1 /*
2 * jdhuff.c
3 *
4 * Copyright (C) 1991-1997, Thomas G. Lane.
5 * Modified 2006-2009 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
8 *
9 * This file contains Huffman entropy decoding routines.
10 * Both sequential and progressive modes are supported in this single module.
11 *
12 * Much of the complexity here has to do with supporting input suspension.
13 * If the data source module demands suspension, we want to be able to back
14 * up to the start of the current MCU. To do this, we copy state variables
15 * into local working storage, and update them back to the permanent
16 * storage only upon successful completion of an MCU.
17 */
18
19 #define JPEG_INTERNALS
20 #include "jinclude.h"
21 #include "jpeglib.h"
22
23
24 /* Derived data constructed for each Huffman table */
25
212 #define ASSIGN_STATE(dest,src) \
213 ((dest).EOBRUN = (src).EOBRUN, \
214 (dest).last_dc_val[0] = (src).last_dc_val[0], \
215 (dest).last_dc_val[1] = (src).last_dc_val[1], \
216 (dest).last_dc_val[2] = (src).last_dc_val[2], \
217 (dest).last_dc_val[3] = (src).last_dc_val[3])
218 #endif
219 #endif
220
221
222 typedef struct {
223 struct jpeg_entropy_decoder pub; /* public fields */
224
225 /* These fields are loaded into local variables at start of each MCU.
226 * In case of suspension, we exit WITHOUT updating them.
227 */
228 bitread_perm_state bitstate; /* Bit buffer at start of MCU */
229 savable_state saved; /* Other state at start of MCU */
230
231 /* These fields are NOT loaded into local working state. */
232 unsigned int restarts_to_go; /* MCUs left in this restart interval */
233
234 /* Following two fields used only in progressive mode */
235
236 /* Pointers to derived tables (these workspaces have image lifespan) */
237 d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
238
239 d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
240
241 /* Following fields used only in sequential mode */
242
243 /* Pointers to derived tables (these workspaces have image lifespan) */
244 d_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
245 d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
246
247 /* Precalculated info set up by start_pass for use in decode_mcu: */
248
249 /* Pointers to derived tables to be used for each block within an MCU */
250 d_derived_tbl * dc_cur_tbls[D_MAX_BLOCKS_IN_MCU];
251 d_derived_tbl * ac_cur_tbls[D_MAX_BLOCKS_IN_MCU];
252 /* Whether we care about the DC and AC coefficient values for each block */
253 int coef_limit[D_MAX_BLOCKS_IN_MCU];
254 } huff_entropy_decoder;
255
256 typedef huff_entropy_decoder * huff_entropy_ptr;
257
258
259 static const int jpeg_zigzag_order[8][8] = {
260 { 0, 1, 5, 6, 14, 15, 27, 28 },
261 { 2, 4, 7, 13, 16, 26, 29, 42 },
262 { 3, 8, 12, 17, 25, 30, 41, 43 },
263 { 9, 11, 18, 24, 31, 40, 44, 53 },
264 { 10, 19, 23, 32, 39, 45, 52, 54 },
265 { 20, 22, 33, 38, 46, 51, 55, 60 },
266 { 21, 34, 37, 47, 50, 56, 59, 61 },
267 { 35, 36, 48, 49, 57, 58, 62, 63 }
268 };
269
270
271 /*
272 * Compute the derived values for a Huffman table.
273 * This routine also performs some validation checks on the table.
274 */
275
276 LOCAL(void)
277 jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno,
278 d_derived_tbl ** pdtbl)
279 {
280 JHUFF_TBL *htbl;
281 d_derived_tbl *dtbl;
282 int p, i, l, si, numsymbols;
283 int lookbits, ctr;
284 char huffsize[257];
285 unsigned int huffcode[257];
286 unsigned int code;
287
288 MEMZERO(huffsize, SIZEOF(huffsize));
289 MEMZERO(huffcode, SIZEOF(huffcode));
290
291 /* Note that huffsize[] and huffcode[] are filled in code-length order,
292 * paralleling the order of the symbols themselves in htbl->huffval[].
293 */
294
295 /* Find the input Huffman table */
296 if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
297 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
298 htbl =
299 isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
300 if (htbl == NULL)
301 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
302
303 /* Allocate a workspace if we haven't already done so. */
304 if (*pdtbl == NULL)
305 *pdtbl = (d_derived_tbl *)
306 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
307 SIZEOF(d_derived_tbl));
308 dtbl = *pdtbl;
309 dtbl->pub = htbl; /* fill in back link */
310
482 goto no_more_bytes;
483 }
484 }
485
486 /* OK, load c into get_buffer */
487 get_buffer = (get_buffer << 8) | c;
488 bits_left += 8;
489 } /* end while */
490 } else {
491 no_more_bytes:
492 /* We get here if we've read the marker that terminates the compressed
493 * data segment. There should be enough bits in the buffer register
494 * to satisfy the request; if so, no problem.
495 */
496 if (nbits > bits_left) {
497 /* Uh-oh. Report corrupted data to user and stuff zeroes into
498 * the data stream, so that we can produce some kind of image.
499 * We use a nonvolatile flag to ensure that only one warning message
500 * appears per data segment.
501 */
502 if (! cinfo->entropy->insufficient_data) {
503 WARNMS(cinfo, JWRN_HIT_MARKER);
504 cinfo->entropy->insufficient_data = TRUE;
505 }
506 /* Fill the buffer with zero bits */
507 get_buffer <<= MIN_GET_BITS - bits_left;
508 bits_left = MIN_GET_BITS;
509 }
510 }
511
512 /* Unload the local registers */
513 state->next_input_byte = next_input_byte;
514 state->bytes_in_buffer = bytes_in_buffer;
515 state->get_buffer = get_buffer;
516 state->bits_left = bits_left;
517
518 return TRUE;
519 }
520
521
522 /*
523 * Figure F.12: extend sign bit.
524 * On some machines, a shift and sub will be faster than a table lookup.
559 CHECK_BIT_BUFFER(*state, l, return -1);
560 code = GET_BITS(l);
561
562 /* Collect the rest of the Huffman code one bit at a time. */
563 /* This is per Figure F.16 in the JPEG spec. */
564
565 while (code > htbl->maxcode[l]) {
566 code <<= 1;
567 CHECK_BIT_BUFFER(*state, 1, return -1);
568 code |= GET_BITS(1);
569 l++;
570 }
571
572 /* Unload the local registers */
573 state->get_buffer = get_buffer;
574 state->bits_left = bits_left;
575
576 /* With garbage input we may reach the sentinel value l = 17. */
577
578 if (l > 16) {
579 int br_offset = state->next_input_byte - state->cinfo->src->next_input_byte;
580 WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
581 state->next_input_byte = state->cinfo->src->next_input_byte + br_offset;
582 return 0; /* fake a zero as the safest result */
583 }
584
585 return htbl->pub->huffval[ (int) (code + htbl->valoffset[l]) ];
586 }
587
588
589 /*
590 * Check for a restart marker & resynchronize decoder.
591 * Returns FALSE if must suspend.
592 */
593
594 LOCAL(boolean)
595 process_restart (j_decompress_ptr cinfo)
596 {
597 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
598 int ci;
599
600 /* Throw away any unused bits remaining in bit buffer; */
601 /* include any full bytes in next_marker's count of discarded bytes */
602 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
603 entropy->bitstate.bits_left = 0;
604
605 /* Advance past the RSTn marker */
606 if (! (*cinfo->marker->read_restart_marker) (cinfo))
607 return FALSE;
608
609 /* Re-initialize DC predictions to 0 */
610 for (ci = 0; ci < cinfo->comps_in_scan; ci++)
611 entropy->saved.last_dc_val[ci] = 0;
612 /* Re-init EOB run count, too */
613 entropy->saved.EOBRUN = 0;
614
615 /* Reset restart counter */
616 entropy->restarts_to_go = cinfo->restart_interval;
617
618 /* Reset out-of-data flag, unless read_restart_marker left us smack up
619 * against a marker. In that case we will end up treating the next data
620 * segment as empty, and we can avoid producing bogus output pixels by
621 * leaving the flag set.
