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   1 /*
   2  * lzx_decompress.c
   3  *
   4  * A decompressor for the LZX compression format, as used in WIM files.
   5  */
   6
   7 /*
   8  * Copyright (C) 2012-2016 Eric Biggers
   9  *
  10  * This file is free software; you can redistribute it and/or modify it under
  11  * the terms of the GNU Lesser General Public License as published by the Free
  12  * Software Foundation; either version 3 of the License, or (at your option) any
  13  * later version.
  14  *
  15  * This file is distributed in the hope that it will be useful, but WITHOUT
  16  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  17  * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
  18  * details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public License
  21  * along with this file; if not, see http://www.gnu.org/licenses/.
  22  */
  23
  24 /*
  25  * LZX is an LZ77 and Huffman-code based compression format that has many
  26  * similarities to DEFLATE (the format used by zlib/gzip).  The compression
  27  * ratio is as good or better than DEFLATE.  See lzx_compress.c for a format
  28  * overview, and see https://en.wikipedia.org/wiki/LZX_(algorithm) for a
  29  * historical overview.  Here I make some pragmatic notes.
  30  *
  31  * The old specification for LZX is the document "Microsoft LZX Data Compression
  32  * Format" (1997).  It defines the LZX format as used in cabinet files.  Allowed
  33  * window sizes are 2^n where 15 <= n <= 21.  However, this document contains
  34  * several errors, so don't read too much into it...
  35  *
  36  * The new specification for LZX is the document "[MS-PATCH]: LZX DELTA
  37  * Compression and Decompression" (2014).  It defines the LZX format as used by
  38  * Microsoft's binary patcher.  It corrects several errors in the 1997 document
  39  * and extends the format in several ways --- namely, optional reference data,
  40  * up to 2^25 byte windows, and longer match lengths.
  41  *
  42  * WIM files use a more restricted form of LZX.  No LZX DELTA extensions are
  43  * present, the window is not "sliding", E8 preprocessing is done
  44  * unconditionally with a fixed file size, and the maximum window size is always
  45  * 2^15 bytes (equal to the size of each "chunk" in a compressed WIM resource).
  46  * This code is primarily intended to implement this form of LZX.  But although
  47  * not compatible with WIMGAPI, this code also supports maximum window sizes up
  48  * to 2^21 bytes.
  49  *
  50  * TODO: Add support for window sizes up to 2^25 bytes.
  51  */
  52
  53 #ifdef HAVE_CONFIG_H
  54 #  include "config.h"
  55 #endif
  56
  57 #include <string.h>
  58
  59 #include "wimlib/decompressor_ops.h"
  60 #include "wimlib/decompress_common.h"
  61 #include "wimlib/error.h"
  62 #include "wimlib/lzx_common.h"
  63 #include "wimlib/util.h"
  64
  65 /* These values are chosen for fast decompression.  */
  66 #define LZX_MAINCODE_TABLEBITS          11
  67 #define LZX_LENCODE_TABLEBITS           9
  68 #define LZX_PRECODE_TABLEBITS           6
