;
        }
        if (f == I3_NULL) {
            i3 = index3NullOffset;
        } else if (f == I3_BMP) {
            i3 = index[i];
        } else if (f == I3_16) {
            int32_t n = mixedBlocks.findBlock(index16, index, i);
            if (n >= 0) {
                i3 = n;
            } else {
                if (indexLength == index3Start) {
                    // No overlap at the boundary between the index-1 and index-3 tables.
                    n = 0;
                } else {
                    n = getOverlap(index16, indexLength,
                                   index, i, UCPTRIE_INDEX_3_BLOCK_LENGTH);
                }
                i3 = indexLength - n;
                int32_t prevIndexLength = indexLength;
                while (n < UCPTRIE_INDEX_3_BLOCK_LENGTH) {
                    index16[indexLength++] = index[i + n++];
                }
                mixedBlocks.extend(index16, index3Start, prevIndexLength, indexLength);
                if (hasLongI3Blocks) {
                    longI3Blocks.extend(index16, index3Start, prevIndexLength, indexLength);
                }
            }
        } else {
            U_ASSERT(f == I3_18);
            U_ASSERT(hasLongI3Blocks);
            // Encode an index-3 block that contains one or more data indexes exceeding 16 bits.
            int32_t j = i;
            int32_t jLimit = i + UCPTRIE_INDEX_3_BLOCK_LENGTH;
            int32_t k = indexLength;
            do {
                ++k;
                uint32_t v = index[j++];
                uint32_t upperBits = (v & 0x30000) >> 2;
                index16[k++] = v;
                v = index[j++];
                upperBits |= (v & 0x30000) >> 4;
                index16[k++] = v;
                v = index[j++];
                upperBits |= (v & 0x30000) >> 6;
                index16[k++] = v;
                v = index[j++];
                upperBits |= (v & 0x30000) >> 8;
                index16[k++] = v;
                v = index[j++];
                upperBits |= (v & 0x30000) >> 10;
                index16[k++] = v;
                v = index[j++];
                upperBits |= (v & 0x30000) >> 12;
                index16[k++] = v;
                v = index[j++];
                upperBits |= (v & 0x30000) >> 14;
                index16[k++] = v;
                v = index[j++];
                upperBits |= (v & 0x30000) >> 16;
                index16[k++] = v;
                index16[k - 9] = upperBits;
            } while (j < jLimit);
            int32_t n = longI3Blocks.findBlock(index16, index16, indexLength);
            if (n >= 0) {
                i3 = n | 0x8000;
            } else {
                if (indexLength == index3Start) {
                    // No overlap at the boundary between the index-1 and index-3 tables.
                    n = 0;
                } else {
                    n = getOverlap(index16, indexLength,
                                   index16, indexLength, INDEX_3_18BIT_BLOCK_LENGTH);
                }
                i3 = (indexLength - n) | 0x8000;
                int32_t prevIndexLength = indexLength;
                if (n > 0) {
                    int32_t start = indexLength;
                    while (n < INDEX_3_18BIT_BLOCK_LENGTH) {
                        index16[indexLength++] = index16[start + n++];
                    }
                } else {
                    indexLength += INDEX_3_18BIT_BLOCK_LENGTH;
                }
                mixedBlocks.extend(index16, index3Start, prevIndexLength, indexLength);
                if (hasLongI3Blocks) {
                    longI3Blocks.extend(index16, index3Start, prevIndexLength, indexLength);
                }
            }
        }
        if (index3NullOffset < 0 && i3FirstNull >= 0) {
            index3NullOffset = i3;
        }
        // Set the index-2 table entry.
        index2[i2Length++] = i3;
    }
    U_ASSERT(i2Length == index2Capacity);
    U_ASSERT(indexLength <= index3Start + index3Capacity);

    if (index3NullOffset < 0) {
        index3NullOffset = UCPTRIE_NO_INDEX3_NULL_OFFSET;
    }
    if (indexLength >= (UCPTRIE_NO_INDEX3_NULL_OFFSET + UCPTRIE_INDEX_3_BLOCK_LENGTH)) {
        // The index-3 offsets exceed 15 bits, or
        // the last one cannot be distinguished from the no-null-block value.
        errorCode = U_INDEX_OUTOFBOUNDS_ERROR;
        return 0;
    }