622 */
623 if (cinfo->unread_marker == 0)
624 entropy->pub.insufficient_data = FALSE;
625
626 return TRUE;
627 }
628
629
630 /*
631 * Huffman MCU decoding.
632 * Each of these routines decodes and returns one MCU's worth of
633 * Huffman-compressed coefficients.
634 * The coefficients are reordered from zigzag order into natural array order,
635 * but are not dequantized.
636 *
637 * The i'th block of the MCU is stored into the block pointed to by
638 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
639 * (Wholesale zeroing is usually a little faster than retail...)
640 *
641 * We return FALSE if data source requested suspension. In that case no
642 * changes have been made to permanent state. (Exception: some output
643 * coefficients may already have been assigned. This is harmless for
644 * spectral selection, since we'll just re-assign them on the next call.
656 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
657 int Al = cinfo->Al;
658 register int s, r;
659 int blkn, ci;
660 JBLOCKROW block;
661 BITREAD_STATE_VARS;
662 savable_state state;
663 d_derived_tbl * tbl;
664 jpeg_component_info * compptr;
665
666 /* Process restart marker if needed; may have to suspend */
667 if (cinfo->restart_interval) {
668 if (entropy->restarts_to_go == 0)
669 if (! process_restart(cinfo))
670 return FALSE;
671 }
672
673 /* If we've run out of data, just leave the MCU set to zeroes.
674 * This way, we return uniform gray for the remainder of the segment.
675 */
676 if (! entropy->pub.insufficient_data) {
677
678 /* Load up working state */
679 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
680 ASSIGN_STATE(state, entropy->saved);
681
682 /* Outer loop handles each block in the MCU */
683
684 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
685 block = MCU_data[blkn];
686 ci = cinfo->MCU_membership[blkn];
687 compptr = cinfo->cur_comp_info[ci];
688 tbl = entropy->derived_tbls[compptr->dc_tbl_no];
689
690 /* Decode a single block's worth of coefficients */
691
692 /* Section F.2.2.1: decode the DC coefficient difference */
693 HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
694 if (s) {
695 CHECK_BIT_BUFFER(br_state, s, return FALSE);
696 r = GET_BITS(s);
708 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
709 ASSIGN_STATE(entropy->saved, state);
710 }
711
712 /* Account for restart interval (no-op if not using restarts) */
713 entropy->restarts_to_go--;
714
715 return TRUE;
716 }
717
718
719 /*
720 * MCU decoding for AC initial scan (either spectral selection,
721 * or first pass of successive approximation).
722 */
723
724 METHODDEF(boolean)
725 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
726 {
727 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
728 int Se = cinfo->Se;
729 int Al = cinfo->Al;
730 register int s, k, r;
731 unsigned int EOBRUN;
732 JBLOCKROW block;
733 BITREAD_STATE_VARS;
734 d_derived_tbl * tbl;
735
736 /* Process restart marker if needed; may have to suspend */
737 if (cinfo->restart_interval) {
738 if (entropy->restarts_to_go == 0)
739 if (! process_restart(cinfo))
740 return FALSE;
741 }
742
743 /* If we've run out of data, just leave the MCU set to zeroes.
744 * This way, we return uniform gray for the remainder of the segment.
745 */
746 if (! entropy->pub.insufficient_data) {
747
748 /* Load up working state.
749 * We can avoid loading/saving bitread state if in an EOB run.
750 */
751 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
752
753 /* There is always only one block per MCU */
754
755 if (EOBRUN > 0) /* if it's a band of zeroes... */
756 EOBRUN--; /* ...process it now (we do nothing) */
757 else {
758 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
759 block = MCU_data[0];
760 tbl = entropy->ac_derived_tbl;
761
762 for (k = cinfo->Ss; k <= Se; k++) {
763 HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
764 r = s >> 4;
765 s &= 15;
766 if (s) {
767 k += r;
768 CHECK_BIT_BUFFER(br_state, s, return FALSE);
769 r = GET_BITS(s);
770 s = HUFF_EXTEND(r, s);
771 /* Scale and output coefficient in natural (dezigzagged) order */
772 (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al);
773 } else {
774 if (r == 15) { /* ZRL */
775 k += 15; /* skip 15 zeroes in band */
776 } else { /* EOBr, run length is 2^r + appended bits */
777 EOBRUN = 1 << r;
778 if (r) { /* EOBr, r > 0 */
779 CHECK_BIT_BUFFER(br_state, r, return FALSE);
780 r = GET_BITS(r);
781 EOBRUN += r;
782 }
783 EOBRUN--; /* this band is processed at this moment */
784 break; /* force end-of-band */
785 }
786 }
787 }
788
789 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
790 }
791
792 /* Completed MCU, so update state */
793 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
794 }
795
796 /* Account for restart interval (no-op if not using restarts) */
797 entropy->restarts_to_go--;
798
799 return TRUE;
800 }
801
802
803 /*
804 * MCU decoding for DC successive approximation refinement scan.
805 * Note: we assume such scans can be multi-component, although the spec
806 * is not very clear on the point.
807 */
808
809 METHODDEF(boolean)
810 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
811 {
812 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
813 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
814 int blkn;
815 JBLOCKROW block;
816 BITREAD_STATE_VARS;
817
818 /* Process restart marker if needed; may have to suspend */
819 if (cinfo->restart_interval) {
820 if (entropy->restarts_to_go == 0)
821 if (! process_restart(cinfo))
822 return FALSE;
823 }
824
825 /* Not worth the cycles to check insufficient_data here,
826 * since we will not change the data anyway if we read zeroes.
827 */
828
829 /* Load up working state */
830 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
831
832 /* Outer loop handles each block in the MCU */
833
834 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
835 block = MCU_data[blkn];
836
837 /* Encoded data is simply the next bit of the two's-complement DC value */
838 CHECK_BIT_BUFFER(br_state, 1, return FALSE);
839 if (GET_BITS(1))
840 (*block)[0] |= p1;
841 /* Note: since we use |=, repeating the assignment later is safe */
842 }
843
844 /* Completed MCU, so update state */
845 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
846
847 /* Account for restart interval (no-op if not using restarts) */
848 entropy->restarts_to_go--;
849
850 return TRUE;
851 }
852
853
854 /*
855 * MCU decoding for AC successive approximation refinement scan.
856 */
857
858 METHODDEF(boolean)
859 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
860 {
861 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
862 int Se = cinfo->Se;
863 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
864 int m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */
865 register int s, k, r;
866 unsigned int EOBRUN;
867 JBLOCKROW block;
868 JCOEFPTR thiscoef;
869 BITREAD_STATE_VARS;
870 d_derived_tbl * tbl;
871 int num_newnz;
872 int newnz_pos[DCTSIZE2];
873
874 /* Process restart marker if needed; may have to suspend */
875 if (cinfo->restart_interval) {
876 if (entropy->restarts_to_go == 0)
877 if (! process_restart(cinfo))
878 return FALSE;
879 }
880
881 /* If we've run out of data, don't modify the MCU.
882 */
883 if (! entropy->pub.insufficient_data) {
884
885 /* Load up working state */
886 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
887 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
888
889 /* There is always only one block per MCU */
890 block = MCU_data[0];
891 tbl = entropy->ac_derived_tbl;
892
893 /* If we are forced to suspend, we must undo the assignments to any newly
894 * nonzero coefficients in the block, because otherwise we'd get confused
895 * next time about which coefficients were already nonzero.
