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-/*
- * jdarith.c
- *
- * Developed 1997-2011 by Guido Vollbeding.
- * This file is part of the Independent JPEG Group's software.
- * For conditions of distribution and use, see the accompanying README file.
- *
- * This file contains portable arithmetic entropy decoding routines for JPEG
- * (implementing the ISO/IEC IS 10918-1 and CCITT Recommendation ITU-T T.81).
- *
- * Both sequential and progressive modes are supported in this single module.
- *
- * Suspension is not currently supported in this module.
- */
-
-#define JPEG_INTERNALS
-#include "jinclude.h"
-#include "jpeglib.h"
-
-
-/* Expanded entropy decoder object for arithmetic decoding. */
-
-typedef struct {
- struct jpeg_entropy_decoder pub; /* public fields */
-
- INT32 c; /* C register, base of coding interval + input bit buffer */
- INT32 a; /* A register, normalized size of coding interval */
- int ct; /* bit shift counter, # of bits left in bit buffer part of C */
- /* init: ct = -16 */
- /* run: ct = 0..7 */
- /* error: ct = -1 */
- int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
- int dc_context[MAX_COMPS_IN_SCAN]; /* context index for DC conditioning */
-
- unsigned int restarts_to_go; /* MCUs left in this restart interval */
-
- /* Pointers to statistics areas (these workspaces have image lifespan) */
- unsigned char * dc_stats[NUM_ARITH_TBLS];
- unsigned char * ac_stats[NUM_ARITH_TBLS];
-
- /* Statistics bin for coding with fixed probability 0.5 */
- unsigned char fixed_bin[4];
-} arith_entropy_decoder;
-
-typedef arith_entropy_decoder * arith_entropy_ptr;
-
-/* The following two definitions specify the allocation chunk size
- * for the statistics area.
- * According to sections F.1.4.4.1.3 and F.1.4.4.2, we need at least
- * 49 statistics bins for DC, and 245 statistics bins for AC coding.
- *
- * We use a compact representation with 1 byte per statistics bin,
- * thus the numbers directly represent byte sizes.
- * This 1 byte per statistics bin contains the meaning of the MPS
- * (more probable symbol) in the highest bit (mask 0x80), and the
- * index into the probability estimation state machine table
- * in the lower bits (mask 0x7F).
- */
-
-#define DC_STAT_BINS 64
-#define AC_STAT_BINS 256
-
-
-LOCAL(int)
-get_byte (j_decompress_ptr cinfo)
-/* Read next input byte; we do not support suspension in this module. */
-{
- struct jpeg_source_mgr * src = cinfo->src;
-
- if (src->bytes_in_buffer == 0)
- if (! (*src->fill_input_buffer) (cinfo))
- ERREXIT(cinfo, JERR_CANT_SUSPEND);
- src->bytes_in_buffer--;
- return GETJOCTET(*src->next_input_byte++);
-}
-
-
-/*
- * The core arithmetic decoding routine (common in JPEG and JBIG).
- * This needs to go as fast as possible.
- * Machine-dependent optimization facilities
- * are not utilized in this portable implementation.
- * However, this code should be fairly efficient and
- * may be a good base for further optimizations anyway.
- *
- * Return value is 0 or 1 (binary decision).
- *
- * Note: I've changed the handling of the code base & bit
- * buffer register C compared to other implementations
- * based on the standards layout & procedures.
- * While it also contains both the actual base of the
- * coding interval (16 bits) and the next-bits buffer,
- * the cut-point between these two parts is floating
- * (instead of fixed) with the bit shift counter CT.
- * Thus, we also need only one (variable instead of
- * fixed size) shift for the LPS/MPS decision, and
- * we can get away with any renormalization update
- * of C (except for new data insertion, of course).
- *
- * I've also introduced a new scheme for accessing
- * the probability estimation state machine table,
- * derived from Markus Kuhn's JBIG implementation.
