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e1929140 RR |
1 | /* |
2 | * jdhuff.c | |
3 | * | |
4 | * Copyright (C) 1991-1997, Thomas G. Lane. | |
5 | * This file is part of the Independent JPEG Group's software. | |
6 | * For conditions of distribution and use, see the accompanying README file. | |
7 | * | |
8 | * This file contains Huffman entropy decoding routines. | |
9 | * | |
10 | * Much of the complexity here has to do with supporting input suspension. | |
11 | * If the data source module demands suspension, we want to be able to back | |
12 | * up to the start of the current MCU. To do this, we copy state variables | |
13 | * into local working storage, and update them back to the permanent | |
14 | * storage only upon successful completion of an MCU. | |
15 | */ | |
16 | ||
17 | #define JPEG_INTERNALS | |
18 | #include "jinclude.h" | |
19 | #include "jpeglib.h" | |
20 | #include "jdhuff.h" /* Declarations shared with jdphuff.c */ | |
21 | ||
22 | ||
23 | /* | |
24 | * Expanded entropy decoder object for Huffman decoding. | |
25 | * | |
26 | * The savable_state subrecord contains fields that change within an MCU, | |
27 | * but must not be updated permanently until we complete the MCU. | |
28 | */ | |
29 | ||
30 | typedef struct { | |
31 | int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ | |
32 | } savable_state; | |
33 | ||
34 | /* This macro is to work around compilers with missing or broken | |
35 | * structure assignment. You'll need to fix this code if you have | |
36 | * such a compiler and you change MAX_COMPS_IN_SCAN. | |
37 | */ | |
38 | ||
39 | #ifndef NO_STRUCT_ASSIGN | |
40 | #define ASSIGN_STATE(dest,src) ((dest) = (src)) | |
41 | #else | |
42 | #if MAX_COMPS_IN_SCAN == 4 | |
43 | #define ASSIGN_STATE(dest,src) \ | |
44 | ((dest).last_dc_val[0] = (src).last_dc_val[0], \ | |
45 | (dest).last_dc_val[1] = (src).last_dc_val[1], \ | |
46 | (dest).last_dc_val[2] = (src).last_dc_val[2], \ | |
47 | (dest).last_dc_val[3] = (src).last_dc_val[3]) | |
48 | #endif | |
49 | #endif | |
50 | ||
51 | ||
52 | typedef struct { | |
53 | struct jpeg_entropy_decoder pub; /* public fields */ | |
54 | ||
55 | /* These fields are loaded into local variables at start of each MCU. | |
56 | * In case of suspension, we exit WITHOUT updating them. | |
57 | */ | |
58 | bitread_perm_state bitstate; /* Bit buffer at start of MCU */ | |
59 | savable_state saved; /* Other state at start of MCU */ | |
60 | ||
61 | /* These fields are NOT loaded into local working state. */ | |
62 | unsigned int restarts_to_go; /* MCUs left in this restart interval */ | |
63 | ||
64 | /* Pointers to derived tables (these workspaces have image lifespan) */ | |
65 | d_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS]; | |
66 | d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS]; | |
67 | ||
68 | /* Precalculated info set up by start_pass for use in decode_mcu: */ | |
69 | ||
70 | /* Pointers to derived tables to be used for each block within an MCU */ | |
71 | d_derived_tbl * dc_cur_tbls[D_MAX_BLOCKS_IN_MCU]; | |
72 | d_derived_tbl * ac_cur_tbls[D_MAX_BLOCKS_IN_MCU]; | |
73 | /* Whether we care about the DC and AC coefficient values for each block */ | |
e604ac79 MW |
74 | wxjpeg_boolean dc_needed[D_MAX_BLOCKS_IN_MCU]; |
75 | wxjpeg_boolean ac_needed[D_MAX_BLOCKS_IN_MCU]; | |
e1929140 RR |
76 | } huff_entropy_decoder; |
77 | ||
78 | typedef huff_entropy_decoder * huff_entropy_ptr; | |
79 | ||
80 | ||
81 | /* | |
82 | * Initialize for a Huffman-compressed scan. | |
83 | */ | |
84 | ||
85 | METHODDEF(void) | |
86 | start_pass_huff_decoder (j_decompress_ptr cinfo) | |
87 | { | |
88 | huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; | |