  69 #define LZX_ALIGNEDCODE_TABLEBITS       7
  70
  71 #define LZX_READ_LENS_MAX_OVERRUN 50
  72
  73 struct lzx_decompressor {
  74
  75         DECODE_TABLE(maincode_decode_table, LZX_MAINCODE_MAX_NUM_SYMBOLS,
  76                      LZX_MAINCODE_TABLEBITS, LZX_MAX_MAIN_CODEWORD_LEN);
  77         u8 maincode_lens[LZX_MAINCODE_MAX_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
  78
  79         DECODE_TABLE(lencode_decode_table, LZX_LENCODE_NUM_SYMBOLS,
  80                      LZX_LENCODE_TABLEBITS, LZX_MAX_LEN_CODEWORD_LEN);
  81         u8 lencode_lens[LZX_LENCODE_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
  82
  83         union {
  84                 DECODE_TABLE(alignedcode_decode_table, LZX_ALIGNEDCODE_NUM_SYMBOLS,
  85                              LZX_ALIGNEDCODE_TABLEBITS, LZX_MAX_ALIGNED_CODEWORD_LEN);
  86                 u8 alignedcode_lens[LZX_ALIGNEDCODE_NUM_SYMBOLS];
  87         };
  88
  89         union {
  90                 DECODE_TABLE(precode_decode_table, LZX_PRECODE_NUM_SYMBOLS,
  91                              LZX_PRECODE_TABLEBITS, LZX_MAX_PRE_CODEWORD_LEN);
  92                 u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS];
  93                 u8 extra_offset_bits[LZX_MAX_OFFSET_SLOTS];
  94         };
  95
  96         unsigned window_order;
  97         unsigned num_main_syms;
  98
  99         /* Like lzx_extra_offset_bits[], but does not include the entropy-coded
 100          * bits of aligned offset blocks */
 101         u8 extra_offset_bits_minus_aligned[LZX_MAX_OFFSET_SLOTS];
 102
 103 } _aligned_attribute(DECODE_TABLE_ALIGNMENT);
 104
 105 /* Read a Huffman-encoded symbol using the precode. */
 106 static inline unsigned
 107 read_presym(const struct lzx_decompressor *d, struct input_bitstream *is)
 108 {
 109         return read_huffsym(is, d->precode_decode_table,
 110                             LZX_PRECODE_TABLEBITS, LZX_MAX_PRE_CODEWORD_LEN);
 111 }
 112
 113 /* Read a Huffman-encoded symbol using the main code. */
 114 static inline unsigned
 115 read_mainsym(const struct lzx_decompressor *d, struct input_bitstream *is)
 116 {
 117         return read_huffsym(is, d->maincode_decode_table,
 118                             LZX_MAINCODE_TABLEBITS, LZX_MAX_MAIN_CODEWORD_LEN);
 119 }
 120
 121 /* Read a Huffman-encoded symbol using the length code. */
 122 static inline unsigned
 123 read_lensym(const struct lzx_decompressor *d, struct input_bitstream *is)
 124 {
 125         return read_huffsym(is, d->lencode_decode_table,
 126                             LZX_LENCODE_TABLEBITS, LZX_MAX_LEN_CODEWORD_LEN);
 127 }
 128
 129 /* Read a Huffman-encoded symbol using the aligned offset code. */
 130 static inline unsigned
 131 read_alignedsym(const struct lzx_decompressor *d, struct input_bitstream *is)
 132 {
 133         return read_huffsym(is, d->alignedcode_decode_table,
 134                             LZX_ALIGNEDCODE_TABLEBITS, LZX_MAX_ALIGNED_CODEWORD_LEN);
 135 }
 136
 137 /*
 138  * Read a precode from the compressed input bitstream, then use it to decode
 139  * @num_lens codeword length values and write them to @lens.
