| /* |
| * jdphuff.c |
| * |
| * This file was part of the Independent JPEG Group's software: |
| * Copyright (C) 1995-1997, Thomas G. Lane. |
| * Lossless JPEG Modifications: |
| * Copyright (C) 1999, Ken Murchison. |
| * 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 jd*huff.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 */ |