+++ /dev/null
-/*
- * jdhuff.c
- *
- * Copyright (C) 1991-1995, Thomas G. Lane.
- * 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 Huffman entropy decoding routines.
- *
- * 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.
- */
-
-#define JPEG_INTERNALS
-#include "jinclude.h"
-#include "radiant_jpeglib.h"
-#include "jdhuff.h" /* Declarations shared with jdphuff.c */
-
-
-/*
- * Expanded entropy decoder object for 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 {
- int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
-} savable_state;
-
-/* This macro is to work around compilers with missing or broken
- * structure assignment. You'll need to fix this code if you have
- * such a compiler and you change MAX_COMPS_IN_SCAN.
- */
-
-#ifndef NO_STRUCT_ASSIGN
-#define ASSIGN_STATE(dest,src) ((dest) = (src))
-#else
-#if MAX_COMPS_IN_SCAN == 4
-#define ASSIGN_STATE(dest,src) \
- ((dest).last_dc_val[0] = (src).last_dc_val[0], \
- (dest).last_dc_val[1] = (src).last_dc_val[1], \
- (dest).last_dc_val[2] = (src).last_dc_val[2], \
- (dest).last_dc_val[3] = (src).last_dc_val[3])
-#endif
-#endif
-
-
-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 * dc_derived_tbls[NUM_HUFF_TBLS];
- d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
-} huff_entropy_decoder;
-
-typedef huff_entropy_decoder * huff_entropy_ptr;
-
-
-/*
- * Initialize for a Huffman-compressed scan.
- */
-
-METHODDEF void
-start_pass_huff_decoder (j_decompress_ptr cinfo)
-{
- huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
- int ci, dctbl, actbl;
- jpeg_component_info * compptr;
-
- /* 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 because
- * there are some baseline files out there with all zeroes in these bytes.
- */
- if (cinfo->Ss != 0 || cinfo->Se != DCTSIZE2-1 ||
- cinfo->Ah != 0 || cinfo->Al != 0)
- WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
-
- for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
- compptr = cinfo->cur_comp_info[ci];
- dctbl = compptr->dc_tbl_no;
- actbl = compptr->ac_tbl_no;
- /* Make sure requested tables are present */
- if (dctbl < 0 || dctbl >= NUM_HUFF_TBLS ||
- cinfo->dc_huff_tbl_ptrs[dctbl] == NULL)
- ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, dctbl);
- if (actbl < 0 || actbl >= NUM_HUFF_TBLS ||
- cinfo->ac_huff_tbl_ptrs[actbl] == NULL)
- ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, actbl);
- /* Compute derived values for Huffman tables */
- /* We may do this more than once for a table, but it's not expensive */
- jpeg_make_d_derived_tbl(cinfo, cinfo->dc_huff_tbl_ptrs[dctbl],
- & entropy->dc_derived_tbls[dctbl]);
- jpeg_make_d_derived_tbl(cinfo, cinfo->ac_huff_tbl_ptrs[actbl],
- & entropy->ac_derived_tbls[actbl]);
- /* 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->bitstate.printed_eod = FALSE;
-
- /* Initialize restart counter */
- entropy->restarts_to_go = cinfo->restart_interval;
-}
-
-
-/*
- * Compute the derived values for a Huffman table.
- * Note this is also used by jdphuff.c.
- */
-
-GLOBAL void
-jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, JHUFF_TBL * htbl,
- d_derived_tbl ** pdtbl)
-{
- d_derived_tbl *dtbl;
- int p, i, l, si;
- int lookbits, ctr;
- char huffsize[257];
- unsigned int huffcode[257];
- unsigned int code;
-
- /* Allocate a workspace if we haven't already done so. */
- if (*pdtbl == NULL)
- *pdtbl = (d_derived_tbl *)
- (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
- SIZEOF(d_derived_tbl));
- dtbl = *pdtbl;
- dtbl->pub = htbl; /* fill in back link */
-
- /* Figure C.1: make table of Huffman code length for each symbol */
- /* Note that this is in code-length order. */
-
- p = 0;
- for (l = 1; l <= 16; l++) {
- for (i = 1; i <= (int) htbl->bits[l]; i++)
- huffsize[p++] = (char) l;
- }
- huffsize[p] = 0;
-
- /* Figure C.2: generate the codes themselves */
- /* Note that this is in code-length order. */
-
- code = 0;
- si = huffsize[0];
- p = 0;
- while (huffsize[p]) {
- while (((int) huffsize[p]) == si) {
- huffcode[p++] = code;
- code++;
- }
- code <<= 1;
- si++;
- }
-
- /* Figure F.15: generate decoding tables for bit-sequential decoding */
-
- p = 0;
- for (l = 1; l <= 16; l++) {
- if (htbl->bits[l]) {
- dtbl->valptr[l] = p; /* huffval[] index of 1st symbol of code length l */
- dtbl->mincode[l] = huffcode[p]; /* minimum code of length l */
- p += htbl->bits[l];
- dtbl->maxcode[l] = huffcode[p-1]; /* maximum code of length l */
- } else {
- dtbl->maxcode[l] = -1; /* -1 if no codes of this length */
- }
- }
- dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */
-
- /* Compute lookahead tables to speed up decoding.
