/[pcsx2_0.9.7]/trunk/3rdparty/libjpeg/jdhuff.c
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Contents of /trunk/3rdparty/libjpeg/jdhuff.c

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Revision 31 - (show annotations) (download)
Tue Sep 7 03:24:11 2010 UTC (9 years, 11 months ago) by william
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File size: 42318 byte(s)
committing r3113 initial commit again...
1 /*
2 * jdhuff.c
3 *
4 * Copyright (C) 1991-1997, Thomas G. Lane.
5 * Modified 2006-2009 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
8 *
9 * This file contains Huffman entropy decoding routines.
10 * Both sequential and progressive modes are supported in this single module.
11 *
12 * Much of the complexity here has to do with supporting input suspension.
13 * If the data source module demands suspension, we want to be able to back
14 * up to the start of the current MCU. To do this, we copy state variables
15 * into local working storage, and update them back to the permanent
16 * storage only upon successful completion of an MCU.
17 */
18
19 #define JPEG_INTERNALS
20 #include "jinclude.h"
21 #include "jpeglib.h"
22
23
24 /* Derived data constructed for each Huffman table */
25
26 #define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */
27
28 typedef struct {
29 /* Basic tables: (element [0] of each array is unused) */
30 INT32 maxcode[18]; /* largest code of length k (-1 if none) */
31 /* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */
32 INT32 valoffset[17]; /* huffval[] offset for codes of length k */
33 /* valoffset[k] = huffval[] index of 1st symbol of code length k, less
34 * the smallest code of length k; so given a code of length k, the
35 * corresponding symbol is huffval[code + valoffset[k]]
36 */
37
38 /* Link to public Huffman table (needed only in jpeg_huff_decode) */
39 JHUFF_TBL *pub;
40
41 /* Lookahead tables: indexed by the next HUFF_LOOKAHEAD bits of
42 * the input data stream. If the next Huffman code is no more
43 * than HUFF_LOOKAHEAD bits long, we can obtain its length and
44 * the corresponding symbol directly from these tables.
45 */
46 int look_nbits[1<<HUFF_LOOKAHEAD]; /* # bits, or 0 if too long */
47 UINT8 look_sym[1<<HUFF_LOOKAHEAD]; /* symbol, or unused */
48 } d_derived_tbl;
49
50
51 /*
52 * Fetching the next N bits from the input stream is a time-critical operation
53 * for the Huffman decoders. We implement it with a combination of inline
54 * macros and out-of-line subroutines. Note that N (the number of bits
55 * demanded at one time) never exceeds 15 for JPEG use.
56 *
57 * We read source bytes into get_buffer and dole out bits as needed.
58 * If get_buffer already contains enough bits, they are fetched in-line
59 * by the macros CHECK_BIT_BUFFER and GET_BITS. When there aren't enough
60 * bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer
61 * as full as possible (not just to the number of bits needed; this
62 * prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer).
63 * Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension.
64 * On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains
65 * at least the requested number of bits --- dummy zeroes are inserted if
66 * necessary.
67 */
68
69 typedef INT32 bit_buf_type; /* type of bit-extraction buffer */
70 #define BIT_BUF_SIZE 32 /* size of buffer in bits */
71
72 /* If long is > 32 bits on your machine, and shifting/masking longs is
73 * reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE
74 * appropriately should be a win. Unfortunately we can't define the size
75 * with something like #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8)
76 * because not all machines measure sizeof in 8-bit bytes.
77 */
78
79 typedef struct { /* Bitreading state saved across MCUs */
80 bit_buf_type get_buffer; /* current bit-extraction buffer */
81 int bits_left; /* # of unused bits in it */
82 } bitread_perm_state;
83
84 typedef struct { /* Bitreading working state within an MCU */
85 /* Current data source location */
86 /* We need a copy, rather than munging the original, in case of suspension */
87 const JOCTET * next_input_byte; /* => next byte to read from source */
88 size_t bytes_in_buffer; /* # of bytes remaining in source buffer */
89 /* Bit input buffer --- note these values are kept in register variables,
90 * not in this struct, inside the inner loops.
91 */
92 bit_buf_type get_buffer; /* current bit-extraction buffer */
93 int bits_left; /* # of unused bits in it */
94 /* Pointer needed by jpeg_fill_bit_buffer. */
95 j_decompress_ptr cinfo; /* back link to decompress master record */
96 } bitread_working_state;
97
98 /* Macros to declare and load/save bitread local variables. */
99 #define BITREAD_STATE_VARS \
100 register bit_buf_type get_buffer; \
101 register int bits_left; \
102 bitread_working_state br_state
103
104 #define BITREAD_LOAD_STATE(cinfop,permstate) \
105 br_state.cinfo = cinfop; \
106 br_state.next_input_byte = cinfop->src->next_input_byte; \
107 br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \
108 get_buffer = permstate.get_buffer; \
109 bits_left = permstate.bits_left;
110
111 #define BITREAD_SAVE_STATE(cinfop,permstate) \
112 cinfop->src->next_input_byte = br_state.next_input_byte; \
113 cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \
114 permstate.get_buffer = get_buffer; \
115 permstate.bits_left = bits_left
116
117 /*
118 * These macros provide the in-line portion of bit fetching.
119 * Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer
120 * before using GET_BITS, PEEK_BITS, or DROP_BITS.
121 * The variables get_buffer and bits_left are assumed to be locals,
122 * but the state struct might not be (jpeg_huff_decode needs this).
123 * CHECK_BIT_BUFFER(state,n,action);
124 * Ensure there are N bits in get_buffer; if suspend, take action.
125 * val = GET_BITS(n);
126 * Fetch next N bits.
127 * val = PEEK_BITS(n);
128 * Fetch next N bits without removing them from the buffer.
