1/*
2 * jdhuff.c
3 *
4 * Copyright (C) 1991-1997, Thomas G. Lane.
5 * Modified 2006-2012 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
28typedef 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
69typedef 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
79typedef 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
84typedef 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; \
183slowlabel: \
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
198typedef 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
222typedef 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
257typedef huff_entropy_decoder * huff_entropy_ptr;
258
259
260static 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
271static 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
281static 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
290static 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
298static 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
305static const int jpeg_zigzag_order3[3][3] = {
306 { 0, 1, 5 },
307 { 2, 4, 6 },
308 { 3, 7, 8 }
309};
310
311static 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
322LOCAL(void)
323jpeg_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
464LOCAL(boolean)
465jpeg_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
580static 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
591LOCAL(int)
592jpeg_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 * Check for a restart marker & resynchronize decoder.
632 * Returns FALSE if must suspend.
633 */
634
635LOCAL(boolean)
636process_restart (j_decompress_ptr cinfo)
637{
638 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
639 int ci;
640
641 /* Throw away any unused bits remaining in bit buffer; */
642 /* include any full bytes in next_marker's count of discarded bytes */
643 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
644 entropy->bitstate.bits_left = 0;
645
646 /* Advance past the RSTn marker */
647 if (! (*cinfo->marker->read_restart_marker) (cinfo))
648 return FALSE;
649
650 /* Re-initialize DC predictions to 0 */
651 for (ci = 0; ci < cinfo->comps_in_scan; ci++)
652 entropy->saved.last_dc_val[ci] = 0;
653 /* Re-init EOB run count, too */
654 entropy->saved.EOBRUN = 0;
655
656 /* Reset restart counter */
657 entropy->restarts_to_go = cinfo->restart_interval;
658
659 /* Reset out-of-data flag, unless read_restart_marker left us smack up
660 * against a marker. In that case we will end up treating the next data
661 * segment as empty, and we can avoid producing bogus output pixels by
662 * leaving the flag set.
663 */
664 if (cinfo->unread_marker == 0)
665 entropy->insufficient_data = FALSE;
666
667 return TRUE;
668}
669
670
671/*
672 * Huffman MCU decoding.
673 * Each of these routines decodes and returns one MCU's worth of
674 * Huffman-compressed coefficients.
675 * The coefficients are reordered from zigzag order into natural array order,
676 * but are not dequantized.
677 *
678 * The i'th block of the MCU is stored into the block pointed to by
679 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
680 * (Wholesale zeroing is usually a little faster than retail...)
681 *
682 * We return FALSE if data source requested suspension. In that case no
683 * changes have been made to permanent state. (Exception: some output
684 * coefficients may already have been assigned. This is harmless for
685 * spectral selection, since we'll just re-assign them on the next call.
686 * Successive approximation AC refinement has to be more careful, however.)
687 */
688
689/*
690 * MCU decoding for DC initial scan (either spectral selection,
691 * or first pass of successive approximation).
692 */
693
694METHODDEF(boolean)
695decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
696{
697 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
698 int Al = cinfo->Al;
699 register int s, r;
700 int blkn, ci;
701 JBLOCKROW block;
702 BITREAD_STATE_VARS;
703 savable_state state;
704 d_derived_tbl * tbl;
705 jpeg_component_info * compptr;
706
707 /* Process restart marker if needed; may have to suspend */
708 if (cinfo->restart_interval) {
709 if (entropy->restarts_to_go == 0)
710 if (! process_restart(cinfo))
711 return FALSE;
712 }
713
714 /* If we've run out of data, just leave the MCU set to zeroes.
715 * This way, we return uniform gray for the remainder of the segment.
