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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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1:1d09e1dec1d9 2:b50eed0cc0ef
1 /*
2 * jdhuff.c
3 *
4 * Copyright (C) 1991-1997, Thomas G. Lane.
5 * Modified 2006-2020 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 boolean insufficient_data; /* set TRUE after emitting warning */
233 unsigned int restarts_to_go; /* MCUs left in this restart interval */
234
235 /* Following two fields used only in progressive mode */
236
237 /* Pointers to derived tables (these workspaces have image lifespan) */
238 d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
239
240 d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
241
242 /* Following fields used only in sequential mode */
243
244 /* Pointers to derived tables (these workspaces have image lifespan) */
245 d_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
246 d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
247
248 /* Precalculated info set up by start_pass for use in decode_mcu: */
249
250 /* Pointers to derived tables to be used for each block within an MCU */
251 d_derived_tbl * dc_cur_tbls[D_MAX_BLOCKS_IN_MCU];
252 d_derived_tbl * ac_cur_tbls[D_MAX_BLOCKS_IN_MCU];
253 /* Whether we care about the DC and AC coefficient values for each block */
254 int coef_limit[D_MAX_BLOCKS_IN_MCU];
255 } huff_entropy_decoder;
256
257 typedef huff_entropy_decoder * huff_entropy_ptr;
258
259
260 static const int jpeg_zigzag_order[8][8] = {
261 { 0, 1, 5, 6, 14, 15, 27, 28 },
262 { 2, 4, 7, 13, 16, 26, 29, 42 },
263 { 3, 8, 12, 17, 25, 30, 41, 43 },
264 { 9, 11, 18, 24, 31, 40, 44, 53 },
265 { 10, 19, 23, 32, 39, 45, 52, 54 },
266 { 20, 22, 33, 38, 46, 51, 55, 60 },
267 { 21, 34, 37, 47, 50, 56, 59, 61 },
268 { 35, 36, 48, 49, 57, 58, 62, 63 }
269 };
270
271 static const int jpeg_zigzag_order7[7][7] = {
272 { 0, 1, 5, 6, 14, 15, 27 },
273 { 2, 4, 7, 13, 16, 26, 28 },
274 { 3, 8, 12, 17, 25, 29, 38 },
275 { 9, 11, 18, 24, 30, 37, 39 },
276 { 10, 19, 23, 31, 36, 40, 45 },
277 { 20, 22, 32, 35, 41, 44, 46 },
278 { 21, 33, 34, 42, 43, 47, 48 }
279 };
280
281 static const int jpeg_zigzag_order6[6][6] = {
282 { 0, 1, 5, 6, 14, 15 },
283 { 2, 4, 7, 13, 16, 25 },
284 { 3, 8, 12, 17, 24, 26 },
285 { 9, 11, 18, 23, 27, 32 },
286 { 10, 19, 22, 28, 31, 33 },
287 { 20, 21, 29, 30, 34, 35 }
288 };
289
290 static const int jpeg_zigzag_order5[5][5] = {
291 { 0, 1, 5, 6, 14 },
292 { 2, 4, 7, 13, 15 },
293 { 3, 8, 12, 16, 21 },
294 { 9, 11, 17, 20, 22 },
295 { 10, 18, 19, 23, 24 }
296 };
297
298 static const int jpeg_zigzag_order4[4][4] = {
299 { 0, 1, 5, 6 },
300 { 2, 4, 7, 12 },
301 { 3, 8, 11, 13 },
302 { 9, 10, 14, 15 }
303 };
304
305 static const int jpeg_zigzag_order3[3][3] = {
306 { 0, 1, 5 },
307 { 2, 4, 6 },
308 { 3, 7, 8 }
309 };
310
311 static const int jpeg_zigzag_order2[2][2] = {
312 { 0, 1 },
313 { 2, 3 }
314 };
315
316
317 /*
318 * Compute the derived values for a Huffman table.
319 * This routine also performs some validation checks on the table.
320 */
321
322 LOCAL(void)
323 jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno,
324 d_derived_tbl ** pdtbl)
325 {
326 JHUFF_TBL *htbl;
327 d_derived_tbl *dtbl;
328 int p, i, l, si, numsymbols;
329 int lookbits, ctr;
330 char huffsize[257];
331 unsigned int huffcode[257];
332 unsigned int code;
333
334 /* Note that huffsize[] and huffcode[] are filled in code-length order,
335 * paralleling the order of the symbols themselves in htbl->huffval[].
336 */
337
338 /* Find the input Huffman table */
339 if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
340 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
341 htbl =
342 isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
343 if (htbl == NULL)
344 htbl = jpeg_std_huff_table((j_common_ptr) cinfo, isDC, tblno);
345
346 /* Allocate a workspace if we haven't already done so. */
347 if (*pdtbl == NULL)
348 *pdtbl = (d_derived_tbl *) (*cinfo->mem->alloc_small)
349 ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(d_derived_tbl));
350 dtbl = *pdtbl;
351 dtbl->pub = htbl; /* fill in back link */
352
353 /* Figure C.1: make table of Huffman code length for each symbol */
354
355 p = 0;
356 for (l = 1; l <= 16; l++) {
357 i = (int) htbl->bits[l];
358 if (i < 0 || p + i > 256) /* protect against table overrun */
359 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
360 while (i--)
361 huffsize[p++] = (char) l;
362 }
363 huffsize[p] = 0;
364 numsymbols = p;
365
366 /* Figure C.2: generate the codes themselves */
367 /* We also validate that the counts represent a legal Huffman code tree. */
368
369 code = 0;
370 si = huffsize[0];
371 p = 0;
372 while (huffsize[p]) {
373 while (((int) huffsize[p]) == si) {
374 huffcode[p++] = code;
375 code++;
376 }
377 /* code is now 1 more than the last code used for codelength si; but
378 * it must still fit in si bits, since no code is allowed to be all ones.
