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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           10
  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         u16 maincode_decode_table[(1 << LZX_MAINCODE_TABLEBITS) +
  76                                         (LZX_MAINCODE_MAX_NUM_SYMBOLS * 2)]
  77                                         _aligned_attribute(DECODE_TABLE_ALIGNMENT);
  78         u8 maincode_lens[LZX_MAINCODE_MAX_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
  79
  80
  81         u16 lencode_decode_table[(1 << LZX_LENCODE_TABLEBITS) +
  82                                         (LZX_LENCODE_NUM_SYMBOLS * 2)]
  83                                         _aligned_attribute(DECODE_TABLE_ALIGNMENT);
  84         u8 lencode_lens[LZX_LENCODE_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
  85
  86         union {
  87                 u16 alignedcode_decode_table[(1 << LZX_ALIGNEDCODE_TABLEBITS) +
  88                                                 (LZX_ALIGNEDCODE_NUM_SYMBOLS * 2)]
  89                                                 _aligned_attribute(DECODE_TABLE_ALIGNMENT);
  90                 u8 alignedcode_lens[LZX_ALIGNEDCODE_NUM_SYMBOLS];
  91         };
  92
  93         union {
  94                 u16 precode_decode_table[(1 << LZX_PRECODE_TABLEBITS) +
  95                                          (LZX_PRECODE_NUM_SYMBOLS * 2)]
  96                                                 _aligned_attribute(DECODE_TABLE_ALIGNMENT);
  97                 u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS];
  98         };
  99
 100         unsigned window_order;
 101         unsigned num_main_syms;
 102 } _aligned_attribute(DECODE_TABLE_ALIGNMENT);
 103
 104 /* Read a Huffman-encoded symbol using the precode. */
 105 static inline unsigned
 106 read_presym(const struct lzx_decompressor *d, struct input_bitstream *is)
 107 {
 108         return read_huffsym(is, d->precode_decode_table,
 109                             LZX_PRECODE_TABLEBITS, LZX_MAX_PRE_CODEWORD_LEN);
 110 }
 111
 112 /* Read a Huffman-encoded symbol using the main code. */
 113 static inline unsigned
 114 read_mainsym(const struct lzx_decompressor *d, struct input_bitstream *is)
 115 {
 116         return read_huffsym(is, d->maincode_decode_table,
 117                             LZX_MAINCODE_TABLEBITS, LZX_MAX_MAIN_CODEWORD_LEN);
 118 }
 119
 120 /* Read a Huffman-encoded symbol using the length code. */
 121 static inline unsigned
 122 read_lensym(const struct lzx_decompressor *d, struct input_bitstream *is)
 123 {
 124         return read_huffsym(is, d->lencode_decode_table,
 125                             LZX_LENCODE_TABLEBITS, LZX_MAX_LEN_CODEWORD_LEN);
 126 }
 127
 128 /* Read a Huffman-encoded symbol using the aligned offset code. */
 129 static inline unsigned
 130 read_alignedsym(const struct lzx_decompressor *d, struct input_bitstream *is)
 131 {
 132         return read_huffsym(is, d->alignedcode_decode_table,
 133                             LZX_ALIGNEDCODE_TABLEBITS, LZX_MAX_ALIGNED_CODEWORD_LEN);
 134 }
 135
 136 /*
 137  * Read a precode from the compressed input bitstream, then use it to decode
 138  * @num_lens codeword length values and write them to @lens.
