diff options
Diffstat (limited to 'plugins/AdvaImg/src/LibJPEG/jdhuff.c')
| -rw-r--r-- | plugins/AdvaImg/src/LibJPEG/jdhuff.c | 3083 |
1 files changed, 1542 insertions, 1541 deletions
diff --git a/plugins/AdvaImg/src/LibJPEG/jdhuff.c b/plugins/AdvaImg/src/LibJPEG/jdhuff.c index 06f92fe47f..b18ff7a20a 100644 --- a/plugins/AdvaImg/src/LibJPEG/jdhuff.c +++ b/plugins/AdvaImg/src/LibJPEG/jdhuff.c @@ -1,1541 +1,1542 @@ -/* - * jdhuff.c - * - * Copyright (C) 1991-1997, Thomas G. Lane. - * Modified 2006-2009 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 Huffman entropy decoding routines. - * Both sequential and progressive modes are supported in this single module. - * - * 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 "jpeglib.h" - - -/* Derived data constructed for each Huffman table */ - -#define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */ - -typedef struct { - /* Basic tables: (element [0] of each array is unused) */ - INT32 maxcode[18]; /* largest code of length k (-1 if none) */ - /* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */ - INT32 valoffset[17]; /* huffval[] offset for codes of length k */ - /* valoffset[k] = huffval[] index of 1st symbol of code length k, less - * the smallest code of length k; so given a code of length k, the - * corresponding symbol is huffval[code + valoffset[k]] - */ - - /* Link to public Huffman table (needed only in jpeg_huff_decode) */ - JHUFF_TBL *pub; - - /* Lookahead tables: indexed by the next HUFF_LOOKAHEAD bits of - * the input data stream. If the next Huffman code is no more - * than HUFF_LOOKAHEAD bits long, we can obtain its length and - * the corresponding symbol directly from these tables. - */ - int look_nbits[1<<HUFF_LOOKAHEAD]; /* # bits, or 0 if too long */ - UINT8 look_sym[1<<HUFF_LOOKAHEAD]; /* symbol, or unused */ -} d_derived_tbl; - - -/* - * Fetching the next N bits from the input stream is a time-critical operation - * for the Huffman decoders. We implement it with a combination of inline - * macros and out-of-line subroutines. Note that N (the number of bits - * demanded at one time) never exceeds 15 for JPEG use. - * - * We read source bytes into get_buffer and dole out bits as needed. - * If get_buffer already contains enough bits, they are fetched in-line - * by the macros CHECK_BIT_BUFFER and GET_BITS. When there aren't enough - * bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer - * as full as possible (not just to the number of bits needed; this - * prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer). - * Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension. - * On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains - * at least the requested number of bits --- dummy zeroes are inserted if - * necessary. - */ - -typedef INT32 bit_buf_type; /* type of bit-extraction buffer */ -#define BIT_BUF_SIZE 32 /* size of buffer in bits */ - -/* If long is > 32 bits on your machine, and shifting/masking longs is - * reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE - * appropriately should be a win. Unfortunately we can't define the size - * with something like #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8) - * because not all machines measure sizeof in 8-bit bytes. - */ - -typedef struct { /* Bitreading state saved across MCUs */ - bit_buf_type get_buffer; /* current bit-extraction buffer */ - int bits_left; /* # of unused bits in it */ -} bitread_perm_state; - -typedef struct { /* Bitreading working state within an MCU */ - /* Current data source location */ - /* We need a copy, rather than munging the original, in case of suspension */ - const JOCTET * next_input_byte; /* => next byte to read from source */ - size_t bytes_in_buffer; /* # of bytes remaining in source buffer */ - /* Bit input buffer --- note these values are kept in register variables, - * not in this struct, inside the inner loops. - */ - bit_buf_type get_buffer; /* current bit-extraction buffer */ - int bits_left; /* # of unused bits in it */ - /* Pointer needed by jpeg_fill_bit_buffer. */ - j_decompress_ptr cinfo; /* back link to decompress master record */ -} bitread_working_state; - -/* Macros to declare and load/save bitread local variables. */ -#define BITREAD_STATE_VARS \ - register bit_buf_type get_buffer; \ - register int bits_left; \ - bitread_working_state br_state - -#define BITREAD_LOAD_STATE(cinfop,permstate) \ - br_state.cinfo = cinfop; \ - br_state.next_input_byte = cinfop->src->next_input_byte; \ - br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \ - get_buffer = permstate.get_buffer; \ - bits_left = permstate.bits_left; - -#define BITREAD_SAVE_STATE(cinfop,permstate) \ - cinfop->src->next_input_byte = br_state.next_input_byte; \ - cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \ - permstate.get_buffer = get_buffer; \ - permstate.bits_left = bits_left - -/* - * These macros provide the in-line portion of bit fetching. - * Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer - * before using GET_BITS, PEEK_BITS, or DROP_BITS. - * The variables get_buffer and bits_left are assumed to be locals, - * but the state struct might not be (jpeg_huff_decode needs this). - * CHECK_BIT_BUFFER(state,n,action); - * Ensure there are N bits in get_buffer; if suspend, take action. - * val = GET_BITS(n); - * Fetch next N bits. - * val = PEEK_BITS(n); - * Fetch next N bits without removing them from the buffer. - * DROP_BITS(n); - * Discard next N bits. - * The value N should be a simple variable, not an expression, because it - * is evaluated multiple times. - */ - -#define CHECK_BIT_BUFFER(state,nbits,action) \ - { if (bits_left < (nbits)) { \ - if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits)) \ - { action; } \ - get_buffer = (state).get_buffer; bits_left = (state).bits_left; } } - -#define GET_BITS(nbits) \ - (((int) (get_buffer >> (bits_left -= (nbits)))) & BIT_MASK(nbits)) - -#define PEEK_BITS(nbits) \ - (((int) (get_buffer >> (bits_left - (nbits)))) & BIT_MASK(nbits)) - -#define DROP_BITS(nbits) \ - (bits_left -= (nbits)) - - -/* - * Code for extracting next Huffman-coded symbol from input bit stream. - * Again, this is time-critical and we make the main paths be macros. - * - * We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits - * without looping. Usually, more than 95% of the Huffman codes will be 8 - * or fewer bits long. The few overlength codes are handled with a loop, - * which need not be inline code. - * - * Notes about the HUFF_DECODE macro: - * 1. Near the end of the data segment, we may fail to get enough bits - * for a lookahead. In that case, we do it the hard way. - * 2. If the lookahead table contains no entry, the next code must be - * more than HUFF_LOOKAHEAD bits long. - * 3. jpeg_huff_decode returns -1 if forced to suspend. - */ - -#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \ -{ register int nb, look; \ - if (bits_left < HUFF_LOOKAHEAD) { \ - if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \ - get_buffer = state.get_buffer; bits_left = state.bits_left; \ - if (bits_left < HUFF_LOOKAHEAD) { \ - nb = 1; goto slowlabel; \ - } \ - } \ - look = PEEK_BITS(HUFF_LOOKAHEAD); \ - if ((nb = htbl->look_nbits[look]) != 0) { \ - DROP_BITS(nb); \ - result = htbl->look_sym[look]; \ - } else { \ - nb = HUFF_LOOKAHEAD+1; \ -slowlabel: \ - if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \ - { failaction; } \ - get_buffer = state.get_buffer; bits_left = state.bits_left; \ - } \ -} - - -/* - * 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 { - unsigned int EOBRUN; /* remaining EOBs in EOBRUN */ - 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).EOBRUN = (src).EOBRUN, \ - (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. */ - boolean insufficient_data; /* set TRUE after emitting warning */ - unsigned int restarts_to_go; /* MCUs left in this restart interval */ - - /* Following two fields used only in progressive mode */ - - /* 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 */ - - /* Following fields used only in sequential mode */ - - /* 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 */ - int coef_limit[D_MAX_BLOCKS_IN_MCU]; -} huff_entropy_decoder; - -typedef huff_entropy_decoder * huff_entropy_ptr; - - -static const int jpeg_zigzag_order[8][8] = { - { 0, 1, 5, 6, 14, 15, 27, 28 }, - { 2, 4, 7, 13, 16, 26, 29, 42 }, - { 3, 8, 12, 17, 25, 30, 41, 43 }, - { 9, 11, 18, 24, 31, 40, 44, 53 }, - { 10, 19, 23, 32, 39, 45, 52, 54 }, - { 20, 22, 33, 38, 46, 51, 55, 60 }, - { 21, 34, 37, 47, 50, 56, 59, 61 }, - { 35, 36, 48, 49, 57, 58, 62, 63 } -}; - -static const int jpeg_zigzag_order7[7][7] = { - { 0, 1, 5, 6, 14, 15, 27 }, - { 2, 4, 7, 13, 16, 26, 28 }, - { 3, 8, 12, 17, 25, 29, 38 }, - { 9, 11, 18, 24, 30, 37, 39 }, - { 10, 19, 23, 31, 36, 40, 45 }, - { 20, 22, 32, 35, 41, 44, 46 }, - { 21, 33, 34, 42, 43, 47, 48 } -}; - -static const int jpeg_zigzag_order6[6][6] = { - { 0, 1, 5, 6, 14, 15 }, - { 2, 4, 7, 13, 16, 25 }, - { 3, 8, 12, 17, 24, 26 }, - { 9, 11, 18, 23, 27, 32 }, - { 10, 19, 22, 28, 31, 33 }, - { 20, 21, 29, 30, 34, 35 } -}; - -static const int jpeg_zigzag_order5[5][5] = { - { 0, 1, 5, 6, 14 }, - { 2, 4, 7, 13, 15 }, - { 3, 8, 12, 16, 21 }, - { 9, 11, 17, 20, 22 }, - { 10, 18, 19, 23, 24 } -}; - -static const int jpeg_zigzag_order4[4][4] = { - { 0, 1, 5, 6 }, - { 2, 4, 7, 12 }, - { 3, 8, 11, 13 }, - { 9, 10, 14, 15 } -}; - -static const int jpeg_zigzag_order3[3][3] = { - { 0, 1, 5 }, - { 2, 4, 6 }, - { 3, 7, 8 } -}; - -static const int jpeg_zigzag_order2[2][2] = { - { 0, 1 }, - { 2, 3 } -}; - - -/* - * Compute the derived values for a Huffman table. - * This routine also performs some validation checks on the table. - */ - -LOCAL(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 (((INT32) code) >= (((INT32) 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] = (INT32) p - (INT32) 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->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++; - } - } - } - - /* 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. - * 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 - - -LOCAL(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 (! ((huff_entropy_ptr) cinfo->entropy)->insufficient_data) { - WARNMS(cinfo, JWRN_HIT_MARKER); - ((huff_entropy_ptr) 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; -} - - -/* - * Figure F.12: extend sign bit. - * On some machines, a shift and sub will be faster than a table lookup. - */ - -#ifdef AVOID_TABLES - -#define BIT_MASK(nbits) ((1<<(nbits))-1) -#define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) - ((1<<(s))-1) : (x)) - -#else - -#define BIT_MASK(nbits) bmask[nbits] -#define HUFF_EXTEND(x,s) ((x) <= bmask[(s) - 1] ? (x) - bmask[s] : (x)) - -static const int bmask[16] = /* bmask[n] is mask for n rightmost bits */ - { 0, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF, - 0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF }; - -#endif /* AVOID_TABLES */ - - -/* - * Out-of-line code for Huffman code decoding. - */ - -LOCAL(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[ (int) (code + htbl->valoffset[l]) ]; -} - - -/* - * 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; - /* 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->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. - * (Wholesale zeroing is usually a little faster than retail...) - * - * 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) -{ - huff_entropy_ptr