89 | int ci, blkn, dctbl, actbl; | |
90 | jpeg_component_info * compptr; | |
91 | ||
92 | /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG. | |
93 | * This ought to be an error condition, but we make it a warning because | |
94 | * there are some baseline files out there with all zeroes in these bytes. | |
95 | */ | |
96 | if (cinfo->Ss != 0 || cinfo->Se != DCTSIZE2-1 || | |
97 | cinfo->Ah != 0 || cinfo->Al != 0) | |
98 | WARNMS(cinfo, JWRN_NOT_SEQUENTIAL); | |
99 | ||
100 | for (ci = 0; ci < cinfo->comps_in_scan; ci++) { | |
101 | compptr = cinfo->cur_comp_info[ci]; | |
102 | dctbl = compptr->dc_tbl_no; | |
103 | actbl = compptr->ac_tbl_no; | |
104 | /* Compute derived values for Huffman tables */ | |
105 | /* We may do this more than once for a table, but it's not expensive */ | |
106 | jpeg_make_d_derived_tbl(cinfo, TRUE, dctbl, | |
107 | & entropy->dc_derived_tbls[dctbl]); | |
108 | jpeg_make_d_derived_tbl(cinfo, FALSE, actbl, | |
109 | & entropy->ac_derived_tbls[actbl]); | |
110 | /* Initialize DC predictions to 0 */ | |
111 | entropy->saved.last_dc_val[ci] = 0; | |
112 | } | |
113 | ||
114 | /* Precalculate decoding info for each block in an MCU of this scan */ | |
115 | for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { | |
116 | ci = cinfo->MCU_membership[blkn]; | |
117 | compptr = cinfo->cur_comp_info[ci]; | |
118 | /* Precalculate which table to use for each block */ | |
119 | entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no]; | |
120 | entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no]; | |
121 | /* Decide whether we really care about the coefficient values */ | |
122 | if (compptr->component_needed) { | |
123 | entropy->dc_needed[blkn] = TRUE; | |
124 | /* we don't need the ACs if producing a 1/8th-size image */ | |
125 | entropy->ac_needed[blkn] = (compptr->DCT_scaled_size > 1); | |
126 | } else { | |
127 | entropy->dc_needed[blkn] = entropy->ac_needed[blkn] = FALSE; | |
128 | } | |
129 | } | |
130 | ||
131 | /* Initialize bitread state variables */ | |
132 | entropy->bitstate.bits_left = 0; | |
133 | entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */ | |
134 | entropy->pub.insufficient_data = FALSE; | |
135 | ||
136 | /* Initialize restart counter */ | |
137 | entropy->restarts_to_go = cinfo->restart_interval; | |
138 | } | |
139 | ||
140 | ||
141 | /* | |
142 | * Compute the derived values for a Huffman table. | |
143 | * This routine also performs some validation checks on the table. | |
144 | * | |
145 | * Note this is also used by jdphuff.c. | |
146 | */ | |
147 | ||
148 | GLOBAL(void) | |
e604ac79 | 149 | jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, wxjpeg_boolean isDC, int tblno, |
e1929140 RR |
150 | d_derived_tbl ** pdtbl) |
151 | { | |
152 | JHUFF_TBL *htbl; | |
153 | d_derived_tbl *dtbl; | |
154 | int p, i, l, si, numsymbols; | |
155 | int lookbits, ctr; | |
156 | char huffsize[257]; | |
157 | unsigned int huffcode[257]; | |
158 | unsigned int code; | |
159 | ||
160 | /* Note that huffsize[] and huffcode[] are filled in code-length order, | |
161 | * paralleling the order of the symbols themselves in htbl->huffval[]. | |
162 | */ | |
163 | ||
164 | /* Find the input Huffman table */ | |
165 | if (tblno < 0 || tblno >= NUM_HUFF_TBLS) | |
166 | ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno); | |
167 | htbl = | |
168 | isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno]; | |
169 | if (htbl == NULL) | |
170 | ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno); | |
171 | ||
172 | /* Allocate a workspace if we haven't already done so. */ | |
173 | if (*pdtbl == NULL) | |
174 | *pdtbl = (d_derived_tbl *) | |