 139  */
 140 static int
 141 lzx_read_codeword_lens(struct lzx_decompressor *d, struct input_bitstream *is,
 142                        u8 *lens, unsigned num_lens)
 143 {
 144         u8 *len_ptr = lens;
 145         u8 *lens_end = lens + num_lens;
 146
 147         /* Read the lengths of the precode codewords.  These are stored
 148          * explicitly. */
 149         for (int i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) {
 150                 d->precode_lens[i] =
 151                         bitstream_read_bits(is, LZX_PRECODE_ELEMENT_SIZE);
 152         }
 153
 154         /* Build the decoding table for the precode. */
 155         if (make_huffman_decode_table(d->precode_decode_table,
 156                                       LZX_PRECODE_NUM_SYMBOLS,
 157                                       LZX_PRECODE_TABLEBITS,
 158                                       d->precode_lens,
 159                                       LZX_MAX_PRE_CODEWORD_LEN))
 160                 return -1;
 161
 162         /* Decode the codeword lengths.  */
 163         do {
 164                 unsigned presym;
 165                 u8 len;
 166
 167                 /* Read the next precode symbol.  */
 168                 presym = read_presym(d, is);
 169                 if (presym < 17) {
 170                         /* Difference from old length  */
 171                         len = *len_ptr - presym;
 172                         if ((s8)len < 0)
 173                                 len += 17;
 174                         *len_ptr++ = len;
 175                 } else {
 176                         /* Special RLE values  */
 177
 178                         unsigned run_len;
 179
 180                         if (presym == 17) {
 181                                 /* Run of 0's  */
 182                                 run_len = 4 + bitstream_read_bits(is, 4);
 183                                 len = 0;
 184                         } else if (presym == 18) {
 185                                 /* Longer run of 0's  */
 186                                 run_len = 20 + bitstream_read_bits(is, 5);
 187                                 len = 0;
 188                         } else {
 189                                 /* Run of identical lengths  */
 190                                 run_len = 4 + bitstream_read_bits(is, 1);
 191                                 presym = read_presym(d, is);
 192                                 if (unlikely(presym > 17))
 193                                         return -1;
 194                                 len = *len_ptr - presym;
 195                                 if ((s8)len < 0)
 196                                         len += 17;
 197                         }
 198
 199                         do {
 200                                 *len_ptr++ = len;
 201                         } while (--run_len);
 202                         /*
 203                          * The worst case overrun is when presym == 18,
 204                          * run_len == 20 + 31, and only 1 length was remaining.
 205                          * So LZX_READ_LENS_MAX_OVERRUN == 50.
 206                          *
 207                          * Overrun while reading the first half of maincode_lens
 208                          * can corrupt the previous values in the second half.
 209                          * This doesn't really matter because the resulting
 210                          * lengths will still be in range, and data that
 211                          * generates overruns is invalid anyway.
 212                          */
 213                 }
 214         } while (len_ptr < lens_end);
 215
 216         return 0;
 217 }
 218
 219 /*
 220  * Read the header of an LZX block.  For all block types, the block type and
 221  * size is saved in *block_type_ret and *block_size_ret, respectively.  For
 222  * compressed blocks, the codeword lengths are also saved.  For uncompressed
 223  * blocks, the recent offsets queue is also updated.
