summaryrefslogtreecommitdiffstats
path: root/modules/brotli/enc/encode.c
blob: 141e70aa2a31344fd4cd047548a7ae9ed9833c89 (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
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
/* Copyright 2013 Google Inc. All Rights Reserved.

   Distributed under MIT license.
   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/

/* Implementation of Brotli compressor. */

#include <brotli/encode.h>

#include <stdlib.h>  /* free, malloc */
#include <string.h>  /* memcpy, memset */

#include "../common/constants.h"
#include "../common/context.h"
#include "../common/platform.h"
#include "../common/version.h"
#include "./backward_references.h"
#include "./backward_references_hq.h"
#include "./bit_cost.h"
#include "./brotli_bit_stream.h"
#include "./compress_fragment.h"
#include "./compress_fragment_two_pass.h"
#include "./encoder_dict.h"
#include "./entropy_encode.h"
#include "./fast_log.h"
#include "./hash.h"
#include "./histogram.h"
#include "./memory.h"
#include "./metablock.h"
#include "./prefix.h"
#include "./quality.h"
#include "./ringbuffer.h"
#include "./utf8_util.h"
#include "./write_bits.h"

#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif

#define COPY_ARRAY(dst, src) memcpy(dst, src, sizeof(src));

typedef enum BrotliEncoderStreamState {
  /* Default state. */
  BROTLI_STREAM_PROCESSING = 0,
  /* Intermediate state; after next block is emitted, byte-padding should be
     performed before getting back to default state. */
  BROTLI_STREAM_FLUSH_REQUESTED = 1,
  /* Last metablock was produced; no more input is acceptable. */
  BROTLI_STREAM_FINISHED = 2,
  /* Flushing compressed block and writing meta-data block header. */
  BROTLI_STREAM_METADATA_HEAD = 3,
  /* Writing metadata block body. */
  BROTLI_STREAM_METADATA_BODY = 4
} BrotliEncoderStreamState;

typedef struct BrotliEncoderStateStruct {
  BrotliEncoderParams params;

  MemoryManager memory_manager_;

  HasherHandle hasher_;
  uint64_t input_pos_;
  RingBuffer ringbuffer_;
  size_t cmd_alloc_size_;
  Command* commands_;
  size_t num_commands_;
  size_t num_literals_;
  size_t last_insert_len_;
  uint64_t last_flush_pos_;
  uint64_t last_processed_pos_;
  int dist_cache_[BROTLI_NUM_DISTANCE_SHORT_CODES];
  int saved_dist_cache_[4];
  uint16_t last_bytes_;
  uint8_t last_bytes_bits_;
  uint8_t prev_byte_;
  uint8_t prev_byte2_;
  size_t storage_size_;
  uint8_t* storage_;
  /* Hash table for FAST_ONE_PASS_COMPRESSION_QUALITY mode. */
  int small_table_[1 << 10];  /* 4KiB */
  int* large_table_;          /* Allocated only when needed */
  size_t large_table_size_;
  /* Command and distance prefix codes (each 64 symbols, stored back-to-back)
     used for the next block in FAST_ONE_PASS_COMPRESSION_QUALITY. The command
     prefix code is over a smaller alphabet with the following 64 symbols:
        0 - 15: insert length code 0, copy length code 0 - 15, same distance
       16 - 39: insert length code 0, copy length code 0 - 23
       40 - 63: insert length code 0 - 23, copy length code 0
     Note that symbols 16 and 40 represent the same code in the full alphabet,
     but we do not use either of them in FAST_ONE_PASS_COMPRESSION_QUALITY. */
  uint8_t cmd_depths_[128];
  uint16_t cmd_bits_[128];
  /* The compressed form of the command and distance prefix codes for the next
     block in FAST_ONE_PASS_COMPRESSION_QUALITY. */
  uint8_t cmd_code_[512];
  size_t cmd_code_numbits_;
  /* Command and literal buffers for FAST_TWO_PASS_COMPRESSION_QUALITY. */
  uint32_t* command_buf_;
  uint8_t* literal_buf_;

  uint8_t* next_out_;
  size_t available_out_;
  size_t total_out_;
  /* Temporary buffer for padding flush bits or metadata block header / body. */
  union {
    uint64_t u64[2];
    uint8_t u8[16];
  } tiny_buf_;
  uint32_t remaining_metadata_bytes_;
  BrotliEncoderStreamState stream_state_;

  BROTLI_BOOL is_last_block_emitted_;
  BROTLI_BOOL is_initialized_;
} BrotliEncoderStateStruct;

static BROTLI_BOOL EnsureInitialized(BrotliEncoderState* s);

static size_t InputBlockSize(BrotliEncoderState* s) {
  return (size_t)1 << s->params.lgblock;
}

static uint64_t UnprocessedInputSize(BrotliEncoderState* s) {
  return s->input_pos_ - s->last_processed_pos_;
}

static size_t RemainingInputBlockSize(BrotliEncoderState* s) {
  const uint64_t delta = UnprocessedInputSize(s);
  size_t block_size = InputBlockSize(s);
  if (delta >= block_size) return 0;
  return block_size - (size_t)delta;
}

BROTLI_BOOL BrotliEncoderSetParameter(
    BrotliEncoderState* state, BrotliEncoderParameter p, uint32_t value) {
  /* Changing parameters on the fly is not implemented yet. */
  if (state->is_initialized_) return BROTLI_FALSE;
  /* TODO: Validate/clamp parameters here. */
  switch (p) {
    case BROTLI_PARAM_MODE:
      state->params.mode = (BrotliEncoderMode)value;
      return BROTLI_TRUE;

    case BROTLI_PARAM_QUALITY:
      state->params.quality = (int)value;
      return BROTLI_TRUE;

    case BROTLI_PARAM_LGWIN:
      state->params.lgwin = (int)value;
      return BROTLI_TRUE;

    case BROTLI_PARAM_LGBLOCK:
      state->params.lgblock = (int)value;
      return BROTLI_TRUE;

    case BROTLI_PARAM_DISABLE_LITERAL_CONTEXT_MODELING:
      if ((value != 0) && (value != 1)) return BROTLI_FALSE;
      state->params.disable_literal_context_modeling = TO_BROTLI_BOOL(!!value);
      return BROTLI_TRUE;

    case BROTLI_PARAM_SIZE_HINT:
      state->params.size_hint = value;
      return BROTLI_TRUE;

    case BROTLI_PARAM_LARGE_WINDOW:
      state->params.large_window = TO_BROTLI_BOOL(!!value);
      return BROTLI_TRUE;

    case BROTLI_PARAM_NPOSTFIX:
      state->params.dist.distance_postfix_bits = value;
      return BROTLI_TRUE;

    case BROTLI_PARAM_NDIRECT:
      state->params.dist.num_direct_distance_codes = value;
      return BROTLI_TRUE;

    default: return BROTLI_FALSE;
  }
}

/* Wraps 64-bit input position to 32-bit ring-buffer position preserving
   "not-a-first-lap" feature. */
static uint32_t WrapPosition(uint64_t position) {
  uint32_t result = (uint32_t)position;
  uint64_t gb = position >> 30;
  if (gb > 2) {
    /* Wrap every 2GiB; The first 3GB are continuous. */
    result = (result & ((1u << 30) - 1)) | ((uint32_t)((gb - 1) & 1) + 1) << 30;
  }
  return result;
}

static uint8_t* GetBrotliStorage(BrotliEncoderState* s, size_t size) {
  MemoryManager* m = &s->memory_manager_;
  if (s->storage_size_ < size) {
    BROTLI_FREE(m, s->storage_);
    s->storage_ = BROTLI_ALLOC(m, uint8_t, size);
    if (BROTLI_IS_OOM(m)) return NULL;
    s->storage_size_ = size;
  }
  return s->storage_;
}

static size_t HashTableSize(size_t max_table_size, size_t input_size) {
  size_t htsize = 256;
  while (htsize < max_table_size && htsize < input_size) {
    htsize <<= 1;
  }
  return htsize;
}

static int* GetHashTable(BrotliEncoderState* s, int quality,
                         size_t input_size, size_t* table_size) {
  /* Use smaller hash table when input.size() is smaller, since we
     fill the table, incurring O(hash table size) overhead for
     compression, and if the input is short, we won't need that
     many hash table entries anyway. */
  MemoryManager* m = &s->memory_manager_;
  const size_t max_table_size = MaxHashTableSize(quality);
  size_t htsize = HashTableSize(max_table_size, input_size);
  int* table;
  BROTLI_DCHECK(max_table_size >= 256);
  if (quality == FAST_ONE_PASS_COMPRESSION_QUALITY) {
    /* Only odd shifts are supported by fast-one-pass. */
    if ((htsize & 0xAAAAA) == 0) {
      htsize <<= 1;
    }
  }

  if (htsize <= sizeof(s->small_table_) / sizeof(s->small_table_[0])) {
    table = s->small_table_;
  } else {
    if (htsize > s->large_table_size_) {
      s->large_table_size_ = htsize;
      BROTLI_FREE(m, s->large_table_);
      s->large_table_ = BROTLI_ALLOC(m, int, htsize);
      if (BROTLI_IS_OOM(m)) return 0;
    }
    table = s->large_table_;
  }

  *table_size = htsize;
  memset(table, 0, htsize * sizeof(*table));
  return table;
}

static void EncodeWindowBits(int lgwin, BROTLI_BOOL large_window,
    uint16_t* last_bytes, uint8_t* last_bytes_bits) {
  if (large_window) {
    *last_bytes = (uint16_t)(((lgwin & 0x3F) << 8) | 0x11);
    *last_bytes_bits = 14;
  } else {
    if (lgwin == 16) {
      *last_bytes = 0;
      *last_bytes_bits = 1;
    } else if (lgwin == 17) {
      *last_bytes = 1;
      *last_bytes_bits = 7;
    } else if (lgwin > 17) {
      *last_bytes = (uint16_t)(((lgwin - 17) << 1) | 0x01);
      *last_bytes_bits = 4;
    } else {
      *last_bytes = (uint16_t)(((lgwin - 8) << 4) | 0x01);
      *last_bytes_bits = 7;
    }
  }
}

