/* | |

* 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. */ | |

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 } | |

}; | |

/* | |

* 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 (! cinfo->entropy->insufficient_data) { | |

WARNMS(cinfo, JWRN_HIT_MARKER); | |

cinfo->entropy->insufficient_data = TRUE; | |

} | |

/* Fill the buffer with zero bits */ | |

get_buffer <<= MIN_GET_BITS - bits_left; | |

bits_left = MIN_GET_BITS; | |

} | |

} | |

/* Unload the local registers */ | |

state->next_input_byte = next_input_byte; | |

state->bytes_in_buffer = bytes_in_buffer; | |

state->get_buffer = get_buffer; | |

state->bits_left = bits_left; | |

return TRUE; | |

} | |

/* | |

* 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->pub.insufficient_data = FALSE; | |

return TRUE; | |

} | |

/* | |

* Huffman MCU decoding. | |

* Each of these routines decodes and returns one MCU's worth of | |

* Huffman-compressed coefficients. | |

* The coefficients are reordered from zigzag order into natural array order, | |

* but are not dequantized. | |

* | |

* The i'th block of the MCU is stored into the block pointed to by | |

* MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. | |

* (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->pub.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; | |

int Se = cinfo->Se; | |

int Al = cinfo->Al; | |

register int s, k, r; | |

unsigned int EOBRUN; | |

JBLOCKROW block; | |

BITREAD_STATE_VARS; | |

d_derived_tbl * tbl; | |

/* Process restart marker if needed; may have to suspend */ | |

if (cinfo->restart_interval) { | |

if (entropy->restarts_to_go == 0) | |

if (! process_restart(cinfo)) | |

return FALSE; | |

} | |

/* If we've run out of data, just leave the MCU set to zeroes. | |

* This way, we return uniform gray for the remainder of the segment. | |

*/ | |

if (! entropy->pub.insufficient_data) { | |

/* Load up working state. | |

* We can avoid loading/saving bitread state if in an EOB run. | |

*/ | |

EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ | |

/* There is always only one block per MCU */ | |

if (EOBRUN > 0) /* if it's a band of zeroes... */ | |

EOBRUN--; /* ...process it now (we do nothing) */ | |

else { | |

BITREAD_LOAD_STATE(cinfo,entropy->bitstate); | |

block = MCU_data[0]; | |

tbl = entropy->ac_derived_tbl; | |

for (k = cinfo->Ss; k <= Se; k++) { | |

HUFF_DECODE(s, br_state, tbl, return FALSE, label2); | |

r = s >> 4; | |

s &= 15; | |

if (s) { | |

k += r; | |

CHECK_BIT_BUFFER(br_state, s, return FALSE); | |

r = GET_BITS(s); | |

s = HUFF_EXTEND(r, s); | |

/* Scale and output coefficient in natural (dezigzagged) order */ | |

(*block)[jpeg_natural_order[k]] = (JCOEF) (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; | |