- */
-
-LOCAL(int)
-arith_decode (j_decompress_ptr cinfo, unsigned char *st)
-{
- register arith_entropy_ptr e = (arith_entropy_ptr) cinfo->entropy;
- register unsigned char nl, nm;
- register INT32 qe, temp;
- register int sv, data;
-
- /* Renormalization & data input per section D.2.6 */
- while (e->a < 0x8000L) {
- if (--e->ct < 0) {
- /* Need to fetch next data byte */
- if (cinfo->unread_marker)
- data = 0; /* stuff zero data */
- else {
- data = get_byte(cinfo); /* read next input byte */
- if (data == 0xFF) { /* zero stuff or marker code */
- do data = get_byte(cinfo);
- while (data == 0xFF); /* swallow extra 0xFF bytes */
- if (data == 0)
- data = 0xFF; /* discard stuffed zero byte */
- else {
- /* Note: Different from the Huffman decoder, hitting
- * a marker while processing the compressed data
- * segment is legal in arithmetic coding.
- * The convention is to supply zero data
- * then until decoding is complete.
- */
- cinfo->unread_marker = data;
- data = 0;
- }
- }
- }
- e->c = (e->c << 8) | data; /* insert data into C register */
- if ((e->ct += 8) < 0) /* update bit shift counter */
- /* Need more initial bytes */
- if (++e->ct == 0)
- /* Got 2 initial bytes -> re-init A and exit loop */
- e->a = 0x8000L; /* => e->a = 0x10000L after loop exit */
- }
- e->a <<= 1;
- }
-
- /* Fetch values from our compact representation of Table D.3(D.2):
- * Qe values and probability estimation state machine
- */
- sv = *st;
- qe = jpeg_aritab[sv & 0x7F]; /* => Qe_Value */
- nl = qe & 0xFF; qe >>= 8; /* Next_Index_LPS + Switch_MPS */
- nm = qe & 0xFF; qe >>= 8; /* Next_Index_MPS */
-
- /* Decode & estimation procedures per sections D.2.4 & D.2.5 */
- temp = e->a - qe;
- e->a = temp;
- temp <<= e->ct;
- if (e->c >= temp) {
- e->c -= temp;
- /* Conditional LPS (less probable symbol) exchange */
- if (e->a < qe) {
- e->a = qe;
- *st = (sv & 0x80) ^ nm; /* Estimate_after_MPS */
- } else {
- e->a = qe;
- *st = (sv & 0x80) ^ nl; /* Estimate_after_LPS */
- sv ^= 0x80; /* Exchange LPS/MPS */
- }
- } else if (e->a < 0x8000L) {
- /* Conditional MPS (more probable symbol) exchange */
- if (e->a < qe) {
- *st = (sv & 0x80) ^ nl; /* Estimate_after_LPS */
- sv ^= 0x80; /* Exchange LPS/MPS */
- } else {
- *st = (sv & 0x80) ^ nm; /* Estimate_after_MPS */
- }
- }
-
- return sv >> 7;
-}
-
-
-/*
- * Check for a restart marker & resynchronize decoder.
- */
-
-LOCAL(void)
-process_restart (j_decompress_ptr cinfo)
-{
- arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
- int ci;
- jpeg_component_info * compptr;
-
- /* Advance past the RSTn marker */
- if (! (*cinfo->marker->read_restart_marker) (cinfo))
- ERREXIT(cinfo, JERR_CANT_SUSPEND);
-
- /* Re-initialize statistics areas */
- for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
- compptr = cinfo->cur_comp_info[ci];
- if (! cinfo->progressive_mode || (cinfo->Ss == 0 && cinfo->Ah == 0)) {
- MEMZERO(entropy->dc_stats[compptr->dc_tbl_no], DC_STAT_BINS);
- /* Reset DC predictions to 0 */
- entropy->last_dc_val[ci] = 0;
- entropy->dc_context[ci] = 0;
- }
- if ((! cinfo->progressive_mode && cinfo->lim_Se) ||
- (cinfo->progressive_mode && cinfo->Ss)) {
- MEMZERO(entropy->ac_stats[compptr->ac_tbl_no], AC_STAT_BINS);
- }
- }
-
- /* Reset arithmetic decoding variables */
- entropy->c = 0;
- entropy->a = 0;
- entropy->ct = -16; /* force reading 2 initial bytes to fill C */
-
- /* Reset restart counter */
- entropy->restarts_to_go = cinfo->restart_interval;
-}
-
-
-/*
- * Arithmetic MCU decoding.