/* Initializes the command and distance prefix codes for the first block. */
static void InitCommandPrefixCodes(uint8_t cmd_depths[128],
                                   uint16_t cmd_bits[128],
                                   uint8_t cmd_code[512],
                                   size_t* cmd_code_numbits) {
  static const uint8_t kDefaultCommandDepths[128] = {
    0, 4, 4, 5, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8,
    0, 0, 0, 4, 4, 4, 4, 4, 5, 5, 6, 6, 6, 6, 7, 7,
    7, 7, 10, 10, 10, 10, 10, 10, 0, 4, 4, 5, 5, 5, 6, 6,
    7, 8, 8, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
    5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    6, 6, 6, 6, 6, 6, 5, 5, 5, 5, 5, 5, 4, 4, 4, 4,
    4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 7, 7, 7, 8, 10,
    12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
  };
  static const uint16_t kDefaultCommandBits[128] = {
    0,   0,   8,   9,   3,  35,   7,   71,
    39, 103,  23,  47, 175, 111, 239,   31,
    0,   0,   0,   4,  12,   2,  10,    6,
    13,  29,  11,  43,  27,  59,  87,   55,
    15,  79, 319, 831, 191, 703, 447,  959,
    0,  14,   1,  25,   5,  21,  19,   51,
    119, 159,  95, 223, 479, 991,  63,  575,
    127, 639, 383, 895, 255, 767, 511, 1023,
    14, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    27, 59, 7, 39, 23, 55, 30, 1, 17, 9, 25, 5, 0, 8, 4, 12,
    2, 10, 6, 21, 13, 29, 3, 19, 11, 15, 47, 31, 95, 63, 127, 255,
    767, 2815, 1791, 3839, 511, 2559, 1535, 3583, 1023, 3071, 2047, 4095,
  };
  static const uint8_t kDefaultCommandCode[] = {
    0xff, 0x77, 0xd5, 0xbf, 0xe7, 0xde, 0xea, 0x9e, 0x51, 0x5d, 0xde, 0xc6,
    0x70, 0x57, 0xbc, 0x58, 0x58, 0x58, 0xd8, 0xd8, 0x58, 0xd5, 0xcb, 0x8c,
    0xea, 0xe0, 0xc3, 0x87, 0x1f, 0x83, 0xc1, 0x60, 0x1c, 0x67, 0xb2, 0xaa,
    0x06, 0x83, 0xc1, 0x60, 0x30, 0x18, 0xcc, 0xa1, 0xce, 0x88, 0x54, 0x94,
    0x46, 0xe1, 0xb0, 0xd0, 0x4e, 0xb2, 0xf7, 0x04, 0x00,
  };
  static const size_t kDefaultCommandCodeNumBits = 448;
  COPY_ARRAY(cmd_depths, kDefaultCommandDepths);
  COPY_ARRAY(cmd_bits, kDefaultCommandBits);

  /* Initialize the pre-compressed form of the command and distance prefix
     codes. */
  COPY_ARRAY(cmd_code, kDefaultCommandCode);
  *cmd_code_numbits = kDefaultCommandCodeNumBits;
}

/* Decide about the context map based on the ability of the prediction
   ability of the previous byte UTF8-prefix on the next byte. The
   prediction ability is calculated as Shannon entropy. Here we need
   Shannon entropy instead of 'BitsEntropy' since the prefix will be
   encoded with the remaining 6 bits of the following byte, and
   BitsEntropy will assume that symbol to be stored alone using Huffman
   coding. */
static void ChooseContextMap(int quality,
                             uint32_t* bigram_histo,
                             size_t* num_literal_contexts,
                             const uint32_t** literal_context_map) {
  static const uint32_t kStaticContextMapContinuation[64] = {
    1, 1, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  };
  static const uint32_t kStaticContextMapSimpleUTF8[64] = {
    0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  };

  uint32_t monogram_histo[3] = { 0 };
  uint32_t two_prefix_histo[6] = { 0 };
  size_t total;
  size_t i;
  size_t dummy;
  double entropy[4];
  for (i = 0; i < 9; ++i) {
    monogram_histo[i % 3] += bigram_histo[i];
    two_prefix_histo[i % 6] += bigram_histo[i];
  }
  entropy[1] = ShannonEntropy(monogram_histo, 3, &dummy);
  entropy[2] = (ShannonEntropy(two_prefix_histo, 3, &dummy) +
                ShannonEntropy(two_prefix_histo + 3, 3, &dummy));
  entropy[3] = 0;
  for (i = 0; i < 3; ++i) {
    entropy[3] += ShannonEntropy(bigram_histo + 3 * i, 3, &dummy);
  }

  total = monogram_histo[0] + monogram_histo[1] + monogram_histo[2];
  BROTLI_DCHECK(total != 0);
  entropy[0] = 1.0 / (double)total;
  entropy[1] *= entropy[0];
  entropy[2] *= entropy[0];
  entropy[3] *= entropy[0];

  if (quality < MIN_QUALITY_FOR_HQ_CONTEXT_MODELING) {
    /* 3 context models is a bit slower, don't use it at lower qualities. */
    entropy[3] = entropy[1] * 10;
  }
  /* If expected savings by symbol are less than 0.2 bits, skip the
     context modeling -- in exchange for faster decoding speed. */
  if (entropy[1] - entropy[2] < 0.2 &&
      entropy[1] - entropy[3] < 0.2) {
    *num_literal_contexts = 1;
  } else if (entropy[2] - entropy[3] < 0.02) {
    *num_literal_contexts = 2;
    *literal_context_map = kStaticContextMapSimpleUTF8;
  } else {
    *num_literal_contexts = 3;
    *literal_context_map = kStaticContextMapContinuation;
  }
}

/* Decide if we want to use a more complex static context map containing 13
   context values, based on the entropy reduction of histograms over the
   first 5 bits of literals. */
static BROTLI_BOOL ShouldUseComplexStaticContextMap(const uint8_t* input,
    size_t start_pos, size_t length, size_t mask, int quality, size_t size_hint,
    size_t* num_literal_contexts, const uint32_t** literal_context_map) {
  static const uint32_t kStaticContextMapComplexUTF8[64] = {
    11, 11, 12, 12, /* 0 special */
    0, 0, 0, 0, /* 4 lf */
    1, 1, 9, 9, /* 8 space */
    2, 2, 2, 2, /* !, first after space/lf and after something else. */
    1, 1, 1, 1, /* " */
    8, 3, 3, 3, /* % */
    1, 1, 1, 1, /* ({[ */
    2, 2, 2, 2, /* }]) */
    8, 4, 4, 4, /* :; */
    8, 7, 4, 4, /* . */
    8, 0, 0, 0, /* > */
    3, 3, 3, 3, /* [0..9] */
    5, 5, 10, 5, /* [A-Z] */
    5, 5, 10, 5,
    6, 6, 6, 6, /* [a-z] */
    6, 6, 6, 6,
  };
  BROTLI_UNUSED(quality);
  /* Try the more complex static context map only for long data. */
  if (size_hint < (1 << 20)) {
    return BROTLI_FALSE;
  } else {
    const size_t end_pos = start_pos + length;
    /* To make entropy calculations faster and to fit on the stack, we collect
       histograms over the 5 most significant bits of literals. One histogram
       without context and 13 additional histograms for each context value. */
    uint32_t combined_histo[32] = { 0 };
    uint32_t context_histo[13][32] = { { 0 } };
    uint32_t total = 0;
    double entropy[3];
    size_t dummy;
    size_t i;
    ContextLut utf8_lut = BROTLI_CONTEXT_LUT(CONTEXT_UTF8);
    for (; start_pos + 64 <= end_pos; start_pos += 4096) {
      const size_t stride_end_pos = start_pos + 64;
      uint8_t prev2 = input[start_pos & mask];
      uint8_t prev1 = input[(start_pos + 1) & mask];
      size_t pos;
      /* To make the analysis of the data faster we only examine 64 byte long
         strides at every 4kB intervals. */
      for (pos = start_pos + 2; pos < stride_end_pos; ++pos) {
        const uint8_t literal = input[pos & mask];
        const uint8_t context = (uint8_t)kStaticContextMapComplexUTF8[
            BROTLI_CONTEXT(prev1, prev2, utf8_lut)];
        ++total;
        ++combined_histo[literal >> 3];
        ++context_histo[context][literal >> 3];
        prev2 = prev1;
        prev1 = literal;
      }
    }
    entropy[1] = ShannonEntropy(combined_histo, 32, &dummy);
    entropy[2] = 0;
    for (i = 0; i < 13; ++i) {
      entropy[2] += ShannonEntropy(&context_histo[i][0], 32, &dummy);
    }
    entropy[0] = 1.0 / (double)total;
    entropy[1] *= entropy[0];
    entropy[2] *= entropy[0];
    /* The triggering heuristics below were tuned by compressing the individual
       files of the silesia corpus. If we skip this kind of context modeling
       for not very well compressible input (i.e. entropy using context modeling
       is 60% of maximal entropy) or if expected savings by symbol are less
       than 0.2 bits, then in every case when it triggers, the final compression
       ratio is improved. Note however that this heuristics might be too strict
       for some cases and could be tuned further. */
    if (entropy[2] > 3.0 || entropy[1] - entropy[2] < 0.2) {
      return BROTLI_FALSE;
    } else {
      *num_literal_contexts = 13;
      *literal_context_map = kStaticContextMapComplexUTF8;
      return BROTLI_TRUE;
    }
  }
}