- * First we set all the table entries to 0, indicating "too long";
- * then we iterate through the Huffman codes that are short enough and
- * fill in all the entries that correspond to bit sequences starting
- * with that code.
- */
-
- MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits));
-
- p = 0;
- for (l = 1; l <= HUFF_LOOKAHEAD; l++) {
- for (i = 1; i <= (int) htbl->bits[l]; i++, p++) {
- /* l = current code's length, p = its index in huffcode[] & huffval[]. */
- /* Generate left-justified code followed by all possible bit sequences */
- lookbits = huffcode[p] << (HUFF_LOOKAHEAD-l);
- for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) {
- dtbl->look_nbits[lookbits] = l;
- dtbl->look_sym[lookbits] = htbl->huffval[p];
- lookbits++;
- }
- }
- }
-}
-
-
-/*
- * Out-of-line code for bit fetching (shared with jdphuff.c).
- * See jdhuff.h for info about usage.
- * Note: current values of get_buffer and bits_left are passed as parameters,
- * but are returned in the corresponding fields of the state struct.
- *
- * On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width
- * of get_buffer to be used. (On machines with wider words, an even larger
- * buffer could be used.) However, on some machines 32-bit shifts are
- * quite slow and take time proportional to the number of places shifted.
- * (This is true with most PC compilers, for instance.) In this case it may
- * be a win to set MIN_GET_BITS to the minimum value of 15. This reduces the
- * average shift distance at the cost of more calls to jpeg_fill_bit_buffer.
- */
-
-#ifdef SLOW_SHIFT_32
-#define MIN_GET_BITS 15 /* minimum allowable value */
-#else
-#define MIN_GET_BITS (BIT_BUF_SIZE-7)
-#endif
-
-
-GLOBAL boolean
-jpeg_fill_bit_buffer (bitread_working_state * state,
- register bit_buf_type get_buffer, register int bits_left,
- int nbits)
-/* Load up the bit buffer to a depth of at least nbits */
-{
- /* Copy heavily used state fields into locals (hopefully registers) */
- register const JOCTET * next_input_byte = state->next_input_byte;
- register size_t bytes_in_buffer = state->bytes_in_buffer;
- register int c;
-
- /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */
- /* (It is assumed that no request will be for more than that many bits.) */
-
- while (bits_left < MIN_GET_BITS) {
- /* Attempt to read a byte */
- if (state->unread_marker != 0)
- goto no_more_data; /* can't advance past a marker */
-
- if (bytes_in_buffer == 0) {
- if (! (*state->cinfo->src->fill_input_buffer) (state->cinfo))
- return FALSE;
- next_input_byte = state->cinfo->src->next_input_byte;
- bytes_in_buffer = state->cinfo->src->bytes_in_buffer;
- }
- bytes_in_buffer--;
- c = GETJOCTET(*next_input_byte++);
-
- /* If it's 0xFF, check and discard stuffed zero byte */
- if (c == 0xFF) {
- do {
- if (bytes_in_buffer == 0) {
- if (! (*state->cinfo->src->fill_input_buffer) (state->cinfo))
- return FALSE;
- next_input_byte = state->cinfo->src->next_input_byte;
- bytes_in_buffer = state->cinfo->src->bytes_in_buffer;
- }
- bytes_in_buffer--;
- c = GETJOCTET(*next_input_byte++);
- } while (c == 0xFF);
-
- if (c == 0) {
- /* Found FF/00, which represents an FF data byte */
- c = 0xFF;
- } else {
- /* Oops, it's actually a marker indicating end of compressed data. */
- /* Better put it back for use later */
- state->unread_marker = c;
-
- no_more_data:
- /* There should be enough bits still left in the data segment; */
- /* if so, just break out of the outer while loop. */
- if (bits_left >= nbits)
- break;
- /* Uh-oh. Report corrupted data to user and stuff zeroes into
- * the data stream, so that we can produce some kind of image.
- * Note that this code will be repeated for each byte demanded
- * for the rest of the segment. We use a nonvolatile flag to ensure
- * that only one warning message appears.
- */
- if (! *(state->printed_eod_ptr)) {
- WARNMS(state->cinfo, JWRN_HIT_MARKER);
- *(state->printed_eod_ptr) = TRUE;
- }
- c = 0; /* insert a zero byte into bit buffer */
- }
- }
-
- /* OK, load c into get_buffer */
- get_buffer = (get_buffer << 8) | c;
- bits_left += 8;
- }
-
- /* Unload the local registers */
- state->next_input_byte = next_input_byte;
- state->bytes_in_buffer = bytes_in_buffer;
- state->get_buffer = get_buffer;
- state->bits_left = bits_left;
-
- return TRUE;
-}
-
-
-/*
- * Out-of-line code for Huffman code decoding.
- * See jdhuff.h for info about usage.
