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| 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 */ | |
| 74 boolean dc_needed[D_MAX_BLOCKS_IN_MCU]; | |
| 75 boolean ac_needed[D_MAX_BLOCKS_IN_MCU]; | |
| 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) | |
| 149 jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno, | |
| 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 */ | |
| 207 if (((INT32) code) >= (((INT32) 1) << si)) | |
| 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 */ | |
| 221 dtbl->valoffset[l] = (INT32) p - (INT32) huffcode[p]; | |
| 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 | |
| 291 GLOBAL(boolean) | |
| 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; | |
| 403 register INT32 code; | |
| 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 | |
| 467 LOCAL(boolean) | |
| 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 | |
| 516 METHODDEF(boolean) | |
| 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 } | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 1705523002:
Remove libjpeg and libjpeg_turbo. (Closed)
Base URL: https://github.com/domokit/mojo.git@master