static void DecideOverLiteralContextModeling(const uint8_t* input,
    size_t start_pos, size_t length, size_t mask, int quality, size_t size_hint,
    size_t* num_literal_contexts, const uint32_t** literal_context_map) {
  if (quality < MIN_QUALITY_FOR_CONTEXT_MODELING || length < 64) {
    return;
  } else if (ShouldUseComplexStaticContextMap(
      input, start_pos, length, mask, quality, size_hint,
      num_literal_contexts, literal_context_map)) {
    /* Context map was already set, nothing else to do. */
  } else {
    /* Gather bi-gram data of the UTF8 byte prefixes. To make the analysis of
       UTF8 data faster we only examine 64 byte long strides at every 4kB
       intervals. */
    const size_t end_pos = start_pos + length;
    uint32_t bigram_prefix_histo[9] = { 0 };
    for (; start_pos + 64 <= end_pos; start_pos += 4096) {
      static const int lut[4] = { 0, 0, 1, 2 };
      const size_t stride_end_pos = start_pos + 64;
      int prev = lut[input[start_pos & mask] >> 6] * 3;
      size_t pos;
      for (pos = start_pos + 1; pos < stride_end_pos; ++pos) {
        const uint8_t literal = input[pos & mask];
        ++bigram_prefix_histo[prev + lut[literal >> 6]];
        prev = lut[literal >> 6] * 3;
      }
    }
    ChooseContextMap(quality, &bigram_prefix_histo[0], num_literal_contexts,
                     literal_context_map);
  }
}

static BROTLI_BOOL ShouldCompress(
    const uint8_t* data, const size_t mask, const uint64_t last_flush_pos,
    const size_t bytes, const size_t num_literals, const size_t num_commands) {
  /* TODO: find more precise minimal block overhead. */
  if (bytes <= 2) return BROTLI_FALSE;
  if (num_commands < (bytes >> 8) + 2) {
    if (num_literals > 0.99 * (double)bytes) {
      uint32_t literal_histo[256] = { 0 };
      static const uint32_t kSampleRate = 13;
      static const double kMinEntropy = 7.92;
      const double bit_cost_threshold =
          (double)bytes * kMinEntropy / kSampleRate;
      size_t t = (bytes + kSampleRate - 1) / kSampleRate;
      uint32_t pos = (uint32_t)last_flush_pos;
      size_t i;
      for (i = 0; i < t; i++) {
        ++literal_histo[data[pos & mask]];
        pos += kSampleRate;
      }
      if (BitsEntropy(literal_histo, 256) > bit_cost_threshold) {
        return BROTLI_FALSE;
      }
    }
  }
  return BROTLI_TRUE;
}

/* Chooses the literal context mode for a metablock */
static ContextType ChooseContextMode(const BrotliEncoderParams* params,
    const uint8_t* data, const size_t pos, const size_t mask,
    const size_t length) {
  /* We only do the computation for the option of something else than
     CONTEXT_UTF8 for the highest qualities */
  if (params->quality >= MIN_QUALITY_FOR_HQ_BLOCK_SPLITTING &&
      !BrotliIsMostlyUTF8(data, pos, mask, length, kMinUTF8Ratio)) {
    return CONTEXT_SIGNED;
  }
  return CONTEXT_UTF8;
}

static void WriteMetaBlockInternal(MemoryManager* m,
                                   const uint8_t* data,
                                   const size_t mask,
                                   const uint64_t last_flush_pos,
                                   const size_t bytes,
                                   const BROTLI_BOOL is_last,
                                   ContextType literal_context_mode,
                                   const BrotliEncoderParams* params,
                                   const uint8_t prev_byte,
                                   const uint8_t prev_byte2,
                                   const size_t num_literals,
                                   const size_t num_commands,
                                   Command* commands,
                                   const int* saved_dist_cache,
                                   int* dist_cache,
                                   size_t* storage_ix,
                                   uint8_t* storage) {
  const uint32_t wrapped_last_flush_pos = WrapPosition(last_flush_pos);
  uint16_t last_bytes;
  uint8_t last_bytes_bits;
  ContextLut literal_context_lut = BROTLI_CONTEXT_LUT(literal_context_mode);
  BrotliEncoderParams block_params = *params;

  if (bytes == 0) {
    /* Write the ISLAST and ISEMPTY bits. */
    BrotliWriteBits(2, 3, storage_ix, storage);
    *storage_ix = (*storage_ix + 7u) & ~7u;
    return;
  }

  if (!ShouldCompress(data, mask, last_flush_pos, bytes,
                      num_literals, num_commands)) {
    /* Restore the distance cache, as its last update by
       CreateBackwardReferences is now unused. */
    memcpy(dist_cache, saved_dist_cache, 4 * sizeof(dist_cache[0]));
    BrotliStoreUncompressedMetaBlock(is_last, data,
                                     wrapped_last_flush_pos, mask, bytes,
                                     storage_ix, storage);
    return;
  }

  BROTLI_DCHECK(*storage_ix <= 14);
  last_bytes = (uint16_t)((storage[1] << 8) | storage[0]);
  last_bytes_bits = (uint8_t)(*storage_ix);
  if (params->quality <= MAX_QUALITY_FOR_STATIC_ENTROPY_CODES) {
    BrotliStoreMetaBlockFast(m, data, wrapped_last_flush_pos,
                             bytes, mask, is_last, params,
                             commands, num_commands,
                             storage_ix, storage);
    if (BROTLI_IS_OOM(m)) return;
  } else if (params->quality < MIN_QUALITY_FOR_BLOCK_SPLIT) {
    BrotliStoreMetaBlockTrivial(m, data, wrapped_last_flush_pos,
                                bytes, mask, is_last, params,
                                commands, num_commands,
                                storage_ix, storage);
    if (BROTLI_IS_OOM(m)) return;
  } else {
    MetaBlockSplit mb;
    InitMetaBlockSplit(&mb);
    if (params->quality < MIN_QUALITY_FOR_HQ_BLOCK_SPLITTING) {
      size_t num_literal_contexts = 1;
      const uint32_t* literal_context_map = NULL;
      if (!params->disable_literal_context_modeling) {
        DecideOverLiteralContextModeling(
            data, wrapped_last_flush_pos, bytes, mask, params->quality,
            params->size_hint, &num_literal_contexts,
            &literal_context_map);
      }
      BrotliBuildMetaBlockGreedy(m, data, wrapped_last_flush_pos, mask,
          prev_byte, prev_byte2, literal_context_lut, num_literal_contexts,
          literal_context_map, commands, num_commands, &mb);
      if (BROTLI_IS_OOM(m)) return;
    } else {
      BrotliBuildMetaBlock(m, data, wrapped_last_flush_pos, mask, &block_params,
                           prev_byte, prev_byte2,
                           commands, num_commands,
                           literal_context_mode,
                           &mb);
      if (BROTLI_IS_OOM(m)) return;
    }
    if (params->quality >= MIN_QUALITY_FOR_OPTIMIZE_HISTOGRAMS) {
      /* The number of distance symbols effectively used for distance
         histograms. It might be less than distance alphabet size
         for "Large Window Brotli" (32-bit). */
      uint32_t num_effective_dist_codes = block_params.dist.alphabet_size;
      if (num_effective_dist_codes > BROTLI_NUM_HISTOGRAM_DISTANCE_SYMBOLS) {
        num_effective_dist_codes = BROTLI_NUM_HISTOGRAM_DISTANCE_SYMBOLS;
      }
      BrotliOptimizeHistograms(num_effective_dist_codes, &mb);
    }
    BrotliStoreMetaBlock(m, data, wrapped_last_flush_pos, bytes, mask,
                         prev_byte, prev_byte2,
                         is_last,
                         &block_params,
                         literal_context_mode,
                         commands, num_commands,
                         &mb,
                         storage_ix, storage);
    if (BROTLI_IS_OOM(m)) return;
    DestroyMetaBlockSplit(m, &mb);
  }
  if (bytes + 4 < (*storage_ix >> 3)) {
    /* Restore the distance cache and last byte. */
    memcpy(dist_cache, saved_dist_cache, 4 * sizeof(dist_cache[0]));
    storage[0] = (uint8_t)last_bytes;
    storage[1] = (uint8_t)(last_bytes >> 8);
    *storage_ix = last_bytes_bits;
    BrotliStoreUncompressedMetaBlock(is_last, data,
                                     wrapped_last_flush_pos, mask,
                                     bytes, storage_ix, storage);
  }
}

static void ChooseDistanceParams(BrotliEncoderParams* params) {
  uint32_t distance_postfix_bits = 0;
  uint32_t num_direct_distance_codes = 0;

  if (params->quality >= MIN_QUALITY_FOR_NONZERO_DISTANCE_PARAMS) {
    uint32_t ndirect_msb;
    if (params->mode == BROTLI_MODE_FONT) {
      distance_postfix_bits = 1;
      num_direct_distance_codes = 12;
    } else {
      distance_postfix_bits = params->dist.distance_postfix_bits;
      num_direct_distance_codes = params->dist.num_direct_distance_codes;
    }
    ndirect_msb = (num_direct_distance_codes >> distance_postfix_bits) & 0x0F;
    if (distance_postfix_bits > BROTLI_MAX_NPOSTFIX ||
        num_direct_distance_codes > BROTLI_MAX_NDIRECT ||
        (ndirect_msb << distance_postfix_bits) != num_direct_distance_codes) {
      distance_postfix_bits = 0;
      num_direct_distance_codes = 0;
    }
  }

  BrotliInitDistanceParams(
      params, distance_postfix_bits, num_direct_distance_codes);
}

static BROTLI_BOOL EnsureInitialized(BrotliEncoderState* s) {
  if (BROTLI_IS_OOM(&s->memory_manager_)) return BROTLI_FALSE;
  if (s->is_initialized_) return BROTLI_TRUE;

  s->last_bytes_bits_ = 0;
  s->last_bytes_ = 0;
  s->remaining_metadata_bytes_ = BROTLI_UINT32_MAX;

  SanitizeParams(&s->params);
  s->params.lgblock = ComputeLgBlock(&s->params);
  ChooseDistanceParams(&s->params);

  RingBufferSetup(&s->params, &s->ringbuffer_);