entropy = (huff_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->insufficient_data) { - - /* 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]; - 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 */ - 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) (s << Al); - } - - /* 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; -} - - -/* - * 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) -{ - huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; - register int s, k, r; - unsigned int EOBRUN; - int Se, Al; - const int * natural_order; - 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->insufficient_data) { - - Se = cinfo->Se; - Al = cinfo->Al; - natural_order = cinfo->natural_order; - - /* 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)[natural_order[k]] = (JCOEF) (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) */ - 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) -{ - huff_entropy_ptr entropy = (huff_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) */ - 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) -{ - huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; - register int s, k, r; - unsigned int EOBRUN; - int Se, p1, m1; - const int * natural_order; - 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->insufficient_data) { - - Se = cinfo->Se; - p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ - m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */ - natural_order = cinfo->natural_order; - - /* 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 + 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 += p1; - else - *thiscoef += m1; - } - } - } else { - if (--r < 0) - break; /* reached target zero coefficient */ - } - k++; - } while (k <= Se); - if (s) { - int pos = 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 + 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 += p1; - else - *thiscoef += 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) */ - 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; -} - - -/* - * Decode one MCU's worth of Huffman-compressed coefficients, - * partial blocks. - */ - -METHODDEF(boolean) -decode_mcu_sub (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) -{ - huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; - const int * natural_order; - int Se, blkn; - BITREAD_STATE_VARS; - savable_state state; - - /* 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->insufficient_data) { - - natural_order = cinfo->natural_order; - Se = cinfo->lim_Se; - - /* 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++) { - JBLOCKROW block = MCU_data[blkn]; - d_derived_tbl * htbl; - register int s, k, r; - int coef_limit, ci; - - /* Decode a single block's worth of coefficients */ - - /* Section F.2.2.1: decode the DC coefficient difference */ - htbl = entropy->dc_cur_tbls[blkn]; - HUFF_DECODE(s, br_state, htbl, return FALSE, label1); - - htbl = entropy->ac_cur_tbls[blkn]; - k = 1; - coef_limit = entropy->coef_limit[blkn]; - if (coef_limit) { - /* Convert DC difference to actual value, update last_dc_val */ - if (s) { - CHECK_BIT_BUFFER(br_state, s, return FALSE); - r = GET_BITS(s); - s = HUFF_EXTEND(r, s); - } - ci = cinfo->MCU_membership[blkn]; - s += state.last_dc_val[ci]; - state.last_dc_val[ci] = s; - /* Output the DC coefficient */ - (*block)[0] = (JCOEF) s; - - /* Section F.2.2.2: decode the AC coefficients */ - /* Since zeroes are skipped, output area must be cleared beforehand */ - for (; k < coef_limit; k++) { - HUFF_DECODE(s, br_state, htbl, 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 natural_order[] will save us - * if k > Se, which could happen if the data is corrupted. - */ - (*block)[natural_order[k]] = (JCOEF) s; - } else { - if (r != 15) - goto EndOfBlock; - k += 15; - } - } - } else { - if (s) { - CHECK_BIT_BUFFER(br_state, s, return FALSE); - DROP_BITS(s); - } - } - - /* Section F.2.2.2: decode the AC coefficients */ - /* In this path we just discard the values */ - for (; k <= Se; k++) { - HUFF_DECODE(s, br_state, htbl, 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; - } - } - - EndOfBlock: ; - } - - /* 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; -} - - -/* - * Decode one MCU's worth of Huffman-compressed coefficients, - * full-size blocks. - */ - -METHODDEF(boolean) -decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) -{ - huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; - int blkn; - BITREAD_STATE_VARS; - savable_state state; - - /* 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->insufficient_data) { - - /* 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++) { - JBLOCKROW block = MCU_data[blkn]; - d_derived_tbl * htbl; - register int s, k, r; - int coef_limit, ci; - - /* Decode a single block's worth of coefficients */ - - /* Section F.2.2.1: decode the DC coefficient difference */ - htbl = entropy->dc_cur_tbls[blkn]; - HUFF_DECODE(s, br_state, htbl, return FALSE, label1); - - htbl = entropy->ac_cur_tbls[blkn]; - k = 1; - coef_limit = entropy->coef_limit[blkn]; - if (coef_limit) { - /* Convert DC difference to actual value, update last_dc_val */ - if (s) { - CHECK_BIT_BUFFER(br_state, s, return FALSE); - r = GET_BITS(s); - s = HUFF_EXTEND(r, s); - } - ci = cinfo->MCU_membership[blkn]; - s += state.last_dc_val[ci]; - state.last_dc_val[ci] = s; - /* Output the DC coefficient */ - (*block)[0] = (JCOEF) s; - - /* Section F.2.2.2: decode the AC coefficients */ - /* Since zeroes are skipped, output area must be cleared beforehand */ - for (; k < coef_limit; k++) { - HUFF_DECODE(s, br_state, htbl, 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) - goto EndOfBlock; - k += 15; - } - } - } else { - if (s) { - CHECK_BIT_BUFFER(br_state, s, return