- * Each of these routines decodes and returns one MCU's worth of
- * arithmetic-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.
- */
-
-/*
- * 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)
-{
- arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
- JBLOCKROW block;
- unsigned char *st;
- int blkn, ci, tbl, sign;
- int v, m;
-
- /* Process restart marker if needed */
- if (cinfo->restart_interval) {
- if (entropy->restarts_to_go == 0)
- process_restart(cinfo);
- entropy->restarts_to_go--;
- }
-
- if (entropy->ct == -1) return TRUE; /* if error do nothing */
-
- /* 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];
- tbl = cinfo->cur_comp_info[ci]->dc_tbl_no;
-
- /* Sections F.2.4.1 & F.1.4.4.1: Decoding of DC coefficients */
-
- /* Table F.4: Point to statistics bin S0 for DC coefficient coding */
- st = entropy->dc_stats[tbl] + entropy->dc_context[ci];
-
- /* Figure F.19: Decode_DC_DIFF */
- if (arith_decode(cinfo, st) == 0)
- entropy->dc_context[ci] = 0;
- else {
- /* Figure F.21: Decoding nonzero value v */
- /* Figure F.22: Decoding the sign of v */
- sign = arith_decode(cinfo, st + 1);
- st += 2; st += sign;
- /* Figure F.23: Decoding the magnitude category of v */
- if ((m = arith_decode(cinfo, st)) != 0) {
- st = entropy->dc_stats[tbl] + 20; /* Table F.4: X1 = 20 */
- while (arith_decode(cinfo, st)) {
- if ((m <<= 1) == 0x8000) {
- WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
- entropy->ct = -1; /* magnitude overflow */
- return TRUE;
- }
- st += 1;
- }
- }
- /* Section F.1.4.4.1.2: Establish dc_context conditioning category */
- if (m < (int) ((1L << cinfo->arith_dc_L[tbl]) >> 1))
- entropy->dc_context[ci] = 0; /* zero diff category */
- else if (m > (int) ((1L << cinfo->arith_dc_U[tbl]) >> 1))
- entropy->dc_context[ci] = 12 + (sign * 4); /* large diff category */
- else
- entropy->dc_context[ci] = 4 + (sign * 4); /* small diff category */
- v = m;
- /* Figure F.24: Decoding the magnitude bit pattern of v */
- st += 14;
- while (m >>= 1)
- if (arith_decode(cinfo, st)) v |= m;
- v += 1; if (sign) v = -v;
- entropy->last_dc_val[ci] += v;
- }
-
- /* Scale and output the DC coefficient (assumes jpeg_natural_order[0]=0) */
- (*block)[0] = (JCOEF) (entropy->last_dc_val[ci] << cinfo->Al);
- }
-
- 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)
-{
- arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
- JBLOCKROW block;
- unsigned char *st;
- int tbl, sign, k;
- int v, m;
- const int * natural_order;
-
- /* Process restart marker if needed */
- if (cinfo->restart_interval) {
- if (entropy->restarts_to_go == 0)
- process_restart(cinfo);
- entropy->restarts_to_go--;
- }
-
- if (entropy->ct == -1) return TRUE; /* if error do nothing */
-
- natural_order = cinfo->natural_order;
-
- /* There is always only one block per MCU */
- block = MCU_data[0];
- tbl = cinfo->cur_comp_info[0]->ac_tbl_no;
-
- /* Sections F.2.4.2 & F.1.4.4.2: Decoding of AC coefficients */
-
- /* Figure F.20: Decode_AC_coefficients */
- for (k = cinfo->Ss; k <= cinfo->Se; k++) {
- st = entropy->ac_stats[tbl] + 3 * (k - 1);
- if (arith_decode(cinfo, st)) break; /* EOB flag */
- while (arith_decode(cinfo, st + 1) == 0) {
- st += 3; k++;
- if (k > cinfo->Se) {
- WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
- entropy->ct = -1; /* spectral overflow */
- return TRUE;
- }
- }
- /* Figure F.21: Decoding nonzero value v */
- /* Figure F.22: Decoding the sign of v */
- sign = arith_decode(cinfo, entropy->fixed_bin);
- st += 2;
- /* Figure F.23: Decoding the magnitude category of v */
- if ((m = arith_decode(cinfo, st)) != 0) {
- if (arith_decode(cinfo, st)) {
- m <<= 1;
- st = entropy->ac_stats[tbl] +
- (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);
- while (arith_decode(cinfo, st)) {
- if ((m <<= 1) == 0x8000) {
- WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
- entropy->ct = -1; /* magnitude overflow */
- return TRUE;
- }
- st += 1;
- }
- }
- }
- v = m;
- /* Figure F.24: Decoding the magnitude bit pattern of v */
- st += 14;
- while (m >>= 1)
- if (arith_decode(cinfo, st)) v |= m;
- v += 1; if (sign) v = -v;
- /* Scale and output coefficient in natural (dezigzagged) order */
- (*block)[natural_order[k]] = (JCOEF) (v << cinfo->Al);
- }
-
- return TRUE;
-}
-
-
-/*
- * MCU decoding for DC successive approximation refinement scan.