896 * But we need not undo addition of bits to already-nonzero coefficients;
897 * instead, we can test the current bit to see if we already did it.
898 */
899 num_newnz = 0;
900
901 /* initialize coefficient loop counter to start of band */
902 k = cinfo->Ss;
903
904 if (EOBRUN == 0) {
905 for (; k <= Se; k++) {
906 HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
907 r = s >> 4;
908 s &= 15;
909 if (s) {
910 if (s != 1) /* size of new coef should always be 1 */
911 WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
912 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
913 if (GET_BITS(1))
914 s = p1; /* newly nonzero coef is positive */
915 else
916 s = m1; /* newly nonzero coef is negative */
917 } else {
918 if (r != 15) {
919 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */
920 if (r) {
921 CHECK_BIT_BUFFER(br_state, r, goto undoit);
922 r = GET_BITS(r);
923 EOBRUN += r;
924 }
925 break; /* rest of block is handled by EOB logic */
926 }
927 /* note s = 0 for processing ZRL */
928 }
929 /* Advance over already-nonzero coefs and r still-zero coefs,
930 * appending correction bits to the nonzeroes. A correction bit is 1
931 * if the absolute value of the coefficient must be increased.
932 */
933 do {
934 thiscoef = *block + jpeg_natural_order[k];
935 if (*thiscoef != 0) {
936 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
937 if (GET_BITS(1)) {
938 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
939 if (*thiscoef >= 0)
940 *thiscoef += p1;
941 else
942 *thiscoef += m1;
943 }
944 }
945 } else {
946 if (--r < 0)
947 break; /* reached target zero coefficient */
948 }
949 k++;
950 } while (k <= Se);
951 if (s) {
952 int pos = jpeg_natural_order[k];
953 /* Output newly nonzero coefficient */
954 (*block)[pos] = (JCOEF) s;
955 /* Remember its position in case we have to suspend */
956 newnz_pos[num_newnz++] = pos;
957 }
958 }
959 }
960
961 if (EOBRUN > 0) {
962 /* Scan any remaining coefficient positions after the end-of-band
963 * (the last newly nonzero coefficient, if any). Append a correction
964 * bit to each already-nonzero coefficient. A correction bit is 1
965 * if the absolute value of the coefficient must be increased.
966 */
967 for (; k <= Se; k++) {
968 thiscoef = *block + jpeg_natural_order[k];
969 if (*thiscoef != 0) {
970 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
971 if (GET_BITS(1)) {
972 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
973 if (*thiscoef >= 0)
974 *thiscoef += p1;
975 else
976 *thiscoef += m1;
977 }
978 }
979 }
980 }
981 /* Count one block completed in EOB run */
982 EOBRUN--;
983 }
984
985 /* Completed MCU, so update state */
986 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
987 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
988 }
989
990 /* Account for restart interval (no-op if not using restarts) */
991 entropy->restarts_to_go--;
992
993 return TRUE;
994
995 undoit:
996 /* Re-zero any output coefficients that we made newly nonzero */
997 while (num_newnz > 0)
998 (*block)[newnz_pos[--num_newnz]] = 0;
999
1000 return FALSE;
1001 }
1002
1003
1004 /*
1005 * Decode one MCU's worth of Huffman-compressed coefficients.
1006 */
1007
1008 METHODDEF(boolean)
1009 decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
1010 {
1011 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1012 int blkn;
1013 BITREAD_STATE_VARS;
1014 savable_state state;
1015
1016 /* Process restart marker if needed; may have to suspend */
1017 if (cinfo->restart_interval) {
1018 if (entropy->restarts_to_go == 0)
1019 if (! process_restart(cinfo))
1020 return FALSE;
1021 }
1022
1023 /* If we've run out of data, just leave the MCU set to zeroes.
1024 * This way, we return uniform gray for the remainder of the segment.
1025 */
1026 if (! entropy->pub.insufficient_data) {
1027
1028 /* Load up working state */
1029 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
1030 ASSIGN_STATE(state, entropy->saved);
1031
1032 /* Outer loop handles each block in the MCU */
1033
1034 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1035 JBLOCKROW block = MCU_data[blkn];
1036 d_derived_tbl * htbl;
1037 register int s, k, r;
1038 int coef_limit, ci;
1039
1040 /* Decode a single block's worth of coefficients */
1041
1042 /* Section F.2.2.1: decode the DC coefficient difference */
1043 htbl = entropy->dc_cur_tbls[blkn];
1044 HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1045
1046 htbl = entropy->ac_cur_tbls[blkn];
1115 /* Completed MCU, so update state */
1116 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1117 ASSIGN_STATE(entropy->saved, state);
1118 }
1119
1120 /* Account for restart interval (no-op if not using restarts) */
1121 entropy->restarts_to_go--;
1122
1123 return TRUE;
1124 }
1125
1126
1127 /*
1128 * Initialize for a Huffman-compressed scan.
1129 */
1130
1131 METHODDEF(void)
1132 start_pass_huff_decoder (j_decompress_ptr cinfo)
1133 {
1134 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1135 int ci, blkn, dctbl, actbl, i;
1136 jpeg_component_info * compptr;
1137
1138 if (cinfo->progressive_mode) {
1139 /* Validate progressive scan parameters */
1140 if (cinfo->Ss == 0) {
1141 if (cinfo->Se != 0)
1142 goto bad;
1143 } else {
1144 /* need not check Ss/Se < 0 since they came from unsigned bytes */
1145 if (cinfo->Se < cinfo->Ss || cinfo->Se >= DCTSIZE2)
1146 goto bad;
1147 /* AC scans may have only one component */
1148 if (cinfo->comps_in_scan != 1)
1149 goto bad;
1150 }
1151 if (cinfo->Ah != 0) {
1152 /* Successive approximation refinement scan: must have Al = Ah-1. */
1153 if (cinfo->Ah-1 != cinfo->Al)
1154 goto bad;
1155 }
1156 if (cinfo->Al > 13) { /* need not check for < 0 */
1157 /* Arguably the maximum Al value should be less than 13 for 8-bit precision,
1158 * but the spec doesn't say so, and we try to be liberal about what we
1159 * accept. Note: large Al values could result in out-of-range DC
1160 * coefficients during early scans, leading to bizarre displays due to
1161 * overflows in the IDCT math. But we won't crash.
1162 */
1163 bad:
1164 ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
1165 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
1184 /* Select MCU decoding routine */
1185 if (cinfo->Ah == 0) {
1186 if (cinfo->Ss == 0)
1187 entropy->pub.decode_mcu = decode_mcu_DC_first;
1188 else
1189 entropy->pub.decode_mcu = decode_mcu_AC_first;
1190 } else {
1191 if (cinfo->Ss == 0)
1192 entropy->pub.decode_mcu = decode_mcu_DC_refine;
1193 else
1194 entropy->pub.decode_mcu = decode_mcu_AC_refine;
1195 }
1196
1197 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1198 compptr = cinfo->cur_comp_info[ci];
1199 /* Make sure requested tables are present, and compute derived tables.
1200 * We may build same derived table more than once, but it's not expensive.
