This repository has been archived by the owner on Jul 25, 2022. It is now read-only.
forked from libjpeg-turbo/libjpeg-turbo
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathjchuff.c
1137 lines (963 loc) · 35.8 KB
/
jchuff.c
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
/*
* jchuff.c
*
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1991-1997, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 2009-2011, 2014-2016, 2018-2022, D. R. Commander.
* Copyright (C) 2015, Matthieu Darbois.
* Copyright (C) 2018, Matthias Räncker.
* Copyright (C) 2020, Arm Limited.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*
* This file contains Huffman entropy encoding routines.
*
* Much of the complexity here has to do with supporting output suspension.
* If the data destination module demands suspension, we want to be able to
* back up to the start of the current MCU. To do this, we copy state
* variables into local working storage, and update them back to the
* permanent JPEG objects only upon successful completion of an MCU.
*
* NOTE: All referenced figures are from
* Recommendation ITU-T T.81 (1992) | ISO/IEC 10918-1:1994.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jsimd.h"
#include "jconfigint.h"
#include <limits.h>
/*
* NOTE: If USE_CLZ_INTRINSIC is defined, then clz/bsr instructions will be
* used for bit counting rather than the lookup table. This will reduce the
* memory footprint by 64k, which is important for some mobile applications
* that create many isolated instances of libjpeg-turbo (web browsers, for
* instance.) This may improve performance on some mobile platforms as well.
* This feature is enabled by default only on Arm processors, because some x86
* chips have a slow implementation of bsr, and the use of clz/bsr cannot be
* shown to have a significant performance impact even on the x86 chips that
* have a fast implementation of it. When building for Armv6, you can
* explicitly disable the use of clz/bsr by adding -mthumb to the compiler
* flags (this defines __thumb__).
*/
/* NOTE: Both GCC and Clang define __GNUC__ */
#if (defined(__GNUC__) && (defined(__arm__) || defined(__aarch64__))) || \
defined(_M_ARM) || defined(_M_ARM64)
#if !defined(__thumb__) || defined(__thumb2__)
#define USE_CLZ_INTRINSIC
#endif
#endif
#ifdef USE_CLZ_INTRINSIC
#if defined(_MSC_VER) && !defined(__clang__)
#define JPEG_NBITS_NONZERO(x) (32 - _CountLeadingZeros(x))
#else
#define JPEG_NBITS_NONZERO(x) (32 - __builtin_clz(x))
#endif
#define JPEG_NBITS(x) (x ? JPEG_NBITS_NONZERO(x) : 0)
#else
#include "jpeg_nbits_table.h"
#define JPEG_NBITS(x) (jpeg_nbits_table[x])
#define JPEG_NBITS_NONZERO(x) JPEG_NBITS(x)
#endif
/* Expanded entropy encoder object for Huffman encoding.
*
* The savable_state subrecord contains fields that change within an MCU,
* but must not be updated permanently until we complete the MCU.
*/
#if defined(__x86_64__) && defined(__ILP32__)
typedef unsigned long long bit_buf_type;
#else
typedef size_t bit_buf_type;
#endif
/* NOTE: The more optimal Huffman encoding algorithm is only used by the
* intrinsics implementation of the Arm Neon SIMD extensions, which is why we
* retain the old Huffman encoder behavior when using the GAS implementation.
*/
#if defined(WITH_SIMD) && !(defined(__arm__) || defined(__aarch64__) || \
defined(_M_ARM) || defined(_M_ARM64))
typedef unsigned long long simd_bit_buf_type;
#else
typedef bit_buf_type simd_bit_buf_type;
#endif
#if (defined(SIZEOF_SIZE_T) && SIZEOF_SIZE_T == 8) || defined(_WIN64) || \
(defined(__x86_64__) && defined(__ILP32__))
#define BIT_BUF_SIZE 64
#elif (defined(SIZEOF_SIZE_T) && SIZEOF_SIZE_T == 4) || defined(_WIN32)
#define BIT_BUF_SIZE 32
#else
#error Cannot determine word size
#endif
#define SIMD_BIT_BUF_SIZE (sizeof(simd_bit_buf_type) * 8)
typedef struct {
union {
bit_buf_type c;
simd_bit_buf_type simd;
} put_buffer; /* current bit accumulation buffer */
int free_bits; /* # of bits available in it */
/* (Neon GAS: # of bits now in it) */
int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
} savable_state;
typedef struct {
struct jpeg_entropy_encoder pub; /* public fields */
savable_state saved; /* Bit buffer & DC state at start of MCU */
/* These fields are NOT loaded into local working state. */
unsigned int restarts_to_go; /* MCUs left in this restart interval */
int next_restart_num; /* next restart number to write (0-7) */
/* Pointers to derived tables (these workspaces have image lifespan) */
c_derived_tbl *dc_derived_tbls[NUM_HUFF_TBLS];
c_derived_tbl *ac_derived_tbls[NUM_HUFF_TBLS];
#ifdef ENTROPY_OPT_SUPPORTED /* Statistics tables for optimization */
long *dc_count_ptrs[NUM_HUFF_TBLS];
long *ac_count_ptrs[NUM_HUFF_TBLS];
#endif
int simd;
} huff_entropy_encoder;
typedef huff_entropy_encoder *huff_entropy_ptr;
/* Working state while writing an MCU.
