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Diffstat (limited to 'media/libjpeg/jdhuff.c')
| -rw-r--r-- | media/libjpeg/jdhuff.c | 832 |
1 files changed, 832 insertions, 0 deletions
diff --git a/media/libjpeg/jdhuff.c b/media/libjpeg/jdhuff.c new file mode 100644 index 0000000000..3880890e23 --- /dev/null +++ b/media/libjpeg/jdhuff.c @@ -0,0 +1,832 @@ +/* + * 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. + * 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; + +/* 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]; + + /* 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 = GETJOCTET(*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 = 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. + * 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 = GETJOCTET(*buffer++); \ + c1 = GETJOCTET(*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) + +/* 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; +} + + +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); + ASSIGN_STATE(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]; + /* This is really just + * s += state.last_dc_val[ci]; + * It is written this way in order to shut up UBSan. + */ + s = (int)((unsigned int)s + (unsigned int)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); + ASSIGN_STATE(entropy->saved, state); + return TRUE; +} + + +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; + ASSIGN_STATE(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, slow_decode_mcu); + 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]; + s = (int)((unsigned int)s + (unsigned int)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, slow_decode_mcu); + 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, slow_decode_mcu); + 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) { +slow_decode_mcu: + 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); + ASSIGN_STATE(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) */ + 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; + } +} |