1 /*
2 * jdhuff.c
3 *
4 * Copyright (C) 1991-1997, Thomas G. Lane.
5 * Modified 2006-2016 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)
jpeg_make_d_derived_tbl(j_decompress_ptr cinfo,boolean isDC,int tblno,d_derived_tbl ** pdtbl)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 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
345
346 /* Allocate a workspace if we haven't already done so. */
347 if (*pdtbl == NULL)
348 *pdtbl = (d_derived_tbl *)
349 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
350 SIZEOF(d_derived_tbl));
351 dtbl = *pdtbl;
352 dtbl->pub = htbl; /* fill in back link */
353
354 /* Figure C.1: make table of Huffman code length for each symbol */
355
356 p = 0;
357 for (l = 1; l <= 16; l++) {
358 i = (int) htbl->bits[l];
359 if (i < 0 || p + i > 256) /* protect against table overrun */
360 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
361 while (i--)
362 huffsize[p++] = (char) l;
363 }
364 huffsize[p] = 0;
365 numsymbols = p;
366
367 /* Figure C.2: generate the codes themselves */
368 /* We also validate that the counts represent a legal Huffman code tree. */
369
370 code = 0;
371 si = huffsize[0];
372 p = 0;
373 while (huffsize[p]) {
374 while (((int) huffsize[p]) == si) {
375 huffcode[p++] = code;
376 code++;
377 }
378 /* code is now 1 more than the last code used for codelength si; but
379 * it must still fit in si bits, since no code is allowed to be all ones.
380 */
381 if (((INT32) code) >= (((INT32) 1) << si))
382 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
383 code <<= 1;
384 si++;
385 }
386
387 /* Figure F.15: generate decoding tables for bit-sequential decoding */
388
389 p = 0;
390 for (l = 1; l <= 16; l++) {
391 if (htbl->bits[l]) {
392 /* valoffset[l] = huffval[] index of 1st symbol of code length l,
393 * minus the minimum code of length l
394 */
395 dtbl->valoffset[l] = (INT32) p - (INT32) huffcode[p];
396 p += htbl->bits[l];
397 dtbl->maxcode[l] = huffcode[p-1]; /* maximum code of length l */
398 } else {
399 dtbl->maxcode[l] = -1; /* -1 if no codes of this length */
400 }
401 }
402 dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */
403
404 /* Compute lookahead tables to speed up decoding.
405 * First we set all the table entries to 0, indicating "too long";
406 * then we iterate through the Huffman codes that are short enough and
407 * fill in all the entries that correspond to bit sequences starting
408 * with that code.
409 */
410
411 MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits));
412
413 p = 0;
414 for (l = 1; l <= HUFF_LOOKAHEAD; l++) {
415 for (i = 1; i <= (int) htbl->bits[l]; i++, p++) {
416 /* l = current code's length, p = its index in huffcode[] & huffval[]. */
417 /* Generate left-justified code followed by all possible bit sequences */
418 lookbits = huffcode[p] << (HUFF_LOOKAHEAD-l);
419 for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) {
420 dtbl->look_nbits[lookbits] = l;
421 dtbl->look_sym[lookbits] = htbl->huffval[p];
422 lookbits++;
423 }
424 }
425 }
426
427 /* Validate symbols as being reasonable.
428 * For AC tables, we make no check, but accept all byte values 0..255.
429 * For DC tables, we require the symbols to be in range 0..15.
430 * (Tighter bounds could be applied depending on the data depth and mode,
431 * but this is sufficient to ensure safe decoding.)
432 */
433 if (isDC) {
434 for (i = 0; i < numsymbols; i++) {
435 int sym = htbl->huffval[i];
436 if (sym < 0 || sym > 15)
437 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
438 }
439 }
440 }
441
442
443 /*
444 * Out-of-line code for bit fetching.
445 * Note: current values of get_buffer and bits_left are passed as parameters,
446 * but are returned in the corresponding fields of the state struct.
447 *
448 * On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width
449 * of get_buffer to be used. (On machines with wider words, an even larger
450 * buffer could be used.) However, on some machines 32-bit shifts are
451 * quite slow and take time proportional to the number of places shifted.
452 * (This is true with most PC compilers, for instance.) In this case it may
453 * be a win to set MIN_GET_BITS to the minimum value of 15. This reduces the
454 * average shift distance at the cost of more calls to jpeg_fill_bit_buffer.
