4 * LZX decompression routines, originally based on code taken from cabextract
5 * v0.5, which was, itself, a modified version of the lzx decompression code
10 * Copyright (C) 2012, 2013, 2014 Eric Biggers
12 * This file is part of wimlib, a library for working with WIM files.
14 * wimlib is free software; you can redistribute it and/or modify it under the
15 * terms of the GNU General Public License as published by the Free
16 * Software Foundation; either version 3 of the License, or (at your option)
19 * wimlib is distributed in the hope that it will be useful, but WITHOUT ANY
20 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
21 * A PARTICULAR PURPOSE. See the GNU General Public License for more
24 * You should have received a copy of the GNU General Public License
25 * along with wimlib; if not, see http://www.gnu.org/licenses/.
29 * LZX is an LZ77 and Huffman-code based compression format that has many
30 * similarities to the DEFLATE format used in zlib. The compression ratio is as
31 * good or better than DEFLATE.
33 * Some notes on the LZX compression format as used in Windows Imaging (WIM)
36 * A compressed WIM resource consists of a table of chunk offsets followed by
37 * the compressed chunks themselves. All compressed chunks except possibly the
38 * last decompress to a fixed number of bytes, by default 32768. This is quite
39 * similar to the cabinet (.cab) file format, but they are not the same.
40 * According to the cabinet format documentation, the LZX block size is
41 * independent from the CFDATA blocks, and an LZX block may span several CFDATA
42 * blocks. However, in WIMs, LZX blocks do not appear to ever span multiple WIM
43 * chunks. Note that this means any WIM chunk may be decompressed or compressed
44 * independently from any other chunk, which allows random access.
46 * An LZX compressed WIM chunk contains one or more LZX blocks of the aligned,
47 * verbatim, or uncompressed block types. For aligned and verbatim blocks, the
48 * size of the block in uncompressed bytes is specified by a bit following the 3
49 * bits that specify the block type, possibly followed by an additional 16 bits.
50 * '1' means to use the default block size (equal to 32768, the default size of
51 * a WIM chunk), while '0' means that the block size is provided by the next 16
54 * The cabinet format, as documented, allows for the possibility that a
55 * compressed CFDATA chunk is up to 6144 bytes larger than the data it
56 * uncompresses to. However, in the WIM format it appears that every chunk that
57 * would be 32768 bytes or more when compressed is actually stored fully
60 * The 'e8' preprocessing step that changes x86 call instructions to use
61 * absolute offsets instead of relative offsets relies on a filesize parameter.
62 * There is no such parameter for this in the WIM files (even though the size of
63 * the file resource could be used for this purpose), and instead a magic file
64 * size of 12000000 is used. The 'e8' preprocessing is always done, and there
65 * is no bit to indicate whether it is done or not.
69 * Some more notes about errors in Microsoft's LZX documentation:
71 * Microsoft's LZX document and their implementation of the com.ms.util.cab Java
72 * package do not concur.
74 * In the LZX document, there is a table showing the correlation between window
75 * size and the number of position slots. It states that the 1MB window = 40
76 * slots and the 2MB window = 42 slots. In the implementation, 1MB = 42 slots,
77 * 2MB = 50 slots. The actual calculation is 'find the first slot whose position
78 * base is equal to or more than the required window size'. This would explain
79 * why other tables in the document refer to 50 slots rather than 42.
81 * The constant NUM_PRIMARY_LENS used in the decompression pseudocode is not
82 * defined in the specification.
84 * The LZX document states that aligned offset blocks have their aligned offset
85 * Huffman tree AFTER the main and length trees. The implementation suggests
86 * that the aligned offset tree is BEFORE the main and length trees.
88 * The LZX document decoding algorithm states that, in an aligned offset block,
89 * if an extra_bits value is 1, 2 or 3, then that number of bits should be read
90 * and the result added to the match offset. This is correct for 1 and 2, but
91 * not 3, where just a Huffman symbol (using the aligned tree) should be read.
93 * Regarding the E8 preprocessing, the LZX document states 'No translation may
94 * be performed on the last 6 bytes of the input block'. This is correct.
95 * However, the pseudocode provided checks for the *E8 leader* up to the last 6
96 * bytes. If the leader appears between -10 and -7 bytes from the end, this
97 * would cause the next four bytes to be modified, at least one of which would
98 * be in the last 6 bytes, which is not allowed according to the spec.