129 * DROP_BITS(n);
130 * Discard next N bits.
131 * The value N should be a simple variable, not an expression, because it
132 * is evaluated multiple times.
133 */
134
135 #define CHECK_BIT_BUFFER(state,nbits,action) \
136 { if (bits_left < (nbits)) { \
137 if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits)) \
138 { action; } \
139 get_buffer = (state).get_buffer; bits_left = (state).bits_left; } }
140
141 #define GET_BITS(nbits) \
142 (((int) (get_buffer >> (bits_left -= (nbits)))) & BIT_MASK(nbits))
143
144 #define PEEK_BITS(nbits) \
145 (((int) (get_buffer >> (bits_left - (nbits)))) & BIT_MASK(nbits))
146
147 #define DROP_BITS(nbits) \
148 (bits_left -= (nbits))
149
150
151 /*
152 * Code for extracting next Huffman-coded symbol from input bit stream.
153 * Again, this is time-critical and we make the main paths be macros.
154 *
155 * We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits
156 * without looping. Usually, more than 95% of the Huffman codes will be 8
157 * or fewer bits long. The few overlength codes are handled with a loop,
158 * which need not be inline code.
159 *
160 * Notes about the HUFF_DECODE macro:
161 * 1. Near the end of the data segment, we may fail to get enough bits
162 * for a lookahead. In that case, we do it the hard way.
163 * 2. If the lookahead table contains no entry, the next code must be
164 * more than HUFF_LOOKAHEAD bits long.
165 * 3. jpeg_huff_decode returns -1 if forced to suspend.
166 */
167
168 #define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \
169 { register int nb, look; \
170 if (bits_left < HUFF_LOOKAHEAD) { \
171 if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \
172 get_buffer = state.get_buffer; bits_left = state.bits_left; \
173 if (bits_left < HUFF_LOOKAHEAD) { \
174 nb = 1; goto slowlabel; \
175 } \
176 } \
177 look = PEEK_BITS(HUFF_LOOKAHEAD); \
178 if ((nb = htbl->look_nbits[look]) != 0) { \
179 DROP_BITS(nb); \
180 result = htbl->look_sym[look]; \
181 } else { \
182 nb = HUFF_LOOKAHEAD+1; \
183 slowlabel: \
184 if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \
185 { failaction; } \
186 get_buffer = state.get_buffer; bits_left = state.bits_left; \
187 } \
188 }
189
190
191 /*
192 * Expanded entropy decoder object for Huffman decoding.
193 *
194 * The savable_state subrecord contains fields that change within an MCU,
195 * but must not be updated permanently until we complete the MCU.
196 */
197
198 typedef struct {
199 unsigned int EOBRUN; /* remaining EOBs in EOBRUN */
200 int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
201 } savable_state;
202
203 /* This macro is to work around compilers with missing or broken
204 * structure assignment. You'll need to fix this code if you have
205 * such a compiler and you change MAX_COMPS_IN_SCAN.
206 */
207
208 #ifndef NO_STRUCT_ASSIGN
209 #define ASSIGN_STATE(dest,src) ((dest) = (src))
210 #else
211 #if MAX_COMPS_IN_SCAN == 4
212 #define ASSIGN_STATE(dest,src) \
213 ((dest).EOBRUN = (src).EOBRUN, \
214 (dest).last_dc_val[0] = (src).last_dc_val[0], \
215 (dest).last_dc_val[1] = (src).last_dc_val[1], \
216 (dest).last_dc_val[2] = (src).last_dc_val[2], \
217 (dest).last_dc_val[3] = (src).last_dc_val[3])
218 #endif
219 #endif
220
221
222 typedef struct {
223 struct jpeg_entropy_decoder pub; /* public fields */
224
225 /* These fields are loaded into local variables at start of each MCU.
226 * In case of suspension, we exit WITHOUT updating them.
227 */
228 bitread_perm_state bitstate; /* Bit buffer at start of MCU */
229 savable_state saved; /* Other state at start of MCU */
230
231 /* These fields are NOT loaded into local working state. */
232 unsigned int restarts_to_go; /* MCUs left in this restart interval */
233
234 /* Following two fields used only in progressive mode */
235
236 /* Pointers to derived tables (these workspaces have image lifespan) */
237 d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
238
239 d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
240
241 /* Following fields used only in sequential mode */
242
243 /* Pointers to derived tables (these workspaces have image lifespan) */
244 d_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
245 d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
246
247 /* Precalculated info set up by start_pass for use in decode_mcu: */
248
249 /* Pointers to derived tables to be used for each block within an MCU */
250 d_derived_tbl * dc_cur_tbls[D_MAX_BLOCKS_IN_MCU];
251 d_derived_tbl * ac_cur_tbls[D_MAX_BLOCKS_IN_MCU];
252 /* Whether we care about the DC and AC coefficient values for each block */
253 int coef_limit[D_MAX_BLOCKS_IN_MCU];
254 } huff_entropy_decoder;
255
256 typedef huff_entropy_decoder * huff_entropy_ptr;
257
258
259 static const int jpeg_zigzag_order[8][8] = {
260 { 0, 1, 5, 6, 14, 15, 27, 28 },
261 { 2, 4, 7, 13, 16, 26, 29, 42 },
262 { 3, 8, 12, 17, 25, 30, 41, 43 },
263 { 9, 11, 18, 24, 31, 40, 44, 53 },
264 { 10, 19, 23, 32, 39, 45, 52, 54 },
265 { 20, 22, 33, 38, 46, 51, 55, 60 },
266 { 21, 34, 37, 47, 50, 56, 59, 61 },
267 { 35, 36, 48, 49, 57, 58, 62, 63 }
268 };
269
270
271 /*
272 * Compute the derived values for a Huffman table.