  /* Initialize last byte with stream header. */
  {
    int lgwin = s->params.lgwin;
    if (s->params.quality == FAST_ONE_PASS_COMPRESSION_QUALITY ||
        s->params.quality == FAST_TWO_PASS_COMPRESSION_QUALITY) {
      lgwin = BROTLI_MAX(int, lgwin, 18);
    }
    EncodeWindowBits(lgwin, s->params.large_window,
                     &s->last_bytes_, &s->last_bytes_bits_);
  }

  if (s->params.quality == FAST_ONE_PASS_COMPRESSION_QUALITY) {
    InitCommandPrefixCodes(s->cmd_depths_, s->cmd_bits_,
                           s->cmd_code_, &s->cmd_code_numbits_);
  }

  s->is_initialized_ = BROTLI_TRUE;
  return BROTLI_TRUE;
}

static void BrotliEncoderInitParams(BrotliEncoderParams* params) {
  params->mode = BROTLI_DEFAULT_MODE;
  params->large_window = BROTLI_FALSE;
  params->quality = BROTLI_DEFAULT_QUALITY;
  params->lgwin = BROTLI_DEFAULT_WINDOW;
  params->lgblock = 0;
  params->size_hint = 0;
  params->disable_literal_context_modeling = BROTLI_FALSE;
  BrotliInitEncoderDictionary(&params->dictionary);
  params->dist.distance_postfix_bits = 0;
  params->dist.num_direct_distance_codes = 0;
  params->dist.alphabet_size =
      BROTLI_DISTANCE_ALPHABET_SIZE(0, 0, BROTLI_MAX_DISTANCE_BITS);
  params->dist.max_distance = BROTLI_MAX_DISTANCE;
}

static void BrotliEncoderInitState(BrotliEncoderState* s) {
  BrotliEncoderInitParams(&s->params);
  s->input_pos_ = 0;
  s->num_commands_ = 0;
  s->num_literals_ = 0;
  s->last_insert_len_ = 0;
  s->last_flush_pos_ = 0;
  s->last_processed_pos_ = 0;
  s->prev_byte_ = 0;
  s->prev_byte2_ = 0;
  s->storage_size_ = 0;
  s->storage_ = 0;
  s->hasher_ = NULL;
  s->large_table_ = NULL;
  s->large_table_size_ = 0;
  s->cmd_code_numbits_ = 0;
  s->command_buf_ = NULL;
  s->literal_buf_ = NULL;
  s->next_out_ = NULL;
  s->available_out_ = 0;
  s->total_out_ = 0;
  s->stream_state_ = BROTLI_STREAM_PROCESSING;
  s->is_last_block_emitted_ = BROTLI_FALSE;
  s->is_initialized_ = BROTLI_FALSE;

  RingBufferInit(&s->ringbuffer_);

  s->commands_ = 0;
  s->cmd_alloc_size_ = 0;

  /* Initialize distance cache. */
  s->dist_cache_[0] = 4;
  s->dist_cache_[1] = 11;
  s->dist_cache_[2] = 15;
  s->dist_cache_[3] = 16;
  /* Save the state of the distance cache in case we need to restore it for
     emitting an uncompressed block. */
  memcpy(s->saved_dist_cache_, s->dist_cache_, sizeof(s->saved_dist_cache_));
}

BrotliEncoderState* BrotliEncoderCreateInstance(
    brotli_alloc_func alloc_func, brotli_free_func free_func, void* opaque) {
  BrotliEncoderState* state = 0;
  if (!alloc_func && !free_func) {
    state = (BrotliEncoderState*)malloc(sizeof(BrotliEncoderState));
  } else if (alloc_func && free_func) {
    state = (BrotliEncoderState*)alloc_func(opaque, sizeof(BrotliEncoderState));
  }
  if (state == 0) {
    /* BROTLI_DUMP(); */
    return 0;
  }
  BrotliInitMemoryManager(
      &state->memory_manager_, alloc_func, free_func, opaque);
  BrotliEncoderInitState(state);
  return state;
}

static void BrotliEncoderCleanupState(BrotliEncoderState* s) {
  MemoryManager* m = &s->memory_manager_;
  if (BROTLI_IS_OOM(m)) {
    BrotliWipeOutMemoryManager(m);
    return;
  }
  BROTLI_FREE(m, s->storage_);
  BROTLI_FREE(m, s->commands_);
  RingBufferFree(m, &s->ringbuffer_);
  DestroyHasher(m, &s->hasher_);
  BROTLI_FREE(m, s->large_table_);
  BROTLI_FREE(m, s->command_buf_);
  BROTLI_FREE(m, s->literal_buf_);
}

/* Deinitializes and frees BrotliEncoderState instance. */
void BrotliEncoderDestroyInstance(BrotliEncoderState* state) {
  if (!state) {
    return;
  } else {
    MemoryManager* m = &state->memory_manager_;
    brotli_free_func free_func = m->free_func;
    void* opaque = m->opaque;
    BrotliEncoderCleanupState(state);
    free_func(opaque, state);
  }
}

/*
   Copies the given input data to the internal ring buffer of the compressor.
   No processing of the data occurs at this time and this function can be
   called multiple times before calling WriteBrotliData() to process the
   accumulated input. At most input_block_size() bytes of input data can be
   copied to the ring buffer, otherwise the next WriteBrotliData() will fail.
 */
static void CopyInputToRingBuffer(BrotliEncoderState* s,
                                  const size_t input_size,
                                  const uint8_t* input_buffer) {
  RingBuffer* ringbuffer_ = &s->ringbuffer_;
  MemoryManager* m = &s->memory_manager_;
  RingBufferWrite(m, input_buffer, input_size, ringbuffer_);
  if (BROTLI_IS_OOM(m)) return;
  s->input_pos_ += input_size;

  /* TL;DR: If needed, initialize 7 more bytes in the ring buffer to make the
     hashing not depend on uninitialized data. This makes compression
     deterministic and it prevents uninitialized memory warnings in Valgrind.
     Even without erasing, the output would be valid (but nondeterministic).

     Background information: The compressor stores short (at most 8 bytes)
     substrings of the input already read in a hash table, and detects
     repetitions by looking up such substrings in the hash table. If it
     can find a substring, it checks whether the substring is really there
     in the ring buffer (or it's just a hash collision). Should the hash
     table become corrupt, this check makes sure that the output is
     still valid, albeit the compression ratio would be bad.

     The compressor populates the hash table from the ring buffer as it's
     reading new bytes from the input. However, at the last few indexes of
     the ring buffer, there are not enough bytes to build full-length
     substrings from. Since the hash table always contains full-length
     substrings, we erase with dummy zeros here to make sure that those
     substrings will contain zeros at the end instead of uninitialized
     data.

     Please note that erasing is not necessary (because the
     memory region is already initialized since he ring buffer
     has a `tail' that holds a copy of the beginning,) so we
     skip erasing if we have already gone around at least once in
     the ring buffer.

     Only clear during the first round of ring-buffer writes. On
     subsequent rounds data in the ring-buffer would be affected. */
  if (ringbuffer_->pos_ <= ringbuffer_->mask_) {
    /* This is the first time when the ring buffer is being written.
       We clear 7 bytes just after the bytes that have been copied from
       the input buffer.

       The ring-buffer has a "tail" that holds a copy of the beginning,
       but only once the ring buffer has been fully written once, i.e.,
       pos <= mask. For the first time, we need to write values
       in this tail (where index may be larger than mask), so that
       we have exactly defined behavior and don't read uninitialized
       memory. Due to performance reasons, hashing reads data using a
       LOAD64, which can go 7 bytes beyond the bytes written in the
       ring-buffer. */
    memset(ringbuffer_->buffer_ + ringbuffer_->pos_, 0, 7);
  }
}

/* Marks all input as processed.
   Returns true if position wrapping occurs. */
static BROTLI_BOOL UpdateLastProcessedPos(BrotliEncoderState* s) {
  uint32_t wrapped_last_processed_pos = WrapPosition(s->last_processed_pos_);
  uint32_t wrapped_input_pos = WrapPosition(s->input_pos_);
  s->last_processed_pos_ = s->input_pos_;
  return TO_BROTLI_BOOL(wrapped_input_pos < wrapped_last_processed_pos);
}

static void ExtendLastCommand(BrotliEncoderState* s, uint32_t* bytes,
                              uint32_t* wrapped_last_processed_pos) {
  Command* last_command = &s->commands_[s->num_commands_ - 1];
  const uint8_t* data = s->ringbuffer_.buffer_;
  const uint32_t mask = s->ringbuffer_.mask_;
  uint64_t max_backward_distance =
      (((uint64_t)1) << s->params.lgwin) - BROTLI_WINDOW_GAP;
  uint64_t last_copy_len = last_command->copy_len_ & 0x1FFFFFF;
  uint64_t last_processed_pos = s->last_processed_pos_ - last_copy_len;
  uint64_t max_distance = last_processed_pos < max_backward_distance ?
      last_processed_pos : max_backward_distance;
  uint64_t cmd_dist = (uint64_t)s->dist_cache_[0];
  uint32_t distance_code = CommandRestoreDistanceCode(last_command,
                                                      &s->params.dist);
  if (distance_code < BROTLI_NUM_DISTANCE_SHORT_CODES ||
      distance_code - (BROTLI_NUM_DISTANCE_SHORT_CODES - 1) == cmd_dist) {
    if (cmd_dist <= max_distance) {
      while (*bytes != 0 && data[*wrapped_last_processed_pos & mask] ==
             data[(*wrapped_last_processed_pos - cmd_dist) & mask]) {
        last_command->copy_len_++;
        (*bytes)--;
        (*wrapped_last_processed_pos)++;
      }
    }
    /* The copy length is at most the metablock size, and thus expressible. */
    GetLengthCode(last_command->insert_len_,
                  (size_t)((int)(last_command->copy_len_ & 0x1FFFFFF) +
                           (int)(last_command->copy_len_ >> 25)),
                  TO_BROTLI_BOOL((last_command->dist_prefix_ & 0x3FF) == 0),
                  &last_command->cmd_prefix_);
  }
}

/*
   Processes the accumulated input data and sets |*out_size| to the length of
   the new output meta-block, or to zero if no new output meta-block has been
   created (in this case the processed input data is buffered internally).
   If |*out_size| is positive, |*output| points to the start of the output
   data. If |is_last| or |force_flush| is BROTLI_TRUE, an output meta-block is
   always created. However, until |is_last| is BROTLI_TRUE encoder may retain up
   to 7 bits of the last byte of output. To force encoder to dump the remaining
   bits use WriteMetadata() to append an empty meta-data block.
   Returns BROTLI_FALSE if the size of the input data is larger than
   input_block_size().
 */
static BROTLI_BOOL EncodeData(
    BrotliEncoderState* s, const BROTLI_BOOL is_last,
    const BROTLI_BOOL force_flush, size_t* out_size, uint8_t** output) {
  const uint64_t delta = UnprocessedInputSize(s);
  uint32_t bytes = (uint32_t)delta;
  uint32_t wrapped_last_processed_pos = WrapPosition(s->last_processed_pos_);
  uint8_t* data;
  uint32_t mask;
  MemoryManager* m = &s->memory_manager_;
  ContextType literal_context_mode;

  data = s->ringbuffer_.buffer_;
  mask = s->ringbuffer_.mask_;