* This struct contains all the fields that are needed by subroutines.
*/
typedef struct {
JOCTET *next_output_byte; /* => next byte to write in buffer */
size_t free_in_buffer; /* # of byte spaces remaining in buffer */
savable_state cur; /* Current bit buffer & DC state */
j_compress_ptr cinfo; /* dump_buffer needs access to this */
int simd;
} working_state;
/* Forward declarations */
METHODDEF(boolean) encode_mcu_huff(j_compress_ptr cinfo, JBLOCKROW *MCU_data);
METHODDEF(void) finish_pass_huff(j_compress_ptr cinfo);
#ifdef ENTROPY_OPT_SUPPORTED
METHODDEF(boolean) encode_mcu_gather(j_compress_ptr cinfo,
JBLOCKROW *MCU_data);
METHODDEF(void) finish_pass_gather(j_compress_ptr cinfo);
#endif
/*
* Initialize for a Huffman-compressed scan.
* If gather_statistics is TRUE, we do not output anything during the scan,
* just count the Huffman symbols used and generate Huffman code tables.
*/
METHODDEF(void)
start_pass_huff(j_compress_ptr cinfo, boolean gather_statistics)
{
huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
int ci, dctbl, actbl;
jpeg_component_info *compptr;
if (gather_statistics) {
#ifdef ENTROPY_OPT_SUPPORTED
entropy->pub.encode_mcu = encode_mcu_gather;
entropy->pub.finish_pass = finish_pass_gather;
#else
ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
} else {
entropy->pub.encode_mcu = encode_mcu_huff;
entropy->pub.finish_pass = finish_pass_huff;
}
entropy->simd = jsimd_can_huff_encode_one_block();
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
compptr = cinfo->cur_comp_info[ci];
dctbl = compptr->dc_tbl_no;
actbl = compptr->ac_tbl_no;
if (gather_statistics) {
#ifdef ENTROPY_OPT_SUPPORTED
/* Check for invalid table indexes */
/* (make_c_derived_tbl does this in the other path) */
if (dctbl < 0 || dctbl >= NUM_HUFF_TBLS)
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, dctbl);
if (actbl < 0 || actbl >= NUM_HUFF_TBLS)
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, actbl);
/* Allocate and zero the statistics tables */
/* Note that jpeg_gen_optimal_table expects 257 entries in each table! */
if (entropy->dc_count_ptrs[dctbl] == NULL)
entropy->dc_count_ptrs[dctbl] = (long *)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
257 * sizeof(long));
memset(entropy->dc_count_ptrs[dctbl], 0, 257 * sizeof(long));
if (entropy->ac_count_ptrs[actbl] == NULL)
entropy->ac_count_ptrs[actbl] = (long *)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
257 * sizeof(long));
memset(entropy->ac_count_ptrs[actbl], 0, 257 * sizeof(long));
#endif
} else {
/* Compute derived values for Huffman tables */
/* We may do this more than once for a table, but it's not expensive */
jpeg_make_c_derived_tbl(cinfo, TRUE, dctbl,
&entropy->dc_derived_tbls[dctbl]);
jpeg_make_c_derived_tbl(cinfo, FALSE, actbl,
&entropy->ac_derived_tbls[actbl]);
}
/* Initialize DC predictions to 0 */
entropy->saved.last_dc_val[ci] = 0;
}
/* Initialize bit buffer to empty */
if (entropy->simd) {
entropy->saved.put_buffer.simd = 0;
#if defined(__aarch64__) && !defined(NEON_INTRINSICS)
entropy->saved.free_bits = 0;
#else
entropy->saved.free_bits = SIMD_BIT_BUF_SIZE;
#endif
} else {
entropy->saved.put_buffer.c = 0;
entropy->saved.free_bits = BIT_BUF_SIZE;
}
/* Initialize restart stuff */
entropy->restarts_to_go = cinfo->restart_interval;
entropy->next_restart_num = 0;
}
/*
* Compute the derived values for a Huffman table.
