/* | |
* 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; | |
} | |
} | |
} |