 140  */
 141 static int
 142 lzx_read_codeword_lens(struct lzx_decompressor *d, struct input_bitstream *is,
 143                        u8 *lens, unsigned num_lens)
 144 {
 145         u8 *len_ptr = lens;
 146         u8 *lens_end = lens + num_lens;
 147
 148         /* Read the lengths of the precode codewords.  These are stored
 149          * explicitly. */
 150         for (int i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) {
 151                 d->precode_lens[i] =
 152                         bitstream_read_bits(is, LZX_PRECODE_ELEMENT_SIZE);
 153         }
 154
 155         /* Build the decoding table for the precode. */
 156         if (make_huffman_decode_table(d->precode_decode_table,
 157                                       LZX_PRECODE_NUM_SYMBOLS,
 158                                       LZX_PRECODE_TABLEBITS,
 159                                       d->precode_lens,
 160                                       LZX_MAX_PRE_CODEWORD_LEN))
 161                 return -1;
 162
 163         /* Decode the codeword lengths.  */
 164         do {
 165                 unsigned presym;
 166                 u8 len;
 167
 168                 /* Read the next precode symbol.  */
 169                 presym = read_presym(d, is);
 170                 if (presym < 17) {
 171                         /* Difference from old length  */
 172                         len = *len_ptr - presym;
 173                         if ((s8)len < 0)
 174                                 len += 17;
 175                         *len_ptr++ = len;
 176                 } else {
 177                         /* Special RLE values  */
 178
 179                         unsigned run_len;
 180
 181                         if (presym == 17) {
 182                                 /* Run of 0's  */
 183                                 run_len = 4 + bitstream_read_bits(is, 4);
 184                                 len = 0;
 185                         } else if (presym == 18) {
 186                                 /* Longer run of 0's  */
 187                                 run_len = 20 + bitstream_read_bits(is, 5);
 188                                 len = 0;
 189                         } else {
 190                                 /* Run of identical lengths  */
 191                                 run_len = 4 + bitstream_read_bits(is, 1);
 192                                 presym = read_presym(d, is);
 193                                 if (unlikely(presym > 17))
 194                                         return -1;
 195                                 len = *len_ptr - presym;
 196                                 if ((s8)len < 0)
 197                                         len += 17;
 198                         }
 199
 200                         do {
 201                                 *len_ptr++ = len;
 202                         } while (--run_len);
 203                         /*
 204                          * The worst case overrun is when presym == 18,
 205                          * run_len == 20 + 31, and only 1 length was remaining.
 206                          * So LZX_READ_LENS_MAX_OVERRUN == 50.
 207                          *
 208                          * Overrun while reading the first half of maincode_lens
 209                          * can corrupt the previous values in the second half.
 210                          * This doesn't really matter because the resulting
 211                          * lengths will still be in range, and data that
 212                          * generates overruns is invalid anyway.
 213                          */
 214                 }
 215         } while (len_ptr < lens_end);
 216
 217         return 0;
 218 }
 219
 220 /*
 221  * Read the header of an LZX block.  For all block types, the block type and
 222  * size is saved in *block_type_ret and *block_size_ret, respectively.  For
 223  * compressed blocks, the codeword lengths are also saved.  For uncompressed
 224  * blocks, the recent offsets queue is also updated.
 225  */
 226 static int
 227 lzx_read_block_header(struct lzx_decompressor *d, struct input_bitstream *is,
 228                       u32 recent_offsets[], int *block_type_ret,
 229                       u32 *block_size_ret)
 230 {
 231         int block_type;
 232         u32 block_size;
 233
 234         bitstream_ensure_bits(is, 4);
 235
 236         /* Read the block type. */
 237         block_type = bitstream_pop_bits(is, 3);
 238
 239         /* Read the block size. */
 240         if (bitstream_pop_bits(is, 1)) {
 241                 block_size = LZX_DEFAULT_BLOCK_SIZE;
 242         } else {
 243                 block_size = bitstream_read_bits(is, 16);
 244                 if (d->window_order >= 16) {
 245                         block_size <<= 8;
 246                         block_size |= bitstream_read_bits(is, 8);
 247                 }
 248         }
 249
 250         switch (block_type) {
 251
 252         case LZX_BLOCKTYPE_ALIGNED:
 253
 254                 /* Read the aligned offset codeword lengths. */
 255
 256                 for (int i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
 257                         d->alignedcode_lens[i] =
 258                                 bitstream_read_bits(is,
 259                                                     LZX_ALIGNEDCODE_ELEMENT_SIZE);
 260                 }
 261
 262                 /* Fall though, since the rest of the header for aligned offset
 263                  * blocks is the same as that for verbatim blocks.  */
 264
 265         case LZX_BLOCKTYPE_VERBATIM:
 266
 267                 /* Read the main codeword lengths, which are divided into two
 268                  * parts: literal symbols and match headers. */
 269
 270                 if (lzx_read_codeword_lens(d, is, d->maincode_lens,
 271                                            LZX_NUM_CHARS))
 272                         return -1;
 273
 274                 if (lzx_read_codeword_lens(d, is, d->maincode_lens + LZX_NUM_CHARS,
 275                                            d->num_main_syms - LZX_NUM_CHARS))
 276                         return -1;
 277
 278
 279                 /* Read the length codeword lengths. */
 280
 281                 if (lzx_read_codeword_lens(d, is, d->lencode_lens,
 282                                            LZX_LENCODE_NUM_SYMBOLS))
 283                         return -1;
 284
 285                 break;
 286
 287         case LZX_BLOCKTYPE_UNCOMPRESSED:
 288                 /*
 289                  * The header of an uncompressed block contains new values for
 290                  * the recent offsets queue, starting on the next 16-bit
 291                  * boundary in the bitstream.  Careful: if the stream is
 292                  * *already* aligned, the correct thing to do is to throw away
 293                  * the next 16 bits (this is probably a mistake in the format).