    // Compact the index-2 table and write the index-1 table.
    static_assert(UCPTRIE_INDEX_2_BLOCK_LENGTH == UCPTRIE_INDEX_3_BLOCK_LENGTH,
                  "must re-init mixedBlocks");
    int32_t blockLength = UCPTRIE_INDEX_2_BLOCK_LENGTH;
    int32_t i1 = fastIndexLength;
    for (int32_t i = 0; i < i2Length; i += blockLength) {
        int32_t n;
        if ((i2Length - i) >= blockLength) {
            // normal block
            U_ASSERT(blockLength == UCPTRIE_INDEX_2_BLOCK_LENGTH);
            n = mixedBlocks.findBlock(index16, index2, i);
        } else {
            // highStart is inside the last index-2 block. Shorten it.
            blockLength = i2Length - i;
            n = findSameBlock(index16, index3Start, indexLength,
                              index2, i, blockLength);
        }
        int32_t i2;
        if (n >= 0) {
            i2 = n;
        } else {
            if (indexLength == index3Start) {
                // No overlap at the boundary between the index-1 and index-3/2 tables.
                n = 0;
            } else {
                n = getOverlap(index16, indexLength, index2, i, blockLength);
            }
            i2 = indexLength - n;
            int32_t prevIndexLength = indexLength;
            while (n < blockLength) {
                index16[indexLength++] = index2[i + n++];
            }
            mixedBlocks.extend(index16, index3Start, prevIndexLength, indexLength);
        }
        // Set the index-1 table entry.
        index16[i1++] = i2;
    }
    U_ASSERT(i1 == index3Start);
    U_ASSERT(indexLength <= index16Capacity);

#ifdef UCPTRIE_DEBUG
    /* we saved some space */
    printf("compacting UCPTrie: count of 16-bit index words %lu->%lu\n",
            (long)iLimit, (long)indexLength);
#endif

    return indexLength;
}

int32_t MutableCodePointTrie::compactTrie(int32_t fastILimit, UErrorCode &errorCode) {
    // Find the real highStart and round it up.
    U_ASSERT((highStart & (UCPTRIE_CP_PER_INDEX_2_ENTRY - 1)) == 0);
    highValue = get(MAX_UNICODE);
    int32_t realHighStart = findHighStart();
    realHighStart = (realHighStart + (UCPTRIE_CP_PER_INDEX_2_ENTRY - 1)) &
        ~(UCPTRIE_CP_PER_INDEX_2_ENTRY - 1);
    if (realHighStart == UNICODE_LIMIT) {
        highValue = initialValue;
    }

#ifdef UCPTRIE_DEBUG
    printf("UCPTrie: highStart U+%06lx  highValue 0x%lx  initialValue 0x%lx\n",
            (long)realHighStart, (long)highValue, (long)initialValue);
#endif

    // We always store indexes and data values for the fast range.
    // Pin highStart to the top of that range while building.
    UChar32 fastLimit = fastILimit << UCPTRIE_SHIFT_3;
    if (realHighStart < fastLimit) {
        for (int32_t i = (realHighStart >> UCPTRIE_SHIFT_3); i < fastILimit; ++i) {
            flags[i] = ALL_SAME;
            index[i] = highValue;
        }
        highStart = fastLimit;
    } else {
        highStart = realHighStart;
    }

    uint32_t asciiData[ASCII_LIMIT];
    for (int32_t i = 0; i < ASCII_LIMIT; ++i) {
        asciiData[i] = get(i);
    }

    // First we look for which data blocks have the same value repeated over the whole block,
    // deduplicate such blocks, find a good null data block (for faster enumeration),
    // and get an upper bound for the necessary data array length.
    AllSameBlocks allSameBlocks;
    int32_t newDataCapacity = compactWholeDataBlocks(fastILimit, allSameBlocks);
    if (newDataCapacity < 0) {
        errorCode = U_MEMORY_ALLOCATION_ERROR;
        return 0;
    }
    uint32_t *newData = (uint32_t *)uprv_malloc(newDataCapacity * 4);
    if (newData == nullptr) {
        errorCode = U_MEMORY_ALLOCATION_ERROR;
        return 0;
    }
    uprv_memcpy(newData, asciiData, sizeof(asciiData));

    int32_t dataNullIndex = allSameBlocks.findMostUsed();