379 */
380 if (((INT32) code) >= (((INT32) 1) << si))
381 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
382 code <<= 1;
383 si++;
384 }
385
386 /* Figure F.15: generate decoding tables for bit-sequential decoding */
387
388 p = 0;
389 for (l = 1; l <= 16; l++) {
390 if (htbl->bits[l]) {
391 /* valoffset[l] = huffval[] index of 1st symbol of code length l,
392 * minus the minimum code of length l
393 */
394 dtbl->valoffset[l] = (INT32) p - (INT32) huffcode[p];
395 p += htbl->bits[l];
396 dtbl->maxcode[l] = huffcode[p-1]; /* maximum code of length l */
397 } else {
398 dtbl->maxcode[l] = -1; /* -1 if no codes of this length */
399 }
400 }
401 dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */
402
403 /* Compute lookahead tables to speed up decoding.
404 * First we set all the table entries to 0, indicating "too long";
405 * then we iterate through the Huffman codes that are short enough and
406 * fill in all the entries that correspond to bit sequences starting
407 * with that code.
408 */
409
410 MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits));
411
412 p = 0;
413 for (l = 1; l <= HUFF_LOOKAHEAD; l++) {
414 for (i = 1; i <= (int) htbl->bits[l]; i++, p++) {
415 /* l = current code's length, p = its index in huffcode[] & huffval[]. */
416 /* Generate left-justified code followed by all possible bit sequences */
417 lookbits = huffcode[p] << (HUFF_LOOKAHEAD-l);
418 for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) {
419 dtbl->look_nbits[lookbits] = l;
420 dtbl->look_sym[lookbits] = htbl->huffval[p];
421 lookbits++;
422 }
423 }
424 }
425
426 /* Validate symbols as being reasonable.
427 * For AC tables, we make no check, but accept all byte values 0..255.
428 * For DC tables, we require the symbols to be in range 0..15.
429 * (Tighter bounds could be applied depending on the data depth and mode,
430 * but this is sufficient to ensure safe decoding.)
431 */
432 if (isDC) {
433 for (i = 0; i < numsymbols; i++) {
434 int sym = htbl->huffval[i];
435 if (sym < 0 || sym > 15)
436 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
437 }
438 }
439 }
440
441
442 /*
443 * Out-of-line code for bit fetching.
444 * Note: current values of get_buffer and bits_left are passed as parameters,
445 * but are returned in the corresponding fields of the state struct.
446 *
447 * On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width
448 * of get_buffer to be used. (On machines with wider words, an even larger
449 * buffer could be used.) However, on some machines 32-bit shifts are
450 * quite slow and take time proportional to the number of places shifted.
451 * (This is true with most PC compilers, for instance.) In this case it may
452 * be a win to set MIN_GET_BITS to the minimum value of 15. This reduces the
453 * average shift distance at the cost of more calls to jpeg_fill_bit_buffer.
454 */
455
456 #ifdef SLOW_SHIFT_32
457 #define MIN_GET_BITS 15 /* minimum allowable value */
458 #else
459 #define MIN_GET_BITS (BIT_BUF_SIZE-7)
460 #endif
461
462
463 LOCAL(boolean)
464 jpeg_fill_bit_buffer (bitread_working_state * state,
465 register bit_buf_type get_buffer, register int bits_left,
466 int nbits)
467 /* Load up the bit buffer to a depth of at least nbits */
468 {
469 /* Copy heavily used state fields into locals (hopefully registers) */
470 register const JOCTET * next_input_byte = state->next_input_byte;
471 register size_t bytes_in_buffer = state->bytes_in_buffer;
472 j_decompress_ptr cinfo = state->cinfo;
473
474 /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */
475 /* (It is assumed that no request will be for more than that many bits.) */
476 /* We fail to do so only if we hit a marker or are forced to suspend. */
477
478 if (cinfo->unread_marker == 0) { /* cannot advance past a marker */
479 while (bits_left < MIN_GET_BITS) {
480 register int c;
481
482 /* Attempt to read a byte */
483 if (bytes_in_buffer == 0) {
484 if (! (*cinfo->src->fill_input_buffer) (cinfo))
485 return FALSE;
486 next_input_byte = cinfo->src->next_input_byte;
487 bytes_in_buffer = cinfo->src->bytes_in_buffer;
488 }
489 bytes_in_buffer--;
490 c = GETJOCTET(*next_input_byte++);
491
492 /* If it's 0xFF, check and discard stuffed zero byte */
493 if (c == 0xFF) {
494 /* Loop here to discard any padding FF's on terminating marker,
495 * so that we can save a valid unread_marker value. NOTE: we will
496 * accept multiple FF's followed by a 0 as meaning a single FF data
497 * byte. This data pattern is not valid according to the standard.
498 */
499 do {
500 if (bytes_in_buffer == 0) {
501 if (! (*cinfo->src->fill_input_buffer) (cinfo))
502 return FALSE;
503 next_input_byte = cinfo->src->next_input_byte;
504 bytes_in_buffer = cinfo->src->bytes_in_buffer;
505 }
506 bytes_in_buffer--;
507 c = GETJOCTET(*next_input_byte++);
508 } while (c == 0xFF);
509
510 if (c == 0) {
511 /* Found FF/00, which represents an FF data byte */
512 c = 0xFF;
513 } else {
514 /* Oops, it's actually a marker indicating end of compressed data.
515 * Save the marker code for later use.