 224  */
 225 static int
 226 lzx_read_block_header(struct lzx_decompressor *d, struct input_bitstream *is,
 227                       u32 recent_offsets[], int *block_type_ret,
 228                       u32 *block_size_ret)
 229 {
 230         int block_type;
 231         u32 block_size;
 232
 233         bitstream_ensure_bits(is, 4);
 234
 235         /* Read the block type. */
 236         block_type = bitstream_pop_bits(is, 3);
 237
 238         /* Read the block size. */
 239         if (bitstream_pop_bits(is, 1)) {
 240                 block_size = LZX_DEFAULT_BLOCK_SIZE;
 241         } else {
 242                 block_size = bitstream_read_bits(is, 16);
 243                 if (d->window_order >= 16) {
 244                         block_size <<= 8;
 245                         block_size |= bitstream_read_bits(is, 8);
 246                 }
 247         }
 248
 249         switch (block_type) {
 250
 251         case LZX_BLOCKTYPE_ALIGNED:
 252
 253                 /* Read the aligned offset codeword lengths. */
 254
 255                 for (int i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
 256                         d->alignedcode_lens[i] =
 257                                 bitstream_read_bits(is,
 258                                                     LZX_ALIGNEDCODE_ELEMENT_SIZE);
 259                 }
 260
 261                 /* Fall though, since the rest of the header for aligned offset
 262                  * blocks is the same as that for verbatim blocks.  */
 263
 264         case LZX_BLOCKTYPE_VERBATIM:
 265
 266                 /* Read the main codeword lengths, which are divided into two
 267                  * parts: literal symbols and match headers. */
 268
 269                 if (lzx_read_codeword_lens(d, is, d->maincode_lens,
 270                                            LZX_NUM_CHARS))
 271                         return -1;
 272
 273                 if (lzx_read_codeword_lens(d, is, d->maincode_lens + LZX_NUM_CHARS,
 274                                            d->num_main_syms - LZX_NUM_CHARS))
 275                         return -1;
 276
 277
 278                 /* Read the length codeword lengths. */
 279
 280                 if (lzx_read_codeword_lens(d, is, d->lencode_lens,
 281                                            LZX_LENCODE_NUM_SYMBOLS))
 282                         return -1;
 283
 284                 break;
 285
 286         case LZX_BLOCKTYPE_UNCOMPRESSED:
 287                 /*
 288                  * The header of an uncompressed block contains new values for
 289                  * the recent offsets queue, starting on the next 16-bit
 290                  * boundary in the bitstream.  Careful: if the stream is
 291                  * *already* aligned, the correct thing to do is to throw away
 292                  * the next 16 bits (this is probably a mistake in the format).
 293                  */
 294                 bitstream_ensure_bits(is, 1);
 295                 bitstream_align(is);
 296                 recent_offsets[0] = bitstream_read_u32(is);
 297                 recent_offsets[1] = bitstream_read_u32(is);
 298                 recent_offsets[2] = bitstream_read_u32(is);
 299
 300                 /* Offsets of 0 are invalid.  */
 301                 if (recent_offsets[0] == 0 || recent_offsets[1] == 0 ||
 302                     recent_offsets[2] == 0)
 303                         return -1;
 304                 break;
 305
 306         default:
 307                 /* Unrecognized block type.  */
 308                 return -1;
 309         }
 310
 311         *block_type_ret = block_type;
 312         *block_size_ret = block_size;
 313         return 0;
 314 }
 315
 316 /* Decompress a block of LZX-compressed data. */
 317 static int
 318 lzx_decompress_block(struct lzx_decompressor *d, struct input_bitstream *is,
 319                      int block_type, u32 block_size,
 320                      u8 * const out_begin, u8 *out_next, u32 recent_offsets[])
 321 {
 322         u8 * const block_end = out_next + block_size;
 323         unsigned min_aligned_offset_slot;
 324
 325         /*
 326          * Build the Huffman decode tables.  We always need to build the main
 327          * and length decode tables.  For aligned blocks we additionally need to
 328          * build the aligned offset decode table.