* This routine also performs some validation checks on the table.
*
* Note this is also used by jcphuff.c.
*/
GLOBAL(void)
jpeg_make_c_derived_tbl(j_compress_ptr cinfo, boolean isDC, int tblno,
c_derived_tbl **pdtbl)
{
JHUFF_TBL *htbl;
c_derived_tbl *dtbl;
int p, i, l, lastp, si, maxsymbol;
char huffsize[257];
unsigned int huffcode[257];
unsigned int code;
/* Note that huffsize[] and huffcode[] are filled in code-length order,
* paralleling the order of the symbols themselves in htbl->huffval[].
*/
/* Find the input Huffman table */
if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
htbl =
isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
if (htbl == NULL)
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
/* Allocate a workspace if we haven't already done so. */
if (*pdtbl == NULL)
*pdtbl = (c_derived_tbl *)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
sizeof(c_derived_tbl));
dtbl = *pdtbl;
/* Figure C.1: make table of Huffman code length for each symbol */
p = 0;
for (l = 1; l <= 16; l++) {
i = (int)htbl->bits[l];
if (i < 0 || p + i > 256) /* protect against table overrun */
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
while (i--)
huffsize[p++] = (char)l;
}
huffsize[p] = 0;
lastp = p;
/* Figure C.2: generate the codes themselves */
/* We also validate that the counts represent a legal Huffman code tree. */
code = 0;
si = huffsize[0];
p = 0;
while (huffsize[p]) {
while (((int)huffsize[p]) == si) {
huffcode[p++] = code;
code++;
}
/* code is now 1 more than the last code used for codelength si; but
* it must still fit in si bits, since no code is allowed to be all ones.
*/
if (((JLONG)code) >= (((JLONG)1) << si))
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
code <<= 1;
si++;
}
/* Figure C.3: generate encoding tables */
/* These are code and size indexed by symbol value */
/* Set all codeless symbols to have code length 0;
* this lets us detect duplicate VAL entries here, and later
* allows emit_bits to detect any attempt to emit such symbols.
*/
memset(dtbl->ehufco, 0, sizeof(dtbl->ehufco));
memset(dtbl->ehufsi, 0, sizeof(dtbl->ehufsi));
/* This is also a convenient place to check for out-of-range
* and duplicated VAL entries. We allow 0..255 for AC symbols
* but only 0..15 for DC. (We could constrain them further
* based on data depth and mode, but this seems enough.)
*/
maxsymbol = isDC ? 15 : 255;
for (p = 0; p < lastp; p++) {
i = htbl->huffval[p];
if (i < 0 || i > maxsymbol || dtbl->ehufsi[i])
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
dtbl->ehufco[i] = huffcode[p];
dtbl->ehufsi[i] = huffsize[p];
}
}
/* Outputting bytes to the file */
/* Emit a byte, taking 'action' if must suspend. */
#define emit_byte(state, val, action) { \
*(state)->next_output_byte++ = (JOCTET)(val); \
if (--(state)->free_in_buffer == 0) \
if (!dump_buffer(state)) \
{ action; } \
}
LOCAL(boolean)
dump_buffer(working_state *state)
/* Empty the output buffer; return TRUE if successful, FALSE if must suspend */
{
struct jpeg_destination_mgr *dest = state->cinfo->dest;
if (!(*dest->empty_output_buffer) (state->cinfo))
return FALSE;
/* After a successful buffer dump, must reset buffer pointers */
state->next_output_byte = dest->next_output_byte;
state->free_in_buffer = dest->free_in_buffer;
return TRUE;
}
/* Outputting bits to the file */
/* Output byte b and, speculatively, an additional 0 byte. 0xFF must be
* encoded as 0xFF 0x00, so the output buffer pointer is advanced by 2 if the
* byte is 0xFF. Otherwise, the output buffer pointer is advanced by 1, and
* the speculative 0 byte will be overwritten by the next byte.