516 * Fine point: it might appear that we should save the marker into
517 * bitread working state, not straight into permanent state. But
518 * once we have hit a marker, we cannot need to suspend within the
519 * current MCU, because we will read no more bytes from the data
520 * source. So it is OK to update permanent state right away.
521 */
522 cinfo->unread_marker = c;
523 /* See if we need to insert some fake zero bits. */
524 goto no_more_bytes;
525 }
526 }
527
528 /* OK, load c into get_buffer */
529 get_buffer = (get_buffer << 8) | c;
530 bits_left += 8;
531 } /* end while */
532 } else {
533 no_more_bytes:
534 /* We get here if we've read the marker that terminates the compressed
535 * data segment. There should be enough bits in the buffer register
536 * to satisfy the request; if so, no problem.
537 */
538 if (nbits > bits_left) {
539 /* Uh-oh. Report corrupted data to user and stuff zeroes into
540 * the data stream, so that we can produce some kind of image.
541 * We use a nonvolatile flag to ensure that only one warning message
542 * appears per data segment.
543 */
544 if (! ((huff_entropy_ptr) cinfo->entropy)->insufficient_data) {
545 WARNMS(cinfo, JWRN_HIT_MARKER);
546 ((huff_entropy_ptr) cinfo->entropy)->insufficient_data = TRUE;
547 }
548 /* Fill the buffer with zero bits */
549 get_buffer <<= MIN_GET_BITS - bits_left;
550 bits_left = MIN_GET_BITS;
551 }
552 }
553
554 /* Unload the local registers */
555 state->next_input_byte = next_input_byte;
556 state->bytes_in_buffer = bytes_in_buffer;
557 state->get_buffer = get_buffer;
558 state->bits_left = bits_left;
559
560 return TRUE;
561 }
562
563
564 /*
565 * Figure F.12: extend sign bit.
566 * On some machines, a shift and sub will be faster than a table lookup.
567 */
568
569 #ifdef AVOID_TABLES
570
571 #define BIT_MASK(nbits) ((1<<(nbits))-1)
572 #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) - ((1<<(s))-1) : (x))
573
574 #else
575
576 #define BIT_MASK(nbits) bmask[nbits]
577 #define HUFF_EXTEND(x,s) ((x) <= bmask[(s) - 1] ? (x) - bmask[s] : (x))
578
579 static const int bmask[16] = /* bmask[n] is mask for n rightmost bits */
580 { 0, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF,
581 0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF };
582
583 #endif /* AVOID_TABLES */
584
585
586 /*
587 * Out-of-line code for Huffman code decoding.
588 */
589
590 LOCAL(int)
591 jpeg_huff_decode (bitread_working_state * state,
592 register bit_buf_type get_buffer, register int bits_left,
593 d_derived_tbl * htbl, int min_bits)
594 {
595 register int l = min_bits;
596 register INT32 code;
597
598 /* HUFF_DECODE has determined that the code is at least min_bits */
599 /* bits long, so fetch that many bits in one swoop. */
600
601 CHECK_BIT_BUFFER(*state, l, return -1);
602 code = GET_BITS(l);
603
604 /* Collect the rest of the Huffman code one bit at a time. */
605 /* This is per Figure F.16 in the JPEG spec. */
606
607 while (code > htbl->maxcode[l]) {
608 code <<= 1;
609 CHECK_BIT_BUFFER(*state, 1, return -1);
610 code |= GET_BITS(1);
611 l++;
612 }
613
614 /* Unload the local registers */
615 state->get_buffer = get_buffer;
616 state->bits_left = bits_left;
617
618 /* With garbage input we may reach the sentinel value l = 17. */
619
620 if (l > 16) {
621 WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
622 return 0; /* fake a zero as the safest result */
623 }
624
625 return htbl->pub->huffval[ (int) (code + htbl->valoffset[l]) ];
626 }
627
628
629 /*
630 * Finish up at the end of a Huffman-compressed scan.
631 */
632
633 METHODDEF(void)
634 finish_pass_huff (j_decompress_ptr cinfo)
635 {
636 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
637
638 /* Throw away any unused bits remaining in bit buffer; */
639 /* include any full bytes in next_marker's count of discarded bytes */
640 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
641 entropy->bitstate.bits_left = 0;
642 }
643
644
645 /*
646 * Check for a restart marker & resynchronize decoder.
647 * Returns FALSE if must suspend.
648 */
649
650 LOCAL(boolean)
651 process_restart (j_decompress_ptr cinfo)
652 {
653 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
654 int ci;
655
656 finish_pass_huff(cinfo);
657
658 /* Advance past the RSTn marker */
659 if (! (*cinfo->marker->read_restart_marker) (cinfo))
660 return FALSE;
661
662 /* Re-initialize DC predictions to 0 */
663 for (ci = 0; ci < cinfo->comps_in_scan; ci++)
664 entropy->saved.last_dc_val[ci] = 0;
665 /* Re-init EOB run count, too */
666 entropy->saved.EOBRUN = 0;
667
668 /* Reset restart counter */
669 entropy->restarts_to_go = cinfo->restart_interval;
670
671 /* Reset out-of-data flag, unless read_restart_marker left us smack up
672 * against a marker. In that case we will end up treating the next data
673 * segment as empty, and we can avoid producing bogus output pixels by
674 * leaving the flag set.
675 */
676 if (cinfo->unread_marker == 0)
677 entropy->insufficient_data = FALSE;
678
679 return TRUE;
680 }
681
682
683 /*
684 * Huffman MCU decoding.
685 * Each of these routines decodes and returns one MCU's worth of
686 * Huffman-compressed coefficients.
687 * The coefficients are reordered from zigzag order into natural array order,
688 * but are not dequantized.
