/*

* jdphuff.c

*

* This file was part of the Independent JPEG Group's software:

* Copyright (C) 1995-1997, Thomas G. Lane.

* libjpeg-turbo Modifications:

* Copyright (C) 2015-2016, 2018-2022, D. R. Commander.

* For conditions of distribution and use, see the accompanying README.ijg

* file.

*

* This file contains Huffman entropy decoding routines for progressive JPEG.

*

* Much of the complexity here has to do with supporting input suspension.

* If the data source 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

* storage 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 "jdhuff.h" /* Declarations shared with jdhuff.c */

#include <limits.h>

#ifdef D_PROGRESSIVE_SUPPORTED

/*

* Expanded entropy decoder object for progressive Huffman decoding.

*

* The savable_state subrecord contains fields that change within an MCU,

* but must not be updated permanently until we complete the MCU.

*/

typedef struct {

unsigned int EOBRUN; /* remaining EOBs in EOBRUN */

int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */

} savable_state;

typedef struct {

struct jpeg_entropy_decoder pub; /* public fields */

/* These fields are loaded into local variables at start of each MCU.

* In case of suspension, we exit WITHOUT updating them.

*/

bitread_perm_state bitstate; /* Bit buffer at start of MCU */

savable_state saved; /* Other 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 */

/* Pointers to derived tables (these workspaces have image lifespan) */

d_derived_tbl *derived_tbls[NUM_HUFF_TBLS];

d_derived_tbl *ac_derived_tbl; /* active table during an AC scan */

} phuff_entropy_decoder;

typedef phuff_entropy_decoder *phuff_entropy_ptr;

/* Forward declarations */

METHODDEF(boolean) decode_mcu_DC_first(j_decompress_ptr cinfo,

JBLOCKROW *MCU_data);

METHODDEF(boolean) decode_mcu_AC_first(j_decompress_ptr cinfo,

JBLOCKROW *MCU_data);

METHODDEF(boolean) decode_mcu_DC_refine(j_decompress_ptr cinfo,

JBLOCKROW *MCU_data);

METHODDEF(boolean) decode_mcu_AC_refine(j_decompress_ptr cinfo,

JBLOCKROW *MCU_data);

/*

* Initialize for a Huffman-compressed scan.

*/

METHODDEF(void)

start_pass_phuff_decoder(j_decompress_ptr cinfo)

{

phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;

boolean is_DC_band, bad;

int ci, coefi, tbl;

d_derived_tbl **pdtbl;

int *coef_bit_ptr, *prev_coef_bit_ptr;

jpeg_component_info *compptr;

is_DC_band = (cinfo->Ss == 0);

/* Validate scan parameters */

bad = FALSE;

if (is_DC_band) {

if (cinfo->Se != 0)

bad = TRUE;

} else {

/* need not check Ss/Se < 0 since they came from unsigned bytes */

if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2)

bad = TRUE;

/* AC scans may have only one component */

if (cinfo->comps_in_scan != 1)

bad = TRUE;

}

if (cinfo->Ah != 0) {

/* Successive approximation refinement scan: must have Al = Ah-1. */

if (cinfo->Al != cinfo->Ah - 1)

bad = TRUE;

}

if (cinfo->Al > 13) /* need not check for < 0 */

bad = TRUE;

/* Arguably the maximum Al value should be less than 13 for 8-bit precision,

* but the spec doesn't say so, and we try to be liberal about what we

* accept. Note: large Al values could result in out-of-range DC

* coefficients during early scans, leading to bizarre displays due to

* overflows in the IDCT math. But we won't crash.

*/

if (bad)

ERREXIT4(cinfo, JERR_BAD_PROGRESSION,

cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);

/* Update progression status, and verify that scan order is legal.

* Note that inter-scan inconsistencies are treated as warnings

* not fatal errors ... not clear if this is right way to behave.