*/
#define EMIT_BYTE(b) { \
buffer[0] = (JOCTET)(b); \
buffer[1] = 0; \
buffer -= -2 + ((JOCTET)(b) < 0xFF); \
}
/* Output the entire bit buffer. If there are no 0xFF bytes in it, then write
* directly to the output buffer. Otherwise, use the EMIT_BYTE() macro to
* encode 0xFF as 0xFF 0x00.
*/
#if BIT_BUF_SIZE == 64
#define FLUSH() { \
if (put_buffer & 0x8080808080808080 & ~(put_buffer + 0x0101010101010101)) { \
EMIT_BYTE(put_buffer >> 56) \
EMIT_BYTE(put_buffer >> 48) \
EMIT_BYTE(put_buffer >> 40) \
EMIT_BYTE(put_buffer >> 32) \
EMIT_BYTE(put_buffer >> 24) \
EMIT_BYTE(put_buffer >> 16) \
EMIT_BYTE(put_buffer >> 8) \
EMIT_BYTE(put_buffer ) \
} else { \
buffer[0] = (JOCTET)(put_buffer >> 56); \
buffer[1] = (JOCTET)(put_buffer >> 48); \
buffer[2] = (JOCTET)(put_buffer >> 40); \
buffer[3] = (JOCTET)(put_buffer >> 32); \
buffer[4] = (JOCTET)(put_buffer >> 24); \
buffer[5] = (JOCTET)(put_buffer >> 16); \
buffer[6] = (JOCTET)(put_buffer >> 8); \
buffer[7] = (JOCTET)(put_buffer); \
buffer += 8; \
} \
}
#else
#define FLUSH() { \
if (put_buffer & 0x80808080 & ~(put_buffer + 0x01010101)) { \
EMIT_BYTE(put_buffer >> 24) \
EMIT_BYTE(put_buffer >> 16) \
EMIT_BYTE(put_buffer >> 8) \
EMIT_BYTE(put_buffer ) \
} else { \
buffer[0] = (JOCTET)(put_buffer >> 24); \
buffer[1] = (JOCTET)(put_buffer >> 16); \
buffer[2] = (JOCTET)(put_buffer >> 8); \
buffer[3] = (JOCTET)(put_buffer); \
buffer += 4; \
} \
}
#endif
/* Fill the bit buffer to capacity with the leading bits from code, then output
* the bit buffer and put the remaining bits from code into the bit buffer.
*/
#define PUT_AND_FLUSH(code, size) { \
put_buffer = (put_buffer << (size + free_bits)) | (code >> -free_bits); \
FLUSH() \
free_bits += BIT_BUF_SIZE; \
put_buffer = code; \
}
/* Insert code into the bit buffer and output the bit buffer if needed.
* NOTE: We can't flush with free_bits == 0, since the left shift in
* PUT_AND_FLUSH() would have undefined behavior.
*/
#define PUT_BITS(code, size) { \
free_bits -= size; \
if (free_bits < 0) \
PUT_AND_FLUSH(code, size) \
else \
put_buffer = (put_buffer << size) | code; \
}
#define PUT_CODE(code, size) { \
temp &= (((JLONG)1) << nbits) - 1; \
temp |= code << nbits; \
nbits += size; \
PUT_BITS(temp, nbits) \
}
/* Although it is exceedingly rare, it is possible for a Huffman-encoded
* coefficient block to be larger than the 128-byte unencoded block. For each
* of the 64 coefficients, PUT_BITS is invoked twice, and each invocation can
* theoretically store 16 bits (for a maximum of 2048 bits or 256 bytes per
* encoded block.) If, for instance, one artificially sets the AC
* coefficients to alternating values of 32767 and -32768 (using the JPEG
* scanning order-- 1, 8, 16, etc.), then this will produce an encoded block
* larger than 200 bytes.