1201 */
1202 if (cinfo->Ss == 0) {
1203 if (cinfo->Ah == 0) { /* DC refinement needs no table */
1204 i = compptr->dc_tbl_no;
1205 jpeg_make_d_derived_tbl(cinfo, TRUE, i,
1206 & entropy->derived_tbls[i]);
1207 }
1208 } else {
1209 i = compptr->ac_tbl_no;
1210 jpeg_make_d_derived_tbl(cinfo, FALSE, i,
1211 & entropy->derived_tbls[i]);
1212 /* remember the single active table */
1213 entropy->ac_derived_tbl = entropy->derived_tbls[i];
1214 }
1215 /* Initialize DC predictions to 0 */
1216 entropy->saved.last_dc_val[ci] = 0;
1217 }
1218
1219 /* Initialize private state variables */
1220 entropy->saved.EOBRUN = 0;
1221 } else {
1222 /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
1223 * This ought to be an error condition, but we make it a warning because
1224 * there are some baseline files out there with all zeroes in these bytes.
1225 */
1226 if (cinfo->Ss != 0 || cinfo->Se != DCTSIZE2-1 ||
1227 cinfo->Ah != 0 || cinfo->Al != 0)
1228 WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
1229
1230 /* Select MCU decoding routine */
1231 entropy->pub.decode_mcu = decode_mcu;
1232
1233 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1234 compptr = cinfo->cur_comp_info[ci];
1235 dctbl = compptr->dc_tbl_no;
1236 actbl = compptr->ac_tbl_no;
1237 /* Compute derived values for Huffman tables */
1238 /* We may do this more than once for a table, but it's not expensive */
1239 jpeg_make_d_derived_tbl(cinfo, TRUE, dctbl,
1240 & entropy->dc_derived_tbls[dctbl]);
1241 jpeg_make_d_derived_tbl(cinfo, FALSE, actbl,
1242 & entropy->ac_derived_tbls[actbl]);
1243 /* Initialize DC predictions to 0 */
1244 entropy->saved.last_dc_val[ci] = 0;
1245 }
1246
1247 /* Precalculate decoding info for each block in an MCU of this scan */
1248 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1249 ci = cinfo->MCU_membership[blkn];
1250 compptr = cinfo->cur_comp_info[ci];
1251 /* Precalculate which table to use for each block */
1252 entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no];
1253 entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no];
1254 /* Decide whether we really care about the coefficient values */
1255 if (compptr->component_needed) {
1256 ci = compptr->DCT_v_scaled_size;
1257 if (ci <= 0 || ci > 8) ci = 8;
1258 i = compptr->DCT_h_scaled_size;
1259 if (i <= 0 || i > 8) i = 8;
1260 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1];
1261 } else {
1262 entropy->coef_limit[blkn] = 0;
1263 }
1264 }
1265 }
1266
1267 /* Initialize bitread state variables */
1268 entropy->bitstate.bits_left = 0;
1269 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
1270 entropy->pub.insufficient_data = FALSE;
1271
1272 /* Initialize restart counter */
1273 entropy->restarts_to_go = cinfo->restart_interval;
1274 }
1275
1276
1277 /*
1278 * Module initialization routine for Huffman entropy decoding.
1279 */
1280
1281 GLOBAL(void)
1282 jinit_huff_decoder (j_decompress_ptr cinfo)
1283 {
1284 huff_entropy_ptr entropy;
1285 int i;
1286
1287 entropy = (huff_entropy_ptr)
1288 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1289 SIZEOF(huff_entropy_decoder));
1290 cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
1291 entropy->pub.start_pass = start_pass_huff_decoder;
1292
1293 if (cinfo->progressive_mode) {
1294 /* Create progression status table */
1295 int *coef_bit_ptr, ci;
1296 cinfo->coef_bits = (int (*)[DCTSIZE2])
1297 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1298 cinfo->num_components*DCTSIZE2*SIZEOF(int));
1299 coef_bit_ptr = & cinfo->coef_bits[0][0];
1300 for (ci = 0; ci < cinfo->num_components; ci++)
1301 for (i = 0; i < DCTSIZE2; i++)
1302 *coef_bit_ptr++ = -1;
1303
1304 /* Mark derived tables unallocated */
1305 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1306 entropy->derived_tbls[i] = NULL;
1307 }
1308 } else {
1309 /* Mark tables unallocated */
1310 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1311 entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
|
1 /*
2 * jdhuff.c
3 *
4 * Copyright (C) 1991-1997, Thomas G. Lane.
5 * Modified 2006-2016 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
8 *
9 * This file contains Huffman entropy decoding routines.
10 * Both sequential and progressive modes are supported in this single module.
11 *
12 * Much of the complexity here has to do with supporting input suspension.
13 * If the data source module demands suspension, we want to be able to back
14 * up to the start of the current MCU. To do this, we copy state variables
15 * into local working storage, and update them back to the permanent
16 * storage only upon successful completion of an MCU.
17 */
18
19 #define JPEG_INTERNALS
20 #include "jinclude.h"
21 #include "jpeglib.h"
22
23
24 /* Derived data constructed for each Huffman table */
25
212 #define ASSIGN_STATE(dest,src) \
213 ((dest).EOBRUN = (src).EOBRUN, \
214 (dest).last_dc_val[0] = (src).last_dc_val[0], \
215 (dest).last_dc_val[1] = (src).last_dc_val[1], \
216 (dest).last_dc_val[2] = (src).last_dc_val[2], \
217 (dest).last_dc_val[3] = (src).last_dc_val[3])
218 #endif
219 #endif
220
221
222 typedef struct {
223 struct jpeg_entropy_decoder pub; /* public fields */
224
225 /* These fields are loaded into local variables at start of each MCU.
226 * In case of suspension, we exit WITHOUT updating them.
227 */
228 bitread_perm_state bitstate; /* Bit buffer at start of MCU */
229 savable_state saved; /* Other state at start of MCU */
230
231 /* These fields are NOT loaded into local working state. */
232 boolean insufficient_data; /* set TRUE after emitting warning */
233 unsigned int restarts_to_go; /* MCUs left in this restart interval */
234
235 /* Following two fields used only in progressive mode */
236
237 /* Pointers to derived tables (these workspaces have image lifespan) */
238 d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
239
240 d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
241
242 /* Following fields used only in sequential mode */
243
244 /* Pointers to derived tables (these workspaces have image lifespan) */
245 d_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
246 d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
247
248 /* Precalculated info set up by start_pass for use in decode_mcu: */
249
250 /* Pointers to derived tables to be used for each block within an MCU */
251 d_derived_tbl * dc_cur_tbls[D_MAX_BLOCKS_IN_MCU];
252 d_derived_tbl * ac_cur_tbls[D_MAX_BLOCKS_IN_MCU];
253 /* Whether we care about the DC and AC coefficient values for each block */
254 int coef_limit[D_MAX_BLOCKS_IN_MCU];
255 } huff_entropy_decoder;
256
257 typedef huff_entropy_decoder * huff_entropy_ptr;
258
259
260 static const int jpeg_zigzag_order[8][8] = {
261 { 0, 1, 5, 6, 14, 15, 27, 28 },
262 { 2, 4, 7, 13, 16, 26, 29, 42 },
263 { 3, 8, 12, 17, 25, 30, 41, 43 },
264 { 9, 11, 18, 24, 31, 40, 44, 53 },
265 { 10, 19, 23, 32, 39, 45, 52, 54 },
266 { 20, 22, 33, 38, 46, 51, 55, 60 },
267 { 21, 34, 37, 47, 50, 56, 59, 61 },
268 { 35, 36, 48, 49, 57, 58, 62, 63 }
269 };
270
271 static const int jpeg_zigzag_order7[7][7] = {
272 { 0, 1, 5, 6, 14, 15, 27 },
273 { 2, 4, 7, 13, 16, 26, 28 },
274 { 3, 8, 12, 17, 25, 29, 38 },
275 { 9, 11, 18, 24, 30, 37, 39 },
276 { 10, 19, 23, 31, 36, 40, 45 },
277 { 20, 22, 32, 35, 41, 44, 46 },
278 { 21, 33, 34, 42, 43, 47, 48 }
279 };
280
281 static const int jpeg_zigzag_order6[6][6] = {
282 { 0, 1, 5, 6, 14, 15 },
283 { 2, 4, 7, 13, 16, 25 },
284 { 3, 8, 12, 17, 24, 26 },
285 { 9, 11, 18, 23, 27, 32 },
286 { 10, 19, 22, 28, 31, 33 },
287 { 20, 21, 29, 30, 34, 35 }
288 };
289
290 static const int jpeg_zigzag_order5[5][5] = {
291 { 0, 1, 5, 6, 14 },
292 { 2, 4, 7, 13, 15 },
293 { 3, 8, 12, 16, 21 },
294 { 9, 11, 17, 20, 22 },
295 { 10, 18, 19, 23, 24 }
296 };
297
298 static const int jpeg_zigzag_order4[4][4] = {
299 { 0, 1, 5, 6 },
300 { 2, 4, 7, 12 },
301 { 3, 8, 11, 13 },
302 { 9, 10, 14, 15 }
303 };
304
305 static const int jpeg_zigzag_order3[3][3] = {
306 { 0, 1, 5 },
307 { 2, 4, 6 },
308 { 3, 7, 8 }
309 };
310
311 static const int jpeg_zigzag_order2[2][2] = {
312 { 0, 1 },
313 { 2, 3 }
314 };
315
316
317 /*
318 * Compute the derived values for a Huffman table.
