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+/*
+ * jdhuff.c
+ *
+ * This file was part of the Independent JPEG Group's software:
+ * Copyright (C) 1991-1997, Thomas G. Lane.
+ * libjpeg-turbo Modifications:
+ * Copyright (C) 2009-2011, 2016, 2018-2019, D. R. Commander.
+ * Copyright (C) 2018, Matthias Räncker.
+ * For conditions of distribution and use, see the accompanying README.ijg
+ * 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.
+ *
+ * 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 jdphuff.c */
+#include "jpegcomp.h"
+#include "jstdhuff.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;
+
+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];
+
+ /* Precalculated info set up by start_pass for use in decode_mcu: */
+
+ /* Pointers to derived tables to be used for each block within an MCU */
+ d_derived_tbl *dc_cur_tbls[D_MAX_BLOCKS_IN_MCU];
+ d_derived_tbl *ac_cur_tbls[D_MAX_BLOCKS_IN_MCU];
+ /* Whether we care about the DC and AC coefficient values for each block */
+ boolean dc_needed[D_MAX_BLOCKS_IN_MCU];
+ boolean ac_needed[D_MAX_BLOCKS_IN_MCU];
+} 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, blkn, dctbl, actbl;
+ d_derived_tbl **pdtbl;
+ 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;
+ /* Compute derived values for Huffman tables */
+ /* We may do this more than once for a table, but it's not expensive */
+ pdtbl = (d_derived_tbl **)(entropy->dc_derived_tbls) + dctbl;
+ jpeg_make_d_derived_tbl(cinfo, TRUE, dctbl, pdtbl);
+ pdtbl = (d_derived_tbl **)(entropy->ac_derived_tbls) + actbl;
+ jpeg_make_d_derived_tbl(cinfo, FALSE, actbl, pdtbl);
+ /* Initialize DC predictions to 0 */
+ entropy->saved.last_dc_val[ci] = 0;
+ }
+
+ /* Precalculate decoding info for each block in an MCU of this scan */
+ for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
+ ci = cinfo->MCU_membership[blkn];
+ compptr = cinfo->cur_comp_info[ci];
+ /* Precalculate which table to use for each block */
+ entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no];
+ entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no];
+ /* Decide whether we really care about the coefficient values */
+ if (compptr->component_needed) {
+ entropy->dc_needed[blkn] = TRUE;
+ /* we don't need the ACs if producing a 1/8th-size image */
+ entropy->ac_needed[blkn] = (compptr->_DCT_scaled_size > 1);
+ } else {
+ entropy->dc_needed[blkn] = entropy->ac_needed[blkn] = FALSE;
+ }
+ }
+
+ /* 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 restart counter */
+ entropy->restarts_to_go = cinfo->restart_interval;
+}
+
+
+/*
+ * Compute the derived values for a Huffman table.
+ * This routine also performs some validation checks on the table.
+ *
+ * Note this is also used by jdphuff.c.
+ */
+
+GLOBAL(void)
+jpeg_make_d_derived_tbl(j_decompress_ptr cinfo, boolean isDC, int tblno,
+ d_derived_tbl **pdtbl)
+{
+ JHUFF_TBL *htbl;
+ d_derived_tbl *dtbl;
+ int p, i, l, si, numsymbols;
+ int lookbits, ctr;
+ char huffsize[257];
+ unsigned int huffcode[257];
+ unsigned int code;
+
+ /* Note that huffsize[] and huffcode[] are filled in code-length order,
+ * paralleling the order of the symbols themselves in htbl->huffval[].
+ */
+
+ /* Find the input Huffman table */
+ if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
+ ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
+ htbl =
+ isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
+ if (htbl == NULL)
+ ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
+
+ /* 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 */
+
+ p = 0;
+ for (l = 1; l <= 16; l++) {
+ i = (int)htbl->bits[l];
+ if (i < 0 || p + i > 256) /* protect against table overrun */
+ ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
+ while (i--)
+ huffsize[p++] = (char)l;
+ }
+ huffsize[p] = 0;
+ numsymbols = p;
+
+ /* Figure C.2: generate the codes themselves */
+ /* We also validate that the counts represent a legal Huffman code tree. */
+
+ code = 0;
+ si = huffsize[0];
+ p = 0;
+ while (huffsize[p]) {
+ while (((int)huffsize[p]) == si) {
+ huffcode[p++] = code;
+ code++;
+ }
+ /* code is now 1 more than the last code used for codelength si; but
+ * it must still fit in si bits, since no code is allowed to be all ones.