455 */
456
457 #ifdef SLOW_SHIFT_32
458 #define MIN_GET_BITS 15 /* minimum allowable value */
459 #else
460 #define MIN_GET_BITS (BIT_BUF_SIZE-7)
461 #endif
462
463
464 LOCAL(boolean)
jpeg_fill_bit_buffer(bitread_working_state * state,register bit_buf_type get_buffer,register int bits_left,int nbits)465 jpeg_fill_bit_buffer (bitread_working_state * state,
466 register bit_buf_type get_buffer, register int bits_left,
467 int nbits)
468 /* Load up the bit buffer to a depth of at least nbits */
469 {
470 /* Copy heavily used state fields into locals (hopefully registers) */
471 register const JOCTET * next_input_byte = state->next_input_byte;
472 register size_t bytes_in_buffer = state->bytes_in_buffer;
473 j_decompress_ptr cinfo = state->cinfo;
474
475 /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */
476 /* (It is assumed that no request will be for more than that many bits.) */
477 /* We fail to do so only if we hit a marker or are forced to suspend. */
478
479 if (cinfo->unread_marker == 0) { /* cannot advance past a marker */
480 while (bits_left < MIN_GET_BITS) {
481 register int c;
482
483 /* Attempt to read a byte */
484 if (bytes_in_buffer == 0) {
485 if (! (*cinfo->src->fill_input_buffer) (cinfo))
486 return FALSE;
487 next_input_byte = cinfo->src->next_input_byte;
488 bytes_in_buffer = cinfo->src->bytes_in_buffer;
489 }
490 bytes_in_buffer--;
491 c = GETJOCTET(*next_input_byte++);
492
493 /* If it's 0xFF, check and discard stuffed zero byte */
494 if (c == 0xFF) {
495 /* Loop here to discard any padding FF's on terminating marker,
496 * so that we can save a valid unread_marker value. NOTE: we will
497 * accept multiple FF's followed by a 0 as meaning a single FF data
498 * byte. This data pattern is not valid according to the standard.
499 */
500 do {
501 if (bytes_in_buffer == 0) {
502 if (! (*cinfo->src->fill_input_buffer) (cinfo))
503 return FALSE;
504 next_input_byte = cinfo->src->next_input_byte;
505 bytes_in_buffer = cinfo->src->bytes_in_buffer;
506 }
507 bytes_in_buffer--;
508 c = GETJOCTET(*next_input_byte++);
509 } while (c == 0xFF);
510
511 if (c == 0) {
512 /* Found FF/00, which represents an FF data byte */
513 c = 0xFF;
514 } else {
515 /* Oops, it's actually a marker indicating end of compressed data.
516 * Save the marker code for later use.
517 * Fine point: it might appear that we should save the marker into
518 * bitread working state, not straight into permanent state. But
519 * once we have hit a marker, we cannot need to suspend within the
520 * current MCU, because we will read no more bytes from the data
521 * source. So it is OK to update permanent state right away.
522 */
523 cinfo->unread_marker = c;
524 /* See if we need to insert some fake zero bits. */
525 goto no_more_bytes;
526 }
527 }
528
529 /* OK, load c into get_buffer */
530 get_buffer = (get_buffer << 8) | c;
531 bits_left += 8;
532 } /* end while */
533 } else {
534 no_more_bytes:
535 /* We get here if we've read the marker that terminates the compressed
536 * data segment. There should be enough bits in the buffer register
537 * to satisfy the request; if so, no problem.
538 */
539 if (nbits > bits_left) {
540 /* Uh-oh. Report corrupted data to user and stuff zeroes into
541 * the data stream, so that we can produce some kind of image.
542 * We use a nonvolatile flag to ensure that only one warning message
543 * appears per data segment.
544 */
545 if (! ((huff_entropy_ptr) cinfo->entropy)->insufficient_data) {
546 WARNMS(cinfo, JWRN_HIT_MARKER);
547 ((huff_entropy_ptr) cinfo->entropy)->insufficient_data = TRUE;
548 }
549 /* Fill the buffer with zero bits */
550 get_buffer <<= MIN_GET_BITS - bits_left;
551 bits_left = MIN_GET_BITS;
552 }
553 }
554
555 /* Unload the local registers */
556 state->next_input_byte = next_input_byte;
557 state->bytes_in_buffer = bytes_in_buffer;
558 state->get_buffer = get_buffer;
559 state->bits_left = bits_left;
560
561 return TRUE;
562 }
563
564
565 /*
566 * Figure F.12: extend sign bit.
567 * On some machines, a shift and sub will be faster than a table lookup.
568 */
569
570 #ifdef AVOID_TABLES
571
572 #define BIT_MASK(nbits) ((1<<(nbits))-1)
573 #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) - ((1<<(s))-1) : (x))
574
575 #else
576
577 #define BIT_MASK(nbits) bmask[nbits]
578 #define HUFF_EXTEND(x,s) ((x) <= bmask[(s) - 1] ? (x) - bmask[s] : (x))
579
580 static const int bmask[16] = /* bmask[n] is mask for n rightmost bits */
581 { 0, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF,
582 0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF };
583
584 #endif /* AVOID_TABLES */
585
586
587 /*
588 * Out-of-line code for Huffman code decoding.