175 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, | |
176 | SIZEOF(d_derived_tbl)); | |
177 | dtbl = *pdtbl; | |
178 | dtbl->pub = htbl; /* fill in back link */ | |
179 | ||
180 | /* Figure C.1: make table of Huffman code length for each symbol */ | |
181 | ||
182 | p = 0; | |
183 | for (l = 1; l <= 16; l++) { | |
184 | i = (int) htbl->bits[l]; | |
185 | if (i < 0 || p + i > 256) /* protect against table overrun */ | |
186 | ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); | |
187 | while (i--) | |
188 | huffsize[p++] = (char) l; | |
189 | } | |
190 | huffsize[p] = 0; | |
191 | numsymbols = p; | |
192 | ||
193 | /* Figure C.2: generate the codes themselves */ | |
194 | /* We also validate that the counts represent a legal Huffman code tree. */ | |
195 | ||
196 | code = 0; | |
197 | si = huffsize[0]; | |
198 | p = 0; | |
199 | while (huffsize[p]) { | |
200 | while (((int) huffsize[p]) == si) { | |
201 | huffcode[p++] = code; | |
202 | code++; | |
203 | } | |
204 | /* code is now 1 more than the last code used for codelength si; but | |
205 | * it must still fit in si bits, since no code is allowed to be all ones. | |
206 | */ | |
39c2d6bd | 207 | if (((JPEG_INT32) code) >= (((JPEG_INT32) 1) << si)) |
e1929140 RR |
208 | ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); |
209 | code <<= 1; | |
210 | si++; | |
211 | } | |
212 | ||
213 | /* Figure F.15: generate decoding tables for bit-sequential decoding */ | |
214 | ||
215 | p = 0; | |
216 | for (l = 1; l <= 16; l++) { | |
217 | if (htbl->bits[l]) { | |
218 | /* valoffset[l] = huffval[] index of 1st symbol of code length l, | |
219 | * minus the minimum code of length l | |
220 | */ | |
39c2d6bd | 221 | dtbl->valoffset[l] = (JPEG_INT32) p - (JPEG_INT32) huffcode[p]; |
e1929140 RR |
222 | p += htbl->bits[l]; |
223 | dtbl->maxcode[l] = huffcode[p-1]; /* maximum code of length l */ | |
224 | } else { | |
225 | dtbl->maxcode[l] = -1; /* -1 if no codes of this length */ | |
226 | } | |
227 | } | |
228 | dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */ | |
229 | ||
230 | /* Compute lookahead tables to speed up decoding. | |
231 | * First we set all the table entries to 0, indicating "too long"; | |
232 | * then we iterate through the Huffman codes that are short enough and | |
233 | * fill in all the entries that correspond to bit sequences starting | |
234 | * with that code. | |
235 | */ | |
236 | ||
237 | MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits)); | |
238 | ||
239 | p = 0; | |
240 | for (l = 1; l <= HUFF_LOOKAHEAD; l++) { | |
241 | for (i = 1; i <= (int) htbl->bits[l]; i++, p++) { | |
242 | /* l = current code's length, p = its index in huffcode[] & huffval[]. */ | |
243 | /* Generate left-justified code followed by all possible bit sequences */ | |
244 | lookbits = huffcode[p] << (HUFF_LOOKAHEAD-l); | |
245 | for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) { | |
246 | dtbl->look_nbits[lookbits] = l; | |
247 | dtbl->look_sym[lookbits] = htbl->huffval[p]; | |
248 | lookbits++; | |
249 | } | |
250 | } | |
251 | } | |
252 | ||
253 | /* Validate symbols as being reasonable. | |
254 | * For AC tables, we make no check, but accept all byte values 0..255. | |
255 | * For DC tables, we require the symbols to be in range 0..15. | |
256 | * (Tighter bounds could be applied depending on the data depth and mode, | |
257 | * but this is sufficient to ensure safe decoding.) | |
258 | */ | |
259 | if (isDC) { | |
260 | for (i = 0; i < numsymbols; i++) { | |
261 | int sym = htbl->huffval[i]; | |
262 | if (sym < 0 || sym > 15) | |
263 | ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); | |
264 | } | |
265 | } | |
266 | } | |