716 */
717 if (! entropy->insufficient_data) {
718
719 /* Load up working state */
720 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
721 ASSIGN_STATE(state, entropy->saved);
722
723 /* Outer loop handles each block in the MCU */
724
725 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
726 block = MCU_data[blkn];
727 ci = cinfo->MCU_membership[blkn];
728 compptr = cinfo->cur_comp_info[ci];
729 tbl = entropy->derived_tbls[compptr->dc_tbl_no];
730
731 /* Decode a single block's worth of coefficients */
732
733 /* Section F.2.2.1: decode the DC coefficient difference */
734 HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
735 if (s) {
736 CHECK_BIT_BUFFER(br_state, s, return FALSE);
737 r = GET_BITS(s);
738 s = HUFF_EXTEND(r, s);
739 }
740
741 /* Convert DC difference to actual value, update last_dc_val */
742 s += state.last_dc_val[ci];
743 state.last_dc_val[ci] = s;
744 /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
745 (*block)[0] = (JCOEF) (s << Al);
746 }
747
748 /* Completed MCU, so update state */
749 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
750 ASSIGN_STATE(entropy->saved, state);
751 }
752
753 /* Account for restart interval (no-op if not using restarts) */
754 entropy->restarts_to_go--;
755
756 return TRUE;
757}
758
759
760/*
761 * MCU decoding for AC initial scan (either spectral selection,
762 * or first pass of successive approximation).
763 */
764
765METHODDEF(boolean)
766decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
767{
768 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
769 register int s, k, r;
770 unsigned int EOBRUN;
771 int Se, Al;
772 const int * natural_order;
773 JBLOCKROW block;
774 BITREAD_STATE_VARS;
775 d_derived_tbl * tbl;
776
777 /* Process restart marker if needed; may have to suspend */
778 if (cinfo->restart_interval) {
779 if (entropy->restarts_to_go == 0)
780 if (! process_restart(cinfo))
781 return FALSE;
782 }
783
784 /* If we've run out of data, just leave the MCU set to zeroes.
785 * This way, we return uniform gray for the remainder of the segment.
786 */
787 if (! entropy->insufficient_data) {
788
789 Se = cinfo->Se;
790 Al = cinfo->Al;
791 natural_order = cinfo->natural_order;
792
793 /* Load up working state.
794 * We can avoid loading/saving bitread state if in an EOB run.
795 */
796 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
797
798 /* There is always only one block per MCU */
799
800 if (EOBRUN) /* if it's a band of zeroes... */
801 EOBRUN--; /* ...process it now (we do nothing) */
802 else {
803 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
804 block = MCU_data[0];
805 tbl = entropy->ac_derived_tbl;
806
807 for (k = cinfo->Ss; k <= Se; k++) {
808 HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
809 r = s >> 4;
810 s &= 15;
811 if (s) {
812 k += r;
813 CHECK_BIT_BUFFER(br_state, s, return FALSE);
814 r = GET_BITS(s);
815 s = HUFF_EXTEND(r, s);
816 /* Scale and output coefficient in natural (dezigzagged) order */
817 (*block)[natural_order[k]] = (JCOEF) (s << Al);
818 } else {
819 if (r != 15) { /* EOBr, run length is 2^r + appended bits */
820 if (r) { /* EOBr, r > 0 */
821 EOBRUN = 1 << r;
822 CHECK_BIT_BUFFER(br_state, r, return FALSE);
823 r = GET_BITS(r);
824 EOBRUN += r;
825 EOBRUN--; /* this band is processed at this moment */
826 }
827 break; /* force end-of-band */
828 }
829 k += 15; /* ZRL: skip 15 zeroes in band */
830 }
831 }
832
833 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
834 }
835
836 /* Completed MCU, so update state */
837 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
838 }
839
840 /* Account for restart interval (no-op if not using restarts) */
841 entropy->restarts_to_go--;
842
843 return TRUE;
844}
845
846
847/*
848 * MCU decoding for DC successive approximation refinement scan.
849 * Note: we assume such scans can be multi-component, although the spec
850 * is not very clear on the point.
851 */
852
853METHODDEF(boolean)
854decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
855{
856 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
857 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
858 int blkn;
859 JBLOCKROW block;
860 BITREAD_STATE_VARS;
861
862 /* Process restart marker if needed; may have to suspend */
863 if (cinfo->restart_interval) {
864 if (entropy->restarts_to_go == 0)
865 if (! process_restart(cinfo))
866 return FALSE;
867 }
868
869 /* Not worth the cycles to check insufficient_data here,
870 * since we will not change the data anyway if we read zeroes.