+ */
+ if (((JLONG)code) >= (((JLONG)1) << si))
+ ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
+ 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]) {
+ /* valoffset[l] = huffval[] index of 1st symbol of code length l,
+ * minus the minimum code of length l
+ */
+ dtbl->valoffset[l] = (JLONG)p - (JLONG)huffcode[p];
+ 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->valoffset[17] = 0;
+ 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.
+ */
+
+ for (i = 0; i < (1 << HUFF_LOOKAHEAD); i++)
+ dtbl->lookup[i] = (HUFF_LOOKAHEAD + 1) << HUFF_LOOKAHEAD;
+
+ 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->lookup[lookbits] = (l << HUFF_LOOKAHEAD) | htbl->huffval[p];
+ lookbits++;
+ }
+ }
+ }
+
+ /* Validate symbols as being reasonable.
+ * For AC tables, we make no check, but accept all byte values 0..255.
+ * For DC tables, we require the symbols to be in range 0..15.
+ * (Tighter bounds could be applied depending on the data depth and mode,
+ * but this is sufficient to ensure safe decoding.)
+ */
+ if (isDC) {
+ for (i = 0; i < numsymbols; i++) {
+ int sym = htbl->huffval[i];
+ if (sym < 0 || sym > 15)
+ ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
+ }
+ }
+}
+
+
+/*
+ * 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;
+ j_decompress_ptr cinfo = state->cinfo;
+
+ /* 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.) */
+ /* We fail to do so only if we hit a marker or are forced to suspend. */
+
+ if (cinfo->unread_marker == 0) { /* cannot advance past a marker */
+ while (bits_left < MIN_GET_BITS) {
+ register int c;
+
+ /* Attempt to read a byte */
+ if (bytes_in_buffer == 0) {
+ if (!(*cinfo->src->fill_input_buffer) (cinfo))
+ return FALSE;
+ next_input_byte = cinfo->src->next_input_byte;
+ bytes_in_buffer = cinfo->src->bytes_in_buffer;
+ }
+ bytes_in_buffer--;
+ c = *next_input_byte++;
+
+ /* If it's 0xFF, check and discard stuffed zero byte */
+ if (c == 0xFF) {
+ /* Loop here to discard any padding FF's on terminating marker,
+ * so that we can save a valid unread_marker value. NOTE: we will
+ * accept multiple FF's followed by a 0 as meaning a single FF data
+ * byte. This data pattern is not valid according to the standard.
+ */
+ do {
+ if (bytes_in_buffer == 0) {
+ if (!(*cinfo->src->fill_input_buffer) (cinfo))
+ return FALSE;
+ next_input_byte = cinfo->src->next_input_byte;
+ bytes_in_buffer = cinfo->src->bytes_in_buffer;
+ }
+ bytes_in_buffer--;
+ c = *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.
+ * Save the marker code for later use.
+ * Fine point: it might appear that we should save the marker into
+ * bitread working state, not straight into permanent state. But
+ * once we have hit a marker, we cannot need to suspend within the
+ * current MCU, because we will read no more bytes from the data
+ * source. So it is OK to update permanent state right away.
+ */
+ cinfo->unread_marker = c;
+ /* See if we need to insert some fake zero bits. */
+ goto no_more_bytes;
+ }
+ }
+
+ /* OK, load c into get_buffer */
+ get_buffer = (get_buffer << 8) | c;
+ bits_left += 8;
+ } /* end while */
+ } else {
+no_more_bytes:
+ /* We get here if we've read the marker that terminates the compressed
+ * data segment. There should be enough bits in the buffer register
+ * to satisfy the request; if so, no problem.
+ */
+ if (nbits > bits_left) {
+ /* Uh-oh. Report corrupted data to user and stuff zeroes into
+ * the data stream, so that we can produce some kind of image.
+ * We use a nonvolatile flag to ensure that only one warning message
+ * appears per data segment.
