contrib/xz/src/liblzma/lzma/lzma_decoder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       lzma_decoder.c
   4 /// \brief      LZMA decoder
   5 ///
   6 //  Authors:    Igor Pavlov
   7 //              Lasse Collin
   8 //
   9 //  This file has been put into the public domain.
  10 //  You can do whatever you want with this file.
  11 //
  12 ///////////////////////////////////////////////////////////////////////////////
  13
  14 #include "lz_decoder.h"
  15 #include "lzma_common.h"
  16 #include "lzma_decoder.h"
  17 #include "range_decoder.h"
  18
  19
  20 #ifdef HAVE_SMALL
  21
  22 // Macros for (somewhat) size-optimized code.
  23 #define seq_4(seq) seq
  24
  25 #define seq_6(seq) seq
  26
  27 #define seq_8(seq) seq
  28
  29 #define seq_len(seq) \
  30         seq ## _CHOICE, \
  31         seq ## _CHOICE2, \
  32         seq ## _BITTREE
  33
  34 #define len_decode(target, ld, pos_state, seq) \
  35 do { \
  36 case seq ## _CHOICE: \
  37         rc_if_0(ld.choice, seq ## _CHOICE) { \
  38                 rc_update_0(ld.choice); \
  39                 probs = ld.low[pos_state];\
  40                 limit = LEN_LOW_SYMBOLS; \
  41                 target = MATCH_LEN_MIN; \
  42         } else { \
  43                 rc_update_1(ld.choice); \
  44 case seq ## _CHOICE2: \
  45                 rc_if_0(ld.choice2, seq ## _CHOICE2) { \
  46                         rc_update_0(ld.choice2); \
  47                         probs = ld.mid[pos_state]; \
  48                         limit = LEN_MID_SYMBOLS; \
  49                         target = MATCH_LEN_MIN + LEN_LOW_SYMBOLS; \
  50                 } else { \
  51                         rc_update_1(ld.choice2); \
  52                         probs = ld.high; \
  53                         limit = LEN_HIGH_SYMBOLS; \
  54                         target = MATCH_LEN_MIN + LEN_LOW_SYMBOLS \
  55                                         + LEN_MID_SYMBOLS; \
  56                 } \
  57         } \
  58         symbol = 1; \
  59 case seq ## _BITTREE: \
  60         do { \
  61                 rc_bit(probs[symbol], , , seq ## _BITTREE); \
  62         } while (symbol < limit); \
  63         target += symbol - limit; \
  64 } while (0)
  65
  66 #else // HAVE_SMALL
  67
  68 // Unrolled versions
  69 #define seq_4(seq) \
  70         seq ## 0, \
  71         seq ## 1, \
  72         seq ## 2, \
  73         seq ## 3
  74
  75 #define seq_6(seq) \
  76         seq ## 0, \
  77         seq ## 1, \
  78         seq ## 2, \
  79         seq ## 3, \
  80         seq ## 4, \
  81         seq ## 5
  82
  83 #define seq_8(seq) \
  84         seq ## 0, \
  85         seq ## 1, \
  86         seq ## 2, \
  87         seq ## 3, \
  88         seq ## 4, \
  89         seq ## 5, \
  90         seq ## 6, \
  91         seq ## 7
  92
  93 #define seq_len(seq) \
  94         seq ## _CHOICE, \
  95         seq ## _LOW0, \
  96         seq ## _LOW1, \
  97         seq ## _LOW2, \
  98         seq ## _CHOICE2, \
  99         seq ## _MID0, \
 100         seq ## _MID1, \
 101         seq ## _MID2, \
 102         seq ## _HIGH0, \
 103         seq ## _HIGH1, \
 104         seq ## _HIGH2, \
 105         seq ## _HIGH3, \
 106         seq ## _HIGH4, \
 107         seq ## _HIGH5, \
 108         seq ## _HIGH6, \
 109         seq ## _HIGH7
 110
 111 #define len_decode(target, ld, pos_state, seq) \
 112 do { \
 113         symbol = 1; \
 114 case seq ## _CHOICE: \
 115         rc_if_0(ld.choice, seq ## _CHOICE) { \
 116                 rc_update_0(ld.choice); \
 117                 rc_bit_case(ld.low[pos_state][symbol], , , seq ## _LOW0); \
 118                 rc_bit_case(ld.low[pos_state][symbol], , , seq ## _LOW1); \
 119                 rc_bit_case(ld.low[pos_state][symbol], , , seq ## _LOW2); \
 120                 target = symbol - LEN_LOW_SYMBOLS + MATCH_LEN_MIN; \
 121         } else { \
 122                 rc_update_1(ld.choice); \
 123 case seq ## _CHOICE2: \
 124                 rc_if_0(ld.choice2, seq ## _CHOICE2) { \
 125                         rc_update_0(ld.choice2); \
 126                         rc_bit_case(ld.mid[pos_state][symbol], , , \
 127                                         seq ## _MID0); \
 128                         rc_bit_case(ld.mid[pos_state][symbol], , , \
 129                                         seq ## _MID1); \
 130                         rc_bit_case(ld.mid[pos_state][symbol], , , \
 131                                         seq ## _MID2); \
 132                         target = symbol - LEN_MID_SYMBOLS \
 133                                         + MATCH_LEN_MIN + LEN_LOW_SYMBOLS; \
 134                 } else { \
 135                         rc_update_1(ld.choice2); \
 136                         rc_bit_case(ld.high[symbol], , , seq ## _HIGH0); \
 137                         rc_bit_case(ld.high[symbol], , , seq ## _HIGH1); \
 138                         rc_bit_case(ld.high[symbol], , , seq ## _HIGH2); \
 139                         rc_bit_case(ld.high[symbol], , , seq ## _HIGH3); \
 140                         rc_bit_case(ld.high[symbol], , , seq ## _HIGH4); \
 141                         rc_bit_case(ld.high[symbol], , , seq ## _HIGH5); \
 142                         rc_bit_case(ld.high[symbol], , , seq ## _HIGH6); \
 143                         rc_bit_case(ld.high[symbol], , , seq ## _HIGH7); \
 144                         target = symbol - LEN_HIGH_SYMBOLS \
 145                                         + MATCH_LEN_MIN \
 146                                         + LEN_LOW_SYMBOLS + LEN_MID_SYMBOLS; \
 147                 } \
 148         } \
 149 } while (0)
 150
 151 #endif // HAVE_SMALL
 152
 153
 154 /// Length decoder probabilities; see comments in lzma_common.h.