871 */
872
873 /* Load up working state */
874 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
875
876 /* Outer loop handles each block in the MCU */
877
878 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
879 block = MCU_data[blkn];
880
881 /* Encoded data is simply the next bit of the two's-complement DC value */
882 CHECK_BIT_BUFFER(br_state, 1, return FALSE);
883 if (GET_BITS(1))
884 (*block)[0] |= p1;
885 /* Note: since we use |=, repeating the assignment later is safe */
886 }
887
888 /* Completed MCU, so update state */
889 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
890
891 /* Account for restart interval (no-op if not using restarts) */
892 entropy->restarts_to_go--;
893
894 return TRUE;
895}
896
897
898/*
899 * MCU decoding for AC successive approximation refinement scan.
900 */
901
902METHODDEF(boolean)
903decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
904{
905 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
906 register int s, k, r;
907 unsigned int EOBRUN;
908 int Se, p1, m1;
909 const int * natural_order;
910 JBLOCKROW block;
911 JCOEFPTR thiscoef;
912 BITREAD_STATE_VARS;
913 d_derived_tbl * tbl;
914 int num_newnz;
915 int newnz_pos[DCTSIZE2];
916
917 /* Process restart marker if needed; may have to suspend */
918 if (cinfo->restart_interval) {
919 if (entropy->restarts_to_go == 0)
920 if (! process_restart(cinfo))
921 return FALSE;
922 }
923
924 /* If we've run out of data, don't modify the MCU.
925 */
926 if (! entropy->insufficient_data) {
927
928 Se = cinfo->Se;
929 p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
930 m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */
931 natural_order = cinfo->natural_order;
932
933 /* Load up working state */
934 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
935 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
936
937 /* There is always only one block per MCU */
938 block = MCU_data[0];
939 tbl = entropy->ac_derived_tbl;
940
941 /* If we are forced to suspend, we must undo the assignments to any newly
942 * nonzero coefficients in the block, because otherwise we'd get confused
943 * next time about which coefficients were already nonzero.
944 * But we need not undo addition of bits to already-nonzero coefficients;
945 * instead, we can test the current bit to see if we already did it.
946 */
947 num_newnz = 0;
948
949 /* initialize coefficient loop counter to start of band */
950 k = cinfo->Ss;
951
952 if (EOBRUN == 0) {
953 do {
954 HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
955 r = s >> 4;
956 s &= 15;
957 if (s) {
958 if (s != 1) /* size of new coef should always be 1 */
959 WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
960 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
961 if (GET_BITS(1))
962 s = p1; /* newly nonzero coef is positive */
963 else
964 s = m1; /* newly nonzero coef is negative */
965 } else {
966 if (r != 15) {
967 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */
968 if (r) {
969 CHECK_BIT_BUFFER(br_state, r, goto undoit);
970 r = GET_BITS(r);
971 EOBRUN += r;
972 }
973 break; /* rest of block is handled by EOB logic */
974 }
975 /* note s = 0 for processing ZRL */
976 }
977 /* Advance over already-nonzero coefs and r still-zero coefs,
978 * appending correction bits to the nonzeroes. A correction bit is 1
979 * if the absolute value of the coefficient must be increased.
980 */
981 do {
982 thiscoef = *block + natural_order[k];
983 if (*thiscoef) {
984 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
985 if (GET_BITS(1)) {
986 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
987 if (*thiscoef >= 0)
988 *thiscoef += p1;
989 else
990 *thiscoef += m1;
991 }
992 }
993 } else {
994 if (--r < 0)
995 break; /* reached target zero coefficient */
996 }
997 k++;
998 } while (k <= Se);
999 if (s) {
1000 int pos = natural_order[k];
1001 /* Output newly nonzero coefficient */
1002 (*block)[pos] = (JCOEF) s;
1003 /* Remember its position in case we have to suspend */
1004 newnz_pos[num_newnz++] = pos;
1005 }
1006 k++;
1007 } while (k <= Se);
1008 }
1009
1010 if (EOBRUN) {
1011 /* Scan any remaining coefficient positions after the end-of-band
1012 * (the last newly nonzero coefficient, if any). Append a correction
1013 * bit to each already-nonzero coefficient. A correction bit is 1
1014 * if the absolute value of the coefficient must be increased.