*/
#define BUFSIZE (DCTSIZE2 * 8)
#define LOAD_BUFFER() { \
if (state->free_in_buffer < BUFSIZE) { \
localbuf = 1; \
buffer = _buffer; \
} else \
buffer = state->next_output_byte; \
}
#define STORE_BUFFER() { \
if (localbuf) { \
size_t bytes, bytestocopy; \
bytes = buffer - _buffer; \
buffer = _buffer; \
while (bytes > 0) { \
bytestocopy = MIN(bytes, state->free_in_buffer); \
memcpy(state->next_output_byte, buffer, bytestocopy); \
state->next_output_byte += bytestocopy; \
buffer += bytestocopy; \
state->free_in_buffer -= bytestocopy; \
if (state->free_in_buffer == 0) \
if (!dump_buffer(state)) return FALSE; \
bytes -= bytestocopy; \
} \
} else { \
state->free_in_buffer -= (buffer - state->next_output_byte); \
state->next_output_byte = buffer; \
} \
}
LOCAL(boolean)
flush_bits(working_state *state)
{
JOCTET _buffer[BUFSIZE], *buffer, temp;
simd_bit_buf_type put_buffer; int put_bits;
int localbuf = 0;
if (state->simd) {
#if defined(__aarch64__) && !defined(NEON_INTRINSICS)
put_bits = state->cur.free_bits;
#else
put_bits = SIMD_BIT_BUF_SIZE - state->cur.free_bits;
#endif
put_buffer = state->cur.put_buffer.simd;
} else {
put_bits = BIT_BUF_SIZE - state->cur.free_bits;
put_buffer = state->cur.put_buffer.c;
}
LOAD_BUFFER()
while (put_bits >= 8) {
put_bits -= 8;
temp = (JOCTET)(put_buffer >> put_bits);
EMIT_BYTE(temp)
}
if (put_bits) {
/* fill partial byte with ones */
temp = (JOCTET)((put_buffer << (8 - put_bits)) | (0xFF >> put_bits));
EMIT_BYTE(temp)
}
if (state->simd) { /* and reset bit buffer to empty */
state->cur.put_buffer.simd = 0;
#if defined(__aarch64__) && !defined(NEON_INTRINSICS)
state->cur.free_bits = 0;
#else
state->cur.free_bits = SIMD_BIT_BUF_SIZE;
#endif
} else {
state->cur.put_buffer.c = 0;
state->cur.free_bits = BIT_BUF_SIZE;
}
STORE_BUFFER()
return TRUE;
}
/* Encode a single block's worth of coefficients */
LOCAL(boolean)
encode_one_block_simd(working_state *state, JCOEFPTR block, int last_dc_val,
c_derived_tbl *dctbl, c_derived_tbl *actbl)
{
JOCTET _buffer[BUFSIZE], *buffer;
int localbuf = 0;
LOAD_BUFFER()
buffer = jsimd_huff_encode_one_block(state, buffer, block, last_dc_val,
dctbl, actbl);
STORE_BUFFER()
return TRUE;
}
LOCAL(boolean)
encode_one_block(working_state *state, JCOEFPTR block, int last_dc_val,
c_derived_tbl *dctbl, c_derived_tbl *actbl)
{
int temp, nbits, free_bits;
bit_buf_type put_buffer;
JOCTET _buffer[BUFSIZE], *buffer;
int localbuf = 0;
free_bits = state->cur.free_bits;
put_buffer = state->cur.put_buffer.c;
LOAD_BUFFER()
/* Encode the DC coefficient difference per section F.1.2.1 */
temp = block[0] - last_dc_val;
/* This is a well-known technique for obtaining the absolute value without a
* branch. It is derived from an assembly language technique presented in
* "How to Optimize for the Pentium Processors", Copyright (c) 1996, 1997 by
* Agner Fog. This code assumes we are on a two's complement machine.
*/
nbits = temp >> (CHAR_BIT * sizeof(int) - 1);
temp += nbits;
nbits ^= temp;
/* Find the number of bits needed for the magnitude of the coefficient */
nbits = JPEG_NBITS(nbits);
/* Emit the Huffman-coded symbol for the number of bits.
* Emit that number of bits of the value, if positive,
* or the complement of its magnitude, if negative.
*/
PUT_CODE(dctbl->ehufco[nbits], dctbl->ehufsi[nbits])
/* Encode the AC coefficients per section F.1.2.2 */
{
int r = 0; /* r = run length of zeros */
/* Manually unroll the k loop to eliminate the counter variable. This
* improves performance greatly on systems with a limited number of
* registers (such as x86.)