319 * This routine also performs some validation checks on the table.
320 */
321
322 LOCAL(void)
323 jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno,
324 d_derived_tbl ** pdtbl)
325 {
326 JHUFF_TBL *htbl;
327 d_derived_tbl *dtbl;
328 int p, i, l, si, numsymbols;
329 int lookbits, ctr;
330 char huffsize[257];
331 unsigned int huffcode[257];
332 unsigned int code;
333
334 /* Note that huffsize[] and huffcode[] are filled in code-length order,
335 * paralleling the order of the symbols themselves in htbl->huffval[].
336 */
337
338 /* Find the input Huffman table */
339 if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
340 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
341 htbl =
342 isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
343 if (htbl == NULL)
344 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
345
346 /* Allocate a workspace if we haven't already done so. */
347 if (*pdtbl == NULL)
348 *pdtbl = (d_derived_tbl *)
349 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
350 SIZEOF(d_derived_tbl));
351 dtbl = *pdtbl;
352 dtbl->pub = htbl; /* fill in back link */
353
525 goto no_more_bytes;
526 }
527 }
528
529 /* OK, load c into get_buffer */
530 get_buffer = (get_buffer << 8) | c;
531 bits_left += 8;
532 } /* end while */
533 } else {
534 no_more_bytes:
535 /* We get here if we've read the marker that terminates the compressed
536 * data segment. There should be enough bits in the buffer register
537 * to satisfy the request; if so, no problem.
538 */
539 if (nbits > bits_left) {
540 /* Uh-oh. Report corrupted data to user and stuff zeroes into
541 * the data stream, so that we can produce some kind of image.
542 * We use a nonvolatile flag to ensure that only one warning message
543 * appears per data segment.
544 */
545 if (! ((huff_entropy_ptr) cinfo->entropy)->insufficient_data) {
546 WARNMS(cinfo, JWRN_HIT_MARKER);
547 ((huff_entropy_ptr) cinfo->entropy)->insufficient_data = TRUE;
548 }
549 /* Fill the buffer with zero bits */
550 get_buffer <<= MIN_GET_BITS - bits_left;
551 bits_left = MIN_GET_BITS;
552 }
553 }
554
555 /* Unload the local registers */
556 state->next_input_byte = next_input_byte;
557 state->bytes_in_buffer = bytes_in_buffer;
558 state->get_buffer = get_buffer;
559 state->bits_left = bits_left;
560
561 return TRUE;
562 }
563
564
565 /*
566 * Figure F.12: extend sign bit.
567 * On some machines, a shift and sub will be faster than a table lookup.
602 CHECK_BIT_BUFFER(*state, l, return -1);
603 code = GET_BITS(l);
604
605 /* Collect the rest of the Huffman code one bit at a time. */
606 /* This is per Figure F.16 in the JPEG spec. */
607
608 while (code > htbl->maxcode[l]) {
609 code <<= 1;
610 CHECK_BIT_BUFFER(*state, 1, return -1);
611 code |= GET_BITS(1);
612 l++;
613 }
614
615 /* Unload the local registers */
616 state->get_buffer = get_buffer;
617 state->bits_left = bits_left;
618
619 /* With garbage input we may reach the sentinel value l = 17. */
620
621 if (l > 16) {
622 WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
623 return 0; /* fake a zero as the safest result */
624 }
625
626 return htbl->pub->huffval[ (int) (code + htbl->valoffset[l]) ];
627 }
628
629
630 /*
631 * Finish up at the end of a Huffman-compressed scan.
632 */
633
634 METHODDEF(void)
635 finish_pass_huff (j_decompress_ptr cinfo)
636 {
637 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
638
639 /* Throw away any unused bits remaining in bit buffer; */
640 /* include any full bytes in next_marker's count of discarded bytes */
641 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
642 entropy->bitstate.bits_left = 0;
643 }
644
645
646 /*
647 * Check for a restart marker & resynchronize decoder.
648 * Returns FALSE if must suspend.
649 */
650
651 LOCAL(boolean)
652 process_restart (j_decompress_ptr cinfo)
653 {
654 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
655 int ci;
656
657 finish_pass_huff(cinfo);
658
659 /* Advance past the RSTn marker */
660 if (! (*cinfo->marker->read_restart_marker) (cinfo))
661 return FALSE;
662
663 /* Re-initialize DC predictions to 0 */
664 for (ci = 0; ci < cinfo->comps_in_scan; ci++)
665 entropy->saved.last_dc_val[ci] = 0;
666 /* Re-init EOB run count, too */
667 entropy->saved.EOBRUN = 0;
668
669 /* Reset restart counter */
670 entropy->restarts_to_go = cinfo->restart_interval;
671
672 /* Reset out-of-data flag, unless read_restart_marker left us smack up
673 * against a marker. In that case we will end up treating the next data
674 * segment as empty, and we can avoid producing bogus output pixels by
675 * leaving the flag set.
676 */
677 if (cinfo->unread_marker == 0)
678 entropy->insufficient_data = FALSE;
679
680 return TRUE;
681 }
682
683
684 /*
685 * Huffman MCU decoding.
686 * Each of these routines decodes and returns one MCU's worth of
687 * Huffman-compressed coefficients.
688 * The coefficients are reordered from zigzag order into natural array order,
689 * but are not dequantized.
690 *
691 * The i'th block of the MCU is stored into the block pointed to by
692 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
693 * (Wholesale zeroing is usually a little faster than retail...)
694 *
695 * We return FALSE if data source requested suspension. In that case no
696 * changes have been made to permanent state. (Exception: some output
697 * coefficients may already have been assigned. This is harmless for
698 * spectral selection, since we'll just re-assign them on the next call.
710 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
711 int Al = cinfo->Al;
712 register int s, r;
713 int blkn, ci;
714 JBLOCKROW block;
715 BITREAD_STATE_VARS;
716 savable_state state;
717 d_derived_tbl * tbl;
718 jpeg_component_info * compptr;
719
720 /* Process restart marker if needed; may have to suspend */
721 if (cinfo->restart_interval) {
722 if (entropy->restarts_to_go == 0)
723 if (! process_restart(cinfo))
724 return FALSE;
725 }
726
727 /* If we've run out of data, just leave the MCU set to zeroes.
728 * This way, we return uniform gray for the remainder of the segment.