    MixedBlocks mixedBlocks;
    int32_t newDataLength = compactData(fastILimit, newData, newDataCapacity,
                                        dataNullIndex, mixedBlocks, errorCode);
    if (U_FAILURE(errorCode)) { return 0; }
    U_ASSERT(newDataLength <= newDataCapacity);
    uprv_free(data);
    data = newData;
    dataCapacity = newDataCapacity;
    dataLength = newDataLength;
    if (dataLength > (0x3ffff + UCPTRIE_SMALL_DATA_BLOCK_LENGTH)) {
        // The offset of the last data block is too high to be stored in the index table.
        errorCode = U_INDEX_OUTOFBOUNDS_ERROR;
        return 0;
    }

    if (dataNullIndex >= 0) {
        dataNullOffset = index[dataNullIndex];
#ifdef UCPTRIE_DEBUG
        if (data[dataNullOffset] != initialValue) {
            printf("UCPTrie initialValue %lx -> more common nullValue %lx\n",
                   (long)initialValue, (long)data[dataNullOffset]);
        }
#endif
        initialValue = data[dataNullOffset];
    } else {
        dataNullOffset = UCPTRIE_NO_DATA_NULL_OFFSET;
    }

    int32_t indexLength = compactIndex(fastILimit, mixedBlocks, errorCode);
    highStart = realHighStart;
    return indexLength;
}

UCPTrie *MutableCodePointTrie::build(UCPTrieType type, UCPTrieValueWidth valueWidth, UErrorCode &errorCode) {
    if (U_FAILURE(errorCode)) {
        return nullptr;
    }
    if (type < UCPTRIE_TYPE_FAST || UCPTRIE_TYPE_SMALL < type ||
            valueWidth < UCPTRIE_VALUE_BITS_16 || UCPTRIE_VALUE_BITS_8 < valueWidth) {
        errorCode = U_ILLEGAL_ARGUMENT_ERROR;
        return nullptr;
    }

    // The mutable trie always stores 32-bit values.
    // When we build a UCPTrie for a smaller value width, we first mask off unused bits
    // before compacting the data.
    switch (valueWidth) {
    case UCPTRIE_VALUE_BITS_32:
        break;
    case UCPTRIE_VALUE_BITS_16:
        maskValues(0xffff);
        break;
    case UCPTRIE_VALUE_BITS_8:
        maskValues(0xff);
        break;
    default:
        break;
    }

    UChar32 fastLimit = type == UCPTRIE_TYPE_FAST ? BMP_LIMIT : UCPTRIE_SMALL_LIMIT;
    int32_t indexLength = compactTrie(fastLimit >> UCPTRIE_SHIFT_3, errorCode);
    if (U_FAILURE(errorCode)) {
        clear();
        return nullptr;
    }

    // Ensure data table alignment: The index length must be even for uint32_t data.
    if (valueWidth == UCPTRIE_VALUE_BITS_32 && (indexLength & 1) != 0) {
        index16[indexLength++] = 0xffee;  // arbitrary value
    }

    // Make the total trie structure length a multiple of 4 bytes by padding the data table,
    // and store special values as the last two data values.
    int32_t length = indexLength * 2;
    if (valueWidth == UCPTRIE_VALUE_BITS_16) {
        if (((indexLength ^ dataLength) & 1) != 0) {
            // padding
            data[dataLength++] = errorValue;
        }
        if (data[dataLength - 1] != errorValue || data[dataLength - 2] != highValue) {
            data[dataLength++] = highValue;
            data[dataLength++] = errorValue;
        }
        length += dataLength * 2;
    } else if (valueWidth == UCPTRIE_VALUE_BITS_32) {
        // 32-bit data words never need padding to a multiple of 4 bytes.
        if (data[dataLength - 1] != errorValue || data[dataLength - 2] != highValue) {
            if (data[dataLength - 1] != highValue) {
                data[dataLength++] = highValue;
            }
            data[dataLength++] = errorValue;
        }
        length += dataLength * 4;
    } else {
        int32_t and3 = (length + dataLength) & 3;
        if (and3 == 0 && data[dataLength - 1] == errorValue && data[dataLength - 2] == highValue) {
            // all set
        } else if(and3 == 3 && data[dataLength - 1] == highValue) {
            data[dataLength++] = errorValue;
        } else {
            while (and3 != 2) {
                data[dataLength++] = highValue;
                and3 = (and3 + 1) & 3;
            }
            data[dataLength++] = highValue;
            data[dataLength++] = errorValue;
        }
        length += dataLength;
    }