*/

for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

int cindex = cinfo->cur_comp_info[ci]->component_index;

coef_bit_ptr = &cinfo->coef_bits[cindex][0];

prev_coef_bit_ptr = &cinfo->coef_bits[cindex + cinfo->num_components][0];

if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */

WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);

for (coefi = MIN(cinfo->Ss, 1); coefi <= MAX(cinfo->Se, 9); coefi++) {

if (cinfo->input_scan_number > 1)

prev_coef_bit_ptr[coefi] = coef_bit_ptr[coefi];

else

prev_coef_bit_ptr[coefi] = 0;

}

for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {

int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];

if (cinfo->Ah != expected)

WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);

coef_bit_ptr[coefi] = cinfo->Al;

}

}

/* Select MCU decoding routine */

if (cinfo->Ah == 0) {

if (is_DC_band)

entropy->pub.decode_mcu = decode_mcu_DC_first;

else

entropy->pub.decode_mcu = decode_mcu_AC_first;

} else {

if (is_DC_band)

entropy->pub.decode_mcu = decode_mcu_DC_refine;

else

entropy->pub.decode_mcu = decode_mcu_AC_refine;

}

for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

compptr = cinfo->cur_comp_info[ci];

/* Make sure requested tables are present, and compute derived tables.

* We may build same derived table more than once, but it's not expensive.

*/

if (is_DC_band) {

if (cinfo->Ah == 0) { /* DC refinement needs no table */

tbl = compptr->dc_tbl_no;

pdtbl = (d_derived_tbl **)(entropy->derived_tbls) + tbl;

jpeg_make_d_derived_tbl(cinfo, TRUE, tbl, pdtbl);

}

} else {

tbl = compptr->ac_tbl_no;

pdtbl = (d_derived_tbl **)(entropy->derived_tbls) + tbl;

jpeg_make_d_derived_tbl(cinfo, FALSE, tbl, pdtbl);

/* remember the single active table */

entropy->ac_derived_tbl = entropy->derived_tbls[tbl];

}

/* Initialize DC predictions to 0 */

entropy->saved.last_dc_val[ci] = 0;

}

/* Initialize bitread state variables */

entropy->bitstate.bits_left = 0;

entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */

entropy->pub.insufficient_data = FALSE;

/* Initialize private state variables */

entropy->saved.EOBRUN = 0;

/* Initialize restart counter */

entropy->restarts_to_go = cinfo->restart_interval;

}

/*

* Figure F.12: extend sign bit.

* On some machines, a shift and add will be faster than a table lookup.

*/

#define AVOID_TABLES

#ifdef AVOID_TABLES

#define NEG_1 ((unsigned)-1)

#define HUFF_EXTEND(x, s) \

((x) < (1 << ((s) - 1)) ? (x) + (((NEG_1) << (s)) + 1) : (x))

#else

#define HUFF_EXTEND(x, s) \

((x) < extend_test[s] ? (x) + extend_offset[s] : (x))

static const int extend_test[16] = { /* entry n is 2**(n-1) */

0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,

0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000

};

static const int extend_offset[16] = { /* entry n is (-1 << n) + 1 */

0, ((-1) << 1) + 1, ((-1) << 2) + 1, ((-1) << 3) + 1, ((-1) << 4) + 1,

((-1) << 5) + 1, ((-1) << 6) + 1, ((-1) << 7) + 1, ((-1) << 8) + 1,

((-1) << 9) + 1, ((-1) << 10) + 1, ((-1) << 11) + 1, ((-1) << 12) + 1,

((-1) << 13) + 1, ((-1) << 14) + 1, ((-1) << 15) + 1

};

#endif /* AVOID_TABLES */

/*

* Check for a restart marker & resynchronize decoder.

* Returns FALSE if must suspend.

*/

LOCAL(boolean)

process_restart(j_decompress_ptr cinfo)

{

phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;

int ci;

/* Throw away any unused bits remaining in bit buffer; */

/* include any full bytes in next_marker's count of discarded bytes */

cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;

entropy->bitstate.bits_left = 0;

/* Advance past the RSTn marker */

if (!(*cinfo->marker->read_restart_marker) (cinfo))

return FALSE;

/* Re-initialize DC predictions to 0 */

for (ci = 0; ci < cinfo->comps_in_scan; ci++)

entropy->saved.last_dc_val[ci] = 0;

/* Re-init EOB run count, too */

entropy->saved.EOBRUN = 0;

/* Reset restart counter */

entropy->restarts_to_go = cinfo->restart_interval;

/* Reset out-of-data flag, unless read_restart_marker left us smack up

* against a marker. In that case we will end up treating the next data

* segment as empty, and we can avoid producing bogus output pixels by

* leaving the flag set.