 155 typedef struct {
 156         probability choice;
 157         probability choice2;
 158         probability low[POS_STATES_MAX][LEN_LOW_SYMBOLS];
 159         probability mid[POS_STATES_MAX][LEN_MID_SYMBOLS];
 160         probability high[LEN_HIGH_SYMBOLS];
 161 } lzma_length_decoder;
 162
 163
 164 typedef struct {
 165         ///////////////////
 166         // Probabilities //
 167         ///////////////////
 168
 169         /// Literals; see comments in lzma_common.h.
 170         probability literal[LITERAL_CODERS_MAX][LITERAL_CODER_SIZE];
 171
 172         /// If 1, it's a match. Otherwise it's a single 8-bit literal.
 173         probability is_match[STATES][POS_STATES_MAX];
 174
 175         /// If 1, it's a repeated match. The distance is one of rep0 .. rep3.
 176         probability is_rep[STATES];
 177
 178         /// If 0, distance of a repeated match is rep0.
 179         /// Otherwise check is_rep1.
 180         probability is_rep0[STATES];
 181
 182         /// If 0, distance of a repeated match is rep1.
 183         /// Otherwise check is_rep2.
 184         probability is_rep1[STATES];
 185
 186         /// If 0, distance of a repeated match is rep2. Otherwise it is rep3.
 187         probability is_rep2[STATES];
 188
 189         /// If 1, the repeated match has length of one byte. Otherwise
 190         /// the length is decoded from rep_len_decoder.
 191         probability is_rep0_long[STATES][POS_STATES_MAX];
 192
 193         /// Probability tree for the highest two bits of the match distance.
 194         /// There is a separate probability tree for match lengths of
 195         /// 2 (i.e. MATCH_LEN_MIN), 3, 4, and [5, 273].
 196         probability dist_slot[DIST_STATES][DIST_SLOTS];
 197
 198         /// Probability trees for additional bits for match distance when the
 199         /// distance is in the range [4, 127].
 200         probability pos_special[FULL_DISTANCES - DIST_MODEL_END];
 201
 202         /// Probability tree for the lowest four bits of a match distance
 203         /// that is equal to or greater than 128.
 204         probability pos_align[ALIGN_SIZE];
 205
 206         /// Length of a normal match
 207         lzma_length_decoder match_len_decoder;
 208
 209         /// Length of a repeated match
 210         lzma_length_decoder rep_len_decoder;
 211
 212         ///////////////////
 213         // Decoder state //
 214         ///////////////////
 215
 216         // Range coder
 217         lzma_range_decoder rc;
 218
 219         // Types of the most recently seen LZMA symbols
 220         lzma_lzma_state state;
 221
 222         uint32_t rep0;      ///< Distance of the latest match
 223         uint32_t rep1;      ///< Distance of second latest match
 224         uint32_t rep2;      ///< Distance of third latest match
 225         uint32_t rep3;      ///< Distance of fourth latest match
 226
 227         uint32_t pos_mask; // (1U << pb) - 1
 228         uint32_t literal_context_bits;
 229         uint32_t literal_pos_mask;
 230
 231         /// Uncompressed size as bytes, or LZMA_VLI_UNKNOWN if end of
 232         /// payload marker is expected.
 233         lzma_vli uncompressed_size;
 234
 235         ////////////////////////////////
 236         // State of incomplete symbol //
 237         ////////////////////////////////
 238
 239         /// Position where to continue the decoder loop
 240         enum {
 241                 SEQ_NORMALIZE,
 242                 SEQ_IS_MATCH,
 243                 seq_8(SEQ_LITERAL),
 244                 seq_8(SEQ_LITERAL_MATCHED),
 245                 SEQ_LITERAL_WRITE,
 246                 SEQ_IS_REP,
 247                 seq_len(SEQ_MATCH_LEN),
 248                 seq_6(SEQ_DIST_SLOT),
 249                 SEQ_DIST_MODEL,
 250                 SEQ_DIRECT,
 251                 seq_4(SEQ_ALIGN),
 252                 SEQ_EOPM,
 253                 SEQ_IS_REP0,
 254                 SEQ_SHORTREP,
 255                 SEQ_IS_REP0_LONG,
 256                 SEQ_IS_REP1,
 257                 SEQ_IS_REP2,
 258                 seq_len(SEQ_REP_LEN),
 259                 SEQ_COPY,
 260         } sequence;
 261
 262         /// Base of the current probability tree
 263         probability *probs;
 264
 265         /// Symbol being decoded. This is also used as an index variable in
 266         /// bittree decoders: probs[symbol]
 267         uint32_t symbol;
 268
 269         /// Used as a loop termination condition on bittree decoders and
 270         /// direct bits decoder.