589 */
590
591 LOCAL(int)
jpeg_huff_decode(bitread_working_state * state,register bit_buf_type get_buffer,register int bits_left,d_derived_tbl * htbl,int min_bits)592 jpeg_huff_decode (bitread_working_state * state,
593 register bit_buf_type get_buffer, register int bits_left,
594 d_derived_tbl * htbl, int min_bits)
595 {
596 register int l = min_bits;
597 register INT32 code;
598
599 /* HUFF_DECODE has determined that the code is at least min_bits */
600 /* bits long, so fetch that many bits in one swoop. */
601
602 CHECK_BIT_BUFFER(*state, l, return -1);
603 code = GET_BITS(l);
604
605 /* Collect the rest of the Huffman code one bit at a time. */
606 /* This is per Figure F.16 in the JPEG spec. */
607
608 while (code > htbl->maxcode[l]) {
609 code <<= 1;
610 CHECK_BIT_BUFFER(*state, 1, return -1);
611 code |= GET_BITS(1);
612 l++;
613 }
614
615 /* Unload the local registers */
616 state->get_buffer = get_buffer;
617 state->bits_left = bits_left;
618
619 /* With garbage input we may reach the sentinel value l = 17. */
620
621 if (l > 16) {
622 WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
623 return 0; /* fake a zero as the safest result */
624 }
625
626 return htbl->pub->huffval[ (int) (code + htbl->valoffset[l]) ];
627 }
628
629
630 /*
631 * Finish up at the end of a Huffman-compressed scan.
632 */
633
634 METHODDEF(void)
finish_pass_huff(j_decompress_ptr cinfo)635 finish_pass_huff (j_decompress_ptr cinfo)
636 {
637 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
638
639 /* Throw away any unused bits remaining in bit buffer; */
640 /* include any full bytes in next_marker's count of discarded bytes */
641 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
642 entropy->bitstate.bits_left = 0;
643 }
644
645
646 /*
647 * Check for a restart marker & resynchronize decoder.
648 * Returns FALSE if must suspend.
649 */
650
651 LOCAL(boolean)
process_restart(j_decompress_ptr cinfo)652 process_restart (j_decompress_ptr cinfo)
653 {
654 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
655 int ci;
656
657 finish_pass_huff(cinfo);
658
659 /* Advance past the RSTn marker */
660 if (! (*cinfo->marker->read_restart_marker) (cinfo))
661 return FALSE;
662
663 /* Re-initialize DC predictions to 0 */
664 for (ci = 0; ci < cinfo->comps_in_scan; ci++)
665 entropy->saved.last_dc_val[ci] = 0;
666 /* Re-init EOB run count, too */
667 entropy->saved.EOBRUN = 0;
668
669 /* Reset restart counter */
670 entropy->restarts_to_go = cinfo->restart_interval;
671
672 /* Reset out-of-data flag, unless read_restart_marker left us smack up
673 * against a marker. In that case we will end up treating the next data
674 * segment as empty, and we can avoid producing bogus output pixels by
675 * leaving the flag set.
676 */
677 if (cinfo->unread_marker == 0)
678 entropy->insufficient_data = FALSE;
679
680 return TRUE;
681 }
682
683
684 /*
685 * Huffman MCU decoding.
686 * Each of these routines decodes and returns one MCU's worth of
687 * Huffman-compressed coefficients.
688 * The coefficients are reordered from zigzag order into natural array order,
689 * but are not dequantized.
690 *
691 * The i'th block of the MCU is stored into the block pointed to by
692 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
693 * (Wholesale zeroing is usually a little faster than retail...)
694 *
695 * We return FALSE if data source requested suspension. In that case no
696 * changes have been made to permanent state. (Exception: some output
697 * coefficients may already have been assigned. This is harmless for
698 * spectral selection, since we'll just re-assign them on the next call.
699 * Successive approximation AC refinement has to be more careful, however.)
700 */
701
702 /*
703 * MCU decoding for DC initial scan (either spectral selection,
704 * or first pass of successive approximation).
705 */
706
707 METHODDEF(boolean)
decode_mcu_DC_first(j_decompress_ptr cinfo,JBLOCKROW * MCU_data)708 decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
709 {
710 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
711 int Al = cinfo->Al;
712 register int s, r;
713 int blkn, ci;
714 JBLOCKROW block;
715 BITREAD_STATE_VARS;
716 savable_state state;
717 d_derived_tbl * tbl;
718 jpeg_component_info * compptr;
719
720 /* Process restart marker if needed; may have to suspend */
721 if (cinfo->restart_interval) {
722 if (entropy->restarts_to_go == 0)
723 if (! process_restart(cinfo))
724 return FALSE;
725 }
726
727 /* If we've run out of data, just leave the MCU set to zeroes.
728 * This way, we return uniform gray for the remainder of the segment.