  /* Adding more blocks after "last" block is forbidden. */
  if (s->is_last_block_emitted_) return BROTLI_FALSE;
  if (is_last) s->is_last_block_emitted_ = BROTLI_TRUE;

  if (delta > InputBlockSize(s)) {
    return BROTLI_FALSE;
  }
  if (s->params.quality == FAST_TWO_PASS_COMPRESSION_QUALITY &&
      !s->command_buf_) {
    s->command_buf_ =
        BROTLI_ALLOC(m, uint32_t, kCompressFragmentTwoPassBlockSize);
    s->literal_buf_ =
        BROTLI_ALLOC(m, uint8_t, kCompressFragmentTwoPassBlockSize);
    if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
  }

  if (s->params.quality == FAST_ONE_PASS_COMPRESSION_QUALITY ||
      s->params.quality == FAST_TWO_PASS_COMPRESSION_QUALITY) {
    uint8_t* storage;
    size_t storage_ix = s->last_bytes_bits_;
    size_t table_size;
    int* table;

    if (delta == 0 && !is_last) {
      /* We have no new input data and we don't have to finish the stream, so
         nothing to do. */
      *out_size = 0;
      return BROTLI_TRUE;
    }
    storage = GetBrotliStorage(s, 2 * bytes + 503);
    if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
    storage[0] = (uint8_t)s->last_bytes_;
    storage[1] = (uint8_t)(s->last_bytes_ >> 8);
    table = GetHashTable(s, s->params.quality, bytes, &table_size);
    if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
    if (s->params.quality == FAST_ONE_PASS_COMPRESSION_QUALITY) {
      BrotliCompressFragmentFast(
          m, &data[wrapped_last_processed_pos & mask],
          bytes, is_last,
          table, table_size,
          s->cmd_depths_, s->cmd_bits_,
          &s->cmd_code_numbits_, s->cmd_code_,
          &storage_ix, storage);
      if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
    } else {
      BrotliCompressFragmentTwoPass(
          m, &data[wrapped_last_processed_pos & mask],
          bytes, is_last,
          s->command_buf_, s->literal_buf_,
          table, table_size,
          &storage_ix, storage);
      if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
    }
    s->last_bytes_ = (uint16_t)(storage[storage_ix >> 3]);
    s->last_bytes_bits_ = storage_ix & 7u;
    UpdateLastProcessedPos(s);
    *output = &storage[0];
    *out_size = storage_ix >> 3;
    return BROTLI_TRUE;
  }

  {
    /* Theoretical max number of commands is 1 per 2 bytes. */
    size_t newsize = s->num_commands_ + bytes / 2 + 1;
    if (newsize > s->cmd_alloc_size_) {
      Command* new_commands;
      /* Reserve a bit more memory to allow merging with a next block
         without reallocation: that would impact speed. */
      newsize += (bytes / 4) + 16;
      s->cmd_alloc_size_ = newsize;
      new_commands = BROTLI_ALLOC(m, Command, newsize);
      if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
      if (s->commands_) {
        memcpy(new_commands, s->commands_, sizeof(Command) * s->num_commands_);
        BROTLI_FREE(m, s->commands_);
      }
      s->commands_ = new_commands;
    }
  }

  InitOrStitchToPreviousBlock(m, &s->hasher_, data, mask, &s->params,
      wrapped_last_processed_pos, bytes, is_last);

  literal_context_mode = ChooseContextMode(
      &s->params, data, WrapPosition(s->last_flush_pos_),
      mask, (size_t)(s->input_pos_ - s->last_flush_pos_));

  if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;

  if (s->num_commands_ && s->last_insert_len_ == 0) {
    ExtendLastCommand(s, &bytes, &wrapped_last_processed_pos);
  }

  if (s->params.quality == ZOPFLIFICATION_QUALITY) {
    BROTLI_DCHECK(s->params.hasher.type == 10);
    BrotliCreateZopfliBackwardReferences(m, bytes, wrapped_last_processed_pos,
        data, mask, &s->params, s->hasher_, s->dist_cache_,
        &s->last_insert_len_, &s->commands_[s->num_commands_],
        &s->num_commands_, &s->num_literals_);
    if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
  } else if (s->params.quality == HQ_ZOPFLIFICATION_QUALITY) {
    BROTLI_DCHECK(s->params.hasher.type == 10);
    BrotliCreateHqZopfliBackwardReferences(m, bytes, wrapped_last_processed_pos,
        data, mask, &s->params, s->hasher_, s->dist_cache_,
        &s->last_insert_len_, &s->commands_[s->num_commands_],
        &s->num_commands_, &s->num_literals_);
    if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
  } else {
    BrotliCreateBackwardReferences(bytes, wrapped_last_processed_pos,
        data, mask, &s->params, s->hasher_, s->dist_cache_,
        &s->last_insert_len_, &s->commands_[s->num_commands_],
        &s->num_commands_, &s->num_literals_);
  }

  {
    const size_t max_length = MaxMetablockSize(&s->params);
    const size_t max_literals = max_length / 8;
    const size_t max_commands = max_length / 8;
    const size_t processed_bytes = (size_t)(s->input_pos_ - s->last_flush_pos_);
    /* If maximal possible additional block doesn't fit metablock, flush now. */
    /* TODO: Postpone decision until next block arrives? */
    const BROTLI_BOOL next_input_fits_metablock = TO_BROTLI_BOOL(
        processed_bytes + InputBlockSize(s) <= max_length);
    /* If block splitting is not used, then flush as soon as there is some
       amount of commands / literals produced. */
    const BROTLI_BOOL should_flush = TO_BROTLI_BOOL(
        s->params.quality < MIN_QUALITY_FOR_BLOCK_SPLIT &&
        s->num_literals_ + s->num_commands_ >= MAX_NUM_DELAYED_SYMBOLS);
    if (!is_last && !force_flush && !should_flush &&
        next_input_fits_metablock &&
        s->num_literals_ < max_literals &&
        s->num_commands_ < max_commands) {
      /* Merge with next input block. Everything will happen later. */
      if (UpdateLastProcessedPos(s)) {
        HasherReset(s->hasher_);
      }
      *out_size = 0;
      return BROTLI_TRUE;
    }
  }

  /* Create the last insert-only command. */
  if (s->last_insert_len_ > 0) {
    InitInsertCommand(&s->commands_[s->num_commands_++], s->last_insert_len_);
    s->num_literals_ += s->last_insert_len_;
    s->last_insert_len_ = 0;
  }

  if (!is_last && s->input_pos_ == s->last_flush_pos_) {
    /* We have no new input data and we don't have to finish the stream, so
       nothing to do. */
    *out_size = 0;
    return BROTLI_TRUE;
  }
  BROTLI_DCHECK(s->input_pos_ >= s->last_flush_pos_);
  BROTLI_DCHECK(s->input_pos_ > s->last_flush_pos_ || is_last);
  BROTLI_DCHECK(s->input_pos_ - s->last_flush_pos_ <= 1u << 24);
  {
    const uint32_t metablock_size =
        (uint32_t)(s->input_pos_ - s->last_flush_pos_);
    uint8_t* storage = GetBrotliStorage(s, 2 * metablock_size + 503);
    size_t storage_ix = s->last_bytes_bits_;
    if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
    storage[0] = (uint8_t)s->last_bytes_;
    storage[1] = (uint8_t)(s->last_bytes_ >> 8);
    WriteMetaBlockInternal(
        m, data, mask, s->last_flush_pos_, metablock_size, is_last,
        literal_context_mode, &s->params, s->prev_byte_, s->prev_byte2_,
        s->num_literals_, s->num_commands_, s->commands_, s->saved_dist_cache_,
        s->dist_cache_, &storage_ix, storage);
    if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
    s->last_bytes_ = (uint16_t)(storage[storage_ix >> 3]);
    s->last_bytes_bits_ = storage_ix & 7u;
    s->last_flush_pos_ = s->input_pos_;
    if (UpdateLastProcessedPos(s)) {
      HasherReset(s->hasher_);
    }
    if (s->last_flush_pos_ > 0) {
      s->prev_byte_ = data[((uint32_t)s->last_flush_pos_ - 1) & mask];
    }
    if (s->last_flush_pos_ > 1) {
      s->prev_byte2_ = data[(uint32_t)(s->last_flush_pos_ - 2) & mask];
    }
    s->num_commands_ = 0;
    s->num_literals_ = 0;
    /* Save the state of the distance cache in case we need to restore it for
       emitting an uncompressed block. */
    memcpy(s->saved_dist_cache_, s->dist_cache_, sizeof(s->saved_dist_cache_));
    *output = &storage[0];
    *out_size = storage_ix >> 3;
    return BROTLI_TRUE;
  }
}

/* Dumps remaining output bits and metadata header to |header|.
   Returns number of produced bytes.
   REQUIRED: |header| should be 8-byte aligned and at least 16 bytes long.
   REQUIRED: |block_size| <= (1 << 24). */
static size_t WriteMetadataHeader(
    BrotliEncoderState* s, const size_t block_size, uint8_t* header) {
  size_t storage_ix;
  storage_ix = s->last_bytes_bits_;
  header[0] = (uint8_t)s->last_bytes_;
  header[1] = (uint8_t)(s->last_bytes_ >> 8);
  s->last_bytes_ = 0;
  s->last_bytes_bits_ = 0;