689 *
690 * The i'th block of the MCU is stored into the block pointed to by
691 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
692 * (Wholesale zeroing is usually a little faster than retail...)
693 *
694 * We return FALSE if data source requested suspension. In that case no
695 * changes have been made to permanent state. (Exception: some output
696 * coefficients may already have been assigned. This is harmless for
697 * spectral selection, since we'll just re-assign them on the next call.
698 * Successive approximation AC refinement has to be more careful, however.)
699 */
700
701 /*
702 * MCU decoding for DC initial scan (either spectral selection,
703 * or first pass of successive approximation).
704 */
705
706 METHODDEF(boolean)
707 decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKARRAY MCU_data)
708 {
709 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
710 int Al = cinfo->Al;
711 register int s, r;
712 int blkn, ci;
713 JBLOCKROW block;
714 BITREAD_STATE_VARS;
715 savable_state state;
716 d_derived_tbl * tbl;
717 jpeg_component_info * compptr;
718
719 /* Process restart marker if needed; may have to suspend */
720 if (cinfo->restart_interval) {
721 if (entropy->restarts_to_go == 0)
722 if (! process_restart(cinfo))
723 return FALSE;
724 }
725
726 /* If we've run out of data, just leave the MCU set to zeroes.
727 * This way, we return uniform gray for the remainder of the segment.
728 */
729 if (! entropy->insufficient_data) {
730
731 /* Load up working state */
732 BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
733 ASSIGN_STATE(state, entropy->saved);
734
735 /* Outer loop handles each block in the MCU */
736
737 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
738 block = MCU_data[blkn];
739 ci = cinfo->MCU_membership[blkn];
740 compptr = cinfo->cur_comp_info[ci];
741 tbl = entropy->derived_tbls[compptr->dc_tbl_no];
742
743 /* Decode a single block's worth of coefficients */
744
745 /* Section F.2.2.1: decode the DC coefficient difference */
746 HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
747 if (s) {
748 CHECK_BIT_BUFFER(br_state, s, return FALSE);
749 r = GET_BITS(s);
750 s = HUFF_EXTEND(r, s);
751 }
752
753 /* Convert DC difference to actual value, update last_dc_val */
754 s += state.last_dc_val[ci];
755 state.last_dc_val[ci] = s;
756 /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
757 (*block)[0] = (JCOEF) (s << Al);
758 }
759
760 /* Completed MCU, so update state */
761 BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
762 ASSIGN_STATE(entropy->saved, state);
763 }
764
765 /* Account for restart interval if using restarts */
766 if (cinfo->restart_interval)
767 entropy->restarts_to_go--;
768
769 return TRUE;
770 }
771
772
773 /*
774 * MCU decoding for AC initial scan (either spectral selection,
775 * or first pass of successive approximation).
776 */
777
778 METHODDEF(boolean)
779 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKARRAY MCU_data)
780 {
781 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
782 register int s, k, r;
783 unsigned int EOBRUN;
784 int Se, Al;
785 const int * natural_order;
786 JBLOCKROW block;
787 BITREAD_STATE_VARS;
788 d_derived_tbl * tbl;
789
790 /* Process restart marker if needed; may have to suspend */
791 if (cinfo->restart_interval) {
792 if (entropy->restarts_to_go == 0)
793 if (! process_restart(cinfo))
794 return FALSE;
795 }
796
797 /* If we've run out of data, just leave the MCU set to zeroes.
798 * This way, we return uniform gray for the remainder of the segment.
799 */
800 if (! entropy->insufficient_data) {
801
802 /* Load up working state.
803 * We can avoid loading/saving bitread state if in an EOB run.
804 */
805 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
806
807 /* There is always only one block per MCU */
808
809 if (EOBRUN) /* if it's a band of zeroes... */
810 EOBRUN--; /* ...process it now (we do nothing) */
811 else {
812 BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
813 Se = cinfo->Se;
814 Al = cinfo->Al;
815 natural_order = cinfo->natural_order;
816 block = MCU_data[0];
817 tbl = entropy->ac_derived_tbl;
818
819 for (k = cinfo->Ss; k <= Se; k++) {
820 HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
821 r = s >> 4;
822 s &= 15;
823 if (s) {
824 k += r;
825 CHECK_BIT_BUFFER(br_state, s, return FALSE);
826 r = GET_BITS(s);
827 s = HUFF_EXTEND(r, s);
828 /* Scale and output coefficient in natural (dezigzagged) order */
829 (*block)[natural_order[k]] = (JCOEF) (s << Al);
830 } else {
831 if (r != 15) { /* EOBr, run length is 2^r + appended bits */
832 if (r) { /* EOBr, r > 0 */
833 EOBRUN = 1 << r;
834 CHECK_BIT_BUFFER(br_state, r, return FALSE);
835 r = GET_BITS(r);
836 EOBRUN += r;
837 EOBRUN--; /* this band is processed at this moment */
838 }
839 break; /* force end-of-band */
840 }
841 k += 15; /* ZRL: skip 15 zeroes in band */
842 }
843 }
844
845 BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
846 }
847
848 /* Completed MCU, so update state */
849 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
850 }
851
852 /* Account for restart interval if using restarts */
853 if (cinfo->restart_interval)
854 entropy->restarts_to_go--;
855
856 return TRUE;
857 }
858
859
860 /*
861 * MCU decoding for DC successive approximation refinement scan.
862 * Note: we assume such scans can be multi-component,
863 * although the spec is not very clear on the point.