729 */
730 if (! entropy->insufficient_data) {
731
732 /* Load up working state */
733 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
734 ASSIGN_STATE(state, entropy->saved);
735
736 /* Outer loop handles each block in the MCU */
737
738 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
739 block = MCU_data[blkn];
740 ci = cinfo->MCU_membership[blkn];
741 compptr = cinfo->cur_comp_info[ci];
742 tbl = entropy->derived_tbls[compptr->dc_tbl_no];
743
744 /* Decode a single block's worth of coefficients */
745
746 /* Section F.2.2.1: decode the DC coefficient difference */
747 HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
748 if (s) {
749 CHECK_BIT_BUFFER(br_state, s, return FALSE);
750 r = GET_BITS(s);
751 s = HUFF_EXTEND(r, s);
752 }
753
754 /* Convert DC difference to actual value, update last_dc_val */
755 s += state.last_dc_val[ci];
756 state.last_dc_val[ci] = s;
757 /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
758 (*block)[0] = (JCOEF) (s << Al);
759 }
760
761 /* Completed MCU, so update state */
762 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
763 ASSIGN_STATE(entropy->saved, state);
764 }
765
766 /* Account for restart interval (no-op if not using restarts) */
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)
decode_mcu_AC_first(j_decompress_ptr cinfo,JBLOCKROW * MCU_data)779 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *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 (no-op if not using restarts) */
853 entropy->restarts_to_go--;
854
855 return TRUE;
856 }
857
858
859 /*
860 * MCU decoding for DC successive approximation refinement scan.
861 * Note: we assume such scans can be multi-component,
862 * although the spec is not very clear on the point.
863 */
864
865 METHODDEF(boolean)
decode_mcu_DC_refine(j_decompress_ptr cinfo,JBLOCKROW * MCU_data)866 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
867 {
868 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
869 int p1, blkn;
870 BITREAD_STATE_VARS;
871
872 /* Process restart marker if needed; may have to suspend */
873 if (cinfo->restart_interval) {
874 if (entropy->restarts_to_go == 0)
875 if (! process_restart(cinfo))
876 return FALSE;
877 }
878
879 /* Not worth the cycles to check insufficient_data here,
880 * since we will not change the data anyway if we read zeroes.
881 */
882
883 /* Load up working state */
884 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
885
886 p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
887
888 /* Outer loop handles each block in the MCU */
889
890 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
891 /* Encoded data is simply the next bit of the two's-complement DC value */
892 CHECK_BIT_BUFFER(br_state, 1, return FALSE);
893 if (GET_BITS(1))
894 MCU_data[blkn][0][0] |= p1;
895 /* Note: since we use |=, repeating the assignment later is safe */
896 }
897
898 /* Completed MCU, so update state */
899 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
900
901 /* Account for restart interval (no-op if not using restarts) */
902 entropy->restarts_to_go--;
903
904 return TRUE;
905 }
906
907
908 /*
909 * MCU decoding for AC successive approximation refinement scan.
910 */
911
912 METHODDEF(boolean)
decode_mcu_AC_refine(j_decompress_ptr cinfo,JBLOCKROW * MCU_data)913 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
914 {
915 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
916 register int s, k, r;
917 unsigned int EOBRUN;
918 int Se, p1, m1;
919 const int * natural_order;
920 JBLOCKROW block;
921 JCOEFPTR thiscoef;
922 BITREAD_STATE_VARS;
923 d_derived_tbl * tbl;
924 int num_newnz;
925 int newnz_pos[DCTSIZE2];
926
927 /* Process restart marker if needed; may have to suspend */
928 if (cinfo->restart_interval) {
929 if (entropy->restarts_to_go == 0)
930 if (! process_restart(cinfo))
931 return FALSE;
932 }
933
934 /* If we've run out of data, don't modify the MCU.
935 */
936 if (! entropy->insufficient_data) {
937
938 Se = cinfo->Se;
939 p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
940 m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */
941 natural_order = cinfo->natural_order;
942
943 /* Load up working state */
944 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
945 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
946
947 /* There is always only one block per MCU */
948 block = MCU_data[0];
949 tbl = entropy->ac_derived_tbl;
950
951 /* If we are forced to suspend, we must undo the assignments to any newly
952 * nonzero coefficients in the block, because otherwise we'd get confused
953 * next time about which coefficients were already nonzero.
954 * But we need not undo addition of bits to already-nonzero coefficients;
955 * instead, we can test the current bit to see if we already did it.
956 */
957 num_newnz = 0;
958
959 /* initialize coefficient loop counter to start of band */
960 k = cinfo->Ss;
961
962 if (EOBRUN == 0) {
963 do {
964 HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
965 r = s >> 4;
966 s &= 15;
967 if (s) {
968 if (s != 1) /* size of new coef should always be 1 */
969 WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
970 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
971 if (GET_BITS(1))
972 s = p1; /* newly nonzero coef is positive */
973 else
974 s = m1; /* newly nonzero coef is negative */
975 } else {
976 if (r != 15) {
977 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */
978 if (r) {
979 CHECK_BIT_BUFFER(br_state, r, goto undoit);
980 r = GET_BITS(r);
981 EOBRUN += r;
982 }
983 break; /* rest of block is handled by EOB logic */
984 }
985 /* note s = 0 for processing ZRL */
986 }
987 /* Advance over already-nonzero coefs and r still-zero coefs,
988 * appending correction bits to the nonzeroes. A correction bit is 1
989 * if the absolute value of the coefficient must be increased.