- */
-
-METHODDEF(boolean)
-decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
-{
- arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
- unsigned char *st;
- int p1, blkn;
-
- /* Process restart marker if needed */
- if (cinfo->restart_interval) {
- if (entropy->restarts_to_go == 0)
- process_restart(cinfo);
- entropy->restarts_to_go--;
- }
-
- st = entropy->fixed_bin; /* use fixed probability estimation */
- p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
-
- /* Outer loop handles each block in the MCU */
-
- for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
- /* Encoded data is simply the next bit of the two's-complement DC value */
- if (arith_decode(cinfo, st))
- MCU_data[blkn][0][0] |= p1;
- }
-
- return TRUE;
-}
-
-
-/*
- * MCU decoding for AC successive approximation refinement scan.
- */
-
-METHODDEF(boolean)
-decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
-{
- arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
- JBLOCKROW block;
- JCOEFPTR thiscoef;
- unsigned char *st;
- int tbl, k, kex;
- int p1, m1;
- const int * natural_order;
-
- /* Process restart marker if needed */
- if (cinfo->restart_interval) {
- if (entropy->restarts_to_go == 0)
- process_restart(cinfo);
- entropy->restarts_to_go--;
- }
-
- if (entropy->ct == -1) return TRUE; /* if error do nothing */
-
- natural_order = cinfo->natural_order;
-
- /* There is always only one block per MCU */
- block = MCU_data[0];
- tbl = cinfo->cur_comp_info[0]->ac_tbl_no;
-
- p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
- m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */
-
- /* Establish EOBx (previous stage end-of-block) index */
- for (kex = cinfo->Se; kex > 0; kex--)
- if ((*block)[natural_order[kex]]) break;
-
- for (k = cinfo->Ss; k <= cinfo->Se; k++) {
- st = entropy->ac_stats[tbl] + 3 * (k - 1);
- if (k > kex)
- if (arith_decode(cinfo, st)) break; /* EOB flag */
- for (;;) {
- thiscoef = *block + natural_order[k];
- if (*thiscoef) { /* previously nonzero coef */
- if (arith_decode(cinfo, st + 2)) {
- if (*thiscoef < 0)
- *thiscoef += m1;
- else
- *thiscoef += p1;
- }
- break;
- }
- if (arith_decode(cinfo, st + 1)) { /* newly nonzero coef */
- if (arith_decode(cinfo, entropy->fixed_bin))
- *thiscoef = m1;
- else
- *thiscoef = p1;
- break;
- }
- st += 3; k++;
- if (k > cinfo->Se) {
- WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
- entropy->ct = -1; /* spectral overflow */
- return TRUE;
- }
- }
- }
-
- return TRUE;
-}
-
-
-/*
- * Decode one MCU's worth of arithmetic-compressed coefficients.