FALSE); - DROP_BITS(s); - } - } - - /* Section F.2.2.2: decode the AC coefficients */ - /* In this path we just discard the values */ - for (; k < DCTSIZE2; k++) { - HUFF_DECODE(s, br_state, htbl, 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; - } - } - - EndOfBlock: ; - } - - /* 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; -} - - -/* - * 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, tbl, i; - 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 */ - /* 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. - */ - 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; - } - - 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 (cinfo->Ss == 0) { - if (cinfo->Ah == 0) { /* DC refinement needs no table */ - tbl = compptr->dc_tbl_no; - jpeg_make_d_derived_tbl(cinfo, TRUE, tbl, - & entropy->derived_tbls[tbl]); - } - } else { - tbl = compptr->ac_tbl_no; - jpeg_make_d_derived_tbl(cinfo, FALSE, tbl, - & entropy->derived_tbls[tbl]); - /* 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 private state variables */ - entropy->saved.EOBRUN = 0; - } 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 because - * there are some baseline files out there with all zeroes in these bytes. - */ - if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 || - ((cinfo->is_baseline || cinfo->Se < DCTSIZE2) && - cinfo->Se != cinfo->lim_Se)) - WARNMS(cinfo, JWRN_NOT_SEQUENTIAL); - - /* Select MCU decoding routine */ - /* We retain the hard-coded case for full-size blocks. - * This is not necessary, but it appears that this version is slightly - * more performant in the given implementation. - * With an improved implementation we would prefer a single optimized - * function. - */ - if (cinfo->lim_Se != DCTSIZE2-1) - entropy->pub.decode_mcu = decode_mcu_sub; - else - entropy->pub.decode_mcu = decode_mcu; - - for (ci = 0; ci < cinfo->comps_in_scan; ci++) { - compptr = cinfo->cur_comp_info[ci]; - /* Compute derived values for Huffman tables */ - /* We may do this more than once for a table, but it's not expensive */ - tbl = compptr->dc_tbl_no; - jpeg_make_d_derived_tbl(cinfo, TRUE, tbl, - & entropy->dc_derived_tbls[tbl]); - if (cinfo->lim_Se) { /* AC needs no table when not present */ - tbl = compptr->ac_tbl_no; - jpeg_make_d_derived_tbl(cinfo, FALSE, tbl, - & entropy->ac_derived_tbls[tbl]); - } - /* 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) { - ci = compptr->DCT_v_scaled_size; - i = compptr->DCT_h_scaled_size; - switch (cinfo->lim_Se) { - case (1*1-1): - entropy->coef_limit[blkn] = 1; - break; - case (2*2-1): - if (ci <= 0 || ci > 2) ci = 2; - if (i <= 0 || i > 2) i = 2; - entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order2[ci - 1][i - 1]; - break; - case (3*3-1): - if (ci <= 0 || ci > 3) ci = 3; - if (i <= 0 || i > 3) i = 3; - entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order3[ci - 1][i - 1]; - break; - case (4*4-1): - if (ci <= 0 || ci > 4) ci = 4; - if (i <= 0 || i > 4) i = 4; - entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order4[ci - 1][i - 1]; - break; - case (5*5-1): - if (ci <= 0 || ci > 5) ci = 5; - if (i <= 0 || i > 5) i = 5; - entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order5[ci - 1][i - 1]; - break; - case (6*6-1): - if (ci <= 0 || ci > 6) ci = 6; - if (i <= 0 || i > 6) i = 6; - entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order6[ci - 1][i - 1]; - break; - case (7*7-1): - if (ci <= 0 || ci > 7) ci = 7; - if (i <= 0 || i > 7) i = 7; - entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order7[ci - 1][i - 1]; - break; - default: - if (ci <= 0 || ci > 8) ci = 8; - if (i <= 0 || i > 8) i = 8; - entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1]; - break; - } - } else { - entropy->coef_limit[blkn] = 0; - } - } - } - - /* Initialize bitread state variables */ - entropy->bitstate.bits_left = 0; - entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */ - entropy->insufficient_data = FALSE; - - /* Initialize restart counter */ - entropy->restarts_to_go = cinfo->restart_interval; -} - - -/* - * 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; - - 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; - - /* Mark derived tables unallocated */ - for (i = 0; i < NUM_HUFF_TBLS; i++) { - entropy->derived_tbls[i] = NULL; - } - } else { - /* Mark tables unallocated */ - for (i = 0; i < NUM_HUFF_TBLS; i++) { - entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL; - } - } -} +/*
+ * jdhuff.c
+ *
+ * Copyright (C) 1991-1997, Thomas G. Lane.
+ * Modified 2006-2012 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 Huffman entropy decoding routines.
+ * Both sequential and progressive modes are supported in this single module.
+ *
+ * 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 "jpeglib.h"
+
+
+/* Derived data constructed for each Huffman table */
+
+#define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */
+
+typedef struct {
+ /* Basic tables: (element [0] of each array is unused) */
+ INT32 maxcode[18]; /* largest code of length k (-1 if none) */
+ /* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */
+ INT32 valoffset[17]; /* huffval[] offset for codes of length k */
+ /* valoffset[k] = huffval[] index of 1st symbol of code length k, less
+ * the smallest code of length k; so given a code of length k, the
+ * corresponding symbol is huffval[code + valoffset[k]]
+ */
+
+ /* Link to public Huffman table (needed only in jpeg_huff_decode) */
+ JHUFF_TBL *pub;
+
+ /* Lookahead tables: indexed by the next HUFF_LOOKAHEAD bits of
+ * the input data stream. If the next Huffman code is no more
+ * than HUFF_LOOKAHEAD bits long, we can obtain its length and
+ * the corresponding symbol directly from these tables.