1015 */
1016 do {
1017 thiscoef = *block + natural_order[k];
1018 if (*thiscoef) {
1019 CHECK_BIT_BUFFER(br_state, 1, goto undoit);
1020 if (GET_BITS(1)) {
1021 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
1022 if (*thiscoef >= 0)
1023 *thiscoef += p1;
1024 else
1025 *thiscoef += m1;
1026 }
1027 }
1028 }
1029 k++;
1030 } while (k <= Se);
1031 /* Count one block completed in EOB run */
1032 EOBRUN--;
1033 }
1034
1035 /* Completed MCU, so update state */
1036 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1037 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
1038 }
1039
1040 /* Account for restart interval (no-op if not using restarts) */
1041 entropy->restarts_to_go--;
1042
1043 return TRUE;
1044
1045undoit:
1046 /* Re-zero any output coefficients that we made newly nonzero */
1047 while (num_newnz)
1048 (*block)[newnz_pos[--num_newnz]] = 0;
1049
1050 return FALSE;
1051}
1052
1053
1054/*
1055 * Decode one MCU's worth of Huffman-compressed coefficients,
1056 * partial blocks.
1057 */
1058
1059METHODDEF(boolean)
1060decode_mcu_sub (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
1061{
1062 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1063 const int * natural_order;
1064 int Se, blkn;
1065 BITREAD_STATE_VARS;
1066 savable_state state;
1067
1068 /* Process restart marker if needed; may have to suspend */
1069 if (cinfo->restart_interval) {
1070 if (entropy->restarts_to_go == 0)
1071 if (! process_restart(cinfo))
1072 return FALSE;
1073 }
1074
1075 /* If we've run out of data, just leave the MCU set to zeroes.
1076 * This way, we return uniform gray for the remainder of the segment.
1077 */
1078 if (! entropy->insufficient_data) {
1079
1080 natural_order = cinfo->natural_order;
1081 Se = cinfo->lim_Se;
1082
1083 /* Load up working state */
1084 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
1085 ASSIGN_STATE(state, entropy->saved);
1086
1087 /* Outer loop handles each block in the MCU */
1088
1089 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1090 JBLOCKROW block = MCU_data[blkn];
1091 d_derived_tbl * htbl;
1092 register int s, k, r;
1093 int coef_limit, ci;
1094
1095 /* Decode a single block's worth of coefficients */
1096
1097 /* Section F.2.2.1: decode the DC coefficient difference */
1098 htbl = entropy->dc_cur_tbls[blkn];
1099 HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1100
1101 htbl = entropy->ac_cur_tbls[blkn];
1102 k = 1;
1103 coef_limit = entropy->coef_limit[blkn];
1104 if (coef_limit) {
1105 /* Convert DC difference to actual value, update last_dc_val */
1106 if (s) {
1107 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1108 r = GET_BITS(s);
1109 s = HUFF_EXTEND(r, s);
1110 }
1111 ci = cinfo->MCU_membership[blkn];
1112 s += state.last_dc_val[ci];
1113 state.last_dc_val[ci] = s;
1114 /* Output the DC coefficient */
1115 (*block)[0] = (JCOEF) s;
1116
1117 /* Section F.2.2.2: decode the AC coefficients */
1118 /* Since zeroes are skipped, output area must be cleared beforehand */
1119 for (; k < coef_limit; k++) {
1120 HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
1121
1122 r = s >> 4;
1123 s &= 15;
1124
1125 if (s) {
1126 k += r;
1127 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1128 r = GET_BITS(s);
1129 s = HUFF_EXTEND(r, s);
1130 /* Output coefficient in natural (dezigzagged) order.
1131 * Note: the extra entries in natural_order[] will save us
1132 * if k > Se, which could happen if the data is corrupted.
1133 */
1134 (*block)[natural_order[k]] = (JCOEF) s;
1135 } else {
1136 if (r != 15)
1137 goto EndOfBlock;
1138 k += 15;
1139 }
1140 }
1141 } else {
1142 if (s) {
1143 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1144 DROP_BITS(s);
1145 }
1146 }
1147
1148 /* Section F.2.2.2: decode the AC coefficients */
1149 /* In this path we just discard the values */
1150 for (; k <= Se; k++) {
1151 HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
1152
1153 r = s >> 4;
1154 s &= 15;
1155
1156 if (s) {
1157 k += r;
1158 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1159 DROP_BITS(s);
1160 } else {
1161 if (r != 15)
1162 break;
1163 k += 15;
1164 }
1165 }
1166
1167 EndOfBlock: ;
1168 }
1169
1170 /* Completed MCU, so update state */
1171 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1172 ASSIGN_STATE(entropy->saved, state);
1173 }
1174
1175 /* Account for restart interval (no-op if not using restarts) */
1176 entropy->restarts_to_go--;
1177
1178 return TRUE;
1179}
1180
1181
1182/*
1183 * Decode one MCU's worth of Huffman-compressed coefficients,
1184 * full-size blocks.