267 | ||
268 | ||
269 | /* | |
270 | * Out-of-line code for bit fetching (shared with jdphuff.c). | |
271 | * See jdhuff.h for info about usage. | |
272 | * Note: current values of get_buffer and bits_left are passed as parameters, | |
273 | * but are returned in the corresponding fields of the state struct. | |
274 | * | |
275 | * On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width | |
276 | * of get_buffer to be used. (On machines with wider words, an even larger | |
277 | * buffer could be used.) However, on some machines 32-bit shifts are | |
278 | * quite slow and take time proportional to the number of places shifted. | |
279 | * (This is true with most PC compilers, for instance.) In this case it may | |
280 | * be a win to set MIN_GET_BITS to the minimum value of 15. This reduces the | |
281 | * average shift distance at the cost of more calls to jpeg_fill_bit_buffer. | |
282 | */ | |
283 | ||
284 | #ifdef SLOW_SHIFT_32 | |
285 | #define MIN_GET_BITS 15 /* minimum allowable value */ | |
286 | #else | |
287 | #define MIN_GET_BITS (BIT_BUF_SIZE-7) | |
288 | #endif | |
289 | ||
290 | ||
e604ac79 | 291 | GLOBAL(wxjpeg_boolean) |
e1929140 RR |
292 | jpeg_fill_bit_buffer (bitread_working_state * state, |
293 | register bit_buf_type get_buffer, register int bits_left, | |
294 | int nbits) | |
295 | /* Load up the bit buffer to a depth of at least nbits */ | |
296 | { | |
297 | /* Copy heavily used state fields into locals (hopefully registers) */ | |
298 | register const JOCTET * next_input_byte = state->next_input_byte; | |
299 | register size_t bytes_in_buffer = state->bytes_in_buffer; | |
300 | j_decompress_ptr cinfo = state->cinfo; | |
301 | ||
302 | /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */ | |
303 | /* (It is assumed that no request will be for more than that many bits.) */ | |
304 | /* We fail to do so only if we hit a marker or are forced to suspend. */ | |
305 | ||
306 | if (cinfo->unread_marker == 0) { /* cannot advance past a marker */ | |
307 | while (bits_left < MIN_GET_BITS) { | |
308 | register int c; | |
309 | ||
310 | /* Attempt to read a byte */ | |
311 | if (bytes_in_buffer == 0) { | |
312 | if (! (*cinfo->src->fill_input_buffer) (cinfo)) | |
313 | return FALSE; | |
314 | next_input_byte = cinfo->src->next_input_byte; | |
315 | bytes_in_buffer = cinfo->src->bytes_in_buffer; | |
316 | } | |
317 | bytes_in_buffer--; | |
318 | c = GETJOCTET(*next_input_byte++); | |
319 | ||
320 | /* If it's 0xFF, check and discard stuffed zero byte */ | |
321 | if (c == 0xFF) { | |
322 | /* Loop here to discard any padding FF's on terminating marker, | |
323 | * so that we can save a valid unread_marker value. NOTE: we will | |
324 | * accept multiple FF's followed by a 0 as meaning a single FF data | |
325 | * byte. This data pattern is not valid according to the standard. | |
326 | */ | |
327 | do { | |
328 | if (bytes_in_buffer == 0) { | |
329 | if (! (*cinfo->src->fill_input_buffer) (cinfo)) | |
330 | return FALSE; | |
331 | next_input_byte = cinfo->src->next_input_byte; | |
332 | bytes_in_buffer = cinfo->src->bytes_in_buffer; | |
333 | } | |
334 | bytes_in_buffer--; | |
335 | c = GETJOCTET(*next_input_byte++); | |
336 | } while (c == 0xFF); | |
337 | ||
338 | if (c == 0) { | |
339 | /* Found FF/00, which represents an FF data byte */ | |
340 | c = 0xFF; | |
341 | } else { | |
342 | /* Oops, it's actually a marker indicating end of compressed data. | |
343 | * Save the marker code for later use. | |
344 | * Fine point: it might appear that we should save the marker into | |
345 | * bitread working state, not straight into permanent state. But | |
346 | * once we have hit a marker, we cannot need to suspend within the | |