    // Calculate the total length of the UCPTrie as a single memory block.
    length += sizeof(UCPTrie);
    U_ASSERT((length & 3) == 0);

    uint8_t *bytes = (uint8_t *)uprv_malloc(length);
    if (bytes == nullptr) {
        errorCode = U_MEMORY_ALLOCATION_ERROR;
        clear();
        return nullptr;
    }
    UCPTrie *trie = reinterpret_cast<UCPTrie *>(bytes);
    uprv_memset(trie, 0, sizeof(UCPTrie));
    trie->indexLength = indexLength;
    trie->dataLength = dataLength;

    trie->highStart = highStart;
    // Round up shifted12HighStart to a multiple of 0x1000 for easy testing from UTF-8 lead bytes.
    // Runtime code needs to then test for the real highStart as well.
    trie->shifted12HighStart = (highStart + 0xfff) >> 12;
    trie->type = type;
    trie->valueWidth = valueWidth;

    trie->index3NullOffset = index3NullOffset;
    trie->dataNullOffset = dataNullOffset;
    trie->nullValue = initialValue;

    bytes += sizeof(UCPTrie);

    // Fill the index and data arrays.
    uint16_t *dest16 = (uint16_t *)bytes;
    trie->index = dest16;

    if (highStart <= fastLimit) {
        // Condense only the fast index from the mutable-trie index.
        for (int32_t i = 0, j = 0; j < indexLength; i += SMALL_DATA_BLOCKS_PER_BMP_BLOCK, ++j) {
            *dest16++ = (uint16_t)index[i];  // dest16[j]
        }
    } else {
        uprv_memcpy(dest16, index16, indexLength * 2);
        dest16 += indexLength;
    }
    bytes += indexLength * 2;

    // Write the data array.
    const uint32_t *p = data;
    switch (valueWidth) {
    case UCPTRIE_VALUE_BITS_16:
        // Write 16-bit data values.
        trie->data.ptr16 = dest16;
        for (int32_t i = dataLength; i > 0; --i) {
            *dest16++ = (uint16_t)*p++;
        }
        break;
    case UCPTRIE_VALUE_BITS_32:
        // Write 32-bit data values.
        trie->data.ptr32 = (uint32_t *)bytes;
        uprv_memcpy(bytes, p, (size_t)dataLength * 4);
        break;
    case UCPTRIE_VALUE_BITS_8:
        // Write 8-bit data values.
        trie->data.ptr8 = bytes;
        for (int32_t i = dataLength; i > 0; --i) {
            *bytes++ = (uint8_t)*p++;
        }
        break;
    default:
        // Will not occur, valueWidth checked at the beginning.
        break;
    }

#ifdef UCPTRIE_DEBUG
    trie->name = name;

    ucptrie_printLengths(trie, "");
#endif

    clear();
    return trie;
}

}  // namespace

U_NAMESPACE_END

U_NAMESPACE_USE

U_CAPI UMutableCPTrie * U_EXPORT2
umutablecptrie_open(uint32_t initialValue, uint32_t errorValue, UErrorCode *pErrorCode) {
    if (U_FAILURE(*pErrorCode)) {
        return nullptr;
    }
    LocalPointer<MutableCodePointTrie> trie(
        new MutableCodePointTrie(initialValue, errorValue, *pErrorCode), *pErrorCode);
    if (U_FAILURE(*pErrorCode)) {
        return nullptr;
    }
    return reinterpret_cast<UMutableCPTrie *>(trie.orphan());
}