+ */
+ int look_nbits[1<<HUFF_LOOKAHEAD]; /* # bits, or 0 if too long */
+ UINT8 look_sym[1<<HUFF_LOOKAHEAD]; /* symbol, or unused */
+} d_derived_tbl;
+
+
+/*
+ * Fetching the next N bits from the input stream is a time-critical operation
+ * for the Huffman decoders. We implement it with a combination of inline
+ * macros and out-of-line subroutines. Note that N (the number of bits
+ * demanded at one time) never exceeds 15 for JPEG use.
+ *
+ * We read source bytes into get_buffer and dole out bits as needed.
+ * If get_buffer already contains enough bits, they are fetched in-line
+ * by the macros CHECK_BIT_BUFFER and GET_BITS. When there aren't enough
+ * bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer
+ * as full as possible (not just to the number of bits needed; this
+ * prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer).
+ * Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension.
+ * On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains
+ * at least the requested number of bits --- dummy zeroes are inserted if
+ * necessary.
+ */
+
+typedef INT32 bit_buf_type; /* type of bit-extraction buffer */
+#define BIT_BUF_SIZE 32 /* size of buffer in bits */
+
+/* If long is > 32 bits on your machine, and shifting/masking longs is
+ * reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE
+ * appropriately should be a win. Unfortunately we can't define the size
+ * with something like #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8)
+ * because not all machines measure sizeof in 8-bit bytes.
+ */
+
+typedef struct { /* Bitreading state saved across MCUs */
+ bit_buf_type get_buffer; /* current bit-extraction buffer */
+ int bits_left; /* # of unused bits in it */
+} bitread_perm_state;
+
+typedef struct { /* Bitreading working state within an MCU */
+ /* Current data source location */
+ /* We need a copy, rather than munging the original, in case of suspension */
+ const JOCTET * next_input_byte; /* => next byte to read from source */
+ size_t bytes_in_buffer; /* # of bytes remaining in source buffer */
+ /* Bit input buffer --- note these values are kept in register variables,
+ * not in this struct, inside the inner loops.
+ */
+ bit_buf_type get_buffer; /* current bit-extraction buffer */
+ int bits_left; /* # of unused bits in it */
+ /* Pointer needed by jpeg_fill_bit_buffer. */
+ j_decompress_ptr cinfo; /* back link to decompress master record */
+} bitread_working_state;
+
+/* Macros to declare and load/save bitread local variables. */
+#define BITREAD_STATE_VARS \
+ register bit_buf_type get_buffer; \
+ register int bits_left; \
+ bitread_working_state br_state
+
+#define BITREAD_LOAD_STATE(cinfop,permstate) \
+ br_state.cinfo = cinfop; \
+ br_state.next_input_byte = cinfop->src->next_input_byte; \
+ br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \
+ get_buffer = permstate.get_buffer; \
+ bits_left = permstate.bits_left;
+
+#define BITREAD_SAVE_STATE(cinfop,permstate) \
+ cinfop->src->next_input_byte = br_state.next_input_byte; \
+ cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \
+ permstate.get_buffer = get_buffer; \
+ permstate.bits_left = bits_left
+
+/*
+ * These macros provide the in-line portion of bit fetching.
+ * Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer
+ * before using GET_BITS, PEEK_BITS, or DROP_BITS.
+ * The variables get_buffer and bits_left are assumed to be locals,
+ * but the state struct might not be (jpeg_huff_decode needs this).
+ * CHECK_BIT_BUFFER(state,n,action);
+ * Ensure there are N bits in get_buffer; if suspend, take action.
+ * val = GET_BITS(n);
+ * Fetch next N bits.
+ * val = PEEK_BITS(n);
+ * Fetch next N bits without removing them from the buffer.
+ * DROP_BITS(n);
+ * Discard next N bits.
+ * The value N should be a simple variable, not an expression, because it
+ * is evaluated multiple times.
+ */
+
+#define CHECK_BIT_BUFFER(state,nbits,action) \
+ { if (bits_left < (nbits)) { \
+ if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits)) \
+ { action; } \
+ get_buffer = (state).get_buffer; bits_left = (state).bits_left; } }
+
+#define GET_BITS(nbits) \
+ (((int) (get_buffer >> (bits_left -= (nbits)))) & BIT_MASK(nbits))
+
+#define PEEK_BITS(nbits) \
+ (((int) (get_buffer >> (bits_left - (nbits)))) & BIT_MASK(nbits))
+
+#define DROP_BITS(nbits) \
+ (bits_left -= (nbits))
+
+
+/*
+ * Code for extracting next Huffman-coded symbol from input bit stream.
+ * Again, this is time-critical and we make the main paths be macros.
+ *
+ * We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits
+ * without looping. Usually, more than 95% of the Huffman codes will be 8
+ * or fewer bits long. The few overlength codes are handled with a loop,
+ * which need not be inline code.
+ *
+ * Notes about the HUFF_DECODE macro:
+ * 1. Near the end of the data segment, we may fail to get enough bits
+ * for a lookahead. In that case, we do it the hard way.
+ * 2. If the lookahead table contains no entry, the next code must be
+ * more than HUFF_LOOKAHEAD bits long.
+ * 3. jpeg_huff_decode returns -1 if forced to suspend.