273 * This routine also performs some validation checks on the table.
274 */
275
276 LOCAL(void)
277 jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno,
278 d_derived_tbl ** pdtbl)
279 {
280 JHUFF_TBL *htbl;
281 d_derived_tbl *dtbl;
282 int p, i, l, si, numsymbols;
283 int lookbits, ctr;
284 char huffsize[257];
285 unsigned int huffcode[257];
286 unsigned int code;
287
288 /* Note that huffsize[] and huffcode[] are filled in code-length order,
289 * paralleling the order of the symbols themselves in htbl->huffval[].
290 */
291
292 /* Find the input Huffman table */
293 if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
294 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
295 htbl =
296 isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
297 if (htbl == NULL)
298 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
299
300 /* Allocate a workspace if we haven't already done so. */
301 if (*pdtbl == NULL)
302 *pdtbl = (d_derived_tbl *)
303 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
304 SIZEOF(d_derived_tbl));
305 dtbl = *pdtbl;
306 dtbl->pub = htbl; /* fill in back link */
307
308 /* Figure C.1: make table of Huffman code length for each symbol */
309
310 p = 0;
311 for (l = 1; l <= 16; l++) {
312 i = (int) htbl->bits[l];
313 if (i < 0 || p + i > 256) /* protect against table overrun */
314 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
315 while (i--)
316 huffsize[p++] = (char) l;
317 }
318 huffsize[p] = 0;
319 numsymbols = p;
320
321 /* Figure C.2: generate the codes themselves */
322 /* We also validate that the counts represent a legal Huffman code tree. */
323
324 code = 0;
325 si = huffsize[0];
326 p = 0;
327 while (huffsize[p]) {
328 while (((int) huffsize[p]) == si) {
329 huffcode[p++] = code;
330 code++;
331 }
332 /* code is now 1 more than the last code used for codelength si; but
333 * it must still fit in si bits, since no code is allowed to be all ones.
334 */
335 if (((INT32) code) >= (((INT32) 1) << si))
336 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
337 code <<= 1;
338 si++;
339 }
340
341 /* Figure F.15: generate decoding tables for bit-sequential decoding */
342
343 p = 0;
344 for (l = 1; l <= 16; l++) {
345 if (htbl->bits[l]) {
346 /* valoffset[l] = huffval[] index of 1st symbol of code length l,
347 * minus the minimum code of length l
348 */
349 dtbl->valoffset[l] = (INT32) p - (INT32) huffcode[p];
350 p += htbl->bits[l];
351 dtbl->maxcode[l] = huffcode[p-1]; /* maximum code of length l */
352 } else {
353 dtbl->maxcode[l] = -1; /* -1 if no codes of this length */
354 }
355 }
356 dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */
357
358 /* Compute lookahead tables to speed up decoding.
359 * First we set all the table entries to 0, indicating "too long";
360 * then we iterate through the Huffman codes that are short enough and
361 * fill in all the entries that correspond to bit sequences starting
362 * with that code.
363 */
364
365 MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits));
366
367 p = 0;
368 for (l = 1; l <= HUFF_LOOKAHEAD; l++) {
369 for (i = 1; i <= (int) htbl->bits[l]; i++, p++) {
370 /* l = current code's length, p = its index in huffcode[] & huffval[]. */
371 /* Generate left-justified code followed by all possible bit sequences */
372 lookbits = huffcode[p] << (HUFF_LOOKAHEAD-l);
373 for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) {
374 dtbl->look_nbits[lookbits] = l;
375 dtbl->look_sym[lookbits] = htbl->huffval[p];
376 lookbits++;
377 }
378 }
379 }
380
381 /* Validate symbols as being reasonable.
382 * For AC tables, we make no check, but accept all byte values 0..255.
383 * For DC tables, we require the symbols to be in range 0..15.
384 * (Tighter bounds could be applied depending on the data depth and mode,
385 * but this is sufficient to ensure safe decoding.)
386 */
387 if (isDC) {
388 for (i = 0; i < numsymbols; i++) {
389 int sym = htbl->huffval[i];
390 if (sym < 0 || sym > 15)
391 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
392 }
393 }
394 }
395
396
397 /*
398 * Out-of-line code for bit fetching.
399 * Note: current values of get_buffer and bits_left are passed as parameters,
400 * but are returned in the corresponding fields of the state struct.
401 *
402 * On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width
403 * of get_buffer to be used. (On machines with wider words, an even larger
404 * buffer could be used.) However, on some machines 32-bit shifts are
405 * quite slow and take time proportional to the number of places shifted.
406 * (This is true with most PC compilers, for instance.) In this case it may
407 * be a win to set MIN_GET_BITS to the minimum value of 15. This reduces the
408 * average shift distance at the cost of more calls to jpeg_fill_bit_buffer.
409 */
410
411 #ifdef SLOW_SHIFT_32
412 #define MIN_GET_BITS 15 /* minimum allowable value */
413 #else
414 #define MIN_GET_BITS (BIT_BUF_SIZE-7)
415 #endif
416
417
418 LOCAL(boolean)
419 jpeg_fill_bit_buffer (bitread_working_state * state,
420 register bit_buf_type get_buffer, register int bits_left,
421 int nbits)
422 /* Load up the bit buffer to a depth of at least nbits */
423 {
424 /* Copy heavily used state fields into locals (hopefully registers) */
425 register const JOCTET * next_input_byte = state->next_input_byte;
426 register size_t bytes_in_buffer = state->bytes_in_buffer;
427 j_decompress_ptr cinfo = state->cinfo;
428
429 /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */
430 /* (It is assumed that no request will be for more than that many bits.) */
431 /* We fail to do so only if we hit a marker or are forced to suspend. */
432
433 if (cinfo->unread_marker == 0) { /* cannot advance past a marker */
434 while (bits_left < MIN_GET_BITS) {
435 register int c;
436
437 /* Attempt to read a byte */
438 if (bytes_in_buffer == 0) {
439 if (! (*cinfo->src->fill_input_buffer) (cinfo))
440 return FALSE;
441 next_input_byte = cinfo->src->next_input_byte;
442 bytes_in_buffer = cinfo->src->bytes_in_buffer;
443 }
444 bytes_in_buffer--;
445 c = GETJOCTET(*next_input_byte++);
446
447 /* If it's 0xFF, check and discard stuffed zero byte */
448 if (c == 0xFF) {
449 /* Loop here to discard any padding FF's on terminating marker,
450 * so that we can save a valid unread_marker value. NOTE: we will
451 * accept multiple FF's followed by a 0 as meaning a single FF data
452 * byte. This data pattern is not valid according to the standard.