864 */
865
866 METHODDEF(boolean)
867 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKARRAY MCU_data)
868 {
869 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
870 JCOEF p1;
871 int blkn;
872 BITREAD_STATE_VARS;
873
874 /* Process restart marker if needed; may have to suspend */
875 if (cinfo->restart_interval) {
876 if (entropy->restarts_to_go == 0)
877 if (! process_restart(cinfo))
878 return FALSE;
879 }
880
881 /* Not worth the cycles to check insufficient_data here,
882 * since we will not change the data anyway if we read zeroes.
883 */
884
885 /* Load up working state */
886 BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
887
888 p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
889
890 /* Outer loop handles each block in the MCU */
891
892 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
893 /* Encoded data is simply the next bit of the two's-complement DC value */
894 CHECK_BIT_BUFFER(br_state, 1, return FALSE);
895 if (GET_BITS(1))
896 MCU_data[blkn][0][0] |= p1;
897 /* Note: since we use |=, repeating the assignment later is safe */
898 }
899
900 /* Completed MCU, so update state */
901 BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
902
903 /* Account for restart interval if using restarts */
904 if (cinfo->restart_interval)
905 entropy->restarts_to_go--;
906
907 return TRUE;
908 }
909
910
911 /*
912 * MCU decoding for AC successive approximation refinement scan.
913 */
914
915 METHODDEF(boolean)
916 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKARRAY MCU_data)
917 {
918 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
919 register int s, k, r;
920 unsigned int EOBRUN;
921 int Se;
922 JCOEF p1, m1;
923 const int * natural_order;
924 JBLOCKROW block;
925 JCOEFPTR thiscoef;
926 BITREAD_STATE_VARS;
927 d_derived_tbl * tbl;
928 int num_newnz;
929 int newnz_pos[DCTSIZE2];
930
931 /* Process restart marker if needed; may have to suspend */
932 if (cinfo->restart_interval) {
933 if (entropy->restarts_to_go == 0)
934 if (! process_restart(cinfo))
935 return FALSE;
936 }
937
938 /* If we've run out of data, don't modify the MCU.
939 */
940 if (! entropy->insufficient_data) {
941
942 Se = cinfo->Se;
943 p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
944 m1 = -p1; /* -1 in the bit position being coded */
945 natural_order = cinfo->natural_order;
946
947 /* Load up working state */
948 BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
949 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
950
951 /* There is always only one block per MCU */
952 block = MCU_data[0];
953 tbl = entropy->ac_derived_tbl;
954
955 /* If we are forced to suspend, we must undo the assignments to any newly
956 * nonzero coefficients in the block, because otherwise we'd get confused
957 * next time about which coefficients were already nonzero.
958 * But we need not undo addition of bits to already-nonzero coefficients;
959 * instead, we can test the current bit to see if we already did it.
960 */
961 num_newnz = 0;
962
963 /* initialize coefficient loop counter to start of band */
964 k = cinfo->Ss;
965
966 if (EOBRUN == 0) {
967 do {
968 HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
969 r = s >> 4;
970 s &= 15;
971 if (s) {
972 if (s != 1) /* size of new coef should always be 1 */
973 WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
974 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
975 if (GET_BITS(1))
976 s = p1; /* newly nonzero coef is positive */
977 else
978 s = m1; /* newly nonzero coef is negative */
979 } else {
980 if (r != 15) {
981 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */
982 if (r) {
983 CHECK_BIT_BUFFER(br_state, r, goto undoit);
984 r = GET_BITS(r);
985 EOBRUN += r;
986 }
987 break; /* rest of block is handled by EOB logic */
988 }
989 /* note s = 0 for processing ZRL */
990 }
991 /* Advance over already-nonzero coefs and r still-zero coefs,
992 * appending correction bits to the nonzeroes. A correction bit is 1
993 * if the absolute value of the coefficient must be increased.
994 */
995 do {
996 thiscoef = *block + natural_order[k];
997 if (*thiscoef) {
998 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
999 if (GET_BITS(1)) {
1000 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
1001 if (*thiscoef >= 0)
1002 *thiscoef += p1;
1003 else
1004 *thiscoef += m1;
1005 }
1006 }
1007 } else {
1008 if (--r < 0)
1009 break; /* reached target zero coefficient */
1010 }
1011 k++;
1012 } while (k <= Se);
1013 if (s) {
1014 int pos = natural_order[k];
1015 /* Output newly nonzero coefficient */
1016 (*block)[pos] = (JCOEF) s;
1017 /* Remember its position in case we have to suspend */
1018 newnz_pos[num_newnz++] = pos;
1019 }
1020 k++;
1021 } while (k <= Se);
1022 }
1023
1024 if (EOBRUN) {
1025 /* Scan any remaining coefficient positions after the end-of-band
1026 * (the last newly nonzero coefficient, if any). Append a correction
1027 * bit to each already-nonzero coefficient. A correction bit is 1
1028 * if the absolute value of the coefficient must be increased.
1029 */
1030 do {
1031 thiscoef = *block + natural_order[k];
1032 if (*thiscoef) {
1033 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
1034 if (GET_BITS(1)) {
1035 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
1036 if (*thiscoef >= 0)
1037 *thiscoef += p1;
1038 else
1039 *thiscoef += m1;
1040 }
1041 }
1042 }
1043 k++;
1044 } while (k <= Se);
1045 /* Count one block completed in EOB run */
1046 EOBRUN--;
1047 }
1048
1049 /* Completed MCU, so update state */
1050 BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
1051 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
1052 }
1053
1054 /* Account for restart interval if using restarts */
1055 if (cinfo->restart_interval)
1056 entropy->restarts_to_go--;
1057
1058 return TRUE;
1059
1060 undoit:
1061 /* Re-zero any output coefficients that we made newly nonzero */
1062 while (num_newnz)
1063 (*block)[newnz_pos[--num_newnz]] = 0;
1064
1065 return FALSE;
1066 }
1067
1068
1069 /*
1070 * Decode one MCU's worth of Huffman-compressed coefficients,
1071 * partial blocks.