+ */
+
+#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \
+{ register int nb, look; \
+ if (bits_left < HUFF_LOOKAHEAD) { \
+ if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \
+ get_buffer = state.get_buffer; bits_left = state.bits_left; \
+ if (bits_left < HUFF_LOOKAHEAD) { \
+ nb = 1; goto slowlabel; \
+ } \
+ } \
+ look = PEEK_BITS(HUFF_LOOKAHEAD); \
+ if ((nb = htbl->look_nbits[look]) != 0) { \
+ DROP_BITS(nb); \
+ result = htbl->look_sym[look]; \
+ } else { \
+ nb = HUFF_LOOKAHEAD+1; \
+slowlabel: \
+ if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \
+ { failaction; } \
+ get_buffer = state.get_buffer; bits_left = state.bits_left; \
+ } \
+}
+
+
+/*
+ * 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 {
+ unsigned int EOBRUN; /* remaining EOBs in EOBRUN */
+ 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).EOBRUN = (src).EOBRUN, \
+ (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. */
+ boolean insufficient_data; /* set TRUE after emitting warning */
+ unsigned int restarts_to_go; /* MCUs left in this restart interval */
+
+ /* Following two fields used only in progressive mode */
+
+ /* 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 */
+
+ /* Following fields used only in sequential mode */
+
+ /* 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 */
+ int coef_limit[D_MAX_BLOCKS_IN_MCU];
+} huff_entropy_decoder;
+
+typedef huff_entropy_decoder * huff_entropy_ptr;
+
+
+static const int jpeg_zigzag_order[8][8] = {
+ { 0, 1, 5, 6, 14, 15, 27, 28 },
+ { 2, 4, 7, 13, 16, 26, 29, 42 },
+ { 3, 8, 12, 17, 25, 30, 41, 43 },
+ { 9, 11, 18, 24, 31, 40, 44, 53 },
+ { 10, 19, 23, 32, 39, 45, 52, 54 },
+ { 20, 22, 33, 38, 46, 51, 55, 60 },
+ { 21, 34, 37, 47, 50, 56, 59, 61 },
+ { 35, 36, 48, 49, 57, 58, 62, 63 }
+};
+
+static const int jpeg_zigzag_order7[7][7] = {
+ { 0, 1, 5, 6, 14, 15, 27 },
+ { 2, 4, 7, 13, 16, 26, 28 },
+ { 3, 8, 12, 17, 25, 29, 38 },
+ { 9, 11, 18, 24, 30, 37, 39 },
+ { 10, 19, 23, 31, 36, 40, 45 },
+ { 20, 22, 32, 35, 41, 44, 46 },
+ { 21, 33, 34, 42, 43, 47, 48 }
+};
+
+static const int jpeg_zigzag_order6[6][6] = {
+ { 0, 1, 5, 6, 14, 15 },
+ { 2, 4, 7, 13, 16, 25 },
+ { 3, 8, 12, 17, 24, 26 },
+ { 9, 11, 18, 23, 27, 32 },
+ { 10, 19, 22, 28, 31, 33 },
+ { 20, 21, 29, 30, 34, 35 }
+};
+
+static const int jpeg_zigzag_order5[5][5] = {
+ { 0, 1, 5, 6, 14 },
+ { 2, 4, 7, 13, 15 },
+ { 3, 8, 12, 16, 21 },
+ { 9, 11, 17, 20, 22 },
+ { 10, 18, 19, 23, 24 }
+};
+
+static const int jpeg_zigzag_order4[4][4] = {
+ { 0, 1, 5, 6 },
+ { 2, 4, 7, 12 },
+ { 3, 8, 11, 13 },
+ { 9, 10, 14, 15 }
+};
+
+static const int jpeg_zigzag_order3[3][3] = {
+ { 0, 1, 5 },
+ { 2, 4, 6 },
+ { 3, 7, 8 }
+};
+
+static const int jpeg_zigzag_order2[2][2] = {
+ { 0, 1 },
+ { 2, 3 }
+};
+
+
+/*
+ * Compute the derived values for a Huffman table.
+ * This routine also performs some validation checks on the table.
+ */
+
+LOCAL(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 (((INT32) code) >= (((INT32) 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] = (INT32) p - (INT32) 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->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++;
+ }
+ }
+ }
+
+ /* 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.
+ * 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
+
+
+LOCAL(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 (! ((huff_entropy_ptr) cinfo->entropy)->insufficient_data) {
+ WARNMS(cinfo, JWRN_HIT_MARKER);
+ ((huff_entropy_ptr) 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;
+}
+
+
+/*
+ * Figure F.12: extend sign bit.
+ * On some machines, a shift and sub will be faster than a table lookup.
+ */
+
+#ifdef AVOID_TABLES
+
+#define BIT_MASK(nbits) ((1<<(nbits))-1)
+#define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) - ((1<<(s))-1) : (x))
+
+#else
+
+#define BIT_MASK(nbits) bmask[nbits]
+#define HUFF_EXTEND(x,s) ((x) <= bmask[(s) - 1] ? (x) - bmask[s] : (x))
+
+static const int bmask[16] = /* bmask[n] is mask for n rightmost bits */
+ { 0, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF,
+ 0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF };
+
+#endif /* AVOID_TABLES */
+
+
+/*
+ * Out-of-line code for Huffman code decoding.
+ */
+
+LOCAL(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[ (int) (code + htbl->valoffset[l]) ];
+}
+
+
+/*
+ * 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;
+ /* 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->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.
+ * (Wholesale zeroing is usually a little faster than retail...)