 294                  */
 295                 bitstream_ensure_bits(is, 1);
 296                 bitstream_align(is);
 297                 recent_offsets[0] = bitstream_read_u32(is);
 298                 recent_offsets[1] = bitstream_read_u32(is);
 299                 recent_offsets[2] = bitstream_read_u32(is);
 300
 301                 /* Offsets of 0 are invalid.  */
 302                 if (recent_offsets[0] == 0 || recent_offsets[1] == 0 ||
 303                     recent_offsets[2] == 0)
 304                         return -1;
 305                 break;
 306
 307         default:
 308                 /* Unrecognized block type.  */
 309                 return -1;
 310         }
 311
 312         *block_type_ret = block_type;
 313         *block_size_ret = block_size;
 314         return 0;
 315 }
 316
 317 /* Decompress a block of LZX-compressed data. */
 318 static int
 319 lzx_decompress_block(struct lzx_decompressor *d, struct input_bitstream *is,
 320                      int block_type, u32 block_size,
 321                      u8 * const out_begin, u8 *out_next, u32 recent_offsets[])
 322 {
 323         u8 * const block_end = out_next + block_size;
 324         unsigned min_aligned_offset_slot;
 325
 326         /*
 327          * Build the Huffman decode tables.  We always need to build the main
 328          * and length decode tables.  For aligned blocks we additionally need to
 329          * build the aligned offset decode table.
 330          */
 331
 332         if (make_huffman_decode_table(d->maincode_decode_table,
 333                                       d->num_main_syms,
 334                                       LZX_MAINCODE_TABLEBITS,
 335                                       d->maincode_lens,
 336                                       LZX_MAX_MAIN_CODEWORD_LEN))
 337                 return -1;
 338
 339         if (make_huffman_decode_table(d->lencode_decode_table,
 340                                       LZX_LENCODE_NUM_SYMBOLS,
 341                                       LZX_LENCODE_TABLEBITS,
 342                                       d->lencode_lens,
 343                                       LZX_MAX_LEN_CODEWORD_LEN))
 344                 return -1;
 345
 346         if (block_type == LZX_BLOCKTYPE_ALIGNED) {
 347                 if (make_huffman_decode_table(d->alignedcode_decode_table,
 348                                               LZX_ALIGNEDCODE_NUM_SYMBOLS,
 349                                               LZX_ALIGNEDCODE_TABLEBITS,
 350                                               d->alignedcode_lens,
 351                                               LZX_MAX_ALIGNED_CODEWORD_LEN))
 352                         return -1;
 353                 min_aligned_offset_slot = LZX_MIN_ALIGNED_OFFSET_SLOT;
 354                 memcpy(d->extra_offset_bits, d->extra_offset_bits_minus_aligned,
 355                        sizeof(lzx_extra_offset_bits));
 356         } else {
 357                 min_aligned_offset_slot = LZX_MAX_OFFSET_SLOTS;
 358                 memcpy(d->extra_offset_bits, lzx_extra_offset_bits,
 359                        sizeof(lzx_extra_offset_bits));
 360         }
 361
 362         /* Decode the literals and matches. */
 363
 364         do {
 365                 unsigned mainsym;
 366                 unsigned length;
 367                 u32 offset;
 368                 unsigned offset_slot;
 369
 370                 mainsym = read_mainsym(d, is);
 371                 if (mainsym < LZX_NUM_CHARS) {
 372                         /* Literal */