100 * The specification states that the Huffman trees must always contain at least
101 * one element. However, many CAB files contain blocks where the length tree is
102 * completely empty (because there are no matches), and this is expected to
111 #include "wimlib/decompressor_ops.h"
112 #include "wimlib/decompress_common.h"
113 #include "wimlib/lzx.h"
114 #include "wimlib/util.h"
119 # include <emmintrin.h>
122 /* Huffman decoding tables and maps from symbols to code lengths. */
125 u16 maintree_decode_table[(1 << LZX_MAINCODE_TABLEBITS) +
126 (LZX_MAINCODE_MAX_NUM_SYMBOLS * 2)]
127 _aligned_attribute(DECODE_TABLE_ALIGNMENT);
128 u8 maintree_lens[LZX_MAINCODE_MAX_NUM_SYMBOLS];
131 u16 lentree_decode_table[(1 << LZX_LENCODE_TABLEBITS) +
132 (LZX_LENCODE_NUM_SYMBOLS * 2)]
133 _aligned_attribute(DECODE_TABLE_ALIGNMENT);
134 u8 lentree_lens[LZX_LENCODE_NUM_SYMBOLS];
137 u16 alignedtree_decode_table[(1 << LZX_ALIGNEDCODE_TABLEBITS) +
138 (LZX_ALIGNEDCODE_NUM_SYMBOLS * 2)]
139 _aligned_attribute(DECODE_TABLE_ALIGNMENT);
140 u8 alignedtree_lens[LZX_ALIGNEDCODE_NUM_SYMBOLS];
141 } _aligned_attribute(DECODE_TABLE_ALIGNMENT);
143 struct lzx_decompressor {
145 unsigned num_main_syms;
146 struct lzx_tables tables;
150 * Reads a Huffman-encoded symbol using the pre-tree.
153 read_huffsym_using_pretree(struct input_bitstream *istream,
154 const u16 pretree_decode_table[])
156 return read_huffsym(istream, pretree_decode_table,
157 LZX_PRECODE_TABLEBITS, LZX_MAX_PRE_CODEWORD_LEN);
160 /* Reads a Huffman-encoded symbol using the main tree. */
162 read_huffsym_using_maintree(struct input_bitstream *istream,
163 const struct lzx_tables *tables)
165 return read_huffsym(istream, tables->maintree_decode_table,
166 LZX_MAINCODE_TABLEBITS, LZX_MAX_MAIN_CODEWORD_LEN);
169 /* Reads a Huffman-encoded symbol using the length tree. */
171 read_huffsym_using_lentree(struct input_bitstream *istream,
172 const struct lzx_tables *tables)
174 return read_huffsym(istream, tables->lentree_decode_table,
175 LZX_LENCODE_TABLEBITS, LZX_MAX_LEN_CODEWORD_LEN);
178 /* Reads a Huffman-encoded symbol using the aligned offset tree. */
180 read_huffsym_using_alignedtree(struct input_bitstream *istream,
181 const struct lzx_tables *tables)
183 return read_huffsym(istream, tables->alignedtree_decode_table,
184 LZX_ALIGNEDCODE_TABLEBITS, LZX_MAX_ALIGNED_CODEWORD_LEN);
188 * Reads the pretree from the input, then uses the pretree to decode @num_lens
189 * code length values from the input.
191 * @istream: The bit stream for the input. It is positioned on the beginning
192 * of the pretree for the code length values.
193 * @lens: An array that contains the length values from the previous time
194 * the code lengths for this Huffman tree were read, or all
195 * 0's if this is the first time.
196 * @num_lens: Number of length values to decode and return.