990 */
991 do {
992 thiscoef = *block + natural_order[k];
993 if (*thiscoef) {
994 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
995 if (GET_BITS(1)) {
996 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
997 if (*thiscoef >= 0)
998 *thiscoef += p1;
999 else
1000 *thiscoef += m1;
1001 }
1002 }
1003 } else {
1004 if (--r < 0)
1005 break; /* reached target zero coefficient */
1006 }
1007 k++;
1008 } while (k <= Se);
1009 if (s) {
1010 int pos = natural_order[k];
1011 /* Output newly nonzero coefficient */
1012 (*block)[pos] = (JCOEF) s;
1013 /* Remember its position in case we have to suspend */
1014 newnz_pos[num_newnz++] = pos;
1015 }
1016 k++;
1017 } while (k <= Se);
1018 }
1019
1020 if (EOBRUN) {
1021 /* Scan any remaining coefficient positions after the end-of-band
1022 * (the last newly nonzero coefficient, if any). Append a correction
1023 * bit to each already-nonzero coefficient. A correction bit is 1
1024 * if the absolute value of the coefficient must be increased.
1025 */
1026 do {
1027 thiscoef = *block + natural_order[k];
1028 if (*thiscoef) {
1029 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
1030 if (GET_BITS(1)) {
1031 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
1032 if (*thiscoef >= 0)
1033 *thiscoef += p1;
1034 else
1035 *thiscoef += m1;
1036 }
1037 }
1038 }
1039 k++;
1040 } while (k <= Se);
1041 /* Count one block completed in EOB run */
1042 EOBRUN--;
1043 }
1044
1045 /* Completed MCU, so update state */
1046 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1047 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
1048 }
1049
1050 /* Account for restart interval (no-op if not using restarts) */
1051 entropy->restarts_to_go--;
1052
1053 return TRUE;
1054
1055 undoit:
1056 /* Re-zero any output coefficients that we made newly nonzero */
1057 while (num_newnz)
1058 (*block)[newnz_pos[--num_newnz]] = 0;
1059
1060 return FALSE;
1061 }
1062
1063
1064 /*
1065 * Decode one MCU's worth of Huffman-compressed coefficients,
1066 * partial blocks.
1067 */
1068
1069 METHODDEF(boolean)
decode_mcu_sub(j_decompress_ptr cinfo,JBLOCKROW * MCU_data)1070 decode_mcu_sub (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
1071 {
1072 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1073 const int * natural_order;
1074 int Se, blkn;
1075 BITREAD_STATE_VARS;
1076 savable_state state;
1077
1078 /* Process restart marker if needed; may have to suspend */
1079 if (cinfo->restart_interval) {
1080 if (entropy->restarts_to_go == 0)
1081 if (! process_restart(cinfo))
1082 return FALSE;
1083 }
1084
1085 /* If we've run out of data, just leave the MCU set to zeroes.
1086 * This way, we return uniform gray for the remainder of the segment.
1087 */
1088 if (! entropy->insufficient_data) {
1089
1090 natural_order = cinfo->natural_order;
1091 Se = cinfo->lim_Se;
1092
1093 /* Load up working state */
1094 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
1095 ASSIGN_STATE(state, entropy->saved);
1096
1097 /* Outer loop handles each block in the MCU */
1098
1099 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1100 JBLOCKROW block = MCU_data[blkn];
1101 d_derived_tbl * htbl;
1102 register int s, k, r;
1103 int coef_limit, ci;
1104
1105 /* Decode a single block's worth of coefficients */
1106
1107 /* Section F.2.2.1: decode the DC coefficient difference */
1108 htbl = entropy->dc_cur_tbls[blkn];
1109 HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1110
1111 htbl = entropy->ac_cur_tbls[blkn];
1112 k = 1;
1113 coef_limit = entropy->coef_limit[blkn];
1114 if (coef_limit) {
1115 /* Convert DC difference to actual value, update last_dc_val */
1116 if (s) {
1117 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1118 r = GET_BITS(s);
1119 s = HUFF_EXTEND(r, s);
1120 }
1121 ci = cinfo->MCU_membership[blkn];
1122 s += state.last_dc_val[ci];
1123 state.last_dc_val[ci] = s;
1124 /* Output the DC coefficient */
1125 (*block)[0] = (JCOEF) s;
1126
1127 /* Section F.2.2.2: decode the AC coefficients */
1128 /* Since zeroes are skipped, output area must be cleared beforehand */
1129 for (; k < coef_limit; k++) {
1130 HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
1131
1132 r = s >> 4;
1133 s &= 15;
1134
1135 if (s) {
1136 k += r;
1137 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1138 r = GET_BITS(s);
1139 s = HUFF_EXTEND(r, s);
1140 /* Output coefficient in natural (dezigzagged) order.