453 */
454 do {
455 if (bytes_in_buffer == 0) {
456 if (! (*cinfo->src->fill_input_buffer) (cinfo))
457 return FALSE;
458 next_input_byte = cinfo->src->next_input_byte;
459 bytes_in_buffer = cinfo->src->bytes_in_buffer;
460 }
461 bytes_in_buffer--;
462 c = GETJOCTET(*next_input_byte++);
463 } while (c == 0xFF);
464
465 if (c == 0) {
466 /* Found FF/00, which represents an FF data byte */
467 c = 0xFF;
468 } else {
469 /* Oops, it's actually a marker indicating end of compressed data.
470 * Save the marker code for later use.
471 * Fine point: it might appear that we should save the marker into
472 * bitread working state, not straight into permanent state. But
473 * once we have hit a marker, we cannot need to suspend within the
474 * current MCU, because we will read no more bytes from the data
475 * source. So it is OK to update permanent state right away.
476 */
477 cinfo->unread_marker = c;
478 /* See if we need to insert some fake zero bits. */
479 goto no_more_bytes;
480 }
481 }
482
483 /* OK, load c into get_buffer */
484 get_buffer = (get_buffer << 8) | c;
485 bits_left += 8;
486 } /* end while */
487 } else {
488 no_more_bytes:
489 /* We get here if we've read the marker that terminates the compressed
490 * data segment. There should be enough bits in the buffer register
491 * to satisfy the request; if so, no problem.
492 */
493 if (nbits > bits_left) {
494 /* Uh-oh. Report corrupted data to user and stuff zeroes into
495 * the data stream, so that we can produce some kind of image.
496 * We use a nonvolatile flag to ensure that only one warning message
497 * appears per data segment.
498 */
499 if (! cinfo->entropy->insufficient_data) {
500 WARNMS(cinfo, JWRN_HIT_MARKER);
501 cinfo->entropy->insufficient_data = TRUE;
502 }
503 /* Fill the buffer with zero bits */
504 get_buffer <<= MIN_GET_BITS - bits_left;
505 bits_left = MIN_GET_BITS;
506 }
507 }
508
509 /* Unload the local registers */
510 state->next_input_byte = next_input_byte;
511 state->bytes_in_buffer = bytes_in_buffer;
512 state->get_buffer = get_buffer;
513 state->bits_left = bits_left;
514
515 return TRUE;
516 }
517
518
519 /*
520 * Figure F.12: extend sign bit.
521 * On some machines, a shift and sub will be faster than a table lookup.
522 */
523
524 #ifdef AVOID_TABLES
525
526 #define BIT_MASK(nbits) ((1<<(nbits))-1)
527 #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) - ((1<<(s))-1) : (x))
528
529 #else
530
531 #define BIT_MASK(nbits) bmask[nbits]
532 #define HUFF_EXTEND(x,s) ((x) <= bmask[(s) - 1] ? (x) - bmask[s] : (x))
533
534 static const int bmask[16] = /* bmask[n] is mask for n rightmost bits */
535 { 0, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF,
536 0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF };
537
538 #endif /* AVOID_TABLES */
539
540
541 /*
542 * Out-of-line code for Huffman code decoding.
543 */
544
545 LOCAL(int)
546 jpeg_huff_decode (bitread_working_state * state,
547 register bit_buf_type get_buffer, register int bits_left,
548 d_derived_tbl * htbl, int min_bits)
549 {
550 register int l = min_bits;
551 register INT32 code;
552
553 /* HUFF_DECODE has determined that the code is at least min_bits */
554 /* bits long, so fetch that many bits in one swoop. */
555
556 CHECK_BIT_BUFFER(*state, l, return -1);
557 code = GET_BITS(l);
558
559 /* Collect the rest of the Huffman code one bit at a time. */
560 /* This is per Figure F.16 in the JPEG spec. */
561
562 while (code > htbl->maxcode[l]) {
563 code <<= 1;
564 CHECK_BIT_BUFFER(*state, 1, return -1);
565 code |= GET_BITS(1);
566 l++;
567 }
568
569 /* Unload the local registers */
570 state->get_buffer = get_buffer;
571 state->bits_left = bits_left;
572
573 /* With garbage input we may reach the sentinel value l = 17. */
574
575 if (l > 16) {
576 WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
577 return 0; /* fake a zero as the safest result */
578 }
579
580 return htbl->pub->huffval[ (int) (code + htbl->valoffset[l]) ];
581 }
582
583
584 /*
585 * Check for a restart marker & resynchronize decoder.
586 * Returns FALSE if must suspend.