*/
#define kloop(jpeg_natural_order_of_k) { \
if ((temp = block[jpeg_natural_order_of_k]) == 0) { \
r += 16; \
} else { \
/* Branch-less absolute value, bitwise complement, etc., same as above */ \
nbits = temp >> (CHAR_BIT * sizeof(int) - 1); \
temp += nbits; \
nbits ^= temp; \
nbits = JPEG_NBITS_NONZERO(nbits); \
/* if run length > 15, must emit special run-length-16 codes (0xF0) */ \
while (r >= 16 * 16) { \
r -= 16 * 16; \
PUT_BITS(actbl->ehufco[0xf0], actbl->ehufsi[0xf0]) \
} \
/* Emit Huffman symbol for run length / number of bits */ \
r += nbits; \
PUT_CODE(actbl->ehufco[r], actbl->ehufsi[r]) \
r = 0; \
} \
}
/* One iteration for each value in jpeg_natural_order[] */
kloop(1); kloop(8); kloop(16); kloop(9); kloop(2); kloop(3);
kloop(10); kloop(17); kloop(24); kloop(32); kloop(25); kloop(18);
kloop(11); kloop(4); kloop(5); kloop(12); kloop(19); kloop(26);
kloop(33); kloop(40); kloop(48); kloop(41); kloop(34); kloop(27);
kloop(20); kloop(13); kloop(6); kloop(7); kloop(14); kloop(21);
kloop(28); kloop(35); kloop(42); kloop(49); kloop(56); kloop(57);
kloop(50); kloop(43); kloop(36); kloop(29); kloop(22); kloop(15);
kloop(23); kloop(30); kloop(37); kloop(44); kloop(51); kloop(58);
kloop(59); kloop(52); kloop(45); kloop(38); kloop(31); kloop(39);
kloop(46); kloop(53); kloop(60); kloop(61); kloop(54); kloop(47);
kloop(55); kloop(62); kloop(63);
/* If the last coef(s) were zero, emit an end-of-block code */
if (r > 0) {
PUT_BITS(actbl->ehufco[0], actbl->ehufsi[0])
}
}
state->cur.put_buffer.c = put_buffer;
state->cur.free_bits = free_bits;
STORE_BUFFER()
return TRUE;
}
/*
* Emit a restart marker & resynchronize predictions.
*/
LOCAL(boolean)
emit_restart(working_state *state, int restart_num)
{
int ci;
if (!flush_bits(state))
return FALSE;
emit_byte(state, 0xFF, return FALSE);
emit_byte(state, JPEG_RST0 + restart_num, return FALSE);
/* Re-initialize DC predictions to 0 */
for (ci = 0; ci < state->cinfo->comps_in_scan; ci++)
state->cur.last_dc_val[ci] = 0;
/* The restart counter is not updated until we successfully write the MCU. */
return TRUE;
}
/*
* Encode and output one MCU's worth of Huffman-compressed coefficients.
*/
METHODDEF(boolean)
encode_mcu_huff(j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
working_state state;
int blkn, ci;
jpeg_component_info *compptr;
/* Load up working state */
state.next_output_byte = cinfo->dest->next_output_byte;
state.free_in_buffer = cinfo->dest->free_in_buffer;
state.cur = entropy->saved;
state.cinfo = cinfo;
state.simd = entropy->simd;
/* Emit restart marker if needed */
if (cinfo->restart_interval) {
if (entropy->restarts_to_go == 0)
if (!emit_restart(&state, entropy->next_restart_num))
return FALSE;
}
/* Encode the MCU data blocks */
if (entropy->simd) {
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
ci = cinfo->MCU_membership[blkn];
compptr = cinfo->cur_comp_info[ci];
if (!encode_one_block_simd(&state,
MCU_data[blkn][0], state.cur.last_dc_val[ci],
entropy->dc_derived_tbls[compptr->dc_tbl_no],
entropy->ac_derived_tbls[compptr->ac_tbl_no]))
return FALSE;
/* Update last_dc_val */
state.cur.last_dc_val[ci] = MCU_data[blkn][0][0];
}
} else {
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
ci = cinfo->MCU_membership[blkn];
compptr = cinfo->cur_comp_info[ci];
if (!encode_one_block(&state,
MCU_data[blkn][0], state.cur.last_dc_val[ci],
entropy->dc_derived_tbls[compptr->dc_tbl_no],
entropy->ac_derived_tbls[compptr->ac_tbl_no]))
return FALSE;
/* Update last_dc_val */
state.cur.last_dc_val[ci] = MCU_data[blkn][0][0];
}
}
/* Completed MCU, so update state */
cinfo->dest->next_output_byte = state.next_output_byte;
cinfo->dest->free_in_buffer = state.free_in_buffer;
entropy->saved = state.cur;
/* Update restart-interval state too */
if (cinfo->restart_interval) {
if (entropy->restarts_to_go == 0) {
entropy->restarts_to_go = cinfo->restart_interval;
entropy->next_restart_num++;
entropy->next_restart_num &= 7;
}
entropy->restarts_to_go--;
}
return TRUE;
}
/*
* Finish up at the end of a Huffman-compressed scan.