 373                         *out_next++ = mainsym;
 374                         continue;
 375                 }
 376
 377                 /* Match */
 378
 379                 /* Decode the length header and offset slot.  */
 380                 STATIC_ASSERT(LZX_NUM_CHARS % LZX_NUM_LEN_HEADERS == 0);
 381                 length = mainsym % LZX_NUM_LEN_HEADERS;
 382                 offset_slot = (mainsym - LZX_NUM_CHARS) / LZX_NUM_LEN_HEADERS;
 383
 384                 /* If needed, read a length symbol to decode the full length. */
 385                 if (length == LZX_NUM_PRIMARY_LENS)
 386                         length += read_lensym(d, is);
 387                 length += LZX_MIN_MATCH_LEN;
 388
 389                 if (offset_slot < LZX_NUM_RECENT_OFFSETS) {
 390                         /* Repeat offset  */
 391
 392                         /* Note: This isn't a real LRU queue, since using the R2
 393                          * offset doesn't bump the R1 offset down to R2. */
 394                         offset = recent_offsets[offset_slot];
 395                         recent_offsets[offset_slot] = recent_offsets[0];
 396                 } else {
 397                         /* Explicit offset  */
 398                         offset = bitstream_read_bits(is, d->extra_offset_bits[offset_slot]);
 399                         if (offset_slot >= min_aligned_offset_slot) {
 400                                 offset = (offset << LZX_NUM_ALIGNED_OFFSET_BITS) |
 401                                          read_alignedsym(d, is);
 402                         }
 403                         offset += lzx_offset_slot_base[offset_slot];
 404
 405                         /* Update the match offset LRU queue.  */
 406                         STATIC_ASSERT(LZX_NUM_RECENT_OFFSETS == 3);
 407                         recent_offsets[2] = recent_offsets[1];
 408                         recent_offsets[1] = recent_offsets[0];
 409                 }
 410                 recent_offsets[0] = offset;
 411
 412                 /* Validate the match and copy it to the current position.  */
 413                 if (unlikely(lz_copy(length, offset, out_begin,
 414                                      out_next, block_end, LZX_MIN_MATCH_LEN)))
 415                         return -1;
 416                 out_next += length;
 417         } while (out_next != block_end);
 418
 419         return 0;
 420 }
 421
 422 static int
 423 lzx_decompress(const void *restrict compressed_data, size_t compressed_size,
 424                void *restrict uncompressed_data, size_t uncompressed_size,
 425                void *restrict _d)
 426 {
 427         struct lzx_decompressor *d = _d;
 428         u8 * const out_begin = uncompressed_data;
 429         u8 *out_next = out_begin;
 430         u8 * const out_end = out_begin + uncompressed_size;
 431         struct input_bitstream is;
 432         STATIC_ASSERT(LZX_NUM_RECENT_OFFSETS == 3);
 433         u32 recent_offsets[LZX_NUM_RECENT_OFFSETS] = {1, 1, 1};
 434         unsigned may_have_e8_byte = 0;
 435
 436         init_input_bitstream(&is, compressed_data, compressed_size);
 437
 438         /* Codeword lengths begin as all 0's for delta encoding purposes. */
 439         memset(d->maincode_lens, 0, d->num_main_syms);
 440         memset(d->lencode_lens, 0, LZX_LENCODE_NUM_SYMBOLS);
 441
 442         /* Decompress blocks until we have all the uncompressed data. */
 443
 444         while (out_next != out_end) {
 445                 int block_type;
 446                 u32 block_size;
 447