1141 * Note: the extra entries in natural_order[] will save us
1142 * if k > Se, which could happen if the data is corrupted.
1143 */
1144 (*block)[natural_order[k]] = (JCOEF) s;
1145 } else {
1146 if (r != 15)
1147 goto EndOfBlock;
1148 k += 15;
1149 }
1150 }
1151 } else {
1152 if (s) {
1153 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1154 DROP_BITS(s);
1155 }
1156 }
1157
1158 /* Section F.2.2.2: decode the AC coefficients */
1159 /* In this path we just discard the values */
1160 for (; k <= Se; k++) {
1161 HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
1162
1163 r = s >> 4;
1164 s &= 15;
1165
1166 if (s) {
1167 k += r;
1168 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1169 DROP_BITS(s);
1170 } else {
1171 if (r != 15)
1172 break;
1173 k += 15;
1174 }
1175 }
1176
1177 EndOfBlock: ;
1178 }
1179
1180 /* Completed MCU, so update state */
1181 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1182 ASSIGN_STATE(entropy->saved, state);
1183 }
1184
1185 /* Account for restart interval (no-op if not using restarts) */
1186 entropy->restarts_to_go--;
1187
1188 return TRUE;
1189 }
1190
1191
1192 /*
1193 * Decode one MCU's worth of Huffman-compressed coefficients,
1194 * full-size blocks.
1195 */
1196
1197 METHODDEF(boolean)
decode_mcu(j_decompress_ptr cinfo,JBLOCKROW * MCU_data)1198 decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
1199 {
1200 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1201 int blkn;
1202 BITREAD_STATE_VARS;
1203 savable_state state;
1204
1205 /* Process restart marker if needed; may have to suspend */
1206 if (cinfo->restart_interval) {
1207 if (entropy->restarts_to_go == 0)
1208 if (! process_restart(cinfo))
1209 return FALSE;
1210 }
1211
1212 /* If we've run out of data, just leave the MCU set to zeroes.
1213 * This way, we return uniform gray for the remainder of the segment.
1214 */
1215 if (! entropy->insufficient_data) {
1216
1217 /* Load up working state */
1218 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
1219 ASSIGN_STATE(state, entropy->saved);
1220
1221 /* Outer loop handles each block in the MCU */
1222
1223 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1224 JBLOCKROW block = MCU_data[blkn];
1225 d_derived_tbl * htbl;
1226 register int s, k, r;
1227 int coef_limit, ci;
1228
1229 /* Decode a single block's worth of coefficients */
1230
1231 /* Section F.2.2.1: decode the DC coefficient difference */
1232 htbl = entropy->dc_cur_tbls[blkn];
1233 HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1234
1235 htbl = entropy->ac_cur_tbls[blkn];
1236 k = 1;
1237 coef_limit = entropy->coef_limit[blkn];
1238 if (coef_limit) {
1239 /* Convert DC difference to actual value, update last_dc_val */
1240 if (s) {
1241 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1242 r = GET_BITS(s);
1243 s = HUFF_EXTEND(r, s);
1244 }
1245 ci = cinfo->MCU_membership[blkn];
1246 s += state.last_dc_val[ci];
1247 state.last_dc_val[ci] = s;
1248 /* Output the DC coefficient */
1249 (*block)[0] = (JCOEF) s;
1250
1251 /* Section F.2.2.2: decode the AC coefficients */
1252 /* Since zeroes are skipped, output area must be cleared beforehand */
1253 for (; k < coef_limit; k++) {
1254 HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
1255
1256 r = s >> 4;
1257 s &= 15;
1258
1259 if (s) {
1260 k += r;
1261 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1262 r = GET_BITS(s);
1263 s = HUFF_EXTEND(r, s);
1264 /* Output coefficient in natural (dezigzagged) order.
1265 * Note: the extra entries in jpeg_natural_order[] will save us
1266 * if k >= DCTSIZE2, which could happen if the data is corrupted.