587 */
588
589 LOCAL(boolean)
590 process_restart (j_decompress_ptr cinfo)
591 {
592 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
593 int ci;
594
595 /* Throw away any unused bits remaining in bit buffer; */
596 /* include any full bytes in next_marker's count of discarded bytes */
597 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
598 entropy->bitstate.bits_left = 0;
599
600 /* Advance past the RSTn marker */
601 if (! (*cinfo->marker->read_restart_marker) (cinfo))
602 return FALSE;
603
604 /* Re-initialize DC predictions to 0 */
605 for (ci = 0; ci < cinfo->comps_in_scan; ci++)
606 entropy->saved.last_dc_val[ci] = 0;
607 /* Re-init EOB run count, too */
608 entropy->saved.EOBRUN = 0;
609
610 /* Reset restart counter */
611 entropy->restarts_to_go = cinfo->restart_interval;
612
613 /* Reset out-of-data flag, unless read_restart_marker left us smack up
614 * against a marker. In that case we will end up treating the next data
615 * segment as empty, and we can avoid producing bogus output pixels by
616 * leaving the flag set.
617 */
618 if (cinfo->unread_marker == 0)
619 entropy->pub.insufficient_data = FALSE;
620
621 return TRUE;
622 }
623
624
625 /*
626 * Huffman MCU decoding.
627 * Each of these routines decodes and returns one MCU's worth of
628 * Huffman-compressed coefficients.
629 * The coefficients are reordered from zigzag order into natural array order,
630 * but are not dequantized.
631 *
632 * The i'th block of the MCU is stored into the block pointed to by
633 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
634 * (Wholesale zeroing is usually a little faster than retail...)
635 *
636 * We return FALSE if data source requested suspension. In that case no
637 * changes have been made to permanent state. (Exception: some output
638 * coefficients may already have been assigned. This is harmless for
639 * spectral selection, since we'll just re-assign them on the next call.
640 * Successive approximation AC refinement has to be more careful, however.)
641 */
642
643 /*
644 * MCU decoding for DC initial scan (either spectral selection,
645 * or first pass of successive approximation).
646 */
647
648 METHODDEF(boolean)
649 decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
650 {
651 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
652 int Al = cinfo->Al;
653 register int s, r;
654 int blkn, ci;
655 JBLOCKROW block;
656 BITREAD_STATE_VARS;
657 savable_state state;
658 d_derived_tbl * tbl;
659 jpeg_component_info * compptr;
660
661 /* Process restart marker if needed; may have to suspend */
662 if (cinfo->restart_interval) {
663 if (entropy->restarts_to_go == 0)
664 if (! process_restart(cinfo))
665 return FALSE;
666 }
667
668 /* If we've run out of data, just leave the MCU set to zeroes.
669 * This way, we return uniform gray for the remainder of the segment.
670 */
671 if (! entropy->pub.insufficient_data) {
672
673 /* Load up working state */
674 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
675 ASSIGN_STATE(state, entropy->saved);
676
677 /* Outer loop handles each block in the MCU */
678
679 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
680 block = MCU_data[blkn];
681 ci = cinfo->MCU_membership[blkn];
682 compptr = cinfo->cur_comp_info[ci];
683 tbl = entropy->derived_tbls[compptr->dc_tbl_no];
684
685 /* Decode a single block's worth of coefficients */
686
687 /* Section F.2.2.1: decode the DC coefficient difference */
688 HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
689 if (s) {
690 CHECK_BIT_BUFFER(br_state, s, return FALSE);
691 r = GET_BITS(s);
692 s = HUFF_EXTEND(r, s);
693 }
694
695 /* Convert DC difference to actual value, update last_dc_val */
696 s += state.last_dc_val[ci];
697 state.last_dc_val[ci] = s;
698 /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
699 (*block)[0] = (JCOEF) (s << Al);
700 }
701
702 /* Completed MCU, so update state */
703 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
704 ASSIGN_STATE(entropy->saved, state);
705 }
706
707 /* Account for restart interval (no-op if not using restarts) */
708 entropy->restarts_to_go--;
709
710 return TRUE;
711 }
712
713
714 /*
715 * MCU decoding for AC initial scan (either spectral selection,
716 * or first pass of successive approximation).
717 */
718
719 METHODDEF(boolean)
720 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
721 {
722 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
723 int Se = cinfo->Se;
724 int Al = cinfo->Al;
725 register int s, k, r;
726 unsigned int EOBRUN;
727 JBLOCKROW block;
728 BITREAD_STATE_VARS;
729 d_derived_tbl * tbl;
730
731 /* Process restart marker if needed; may have to suspend */
732 if (cinfo->restart_interval) {
733 if (entropy->restarts_to_go == 0)
734 if (! process_restart(cinfo))
735 return FALSE;
736 }
737
738 /* If we've run out of data, just leave the MCU set to zeroes.
739 * This way, we return uniform gray for the remainder of the segment.
740 */
741 if (! entropy->pub.insufficient_data) {
742
743 /* Load up working state.
744 * We can avoid loading/saving bitread state if in an EOB run.
745 */
746 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
747
748 /* There is always only one block per MCU */
749
750 if (EOBRUN > 0) /* if it's a band of zeroes... */
751 EOBRUN--; /* ...process it now (we do nothing) */
752 else {
753 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
754 block = MCU_data[0];
755 tbl = entropy->ac_derived_tbl;
756
757 for (k = cinfo->Ss; k <= Se; k++) {
758 HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
759 r = s >> 4;
760 s &= 15;
761 if (s) {
762 k += r;
763 CHECK_BIT_BUFFER(br_state, s, return FALSE);
764 r = GET_BITS(s);
765 s = HUFF_EXTEND(r, s);
766 /* Scale and output coefficient in natural (dezigzagged) order */
767 (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al);
768 } else {
769 if (r == 15) { /* ZRL */
770 k += 15; /* skip 15 zeroes in band */
771 } else { /* EOBr, run length is 2^r + appended bits */
772 EOBRUN = 1 << r;
773 if (r) { /* EOBr, r > 0 */
774 CHECK_BIT_BUFFER(br_state, r, return FALSE);
775 r = GET_BITS(r);
776 EOBRUN += r;
777 }
778 EOBRUN--; /* this band is processed at this moment */
779 break; /* force end-of-band */
780 }
781 }
782 }
783
784 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
785 }
786
787 /* Completed MCU, so update state */
788 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
789 }
790
791 /* Account for restart interval (no-op if not using restarts) */
792 entropy->restarts_to_go--;
793
794 return TRUE;
795 }
796
797
798 /*
799 * MCU decoding for DC successive approximation refinement scan.