+ *
+ * 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)
+{
+ huff_entropy_ptr entropy = (huff_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->insufficient_data) {
+
+ /* 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];
+ 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 */
+ 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) (s << Al);
+ }
+
+ /* 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;
+}
+
+
+/*
+ * 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)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
+ register int s, k, r;
+ unsigned int EOBRUN;
+ int Se, Al;
+ const int * natural_order;
+ 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->insufficient_data) {
+
+ Se = cinfo->Se;
+ Al = cinfo->Al;
+ natural_order = cinfo->natural_order;
+
+ /* 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) /* 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)[natural_order[k]] = (JCOEF) (s << Al);
+ } else {
+ if (r != 15) { /* EOBr, run length is 2^r + appended bits */
+ if (r) { /* EOBr, r > 0 */
+ EOBRUN = 1 << r;
+ 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 */
+ }
+ k += 15; /* ZRL: skip 15 zeroes in 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) */
+ 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)
+{
+ huff_entropy_ptr entropy = (huff_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) */
+ 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)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
+ register int s, k, r;
+ unsigned int EOBRUN;
+ int Se, p1, m1;
+ const int * natural_order;
+ 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->insufficient_data) {
+
+ Se = cinfo->Se;
+ p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
+ m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */
+ natural_order = cinfo->natural_order;
+
+ /* 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) {
+ do {
+ 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 + natural_order[k];
+ if (*thiscoef) {
+ 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 += p1;
+ else
+ *thiscoef += m1;
+ }
+ }
+ } else {
+ if (--r < 0)
+ break; /* reached target zero coefficient */
+ }
+ k++;
+ } while (k <= Se);
+ if (s) {
+ int pos = 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;
+ }
+ k++;
+ } while (k <= Se);
+ }
+
+ if (EOBRUN) {
+ /* 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.
+ */
+ do {
+ thiscoef = *block + natural_order[k];
+ if (*thiscoef) {
+ 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 += p1;
+ else
+ *thiscoef += m1;
+ }
+ }
+ }
+ k++;
+ } while (k <= Se);
+ /* 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) */
+ entropy->restarts_to_go--;
+
+ return TRUE;
+
+undoit:
+ /* Re-zero any output coefficients that we made newly nonzero */
+ while (num_newnz)
+ (*block)[newnz_pos[--num_newnz]] = 0;
+
+ return FALSE;
+}
+
+
+/*
+ * Decode one MCU's worth of Huffman-compressed coefficients,
+ * partial blocks.
+ */
+
+METHODDEF(boolean)
+decode_mcu_sub (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
+ const int * natural_order;
+ int Se, blkn;
+ BITREAD_STATE_VARS;
+ savable_state state;
+
+ /* 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->insufficient_data) {
+
+ natural_order = cinfo->natural_order;
+ Se = cinfo->lim_Se;
+
+ /* 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++) {
+ JBLOCKROW block = MCU_data[blkn];
+ d_derived_tbl * htbl;
+ register int s, k, r;
+ int coef_limit, ci;
+
+ /* Decode a single block's worth of coefficients */
+
+ /* Section F.2.2.1: decode the DC coefficient difference */
+ htbl = entropy->dc_cur_tbls[blkn];
+ HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
+
+ htbl = entropy->ac_cur_tbls[blkn];
+ k = 1;
+ coef_limit = entropy->coef_limit[blkn];
+ if (coef_limit) {
+ /* Convert DC difference to actual value, update last_dc_val */
+ if (s) {
+ CHECK_BIT_BUFFER(br_state, s, return FALSE);
+ r = GET_BITS(s);
+ s = HUFF_EXTEND(r, s);
+ }
+ ci = cinfo->MCU_membership[blkn];
+ s += state.last_dc_val[ci];
+ state.last_dc_val[ci] = s;
+ /* Output the DC coefficient */
+ (*block)[0] = (JCOEF) s;
+
+ /* Section F.2.2.2: decode the AC coefficients */
+ /* Since zeroes are skipped, output area must be cleared beforehand */
+ for (; k < coef_limit; k++) {
+ HUFF_DECODE(s, br_state, htbl, 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 natural_order[] will save us
+ * if k > Se, which could happen if the data is corrupted.
+ */
+ (*block)[natural_order[k]] = (JCOEF) s;
+ } else {
+ if (r != 15)
+ goto EndOfBlock;
+ k += 15;
+ }
+ }
+ } else {
+ if (s) {
+ CHECK_BIT_BUFFER(br_state, s, return FALSE);
+ DROP_BITS(s);
+ }
+ }
+
+ /* Section F.2.2.2: decode the AC coefficients */
+ /* In this path we just discard the values */
+ for (; k <= Se; k++) {
+ HUFF_DECODE(s, br_state, htbl, 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;
+ }
+ }
+
+ EndOfBlock: ;
+ }
+
+ /* 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;
+}
+
+
+/*
+ * Decode one MCU's worth of Huffman-compressed coefficients,
+ * full-size blocks.