+ */
+ if (!cinfo->entropy->insufficient_data) {
+ WARNMS(cinfo, JWRN_HIT_MARKER);
+ cinfo->entropy->insufficient_data = TRUE;
+ }
+ /* Fill the buffer with zero bits */
+ get_buffer <<= MIN_GET_BITS - bits_left;
+ bits_left = MIN_GET_BITS;
+ }
+ }
+
+ /* 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;
+}
+
+
+/* Macro version of the above, which performs much better but does not
+ handle markers. We have to hand off any blocks with markers to the
+ slower routines. */
+
+#define GET_BYTE { \
+ register int c0, c1; \
+ c0 = *buffer++; \
+ c1 = *buffer; \
+ /* Pre-execute most common case */ \
+ get_buffer = (get_buffer << 8) | c0; \
+ bits_left += 8; \
+ if (c0 == 0xFF) { \
+ /* Pre-execute case of FF/00, which represents an FF data byte */ \
+ buffer++; \
+ if (c1 != 0) { \
+ /* Oops, it's actually a marker indicating end of compressed data. */ \
+ cinfo->unread_marker = c1; \
+ /* Back out pre-execution and fill the buffer with zero bits */ \
+ buffer -= 2; \
+ get_buffer &= ~0xFF; \
+ } \
+ } \
+}
+
+#if SIZEOF_SIZE_T == 8 || defined(_WIN64) || (defined(__x86_64__) && defined(__ILP32__))
+
+/* Pre-fetch 48 bytes, because the holding register is 64-bit */
+#define FILL_BIT_BUFFER_FAST \
+ if (bits_left <= 16) { \
+ GET_BYTE GET_BYTE GET_BYTE GET_BYTE GET_BYTE GET_BYTE \
+ }
+
+#else
+
+/* Pre-fetch 16 bytes, because the holding register is 32-bit */
+#define FILL_BIT_BUFFER_FAST \
+ if (bits_left <= 16) { \
+ GET_BYTE GET_BYTE \
+ }
+
+#endif
+
+
+/*
+ * 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 JLONG 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. */
+
+ 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[(int)(code + htbl->valoffset[l])];
+}
+
+
+/*
+ * 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 int)-1)
+#define HUFF_EXTEND(x, s) \
+ ((x) + ((((x) - (1 << ((s) - 1))) >> 31) & (((NEG_1) << (s)) + 1)))
+
+#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;
+
+ /* 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;
+}
+
+
+#if defined(__has_feature)
+#if __has_feature(undefined_behavior_sanitizer)
+__attribute__((no_sanitize("signed-integer-overflow"),
+ no_sanitize("unsigned-integer-overflow")))
+#endif
+#endif
+LOCAL(boolean)
+decode_mcu_slow(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
+ BITREAD_STATE_VARS;
+ int blkn;
+ savable_state state;
+ /* Outer loop handles each block in the MCU */
+
+ /* Load up working state */
+ BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
+ state = entropy->saved;
+
+ for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
+ JBLOCKROW block = MCU_data ? MCU_data[blkn] : NULL;
+ d_derived_tbl *dctbl = entropy->dc_cur_tbls[blkn];
+ d_derived_tbl *actbl = entropy->ac_cur_tbls[blkn];
+ register int s, k, r;
+
+ /* 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);
+ }
+
+ if (entropy->dc_needed[blkn]) {
+ /* Convert DC difference to actual value, update last_dc_val */
+ int ci = cinfo->MCU_membership[blkn];
+ /* Certain malformed JPEG images produce repeated DC coefficient
+ * differences of 2047 or -2047, which causes state.last_dc_val[ci] to
+ * grow until it overflows or underflows a 32-bit signed integer. This
+ * behavior is, to the best of our understanding, innocuous, and it is
+ * unclear how to work around it without potentially affecting
+ * performance. Thus, we (hopefully temporarily) suppress UBSan integer
+ * overflow errors for this function and decode_mcu_fast().