- */
-
-GLOBAL int
-jpeg_huff_decode (bitread_working_state * state,
- register bit_buf_type get_buffer, register int bits_left,
- d_derived_tbl * htbl, int min_bits)
-{
- register int l = min_bits;
- register INT32 code;
-
- /* HUFF_DECODE has determined that the code is at least min_bits */
- /* bits long, so fetch that many bits in one swoop. */
-
- CHECK_BIT_BUFFER(*state, l, return -1);
- code = GET_BITS(l);
-
- /* Collect the rest of the Huffman code one bit at a time. */
- /* This is per Figure F.16 in the JPEG spec. */
-
- while (code > htbl->maxcode[l]) {
- code <<= 1;
- CHECK_BIT_BUFFER(*state, 1, return -1);
- code |= GET_BITS(1);
- l++;
- }
-
- /* Unload the local registers */
- state->get_buffer = get_buffer;
- state->bits_left = bits_left;
-
- /* With garbage input we may reach the sentinel value l = 17. */
-
- if (l > 16) {
- WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
- return 0; /* fake a zero as the safest result */
- }
-
- return htbl->pub->huffval[ htbl->valptr[l] +
- ((int) (code - htbl->mincode[l])) ];
-}
-
-
-/*
- * Figure F.12: extend sign bit.
- * On some machines, a shift and add will be faster than a table lookup.
- */
-
-#ifdef AVOID_TABLES
-
-#define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-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)
-{
- huff_entropy_ptr entropy = (huff_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;
-
- /* Reset restart counter */
- entropy->restarts_to_go = cinfo->restart_interval;
-
- /* Next segment can get another out-of-data warning */
- entropy->bitstate.printed_eod = FALSE;
-
- return TRUE;
-}
-
-
-/*
- * Decode and return 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 HAS BEEN ZEROED BY THE CALLER.
- * (Wholesale zeroing is usually a little faster than retail...)
- *
- * Returns 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
- * this module, since we'll just re-assign them on the next call.)
- */
-
-METHODDEF boolean
-decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
-{
- huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
- register int s, k, r;
- int blkn, ci;
- JBLOCKROW block;
- BITREAD_STATE_VARS;
- savable_state state;
- d_derived_tbl * dctbl;
- d_derived_tbl * actbl;
- 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;
- }
-
- /* Load up working state */
- BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
- ASSIGN_STATE(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];
- dctbl = entropy->dc_derived_tbls[compptr->dc_tbl_no];
- actbl = entropy->ac_derived_tbls[compptr->ac_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, dctbl, return FALSE, label1);
- if (s) {
- CHECK_BIT_BUFFER(br_state, s, return FALSE);
- r = GET_BITS(s);
- s = HUFF_EXTEND(r, s);
- }
-
- /* Shortcut if component's values are not interesting */
- if (! compptr->component_needed)
- goto skip_ACs;
-
- /* Convert DC difference to actual value, update last_dc_val */
- s += state.last_dc_val[ci];
- state.last_dc_val[ci] = s;
- /* Output the DC coefficient (assumes jpeg_natural_order[0] = 0) */
- (*block)[0] = (JCOEF) s;
-
- /* Do we need to decode the AC coefficients for this component? */
- if (compptr->DCT_scaled_size > 1) {
-
- /* Section F.2.2.2: decode the AC coefficients */
- /* Since zeroes are skipped, output area must be cleared beforehand */
- for (k = 1; k < DCTSIZE2; k++) {
- HUFF_DECODE(s, br_state, actbl, 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);
- /* Output coefficient in natural (dezigzagged) order.
- * Note: the extra entries in jpeg_natural_order[] will save us
- * if k >= DCTSIZE2, which could happen if the data is corrupted.
- */
- (*block)[jpeg_natural_order[k]] = (JCOEF) s;
- } else {
- if (r != 15)
- break;
- k += 15;
- }
- }
-
- } else {
-skip_ACs:
-
- /* Section F.2.2.2: decode the AC coefficients */
- /* In this path we just discard the values */
- for (k = 1; k < DCTSIZE2; k++) {
- HUFF_DECODE(s, br_state, actbl, return FALSE, label3);
-
- r = s >> 4;
- s &= 15;
-
- if (s) {
- k += r;
- CHECK_BIT_BUFFER(br_state, s, return FALSE);
- DROP_BITS(s);
- } else {
- if (r != 15)
- break;
- k += 15;
- }
- }
-
- }
- }
-
- /* Completed MCU, so update state */
- BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
- ASSIGN_STATE(entropy->saved, state);
-
- /* Account for restart interval (no-op if not using restarts) */
- entropy->restarts_to_go--;
-
- return TRUE;
-}
-
-
-/*
- * Module initialization routine for Huffman entropy decoding.
- */
-
-GLOBAL void
-jinit_huff_decoder (j_decompress_ptr cinfo)
-{
- huff_entropy_ptr entropy;
- int i;
-
- entropy = (huff_entropy_ptr)
- (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
- SIZEOF(huff_entropy_decoder));
- cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
- entropy->pub.start_pass = start_pass_huff_decoder;
- entropy->pub.decode_mcu = decode_mcu;
-
- /* Mark tables unallocated */
- for (i = 0; i < NUM_HUFF_TBLS; i++) {
- entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
- }
-}
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