800 * Note: we assume such scans can be multi-component, although the spec
801 * is not very clear on the point.
802 */
803
804 METHODDEF(boolean)
805 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
806 {
807 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
808 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
809 int blkn;
810 JBLOCKROW block;
811 BITREAD_STATE_VARS;
812
813 /* Process restart marker if needed; may have to suspend */
814 if (cinfo->restart_interval) {
815 if (entropy->restarts_to_go == 0)
816 if (! process_restart(cinfo))
817 return FALSE;
818 }
819
820 /* Not worth the cycles to check insufficient_data here,
821 * since we will not change the data anyway if we read zeroes.
822 */
823
824 /* Load up working state */
825 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
826
827 /* Outer loop handles each block in the MCU */
828
829 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
830 block = MCU_data[blkn];
831
832 /* Encoded data is simply the next bit of the two's-complement DC value */
833 CHECK_BIT_BUFFER(br_state, 1, return FALSE);
834 if (GET_BITS(1))
835 (*block)[0] |= p1;
836 /* Note: since we use |=, repeating the assignment later is safe */
837 }
838
839 /* Completed MCU, so update state */
840 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
841
842 /* Account for restart interval (no-op if not using restarts) */
843 entropy->restarts_to_go--;
844
845 return TRUE;
846 }
847
848
849 /*
850 * MCU decoding for AC successive approximation refinement scan.
851 */
852
853 METHODDEF(boolean)
854 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
855 {
856 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
857 int Se = cinfo->Se;
858 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
859 int m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */
860 register int s, k, r;
861 unsigned int EOBRUN;
862 JBLOCKROW block;
863 JCOEFPTR thiscoef;
864 BITREAD_STATE_VARS;
865 d_derived_tbl * tbl;
866 int num_newnz;
867 int newnz_pos[DCTSIZE2];
868
869 /* Process restart marker if needed; may have to suspend */
870 if (cinfo->restart_interval) {
871 if (entropy->restarts_to_go == 0)
872 if (! process_restart(cinfo))
873 return FALSE;
874 }
875
876 /* If we've run out of data, don't modify the MCU.
877 */
878 if (! entropy->pub.insufficient_data) {
879
880 /* Load up working state */
881 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
882 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
883
884 /* There is always only one block per MCU */
885 block = MCU_data[0];
886 tbl = entropy->ac_derived_tbl;
887
888 /* If we are forced to suspend, we must undo the assignments to any newly
889 * nonzero coefficients in the block, because otherwise we'd get confused
890 * next time about which coefficients were already nonzero.
891 * But we need not undo addition of bits to already-nonzero coefficients;
892 * instead, we can test the current bit to see if we already did it.
893 */
894 num_newnz = 0;
895
896 /* initialize coefficient loop counter to start of band */
897 k = cinfo->Ss;
898
899 if (EOBRUN == 0) {
900 for (; k <= Se; k++) {
901 HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
902 r = s >> 4;
903 s &= 15;
904 if (s) {
905 if (s != 1) /* size of new coef should always be 1 */
906 WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
907 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
908 if (GET_BITS(1))
909 s = p1; /* newly nonzero coef is positive */
910 else
911 s = m1; /* newly nonzero coef is negative */
912 } else {
913 if (r != 15) {
914 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */
915 if (r) {
916 CHECK_BIT_BUFFER(br_state, r, goto undoit);
917 r = GET_BITS(r);
918 EOBRUN += r;
919 }
920 break; /* rest of block is handled by EOB logic */
921 }
922 /* note s = 0 for processing ZRL */
923 }
924 /* Advance over already-nonzero coefs and r still-zero coefs,
925 * appending correction bits to the nonzeroes. A correction bit is 1
926 * if the absolute value of the coefficient must be increased.
927 */
928 do {
929 thiscoef = *block + jpeg_natural_order[k];
930 if (*thiscoef != 0) {
931 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
932 if (GET_BITS(1)) {
933 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
934 if (*thiscoef >= 0)
935 *thiscoef += p1;
936 else
937 *thiscoef += m1;
938 }
939 }
940 } else {
941 if (--r < 0)
942 break; /* reached target zero coefficient */
943 }
944 k++;
945 } while (k <= Se);
946 if (s) {
947 int pos = jpeg_natural_order[k];
948 /* Output newly nonzero coefficient */
949 (*block)[pos] = (JCOEF) s;
950 /* Remember its position in case we have to suspend */
951 newnz_pos[num_newnz++] = pos;
952 }
953 }
954 }
955
956 if (EOBRUN > 0) {
957 /* Scan any remaining coefficient positions after the end-of-band
958 * (the last newly nonzero coefficient, if any). Append a correction
959 * bit to each already-nonzero coefficient. A correction bit is 1
960 * if the absolute value of the coefficient must be increased.
