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   1 /*
   2  * lzx-decompress.c
   3  *
   4  * A very fast decompressor for LZX, as used in WIM files.
   5  */
   6
   7 /*
   8  * Copyright (C) 2012, 2013, 2014 Eric Biggers
   9  *
  10  * This file is part of wimlib, a library for working with WIM files.
  11  *
  12  * wimlib is free software; you can redistribute it and/or modify it under the
  13  * terms of the GNU General Public License as published by the Free
  14  * Software Foundation; either version 3 of the License, or (at your option)
  15  * any later version.
  16  *
  17  * wimlib is distributed in the hope that it will be useful, but WITHOUT ANY
  18  * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  19  * A PARTICULAR PURPOSE. See the GNU General Public License for more
  20  * details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with wimlib; if not, see http://www.gnu.org/licenses/.
  24  */
  25
  26 /*
  27  * LZX is an LZ77 and Huffman-code based compression format that has many
  28  * similarities to DEFLATE (the format used by zlib/gzip).  The compression
  29  * ratio is as good or better than DEFLATE.  See lzx-compress.c for a format
  30  * overview, and see https://en.wikipedia.org/wiki/LZX_(algorithm) for a
  31  * historical overview.  Here I make some pragmatic notes.
  32  *
  33  * The old specification for LZX is the document "Microsoft LZX Data Compression
  34  * Format" (1997).  It defines the LZX format as used in cabinet files.  Allowed
  35  * window sizes are 2^n where 15 <= n <= 21.  However, this document contains
  36  * several errors, so don't read too much into it...
  37  *
  38  * The new specification for LZX is the document "[MS-PATCH]: LZX DELTA
  39  * Compression and Decompression" (2014).  It defines the LZX format as used by
  40  * Microsoft's binary patcher.  It corrects several errors in the 1997 document
  41  * and extends the format in several ways --- namely, optional reference data,
  42  * up to 2^25 byte windows, and longer match lengths.
  43  *
  44  * WIM files use a more restricted form of LZX.  No LZX DELTA extensions are
  45  * present, the window is not "sliding", E8 preprocessing is done
  46  * unconditionally with a fixed file size, and the maximum window size is always
  47  * 2^15 bytes (equal to the size of each "chunk" in a compressed WIM resource).
  48  * This code is primarily intended to implement this form of LZX.  But although
  49  * not compatible with WIMGAPI, this code also supports maximum window sizes up
  50  * to 2^21 bytes.
  51  *
  52  * TODO: Add support for window sizes up to 2^25 bytes.
  53  */
  54
  55 #ifdef HAVE_CONFIG_H
  56 #  include "config.h"
  57 #endif
  58
  59 #include "wimlib/decompressor_ops.h"
  60 #include "wimlib/decompress_common.h"
  61 #include "wimlib/error.h"
  62 #include "wimlib/lzx.h"
  63 #include "wimlib/util.h"
  64
  65 #include <string.h>
  66
  67 /* These values are chosen for fast decompression.  */
  68 #define LZX_MAINCODE_TABLEBITS          11
  69 #define LZX_LENCODE_TABLEBITS           10
  70 #define LZX_PRECODE_TABLEBITS           6
  71 #define LZX_ALIGNEDCODE_TABLEBITS       7
  72
  73 #define LZX_READ_LENS_MAX_OVERRUN 50
  74
  75 /* Huffman decoding tables, and arrays that map symbols to codeword lengths.  */
  76 struct lzx_tables {
  77
  78         u16 maincode_decode_table[(1 << LZX_MAINCODE_TABLEBITS) +
  79                                         (LZX_MAINCODE_MAX_NUM_SYMBOLS * 2)]
  80                                         _aligned_attribute(DECODE_TABLE_ALIGNMENT);
  81         u8 maincode_lens[LZX_MAINCODE_MAX_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
  82
  83
  84         u16 lencode_decode_table[(1 << LZX_LENCODE_TABLEBITS) +
  85                                         (LZX_LENCODE_NUM_SYMBOLS * 2)]
  86                                         _aligned_attribute(DECODE_TABLE_ALIGNMENT);
  87         u8 lencode_lens[LZX_LENCODE_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
  88
  89
  90         u16 alignedcode_decode_table[(1 << LZX_ALIGNEDCODE_TABLEBITS) +
  91                                         (LZX_ALIGNEDCODE_NUM_SYMBOLS * 2)]
  92                                         _aligned_attribute(DECODE_TABLE_ALIGNMENT);
  93         u8 alignedcode_lens[LZX_ALIGNEDCODE_NUM_SYMBOLS];
  94 } _aligned_attribute(DECODE_TABLE_ALIGNMENT);
  95
  96 /* The main LZX decompressor structure.