729 */
730 if (! entropy->insufficient_data) {
731
732 /* Load up working state */
733 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
734 ASSIGN_STATE(state, entropy->saved);
735
736 /* Outer loop handles each block in the MCU */
737
738 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
739 block = MCU_data[blkn];
740 ci = cinfo->MCU_membership[blkn];
741 compptr = cinfo->cur_comp_info[ci];
742 tbl = entropy->derived_tbls[compptr->dc_tbl_no];
743
744 /* Decode a single block's worth of coefficients */
745
746 /* Section F.2.2.1: decode the DC coefficient difference */
747 HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
748 if (s) {
749 CHECK_BIT_BUFFER(br_state, s, return FALSE);
750 r = GET_BITS(s);
762 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
763 ASSIGN_STATE(entropy->saved, state);
764 }
765
766 /* Account for restart interval (no-op if not using restarts) */
767 entropy->restarts_to_go--;
768
769 return TRUE;
770 }
771
772
773 /*
774 * MCU decoding for AC initial scan (either spectral selection,
775 * or first pass of successive approximation).
776 */
777
778 METHODDEF(boolean)
779 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
780 {
781 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
782 register int s, k, r;
783 unsigned int EOBRUN;
784 int Se, Al;
785 const int * natural_order;
786 JBLOCKROW block;
787 BITREAD_STATE_VARS;
788 d_derived_tbl * tbl;
789
790 /* Process restart marker if needed; may have to suspend */
791 if (cinfo->restart_interval) {
792 if (entropy->restarts_to_go == 0)
793 if (! process_restart(cinfo))
794 return FALSE;
795 }
796
797 /* If we've run out of data, just leave the MCU set to zeroes.
798 * This way, we return uniform gray for the remainder of the segment.
799 */
800 if (! entropy->insufficient_data) {
801
802 /* Load up working state.
803 * We can avoid loading/saving bitread state if in an EOB run.
804 */
805 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
806
807 /* There is always only one block per MCU */
808
809 if (EOBRUN) /* if it's a band of zeroes... */
810 EOBRUN--; /* ...process it now (we do nothing) */
811 else {
812 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
813 Se = cinfo->Se;
814 Al = cinfo->Al;
815 natural_order = cinfo->natural_order;
816 block = MCU_data[0];
817 tbl = entropy->ac_derived_tbl;
818
819 for (k = cinfo->Ss; k <= Se; k++) {
820 HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
821 r = s >> 4;
822 s &= 15;
823 if (s) {
824 k += r;
825 CHECK_BIT_BUFFER(br_state, s, return FALSE);
826 r = GET_BITS(s);
827 s = HUFF_EXTEND(r, s);
828 /* Scale and output coefficient in natural (dezigzagged) order */
829 (*block)[natural_order[k]] = (JCOEF) (s << Al);
830 } else {
831 if (r != 15) { /* EOBr, run length is 2^r + appended bits */
832 if (r) { /* EOBr, r > 0 */
833 EOBRUN = 1 << r;
834 CHECK_BIT_BUFFER(br_state, r, return FALSE);
835 r = GET_BITS(r);
836 EOBRUN += r;
837 EOBRUN--; /* this band is processed at this moment */
838 }
839 break; /* force end-of-band */
840 }
841 k += 15; /* ZRL: skip 15 zeroes in band */
842 }
843 }
844
845 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
846 }
847
848 /* Completed MCU, so update state */
849 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
850 }
851
852 /* Account for restart interval (no-op if not using restarts) */
853 entropy->restarts_to_go--;
854
855 return TRUE;
856 }
857
858
859 /*
860 * MCU decoding for DC successive approximation refinement scan.
861 * Note: we assume such scans can be multi-component,
862 * although the spec is not very clear on the point.
863 */
864
865 METHODDEF(boolean)
866 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
867 {
868 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
869 int p1, blkn;
870 BITREAD_STATE_VARS;
871
872 /* Process restart marker if needed; may have to suspend */
873 if (cinfo->restart_interval) {
874 if (entropy->restarts_to_go == 0)
875 if (! process_restart(cinfo))
876 return FALSE;
877 }
878
879 /* Not worth the cycles to check insufficient_data here,
880 * since we will not change the data anyway if we read zeroes.
881 */
882
883 /* Load up working state */
884 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
885
886 p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
887
888 /* Outer loop handles each block in the MCU */
889
890 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
891 /* Encoded data is simply the next bit of the two's-complement DC value */
892 CHECK_BIT_BUFFER(br_state, 1, return FALSE);
893 if (GET_BITS(1))
894 MCU_data[blkn][0][0] |= p1;
895 /* Note: since we use |=, repeating the assignment later is safe */
896 }
897
898 /* Completed MCU, so update state */
899 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
900
901 /* Account for restart interval (no-op if not using restarts) */
902 entropy->restarts_to_go--;
903
904 return TRUE;
905 }
906
907
908 /*
909 * MCU decoding for AC successive approximation refinement scan.
910 */
911
912 METHODDEF(boolean)
913 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
914 {
915 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
916 register int s, k, r;
917 unsigned int EOBRUN;
918 int Se, p1, m1;
919 const int * natural_order;
920 JBLOCKROW block;
921 JCOEFPTR thiscoef;
922 BITREAD_STATE_VARS;
923 d_derived_tbl * tbl;
924 int num_newnz;
925 int newnz_pos[DCTSIZE2];
926
927 /* Process restart marker if needed; may have to suspend */
928 if (cinfo->restart_interval) {
929 if (entropy->restarts_to_go == 0)
930 if (! process_restart(cinfo))
931 return FALSE;
932 }
933
934 /* If we've run out of data, don't modify the MCU.
935 */
936 if (! entropy->insufficient_data) {
937
938 Se = cinfo->Se;
939 p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
940 m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */
941 natural_order = cinfo->natural_order;
942
943 /* Load up working state */
944 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
945 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
946
947 /* There is always only one block per MCU */
948 block = MCU_data[0];
949 tbl = entropy->ac_derived_tbl;
950
951 /* If we are forced to suspend, we must undo the assignments to any newly
952 * nonzero coefficients in the block, because otherwise we'd get confused
953 * next time about which coefficients were already nonzero.
954 * But we need not undo addition of bits to already-nonzero coefficients;
955 * instead, we can test the current bit to see if we already did it.
956 */
957 num_newnz = 0;
958
959 /* initialize coefficient loop counter to start of band */
960 k = cinfo->Ss;
961
962 if (EOBRUN == 0) {
963 do {
964 HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
965 r = s >> 4;
966 s &= 15;
967 if (s) {
968 if (s != 1) /* size of new coef should always be 1 */
969 WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
970 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
971 if (GET_BITS(1))
972 s = p1; /* newly nonzero coef is positive */
973 else
974 s = m1; /* newly nonzero coef is negative */
975 } else {
976 if (r != 15) {
977 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */
978 if (r) {
979 CHECK_BIT_BUFFER(br_state, r, goto undoit);
980 r = GET_BITS(r);
981 EOBRUN += r;
982 }
983 break; /* rest of block is handled by EOB logic */
984 }
985 /* note s = 0 for processing ZRL */
986 }
987 /* Advance over already-nonzero coefs and r still-zero coefs,
988 * appending correction bits to the nonzeroes. A correction bit is 1
989 * if the absolute value of the coefficient must be increased.