 448                 if (lzx_read_block_header(d, &is, recent_offsets,
 449                                           &block_type, &block_size))
 450                         return -1;
 451
 452                 if (block_size < 1 || block_size > out_end - out_next)
 453                         return -1;
 454
 455                 if (likely(block_type != LZX_BLOCKTYPE_UNCOMPRESSED)) {
 456
 457                         /* Compressed block */
 458                         if (lzx_decompress_block(d, &is, block_type, block_size,
 459                                                  out_begin, out_next,
 460                                                  recent_offsets))
 461                                 return -1;
 462
 463                         /* If the first E8 byte was in this block, then it must
 464                          * have been encoded as a literal using mainsym E8. */
 465                         may_have_e8_byte |= d->maincode_lens[0xE8];
 466                 } else {
 467
 468                         /* Uncompressed block */
 469                         if (bitstream_read_bytes(&is, out_next, block_size))
 470                                 return -1;
 471
 472                         /* Re-align the bitstream if needed. */
 473                         if (block_size & 1)
 474                                 bitstream_read_byte(&is);
 475
 476                         /* There may have been an E8 byte in the block. */
 477                         may_have_e8_byte = 1;
 478                 }
 479                 out_next += block_size;
 480         }
 481
 482         /* Postprocess the data unless it cannot possibly contain E8 bytes. */
 483         if (may_have_e8_byte)
 484                 lzx_postprocess(uncompressed_data, uncompressed_size);
 485
 486         return 0;
 487 }
 488
 489 static int
 490 lzx_create_decompressor(size_t max_block_size, void **d_ret)
 491 {
 492         unsigned window_order;
 493         struct lzx_decompressor *d;
 494
 495         window_order = lzx_get_window_order(max_block_size);
 496         if (window_order == 0)
 497                 return WIMLIB_ERR_INVALID_PARAM;
 498
 499         d = ALIGNED_MALLOC(sizeof(*d), DECODE_TABLE_ALIGNMENT);
 500         if (!d)
 501                 return WIMLIB_ERR_NOMEM;
 502
 503         d->window_order = window_order;
 504         d->num_main_syms = lzx_get_num_main_syms(window_order);
 505
 506         /* Initialize 'd->extra_offset_bits_minus_aligned'. */
 507         STATIC_ASSERT(sizeof(d->extra_offset_bits_minus_aligned) ==
 508                       sizeof(lzx_extra_offset_bits));
 509         STATIC_ASSERT(sizeof(d->extra_offset_bits) ==
 510                       sizeof(lzx_extra_offset_bits));
 511         memcpy(d->extra_offset_bits_minus_aligned, lzx_extra_offset_bits,
 512                sizeof(lzx_extra_offset_bits));
 513         for (unsigned offset_slot = LZX_MIN_ALIGNED_OFFSET_SLOT;
 514              offset_slot < LZX_MAX_OFFSET_SLOTS; offset_slot++)
 515         {
 516                 d->extra_offset_bits_minus_aligned[offset_slot] -=
 517                                 LZX_NUM_ALIGNED_OFFSET_BITS;
 518         }
 519
 520         *d_ret = d;
 521         return 0;
 522 }
 523
 524 static void
 525 lzx_free_decompressor(void *_d)
 526 {
 527         ALIGNED_FREE(_d);
 528 }
 529
 530 const struct decompressor_ops lzx_decompressor_ops = {
 531         .create_decompressor = lzx_create_decompressor,
 532         .decompress          = lzx_decompress,
 533         .free_decompressor   = lzx_free_decompressor,
 534 };