1185 */
1186
1187METHODDEF(boolean)
1188decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
1189{
1190 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1191 int blkn;
1192 BITREAD_STATE_VARS;
1193 savable_state state;
1194
1195 /* Process restart marker if needed; may have to suspend */
1196 if (cinfo->restart_interval) {
1197 if (entropy->restarts_to_go == 0)
1198 if (! process_restart(cinfo))
1199 return FALSE;
1200 }
1201
1202 /* If we've run out of data, just leave the MCU set to zeroes.
1203 * This way, we return uniform gray for the remainder of the segment.
1204 */
1205 if (! entropy->insufficient_data) {
1206
1207 /* Load up working state */
1208 BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
1209 ASSIGN_STATE(state, entropy->saved);
1210
1211 /* Outer loop handles each block in the MCU */
1212
1213 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1214 JBLOCKROW block = MCU_data[blkn];
1215 d_derived_tbl * htbl;
1216 register int s, k, r;
1217 int coef_limit, ci;
1218
1219 /* Decode a single block's worth of coefficients */
1220
1221 /* Section F.2.2.1: decode the DC coefficient difference */
1222 htbl = entropy->dc_cur_tbls[blkn];
1223 HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1224
1225 htbl = entropy->ac_cur_tbls[blkn];
1226 k = 1;
1227 coef_limit = entropy->coef_limit[blkn];
1228 if (coef_limit) {
1229 /* Convert DC difference to actual value, update last_dc_val */
1230 if (s) {
1231 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1232 r = GET_BITS(s);
1233 s = HUFF_EXTEND(r, s);
1234 }
1235 ci = cinfo->MCU_membership[blkn];
1236 s += state.last_dc_val[ci];
1237 state.last_dc_val[ci] = s;
1238 /* Output the DC coefficient */
1239 (*block)[0] = (JCOEF) s;
1240
1241 /* Section F.2.2.2: decode the AC coefficients */
1242 /* Since zeroes are skipped, output area must be cleared beforehand */
1243 for (; k < coef_limit; k++) {
1244 HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
1245
1246 r = s >> 4;
1247 s &= 15;
1248
1249 if (s) {
1250 k += r;
1251 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1252 r = GET_BITS(s);
1253 s = HUFF_EXTEND(r, s);
1254 /* Output coefficient in natural (dezigzagged) order.
1255 * Note: the extra entries in jpeg_natural_order[] will save us
1256 * if k >= DCTSIZE2, which could happen if the data is corrupted.
1257 */
1258 (*block)[jpeg_natural_order[k]] = (JCOEF) s;
1259 } else {
1260 if (r != 15)
1261 goto EndOfBlock;
1262 k += 15;
1263 }
1264 }
1265 } else {
1266 if (s) {
1267 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1268 DROP_BITS(s);
1269 }
1270 }
1271
1272 /* Section F.2.2.2: decode the AC coefficients */
1273 /* In this path we just discard the values */
1274 for (; k < DCTSIZE2; k++) {
1275 HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
1276
1277 r = s >> 4;
1278 s &= 15;
1279
1280 if (s) {
1281 k += r;
1282 CHECK_BIT_BUFFER(br_state, s, return FALSE);
1283 DROP_BITS(s);
1284 } else {
1285 if (r != 15)
1286 break;
1287 k += 15;
1288 }
1289 }
1290
1291 EndOfBlock: ;
1292 }
1293
1294 /* Completed MCU, so update state */
1295 BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1296 ASSIGN_STATE(entropy->saved, state);
1297 }
1298
1299 /* Account for restart interval (no-op if not using restarts) */
1300 entropy->restarts_to_go--;
1301
1302 return TRUE;
1303}
1304
1305
1306/*
1307 * Initialize for a Huffman-compressed scan.