 271         uint32_t limit;
 272
 273         /// Matched literal decoder: 0x100 or 0 to help avoiding branches.
 274         /// Bittree reverse decoders: Offset of the next bit: 1 << offset
 275         uint32_t offset;
 276
 277         /// If decoding a literal: match byte.
 278         /// If decoding a match: length of the match.
 279         uint32_t len;
 280 } lzma_lzma1_decoder;
 281
 282
 283 static lzma_ret
 284 lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr,
 285                 const uint8_t *restrict in,
 286                 size_t *restrict in_pos, size_t in_size)
 287 {
 288         lzma_lzma1_decoder *restrict coder = coder_ptr;
 289
 290         ////////////////////
 291         // Initialization //
 292         ////////////////////
 293
 294         {
 295                 const lzma_ret ret = rc_read_init(
 296                                 &coder->rc, in, in_pos, in_size);
 297                 if (ret != LZMA_STREAM_END)
 298                         return ret;
 299         }
 300
 301         ///////////////
 302         // Variables //
 303         ///////////////
 304
 305         // Making local copies of often-used variables improves both
 306         // speed and readability.
 307
 308         lzma_dict dict = *dictptr;
 309
 310         const size_t dict_start = dict.pos;
 311
 312         // Range decoder
 313         rc_to_local(coder->rc, *in_pos);
 314
 315         // State
 316         uint32_t state = coder->state;
 317         uint32_t rep0 = coder->rep0;
 318         uint32_t rep1 = coder->rep1;
 319         uint32_t rep2 = coder->rep2;
 320         uint32_t rep3 = coder->rep3;
 321
 322         const uint32_t pos_mask = coder->pos_mask;
 323
 324         // These variables are actually needed only if we last time ran
 325         // out of input in the middle of the decoder loop.
 326         probability *probs = coder->probs;
 327         uint32_t symbol = coder->symbol;
 328         uint32_t limit = coder->limit;
 329         uint32_t offset = coder->offset;
 330         uint32_t len = coder->len;
 331
 332         const uint32_t literal_pos_mask = coder->literal_pos_mask;
 333         const uint32_t literal_context_bits = coder->literal_context_bits;
 334
 335         // Temporary variables
 336         uint32_t pos_state = dict.pos & pos_mask;
 337
 338         lzma_ret ret = LZMA_OK;
 339
 340         // If uncompressed size is known, there must be no end of payload
 341         // marker.
 342         const bool no_eopm = coder->uncompressed_size
 343                         != LZMA_VLI_UNKNOWN;
 344         if (no_eopm && coder->uncompressed_size < dict.limit - dict.pos)
 345                 dict.limit = dict.pos + (size_t)(coder->uncompressed_size);
 346
 347         // The main decoder loop. The "switch" is used to restart the decoder at
 348         // correct location. Once restarted, the "switch" is no longer used.
 349         switch (coder->sequence)
 350         while (true) {
 351                 // Calculate new pos_state. This is skipped on the first loop
 352                 // since we already calculated it when setting up the local
 353                 // variables.
 354                 pos_state = dict.pos & pos_mask;
 355
 356         case SEQ_NORMALIZE:
 357         case SEQ_IS_MATCH:
 358                 if (unlikely(no_eopm && dict.pos == dict.limit))
 359                         break;
 360
 361                 rc_if_0(coder->is_match[state][pos_state], SEQ_IS_MATCH) {
 362                         rc_update_0(coder->is_match[state][pos_state]);
 363
 364                         // It's a literal i.e. a single 8-bit byte.
 365
 366                         probs = literal_subcoder(coder->literal,
 367                                         literal_context_bits, literal_pos_mask,
 368                                         dict.pos, dict_get(&dict, 0));
 369                         symbol = 1;
 370
 371                         if (is_literal_state(state)) {
 372                                 // Decode literal without match byte.
 373 #ifdef HAVE_SMALL
 374         case SEQ_LITERAL:
 375                                 do {
 376                                         rc_bit(probs[symbol], , , SEQ_LITERAL);
 377                                 } while (symbol < (1 << 8));
 378 #else
 379                                 rc_bit_case(probs[symbol], , , SEQ_LITERAL0);
 380                                 rc_bit_case(probs[symbol], , , SEQ_LITERAL1);
 381                                 rc_bit_case(probs[symbol], , , SEQ_LITERAL2);
 382                                 rc_bit_case(probs[symbol], , , SEQ_LITERAL3);
 383                                 rc_bit_case(probs[symbol], , , SEQ_LITERAL4);
 384                                 rc_bit_case(probs[symbol], , , SEQ_LITERAL5);
 385                                 rc_bit_case(probs[symbol], , , SEQ_LITERAL6);
 386                                 rc_bit_case(probs[symbol], , , SEQ_LITERAL7);
 387 #endif
 388                         } else {
 389                                 // Decode literal with match byte.