*/

if (cinfo->unread_marker == 0)

entropy->pub.insufficient_data = FALSE;

return TRUE;

}

/*

* Huffman MCU decoding.

* Each of these routines decodes and returns one MCU's worth of

* Huffman-compressed coefficients.

* The coefficients are reordered from zigzag order into natural array order,

* but are not dequantized.

*

* The i'th block of the MCU is stored into the block pointed to by

* MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.

*

* We return FALSE if data source requested suspension. In that case no

* changes have been made to permanent state. (Exception: some output

* coefficients may already have been assigned. This is harmless for

* spectral selection, since we'll just re-assign them on the next call.

* Successive approximation AC refinement has to be more careful, however.)

*/

/*

* MCU decoding for DC initial scan (either spectral selection,

* or first pass of successive approximation).

*/

METHODDEF(boolean)

decode_mcu_DC_first(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

{

phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;

int Al = cinfo->Al;

register int s, r;

int blkn, ci;

JBLOCKROW block;

BITREAD_STATE_VARS;

savable_state state;

d_derived_tbl *tbl;

jpeg_component_info *compptr;

/* Process restart marker if needed; may have to suspend */

if (cinfo->restart_interval) {

if (entropy->restarts_to_go == 0)

if (!process_restart(cinfo))

return FALSE;

}

/* If we've run out of data, just leave the MCU set to zeroes.

* This way, we return uniform gray for the remainder of the segment.

*/

if (!entropy->pub.insufficient_data) {

/* Load up working state */

BITREAD_LOAD_STATE(cinfo, entropy->bitstate);

state = entropy->saved;

/* Outer loop handles each block in the MCU */

for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {

block = MCU_data[blkn];

ci = cinfo->MCU_membership[blkn];

compptr = cinfo->cur_comp_info[ci];

tbl = entropy->derived_tbls[compptr->dc_tbl_no];

/* Decode a single block's worth of coefficients */

/* Section F.2.2.1: decode the DC coefficient difference */

HUFF_DECODE(s, br_state, tbl, return FALSE, label1);

if (s) {

CHECK_BIT_BUFFER(br_state, s, return FALSE);

r = GET_BITS(s);

s = HUFF_EXTEND(r, s);

}

/* Convert DC difference to actual value, update last_dc_val */

if ((state.last_dc_val[ci] >= 0 &&

s > INT_MAX - state.last_dc_val[ci]) ||

(state.last_dc_val[ci] < 0 && s < INT_MIN - state.last_dc_val[ci]))

ERREXIT(cinfo, JERR_BAD_DCT_COEF);

s += state.last_dc_val[ci];

state.last_dc_val[ci] = s;

/* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */

(*block)[0] = (JCOEF)LEFT_SHIFT(s, Al);

}

/* Completed MCU, so update state */

BITREAD_SAVE_STATE(cinfo, entropy->bitstate);

entropy->saved = state;

}

/* Account for restart interval (no-op if not using restarts) */

if (cinfo->restart_interval)

entropy->restarts_to_go--;

return TRUE;

}

/*

* MCU decoding for AC initial scan (either spectral selection,

* or first pass of successive approximation).

*/

METHODDEF(boolean)

decode_mcu_AC_first(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

{

phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;

int Se = cinfo->Se;

int Al = cinfo->Al;

register int s, k, r;

unsigned int EOBRUN;

JBLOCKROW block;

BITREAD_STATE_VARS;

d_derived_tbl *tbl;

/* Process restart marker if needed; may have to suspend */

if (cinfo->restart_interval) {

if (entropy->restarts_to_go == 0)

if (!process_restart(cinfo))

return FALSE;

}

/* If we've run out of data, just leave the MCU set to zeroes.

* This way, we return uniform gray for the remainder of the segment.

*/

if (!entropy->pub.insufficient_data) {

/* Load up working state.

* We can avoid loading/saving bitread state if in an EOB run.