1308 */
1309
1310METHODDEF(void)
1311start_pass_huff_decoder (j_decompress_ptr cinfo)
1312{
1313 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1314 int ci, blkn, tbl, i;
1315 jpeg_component_info * compptr;
1316
1317 if (cinfo->progressive_mode) {
1318 /* Validate progressive scan parameters */
1319 if (cinfo->Ss == 0) {
1320 if (cinfo->Se != 0)
1321 goto bad;
1322 } else {
1323 /* need not check Ss/Se < 0 since they came from unsigned bytes */
1324 if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se)
1325 goto bad;
1326 /* AC scans may have only one component */
1327 if (cinfo->comps_in_scan != 1)
1328 goto bad;
1329 }
1330 if (cinfo->Ah != 0) {
1331 /* Successive approximation refinement scan: must have Al = Ah-1. */
1332 if (cinfo->Ah-1 != cinfo->Al)
1333 goto bad;
1334 }
1335 if (cinfo->Al > 13) { /* need not check for < 0 */
1336 /* Arguably the maximum Al value should be less than 13 for 8-bit precision,
1337 * but the spec doesn't say so, and we try to be liberal about what we
1338 * accept. Note: large Al values could result in out-of-range DC
1339 * coefficients during early scans, leading to bizarre displays due to
1340 * overflows in the IDCT math. But we won't crash.
1341 */
1342 bad:
1343 ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
1344 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
1345 }
1346 /* Update progression status, and verify that scan order is legal.
1347 * Note that inter-scan inconsistencies are treated as warnings
1348 * not fatal errors ... not clear if this is right way to behave.
1349 */
1350 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1351 int coefi, cindex = cinfo->cur_comp_info[ci]->component_index;
1352 int *coef_bit_ptr = & cinfo->coef_bits[cindex][0];
1353 if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
1354 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
1355 for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
1356 int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
1357 if (cinfo->Ah != expected)
1358 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
1359 coef_bit_ptr[coefi] = cinfo->Al;
1360 }
1361 }
1362
1363 /* Select MCU decoding routine */
1364 if (cinfo->Ah == 0) {
1365 if (cinfo->Ss == 0)
1366 entropy->pub.decode_mcu = decode_mcu_DC_first;
1367 else
1368 entropy->pub.decode_mcu = decode_mcu_AC_first;
1369 } else {
1370 if (cinfo->Ss == 0)
1371 entropy->pub.decode_mcu = decode_mcu_DC_refine;
1372 else
1373 entropy->pub.decode_mcu = decode_mcu_AC_refine;
1374 }
1375
1376 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1377 compptr = cinfo->cur_comp_info[ci];
1378 /* Make sure requested tables are present, and compute derived tables.
1379 * We may build same derived table more than once, but it's not expensive.
1380 */
1381 if (cinfo->Ss == 0) {
1382 if (cinfo->Ah == 0) { /* DC refinement needs no table */
1383 tbl = compptr->dc_tbl_no;
1384 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
1385 & entropy->derived_tbls[tbl]);
1386 }
1387 } else {
1388 tbl = compptr->ac_tbl_no;
1389 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
1390 & entropy->derived_tbls[tbl]);
1391 /* remember the single active table */
1392 entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
1393 }
1394 /* Initialize DC predictions to 0 */
1395 entropy->saved.last_dc_val[ci] = 0;
1396 }
1397
1398 /* Initialize private state variables */
1399 entropy->saved.EOBRUN = 0;
1400 } else {
1401 /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
1402 * This ought to be an error condition, but we make it a warning because
1403 * there are some baseline files out there with all zeroes in these bytes.
1404 */
1405 if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||
1406 ((cinfo->is_baseline || cinfo->Se < DCTSIZE2) &&
1407 cinfo->Se != cinfo->lim_Se))
1408 WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
1409
1410 /* Select MCU decoding routine */
1411 /* We retain the hard-coded case for full-size blocks.
1412 * This is not necessary, but it appears that this version is slightly
1413 * more performant in the given implementation.
1414 * With an improved implementation we would prefer a single optimized
1415 * function.