 390                                 //
 391                                 // We store the byte we compare against
 392                                 // ("match byte") to "len" to minimize the
 393                                 // number of variables we need to store
 394                                 // between decoder calls.
 395                                 len = dict_get(&dict, rep0) << 1;
 396
 397                                 // The usage of "offset" allows omitting some
 398                                 // branches, which should give tiny speed
 399                                 // improvement on some CPUs. "offset" gets
 400                                 // set to zero if match_bit didn't match.
 401                                 offset = 0x100;
 402
 403 #ifdef HAVE_SMALL
 404         case SEQ_LITERAL_MATCHED:
 405                                 do {
 406                                         const uint32_t match_bit
 407                                                         = len & offset;
 408                                         const uint32_t subcoder_index
 409                                                         = offset + match_bit
 410                                                         + symbol;
 411
 412                                         rc_bit(probs[subcoder_index],
 413                                                         offset &= ~match_bit,
 414                                                         offset &= match_bit,
 415                                                         SEQ_LITERAL_MATCHED);
 416
 417                                         // It seems to be faster to do this
 418                                         // here instead of putting it to the
 419                                         // beginning of the loop and then
 420                                         // putting the "case" in the middle
 421                                         // of the loop.
 422                                         len <<= 1;
 423
 424                                 } while (symbol < (1 << 8));
 425 #else
 426                                 // Unroll the loop.
 427                                 uint32_t match_bit;
 428                                 uint32_t subcoder_index;
 429
 430 #       define d(seq) \
 431                 case seq: \
 432                         match_bit = len & offset; \
 433                         subcoder_index = offset + match_bit + symbol; \
 434                         rc_bit(probs[subcoder_index], \
 435                                         offset &= ~match_bit, \
 436                                         offset &= match_bit, \
 437                                         seq)
 438
 439                                 d(SEQ_LITERAL_MATCHED0);
 440                                 len <<= 1;
 441                                 d(SEQ_LITERAL_MATCHED1);
 442                                 len <<= 1;
 443                                 d(SEQ_LITERAL_MATCHED2);
 444                                 len <<= 1;
 445                                 d(SEQ_LITERAL_MATCHED3);
 446                                 len <<= 1;
 447                                 d(SEQ_LITERAL_MATCHED4);
 448                                 len <<= 1;
 449                                 d(SEQ_LITERAL_MATCHED5);
 450                                 len <<= 1;
 451                                 d(SEQ_LITERAL_MATCHED6);
 452                                 len <<= 1;
 453                                 d(SEQ_LITERAL_MATCHED7);
 454 #       undef d
 455 #endif
 456                         }
 457
 458                         //update_literal(state);
 459                         // Use a lookup table to update to literal state,
 460                         // since compared to other state updates, this would
 461                         // need two branches.
 462                         static const lzma_lzma_state next_state[] = {
 463                                 STATE_LIT_LIT,
 464                                 STATE_LIT_LIT,
 465                                 STATE_LIT_LIT,
 466                                 STATE_LIT_LIT,
 467                                 STATE_MATCH_LIT_LIT,
 468                                 STATE_REP_LIT_LIT,
 469                                 STATE_SHORTREP_LIT_LIT,
 470                                 STATE_MATCH_LIT,
 471                                 STATE_REP_LIT,
 472                                 STATE_SHORTREP_LIT,
 473                                 STATE_MATCH_LIT,
 474                                 STATE_REP_LIT
 475                         };
 476                         state = next_state[state];
 477
 478         case SEQ_LITERAL_WRITE:
 479                         if (unlikely(dict_put(&dict, symbol))) {
 480                                 coder->sequence = SEQ_LITERAL_WRITE;
 481                                 goto out;
 482                         }
 483
 484                         continue;
 485                 }
 486
 487                 // Instead of a new byte we are going to get a byte range
 488                 // (distance and length) which will be repeated from our
 489                 // output history.
 490
 491                 rc_update_1(coder->is_match[state][pos_state]);
 492
 493         case SEQ_IS_REP:
 494                 rc_if_0(coder->is_rep[state], SEQ_IS_REP) {
 495                         // Not a repeated match
 496                         rc_update_0(coder->is_rep[state]);
 497                         update_match(state);
 498
 499                         // The latest three match distances are kept in
 500                         // memory in case there are repeated matches.
 501                         rep3 = rep2;
 502                         rep2 = rep1;
 503                         rep1 = rep0;
 504
 505                         // Decode the length of the match.
 506                         len_decode(len, coder->match_len_decoder,
 507                                         pos_state, SEQ_MATCH_LEN);
 508
 509                         // Prepare to decode the highest two bits of the
 510                         // match distance.