int Se = cinfo->Se; | |

int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ | |

int m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */ | |

register int s, k, r; | |

unsigned int EOBRUN; | |

JBLOCKROW block; | |

JCOEFPTR thiscoef; | |

BITREAD_STATE_VARS; | |

d_derived_tbl * tbl; | |

int num_newnz; | |

int newnz_pos[DCTSIZE2]; | |

/* Process restart marker if needed; may have to suspend */ | |

if (cinfo->restart_interval) { | |

if (entropy->restarts_to_go == 0) | |

if (! process_restart(cinfo)) | |

return FALSE; | |

} | |

/* If we've run out of data, don't modify the MCU. | |

*/ | |

if (! entropy->pub.insufficient_data) { | |

/* Load up working state */ | |

BITREAD_LOAD_STATE(cinfo,entropy->bitstate); | |

EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ | |

/* There is always only one block per MCU */ | |

block = MCU_data[0]; | |

tbl = entropy->ac_derived_tbl; | |

/* If we are forced to suspend, we must undo the assignments to any newly | |

* nonzero coefficients in the block, because otherwise we'd get confused | |

* next time about which coefficients were already nonzero. | |

* But we need not undo addition of bits to already-nonzero coefficients; | |

* instead, we can test the current bit to see if we already did it. | |

*/ | |

num_newnz = 0; | |

/* initialize coefficient loop counter to start of band */ | |

k = cinfo->Ss; | |

if (EOBRUN == 0) { | |

for (; k <= Se; k++) { | |

HUFF_DECODE(s, br_state, tbl, goto undoit, label3); | |

r = s >> 4; | |

s &= 15; | |

if (s) { | |

if (s != 1) /* size of new coef should always be 1 */ | |

WARNMS(cinfo, JWRN_HUFF_BAD_CODE); | |

CHECK_BIT_BUFFER(br_state, 1, goto undoit); | |

if (GET_BITS(1)) | |

s = p1; /* newly nonzero coef is positive */ | |

else | |

s = m1; /* newly nonzero coef is negative */ | |

} else { | |

if (r != 15) { | |

EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */ | |

if (r) { | |

CHECK_BIT_BUFFER(br_state, r, goto undoit); | |

r = GET_BITS(r); | |

EOBRUN += r; | |

} | |

break; /* rest of block is handled by EOB logic */ | |

} | |

/* note s = 0 for processing ZRL */ | |

} | |

/* Advance over already-nonzero coefs and r still-zero coefs, | |

* appending correction bits to the nonzeroes. A correction bit is 1 | |

* if the absolute value of the coefficient must be increased. | |

*/ | |

do { | |

thiscoef = *block + jpeg_natural_order[k]; | |

if (*thiscoef != 0) { | |

CHECK_BIT_BUFFER(br_state, 1, goto undoit); | |

if (GET_BITS(1)) { | |

if ((*thiscoef & p1) == 0) { /* do nothing if already set it */ | |

if (*thiscoef >= 0) | |

*thiscoef += p1; | |

else | |

*thiscoef += m1; | |

} | |

} | |

} else { | |

if (--r < 0) | |

break; /* reached target zero coefficient */ | |

} | |

k++; | |

} while (k <= Se); | |

if (s) { | |

int pos = jpeg_natural_order[k]; | |

/* Output newly nonzero coefficient */ | |

(*block)[pos] = (JCOEF) s; | |

/* Remember its position in case we have to suspend */ | |

newnz_pos[num_newnz++] = pos; | |

} | |

} | |

} | |

if (EOBRUN > 0) { | |

/* Scan any remaining coefficient positions after the end-of-band | |

* (the last newly nonzero coefficient, if any). Append a correction | |

* bit to each already-nonzero coefficient. A correction bit is 1 | |

* if the absolute value of the coefficient must be increased. | |

*/ | |

for (; k <= Se; k++) { | |

thiscoef = *block + jpeg_natural_order[k]; | |

if (*thiscoef != 0) { | |

CHECK_BIT_BUFFER(br_state, 1, goto undoit); | |

if (GET_BITS(1)) { | |

if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */ | |

if (*thiscoef >= 0) | |

*thiscoef += 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. | |

*/ | |

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->pub.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, dctbl, actbl, 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 >= DCTSIZE2) | |

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 */ | |

i = compptr->dc_tbl_no; | |

jpeg_make_d_derived_tbl(cinfo, TRUE, i, | |

& entropy->derived_tbls[i]); | |

} | |

} else { | |

i = compptr->ac_tbl_no; | |

jpeg_make_d_derived_tbl(cinfo, FALSE, i, | |

& entropy->derived_tbls[i]); | |

/* remember the single active table */ | |

entropy->ac_derived_tbl = entropy->derived_tbls[i]; | |

} | |

/* 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->Se != DCTSIZE2-1 || | |

cinfo->Ah != 0 || cinfo->Al != 0) | |

WARNMS(cinfo, JWRN_NOT_SEQUENTIAL); | |

/* Select MCU decoding routine */ | |

entropy->pub.decode_mcu = decode_mcu; | |

for (ci = 0; ci < cinfo->comps_in_scan; ci++) { | |

compptr = cinfo->cur_comp_info[ci]; | |

dctbl = compptr->dc_tbl_no; | |

actbl = compptr->ac_tbl_no; | |

/* Compute derived values for Huffman tables */ | |

/* We may do this more than once for a table, but it's not expensive */ | |

jpeg_make_d_derived_tbl(cinfo, TRUE, dctbl, | |

& entropy->dc_derived_tbls[dctbl]); | |

jpeg_make_d_derived_tbl(cinfo, FALSE, actbl, | |

& entropy->ac_derived_tbls[actbl]); | |

/* 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; | |

if (ci <= 0 || ci > 8) ci = 8; | |

i = compptr->DCT_h_scaled_size; | |

if (i <= 0 || i > 8) i = 8; | |

entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1]; | |

} 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->pub.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; | |

} | |

} | |

} |