  97  *
  98  * Note: we keep track of most of the decompression state outside this
  99  * structure.  This structure only exists so that (1) we can store @window_order
 100  * and @num_main_syms for multiple calls to lzx_decompress(); and (2) so that we
 101  * don't have to allocate the large 'struct lzx_tables' on the stack.  */
 102 struct lzx_decompressor {
 103         unsigned window_order;
 104         unsigned num_main_syms;
 105         struct lzx_tables tables;
 106 };
 107
 108 /* Read a Huffman-encoded symbol using the precode.  */
 109 static inline u16
 110 read_huffsym_using_precode(struct input_bitstream *istream,
 111                            const u16 precode_decode_table[])
 112 {
 113         return read_huffsym(istream, precode_decode_table,
 114                             LZX_PRECODE_TABLEBITS, LZX_MAX_PRE_CODEWORD_LEN);
 115 }
 116
 117 /* Read a Huffman-encoded symbol using the main code.  */
 118 static inline u16
 119 read_huffsym_using_maincode(struct input_bitstream *istream,
 120                             const struct lzx_tables *tables)
 121 {
 122         return read_huffsym(istream, tables->maincode_decode_table,
 123                             LZX_MAINCODE_TABLEBITS, LZX_MAX_MAIN_CODEWORD_LEN);
 124 }
 125
 126 /* Read a Huffman-encoded symbol using the length code.  */
 127 static inline u16
 128 read_huffsym_using_lencode(struct input_bitstream *istream,
 129                            const struct lzx_tables *tables)
 130 {
 131         return read_huffsym(istream, tables->lencode_decode_table,
 132                             LZX_LENCODE_TABLEBITS, LZX_MAX_LEN_CODEWORD_LEN);
 133 }
 134
 135 /* Read a Huffman-encoded symbol using the aligned offset code.  */
 136 static inline u16
 137 read_huffsym_using_alignedcode(struct input_bitstream *istream,
 138                                const struct lzx_tables *tables)
 139 {
 140         return read_huffsym(istream, tables->alignedcode_decode_table,
 141                             LZX_ALIGNEDCODE_TABLEBITS, LZX_MAX_ALIGNED_CODEWORD_LEN);
 142 }
 143
 144 /*
 145  * Read the precode from the compressed input bitstream, then use it to decode
 146  * @num_lens codeword length values.
 147  *
 148  * @istream:
 149  *      The input bitstream.
 150  *
 151  * @lens:
 152  *      An array that contains the length values from the previous time the
 153  *      codeword lengths for this Huffman code were read, or all 0's if this is
 154  *      the first time.  This array must have at least (@num_lens +
 155  *      LZX_READ_LENS_MAX_OVERRUN) entries.
 156  *
 157  * @num_lens:
 158  *      Number of length values to decode.
 159  *
 160  * Returns 0 on success, or -1 if the data was invalid.