*/
METHODDEF(void)
finish_pass_huff(j_compress_ptr cinfo)
{
huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
working_state state;
/* Load up working state ... flush_bits needs it */
state.next_output_byte = cinfo->dest->next_output_byte;
state.free_in_buffer = cinfo->dest->free_in_buffer;
state.cur = entropy->saved;
state.cinfo = cinfo;
state.simd = entropy->simd;
/* Flush out the last data */
if (!flush_bits(&state))
ERREXIT(cinfo, JERR_CANT_SUSPEND);
/* Update state */
cinfo->dest->next_output_byte = state.next_output_byte;
cinfo->dest->free_in_buffer = state.free_in_buffer;
entropy->saved = state.cur;
}
/*
* Huffman coding optimization.
*
* We first scan the supplied data and count the number of uses of each symbol
* that is to be Huffman-coded. (This process MUST agree with the code above.)
* Then we build a Huffman coding tree for the observed counts.
* Symbols which are not needed at all for the particular image are not
* assigned any code, which saves space in the DHT marker as well as in
* the compressed data.
*/
#ifdef ENTROPY_OPT_SUPPORTED
/* Process a single block's worth of coefficients */
LOCAL(void)
htest_one_block(j_compress_ptr cinfo, JCOEFPTR block, int last_dc_val,
long dc_counts[], long ac_counts[])
{
register int temp;
register int nbits;
register int k, r;
/* Encode the DC coefficient difference per section F.1.2.1 */
temp = block[0] - last_dc_val;
if (temp < 0)
temp = -temp;
/* Find the number of bits needed for the magnitude of the coefficient */
nbits = 0;
while (temp) {
nbits++;
temp >>= 1;
}
/* Check for out-of-range coefficient values.
* Since we're encoding a difference, the range limit is twice as much.
*/
if (nbits > MAX_COEF_BITS + 1)
ERREXIT(cinfo, JERR_BAD_DCT_COEF);
/* Count the Huffman symbol for the number of bits */
dc_counts[nbits]++;
/* Encode the AC coefficients per section F.1.2.2 */
r = 0; /* r = run length of zeros */
for (k = 1; k < DCTSIZE2; k++) {
if ((temp = block[jpeg_natural_order[k]]) == 0) {
r++;
} else {
/* if run length > 15, must emit special run-length-16 codes (0xF0) */
while (r > 15) {
ac_counts[0xF0]++;
r -= 16;
}
/* Find the number of bits needed for the magnitude of the coefficient */
if (temp < 0)
temp = -temp;
/* Find the number of bits needed for the magnitude of the coefficient */
nbits = 1; /* there must be at least one 1 bit */
while ((temp >>= 1))
nbits++;
/* Check for out-of-range coefficient values */
if (nbits > MAX_COEF_BITS)
ERREXIT(cinfo, JERR_BAD_DCT_COEF);
/* Count Huffman symbol for run length / number of bits */
ac_counts[(r << 4) + nbits]++;
r = 0;
}
}
/* If the last coef(s) were zero, emit an end-of-block code */
if (r > 0)
ac_counts[0]++;
}
/*
* Trial-encode one MCU's worth of Huffman-compressed coefficients.
* No data is actually output, so no suspension return is possible.