347 | * current MCU, because we will read no more bytes from the data | |
348 | * source. So it is OK to update permanent state right away. | |
349 | */ | |
350 | cinfo->unread_marker = c; | |
351 | /* See if we need to insert some fake zero bits. */ | |
352 | goto no_more_bytes; | |
353 | } | |
354 | } | |
355 | ||
356 | /* OK, load c into get_buffer */ | |
357 | get_buffer = (get_buffer << 8) | c; | |
358 | bits_left += 8; | |
359 | } /* end while */ | |
360 | } else { | |
361 | no_more_bytes: | |
362 | /* We get here if we've read the marker that terminates the compressed | |
363 | * data segment. There should be enough bits in the buffer register | |
364 | * to satisfy the request; if so, no problem. | |
365 | */ | |
366 | if (nbits > bits_left) { | |
367 | /* Uh-oh. Report corrupted data to user and stuff zeroes into | |
368 | * the data stream, so that we can produce some kind of image. | |
369 | * We use a nonvolatile flag to ensure that only one warning message | |
370 | * appears per data segment. | |
371 | */ | |
372 | if (! cinfo->entropy->insufficient_data) { | |
373 | WARNMS(cinfo, JWRN_HIT_MARKER); | |
374 | cinfo->entropy->insufficient_data = TRUE; | |
375 | } | |
376 | /* Fill the buffer with zero bits */ | |
377 | get_buffer <<= MIN_GET_BITS - bits_left; | |
378 | bits_left = MIN_GET_BITS; | |
379 | } | |
380 | } | |
381 | ||
382 | /* Unload the local registers */ | |
383 | state->next_input_byte = next_input_byte; | |
384 | state->bytes_in_buffer = bytes_in_buffer; | |
385 | state->get_buffer = get_buffer; | |
386 | state->bits_left = bits_left; | |
387 | ||
388 | return TRUE; | |
389 | } | |
390 | ||
391 | ||
392 | /* | |
393 | * Out-of-line code for Huffman code decoding. | |
394 | * See jdhuff.h for info about usage. | |
395 | */ | |
396 | ||
397 | GLOBAL(int) | |
398 | jpeg_huff_decode (bitread_working_state * state, | |
399 | register bit_buf_type get_buffer, register int bits_left, | |
400 | d_derived_tbl * htbl, int min_bits) | |
401 | { | |
402 | register int l = min_bits; | |
39c2d6bd | 403 | register JPEG_INT32 code; |
e1929140 RR |
404 | |
405 | /* HUFF_DECODE has determined that the code is at least min_bits */ | |
406 | /* bits long, so fetch that many bits in one swoop. */ | |
407 | ||
408 | CHECK_BIT_BUFFER(*state, l, return -1); | |
409 | code = GET_BITS(l); | |
410 | ||
411 | /* Collect the rest of the Huffman code one bit at a time. */ | |
412 | /* This is per Figure F.16 in the JPEG spec. */ | |
413 | ||
414 | while (code > htbl->maxcode[l]) { | |
415 | code <<= 1; | |
416 | CHECK_BIT_BUFFER(*state, 1, return -1); | |
417 | code |= GET_BITS(1); | |
418 | l++; | |
419 | } | |
420 | ||
421 | /* Unload the local registers */ | |
422 | state->get_buffer = get_buffer; | |
423 | state->bits_left = bits_left; | |
424 | ||
425 | /* With garbage input we may reach the sentinel value l = 17. */ | |
426 | ||
427 | if (l > 16) { | |
428 | WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE); | |
429 | return 0; /* fake a zero as the safest result */ | |
430 | } | |
431 | ||
432 | return htbl->pub->huffval[ (int) (code + htbl->valoffset[l]) ]; | |
433 | } | |
434 | ||
435 | ||
436 | /* | |
437 | * Figure F.12: extend sign bit. | |
438 | * On some machines, a shift and add will be faster than a table lookup. | |
439 | */ | |
440 | ||
441 | #ifdef AVOID_TABLES | |
442 | ||
443 | #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x)) | |
444 | ||
445 | #else | |
446 | ||
447 | #define HUFF_EXTEND(x,s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x)) | |
448 | ||
449 | static const int extend_test[16] = /* entry n is 2**(n-1) */ | |