 161  */
 162 static int
 163 lzx_read_codeword_lens(struct input_bitstream *istream, u8 *lens, unsigned num_lens)
 164 {
 165         u16 precode_decode_table[(1 << LZX_PRECODE_TABLEBITS) +
 166                                         (LZX_PRECODE_NUM_SYMBOLS * 2)]
 167                                         _aligned_attribute(DECODE_TABLE_ALIGNMENT);
 168         u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS];
 169         u8 *len_ptr = lens;
 170         u8 *lens_end = lens + num_lens;
 171         int ret;
 172
 173         /* Read the lengths of the precode codewords.  These are given
 174          * explicitly.  */
 175         for (int i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) {
 176                 precode_lens[i] = bitstream_read_bits(istream,
 177                                                       LZX_PRECODE_ELEMENT_SIZE);
 178         }
 179
 180         /* Make the decoding table for the precode.  */
 181         ret = make_huffman_decode_table(precode_decode_table,
 182                                         LZX_PRECODE_NUM_SYMBOLS,
 183                                         LZX_PRECODE_TABLEBITS,
 184                                         precode_lens,
 185                                         LZX_MAX_PRE_CODEWORD_LEN);
 186         if (ret)
 187                 return ret;
 188
 189         /* Decode the codeword lengths.  */
 190         do {
 191                 unsigned presym;
 192                 u8 len;
 193
 194                 /* Read the next precode symbol.  */
 195                 presym = read_huffsym_using_precode(istream,
 196                                                     precode_decode_table);
 197                 if (presym < 17) {
 198                         /* Difference from old length  */
 199                         len = *len_ptr - presym;
 200                         if ((s8)len < 0)
 201                                 len += 17;
 202                         *len_ptr++ = len;
 203                 } else {
 204                         /* Special RLE values  */
 205
 206                         unsigned run_len;
 207
 208                         if (presym == 17) {
 209                                 /* Run of 0's  */
 210                                 run_len = 4 + bitstream_read_bits(istream, 4);
 211                                 len = 0;
 212                         } else if (presym == 18) {
 213                                 /* Longer run of 0's  */
 214                                 run_len = 20 + bitstream_read_bits(istream, 5);
 215                                 len = 0;
 216                         } else {
 217                                 /* Run of identical lengths  */
 218                                 run_len = 4 + bitstream_read_bits(istream, 1);
 219                                 presym = read_huffsym_using_precode(istream,
 220                                                                     precode_decode_table);
 221                                 len = *len_ptr - presym;
 222                                 if ((s8)len < 0)
 223                                         len += 17;
 224                         }
 225
 226                         do {
 227                                 *len_ptr++ = len;
 228                         } while (--run_len);
 229                         /* Worst case overrun is when presym == 18,
 230                          * run_len == 20 + 31, and only 1 length was remaining.
 231                          * So LZX_READ_LENS_MAX_OVERRUN == 50.
 232                          *
 233                          * Overrun while reading the first half of maincode_lens
 234                          * can corrupt the previous values in the second half.
 235                          * This doesn't really matter because the resulting
 236                          * lengths will still be in range, and data that
 237                          * generates overruns is invalid anyway.  */
 238                 }
 239         } while (len_ptr < lens_end);
 240         return 0;
 241 }
 242
 243 /*
 244  * Read the header of an LZX block and save the block type and size in
 245  * *block_type_ret and *block_size_ret, respectively.
 246  *
 247  * If the block is compressed, also update the Huffman decode @tables with the
 248  * new Huffman codes.
 249  *
 250  * If the block is uncompressed, also update the match offset @queue with the
 251  * new match offsets.
 252  *
 253  * Return 0 on success, or -1 if the data was invalid.
 254  */
 255 static int
 256 lzx_read_block_header(struct input_bitstream *istream,
 257                       unsigned num_main_syms,
 258                       unsigned window_order,
 259                       int *block_type_ret,
 260                       u32 *block_size_ret,
 261                       struct lzx_tables *tables,
 262                       struct lzx_lru_queue *queue)
 263 {
 264         int block_type;
 265         u32 block_size;
 266         int ret;
 267
 268         bitstream_ensure_bits(istream, 4);
 269
 270         /* The first three bits tell us what kind of block it is, and should be
 271          * one of the LZX_BLOCKTYPE_* values.  */
 272         block_type = bitstream_pop_bits(istream, 3);
 273
 274         /* Read the block size.  This mirrors the behavior of
 275          * lzx_write_compressed_block() in lzx-compress.c; see that for more
 276          * details.  */
 277         if (bitstream_pop_bits(istream, 1)) {
 278                 block_size = LZX_DEFAULT_BLOCK_SIZE;
 279         } else {
 280                 u32 tmp;
 281                 block_size = 0;
 282
 283                 tmp = bitstream_read_bits(istream, 8);
 284                 block_size |= tmp;
 285                 tmp = bitstream_read_bits(istream, 8);
 286                 block_size <<= 8;
 287                 block_size |= tmp;
 288
 289                 if (window_order >= 16) {
 290                         tmp = bitstream_read_bits(istream, 8);
 291                         block_size <<= 8;
 292                         block_size |= tmp;
 293                 }
 294         }
 295
 296         switch (block_type) {
 297
 298         case LZX_BLOCKTYPE_ALIGNED:
 299
 300                 /* Read the aligned offset code and prepare its decode table.