1267 */
1268 (*block)[jpeg_natural_order[k]] = (JCOEF) s;
1269 } else {
1270 if (r != 15)
1271 goto EndOfBlock;
1272 k += 15;
1273 }
1274 }
1275 } else {
1276 if (s) {
1277 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1278 DROP_BITS(s);
1279 }
1280 }
1281
1282 /* Section F.2.2.2: decode the AC coefficients */
1283 /* In this path we just discard the values */
1284 for (; k < DCTSIZE2; k++) {
1285 HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
1286
1287 r = s >> 4;
1288 s &= 15;
1289
1290 if (s) {
1291 k += r;
1292 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1293 DROP_BITS(s);
1294 } else {
1295 if (r != 15)
1296 break;
1297 k += 15;
1298 }
1299 }
1300
1301 EndOfBlock: ;
1302 }
1303
1304 /* Completed MCU, so update state */
1305 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1306 ASSIGN_STATE(entropy->saved, state);
1307 }
1308
1309 /* Account for restart interval (no-op if not using restarts) */
1310 entropy->restarts_to_go--;
1311
1312 return TRUE;
1313 }
1314
1315
1316 /*
1317 * Initialize for a Huffman-compressed scan.
1318 */
1319
1320 METHODDEF(void)
start_pass_huff_decoder(j_decompress_ptr cinfo)1321 start_pass_huff_decoder (j_decompress_ptr cinfo)
1322 {
1323 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1324 int ci, blkn, tbl, i;
1325 jpeg_component_info * compptr;
1326
1327 if (cinfo->progressive_mode) {
1328 /* Validate progressive scan parameters */
1329 if (cinfo->Ss == 0) {
1330 if (cinfo->Se != 0)
1331 goto bad;
1332 } else {
1333 /* need not check Ss/Se < 0 since they came from unsigned bytes */
1334 if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se)
1335 goto bad;
1336 /* AC scans may have only one component */
1337 if (cinfo->comps_in_scan != 1)
1338 goto bad;
1339 }
1340 if (cinfo->Ah != 0) {
1341 /* Successive approximation refinement scan: must have Al = Ah-1. */
1342 if (cinfo->Ah-1 != cinfo->Al)
1343 goto bad;
1344 }
1345 if (cinfo->Al > 13) { /* need not check for < 0 */
1346 /* Arguably the maximum Al value should be less than 13 for 8-bit precision,
1347 * but the spec doesn't say so, and we try to be liberal about what we
1348 * accept. Note: large Al values could result in out-of-range DC
1349 * coefficients during early scans, leading to bizarre displays due to
1350 * overflows in the IDCT math. But we won't crash.
1351 */
1352 bad:
1353 ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
1354 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
1355 }
1356 /* Update progression status, and verify that scan order is legal.
1357 * Note that inter-scan inconsistencies are treated as warnings
1358 * not fatal errors ... not clear if this is right way to behave.
1359 */
1360 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1361 int coefi, cindex = cinfo->cur_comp_info[ci]->component_index;
1362 int *coef_bit_ptr = & cinfo->coef_bits[cindex][0];
1363 if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
1364 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
1365 for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
1366 int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
1367 if (cinfo->Ah != expected)
1368 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
1369 coef_bit_ptr[coefi] = cinfo->Al;
1370 }
1371 }
1372
1373 /* Select MCU decoding routine */
1374 if (cinfo->Ah == 0) {
1375 if (cinfo->Ss == 0)
1376 entropy->pub.decode_mcu = decode_mcu_DC_first;
1377 else
1378 entropy->pub.decode_mcu = decode_mcu_AC_first;
1379 } else {
1380 if (cinfo->Ss == 0)
1381 entropy->pub.decode_mcu = decode_mcu_DC_refine;
1382 else
1383 entropy->pub.decode_mcu = decode_mcu_AC_refine;
1384 }
1385
1386 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1387 compptr = cinfo->cur_comp_info[ci];
1388 /* Make sure requested tables are present, and compute derived tables.
1389 * We may build same derived table more than once, but it's not expensive.
1390 */
1391 if (cinfo->Ss == 0) {
1392 if (cinfo->Ah == 0) { /* DC refinement needs no table */
1393 tbl = compptr->dc_tbl_no;
1394 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
1395 & entropy->derived_tbls[tbl]);
1396 }
1397 } else {
1398 tbl = compptr->ac_tbl_no;
1399 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
1400 & entropy->derived_tbls[tbl]);
1401 /* remember the single active table */
1402 entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
1403 }
1404 /* Initialize DC predictions to 0 */
1405 entropy->saved.last_dc_val[ci] = 0;
1406 }
1407
1408 /* Initialize private state variables */
1409 entropy->saved.EOBRUN = 0;
1410 } else {
1411 /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
1412 * This ought to be an error condition, but we make it a warning because
1413 * there are some baseline files out there with all zeroes in these bytes.
1414 */
1415 if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||
1416 ((cinfo->is_baseline || cinfo->Se < DCTSIZE2) &&
1417 cinfo->Se != cinfo->lim_Se))
1418 WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
1419
1420 /* Select MCU decoding routine */
1421 /* We retain the hard-coded case for full-size blocks.
1422 * This is not necessary, but it appears that this version is slightly
1423 * more performant in the given implementation.
1424 * With an improved implementation we would prefer a single optimized
1425 * function.