450 | { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080, | |
451 | 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 }; | |
452 | ||
453 | static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */ | |
454 | { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1, | |
455 | ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1, | |
456 | ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1, | |
457 | ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 }; | |
458 | ||
459 | #endif /* AVOID_TABLES */ | |
460 | ||
461 | ||
462 | /* | |
463 | * Check for a restart marker & resynchronize decoder. | |
464 | * Returns FALSE if must suspend. | |
465 | */ | |
466 | ||
e604ac79 | 467 | LOCAL(wxjpeg_boolean) |
e1929140 RR |
468 | process_restart (j_decompress_ptr cinfo) |
469 | { | |
470 | huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; | |
471 | int ci; | |
472 | ||
473 | /* Throw away any unused bits remaining in bit buffer; */ | |
474 | /* include any full bytes in next_marker's count of discarded bytes */ | |
475 | cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8; | |
476 | entropy->bitstate.bits_left = 0; | |
477 | ||
478 | /* Advance past the RSTn marker */ | |
479 | if (! (*cinfo->marker->read_restart_marker) (cinfo)) | |
480 | return FALSE; | |
481 | ||
482 | /* Re-initialize DC predictions to 0 */ | |
483 | for (ci = 0; ci < cinfo->comps_in_scan; ci++) | |
484 | entropy->saved.last_dc_val[ci] = 0; | |
485 | ||
486 | /* Reset restart counter */ | |
487 | entropy->restarts_to_go = cinfo->restart_interval; | |
488 | ||
489 | /* Reset out-of-data flag, unless read_restart_marker left us smack up | |
490 | * against a marker. In that case we will end up treating the next data | |
491 | * segment as empty, and we can avoid producing bogus output pixels by | |
492 | * leaving the flag set. | |
493 | */ | |
494 | if (cinfo->unread_marker == 0) | |
495 | entropy->pub.insufficient_data = FALSE; | |
496 | ||
497 | return TRUE; | |
498 | } | |
499 | ||
500 | ||
501 | /* | |
502 | * Decode and return one MCU's worth of Huffman-compressed coefficients. | |
503 | * The coefficients are reordered from zigzag order into natural array order, | |
504 | * but are not dequantized. | |
505 | * | |
506 | * The i'th block of the MCU is stored into the block pointed to by | |
507 | * MCU_data[i]. WE ASSUME THIS AREA HAS BEEN ZEROED BY THE CALLER. | |
508 | * (Wholesale zeroing is usually a little faster than retail...) | |
509 | * | |
510 | * Returns FALSE if data source requested suspension. In that case no | |
511 | * changes have been made to permanent state. (Exception: some output | |
512 | * coefficients may already have been assigned. This is harmless for | |
513 | * this module, since we'll just re-assign them on the next call.) | |
514 | */ | |
515 | ||
e604ac79 | 516 | METHODDEF(wxjpeg_boolean) |
e1929140 RR |
517 | decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
518 | { | |
519 | huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; | |
520 | int blkn; | |
521 | BITREAD_STATE_VARS; | |
522 | savable_state state; | |
523 | ||
524 | /* Process restart marker if needed; may have to suspend */ | |
525 | if (cinfo->restart_interval) { | |
526 | if (entropy->restarts_to_go == 0) | |
527 | if (! process_restart(cinfo)) | |
528 | return FALSE; | |
529 | } | |
530 | ||
531 | /* If we've run out of data, just leave the MCU set to zeroes. | |
532 | * This way, we return uniform gray for the remainder of the segment. | |
533 | */ | |
534 | if (! entropy->pub.insufficient_data) { | |
535 | ||
536 | /* Load up working state */ | |
537 | BITREAD_LOAD_STATE(cinfo,entropy->bitstate); | |
538 | ASSIGN_STATE(state, entropy->saved); | |