 301                  */
 302
 303                 for (int i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
 304                         tables->alignedcode_lens[i] =
 305                                 bitstream_read_bits(istream,
 306                                                     LZX_ALIGNEDCODE_ELEMENT_SIZE);
 307                 }
 308
 309                 ret = make_huffman_decode_table(tables->alignedcode_decode_table,
 310                                                 LZX_ALIGNEDCODE_NUM_SYMBOLS,
 311                                                 LZX_ALIGNEDCODE_TABLEBITS,
 312                                                 tables->alignedcode_lens,
 313                                                 LZX_MAX_ALIGNED_CODEWORD_LEN);
 314                 if (ret)
 315                         return ret;
 316
 317                 /* Fall though, since the rest of the header for aligned offset
 318                  * blocks is the same as that for verbatim blocks.  */
 319
 320         case LZX_BLOCKTYPE_VERBATIM:
 321
 322                 /* Read the main code and prepare its decode table.
 323                  *
 324                  * Note that the codeword lengths in the main code are encoded
 325                  * in two parts: one part for literal symbols, and one part for
 326                  * match symbols.  */
 327
 328                 ret = lzx_read_codeword_lens(istream, tables->maincode_lens,
 329                                              LZX_NUM_CHARS);
 330                 if (ret)
 331                         return ret;
 332
 333                 ret = lzx_read_codeword_lens(istream,
 334                                              tables->maincode_lens + LZX_NUM_CHARS,
 335                                              num_main_syms - LZX_NUM_CHARS);
 336                 if (ret)
 337                         return ret;
 338
 339                 ret = make_huffman_decode_table(tables->maincode_decode_table,
 340                                                 num_main_syms,
 341                                                 LZX_MAINCODE_TABLEBITS,
 342                                                 tables->maincode_lens,
 343                                                 LZX_MAX_MAIN_CODEWORD_LEN);
 344                 if (ret)
 345                         return ret;
 346
 347                 /* Read the length code and prepare its decode table.  */
 348
 349                 ret = lzx_read_codeword_lens(istream, tables->lencode_lens,
 350                                              LZX_LENCODE_NUM_SYMBOLS);
 351                 if (ret)
 352                         return ret;
 353
 354                 ret = make_huffman_decode_table(tables->lencode_decode_table,
 355                                                 LZX_LENCODE_NUM_SYMBOLS,
 356                                                 LZX_LENCODE_TABLEBITS,
 357                                                 tables->lencode_lens,
 358                                                 LZX_MAX_LEN_CODEWORD_LEN);
 359                 if (ret)
 360                         return ret;
 361
 362                 break;
 363
 364         case LZX_BLOCKTYPE_UNCOMPRESSED:
 365
 366                 /* Before reading the three LRU match offsets from the
 367                  * uncompressed block header, the stream must be aligned on a
 368                  * 16-bit boundary.  But, unexpectedly, if the stream is
 369                  * *already* aligned, the correct thing to do is to throw away
 370                  * the next 16 bits.  */
 371
 372                 bitstream_ensure_bits(istream, 1);
 373                 bitstream_align(istream);
 374                 queue->R[0] = bitstream_read_u32(istream);
 375                 queue->R[1] = bitstream_read_u32(istream);
 376                 queue->R[2] = bitstream_read_u32(istream);
 377
 378                 /* Offsets of 0 are invalid.  */
 379                 if (queue->R[0] == 0 || queue->R[1] == 0 || queue->R[2] == 0)
 380                         return -1;
 381                 break;
 382
 383         default:
 384                 /* Unrecognized block type.  */
 385                 return -1;
 386         }
 387
 388         *block_type_ret = block_type;
 389         *block_size_ret = block_size;
 390         return 0;
 391 }
 392
 393 /*
 394  * Decompress an LZX-compressed block of data.
 395  *
 396  * @block_type:
 397  *      The type of the block (LZX_BLOCKTYPE_VERBATIM or LZX_BLOCKTYPE_ALIGNED).
 398  *
 399  * @block_size:
 400  *      The size of the block, in bytes.
 401  *
 402  * @window:
 403  *      Pointer to the beginning of the decompression window.
 404  *
 405  * @window_pos:
 406  *      The position in the window at which the block starts.
 407  *
 408  * @tables:
 409  *      The Huffman decoding tables for the block.
 410  *
 411  * @queue:
 412  *      The least-recently-used queue for match offsets.