+ */
+
+METHODDEF(boolean)
+decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
+ int blkn;
+ BITREAD_STATE_VARS;
+ savable_state state;
+
+ /* 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->insufficient_data) {
+
+ /* 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++) {
+ JBLOCKROW block = MCU_data[blkn];
+ d_derived_tbl * htbl;
+ register int s, k, r;
+ int coef_limit, ci;
+
+ /* Decode a single block's worth of coefficients */
+
+ /* Section F.2.2.1: decode the DC coefficient difference */
+ htbl = entropy->dc_cur_tbls[blkn];
+ HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
+
+ htbl = entropy->ac_cur_tbls[blkn];
+ k = 1;
+ coef_limit = entropy->coef_limit[blkn];
+ if (coef_limit) {
+ /* Convert DC difference to actual value, update last_dc_val */
+ if (s) {
+ CHECK_BIT_BUFFER(br_state, s, return FALSE);
+ r = GET_BITS(s);
+ s = HUFF_EXTEND(r, s);
+ }
+ ci = cinfo->MCU_membership[blkn];
+ s += state.last_dc_val[ci];
+ state.last_dc_val[ci] = s;
+ /* Output the DC coefficient */
+ (*block)[0] = (JCOEF) s;
+
+ /* Section F.2.2.2: decode the AC coefficients */
+ /* Since zeroes are skipped, output area must be cleared beforehand */
+ for (; k < coef_limit; k++) {
+ HUFF_DECODE(s, br_state, htbl, 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)
+ goto EndOfBlock;
+ k += 15;
+ }
+ }
+ } else {
+ if (s) {
+ CHECK_BIT_BUFFER(br_state, s, return FALSE);
+ DROP_BITS(s);
+ }
+ }
+
+ /* Section F.2.2.2: decode the AC coefficients */
+ /* In this path we just discard the values */
+ for (; k < DCTSIZE2; k++) {
+ HUFF_DECODE(s, br_state, htbl, 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;
+ }
+ }
+
+ EndOfBlock: ;
+ }
+
+ /* 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;
+}
+
+
+/*
+ * 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, tbl, i;
+ 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 */
+ /* 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.
+ */
+ 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;
+ }
+
+ 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 (cinfo->Ss == 0) {
+ if (cinfo->Ah == 0) { /* DC refinement needs no table */
+ tbl = compptr->dc_tbl_no;
+ jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
+ & entropy->derived_tbls[tbl]);
+ }
+ } else {
+ tbl = compptr->ac_tbl_no;
+ jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
+ & entropy->derived_tbls[tbl]);
+ /* 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 private state variables */
+ entropy->saved.EOBRUN = 0;
+ } 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 because
+ * there are some baseline files out there with all zeroes in these bytes.
+ */
+ if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||
+ ((cinfo->is_baseline || cinfo->Se < DCTSIZE2) &&
+ cinfo->Se != cinfo->lim_Se))
+ WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
+
+ /* Select MCU decoding routine */
+ /* We retain the hard-coded case for full-size blocks.
+ * This is not necessary, but it appears that this version is slightly
+ * more performant in the given implementation.
+ * With an improved implementation we would prefer a single optimized
+ * function.
+ */
+ if (cinfo->lim_Se != DCTSIZE2-1)
+ entropy->pub.decode_mcu = decode_mcu_sub;
+ else
+ entropy->pub.decode_mcu = decode_mcu;
+
+ for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
+ compptr = cinfo->cur_comp_info[ci];
+ /* Compute derived values for Huffman tables */
+ /* We may do this more than once for a table, but it's not expensive */
+ tbl = compptr->dc_tbl_no;
+ jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
+ & entropy->dc_derived_tbls[tbl]);
+ if (cinfo->lim_Se) { /* AC needs no table when not present */
+ tbl = compptr->ac_tbl_no;
+ jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
+ & entropy->ac_derived_tbls[tbl]);
+ }
+ /* 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) {
+ ci = compptr->DCT_v_scaled_size;
+ i = compptr->DCT_h_scaled_size;
+ switch (cinfo->lim_Se) {
+ case (1*1-1):
+ entropy->coef_limit[blkn] = 1;
+ break;
+ case (2*2-1):
+ if (ci <= 0 || ci > 2) ci = 2;
+ if (i <= 0 || i > 2) i = 2;
+ entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order2[ci - 1][i - 1];
+ break;
+ case (3*3-1):
+ if (ci <= 0 || ci > 3) ci = 3;
+ if (i <= 0 || i > 3) i = 3;
+ entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order3[ci - 1][i - 1];
+ break;
+ case (4*4-1):
+ if (ci <= 0 || ci > 4) ci = 4;
+ if (i <= 0 || i > 4) i = 4;
+ entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order4[ci - 1][i - 1];
+ break;
+ case (5*5-1):
+ if (ci <= 0 || ci > 5) ci = 5;
+ if (i <= 0 || i > 5) i = 5;
+ entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order5[ci - 1][i - 1];
+ break;
+ case (6*6-1):
+ if (ci <= 0 || ci > 6) ci = 6;
+ if (i <= 0 || i > 6) i = 6;
+ entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order6[ci - 1][i - 1];
+ break;
+ case (7*7-1):
+ if (ci <= 0 || ci > 7) ci = 7;
+ if (i <= 0 || i > 7) i = 7;
+ entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order7[ci - 1][i - 1];
+ break;
+ default:
+ if (ci <= 0 || ci > 8) ci = 8;
+ if (i <= 0 || i > 8) i = 8;
+ entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1];
+ break;
+ }
+ } else {
+ entropy->coef_limit[blkn] = 0;
+ }
+ }
+ }
+
+ /* Initialize bitread state variables */
+ entropy->bitstate.bits_left = 0;
+ entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
+ entropy->insufficient_data = FALSE;
+
+ /* Initialize restart counter */
+ entropy->restarts_to_go = cinfo->restart_interval;
+}
+
+
+/*
+ * 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 = &entropy->pub;
+ entropy->pub.start_pass = start_pass_huff_decoder;
+
+ 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;
+
+ /* Mark derived tables unallocated */
+ for (i = 0; i < NUM_HUFF_TBLS; i++) {
+ entropy->derived_tbls[i] = NULL;
+ }
+ } else {
+ /* 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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