539 | ||
540 | /* Outer loop handles each block in the MCU */ | |
541 | ||
542 | for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { | |
543 | JBLOCKROW block = MCU_data[blkn]; | |
544 | d_derived_tbl * dctbl = entropy->dc_cur_tbls[blkn]; | |
545 | d_derived_tbl * actbl = entropy->ac_cur_tbls[blkn]; | |
546 | register int s, k, r; | |
547 | ||
548 | /* Decode a single block's worth of coefficients */ | |
549 | ||
550 | /* Section F.2.2.1: decode the DC coefficient difference */ | |
551 | HUFF_DECODE(s, br_state, dctbl, return FALSE, label1); | |
552 | if (s) { | |
553 | CHECK_BIT_BUFFER(br_state, s, return FALSE); | |
554 | r = GET_BITS(s); | |
555 | s = HUFF_EXTEND(r, s); | |
556 | } | |
557 | ||
558 | if (entropy->dc_needed[blkn]) { | |
559 | /* Convert DC difference to actual value, update last_dc_val */ | |
560 | int ci = cinfo->MCU_membership[blkn]; | |
561 | s += state.last_dc_val[ci]; | |
562 | state.last_dc_val[ci] = s; | |
563 | /* Output the DC coefficient (assumes jpeg_natural_order[0] = 0) */ | |
564 | (*block)[0] = (JCOEF) s; | |
565 | } | |
566 | ||
567 | if (entropy->ac_needed[blkn]) { | |
568 | ||
569 | /* Section F.2.2.2: decode the AC coefficients */ | |
570 | /* Since zeroes are skipped, output area must be cleared beforehand */ | |
571 | for (k = 1; k < DCTSIZE2; k++) { | |
572 | HUFF_DECODE(s, br_state, actbl, return FALSE, label2); | |
573 | ||
574 | r = s >> 4; | |
575 | s &= 15; | |
576 | ||
577 | if (s) { | |
578 | k += r; | |
579 | CHECK_BIT_BUFFER(br_state, s, return FALSE); | |
580 | r = GET_BITS(s); | |
581 | s = HUFF_EXTEND(r, s); | |
582 | /* Output coefficient in natural (dezigzagged) order. | |
583 | * Note: the extra entries in jpeg_natural_order[] will save us | |
584 | * if k >= DCTSIZE2, which could happen if the data is corrupted. | |
585 | */ | |
586 | (*block)[jpeg_natural_order[k]] = (JCOEF) s; | |
587 | } else { | |
588 | if (r != 15) | |
589 | break; | |
590 | k += 15; | |
591 | } | |
592 | } | |
593 | ||
594 | } else { | |
595 | ||
596 | /* Section F.2.2.2: decode the AC coefficients */ | |
597 | /* In this path we just discard the values */ | |
598 | for (k = 1; k < DCTSIZE2; k++) { | |
599 | HUFF_DECODE(s, br_state, actbl, return FALSE, label3); | |
600 | ||
601 | r = s >> 4; | |
602 | s &= 15; | |
603 | ||
604 | if (s) { | |
605 | k += r; | |
606 | CHECK_BIT_BUFFER(br_state, s, return FALSE); | |
607 | DROP_BITS(s); | |
608 | } else { | |
609 | if (r != 15) | |
610 | break; | |
611 | k += 15; | |
612 | } | |
613 | } | |
614 | ||
615 | } | |
616 | } | |
617 | ||
618 | /* Completed MCU, so update state */ | |
619 | BITREAD_SAVE_STATE(cinfo,entropy->bitstate); | |
620 | ASSIGN_STATE(entropy->saved, state); | |
621 | } | |
622 | ||
623 | /* Account for restart interval (no-op if not using restarts) */ | |
624 | entropy->restarts_to_go--; | |
625 | ||
626 | return TRUE; | |
627 | } | |
628 | ||
629 | ||
630 | /* | |
631 | * Module initialization routine for Huffman entropy decoding. | |
632 | */ | |
633 | ||
634 | GLOBAL(void) | |
635 | jinit_huff_decoder (j_decompress_ptr cinfo) | |
636 | { | |
637 | huff_entropy_ptr entropy; | |
638 | int i; | |
639 | ||
640 | entropy = (huff_entropy_ptr) | |
641 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, | |
642 | SIZEOF(huff_entropy_decoder)); | |
643 | cinfo->entropy = (struct jpeg_entropy_decoder *) entropy; | |
644 | entropy->pub.start_pass = start_pass_huff_decoder; | |
645 | entropy->pub.decode_mcu = decode_mcu; | |
646 | ||
647 | /* Mark tables unallocated */ | |
648 | for (i = 0; i < NUM_HUFF_TBLS; i++) { | |
649 | entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL; | |
650 | } | |
651 | } |