 413  *
 414  * @istream:
 415  *      The input bitstream, positioned at the start of the block data.
 416  *
 417  * Returns 0 on success, or -1 if the data was invalid.
 418  */
 419 static int
 420 lzx_decompress_block(int block_type, u32 block_size,
 421                      u8 *window, u32 window_pos,
 422                      const struct lzx_tables *tables,
 423                      struct lzx_lru_queue *queue,
 424                      struct input_bitstream *istream)
 425 {
 426         u8 *window_ptr = &window[window_pos];
 427         u8 *window_end = window_ptr + block_size;
 428         unsigned mainsym;
 429         u32 match_len;
 430         unsigned offset_slot;
 431         u32 match_offset;
 432         unsigned num_extra_bits;
 433         unsigned ones_if_aligned = 0U - (block_type == LZX_BLOCKTYPE_ALIGNED);
 434
 435         while (window_ptr != window_end) {
 436
 437                 mainsym = read_huffsym_using_maincode(istream, tables);
 438                 if (mainsym < LZX_NUM_CHARS) {
 439                         /* Literal  */
 440                         *window_ptr++ = mainsym;
 441                         continue;
 442                 }
 443
 444                 /* Match  */
 445
 446                 /* Decode the length header and offset slot.  */
 447                 mainsym -= LZX_NUM_CHARS;
 448                 match_len = mainsym & 0x7;
 449                 offset_slot = mainsym >> 3;
 450
 451                 /* If needed, read a length symbol to decode the full length. */
 452                 if (match_len == 0x7)
 453                         match_len += read_huffsym_using_lencode(istream, tables);
 454                 match_len += LZX_MIN_MATCH_LEN;
 455
 456                 if (offset_slot <= 2) {
 457                         /* Repeat offset  */
 458
 459                         /* Note: This isn't a real LRU queue, since using the R2
 460                          * offset doesn't bump the R1 offset down to R2.  This
 461                          * quirk allows all 3 recent offsets to be handled by
 462                          * the same code.  (For R0, the swap is a no-op.)  */
 463                         match_offset = queue->R[offset_slot];
 464                         queue->R[offset_slot] = queue->R[0];
 465                         queue->R[0] = match_offset;
 466                 } else {
 467                         /* Explicit offset  */
 468
 469                         /* Look up the number of extra bits that need to be read
 470                          * to decode offsets with this offset slot.  */
 471                         num_extra_bits = lzx_extra_offset_bits[offset_slot];
 472
 473                         /* Start with the offset slot base value.  */
 474                         match_offset = lzx_offset_slot_base[offset_slot];
 475
 476                         /* In aligned offset blocks, the low-order 3 bits of
 477                          * each offset are encoded using the aligned offset
 478                          * code.  Otherwise, all the extra bits are literal.  */
 479
 480                         /*if (block_type == LZX_BLOCKTYPE_ALIGNED && num_extra_bits >= 3) {*/
 481                         if ((num_extra_bits & ones_if_aligned) >= 3) {
 482                                 match_offset += bitstream_read_bits(istream, num_extra_bits - 3) << 3;
 483                                 match_offset += read_huffsym_using_alignedcode(istream, tables);
 484                         } else {
 485                                 match_offset += bitstream_read_bits(istream, num_extra_bits);
 486                         }
 487
 488                         /* Adjust the offset.  */
 489                         match_offset -= LZX_OFFSET_OFFSET;
 490
 491                         /* Update the match offset LRU queue.  */
 492                         queue->R[2] = queue->R[1];
 493                         queue->R[1] = queue->R[0];
 494                         queue->R[0] = match_offset;
 495                 }
 496
 497                 /* Validate the match, then copy it to the current position.  */
 498
 499                 if (unlikely(match_len > window_end - window_ptr))
 500                         return -1;
 501
 502                 if (unlikely(match_offset > window_ptr - window))
 503                         return -1;
 504
 505                 lz_copy(window_ptr, match_len, match_offset, window_end);
 506
 507                 window_ptr += match_len;
 508         }
 509         return 0;
 510 }
 511
 512 static int
 513 lzx_decompress(const void *compressed_data, size_t compressed_size,
 514                void *uncompressed_data, size_t uncompressed_size,
 515                void *_dec)
 516 {
 517         struct lzx_decompressor *dec = _dec;
 518         struct input_bitstream istream;
 519         struct lzx_lru_queue queue;
 520         u32 window_pos;
 521         int block_type;
 522         u32 block_size;
 523         bool may_have_e8_byte;
 524         int ret;
 525
 526         init_input_bitstream(&istream, compressed_data, compressed_size);
 527
 528         /* Initialize the recent offsets queue.  */
 529         lzx_lru_queue_init(&queue);
 530
 531         /* Codeword lengths begin as all 0's for delta encoding purposes.  */
 532         memset(dec->tables.maincode_lens, 0, dec->num_main_syms);
 533         memset(dec->tables.lencode_lens, 0, LZX_LENCODE_NUM_SYMBOLS);
 534
 535         /* Set this to true if there may be 0xe8 bytes in the uncompressed data.