 511                         probs = coder->dist_slot[get_dist_state(len)];
 512                         symbol = 1;
 513
 514 #ifdef HAVE_SMALL
 515         case SEQ_DIST_SLOT:
 516                         do {
 517                                 rc_bit(probs[symbol], , , SEQ_DIST_SLOT);
 518                         } while (symbol < DIST_SLOTS);
 519 #else
 520                         rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT0);
 521                         rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT1);
 522                         rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT2);
 523                         rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT3);
 524                         rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT4);
 525                         rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT5);
 526 #endif
 527                         // Get rid of the highest bit that was needed for
 528                         // indexing of the probability array.
 529                         symbol -= DIST_SLOTS;
 530                         assert(symbol <= 63);
 531
 532                         if (symbol < DIST_MODEL_START) {
 533                                 // Match distances [0, 3] have only two bits.
 534                                 rep0 = symbol;
 535                         } else {
 536                                 // Decode the lowest [1, 29] bits of
 537                                 // the match distance.
 538                                 limit = (symbol >> 1) - 1;
 539                                 assert(limit >= 1 && limit <= 30);
 540                                 rep0 = 2 + (symbol & 1);
 541
 542                                 if (symbol < DIST_MODEL_END) {
 543                                         // Prepare to decode the low bits for
 544                                         // a distance of [4, 127].
 545                                         assert(limit <= 5);
 546                                         rep0 <<= limit;
 547                                         assert(rep0 <= 96);
 548                                         // -1 is fine, because we start
 549                                         // decoding at probs[1], not probs[0].
 550                                         // NOTE: This violates the C standard,
 551                                         // since we are doing pointer
 552                                         // arithmetic past the beginning of
 553                                         // the array.
 554                                         assert((int32_t)(rep0 - symbol - 1)
 555                                                         >= -1);
 556                                         assert((int32_t)(rep0 - symbol - 1)
 557                                                         <= 82);
 558                                         probs = coder->pos_special + rep0
 559                                                         - symbol - 1;
 560                                         symbol = 1;
 561                                         offset = 0;
 562         case SEQ_DIST_MODEL:
 563 #ifdef HAVE_SMALL
 564                                         do {
 565                                                 rc_bit(probs[symbol], ,
 566                                                         rep0 += 1 << offset,
 567                                                         SEQ_DIST_MODEL);
 568                                         } while (++offset < limit);
 569 #else
 570                                         switch (limit) {
 571                                         case 5:
 572                                                 assert(offset == 0);
 573                                                 rc_bit(probs[symbol], ,
 574                                                         rep0 += 1,
 575                                                         SEQ_DIST_MODEL);
 576                                                 ++offset;
 577                                                 --limit;
 578                                         case 4:
 579                                                 rc_bit(probs[symbol], ,
 580                                                         rep0 += 1 << offset,
 581                                                         SEQ_DIST_MODEL);
 582                                                 ++offset;
 583                                                 --limit;
 584                                         case 3:
 585                                                 rc_bit(probs[symbol], ,
 586                                                         rep0 += 1 << offset,
 587                                                         SEQ_DIST_MODEL);
 588                                                 ++offset;
 589                                                 --limit;
 590                                         case 2:
 591                                                 rc_bit(probs[symbol], ,
 592                                                         rep0 += 1 << offset,
 593                                                         SEQ_DIST_MODEL);
 594                                                 ++offset;
 595                                                 --limit;
 596                                         case 1:
 597                                                 // We need "symbol" only for
 598                                                 // indexing the probability
 599                                                 // array, thus we can use
 600                                                 // rc_bit_last() here to omit
 601                                                 // the unneeded updating of
 602                                                 // "symbol".
 603                                                 rc_bit_last(probs[symbol], ,
 604                                                         rep0 += 1 << offset,
 605                                                         SEQ_DIST_MODEL);
 606                                         }
 607 #endif
 608                                 } else {
 609                                         // The distance is >= 128. Decode the
 610                                         // lower bits without probabilities
 611                                         // except the lowest four bits.
 612                                         assert(symbol >= 14);
 613                                         assert(limit >= 6);
 614                                         limit -= ALIGN_BITS;
 615                                         assert(limit >= 2);
 616         case SEQ_DIRECT:
 617                                         // Not worth manual unrolling
 618                                         do {
 619                                                 rc_direct(rep0, SEQ_DIRECT);
 620                                         } while (--limit > 0);
 621
 622                                         // Decode the lowest four bits using
 623                                         // probabilities.
 624                                         rep0 <<= ALIGN_BITS;
 625                                         symbol = 1;
 626 #ifdef HAVE_SMALL
 627                                         offset = 0;
 628         case SEQ_ALIGN:
 629                                         do {
 630                                                 rc_bit(coder->pos_align[
 631                                                                 symbol], ,
 632                                                         rep0 += 1 << offset,
 633                                                         SEQ_ALIGN);
 634                                         } while (++offset < ALIGN_BITS);
 635 #else
 636         case SEQ_ALIGN0:
 637                                         rc_bit(coder->pos_align[symbol], ,
 638                                                         rep0 += 1, SEQ_ALIGN0);
 639         case SEQ_ALIGN1:
 640                                         rc_bit(coder->pos_align[symbol], ,
 641                                                         rep0 += 2, SEQ_ALIGN1);
 642         case SEQ_ALIGN2:
 643                                         rc_bit(coder->pos_align[symbol], ,
 644                                                         rep0 += 4, SEQ_ALIGN2);
 645         case SEQ_ALIGN3:
 646                                         // Like in SEQ_DIST_MODEL, we don't
 647                                         // need "symbol" for anything else
 648                                         // than indexing the probability array.