U_CAPI UMutableCPTrie * U_EXPORT2
umutablecptrie_clone(const UMutableCPTrie *other, UErrorCode *pErrorCode) {
    if (U_FAILURE(*pErrorCode)) {
        return nullptr;
    }
    if (other == nullptr) {
        return nullptr;
    }
    LocalPointer<MutableCodePointTrie> clone(
        new MutableCodePointTrie(*reinterpret_cast<const MutableCodePointTrie *>(other), *pErrorCode), *pErrorCode);
    if (U_FAILURE(*pErrorCode)) {
        return nullptr;
    }
    return reinterpret_cast<UMutableCPTrie *>(clone.orphan());
}

U_CAPI void U_EXPORT2
umutablecptrie_close(UMutableCPTrie *trie) {
    delete reinterpret_cast<MutableCodePointTrie *>(trie);
}

U_CAPI UMutableCPTrie * U_EXPORT2
umutablecptrie_fromUCPMap(const UCPMap *map, UErrorCode *pErrorCode) {
    if (U_FAILURE(*pErrorCode)) {
        return nullptr;
    }
    if (map == nullptr) {
        *pErrorCode = U_ILLEGAL_ARGUMENT_ERROR;
        return nullptr;
    }
    return reinterpret_cast<UMutableCPTrie *>(MutableCodePointTrie::fromUCPMap(map, *pErrorCode));
}

U_CAPI UMutableCPTrie * U_EXPORT2
umutablecptrie_fromUCPTrie(const UCPTrie *trie, UErrorCode *pErrorCode) {
    if (U_FAILURE(*pErrorCode)) {
        return nullptr;
    }
    if (trie == nullptr) {
        *pErrorCode = U_ILLEGAL_ARGUMENT_ERROR;
        return nullptr;
    }
    return reinterpret_cast<UMutableCPTrie *>(MutableCodePointTrie::fromUCPTrie(trie, *pErrorCode));
}

U_CAPI uint32_t U_EXPORT2
umutablecptrie_get(const UMutableCPTrie *trie, UChar32 c) {
    return reinterpret_cast<const MutableCodePointTrie *>(trie)->get(c);
}

namespace {

UChar32 getRange(const void *trie, UChar32 start,
                 UCPMapValueFilter *filter, const void *context, uint32_t *pValue) {
    return reinterpret_cast<const MutableCodePointTrie *>(trie)->
        getRange(start, filter, context, pValue);
}

}  // namespace

U_CAPI UChar32 U_EXPORT2
umutablecptrie_getRange(const UMutableCPTrie *trie, UChar32 start,
                        UCPMapRangeOption option, uint32_t surrogateValue,
                        UCPMapValueFilter *filter, const void *context, uint32_t *pValue) {
    return ucptrie_internalGetRange(getRange, trie, start,
                                    option, surrogateValue,
                                    filter, context, pValue);
}

U_CAPI void U_EXPORT2
umutablecptrie_set(UMutableCPTrie *trie, UChar32 c, uint32_t value, UErrorCode *pErrorCode) {
    if (U_FAILURE(*pErrorCode)) {
        return;
    }
    reinterpret_cast<MutableCodePointTrie *>(trie)->set(c, value, *pErrorCode);
}

U_CAPI void U_EXPORT2
umutablecptrie_setRange(UMutableCPTrie *trie, UChar32 start, UChar32 end,
                   uint32_t value, UErrorCode *pErrorCode) {
    if (U_FAILURE(*pErrorCode)) {
        return;
    }
    reinterpret_cast<MutableCodePointTrie *>(trie)->setRange(start, end, value, *pErrorCode);
}

/* Compact and internally serialize the trie. */
U_CAPI UCPTrie * U_EXPORT2
umutablecptrie_buildImmutable(UMutableCPTrie *trie, UCPTrieType type, UCPTrieValueWidth valueWidth,
                              UErrorCode *pErrorCode) {
    if (U_FAILURE(*pErrorCode)) {
        return nullptr;
    }
    return reinterpret_cast<MutableCodePointTrie *>(trie)->build(type, valueWidth, *pErrorCode);
}

#ifdef UCPTRIE_DEBUG
U_CFUNC void umutablecptrie_setName(UMutableCPTrie *trie, const char *name) {
    reinterpret_cast<MutableCodePointTrie *>(trie)->name = name;
}
#endif