  BrotliWriteBits(1, 0, &storage_ix, header);
  BrotliWriteBits(2, 3, &storage_ix, header);
  BrotliWriteBits(1, 0, &storage_ix, header);
  if (block_size == 0) {
    BrotliWriteBits(2, 0, &storage_ix, header);
  } else {
    uint32_t nbits = (block_size == 1) ? 0 :
        (Log2FloorNonZero((uint32_t)block_size - 1) + 1);
    uint32_t nbytes = (nbits + 7) / 8;
    BrotliWriteBits(2, nbytes, &storage_ix, header);
    BrotliWriteBits(8 * nbytes, block_size - 1, &storage_ix, header);
  }
  return (storage_ix + 7u) >> 3;
}

static BROTLI_BOOL BrotliCompressBufferQuality10(
    int lgwin, size_t input_size, const uint8_t* input_buffer,
    size_t* encoded_size, uint8_t* encoded_buffer) {
  MemoryManager memory_manager;
  MemoryManager* m = &memory_manager;

  const size_t mask = BROTLI_SIZE_MAX >> 1;
  int dist_cache[4] = { 4, 11, 15, 16 };
  int saved_dist_cache[4] = { 4, 11, 15, 16 };
  BROTLI_BOOL ok = BROTLI_TRUE;
  const size_t max_out_size = *encoded_size;
  size_t total_out_size = 0;
  uint16_t last_bytes;
  uint8_t last_bytes_bits;
  HasherHandle hasher = NULL;

  const size_t hasher_eff_size = BROTLI_MIN(size_t,
      input_size, BROTLI_MAX_BACKWARD_LIMIT(lgwin) + BROTLI_WINDOW_GAP);

  BrotliEncoderParams params;

  const int lgmetablock = BROTLI_MIN(int, 24, lgwin + 1);
  size_t max_block_size;
  const size_t max_metablock_size = (size_t)1 << lgmetablock;
  const size_t max_literals_per_metablock = max_metablock_size / 8;
  const size_t max_commands_per_metablock = max_metablock_size / 8;
  size_t metablock_start = 0;
  uint8_t prev_byte = 0;
  uint8_t prev_byte2 = 0;

  BrotliEncoderInitParams(&params);
  params.quality = 10;
  params.lgwin = lgwin;
  if (lgwin > BROTLI_MAX_WINDOW_BITS) {
    params.large_window = BROTLI_TRUE;
  }
  SanitizeParams(&params);
  params.lgblock = ComputeLgBlock(&params);
  ChooseDistanceParams(&params);
  max_block_size = (size_t)1 << params.lgblock;

  BrotliInitMemoryManager(m, 0, 0, 0);

  BROTLI_DCHECK(input_size <= mask + 1);
  EncodeWindowBits(lgwin, params.large_window, &last_bytes, &last_bytes_bits);
  InitOrStitchToPreviousBlock(m, &hasher, input_buffer, mask, &params,
      0, hasher_eff_size, BROTLI_TRUE);
  if (BROTLI_IS_OOM(m)) goto oom;

  while (ok && metablock_start < input_size) {
    const size_t metablock_end =
        BROTLI_MIN(size_t, input_size, metablock_start + max_metablock_size);
    const size_t expected_num_commands =
        (metablock_end - metablock_start) / 12 + 16;
    Command* commands = 0;
    size_t num_commands = 0;
    size_t last_insert_len = 0;
    size_t num_literals = 0;
    size_t metablock_size = 0;
    size_t cmd_alloc_size = 0;
    BROTLI_BOOL is_last;
    uint8_t* storage;
    size_t storage_ix;

    ContextType literal_context_mode = ChooseContextMode(&params,
        input_buffer, metablock_start, mask, metablock_end - metablock_start);

    size_t block_start;
    for (block_start = metablock_start; block_start < metablock_end; ) {
      size_t block_size =
          BROTLI_MIN(size_t, metablock_end - block_start, max_block_size);
      ZopfliNode* nodes = BROTLI_ALLOC(m, ZopfliNode, block_size + 1);
      size_t path_size;
      size_t new_cmd_alloc_size;
      if (BROTLI_IS_OOM(m)) goto oom;
      BrotliInitZopfliNodes(nodes, block_size + 1);
      StitchToPreviousBlockH10(hasher, block_size, block_start,
                               input_buffer, mask);
      path_size = BrotliZopfliComputeShortestPath(m, block_size, block_start,
          input_buffer, mask, &params, dist_cache, hasher,
          nodes);
      if (BROTLI_IS_OOM(m)) goto oom;
      /* We allocate a command buffer in the first iteration of this loop that
         will be likely big enough for the whole metablock, so that for most
         inputs we will not have to reallocate in later iterations. We do the
         allocation here and not before the loop, because if the input is small,
         this will be allocated after the Zopfli cost model is freed, so this
         will not increase peak memory usage.
         TODO: If the first allocation is too small, increase command
         buffer size exponentially. */
      new_cmd_alloc_size = BROTLI_MAX(size_t, expected_num_commands,
                                      num_commands + path_size + 1);
      if (cmd_alloc_size != new_cmd_alloc_size) {
        Command* new_commands = BROTLI_ALLOC(m, Command, new_cmd_alloc_size);
        if (BROTLI_IS_OOM(m)) goto oom;
        cmd_alloc_size = new_cmd_alloc_size;
        if (commands) {
          memcpy(new_commands, commands, sizeof(Command) * num_commands);
          BROTLI_FREE(m, commands);
        }
        commands = new_commands;
      }
      BrotliZopfliCreateCommands(block_size, block_start, &nodes[0], dist_cache,
          &last_insert_len, &params, &commands[num_commands], &num_literals);
      num_commands += path_size;
      block_start += block_size;
      metablock_size += block_size;
      BROTLI_FREE(m, nodes);
      if (num_literals > max_literals_per_metablock ||
          num_commands > max_commands_per_metablock) {
        break;
      }
    }

    if (last_insert_len > 0) {
      InitInsertCommand(&commands[num_commands++], last_insert_len);
      num_literals += last_insert_len;
    }

    is_last = TO_BROTLI_BOOL(metablock_start + metablock_size == input_size);
    storage = NULL;
    storage_ix = last_bytes_bits;

    if (metablock_size == 0) {
      /* Write the ISLAST and ISEMPTY bits. */
      storage = BROTLI_ALLOC(m, uint8_t, 16);
      if (BROTLI_IS_OOM(m)) goto oom;
      storage[0] = (uint8_t)last_bytes;
      storage[1] = (uint8_t)(last_bytes >> 8);
      BrotliWriteBits(2, 3, &storage_ix, storage);
      storage_ix = (storage_ix + 7u) & ~7u;
    } else if (!ShouldCompress(input_buffer, mask, metablock_start,
                               metablock_size, num_literals, num_commands)) {
      /* Restore the distance cache, as its last update by
         CreateBackwardReferences is now unused. */
      memcpy(dist_cache, saved_dist_cache, 4 * sizeof(dist_cache[0]));
      storage = BROTLI_ALLOC(m, uint8_t, metablock_size + 16);
      if (BROTLI_IS_OOM(m)) goto oom;
      storage[0] = (uint8_t)last_bytes;
      storage[1] = (uint8_t)(last_bytes >> 8);
      BrotliStoreUncompressedMetaBlock(is_last, input_buffer,
                                       metablock_start, mask, metablock_size,
                                       &storage_ix, storage);
    } else {
      MetaBlockSplit mb;
      BrotliEncoderParams block_params = params;
      InitMetaBlockSplit(&mb);
      BrotliBuildMetaBlock(m, input_buffer, metablock_start, mask,
                           &block_params,
                           prev_byte, prev_byte2,
                           commands, num_commands,
                           literal_context_mode,
                           &mb);
      if (BROTLI_IS_OOM(m)) goto oom;
      {
        /* The number of distance symbols effectively used for distance
           histograms. It might be less than distance alphabet size
           for "Large Window Brotli" (32-bit). */
        uint32_t num_effective_dist_codes = block_params.dist.alphabet_size;
        if (num_effective_dist_codes > BROTLI_NUM_HISTOGRAM_DISTANCE_SYMBOLS) {
          num_effective_dist_codes = BROTLI_NUM_HISTOGRAM_DISTANCE_SYMBOLS;
        }
        BrotliOptimizeHistograms(num_effective_dist_codes, &mb);
      }
      storage = BROTLI_ALLOC(m, uint8_t, 2 * metablock_size + 503);
      if (BROTLI_IS_OOM(m)) goto oom;
      storage[0] = (uint8_t)last_bytes;
      storage[1] = (uint8_t)(last_bytes >> 8);
      BrotliStoreMetaBlock(m, input_buffer, metablock_start, metablock_size,
                           mask, prev_byte, prev_byte2,
                           is_last,
                           &block_params,
                           literal_context_mode,
                           commands, num_commands,
                           &mb,
                           &storage_ix, storage);
      if (BROTLI_IS_OOM(m)) goto oom;
      if (metablock_size + 4 < (storage_ix >> 3)) {
        /* Restore the distance cache and last byte. */
        memcpy(dist_cache, saved_dist_cache, 4 * sizeof(dist_cache[0]));
        storage[0] = (uint8_t)last_bytes;
        storage[1] = (uint8_t)(last_bytes >> 8);
        storage_ix = last_bytes_bits;
        BrotliStoreUncompressedMetaBlock(is_last, input_buffer,
                                         metablock_start, mask,
                                         metablock_size, &storage_ix, storage);
      }
      DestroyMetaBlockSplit(m, &mb);
    }
    last_bytes = (uint16_t)(storage[storage_ix >> 3]);
    last_bytes_bits = storage_ix & 7u;
    metablock_start += metablock_size;
    if (metablock_start < input_size) {
      prev_byte = input_buffer[metablock_start - 1];
      prev_byte2 = input_buffer[metablock_start - 2];
    }
    /* Save the state of the distance cache in case we need to restore it for
       emitting an uncompressed block. */
    memcpy(saved_dist_cache, dist_cache, 4 * sizeof(dist_cache[0]));

    {
      const size_t out_size = storage_ix >> 3;
      total_out_size += out_size;
      if (total_out_size <= max_out_size) {
        memcpy(encoded_buffer, storage, out_size);
        encoded_buffer += out_size;
      } else {
        ok = BROTLI_FALSE;
      }
    }
    BROTLI_FREE(m, storage);
    BROTLI_FREE(m, commands);
  }