 649                                         rc_bit_last(coder->pos_align[symbol], ,
 650                                                         rep0 += 8, SEQ_ALIGN3);
 651 #endif
 652
 653                                         if (rep0 == UINT32_MAX) {
 654                                                 // End of payload marker was
 655                                                 // found. It must not be
 656                                                 // present if uncompressed
 657                                                 // size is known.
 658                                                 if (coder->uncompressed_size
 659                                                 != LZMA_VLI_UNKNOWN) {
 660                                                         ret = LZMA_DATA_ERROR;
 661                                                         goto out;
 662                                                 }
 663
 664         case SEQ_EOPM:
 665                                                 // LZMA1 stream with
 666                                                 // end-of-payload marker.
 667                                                 rc_normalize(SEQ_EOPM);
 668                                                 ret = LZMA_STREAM_END;
 669                                                 goto out;
 670                                         }
 671                                 }
 672                         }
 673
 674                         // Validate the distance we just decoded.
 675                         if (unlikely(!dict_is_distance_valid(&dict, rep0))) {
 676                                 ret = LZMA_DATA_ERROR;
 677                                 goto out;
 678                         }
 679
 680                 } else {
 681                         rc_update_1(coder->is_rep[state]);
 682
 683                         // Repeated match
 684                         //
 685                         // The match distance is a value that we have had
 686                         // earlier. The latest four match distances are
 687                         // available as rep0, rep1, rep2 and rep3. We will
 688                         // now decode which of them is the new distance.
 689                         //
 690                         // There cannot be a match if we haven't produced
 691                         // any output, so check that first.
 692                         if (unlikely(!dict_is_distance_valid(&dict, 0))) {
 693                                 ret = LZMA_DATA_ERROR;
 694                                 goto out;
 695                         }
 696
 697         case SEQ_IS_REP0:
 698                         rc_if_0(coder->is_rep0[state], SEQ_IS_REP0) {
 699                                 rc_update_0(coder->is_rep0[state]);
 700                                 // The distance is rep0.
 701
 702         case SEQ_IS_REP0_LONG:
 703                                 rc_if_0(coder->is_rep0_long[state][pos_state],
 704                                                 SEQ_IS_REP0_LONG) {
 705                                         rc_update_0(coder->is_rep0_long[
 706                                                         state][pos_state]);
 707
 708                                         update_short_rep(state);
 709
 710         case SEQ_SHORTREP:
 711                                         if (unlikely(dict_put(&dict, dict_get(
 712                                                         &dict, rep0)))) {
 713                                                 coder->sequence = SEQ_SHORTREP;
 714                                                 goto out;
 715                                         }
 716
 717                                         continue;
 718                                 }
 719
 720                                 // Repeating more than one byte at
 721                                 // distance of rep0.
 722                                 rc_update_1(coder->is_rep0_long[
 723                                                 state][pos_state]);
 724
 725                         } else {
 726                                 rc_update_1(coder->is_rep0[state]);
 727
 728         case SEQ_IS_REP1:
 729                                 // The distance is rep1, rep2 or rep3. Once
 730                                 // we find out which one of these three, it
 731                                 // is stored to rep0 and rep1, rep2 and rep3
 732                                 // are updated accordingly.
 733                                 rc_if_0(coder->is_rep1[state], SEQ_IS_REP1) {
 734                                         rc_update_0(coder->is_rep1[state]);
 735
 736                                         const uint32_t distance = rep1;
 737                                         rep1 = rep0;
 738                                         rep0 = distance;
 739
 740                                 } else {
 741                                         rc_update_1(coder->is_rep1[state]);
 742         case SEQ_IS_REP2:
 743                                         rc_if_0(coder->is_rep2[state],
 744                                                         SEQ_IS_REP2) {
 745                                                 rc_update_0(coder->is_rep2[
 746                                                                 state]);
 747
 748                                                 const uint32_t distance = rep2;
 749                                                 rep2 = rep1;
 750                                                 rep1 = rep0;
 751                                                 rep0 = distance;
 752
 753                                         } else {
 754                                                 rc_update_1(coder->is_rep2[
 755                                                                 state]);
 756
 757                                                 const uint32_t distance = rep3;
 758                                                 rep3 = rep2;
 759                                                 rep2 = rep1;
 760                                                 rep1 = rep0;
 761                                                 rep0 = distance;
 762                                         }
 763                                 }
 764                         }
 765
 766                         update_long_rep(state);
 767
 768                         // Decode the length of the repeated match.
 769                         len_decode(len, coder->rep_len_decoder,
 770                                         pos_state, SEQ_REP_LEN);
 771                 }
 772
 773                 /////////////////////////////////
 774                 // Repeat from history buffer. //
 775                 /////////////////////////////////
 776
 777                 // The length is always between these limits. There is no way
 778                 // to trigger the algorithm to set len outside this range.
 779                 assert(len >= MATCH_LEN_MIN);
 780                 assert(len <= MATCH_LEN_MAX);
 781
 782         case SEQ_COPY:
 783                 // Repeat len bytes from distance of rep0.