- */
-
-METHODDEF(boolean)
-decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
-{
- arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
- jpeg_component_info * compptr;
- JBLOCKROW block;
- unsigned char *st;
- int blkn, ci, tbl, sign, k;
- int v, m;
- const int * natural_order;
-
- /* Process restart marker if needed */
- if (cinfo->restart_interval) {
- if (entropy->restarts_to_go == 0)
- process_restart(cinfo);
- entropy->restarts_to_go--;
- }
-
- if (entropy->ct == -1) return TRUE; /* if error do nothing */
-
- natural_order = cinfo->natural_order;
-
- /* 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];
-
- /* Sections F.2.4.1 & F.1.4.4.1: Decoding of DC coefficients */
-
- tbl = compptr->dc_tbl_no;
-
- /* Table F.4: Point to statistics bin S0 for DC coefficient coding */
- st = entropy->dc_stats[tbl] + entropy->dc_context[ci];
-
- /* Figure F.19: Decode_DC_DIFF */
- if (arith_decode(cinfo, st) == 0)
- entropy->dc_context[ci] = 0;
- else {
- /* Figure F.21: Decoding nonzero value v */
- /* Figure F.22: Decoding the sign of v */
- sign = arith_decode(cinfo, st + 1);
- st += 2; st += sign;
- /* Figure F.23: Decoding the magnitude category of v */
- if ((m = arith_decode(cinfo, st)) != 0) {
- st = entropy->dc_stats[tbl] + 20; /* Table F.4: X1 = 20 */
- while (arith_decode(cinfo, st)) {
- if ((m <<= 1) == 0x8000) {
- WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
- entropy->ct = -1; /* magnitude overflow */
- return TRUE;
- }
- st += 1;
- }
- }
- /* Section F.1.4.4.1.2: Establish dc_context conditioning category */
- if (m < (int) ((1L << cinfo->arith_dc_L[tbl]) >> 1))
- entropy->dc_context[ci] = 0; /* zero diff category */
- else if (m > (int) ((1L << cinfo->arith_dc_U[tbl]) >> 1))
- entropy->dc_context[ci] = 12 + (sign * 4); /* large diff category */
- else
- entropy->dc_context[ci] = 4 + (sign * 4); /* small diff category */
- v = m;
- /* Figure F.24: Decoding the magnitude bit pattern of v */
- st += 14;
- while (m >>= 1)
- if (arith_decode(cinfo, st)) v |= m;
- v += 1; if (sign) v = -v;
- entropy->last_dc_val[ci] += v;
- }
-
- (*block)[0] = (JCOEF) entropy->last_dc_val[ci];
-
- /* Sections F.2.4.2 & F.1.4.4.2: Decoding of AC coefficients */
-
- if (cinfo->lim_Se == 0) continue;
- tbl = compptr->ac_tbl_no;
- k = 0;
-
- /* Figure F.20: Decode_AC_coefficients */
- do {
- st = entropy->ac_stats[tbl] + 3 * k;
- if (arith_decode(cinfo, st)) break; /* EOB flag */
- for (;;) {
- k++;
- if (arith_decode(cinfo, st + 1)) break;
- st += 3;
- if (k >= cinfo->lim_Se) {
- WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
- entropy->ct = -1; /* spectral overflow */
- return TRUE;
- }
- }
- /* Figure F.21: Decoding nonzero value v */
- /* Figure F.22: Decoding the sign of v */
- sign = arith_decode(cinfo, entropy->fixed_bin);
- st += 2;
- /* Figure F.23: Decoding the magnitude category of v */
- if ((m = arith_decode(cinfo, st)) != 0) {
- if (arith_decode(cinfo, st)) {
- m <<= 1;
- st = entropy->ac_stats[tbl] +
- (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);
- while (arith_decode(cinfo, st)) {
- if ((m <<= 1) == 0x8000) {
- WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
- entropy->ct = -1; /* magnitude overflow */
- return TRUE;
- }
- st += 1;
- }
- }
- }
- v = m;
- /* Figure F.24: Decoding the magnitude bit pattern of v */
- st += 14;
- while (m >>= 1)
- if (arith_decode(cinfo, st)) v |= m;
- v += 1; if (sign) v = -v;
- (*block)[natural_order[k]] = (JCOEF) v;
- } while (k < cinfo->lim_Se);
- }
-
- return TRUE;
-}
-
-
-/*
- * Initialize for an arithmetic-compressed scan.