  *encoded_size = total_out_size;
  DestroyHasher(m, &hasher);
  return ok;

oom:
  BrotliWipeOutMemoryManager(m);
  return BROTLI_FALSE;
}

size_t BrotliEncoderMaxCompressedSize(size_t input_size) {
  /* [window bits / empty metadata] + N * [uncompressed] + [last empty] */
  size_t num_large_blocks = input_size >> 14;
  size_t overhead = 2 + (4 * num_large_blocks) + 3 + 1;
  size_t result = input_size + overhead;
  if (input_size == 0) return 2;
  return (result < input_size) ? 0 : result;
}

/* Wraps data to uncompressed brotli stream with minimal window size.
   |output| should point at region with at least BrotliEncoderMaxCompressedSize
   addressable bytes.
   Returns the length of stream. */
static size_t MakeUncompressedStream(
    const uint8_t* input, size_t input_size, uint8_t* output) {
  size_t size = input_size;
  size_t result = 0;
  size_t offset = 0;
  if (input_size == 0) {
    output[0] = 6;
    return 1;
  }
  output[result++] = 0x21;  /* window bits = 10, is_last = false */
  output[result++] = 0x03;  /* empty metadata, padding */
  while (size > 0) {
    uint32_t nibbles = 0;
    uint32_t chunk_size;
    uint32_t bits;
    chunk_size = (size > (1u << 24)) ? (1u << 24) : (uint32_t)size;
    if (chunk_size > (1u << 16)) nibbles = (chunk_size > (1u << 20)) ? 2 : 1;
    bits =
        (nibbles << 1) | ((chunk_size - 1) << 3) | (1u << (19 + 4 * nibbles));
    output[result++] = (uint8_t)bits;
    output[result++] = (uint8_t)(bits >> 8);
    output[result++] = (uint8_t)(bits >> 16);
    if (nibbles == 2) output[result++] = (uint8_t)(bits >> 24);
    memcpy(&output[result], &input[offset], chunk_size);
    result += chunk_size;
    offset += chunk_size;
    size -= chunk_size;
  }
  output[result++] = 3;
  return result;
}

BROTLI_BOOL BrotliEncoderCompress(
    int quality, int lgwin, BrotliEncoderMode mode, size_t input_size,
    const uint8_t* input_buffer, size_t* encoded_size,
    uint8_t* encoded_buffer) {
  BrotliEncoderState* s;
  size_t out_size = *encoded_size;
  const uint8_t* input_start = input_buffer;
  uint8_t* output_start = encoded_buffer;
  size_t max_out_size = BrotliEncoderMaxCompressedSize(input_size);
  if (out_size == 0) {
    /* Output buffer needs at least one byte. */
    return BROTLI_FALSE;
  }
  if (input_size == 0) {
    /* Handle the special case of empty input. */
    *encoded_size = 1;
    *encoded_buffer = 6;
    return BROTLI_TRUE;
  }
  if (quality == 10) {
    /* TODO: Implement this direct path for all quality levels. */
    const int lg_win = BROTLI_MIN(int, BROTLI_LARGE_MAX_WINDOW_BITS,
                                       BROTLI_MAX(int, 16, lgwin));
    int ok = BrotliCompressBufferQuality10(lg_win, input_size, input_buffer,
                                           encoded_size, encoded_buffer);
    if (!ok || (max_out_size && *encoded_size > max_out_size)) {
      goto fallback;
    }
    return BROTLI_TRUE;
  }

  s = BrotliEncoderCreateInstance(0, 0, 0);
  if (!s) {
    return BROTLI_FALSE;
  } else {
    size_t available_in = input_size;
    const uint8_t* next_in = input_buffer;
    size_t available_out = *encoded_size;
    uint8_t* next_out = encoded_buffer;
    size_t total_out = 0;
    BROTLI_BOOL result = BROTLI_FALSE;
    BrotliEncoderSetParameter(s, BROTLI_PARAM_QUALITY, (uint32_t)quality);
    BrotliEncoderSetParameter(s, BROTLI_PARAM_LGWIN, (uint32_t)lgwin);
    BrotliEncoderSetParameter(s, BROTLI_PARAM_MODE, (uint32_t)mode);
    BrotliEncoderSetParameter(s, BROTLI_PARAM_SIZE_HINT, (uint32_t)input_size);
    if (lgwin > BROTLI_MAX_WINDOW_BITS) {
      BrotliEncoderSetParameter(s, BROTLI_PARAM_LARGE_WINDOW, BROTLI_TRUE);
    }
    result = BrotliEncoderCompressStream(s, BROTLI_OPERATION_FINISH,
        &available_in, &next_in, &available_out, &next_out, &total_out);
    if (!BrotliEncoderIsFinished(s)) result = 0;
    *encoded_size = total_out;
    BrotliEncoderDestroyInstance(s);
    if (!result || (max_out_size && *encoded_size > max_out_size)) {
      goto fallback;
    }
    return BROTLI_TRUE;
  }
fallback:
  *encoded_size = 0;
  if (!max_out_size) return BROTLI_FALSE;
  if (out_size >= max_out_size) {
    *encoded_size =
        MakeUncompressedStream(input_start, input_size, output_start);
    return BROTLI_TRUE;
  }
  return BROTLI_FALSE;
}

static void InjectBytePaddingBlock(BrotliEncoderState* s) {
  uint32_t seal = s->last_bytes_;
  size_t seal_bits = s->last_bytes_bits_;
  uint8_t* destination;
  s->last_bytes_ = 0;
  s->last_bytes_bits_ = 0;
  /* is_last = 0, data_nibbles = 11, reserved = 0, meta_nibbles = 00 */
  seal |= 0x6u << seal_bits;
  seal_bits += 6;
  /* If we have already created storage, then append to it.
     Storage is valid until next block is being compressed. */
  if (s->next_out_) {
    destination = s->next_out_ + s->available_out_;
  } else {
    destination = s->tiny_buf_.u8;
    s->next_out_ = destination;
  }
  destination[0] = (uint8_t)seal;
  if (seal_bits > 8) destination[1] = (uint8_t)(seal >> 8);
  if (seal_bits > 16) destination[2] = (uint8_t)(seal >> 16);
  s->available_out_ += (seal_bits + 7) >> 3;
}

/* Injects padding bits or pushes compressed data to output.
   Returns false if nothing is done. */
static BROTLI_BOOL InjectFlushOrPushOutput(BrotliEncoderState* s,
    size_t* available_out, uint8_t** next_out, size_t* total_out) {
  if (s->stream_state_ == BROTLI_STREAM_FLUSH_REQUESTED &&
      s->last_bytes_bits_ != 0) {
    InjectBytePaddingBlock(s);
    return BROTLI_TRUE;
  }

  if (s->available_out_ != 0 && *available_out != 0) {
    size_t copy_output_size =
        BROTLI_MIN(size_t, s->available_out_, *available_out);
    memcpy(*next_out, s->next_out_, copy_output_size);
    *next_out += copy_output_size;
    *available_out -= copy_output_size;
    s->next_out_ += copy_output_size;
    s->available_out_ -= copy_output_size;
    s->total_out_ += copy_output_size;
    if (total_out) *total_out = s->total_out_;
    return BROTLI_TRUE;
  }

  return BROTLI_FALSE;
}

static void CheckFlushComplete(BrotliEncoderState* s) {
  if (s->stream_state_ == BROTLI_STREAM_FLUSH_REQUESTED &&
      s->available_out_ == 0) {
    s->stream_state_ = BROTLI_STREAM_PROCESSING;
    s->next_out_ = 0;
  }
}

static BROTLI_BOOL BrotliEncoderCompressStreamFast(
    BrotliEncoderState* s, BrotliEncoderOperation op, size_t* available_in,
    const uint8_t** next_in, size_t* available_out, uint8_t** next_out,
    size_t* total_out) {
  const size_t block_size_limit = (size_t)1 << s->params.lgwin;
  const size_t buf_size = BROTLI_MIN(size_t, kCompressFragmentTwoPassBlockSize,
      BROTLI_MIN(size_t, *available_in, block_size_limit));
  uint32_t* tmp_command_buf = NULL;
  uint32_t* command_buf = NULL;
  uint8_t* tmp_literal_buf = NULL;
  uint8_t* literal_buf = NULL;
  MemoryManager* m = &s->memory_manager_;
  if (s->params.quality != FAST_ONE_PASS_COMPRESSION_QUALITY &&
      s->params.quality != FAST_TWO_PASS_COMPRESSION_QUALITY) {
    return BROTLI_FALSE;
  }
  if (s->params.quality == FAST_TWO_PASS_COMPRESSION_QUALITY) {
    if (!s->command_buf_ && buf_size == kCompressFragmentTwoPassBlockSize) {
      s->command_buf_ =
          BROTLI_ALLOC(m, uint32_t, kCompressFragmentTwoPassBlockSize);
      s->literal_buf_ =
          BROTLI_ALLOC(m, uint8_t, kCompressFragmentTwoPassBlockSize);
      if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
    }
    if (s->command_buf_) {
      command_buf = s->command_buf_;
      literal_buf = s->literal_buf_;
    } else {
      tmp_command_buf = BROTLI_ALLOC(m, uint32_t, buf_size);
      tmp_literal_buf = BROTLI_ALLOC(m, uint8_t, buf_size);
      if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
      command_buf = tmp_command_buf;
      literal_buf = tmp_literal_buf;
    }
  }

  while (BROTLI_TRUE) {
    if (InjectFlushOrPushOutput(s, available_out, next_out, total_out)) {
      continue;
    }