*/

EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */

/* There is always only one block per MCU */

if (EOBRUN > 0) /* if it's a band of zeroes... */

EOBRUN--; /* ...process it now (we do nothing) */

else {

BITREAD_LOAD_STATE(cinfo, entropy->bitstate);

block = MCU_data[0];

tbl = entropy->ac_derived_tbl;

for (k = cinfo->Ss; k <= Se; k++) {

HUFF_DECODE(s, br_state, tbl, return FALSE, label2);

r = s >> 4;

s &= 15;

if (s) {

k += r;

CHECK_BIT_BUFFER(br_state, s, return FALSE);

r = GET_BITS(s);

s = HUFF_EXTEND(r, s);

/* Scale and output coefficient in natural (dezigzagged) order */

(*block)[jpeg_natural_order[k]] = (JCOEF)LEFT_SHIFT(s, Al);

} else {

if (r == 15) { /* ZRL */

k += 15; /* skip 15 zeroes in band */

} else { /* EOBr, run length is 2^r + appended bits */

EOBRUN = 1 << r;

if (r) { /* EOBr, r > 0 */

CHECK_BIT_BUFFER(br_state, r, return FALSE);

r = GET_BITS(r);

EOBRUN += r;

}

EOBRUN--; /* this band is processed at this moment */

break; /* force end-of-band */

}

}

}

BITREAD_SAVE_STATE(cinfo, entropy->bitstate);

}

/* Completed MCU, so update state */

entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */

}

/* Account for restart interval (no-op if not using restarts) */

if (cinfo->restart_interval)

entropy->restarts_to_go--;

return TRUE;

}

/*

* MCU decoding for DC successive approximation refinement scan.

* Note: we assume such scans can be multi-component, although the spec

* is not very clear on the point.

*/

METHODDEF(boolean)

decode_mcu_DC_refine(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

{

phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;

int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */

int blkn;

JBLOCKROW block;

BITREAD_STATE_VARS;

/* Process restart marker if needed; may have to suspend */

if (cinfo->restart_interval) {

if (entropy->restarts_to_go == 0)

if (!process_restart(cinfo))

return FALSE;

}

/* Not worth the cycles to check insufficient_data here,

* since we will not change the data anyway if we read zeroes.

*/

/* Load up working state */

BITREAD_LOAD_STATE(cinfo, entropy->bitstate);

/* Outer loop handles each block in the MCU */

for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {

block = MCU_data[blkn];

/* Encoded data is simply the next bit of the two's-complement DC value */

CHECK_BIT_BUFFER(br_state, 1, return FALSE);

if (GET_BITS(1))

(*block)[0] |= p1;

/* Note: since we use |=, repeating the assignment later is safe */

}

/* Completed MCU, so update state */

BITREAD_SAVE_STATE(cinfo, entropy->bitstate);

/* Account for restart interval (no-op if not using restarts) */

if (cinfo->restart_interval)

entropy->restarts_to_go--;

return TRUE;

}

/*

* MCU decoding for AC successive approximation refinement scan.

*/

METHODDEF(boolean)

decode_mcu_AC_refine(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

{

phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;

int Se = cinfo->Se;

int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */

int m1 = (NEG_1) << cinfo->Al; /* -1 in the bit position being coded */

register int s, k, r;

unsigned int EOBRUN;

JBLOCKROW block;

JCOEFPTR thiscoef;

BITREAD_STATE_VARS;

d_derived_tbl *tbl;

int num_newnz;

int newnz_pos[DCTSIZE2];

/* Process restart marker if needed; may have to suspend */

if (cinfo->restart_interval) {

if (entropy->restarts_to_go == 0)

if (!process_restart(cinfo))

return FALSE;

}

/* If we've run out of data, don't modify the MCU.

*/

if (!entropy->pub.insufficient_data) {

/* Load up working state */

BITREAD_LOAD_STATE(cinfo, entropy->bitstate);

EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */

/* There is always only one block per MCU */

block = MCU_data[0];

tbl = entropy->ac_derived_tbl;

/* If we are forced to suspend, we must undo the assignments to any newly

* nonzero coefficients in the block, because otherwise we'd get confused

* next time about which coefficients were already nonzero.

* But we need not undo addition of bits to already-nonzero coefficients;

* instead, we can test the current bit to see if we already did it.