1072 */
1073
1074 METHODDEF(boolean)
1075 decode_mcu_sub (j_decompress_ptr cinfo, JBLOCKARRAY MCU_data)
1076 {
1077 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1078 const int * natural_order;
1079 int Se, blkn;
1080 BITREAD_STATE_VARS;
1081 savable_state state;
1082
1083 /* Process restart marker if needed; may have to suspend */
1084 if (cinfo->restart_interval) {
1085 if (entropy->restarts_to_go == 0)
1086 if (! process_restart(cinfo))
1087 return FALSE;
1088 }
1089
1090 /* If we've run out of data, just leave the MCU set to zeroes.
1091 * This way, we return uniform gray for the remainder of the segment.
1092 */
1093 if (! entropy->insufficient_data) {
1094
1095 natural_order = cinfo->natural_order;
1096 Se = cinfo->lim_Se;
1097
1098 /* Load up working state */
1099 BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
1100 ASSIGN_STATE(state, entropy->saved);
1101
1102 /* Outer loop handles each block in the MCU */
1103
1104 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1105 JBLOCKROW block = MCU_data[blkn];
1106 d_derived_tbl * htbl;
1107 register int s, k, r;
1108 int coef_limit, ci;
1109
1110 /* Decode a single block's worth of coefficients */
1111
1112 /* Section F.2.2.1: decode the DC coefficient difference */
1113 htbl = entropy->dc_cur_tbls[blkn];
1114 HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1115
1116 htbl = entropy->ac_cur_tbls[blkn];
1117 k = 1;
1118 coef_limit = entropy->coef_limit[blkn];
1119 if (coef_limit) {
1120 /* Convert DC difference to actual value, update last_dc_val */
1121 if (s) {
1122 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1123 r = GET_BITS(s);
1124 s = HUFF_EXTEND(r, s);
1125 }
1126 ci = cinfo->MCU_membership[blkn];
1127 s += state.last_dc_val[ci];
1128 state.last_dc_val[ci] = s;
1129 /* Output the DC coefficient */
1130 (*block)[0] = (JCOEF) s;
1131
1132 /* Section F.2.2.2: decode the AC coefficients */
1133 /* Since zeroes are skipped, output area must be cleared beforehand */
1134 for (; k < coef_limit; k++) {
1135 HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
1136
1137 r = s >> 4;
1138 s &= 15;
1139
1140 if (s) {
1141 k += r;
1142 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1143 r = GET_BITS(s);
1144 s = HUFF_EXTEND(r, s);
1145 /* Output coefficient in natural (dezigzagged) order.
1146 * Note: the extra entries in natural_order[] will save us
1147 * if k > Se, which could happen if the data is corrupted.
1148 */
1149 (*block)[natural_order[k]] = (JCOEF) s;
1150 } else {
1151 if (r != 15)
1152 goto EndOfBlock;
1153 k += 15;
1154 }
1155 }
1156 } else {
1157 if (s) {
1158 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1159 DROP_BITS(s);
1160 }
1161 }
1162
1163 /* Section F.2.2.2: decode the AC coefficients */
1164 /* In this path we just discard the values */
1165 for (; k <= Se; k++) {
1166 HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
1167
1168 r = s >> 4;
1169 s &= 15;
1170
1171 if (s) {
1172 k += r;
1173 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1174 DROP_BITS(s);
1175 } else {
1176 if (r != 15)
1177 break;
1178 k += 15;
1179 }
1180 }
1181
1182 EndOfBlock: ;
1183 }
1184
1185 /* Completed MCU, so update state */
1186 BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
1187 ASSIGN_STATE(entropy->saved, state);
1188 }
1189
1190 /* Account for restart interval if using restarts */
1191 if (cinfo->restart_interval)
1192 entropy->restarts_to_go--;
1193
1194 return TRUE;
1195 }
1196
1197
1198 /*
1199 * Decode one MCU's worth of Huffman-compressed coefficients,
1200 * full-size blocks.
1201 */
1202
1203 METHODDEF(boolean)
1204 decode_mcu (j_decompress_ptr cinfo, JBLOCKARRAY MCU_data)
1205 {
1206 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1207 int blkn;
1208 BITREAD_STATE_VARS;
1209 savable_state state;
1210
1211 /* Process restart marker if needed; may have to suspend */
1212 if (cinfo->restart_interval) {
1213 if (entropy->restarts_to_go == 0)
1214 if (! process_restart(cinfo))
1215 return FALSE;
1216 }
1217
1218 /* If we've run out of data, just leave the MCU set to zeroes.
1219 * This way, we return uniform gray for the remainder of the segment.
1220 */
1221 if (! entropy->insufficient_data) {
1222
1223 /* Load up working state */
1224 BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
1225 ASSIGN_STATE(state, entropy->saved);
1226
1227 /* Outer loop handles each block in the MCU */
1228
1229 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1230 JBLOCKROW block = MCU_data[blkn];
1231 d_derived_tbl * htbl;
1232 register int s, k, r;
1233 int coef_limit, ci;
1234
1235 /* Decode a single block's worth of coefficients */
1236
1237 /* Section F.2.2.1: decode the DC coefficient difference */
1238 htbl = entropy->dc_cur_tbls[blkn];
1239 HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1240
1241 htbl = entropy->ac_cur_tbls[blkn];
1242 k = 1;
1243 coef_limit = entropy->coef_limit[blkn];
1244 if (coef_limit) {
1245 /* Convert DC difference to actual value, update last_dc_val */
1246 if (s) {
1247 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1248 r = GET_BITS(s);
1249 s = HUFF_EXTEND(r, s);
1250 }
1251 ci = cinfo->MCU_membership[blkn];
1252 s += state.last_dc_val[ci];
1253 state.last_dc_val[ci] = s;
1254 /* Output the DC coefficient */
1255 (*block)[0] = (JCOEF) s;
1256
1257 /* Section F.2.2.2: decode the AC coefficients */
1258 /* Since zeroes are skipped, output area must be cleared beforehand */
1259 for (; k < coef_limit; k++) {
1260 HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
1261
1262 r = s >> 4;
1263 s &= 15;
1264
1265 if (s) {
1266 k += r;
1267 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1268 r = GET_BITS(s);
1269 s = HUFF_EXTEND(r, s);
1270 /* Output coefficient in natural (dezigzagged) order.