961 */
962 for (; k <= Se; k++) {
963 thiscoef = *block + jpeg_natural_order[k];
964 if (*thiscoef != 0) {
965 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
966 if (GET_BITS(1)) {
967 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
968 if (*thiscoef >= 0)
969 *thiscoef += p1;
970 else
971 *thiscoef += m1;
972 }
973 }
974 }
975 }
976 /* Count one block completed in EOB run */
977 EOBRUN--;
978 }
979
980 /* Completed MCU, so update state */
981 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
982 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
983 }
984
985 /* Account for restart interval (no-op if not using restarts) */
986 entropy->restarts_to_go--;
987
988 return TRUE;
989
990 undoit:
991 /* Re-zero any output coefficients that we made newly nonzero */
992 while (num_newnz > 0)
993 (*block)[newnz_pos[--num_newnz]] = 0;
994
995 return FALSE;
996 }
997
998
999 /*
1000 * Decode one MCU's worth of Huffman-compressed coefficients.
1001 */
1002
1003 METHODDEF(boolean)
1004 decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
1005 {
1006 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1007 int blkn;
1008 BITREAD_STATE_VARS;
1009 savable_state state;
1010
1011 /* Process restart marker if needed; may have to suspend */
1012 if (cinfo->restart_interval) {
1013 if (entropy->restarts_to_go == 0)
1014 if (! process_restart(cinfo))
1015 return FALSE;
1016 }
1017
1018 /* If we've run out of data, just leave the MCU set to zeroes.
1019 * This way, we return uniform gray for the remainder of the segment.
1020 */
1021 if (! entropy->pub.insufficient_data) {
1022
1023 /* Load up working state */
1024 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
1025 ASSIGN_STATE(state, entropy->saved);
1026
1027 /* Outer loop handles each block in the MCU */
1028
1029 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1030 JBLOCKROW block = MCU_data[blkn];
1031 d_derived_tbl * htbl;
1032 register int s, k, r;
1033 int coef_limit, ci;
1034
1035 /* Decode a single block's worth of coefficients */
1036
1037 /* Section F.2.2.1: decode the DC coefficient difference */
1038 htbl = entropy->dc_cur_tbls[blkn];
1039 HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1040
1041 htbl = entropy->ac_cur_tbls[blkn];
1042 k = 1;
1043 coef_limit = entropy->coef_limit[blkn];
1044 if (coef_limit) {
1045 /* Convert DC difference to actual value, update last_dc_val */
1046 if (s) {
1047 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1048 r = GET_BITS(s);
1049 s = HUFF_EXTEND(r, s);
1050 }
1051 ci = cinfo->MCU_membership[blkn];
1052 s += state.last_dc_val[ci];
1053 state.last_dc_val[ci] = s;
1054 /* Output the DC coefficient */
1055 (*block)[0] = (JCOEF) s;
1056
1057 /* Section F.2.2.2: decode the AC coefficients */
1058 /* Since zeroes are skipped, output area must be cleared beforehand */
1059 for (; k < coef_limit; k++) {
1060 HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
1061
1062 r = s >> 4;
1063 s &= 15;
1064
1065 if (s) {
1066 k += r;
1067 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1068 r = GET_BITS(s);
1069 s = HUFF_EXTEND(r, s);
1070 /* Output coefficient in natural (dezigzagged) order.
1071 * Note: the extra entries in jpeg_natural_order[] will save us
1072 * if k >= DCTSIZE2, which could happen if the data is corrupted.
1073 */
1074 (*block)[jpeg_natural_order[k]] = (JCOEF) s;
1075 } else {
1076 if (r != 15)
1077 goto EndOfBlock;
1078 k += 15;
1079 }
1080 }
1081 } else {
1082 if (s) {
1083 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1084 DROP_BITS(s);
1085 }
1086 }
1087
1088 /* Section F.2.2.2: decode the AC coefficients */
1089 /* In this path we just discard the values */
1090 for (; k < DCTSIZE2; k++) {
1091 HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
1092
1093 r = s >> 4;
1094 s &= 15;
1095
1096 if (s) {
1097 k += r;
1098 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1099 DROP_BITS(s);
1100 } else {
1101 if (r != 15)
1102 break;
1103 k += 15;
1104 }
1105 }
1106
1107 EndOfBlock: ;
1108 }
1109
1110 /* Completed MCU, so update state */
1111 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1112 ASSIGN_STATE(entropy->saved, state);
1113 }
1114
1115 /* Account for restart interval (no-op if not using restarts) */
1116 entropy->restarts_to_go--;
1117
1118 return TRUE;
1119 }
1120
1121
1122 /*
1123 * Initialize for a Huffman-compressed scan.
1124 */
1125
1126 METHODDEF(void)
1127 start_pass_huff_decoder (j_decompress_ptr cinfo)
1128 {
1129 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1130 int ci, blkn, dctbl, actbl, i;
1131 jpeg_component_info * compptr;
1132
1133 if (cinfo->progressive_mode) {
1134 /* Validate progressive scan parameters */
1135 if (cinfo->Ss == 0) {
1136 if (cinfo->Se != 0)
1137 goto bad;
1138 } else {
1139 /* need not check Ss/Se < 0 since they came from unsigned bytes */
1140 if (cinfo->Se < cinfo->Ss || cinfo->Se >= DCTSIZE2)
1141 goto bad;
1142 /* AC scans may have only one component */
1143 if (cinfo->comps_in_scan != 1)
1144 goto bad;
1145 }
1146 if (cinfo->Ah != 0) {
1147 /* Successive approximation refinement scan: must have Al = Ah-1. */
1148 if (cinfo->Ah-1 != cinfo->Al)
1149 goto bad;
1150 }
1151 if (cinfo->Al > 13) { /* need not check for < 0 */
1152 /* Arguably the maximum Al value should be less than 13 for 8-bit precision,
1153 * but the spec doesn't say so, and we try to be liberal about what we
1154 * accept. Note: large Al values could result in out-of-range DC
1155 * coefficients during early scans, leading to bizarre displays due to
1156 * overflows in the IDCT math. But we won't crash.