 329          */
 330
 331         if (make_huffman_decode_table(d->maincode_decode_table,
 332                                       d->num_main_syms,
 333                                       LZX_MAINCODE_TABLEBITS,
 334                                       d->maincode_lens,
 335                                       LZX_MAX_MAIN_CODEWORD_LEN))
 336                 return -1;
 337
 338         if (make_huffman_decode_table(d->lencode_decode_table,
 339                                       LZX_LENCODE_NUM_SYMBOLS,
 340                                       LZX_LENCODE_TABLEBITS,
 341                                       d->lencode_lens,
 342                                       LZX_MAX_LEN_CODEWORD_LEN))
 343                 return -1;
 344
 345         if (block_type == LZX_BLOCKTYPE_ALIGNED) {
 346                 if (make_huffman_decode_table(d->alignedcode_decode_table,
 347                                               LZX_ALIGNEDCODE_NUM_SYMBOLS,
 348                                               LZX_ALIGNEDCODE_TABLEBITS,
 349                                               d->alignedcode_lens,
 350                                               LZX_MAX_ALIGNED_CODEWORD_LEN))
 351                         return -1;
 352                 min_aligned_offset_slot = 8;
 353         } else {
 354                 min_aligned_offset_slot = LZX_MAX_OFFSET_SLOTS;
 355         }
 356
 357         /* Decode the literals and matches. */
 358
 359         do {
 360                 unsigned mainsym;
 361                 unsigned length;
 362                 u32 offset;
 363                 unsigned offset_slot;
 364                 unsigned num_extra_bits;
 365
 366                 mainsym = read_mainsym(d, is);
 367                 if (mainsym < LZX_NUM_CHARS) {
 368                         /* Literal */
 369                         *out_next++ = mainsym;
 370                         continue;
 371                 }
 372
 373                 /* Match */
 374
 375                 /* Decode the length header and offset slot.  */
 376                 STATIC_ASSERT(LZX_NUM_CHARS % LZX_NUM_LEN_HEADERS == 0);
 377                 length = mainsym % LZX_NUM_LEN_HEADERS;
 378                 offset_slot = (mainsym - LZX_NUM_CHARS) / LZX_NUM_LEN_HEADERS;
 379
 380                 /* If needed, read a length symbol to decode the full length. */
 381                 if (length == LZX_NUM_PRIMARY_LENS)
 382                         length += read_lensym(d, is);
 383                 length += LZX_MIN_MATCH_LEN;
 384
 385                 if (offset_slot < LZX_NUM_RECENT_OFFSETS) {
 386                         /* Repeat offset  */
 387
 388                         /* Note: This isn't a real LRU queue, since using the R2
 389                          * offset doesn't bump the R1 offset down to R2. */
 390                         offset = recent_offsets[offset_slot];
 391                         recent_offsets[offset_slot] = recent_offsets[0];
 392                 } else {
 393                         /* Explicit offset  */
 394
 395                         /* Look up the number of extra bits that need to be read
 396                          * to decode offsets with this offset slot.  */
 397                         num_extra_bits = lzx_extra_offset_bits[offset_slot];
 398
 399                         /* Start with the offset slot base value.  */
 400                         offset = lzx_offset_slot_base[offset_slot];
 401
 402                         /* In aligned offset blocks, the low-order 3 bits of
 403                          * each offset are encoded using the aligned offset
 404                          * code.  Otherwise, all the extra bits are literal.  */
 405
 406                         if (offset_slot >= min_aligned_offset_slot) {
 407                                 offset +=
 408                                         bitstream_read_bits(is,
 409                                                             num_extra_bits -
 410                                                                 LZX_NUM_ALIGNED_OFFSET_BITS)
 411                                                         << LZX_NUM_ALIGNED_OFFSET_BITS;
 412                                 offset += read_alignedsym(d, is);
 413                         } else {
 414                                 offset += bitstream_read_bits(is, num_extra_bits);
 415                         }
 416
 417                         /* Adjust the offset.  */
 418                         offset -= LZX_OFFSET_ADJUSTMENT;
 419
 420                         /* Update the match offset LRU queue.  */
 421                         STATIC_ASSERT(LZX_NUM_RECENT_OFFSETS == 3);