1271 * Note: the extra entries in jpeg_natural_order[] will save us
1272 * if k >= DCTSIZE2, which could happen if the data is corrupted.
1273 */
1274 (*block)[jpeg_natural_order[k]] = (JCOEF) s;
1275 } else {
1276 if (r != 15)
1277 goto EndOfBlock;
1278 k += 15;
1279 }
1280 }
1281 } else {
1282 if (s) {
1283 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1284 DROP_BITS(s);
1285 }
1286 }
1287
1288 /* Section F.2.2.2: decode the AC coefficients */
1289 /* In this path we just discard the values */
1290 for (; k < DCTSIZE2; k++) {
1291 HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
1292
1293 r = s >> 4;
1294 s &= 15;
1295
1296 if (s) {
1297 k += r;
1298 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1299 DROP_BITS(s);
1300 } else {
1301 if (r != 15)
1302 break;
1303 k += 15;
1304 }
1305 }
1306
1307 EndOfBlock: ;
1308 }
1309
1310 /* Completed MCU, so update state */
1311 BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
1312 ASSIGN_STATE(entropy->saved, state);
1313 }
1314
1315 /* Account for restart interval if using restarts */
1316 if (cinfo->restart_interval)
1317 entropy->restarts_to_go--;
1318
1319 return TRUE;
1320 }
1321
1322
1323 /*
1324 * Initialize for a Huffman-compressed scan.
1325 */
1326
1327 METHODDEF(void)
1328 start_pass_huff_decoder (j_decompress_ptr cinfo)
1329 {
1330 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1331 int ci, blkn, tbl, i;
1332 jpeg_component_info * compptr;
1333
1334 if (cinfo->progressive_mode) {
1335 /* Validate progressive scan parameters */
1336 if (cinfo->Ss == 0) {
1337 if (cinfo->Se != 0)
1338 goto bad;
1339 } else {
1340 /* need not check Ss/Se < 0 since they came from unsigned bytes */
1341 if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se)
1342 goto bad;
1343 /* AC scans may have only one component */
1344 if (cinfo->comps_in_scan != 1)
1345 goto bad;
1346 }
1347 if (cinfo->Ah != 0) {
1348 /* Successive approximation refinement scan: must have Al = Ah-1. */
1349 if (cinfo->Ah-1 != cinfo->Al)
1350 goto bad;
1351 }
1352 if (cinfo->Al > 13) { /* need not check for < 0 */
1353 /* Arguably the maximum Al value should be less than 13 for 8-bit
1354 * precision, but the spec doesn't say so, and we try to be liberal
1355 * about what we accept. Note: large Al values could result in
1356 * out-of-range DC coefficients during early scans, leading to bizarre
1357 * displays due to overflows in the IDCT math. But we won't crash.
1358 */
1359 bad:
1360 ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
1361 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
1362 }
1363 /* Update progression status, and verify that scan order is legal.
1364 * Note that inter-scan inconsistencies are treated as warnings
1365 * not fatal errors ... not clear if this is right way to behave.
1366 */
1367 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1368 int coefi, cindex = cinfo->cur_comp_info[ci]->component_index;
1369 int *coef_bit_ptr = & cinfo->coef_bits[cindex][0];
1370 if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
1371 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
1372 for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
1373 int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
1374 if (cinfo->Ah != expected)
1375 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
1376 coef_bit_ptr[coefi] = cinfo->Al;
1377 }
1378 }
1379
1380 /* Select MCU decoding routine */
1381 if (cinfo->Ah == 0) {
1382 if (cinfo->Ss == 0)
1383 entropy->pub.decode_mcu = decode_mcu_DC_first;
1384 else
1385 entropy->pub.decode_mcu = decode_mcu_AC_first;
1386 } else {
1387 if (cinfo->Ss == 0)
1388 entropy->pub.decode_mcu = decode_mcu_DC_refine;
1389 else
1390 entropy->pub.decode_mcu = decode_mcu_AC_refine;
1391 }
1392
1393 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1394 compptr = cinfo->cur_comp_info[ci];
1395 /* Make sure requested tables are present, and compute derived tables.
1396 * We may build same derived table more than once, but it's not expensive.
1397 */
1398 if (cinfo->Ss == 0) {
1399 if (cinfo->Ah == 0) { /* DC refinement needs no table */
1400 tbl = compptr->dc_tbl_no;
1401 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
1402 & entropy->derived_tbls[tbl]);
1403 }
1404 } else {
1405 tbl = compptr->ac_tbl_no;
1406 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
1407 & entropy->derived_tbls[tbl]);
1408 /* remember the single active table */
1409 entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
1410 }
1411 /* Initialize DC predictions to 0 */
1412 entropy->saved.last_dc_val[ci] = 0;
1413 }
1414
1415 /* Initialize private state variables */
1416 entropy->saved.EOBRUN = 0;
1417 } else {
1418 /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
1419 * This ought to be an error condition, but we make it a warning because
1420 * there are some baseline files out there with all zeroes in these bytes.