 536          */
 537         may_have_e8_byte = false;
 538
 539         /* The compressed data will consist of one or more blocks.  The
 540          * following loop decompresses one block, and it runs until there all
 541          * the compressed data has been decompressed, so there are no more
 542          * blocks.  */
 543
 544         for (window_pos = 0;
 545              window_pos < uncompressed_size;
 546              window_pos += block_size)
 547         {
 548                 ret = lzx_read_block_header(&istream, dec->num_main_syms,
 549                                             dec->window_order, &block_type,
 550                                             &block_size, &dec->tables, &queue);
 551                 if (ret)
 552                         return ret;
 553
 554                 if (block_size > uncompressed_size - window_pos)
 555                         return -1;
 556
 557                 if (block_type != LZX_BLOCKTYPE_UNCOMPRESSED) {
 558
 559                         /* Compressed block.  */
 560
 561                         ret = lzx_decompress_block(block_type,
 562                                                    block_size,
 563                                                    uncompressed_data,
 564                                                    window_pos,
 565                                                    &dec->tables,
 566                                                    &queue,
 567                                                    &istream);
 568                         if (ret)
 569                                 return ret;
 570
 571                         /* If the first 0xe8 byte was in this block, it must
 572                          * have been encoded as a literal using mainsym 0xe8. */
 573                         if (dec->tables.maincode_lens[0xe8] != 0)
 574                                 may_have_e8_byte = true;
 575                 } else {
 576
 577                         /* Uncompressed block.  */
 578                         const u8 *p;
 579
 580                         p = bitstream_read_bytes(&istream, block_size);
 581                         if (!p)
 582                                 return -1;
 583
 584                         memcpy(&((u8*)uncompressed_data)[window_pos], p, block_size);
 585
 586                         /* Re-align the bitstream if an odd number of bytes was
 587                          * read.  */
 588                         if (block_size & 1)
 589                                 bitstream_read_byte(&istream);
 590
 591                         may_have_e8_byte = true;
 592                 }
 593         }
 594
 595         /* Postprocess the data unless it cannot possibly contain 0xe8 bytes  */
 596         if (may_have_e8_byte)
 597                 lzx_undo_e8_preprocessing(uncompressed_data, uncompressed_size);
 598
 599         return 0;
 600 }
 601
 602 static void
 603 lzx_free_decompressor(void *_dec)
 604 {
 605         struct lzx_decompressor *dec = _dec;
 606
 607         ALIGNED_FREE(dec);
 608 }
 609
 610 static int
 611 lzx_create_decompressor(size_t max_block_size, void **dec_ret)
 612 {
 613         struct lzx_decompressor *dec;
 614         unsigned window_order;
 615
 616         window_order = lzx_get_window_order(max_block_size);
 617         if (window_order == 0)
 618                 return WIMLIB_ERR_INVALID_PARAM;
 619
 620         /* The aligned allocation is needed to ensure that the lzx_tables are
 621          * aligned properly.  */
 622         dec = ALIGNED_MALLOC(sizeof(struct lzx_decompressor),
 623                              DECODE_TABLE_ALIGNMENT);
 624         if (!dec)
 625                 return WIMLIB_ERR_NOMEM;
 626
 627         dec->window_order = window_order;
 628         dec->num_main_syms = lzx_get_num_main_syms(window_order);
 629
 630         *dec_ret = dec;
 631         return 0;
 632 }
 633
 634 const struct decompressor_ops lzx_decompressor_ops = {
 635         .create_decompressor = lzx_create_decompressor,
 636         .decompress          = lzx_decompress,
 637         .free_decompressor   = lzx_free_decompressor,
 638 };