1416 */
1417 if (cinfo->lim_Se != DCTSIZE2-1)
1418 entropy->pub.decode_mcu = decode_mcu_sub;
1419 else
1420 entropy->pub.decode_mcu = decode_mcu;
1421
1422 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1423 compptr = cinfo->cur_comp_info[ci];
1424 /* Compute derived values for Huffman tables */
1425 /* We may do this more than once for a table, but it's not expensive */
1426 tbl = compptr->dc_tbl_no;
1427 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
1428 & entropy->dc_derived_tbls[tbl]);
1429 if (cinfo->lim_Se) { /* AC needs no table when not present */
1430 tbl = compptr->ac_tbl_no;
1431 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
1432 & entropy->ac_derived_tbls[tbl]);
1433 }
1434 /* Initialize DC predictions to 0 */
1435 entropy->saved.last_dc_val[ci] = 0;
1436 }
1437
1438 /* Precalculate decoding info for each block in an MCU of this scan */
1439 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1440 ci = cinfo->MCU_membership[blkn];
1441 compptr = cinfo->cur_comp_info[ci];
1442 /* Precalculate which table to use for each block */
1443 entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no];
1444 entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no];
1445 /* Decide whether we really care about the coefficient values */
1446 if (compptr->component_needed) {
1447 ci = compptr->DCT_v_scaled_size;
1448 i = compptr->DCT_h_scaled_size;
1449 switch (cinfo->lim_Se) {
1450 case (1*1-1):
1451 entropy->coef_limit[blkn] = 1;
1452 break;
1453 case (2*2-1):
1454 if (ci <= 0 || ci > 2) ci = 2;
1455 if (i <= 0 || i > 2) i = 2;
1456 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order2[ci - 1][i - 1];
1457 break;
1458 case (3*3-1):
1459 if (ci <= 0 || ci > 3) ci = 3;
1460 if (i <= 0 || i > 3) i = 3;
1461 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order3[ci - 1][i - 1];
1462 break;
1463 case (4*4-1):
1464 if (ci <= 0 || ci > 4) ci = 4;
1465 if (i <= 0 || i > 4) i = 4;
1466 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order4[ci - 1][i - 1];
1467 break;
1468 case (5*5-1):
1469 if (ci <= 0 || ci > 5) ci = 5;
1470 if (i <= 0 || i > 5) i = 5;
1471 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order5[ci - 1][i - 1];
1472 break;
1473 case (6*6-1):
1474 if (ci <= 0 || ci > 6) ci = 6;
1475 if (i <= 0 || i > 6) i = 6;
1476 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order6[ci - 1][i - 1];
1477 break;
1478 case (7*7-1):
1479 if (ci <= 0 || ci > 7) ci = 7;
1480 if (i <= 0 || i > 7) i = 7;
1481 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order7[ci - 1][i - 1];
1482 break;
1483 default:
1484 if (ci <= 0 || ci > 8) ci = 8;
1485 if (i <= 0 || i > 8) i = 8;
1486 entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1];
1487 break;
1488 }
1489 } else {
1490 entropy->coef_limit[blkn] = 0;
1491 }
1492 }
1493 }
1494
1495 /* Initialize bitread state variables */
1496 entropy->bitstate.bits_left = 0;
1497 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
1498 entropy->insufficient_data = FALSE;
1499
1500 /* Initialize restart counter */
1501 entropy->restarts_to_go = cinfo->restart_interval;
1502}
1503
1504
1505/*
1506 * Module initialization routine for Huffman entropy decoding.
1507 */
1508
1509GLOBAL(void)
1510jinit_huff_decoder (j_decompress_ptr cinfo)
1511{
1512 huff_entropy_ptr entropy;
1513 int i;
1514
1515 entropy = (huff_entropy_ptr)
1516 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1517 SIZEOF(huff_entropy_decoder));
1518 cinfo->entropy = &entropy->pub;
1519 entropy->pub.start_pass = start_pass_huff_decoder;
1520
1521 if (cinfo->progressive_mode) {
1522 /* Create progression status table */
1523 int *coef_bit_ptr, ci;
1524 cinfo->coef_bits = (int (*)[DCTSIZE2])
1525 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1526 cinfo->num_components*DCTSIZE2*SIZEOF(int));
1527 coef_bit_ptr = & cinfo->coef_bits[0][0];
1528 for (ci = 0; ci < cinfo->num_components; ci++)
1529 for (i = 0; i < DCTSIZE2; i++)
1530 *coef_bit_ptr++ = -1;
1531
1532 /* Mark derived tables unallocated */
1533 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1534 entropy->derived_tbls[i] = NULL;
1535 }
1536 } else {
1537 /* Mark tables unallocated */
1538 for (i = 0; i < NUM_HUFF_TBLS; i++) {
1539 entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
1540 }
1541 }
1542}
1543