1157 */
1158 bad:
1159 ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
1160 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
1161 }
1162 /* Update progression status, and verify that scan order is legal.
1163 * Note that inter-scan inconsistencies are treated as warnings
1164 * not fatal errors ... not clear if this is right way to behave.
1165 */
1166 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1167 int coefi, cindex = cinfo->cur_comp_info[ci]->component_index;
1168 int *coef_bit_ptr = & cinfo->coef_bits[cindex][0];
1169 if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
1170 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
1171 for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
1172 int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
1173 if (cinfo->Ah != expected)
1174 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
1175 coef_bit_ptr[coefi] = cinfo->Al;
1176 }
1177 }
1178
1179 /* Select MCU decoding routine */
1180 if (cinfo->Ah == 0) {
1181 if (cinfo->Ss == 0)
1182 entropy->pub.decode_mcu = decode_mcu_DC_first;
1183 else
1184 entropy->pub.decode_mcu = decode_mcu_AC_first;
1185 } else {
1186 if (cinfo->Ss == 0)
1187 entropy->pub.decode_mcu = decode_mcu_DC_refine;
1188 else
1189 entropy->pub.decode_mcu = decode_mcu_AC_refine;
1190 }
1191
1192 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1193 compptr = cinfo->cur_comp_info[ci];
1194 /* Make sure requested tables are present, and compute derived tables.
1195 * We may build same derived table more than once, but it's not expensive.
1196 */
1197 if (cinfo->Ss == 0) {
1198 if (cinfo->Ah == 0) { /* DC refinement needs no table */
1199 i = compptr->dc_tbl_no;
1200 jpeg_make_d_derived_tbl(cinfo, TRUE, i,
1201 & entropy->derived_tbls[i]);
1202 }
1203 } else {
1204 i = compptr->ac_tbl_no;
1205 jpeg_make_d_derived_tbl(cinfo, FALSE, i,
1206 & entropy->derived_tbls[i]);
1207 /* remember the single active table */
1208 entropy->ac_derived_tbl = entropy->derived_tbls[i];
1209 }
1210 /* Initialize DC predictions to 0 */
1211 entropy->saved.last_dc_val[ci] = 0;
1212 }
1213
1214 /* Initialize private state variables */
1215 entropy->saved.EOBRUN = 0;
1216 } else {
1217 /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
1218 * This ought to be an error condition, but we make it a warning because
1219 * there are some baseline files out there with all zeroes in these bytes.
1220 */
1221 if (cinfo->Ss != 0 || cinfo->Se != DCTSIZE2-1 ||
1222 cinfo->Ah != 0 || cinfo->Al != 0)
1223 WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
1224
1225 /* Select MCU decoding routine */
1226 entropy->pub.decode_mcu = decode_mcu;
1227
1228 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1229 compptr = cinfo->cur_comp_info[ci];
1230 dctbl = compptr->dc_tbl_no;
1231 actbl = compptr->ac_tbl_no;
1232 /* Compute derived values for Huffman tables */
1233 /* We may do this more than once for a table, but it's not expensive */
1234 jpeg_make_d_derived_tbl(cinfo, TRUE, dctbl,
1235 & entropy->dc_derived_tbls[dctbl]);
1236 jpeg_make_d_derived_tbl(cinfo, FALSE, actbl,
1237 & entropy->ac_derived_tbls[actbl]);
1238 /* Initialize DC predictions to 0 */
1239 entropy->saved.last_dc_val[ci] = 0;
1240 }
1241
1242 /* Precalculate decoding info for each block in an MCU of this scan */
1243 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1244 ci = cinfo->MCU_membership[blkn];
1245 compptr = cinfo->cur_comp_info[ci];
1246 /* Precalculate which table to use for each block */
1247 entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no];
1248 entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no];
1249 /* Decide whether we really care about the coefficient values */
1250 if (compptr->component_needed) {
1251 ci = compptr->DCT_v_scaled_size;
1252 if (ci <= 0 || ci > 8) ci = 8;
1253 i = compptr->DCT_h_scaled_size;
1254 if (i <= 0 || i > 8) i = 8;
1255 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1];
1256 } else {
1257 entropy->coef_limit[blkn] = 0;
1258 }
1259 }
1260 }
1261
1262 /* Initialize bitread state variables */
1263 entropy->bitstate.bits_left = 0;
1264 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
1265 entropy->pub.insufficient_data = FALSE;
1266
1267 /* Initialize restart counter */
1268 entropy->restarts_to_go = cinfo->restart_interval;
1269 }
1270
1271
1272 /*
1273 * Module initialization routine for Huffman entropy decoding.
1274 */
1275
1276 GLOBAL(void)
1277 jinit_huff_decoder (j_decompress_ptr cinfo)
1278 {
1279 huff_entropy_ptr entropy;
1280 int i;
1281
1282 entropy = (huff_entropy_ptr)
1283 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1284 SIZEOF(huff_entropy_decoder));
1285 cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
1286 entropy->pub.start_pass = start_pass_huff_decoder;
1287
1288 if (cinfo->progressive_mode) {
1289 /* Create progression status table */
1290 int *coef_bit_ptr, ci;
1291 cinfo->coef_bits = (int (*)[DCTSIZE2])
1292 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1293 cinfo->num_components*DCTSIZE2*SIZEOF(int));
1294 coef_bit_ptr = & cinfo->coef_bits[0][0];
1295 for (ci = 0; ci < cinfo->num_components; ci++)
1296 for (i = 0; i < DCTSIZE2; i++)
1297 *coef_bit_ptr++ = -1;
1298
1299 /* Mark derived tables unallocated */
1300 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1301 entropy->derived_tbls[i] = NULL;
1302 }
1303 } else {
1304 /* Mark tables unallocated */
1305 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1306 entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
1307 }
1308 }
1309 }

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