1426 */
1427 if (cinfo->lim_Se != DCTSIZE2-1)
1428 entropy->pub.decode_mcu = decode_mcu_sub;
1429 else
1430 entropy->pub.decode_mcu = decode_mcu;
1431
1432 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1433 compptr = cinfo->cur_comp_info[ci];
1434 /* Compute derived values for Huffman tables */
1435 /* We may do this more than once for a table, but it's not expensive */
1436 tbl = compptr->dc_tbl_no;
1437 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
1438 & entropy->dc_derived_tbls[tbl]);
1439 if (cinfo->lim_Se) { /* AC needs no table when not present */
1440 tbl = compptr->ac_tbl_no;
1441 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
1442 & entropy->ac_derived_tbls[tbl]);
1443 }
1444 /* Initialize DC predictions to 0 */
1445 entropy->saved.last_dc_val[ci] = 0;
1446 }
1447
1448 /* Precalculate decoding info for each block in an MCU of this scan */
1449 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1450 ci = cinfo->MCU_membership[blkn];
1451 compptr = cinfo->cur_comp_info[ci];
1452 /* Precalculate which table to use for each block */
1453 entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no];
1454 entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no];
1455 /* Decide whether we really care about the coefficient values */
1456 if (compptr->component_needed) {
1457 ci = compptr->DCT_v_scaled_size;
1458 i = compptr->DCT_h_scaled_size;
1459 switch (cinfo->lim_Se) {
1460 case (1*1-1):
1461 entropy->coef_limit[blkn] = 1;
1462 break;
1463 case (2*2-1):
1464 if (ci <= 0 || ci > 2) ci = 2;
1465 if (i <= 0 || i > 2) i = 2;
1466 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order2[ci - 1][i - 1];
1467 break;
1468 case (3*3-1):
1469 if (ci <= 0 || ci > 3) ci = 3;
1470 if (i <= 0 || i > 3) i = 3;
1471 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order3[ci - 1][i - 1];
1472 break;
1473 case (4*4-1):
1474 if (ci <= 0 || ci > 4) ci = 4;
1475 if (i <= 0 || i > 4) i = 4;
1476 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order4[ci - 1][i - 1];
1477 break;
1478 case (5*5-1):
1479 if (ci <= 0 || ci > 5) ci = 5;
1480 if (i <= 0 || i > 5) i = 5;
1481 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order5[ci - 1][i - 1];
1482 break;
1483 case (6*6-1):
1484 if (ci <= 0 || ci > 6) ci = 6;
1485 if (i <= 0 || i > 6) i = 6;
1486 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order6[ci - 1][i - 1];
1487 break;
1488 case (7*7-1):
1489 if (ci <= 0 || ci > 7) ci = 7;
1490 if (i <= 0 || i > 7) i = 7;
1491 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order7[ci - 1][i - 1];
1492 break;
1493 default:
1494 if (ci <= 0 || ci > 8) ci = 8;
1495 if (i <= 0 || i > 8) i = 8;
1496 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1];
1497 break;
1498 }
1499 } else {
1500 entropy->coef_limit[blkn] = 0;
1501 }
1502 }
1503 }
1504
1505 /* Initialize bitread state variables */
1506 entropy->bitstate.bits_left = 0;
1507 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
1508 entropy->insufficient_data = FALSE;
1509
1510 /* Initialize restart counter */
1511 entropy->restarts_to_go = cinfo->restart_interval;
1512 }
1513
1514
1515 /*
1516 * Module initialization routine for Huffman entropy decoding.
1517 */
1518
1519 GLOBAL(void)
jinit_huff_decoder(j_decompress_ptr cinfo)1520 jinit_huff_decoder (j_decompress_ptr cinfo)
1521 {
1522 huff_entropy_ptr entropy;
1523 int i;
1524
1525 entropy = (huff_entropy_ptr)
1526 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1527 SIZEOF(huff_entropy_decoder));
1528 cinfo->entropy = &entropy->pub;
1529 entropy->pub.start_pass = start_pass_huff_decoder;
1530 entropy->pub.finish_pass = finish_pass_huff;
1531
1532 if (cinfo->progressive_mode) {
1533 /* Create progression status table */
1534 int *coef_bit_ptr, ci;
1535 cinfo->coef_bits = (int (*)[DCTSIZE2])
1536 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1537 cinfo->num_components*DCTSIZE2*SIZEOF(int));
1538 coef_bit_ptr = & cinfo->coef_bits[0][0];
1539 for (ci = 0; ci < cinfo->num_components; ci++)
1540 for (i = 0; i < DCTSIZE2; i++)
1541 *coef_bit_ptr++ = -1;
1542
1543 /* Mark derived tables unallocated */
1544 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1545 entropy->derived_tbls[i] = NULL;
1546 }
1547 } else {
1548 /* Mark tables unallocated */
1549 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1550 entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
1551 }
1552 }
1553 }
1554