*/

num_newnz = 0;

/* initialize coefficient loop counter to start of band */

k = cinfo->Ss;

if (EOBRUN == 0) {

for (; k <= Se; k++) {

HUFF_DECODE(s, br_state, tbl, goto undoit, label3);

r = s >> 4;

s &= 15;

if (s) {

if (s != 1) /* size of new coef should always be 1 */

WARNMS(cinfo, JWRN_HUFF_BAD_CODE);

CHECK_BIT_BUFFER(br_state, 1, goto undoit);

if (GET_BITS(1))

s = p1; /* newly nonzero coef is positive */

else

s = m1; /* newly nonzero coef is negative */

} else {

if (r != 15) {

EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */

if (r) {

CHECK_BIT_BUFFER(br_state, r, goto undoit);

r = GET_BITS(r);

EOBRUN += r;

}

break; /* rest of block is handled by EOB logic */

}

/* note s = 0 for processing ZRL */

}

/* Advance over already-nonzero coefs and r still-zero coefs,

* appending correction bits to the nonzeroes. A correction bit is 1

* if the absolute value of the coefficient must be increased.

*/

do {

thiscoef = *block + jpeg_natural_order[k];

if (*thiscoef != 0) {

CHECK_BIT_BUFFER(br_state, 1, goto undoit);

if (GET_BITS(1)) {

if ((*thiscoef & p1) == 0) { /* do nothing if already set it */

if (*thiscoef >= 0)

*thiscoef += (JCOEF)p1;

else

*thiscoef += (JCOEF)m1;

}

}

} else {

if (--r < 0)

break; /* reached target zero coefficient */

}

k++;

} while (k <= Se);

if (s) {

int pos = jpeg_natural_order[k];

/* Output newly nonzero coefficient */

(*block)[pos] = (JCOEF)s;

/* Remember its position in case we have to suspend */

newnz_pos[num_newnz++] = pos;

}

}

}

if (EOBRUN > 0) {

/* Scan any remaining coefficient positions after the end-of-band

* (the last newly nonzero coefficient, if any). Append a correction

* bit to each already-nonzero coefficient. A correction bit is 1

* if the absolute value of the coefficient must be increased.

*/

for (; k <= Se; k++) {

thiscoef = *block + jpeg_natural_order[k];

if (*thiscoef != 0) {

CHECK_BIT_BUFFER(br_state, 1, goto undoit);

if (GET_BITS(1)) {

if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */

if (*thiscoef >= 0)

*thiscoef += (JCOEF)p1;

else

*thiscoef += (JCOEF)m1;

}

}

}

}

/* Count one block completed in EOB run */

EOBRUN--;

}

/* Completed MCU, so update state */

BITREAD_SAVE_STATE(cinfo, entropy->bitstate);

entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */

}

/* Account for restart interval (no-op if not using restarts) */

if (cinfo->restart_interval)

entropy->restarts_to_go--;

return TRUE;

undoit:

/* Re-zero any output coefficients that we made newly nonzero */

while (num_newnz > 0)

(*block)[newnz_pos[--num_newnz]] = 0;

return FALSE;

}

/*

* Module initialization routine for progressive Huffman entropy decoding.

*/

GLOBAL(void)

jinit_phuff_decoder(j_decompress_ptr cinfo)

{

phuff_entropy_ptr entropy;

int *coef_bit_ptr;

int ci, i;

entropy = (phuff_entropy_ptr)

(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,

sizeof(phuff_entropy_decoder));

cinfo->entropy = (struct jpeg_entropy_decoder *)entropy;

entropy->pub.start_pass = start_pass_phuff_decoder;

/* Mark derived tables unallocated */

for (i = 0; i < NUM_HUFF_TBLS; i++) {

entropy->derived_tbls[i] = NULL;

}

/* Create progression status table */

cinfo->coef_bits = (int (*)[DCTSIZE2])

(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,

cinfo->num_components * 2 * DCTSIZE2 *

sizeof(int));

coef_bit_ptr = &cinfo->coef_bits[0][0];

for (ci = 0; ci < cinfo->num_components; ci++)

for (i = 0; i < DCTSIZE2; i++)

*coef_bit_ptr++ = -1;

}

#endif /* D_PROGRESSIVE_SUPPORTED */