 784                 if (unlikely(dict_repeat(&dict, rep0, &len))) {
 785                         coder->sequence = SEQ_COPY;
 786                         goto out;
 787                 }
 788         }
 789
 790         rc_normalize(SEQ_NORMALIZE);
 791         coder->sequence = SEQ_IS_MATCH;
 792
 793 out:
 794         // Save state
 795
 796         // NOTE: Must not copy dict.limit.
 797         dictptr->pos = dict.pos;
 798         dictptr->full = dict.full;
 799
 800         rc_from_local(coder->rc, *in_pos);
 801
 802         coder->state = state;
 803         coder->rep0 = rep0;
 804         coder->rep1 = rep1;
 805         coder->rep2 = rep2;
 806         coder->rep3 = rep3;
 807
 808         coder->probs = probs;
 809         coder->symbol = symbol;
 810         coder->limit = limit;
 811         coder->offset = offset;
 812         coder->len = len;
 813
 814         // Update the remaining amount of uncompressed data if uncompressed
 815         // size was known.
 816         if (coder->uncompressed_size != LZMA_VLI_UNKNOWN) {
 817                 coder->uncompressed_size -= dict.pos - dict_start;
 818
 819                 // Since there cannot be end of payload marker if the
 820                 // uncompressed size was known, we check here if we
 821                 // finished decoding.
 822                 if (coder->uncompressed_size == 0 && ret == LZMA_OK
 823                                 && coder->sequence != SEQ_NORMALIZE)
 824                         ret = coder->sequence == SEQ_IS_MATCH
 825                                         ? LZMA_STREAM_END : LZMA_DATA_ERROR;
 826         }
 827
 828         // We can do an additional check in the range decoder to catch some
 829         // corrupted files.
 830         if (ret == LZMA_STREAM_END) {
 831                 if (!rc_is_finished(coder->rc))
 832                         ret = LZMA_DATA_ERROR;
 833
 834                 // Reset the range decoder so that it is ready to reinitialize
 835                 // for a new LZMA2 chunk.
 836                 rc_reset(coder->rc);
 837         }
 838
 839         return ret;
 840 }
 841
 842
 843
 844 static void
 845 lzma_decoder_uncompressed(void *coder_ptr, lzma_vli uncompressed_size)
 846 {
 847         lzma_lzma1_decoder *coder = coder_ptr;
 848         coder->uncompressed_size = uncompressed_size;
 849 }
 850
 851
 852 static void
 853 lzma_decoder_reset(void *coder_ptr, const void *opt)
 854 {
 855         lzma_lzma1_decoder *coder = coder_ptr;
 856         const lzma_options_lzma *options = opt;
 857
 858         // NOTE: We assume that lc/lp/pb are valid since they were
 859         // successfully decoded with lzma_lzma_decode_properties().
 860
 861         // Calculate pos_mask. We don't need pos_bits as is for anything.
 862         coder->pos_mask = (1U << options->pb) - 1;
 863
 864         // Initialize the literal decoder.
 865         literal_init(coder->literal, options->lc, options->lp);
 866
 867         coder->literal_context_bits = options->lc;
 868         coder->literal_pos_mask = (1U << options->lp) - 1;
 869
 870         // State
 871         coder->state = STATE_LIT_LIT;
 872         coder->rep0 = 0;
 873         coder->rep1 = 0;
 874         coder->rep2 = 0;
 875         coder->rep3 = 0;
 876         coder->pos_mask = (1U << options->pb) - 1;
 877
 878         // Range decoder
 879         rc_reset(coder->rc);
 880
 881         // Bit and bittree decoders
 882         for (uint32_t i = 0; i < STATES; ++i) {
 883                 for (uint32_t j = 0; j <= coder->pos_mask; ++j) {
 884                         bit_reset(coder->is_match[i][j]);
 885                         bit_reset(coder->is_rep0_long[i][j]);
 886                 }
 887
 888                 bit_reset(coder->is_rep[i]);
 889                 bit_reset(coder->is_rep0[i]);
 890                 bit_reset(coder->is_rep1[i]);
 891                 bit_reset(coder->is_rep2[i]);
 892         }
 893
 894         for (uint32_t i = 0; i < DIST_STATES; ++i)
 895                 bittree_reset(coder->dist_slot[i], DIST_SLOT_BITS);
 896
 897         for (uint32_t i = 0; i < FULL_DISTANCES - DIST_MODEL_END; ++i)
 898                 bit_reset(coder->pos_special[i]);
 899
 900         bittree_reset(coder->pos_align, ALIGN_BITS);
 901
 902         // Len decoders (also bit/bittree)
 903         const uint32_t num_pos_states = 1U << options->pb;
 904         bit_reset(coder->match_len_decoder.choice);
 905         bit_reset(coder->match_len_decoder.choice2);
 906         bit_reset(coder->rep_len_decoder.choice);
 907         bit_reset(coder->rep_len_decoder.choice2);
 908
 909         for (uint32_t pos_state = 0; pos_state < num_pos_states; ++pos_state) {
 910                 bittree_reset(coder->match_len_decoder.low[pos_state],
 911                                 LEN_LOW_BITS);
 912                 bittree_reset(coder->match_len_decoder.mid[pos_state],
 913                                 LEN_MID_BITS);
 914
 915                 bittree_reset(coder->rep_len_decoder.low[pos_state],
 916                                 LEN_LOW_BITS);
 917                 bittree_reset(coder->rep_len_decoder.mid[pos_state],
 918                                 LEN_MID_BITS);
 919         }
 920
 921         bittree_reset(coder->match_len_decoder.high, LEN_HIGH_BITS);
 922         bittree_reset(coder->rep_len_decoder.high, LEN_HIGH_BITS);
 923
 924         coder->sequence = SEQ_IS_MATCH;
 925         coder->probs = NULL;
 926         coder->symbol = 0;
 927         coder->limit = 0;
 928         coder->offset = 0;
 929         coder->len = 0;
 930
 931         return;
 932 }
 933
 934
 935 extern lzma_ret
 936 lzma_lzma_decoder_create(lzma_lz_decoder *lz, const lzma_allocator *allocator,
 937                 const void *opt, lzma_lz_options *lz_options)
 938 {
 939         if (lz->coder == NULL) {
 940                 lz->coder = lzma_alloc(sizeof(lzma_lzma1_decoder), allocator);
 941                 if (lz->coder == NULL)
 942                         return LZMA_MEM_ERROR;
 943
 944                 lz->code = &lzma_decode;
 945                 lz->reset = &lzma_decoder_reset;
 946                 lz->set_uncompressed = &lzma_decoder_uncompressed;
 947         }
 948
 949         // All dictionary sizes are OK here. LZ decoder will take care of
 950         // the special cases.