990 */
991 do {
992 thiscoef = *block + natural_order[k];
993 if (*thiscoef) {
994 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
995 if (GET_BITS(1)) {
996 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
997 if (*thiscoef >= 0)
998 *thiscoef += p1;
999 else
1000 *thiscoef += m1;
1001 }
1002 }
1003 } else {
1004 if (--r < 0)
1005 break; /* reached target zero coefficient */
1006 }
1007 k++;
1008 } while (k <= Se);
1009 if (s) {
1010 int pos = natural_order[k];
1011 /* Output newly nonzero coefficient */
1012 (*block)[pos] = (JCOEF) s;
1013 /* Remember its position in case we have to suspend */
1014 newnz_pos[num_newnz++] = pos;
1015 }
1016 k++;
1017 } while (k <= Se);
1018 }
1019
1020 if (EOBRUN) {
1021 /* Scan any remaining coefficient positions after the end-of-band
1022 * (the last newly nonzero coefficient, if any). Append a correction
1023 * bit to each already-nonzero coefficient. A correction bit is 1
1024 * if the absolute value of the coefficient must be increased.
1025 */
1026 do {
1027 thiscoef = *block + natural_order[k];
1028 if (*thiscoef) {
1029 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
1030 if (GET_BITS(1)) {
1031 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
1032 if (*thiscoef >= 0)
1033 *thiscoef += p1;
1034 else
1035 *thiscoef += m1;
1036 }
1037 }
1038 }
1039 k++;
1040 } while (k <= Se);
1041 /* Count one block completed in EOB run */
1042 EOBRUN--;
1043 }
1044
1045 /* Completed MCU, so update state */
1046 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1047 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
1048 }
1049
1050 /* Account for restart interval (no-op if not using restarts) */
1051 entropy->restarts_to_go--;
1052
1053 return TRUE;
1054
1055 undoit:
1056 /* Re-zero any output coefficients that we made newly nonzero */
1057 while (num_newnz)
1058 (*block)[newnz_pos[--num_newnz]] = 0;
1059
1060 return FALSE;
1061 }
1062
1063
1064 /*
1065 * Decode one MCU's worth of Huffman-compressed coefficients,
1066 * partial blocks.
1067 */
1068
1069 METHODDEF(boolean)
1070 decode_mcu_sub (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
1071 {
1072 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1073 const int * natural_order;
1074 int Se, blkn;
1075 BITREAD_STATE_VARS;
1076 savable_state state;
1077
1078 /* Process restart marker if needed; may have to suspend */
1079 if (cinfo->restart_interval) {
1080 if (entropy->restarts_to_go == 0)
1081 if (! process_restart(cinfo))
1082 return FALSE;
1083 }
1084
1085 /* If we've run out of data, just leave the MCU set to zeroes.
1086 * This way, we return uniform gray for the remainder of the segment.
1087 */
1088 if (! entropy->insufficient_data) {
1089
1090 natural_order = cinfo->natural_order;
1091 Se = cinfo->lim_Se;
1092
1093 /* Load up working state */
1094 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
1095 ASSIGN_STATE(state, entropy->saved);
1096
1097 /* Outer loop handles each block in the MCU */
1098
1099 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1100 JBLOCKROW block = MCU_data[blkn];
1101 d_derived_tbl * htbl;
1102 register int s, k, r;
1103 int coef_limit, ci;
1104
1105 /* Decode a single block's worth of coefficients */
1106
1107 /* Section F.2.2.1: decode the DC coefficient difference */
1108 htbl = entropy->dc_cur_tbls[blkn];
1109 HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1110
1111 htbl = entropy->ac_cur_tbls[blkn];
1112 k = 1;
1113 coef_limit = entropy->coef_limit[blkn];
1114 if (coef_limit) {
1115 /* Convert DC difference to actual value, update last_dc_val */
1116 if (s) {
1117 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1118 r = GET_BITS(s);
1119 s = HUFF_EXTEND(r, s);
1120 }
1121 ci = cinfo->MCU_membership[blkn];
1122 s += state.last_dc_val[ci];
1123 state.last_dc_val[ci] = s;
1124 /* Output the DC coefficient */
1125 (*block)[0] = (JCOEF) s;
1126
1127 /* Section F.2.2.2: decode the AC coefficients */
1128 /* Since zeroes are skipped, output area must be cleared beforehand */
1129 for (; k < coef_limit; k++) {
1130 HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
1131
1132 r = s >> 4;
1133 s &= 15;
1134
1135 if (s) {
1136 k += r;
1137 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1138 r = GET_BITS(s);
1139 s = HUFF_EXTEND(r, s);
1140 /* Output coefficient in natural (dezigzagged) order.
1141 * Note: the extra entries in natural_order[] will save us
1142 * if k > Se, which could happen if the data is corrupted.
1143 */
1144 (*block)[natural_order[k]] = (JCOEF) s;
1145 } else {
1146 if (r != 15)
1147 goto EndOfBlock;
1148 k += 15;
1149 }
1150 }
1151 } else {
1152 if (s) {
1153 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1154 DROP_BITS(s);
1155 }
1156 }
1157
1158 /* Section F.2.2.2: decode the AC coefficients */
1159 /* In this path we just discard the values */
1160 for (; k <= Se; k++) {
1161 HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
1162
1163 r = s >> 4;
1164 s &= 15;
1165
1166 if (s) {
1167 k += r;
1168 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1169 DROP_BITS(s);
1170 } else {
1171 if (r != 15)
1172 break;
1173 k += 15;
1174 }
1175 }
1176
1177 EndOfBlock: ;
1178 }
1179
1180 /* Completed MCU, so update state */
1181 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1182 ASSIGN_STATE(entropy->saved, state);
1183 }
1184
1185 /* Account for restart interval (no-op if not using restarts) */
1186 entropy->restarts_to_go--;
1187
1188 return TRUE;
1189 }
1190
1191
1192 /*
1193 * Decode one MCU's worth of Huffman-compressed coefficients,
1194 * full-size blocks.
1195 */
1196
1197 METHODDEF(boolean)
1198 decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
1199 {
1200 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1201 int blkn;
1202 BITREAD_STATE_VARS;
1203 savable_state state;
1204
1205 /* Process restart marker if needed; may have to suspend */
1206 if (cinfo->restart_interval) {
1207 if (entropy->restarts_to_go == 0)
1208 if (! process_restart(cinfo))
1209 return FALSE;
1210 }
1211
1212 /* If we've run out of data, just leave the MCU set to zeroes.
1213 * This way, we return uniform gray for the remainder of the segment.
1214 */
1215 if (! entropy->insufficient_data) {
1216
1217 /* Load up working state */
1218 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
1219 ASSIGN_STATE(state, entropy->saved);
1220
1221 /* Outer loop handles each block in the MCU */
1222
1223 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1224 JBLOCKROW block = MCU_data[blkn];
1225 d_derived_tbl * htbl;
1226 register int s, k, r;
1227 int coef_limit, ci;
1228
1229 /* Decode a single block's worth of coefficients */
1230
1231 /* Section F.2.2.1: decode the DC coefficient difference */
1232 htbl = entropy->dc_cur_tbls[blkn];
1233 HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1234
1235 htbl = entropy->ac_cur_tbls[blkn];
1304 /* Completed MCU, so update state */
1305 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1306 ASSIGN_STATE(entropy->saved, state);
1307 }
1308
1309 /* Account for restart interval (no-op if not using restarts) */
1310 entropy->restarts_to_go--;
1311
1312 return TRUE;
1313 }
1314
1315
1316 /*
1317 * Initialize for a Huffman-compressed scan.
