| 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 | wxjpeg_boolean dc_needed[D_MAX_BLOCKS_IN_MCU]; |
| 75 | wxjpeg_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, wxjpeg_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 (((JPEG_INT32) code) >= (((JPEG_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] = (JPEG_INT32) p - (JPEG_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(wxjpeg_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 JPEG_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(wxjpeg_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(wxjpeg_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 | } |