 951         const lzma_options_lzma *options = opt;
 952         lz_options->dict_size = options->dict_size;
 953         lz_options->preset_dict = options->preset_dict;
 954         lz_options->preset_dict_size = options->preset_dict_size;
 955
 956         return LZMA_OK;
 957 }
 958
 959
 960 /// Allocate and initialize LZMA decoder. This is used only via LZ
 961 /// initialization (lzma_lzma_decoder_init() passes function pointer to
 962 /// the LZ initialization).
 963 static lzma_ret
 964 lzma_decoder_init(lzma_lz_decoder *lz, const lzma_allocator *allocator,
 965                 const void *options, lzma_lz_options *lz_options)
 966 {
 967         if (!is_lclppb_valid(options))
 968                 return LZMA_PROG_ERROR;
 969
 970         return_if_error(lzma_lzma_decoder_create(
 971                         lz, allocator, options, lz_options));
 972
 973         lzma_decoder_reset(lz->coder, options);
 974         lzma_decoder_uncompressed(lz->coder, LZMA_VLI_UNKNOWN);
 975
 976         return LZMA_OK;
 977 }
 978
 979
 980 extern lzma_ret
 981 lzma_lzma_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 982                 const lzma_filter_info *filters)
 983 {
 984         // LZMA can only be the last filter in the chain. This is enforced
 985         // by the raw_decoder initialization.
 986         assert(filters[1].init == NULL);
 987
 988         return lzma_lz_decoder_init(next, allocator, filters,
 989                         &lzma_decoder_init);
 990 }
 991
 992
 993 extern bool
 994 lzma_lzma_lclppb_decode(lzma_options_lzma *options, uint8_t byte)
 995 {
 996         if (byte > (4 * 5 + 4) * 9 + 8)
 997                 return true;
 998
 999         // See the file format specification to understand this.
1000         options->pb = byte / (9 * 5);
1001         byte -= options->pb * 9 * 5;
1002         options->lp = byte / 9;
1003         options->lc = byte - options->lp * 9;
1004
1005         return options->lc + options->lp > LZMA_LCLP_MAX;
1006 }
1007
1008
1009 extern uint64_t
1010 lzma_lzma_decoder_memusage_nocheck(const void *options)
1011 {
1012         const lzma_options_lzma *const opt = options;
1013         return sizeof(lzma_lzma1_decoder)
1014                         + lzma_lz_decoder_memusage(opt->dict_size);
1015 }
1016
1017
1018 extern uint64_t
1019 lzma_lzma_decoder_memusage(const void *options)
1020 {
1021         if (!is_lclppb_valid(options))
1022                 return UINT64_MAX;
1023
1024         return lzma_lzma_decoder_memusage_nocheck(options);
1025 }
1026
1027
1028 extern lzma_ret
1029 lzma_lzma_props_decode(void **options, const lzma_allocator *allocator,
1030                 const uint8_t *props, size_t props_size)
1031 {
1032         if (props_size != 5)
1033                 return LZMA_OPTIONS_ERROR;
1034
1035         lzma_options_lzma *opt
1036                         = lzma_alloc(sizeof(lzma_options_lzma), allocator);
1037         if (opt == NULL)
1038                 return LZMA_MEM_ERROR;
1039
1040         if (lzma_lzma_lclppb_decode(opt, props[0]))
1041                 goto error;
1042
1043         // All dictionary sizes are accepted, including zero. LZ decoder
1044         // will automatically use a dictionary at least a few KiB even if
1045         // a smaller dictionary is requested.
1046         opt->dict_size = unaligned_read32le(props + 1);
1047
1048         opt->preset_dict = NULL;
1049         opt->preset_dict_size = 0;
1050
1051         *options = opt;
1052
1053         return LZMA_OK;
1054
1055 error:
1056         lzma_free(opt, allocator);
1057         return LZMA_OPTIONS_ERROR;
1058 }