- */
-
-METHODDEF(void)
-start_pass (j_decompress_ptr cinfo)
-{
- arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
- int ci, tbl;
- jpeg_component_info * compptr;
-
- if (cinfo->progressive_mode) {
- /* Validate progressive scan parameters */
- if (cinfo->Ss == 0) {
- if (cinfo->Se != 0)
- goto bad;
- } else {
- /* need not check Ss/Se < 0 since they came from unsigned bytes */
- if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se)
- goto bad;
- /* AC scans may have only one component */
- if (cinfo->comps_in_scan != 1)
- goto bad;
- }
- if (cinfo->Ah != 0) {
- /* Successive approximation refinement scan: must have Al = Ah-1. */
- if (cinfo->Ah-1 != cinfo->Al)
- goto bad;
- }
- if (cinfo->Al > 13) { /* need not check for < 0 */
- 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 coefi, cindex = cinfo->cur_comp_info[ci]->component_index;
- int *coef_bit_ptr = & cinfo->coef_bits[cindex][0];
- if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
- WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 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 (cinfo->Ss == 0)
- entropy->pub.decode_mcu = decode_mcu_DC_first;
- else
- entropy->pub.decode_mcu = decode_mcu_AC_first;
- } else {
- if (cinfo->Ss == 0)
- entropy->pub.decode_mcu = decode_mcu_DC_refine;
- else
- entropy->pub.decode_mcu = decode_mcu_AC_refine;
- }
- } else {
- /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
- * This ought to be an error condition, but we make it a warning.
- */
- if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||
- (cinfo->Se < DCTSIZE2 && cinfo->Se != cinfo->lim_Se))
- WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
- /* Select MCU decoding routine */
- entropy->pub.decode_mcu = decode_mcu;
- }
-
- /* Allocate & initialize requested statistics areas */
- for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
- compptr = cinfo->cur_comp_info[ci];
- if (! cinfo->progressive_mode || (cinfo->Ss == 0 && cinfo->Ah == 0)) {
- tbl = compptr->dc_tbl_no;
- if (tbl < 0 || tbl >= NUM_ARITH_TBLS)
- ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl);
- if (entropy->dc_stats[tbl] == NULL)
- entropy->dc_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small)
- ((j_common_ptr) cinfo, JPOOL_IMAGE, DC_STAT_BINS);
- MEMZERO(entropy->dc_stats[tbl], DC_STAT_BINS);
- /* Initialize DC predictions to 0 */
- entropy->last_dc_val[ci] = 0;
- entropy->dc_context[ci] = 0;
- }
- if ((! cinfo->progressive_mode && cinfo->lim_Se) ||
- (cinfo->progressive_mode && cinfo->Ss)) {
- tbl = compptr->ac_tbl_no;
- if (tbl < 0 || tbl >= NUM_ARITH_TBLS)
- ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl);
- if (entropy->ac_stats[tbl] == NULL)
- entropy->ac_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small)
- ((j_common_ptr) cinfo, JPOOL_IMAGE, AC_STAT_BINS);
- MEMZERO(entropy->ac_stats[tbl], AC_STAT_BINS);
- }
- }
-
- /* Initialize arithmetic decoding variables */
- entropy->c = 0;
- entropy->a = 0;
- entropy->ct = -16; /* force reading 2 initial bytes to fill C */
-
- /* Initialize restart counter */
- entropy->restarts_to_go = cinfo->restart_interval;
-}
-
-
-/*
- * Module initialization routine for arithmetic entropy decoding.
- */
-
-GLOBAL(void)
-jinit_arith_decoder (j_decompress_ptr cinfo)
-{
- arith_entropy_ptr entropy;
- int i;
-
- entropy = (arith_entropy_ptr)
- (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
- SIZEOF(arith_entropy_decoder));
- cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
- entropy->pub.start_pass = start_pass;
-
- /* Mark tables unallocated */
- for (i = 0; i < NUM_ARITH_TBLS; i++) {
- entropy->dc_stats[i] = NULL;
- entropy->ac_stats[i] = NULL;
- }
-
- /* Initialize index for fixed probability estimation */
- entropy->fixed_bin[0] = 113;
-
- if (cinfo->progressive_mode) {
- /* Create progression status table */
- int *coef_bit_ptr, ci;
- cinfo->coef_bits = (int (*)[DCTSIZE2])
- (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
- cinfo->num_components*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;
- }
-}
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-19 02:39:20 +0000