1421 */
1422 if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||
1423 ((cinfo->is_baseline || cinfo->Se < DCTSIZE2) &&
1424 cinfo->Se != cinfo->lim_Se))
1425 WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
1426
1427 /* Select MCU decoding routine */
1428 /* We retain the hard-coded case for full-size blocks.
1429 * This is not necessary, but it appears that this version is slightly
1430 * more performant in the given implementation.
1431 * With an improved implementation we would prefer a single optimized
1432 * function.
1433 */
1434 if (cinfo->lim_Se != DCTSIZE2-1)
1435 entropy->pub.decode_mcu = decode_mcu_sub;
1436 else
1437 entropy->pub.decode_mcu = decode_mcu;
1438
1439 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1440 compptr = cinfo->cur_comp_info[ci];
1441 /* Compute derived values for Huffman tables */
1442 /* We may do this more than once for a table, but it's not expensive */
1443 tbl = compptr->dc_tbl_no;
1444 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
1445 & entropy->dc_derived_tbls[tbl]);
1446 if (cinfo->lim_Se) { /* AC needs no table when not present */
1447 tbl = compptr->ac_tbl_no;
1448 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
1449 & entropy->ac_derived_tbls[tbl]);
1450 }
1451 /* Initialize DC predictions to 0 */
1452 entropy->saved.last_dc_val[ci] = 0;
1453 }
1454
1455 /* Precalculate decoding info for each block in an MCU of this scan */
1456 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1457 ci = cinfo->MCU_membership[blkn];
1458 compptr = cinfo->cur_comp_info[ci];
1459 /* Precalculate which table to use for each block */
1460 entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no];
1461 entropy->ac_cur_tbls[blkn] = /* AC needs no table when not present */
1462 cinfo->lim_Se ? entropy->ac_derived_tbls[compptr->ac_tbl_no] : NULL;
1463 /* Decide whether we really care about the coefficient values */
1464 if (compptr->component_needed) {
1465 ci = compptr->DCT_v_scaled_size;
1466 i = compptr->DCT_h_scaled_size;
1467 switch (cinfo->lim_Se) {
1468 case (1*1-1):
1469 entropy->coef_limit[blkn] = 1;
1470 break;
1471 case (2*2-1):
1472 if (ci <= 0 || ci > 2) ci = 2;
1473 if (i <= 0 || i > 2) i = 2;
1474 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order2[ci - 1][i - 1];
1475 break;
1476 case (3*3-1):
1477 if (ci <= 0 || ci > 3) ci = 3;
1478 if (i <= 0 || i > 3) i = 3;
1479 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order3[ci - 1][i - 1];
1480 break;
1481 case (4*4-1):
1482 if (ci <= 0 || ci > 4) ci = 4;
1483 if (i <= 0 || i > 4) i = 4;
1484 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order4[ci - 1][i - 1];
1485 break;
1486 case (5*5-1):
1487 if (ci <= 0 || ci > 5) ci = 5;
1488 if (i <= 0 || i > 5) i = 5;
1489 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order5[ci - 1][i - 1];
1490 break;
1491 case (6*6-1):
1492 if (ci <= 0 || ci > 6) ci = 6;
1493 if (i <= 0 || i > 6) i = 6;
1494 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order6[ci - 1][i - 1];
1495 break;
1496 case (7*7-1):
1497 if (ci <= 0 || ci > 7) ci = 7;
1498 if (i <= 0 || i > 7) i = 7;
1499 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order7[ci - 1][i - 1];
1500 break;
1501 default:
1502 if (ci <= 0 || ci > 8) ci = 8;
1503 if (i <= 0 || i > 8) i = 8;
1504 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1];
1505 }
1506 } else {
1507 entropy->coef_limit[blkn] = 0;
1508 }
1509 }
1510 }
1511
1512 /* Initialize bitread state variables */
1513 entropy->bitstate.bits_left = 0;
1514 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
1515 entropy->insufficient_data = FALSE;
1516
1517 /* Initialize restart counter */
1518 entropy->restarts_to_go = cinfo->restart_interval;
1519 }
1520
1521
1522 /*
1523 * Module initialization routine for Huffman entropy decoding.
1524 */
1525
1526 GLOBAL(void)
1527 jinit_huff_decoder (j_decompress_ptr cinfo)
1528 {
1529 huff_entropy_ptr entropy;
1530 int i;
1531
1532 entropy = (huff_entropy_ptr) (*cinfo->mem->alloc_small)
1533 ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(huff_entropy_decoder));
1534 cinfo->entropy = &entropy->pub;
1535 entropy->pub.start_pass = start_pass_huff_decoder;
1536 entropy->pub.finish_pass = finish_pass_huff;
1537
1538 if (cinfo->progressive_mode) {
1539 /* Create progression status table */
1540 int *coef_bit_ptr, ci;
1541 cinfo->coef_bits = (int (*)[DCTSIZE2]) (*cinfo->mem->alloc_small)
1542 ((j_common_ptr) cinfo, JPOOL_IMAGE,
1543 cinfo->num_components * DCTSIZE2 * SIZEOF(int));
1544 coef_bit_ptr = & cinfo->coef_bits[0][0];
1545 for (ci = 0; ci < cinfo->num_components; ci++)
1546 for (i = 0; i < DCTSIZE2; i++)
1547 *coef_bit_ptr++ = -1;
1548
1549 /* Mark derived tables unallocated */
1550 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1551 entropy->derived_tbls[i] = NULL;
1552 }
1553 } else {
1554 /* Mark derived tables unallocated */
1555 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1556 entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
1557 }
1558 }
1559 }