1318 */
1319
1320 METHODDEF(void)
1321 start_pass_huff_decoder (j_decompress_ptr cinfo)
1322 {
1323 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1324 int ci, blkn, tbl, i;
1325 jpeg_component_info * compptr;
1326
1327 if (cinfo->progressive_mode) {
1328 /* Validate progressive scan parameters */
1329 if (cinfo->Ss == 0) {
1330 if (cinfo->Se != 0)
1331 goto bad;
1332 } else {
1333 /* need not check Ss/Se < 0 since they came from unsigned bytes */
1334 if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se)
1335 goto bad;
1336 /* AC scans may have only one component */
1337 if (cinfo->comps_in_scan != 1)
1338 goto bad;
1339 }
1340 if (cinfo->Ah != 0) {
1341 /* Successive approximation refinement scan: must have Al = Ah-1. */
1342 if (cinfo->Ah-1 != cinfo->Al)
1343 goto bad;
1344 }
1345 if (cinfo->Al > 13) { /* need not check for < 0 */
1346 /* Arguably the maximum Al value should be less than 13 for 8-bit precision,
1347 * but the spec doesn't say so, and we try to be liberal about what we
1348 * accept. Note: large Al values could result in out-of-range DC
1349 * coefficients during early scans, leading to bizarre displays due to
1350 * overflows in the IDCT math. But we won't crash.
1351 */
1352 bad:
1353 ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
1354 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
1373 /* Select MCU decoding routine */
1374 if (cinfo->Ah == 0) {
1375 if (cinfo->Ss == 0)
1376 entropy->pub.decode_mcu = decode_mcu_DC_first;
1377 else
1378 entropy->pub.decode_mcu = decode_mcu_AC_first;
1379 } else {
1380 if (cinfo->Ss == 0)
1381 entropy->pub.decode_mcu = decode_mcu_DC_refine;
1382 else
1383 entropy->pub.decode_mcu = decode_mcu_AC_refine;
1384 }
1385
1386 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1387 compptr = cinfo->cur_comp_info[ci];
1388 /* Make sure requested tables are present, and compute derived tables.
1389 * We may build same derived table more than once, but it's not expensive.
1390 */
1391 if (cinfo->Ss == 0) {
1392 if (cinfo->Ah == 0) { /* DC refinement needs no table */
1393 tbl = compptr->dc_tbl_no;
1394 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
1395 & entropy->derived_tbls[tbl]);
1396 }
1397 } else {
1398 tbl = compptr->ac_tbl_no;
1399 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
1400 & entropy->derived_tbls[tbl]);
1401 /* remember the single active table */
1402 entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
1403 }
1404 /* Initialize DC predictions to 0 */
1405 entropy->saved.last_dc_val[ci] = 0;
1406 }
1407
1408 /* Initialize private state variables */
1409 entropy->saved.EOBRUN = 0;
1410 } else {
1411 /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
1412 * This ought to be an error condition, but we make it a warning because
1413 * there are some baseline files out there with all zeroes in these bytes.
1414 */
1415 if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||
1416 ((cinfo->is_baseline || cinfo->Se < DCTSIZE2) &&
1417 cinfo->Se != cinfo->lim_Se))
1418 WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
1419
1420 /* Select MCU decoding routine */
1421 /* We retain the hard-coded case for full-size blocks.
1422 * This is not necessary, but it appears that this version is slightly
1423 * more performant in the given implementation.
1424 * With an improved implementation we would prefer a single optimized
1425 * function.
1426 */
1427 if (cinfo->lim_Se != DCTSIZE2-1)
1428 entropy->pub.decode_mcu = decode_mcu_sub;
1429 else
1430 entropy->pub.decode_mcu = decode_mcu;
1431
1432 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1433 compptr = cinfo->cur_comp_info[ci];
1434 /* Compute derived values for Huffman tables */
1435 /* We may do this more than once for a table, but it's not expensive */
1436 tbl = compptr->dc_tbl_no;
1437 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
1438 & entropy->dc_derived_tbls[tbl]);
1439 if (cinfo->lim_Se) { /* AC needs no table when not present */
1440 tbl = compptr->ac_tbl_no;
1441 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
1442 & entropy->ac_derived_tbls[tbl]);
1443 }
1444 /* Initialize DC predictions to 0 */
1445 entropy->saved.last_dc_val[ci] = 0;
1446 }
1447
1448 /* Precalculate decoding info for each block in an MCU of this scan */
1449 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1450 ci = cinfo->MCU_membership[blkn];
1451 compptr = cinfo->cur_comp_info[ci];
1452 /* Precalculate which table to use for each block */
1453 entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no];
1454 entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no];
1455 /* Decide whether we really care about the coefficient values */
1456 if (compptr->component_needed) {
1457 ci = compptr->DCT_v_scaled_size;
1458 i = compptr->DCT_h_scaled_size;
1459 switch (cinfo->lim_Se) {
1460 case (1*1-1):
1461 entropy->coef_limit[blkn] = 1;
1462 break;
1463 case (2*2-1):
1464 if (ci <= 0 || ci > 2) ci = 2;
1465 if (i <= 0 || i > 2) i = 2;
1466 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order2[ci - 1][i - 1];
1467 break;
1468 case (3*3-1):
1469 if (ci <= 0 || ci > 3) ci = 3;
1470 if (i <= 0 || i > 3) i = 3;
1471 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order3[ci - 1][i - 1];
1472 break;
1473 case (4*4-1):
1474 if (ci <= 0 || ci > 4) ci = 4;
1475 if (i <= 0 || i > 4) i = 4;
1476 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order4[ci - 1][i - 1];
1477 break;
1478 case (5*5-1):
1479 if (ci <= 0 || ci > 5) ci = 5;
1480 if (i <= 0 || i > 5) i = 5;
1481 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order5[ci - 1][i - 1];
1482 break;
1483 case (6*6-1):
1484 if (ci <= 0 || ci > 6) ci = 6;
1485 if (i <= 0 || i > 6) i = 6;
1486 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order6[ci - 1][i - 1];
1487 break;
1488 case (7*7-1):
1489 if (ci <= 0 || ci > 7) ci = 7;
1490 if (i <= 0 || i > 7) i = 7;
1491 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order7[ci - 1][i - 1];
1492 break;
1493 default:
1494 if (ci <= 0 || ci > 8) ci = 8;
1495 if (i <= 0 || i > 8) i = 8;
1496 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1];
1497 break;
1498 }
1499 } else {
1500 entropy->coef_limit[blkn] = 0;
1501 }
1502 }
1503 }
1504
1505 /* Initialize bitread state variables */
1506 entropy->bitstate.bits_left = 0;
1507 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
1508 entropy->insufficient_data = FALSE;
1509
1510 /* Initialize restart counter */
1511 entropy->restarts_to_go = cinfo->restart_interval;
1512 }
1513
1514
1515 /*
1516 * Module initialization routine for Huffman entropy decoding.
1517 */
1518
1519 GLOBAL(void)
1520 jinit_huff_decoder (j_decompress_ptr cinfo)
1521 {
1522 huff_entropy_ptr entropy;
1523 int i;
1524
1525 entropy = (huff_entropy_ptr)
1526 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1527 SIZEOF(huff_entropy_decoder));
1528 cinfo->entropy = &entropy->pub;
1529 entropy->pub.start_pass = start_pass_huff_decoder;
1530 entropy->pub.finish_pass = finish_pass_huff;
1531
1532 if (cinfo->progressive_mode) {
1533 /* Create progression status table */
1534 int *coef_bit_ptr, ci;
1535 cinfo->coef_bits = (int (*)[DCTSIZE2])
1536 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1537 cinfo->num_components*DCTSIZE2*SIZEOF(int));
1538 coef_bit_ptr = & cinfo->coef_bits[0][0];
1539 for (ci = 0; ci < cinfo->num_components; ci++)
1540 for (i = 0; i < DCTSIZE2; i++)
1541 *coef_bit_ptr++ = -1;
1542
1543 /* Mark derived tables unallocated */
1544 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1545 entropy->derived_tbls[i] = NULL;
1546 }
1547 } else {
1548 /* Mark tables unallocated */
1549 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1550 entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
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