    /* Compress block only when internal output buffer is empty, stream is not
       finished, there is no pending flush request, and there is either
       additional input or pending operation. */
    if (s->available_out_ == 0 &&
        s->stream_state_ == BROTLI_STREAM_PROCESSING &&
        (*available_in != 0 || op != BROTLI_OPERATION_PROCESS)) {
      size_t block_size = BROTLI_MIN(size_t, block_size_limit, *available_in);
      BROTLI_BOOL is_last =
          (*available_in == block_size) && (op == BROTLI_OPERATION_FINISH);
      BROTLI_BOOL force_flush =
          (*available_in == block_size) && (op == BROTLI_OPERATION_FLUSH);
      size_t max_out_size = 2 * block_size + 503;
      BROTLI_BOOL inplace = BROTLI_TRUE;
      uint8_t* storage = NULL;
      size_t storage_ix = s->last_bytes_bits_;
      size_t table_size;
      int* table;

      if (force_flush && block_size == 0) {
        s->stream_state_ = BROTLI_STREAM_FLUSH_REQUESTED;
        continue;
      }
      if (max_out_size <= *available_out) {
        storage = *next_out;
      } else {
        inplace = BROTLI_FALSE;
        storage = GetBrotliStorage(s, max_out_size);
        if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
      }
      storage[0] = (uint8_t)s->last_bytes_;
      storage[1] = (uint8_t)(s->last_bytes_ >> 8);
      table = GetHashTable(s, s->params.quality, block_size, &table_size);
      if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;

      if (s->params.quality == FAST_ONE_PASS_COMPRESSION_QUALITY) {
        BrotliCompressFragmentFast(m, *next_in, block_size, is_last, table,
            table_size, s->cmd_depths_, s->cmd_bits_, &s->cmd_code_numbits_,
            s->cmd_code_, &storage_ix, storage);
        if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
      } else {
        BrotliCompressFragmentTwoPass(m, *next_in, block_size, is_last,
            command_buf, literal_buf, table, table_size,
            &storage_ix, storage);
        if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
      }
      *next_in += block_size;
      *available_in -= block_size;
      if (inplace) {
        size_t out_bytes = storage_ix >> 3;
        BROTLI_DCHECK(out_bytes <= *available_out);
        BROTLI_DCHECK((storage_ix & 7) == 0 || out_bytes < *available_out);
        *next_out += out_bytes;
        *available_out -= out_bytes;
        s->total_out_ += out_bytes;
        if (total_out) *total_out = s->total_out_;
      } else {
        size_t out_bytes = storage_ix >> 3;
        s->next_out_ = storage;
        s->available_out_ = out_bytes;
      }
      s->last_bytes_ = (uint16_t)(storage[storage_ix >> 3]);
      s->last_bytes_bits_ = storage_ix & 7u;

      if (force_flush) s->stream_state_ = BROTLI_STREAM_FLUSH_REQUESTED;
      if (is_last) s->stream_state_ = BROTLI_STREAM_FINISHED;
      continue;
    }
    break;
  }
  BROTLI_FREE(m, tmp_command_buf);
  BROTLI_FREE(m, tmp_literal_buf);
  CheckFlushComplete(s);
  return BROTLI_TRUE;
}

static BROTLI_BOOL ProcessMetadata(
    BrotliEncoderState* s, size_t* available_in, const uint8_t** next_in,
    size_t* available_out, uint8_t** next_out, size_t* total_out) {
  if (*available_in > (1u << 24)) return BROTLI_FALSE;
  /* Switch to metadata block workflow, if required. */
  if (s->stream_state_ == BROTLI_STREAM_PROCESSING) {
    s->remaining_metadata_bytes_ = (uint32_t)*available_in;
    s->stream_state_ = BROTLI_STREAM_METADATA_HEAD;
  }
  if (s->stream_state_ != BROTLI_STREAM_METADATA_HEAD &&
      s->stream_state_ != BROTLI_STREAM_METADATA_BODY) {
    return BROTLI_FALSE;
  }

  while (BROTLI_TRUE) {
    if (InjectFlushOrPushOutput(s, available_out, next_out, total_out)) {
      continue;
    }
    if (s->available_out_ != 0) break;

    if (s->input_pos_ != s->last_flush_pos_) {
      BROTLI_BOOL result = EncodeData(s, BROTLI_FALSE, BROTLI_TRUE,
          &s->available_out_, &s->next_out_);
      if (!result) return BROTLI_FALSE;
      continue;
    }

    if (s->stream_state_ == BROTLI_STREAM_METADATA_HEAD) {
      s->next_out_ = s->tiny_buf_.u8;
      s->available_out_ =
          WriteMetadataHeader(s, s->remaining_metadata_bytes_, s->next_out_);
      s->stream_state_ = BROTLI_STREAM_METADATA_BODY;
      continue;
    } else {
      /* Exit workflow only when there is no more input and no more output.
         Otherwise client may continue producing empty metadata blocks. */
      if (s->remaining_metadata_bytes_ == 0) {
        s->remaining_metadata_bytes_ = BROTLI_UINT32_MAX;
        s->stream_state_ = BROTLI_STREAM_PROCESSING;
        break;
      }
      if (*available_out) {
        /* Directly copy input to output. */
        uint32_t copy = (uint32_t)BROTLI_MIN(
            size_t, s->remaining_metadata_bytes_, *available_out);
        memcpy(*next_out, *next_in, copy);
        *next_in += copy;
        *available_in -= copy;
        s->remaining_metadata_bytes_ -= copy;
        *next_out += copy;
        *available_out -= copy;
      } else {
        /* This guarantees progress in "TakeOutput" workflow. */
        uint32_t copy = BROTLI_MIN(uint32_t, s->remaining_metadata_bytes_, 16);
        s->next_out_ = s->tiny_buf_.u8;
        memcpy(s->next_out_, *next_in, copy);
        *next_in += copy;
        *available_in -= copy;
        s->remaining_metadata_bytes_ -= copy;
        s->available_out_ = copy;
      }
      continue;
    }
  }

  return BROTLI_TRUE;
}

static void UpdateSizeHint(BrotliEncoderState* s, size_t available_in) {
  if (s->params.size_hint == 0) {
    uint64_t delta = UnprocessedInputSize(s);
    uint64_t tail = available_in;
    uint32_t limit = 1u << 30;
    uint32_t total;
    if ((delta >= limit) || (tail >= limit) || ((delta + tail) >= limit)) {
      total = limit;
    } else {
      total = (uint32_t)(delta + tail);
    }
    s->params.size_hint = total;
  }
}

BROTLI_BOOL BrotliEncoderCompressStream(
    BrotliEncoderState* s, BrotliEncoderOperation op, size_t* available_in,
    const uint8_t** next_in, size_t* available_out,uint8_t** next_out,
    size_t* total_out) {
  if (!EnsureInitialized(s)) return BROTLI_FALSE;

  /* Unfinished metadata block; check requirements. */
  if (s->remaining_metadata_bytes_ != BROTLI_UINT32_MAX) {
    if (*available_in != s->remaining_metadata_bytes_) return BROTLI_FALSE;
    if (op != BROTLI_OPERATION_EMIT_METADATA) return BROTLI_FALSE;
  }

  if (op == BROTLI_OPERATION_EMIT_METADATA) {
    UpdateSizeHint(s, 0);  /* First data metablock might be emitted here. */
    return ProcessMetadata(
        s, available_in, next_in, available_out, next_out, total_out);
  }

  if (s->stream_state_ == BROTLI_STREAM_METADATA_HEAD ||
      s->stream_state_ == BROTLI_STREAM_METADATA_BODY) {
    return BROTLI_FALSE;
  }

  if (s->stream_state_ != BROTLI_STREAM_PROCESSING && *available_in != 0) {
    return BROTLI_FALSE;
  }
  if (s->params.quality == FAST_ONE_PASS_COMPRESSION_QUALITY ||
      s->params.quality == FAST_TWO_PASS_COMPRESSION_QUALITY) {
    return BrotliEncoderCompressStreamFast(s, op, available_in, next_in,
        available_out, next_out, total_out);
  }
  while (BROTLI_TRUE) {
    size_t remaining_block_size = RemainingInputBlockSize(s);

    if (remaining_block_size != 0 && *available_in != 0) {
      size_t copy_input_size =
          BROTLI_MIN(size_t, remaining_block_size, *available_in);
      CopyInputToRingBuffer(s, copy_input_size, *next_in);
      *next_in += copy_input_size;
      *available_in -= copy_input_size;
      continue;
    }

    if (InjectFlushOrPushOutput(s, available_out, next_out, total_out)) {
      continue;
    }

    /* Compress data only when internal output buffer is empty, stream is not
       finished and there is no pending flush request. */
    if (s->available_out_ == 0 &&
        s->stream_state_ == BROTLI_STREAM_PROCESSING) {
      if (remaining_block_size == 0 || op != BROTLI_OPERATION_PROCESS) {
        BROTLI_BOOL is_last = TO_BROTLI_BOOL(
            (*available_in == 0) && op == BROTLI_OPERATION_FINISH);
        BROTLI_BOOL force_flush = TO_BROTLI_BOOL(
            (*available_in == 0) && op == BROTLI_OPERATION_FLUSH);
        BROTLI_BOOL result;
        UpdateSizeHint(s, *available_in);
        result = EncodeData(s, is_last, force_flush,
            &s->available_out_, &s->next_out_);
        if (!result) return BROTLI_FALSE;
        if (force_flush) s->stream_state_ = BROTLI_STREAM_FLUSH_REQUESTED;
        if (is_last) s->stream_state_ = BROTLI_STREAM_FINISHED;
        continue;
      }
    }
    break;
  }
  CheckFlushComplete(s);
  return BROTLI_TRUE;
}

BROTLI_BOOL BrotliEncoderIsFinished(BrotliEncoderState* s) {
  return TO_BROTLI_BOOL(s->stream_state_ == BROTLI_STREAM_FINISHED &&
      !BrotliEncoderHasMoreOutput(s));
}

BROTLI_BOOL BrotliEncoderHasMoreOutput(BrotliEncoderState* s) {
  return TO_BROTLI_BOOL(s->available_out_ != 0);
}

const uint8_t* BrotliEncoderTakeOutput(BrotliEncoderState* s, size_t* size) {
  size_t consumed_size = s->available_out_;
  uint8_t* result = s->next_out_;
  if (*size) {
    consumed_size = BROTLI_MIN(size_t, *size, s->available_out_);
  }
  if (consumed_size) {
    s->next_out_ += consumed_size;
    s->available_out_ -= consumed_size;
    s->total_out_ += consumed_size;
    CheckFlushComplete(s);
    *size = consumed_size;
  } else {
    *size = 0;
    result = 0;
  }
  return result;
}

uint32_t BrotliEncoderVersion(void) {
  return BROTLI_VERSION;
}

#if defined(__cplusplus) || defined(c_plusplus)
}  /* extern "C" */
#endif