+ */
+ s += state.last_dc_val[ci];
+ state.last_dc_val[ci] = s;
+ if (block) {
+ /* Output the DC coefficient (assumes jpeg_natural_order[0] = 0) */
+ (*block)[0] = (JCOEF)s;
+ }
+ }
+
+ if (entropy->ac_needed[blkn] && block) {
+
+ /* 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 {
+
+ /* 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);
+ entropy->saved = state;
+ return TRUE;
+}
+
+
+#if defined(__has_feature)
+#if __has_feature(undefined_behavior_sanitizer)
+__attribute__((no_sanitize("signed-integer-overflow"),
+ no_sanitize("unsigned-integer-overflow")))
+#endif
+#endif
+LOCAL(boolean)
+decode_mcu_fast(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
+ BITREAD_STATE_VARS;
+ JOCTET *buffer;
+ int blkn;
+ savable_state state;
+ /* Outer loop handles each block in the MCU */
+
+ /* Load up working state */
+ BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
+ buffer = (JOCTET *)br_state.next_input_byte;
+ state = entropy->saved;
+
+ for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
+ JBLOCKROW block = MCU_data ? MCU_data[blkn] : NULL;
+ d_derived_tbl *dctbl = entropy->dc_cur_tbls[blkn];
+ d_derived_tbl *actbl = entropy->ac_cur_tbls[blkn];
+ register int s, k, r, l;
+
+ HUFF_DECODE_FAST(s, l, dctbl);
+ if (s) {
+ FILL_BIT_BUFFER_FAST
+ r = GET_BITS(s);
+ s = HUFF_EXTEND(r, s);
+ }
+
+ if (entropy->dc_needed[blkn]) {
+ int ci = cinfo->MCU_membership[blkn];
+ /* Refer to the comment in decode_mcu_slow() regarding the supression of
+ * a UBSan integer overflow error in this line of code.
+ */
+ s += state.last_dc_val[ci];
+ state.last_dc_val[ci] = s;
+ if (block)
+ (*block)[0] = (JCOEF)s;
+ }
+
+ if (entropy->ac_needed[blkn] && block) {
+
+ for (k = 1; k < DCTSIZE2; k++) {
+ HUFF_DECODE_FAST(s, l, actbl);
+ r = s >> 4;
+ s &= 15;
+
+ if (s) {
+ k += r;
+ FILL_BIT_BUFFER_FAST
+ r = GET_BITS(s);
+ s = HUFF_EXTEND(r, s);
+ (*block)[jpeg_natural_order[k]] = (JCOEF)s;
+ } else {
+ if (r != 15) break;
+ k += 15;
+ }
+ }
+
+ } else {
+
+ for (k = 1; k < DCTSIZE2; k++) {
+ HUFF_DECODE_FAST(s, l, actbl);
+ r = s >> 4;
+ s &= 15;
+
+ if (s) {
+ k += r;
+ FILL_BIT_BUFFER_FAST
+ DROP_BITS(s);
+ } else {
+ if (r != 15) break;
+ k += 15;
+ }
+ }
+ }
+ }
+
+ if (cinfo->unread_marker != 0) {
+ cinfo->unread_marker = 0;
+ return FALSE;
+ }
+
+ br_state.bytes_in_buffer -= (buffer - br_state.next_input_byte);
+ br_state.next_input_byte = buffer;
+ BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
+ entropy->saved = state;
+ 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.)
+ */
+
+#define BUFSIZE (DCTSIZE2 * 8)
+
+METHODDEF(boolean)
+decode_mcu(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
+ int usefast = 1;
+
+ /* 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;
+ usefast = 0;
+ }
+
+ if (cinfo->src->bytes_in_buffer < BUFSIZE * (size_t)cinfo->blocks_in_MCU ||
+ cinfo->unread_marker != 0)
+ usefast = 0;
+
+ /* 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) {
+
+ if (usefast) {
+ if (!decode_mcu_fast(cinfo, MCU_data)) goto use_slow;
+ } else {
+use_slow:
+ if (!decode_mcu_slow(cinfo, MCU_data)) return FALSE;
+ }
+
+ }
+
+ /* Account for restart interval (no-op if not using restarts) */
+ if (cinfo->restart_interval)
+ 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;
+
+ /* Motion JPEG frames typically do not include the Huffman tables if they
+ are the default tables. Thus, if the tables are not set by the time
+ the Huffman decoder is initialized (usually within the body of
+ jpeg_start_decompress()), we set them to default values. */
+ std_huff_tables((j_common_ptr)cinfo);
+
+ 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;
+ }
+}