 422                         recent_offsets[2] = recent_offsets[1];
 423                         recent_offsets[1] = recent_offsets[0];
 424                 }
 425                 recent_offsets[0] = offset;
 426
 427                 /* Validate the match, then copy it to the current position.  */
 428
 429                 if (unlikely(length > block_end - out_next))
 430                         return -1;
 431
 432                 if (unlikely(offset > out_next - out_begin))
 433                         return -1;
 434
 435                 lz_copy(out_next, length, offset, block_end, LZX_MIN_MATCH_LEN);
 436
 437                 out_next += length;
 438
 439         } while (out_next != block_end);
 440
 441         return 0;
 442 }
 443
 444 static int
 445 lzx_decompress(const void *restrict compressed_data, size_t compressed_size,
 446                void *restrict uncompressed_data, size_t uncompressed_size,
 447                void *restrict _d)
 448 {
 449         struct lzx_decompressor *d = _d;
 450         u8 * const out_begin = uncompressed_data;
 451         u8 *out_next = out_begin;
 452         u8 * const out_end = out_begin + uncompressed_size;
 453         struct input_bitstream is;
 454         STATIC_ASSERT(LZX_NUM_RECENT_OFFSETS == 3);
 455         u32 recent_offsets[LZX_NUM_RECENT_OFFSETS] = {1, 1, 1};
 456         unsigned may_have_e8_byte = 0;
 457
 458         init_input_bitstream(&is, compressed_data, compressed_size);
 459
 460         /* Codeword lengths begin as all 0's for delta encoding purposes. */
 461         memset(d->maincode_lens, 0, d->num_main_syms);
 462         memset(d->lencode_lens, 0, LZX_LENCODE_NUM_SYMBOLS);
 463
 464         /* Decompress blocks until we have all the uncompressed data. */
 465
 466         while (out_next != out_end) {
 467                 int block_type;
 468                 u32 block_size;
 469
 470                 if (lzx_read_block_header(d, &is, recent_offsets,
 471                                           &block_type, &block_size))
 472                         return -1;
 473
 474                 if (block_size < 1 || block_size > out_end - out_next)
 475                         return -1;
 476
 477                 if (likely(block_type != LZX_BLOCKTYPE_UNCOMPRESSED)) {
 478
 479                         /* Compressed block */
 480                         if (lzx_decompress_block(d, &is, block_type, block_size,
 481                                                  out_begin, out_next,
 482                                                  recent_offsets))
 483                                 return -1;
 484
 485                         /* If the first E8 byte was in this block, then it must
 486                          * have been encoded as a literal using mainsym E8. */
 487                         may_have_e8_byte |= d->maincode_lens[0xE8];
 488                 } else {
 489
 490                         /* Uncompressed block */
 491                         if (bitstream_read_bytes(&is, out_next, block_size))
 492                                 return -1;
 493
 494                         /* Re-align the bitstream if needed. */
 495                         if (block_size & 1)
 496                                 bitstream_read_byte(&is);
 497
 498                         /* There may have been an E8 byte in the block. */
 499                         may_have_e8_byte = 1;
 500                 }
 501                 out_next += block_size;
 502         }
 503
 504         /* Postprocess the data unless it cannot possibly contain E8 bytes. */
 505         if (may_have_e8_byte)
 506                 lzx_postprocess(uncompressed_data, uncompressed_size);
 507
 508         return 0;
 509 }
 510
 511 static int
 512 lzx_create_decompressor(size_t max_block_size, void **d_ret)
 513 {
 514         unsigned window_order;
 515         struct lzx_decompressor *d;
 516
 517         window_order = lzx_get_window_order(max_block_size);
 518         if (window_order == 0)
 519                 return WIMLIB_ERR_INVALID_PARAM;
 520
 521         d = ALIGNED_MALLOC(sizeof(*d), DECODE_TABLE_ALIGNMENT);
 522         if (!d)
 523                 return WIMLIB_ERR_NOMEM;
 524
 525         d->window_order = window_order;
 526         d->num_main_syms = lzx_get_num_main_syms(window_order);
 527
 528         *d_ret = d;
 529         return 0;
 530 }
 531
 532 static void
 533 lzx_free_decompressor(void *_d)
 534 {
 535         ALIGNED_FREE(_d);
 536 }
 537
 538 const struct decompressor_ops lzx_decompressor_ops = {
 539         .create_decompressor = lzx_create_decompressor,
 540         .decompress          = lzx_decompress,
 541         .free_decompressor   = lzx_free_decompressor,
 542 };