*/
METHODDEF(boolean)
encode_mcu_gather(j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
int blkn, ci;
jpeg_component_info *compptr;
/* Take care of restart intervals if needed */
if (cinfo->restart_interval) {
if (entropy->restarts_to_go == 0) {
/* Re-initialize DC predictions to 0 */
for (ci = 0; ci < cinfo->comps_in_scan; ci++)
entropy->saved.last_dc_val[ci] = 0;
/* Update restart state */
entropy->restarts_to_go = cinfo->restart_interval;
}
entropy->restarts_to_go--;
}
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
ci = cinfo->MCU_membership[blkn];
compptr = cinfo->cur_comp_info[ci];
htest_one_block(cinfo, MCU_data[blkn][0], entropy->saved.last_dc_val[ci],
entropy->dc_count_ptrs[compptr->dc_tbl_no],
entropy->ac_count_ptrs[compptr->ac_tbl_no]);
entropy->saved.last_dc_val[ci] = MCU_data[blkn][0][0];
}
return TRUE;
}
/*
* Generate the best Huffman code table for the given counts, fill htbl.
* Note this is also used by jcphuff.c.
*
* The JPEG standard requires that no symbol be assigned a codeword of all
* one bits (so that padding bits added at the end of a compressed segment
* can't look like a valid code). Because of the canonical ordering of
* codewords, this just means that there must be an unused slot in the
* longest codeword length category. Annex K (Clause K.2) of
* Rec. ITU-T T.81 (1992) | ISO/IEC 10918-1:1994 suggests reserving such a slot
* by pretending that symbol 256 is a valid symbol with count 1. In theory
* that's not optimal; giving it count zero but including it in the symbol set
* anyway should give a better Huffman code. But the theoretically better code
* actually seems to come out worse in practice, because it produces more
* all-ones bytes (which incur stuffed zero bytes in the final file). In any
* case the difference is tiny.
*
* The JPEG standard requires Huffman codes to be no more than 16 bits long.
* If some symbols have a very small but nonzero probability, the Huffman tree
* must be adjusted to meet the code length restriction. We currently use
* the adjustment method suggested in JPEG section K.2. This method is *not*
* optimal; it may not choose the best possible limited-length code. But
* typically only very-low-frequency symbols will be given less-than-optimal
* lengths, so the code is almost optimal. Experimental comparisons against
* an optimal limited-length-code algorithm indicate that the difference is
* microscopic --- usually less than a hundredth of a percent of total size.
* So the extra complexity of an optimal algorithm doesn't seem worthwhile.
*/
GLOBAL(void)
jpeg_gen_optimal_table(j_compress_ptr cinfo, JHUFF_TBL *htbl, long freq[])
{
#define MAX_CLEN 32 /* assumed maximum initial code length */
UINT8 bits[MAX_CLEN + 1]; /* bits[k] = # of symbols with code length k */
int codesize[257]; /* codesize[k] = code length of symbol k */
int others[257]; /* next symbol in current branch of tree */
int c1, c2;
int p, i, j;
long v;
/* This algorithm is explained in section K.2 of the JPEG standard */
memset(bits, 0, sizeof(bits));
memset(codesize, 0, sizeof(codesize));
for (i = 0; i < 257; i++)
others[i] = -1; /* init links to empty */
freq[256] = 1; /* make sure 256 has a nonzero count */
/* Including the pseudo-symbol 256 in the Huffman procedure guarantees
* that no real symbol is given code-value of all ones, because 256
* will be placed last in the largest codeword category.
*/
/* Huffman's basic algorithm to assign optimal code lengths to symbols */
for (;;) {
/* Find the smallest nonzero frequency, set c1 = its symbol */
/* In case of ties, take the larger symbol number */
c1 = -1;
v = 1000000000L;
for (i = 0; i <= 256; i++) {
if (freq[i] && freq[i] <= v) {
v = freq[i];
c1 = i;
}
}
/* Find the next smallest nonzero frequency, set c2 = its symbol */
/* In case of ties, take the larger symbol number */
c2 = -1;
v = 1000000000L;
for (i = 0; i <= 256; i++) {
if (freq[i] && freq[i] <= v && i != c1) {
v = freq[i];
c2 = i;
}
}
/* Done if we've merged everything into one frequency */
if (c2 < 0)
break;
/* Else merge the two counts/trees */
freq[c1] += freq[c2];
freq[c2] = 0;
/* Increment the codesize of everything in c1's tree branch */
codesize[c1]++;
while (others[c1] >= 0) {
c1 = others[c1];
codesize[c1]++;
}
others[c1] = c2; /* chain c2 onto c1's tree branch */
/* Increment the codesize of everything in c2's tree branch */
codesize[c2]++;
while (others[c2] >= 0) {
c2 = others[c2];