200 lzx_read_code_lens(struct input_bitstream *istream, u8 lens[],
203 /* Declare the decoding table and length table for the pretree. */
204 u16 pretree_decode_table[(1 << LZX_PRECODE_TABLEBITS) +
205 (LZX_PRECODE_NUM_SYMBOLS * 2)]
206 _aligned_attribute(DECODE_TABLE_ALIGNMENT);
207 u8 pretree_lens[LZX_PRECODE_NUM_SYMBOLS];
211 /* Read the code lengths of the pretree codes. There are 20 lengths of
213 for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) {
214 pretree_lens[i] = bitstream_read_bits(istream,
215 LZX_PRECODE_ELEMENT_SIZE);
218 /* Make the decoding table for the pretree. */
219 ret = make_huffman_decode_table(pretree_decode_table,
220 LZX_PRECODE_NUM_SYMBOLS,
221 LZX_PRECODE_TABLEBITS,
223 LZX_MAX_PRE_CODEWORD_LEN);
227 /* Pointer past the last length value that needs to be filled in. */
228 u8 *lens_end = lens + num_lens;
232 /* Decode a symbol from the input. If the symbol is between 0
233 * and 16, it is the difference from the old length. If it is
234 * between 17 and 19, it is a special code that indicates that
235 * some number of the next lengths are all 0, or some number of
236 * the next lengths are all equal to the next symbol in the
244 tree_code = read_huffsym_using_pretree(istream,
245 pretree_decode_table);
247 case 17: /* Run of 0's */
248 num_zeroes = bitstream_read_bits(istream, 4);
250 while (num_zeroes--) {
252 if (++lens == lens_end)
256 case 18: /* Longer run of 0's */
257 num_zeroes = bitstream_read_bits(istream, 5);
259 while (num_zeroes--) {
261 if (++lens == lens_end)
265 case 19: /* Run of identical lengths */
266 num_same = bitstream_read_bits(istream, 1);
268 code = read_huffsym_using_pretree(istream,
269 pretree_decode_table);
270 value = (signed char)*lens - (signed char)code;
275 if (++lens == lens_end)
279 default: /* Difference from old length. */
280 value = (signed char)*lens - (signed char)tree_code;
284 if (++lens == lens_end)
292 * Reads the header for an LZX-compressed block.
294 * @istream: The input bitstream.
295 * @block_size_ret: A pointer to an int into which the size of the block,
296 * in bytes, will be returned.
297 * @block_type_ret: A pointer to an int into which the type of the block
298 * (LZX_BLOCKTYPE_*) will be returned.
299 * @tables: A pointer to an lzx_tables structure in which the
300 * main tree, the length tree, and possibly the
301 * aligned offset tree will be constructed.
302 * @queue: A pointer to the least-recently-used queue into which
303 * R0, R1, and R2 will be written (only for uncompressed
304 * blocks, which contain this information in the header)
307 lzx_read_block_header(struct input_bitstream *istream,
308 unsigned num_main_syms,
309 unsigned max_window_size,
310 unsigned *block_size_ret,
311 unsigned *block_type_ret,
312 struct lzx_tables *tables,
313 struct lzx_lru_queue *queue)
319 bitstream_ensure_bits(istream, 4);
321 /* The first three bits tell us what kind of block it is, and are one
322 * of the LZX_BLOCKTYPE_* values. */
323 block_type = bitstream_pop_bits(istream, 3);
325 /* Read the block size. This mirrors the behavior
326 * lzx_write_compressed_block() in lzx-compress.c; see that for more
328 if (bitstream_pop_bits(istream, 1)) {
329 block_size = LZX_DEFAULT_BLOCK_SIZE;
334 tmp = bitstream_read_bits(istream, 8);
336 tmp = bitstream_read_bits(istream, 8);
340 if (max_window_size >= 65536) {
341 tmp = bitstream_read_bits(istream, 8);
347 switch (block_type) {
348 case LZX_BLOCKTYPE_ALIGNED:
349 /* Read the path lengths for the elements of the aligned tree,
352 for (unsigned i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
353 tables->alignedtree_lens[i] =
354 bitstream_read_bits(istream,
355 LZX_ALIGNEDCODE_ELEMENT_SIZE);
358 LZX_DEBUG("Building the aligned tree.");
359 ret = make_huffman_decode_table(tables->alignedtree_decode_table,
360 LZX_ALIGNEDCODE_NUM_SYMBOLS,
361 LZX_ALIGNEDCODE_TABLEBITS,
362 tables->alignedtree_lens,
363 LZX_MAX_ALIGNED_CODEWORD_LEN);
365 LZX_DEBUG("Failed to make the decode table for the "
366 "aligned offset tree");
370 /* Fall though, since the rest of the header for aligned offset
371 * blocks is the same as that for verbatim blocks */
373 case LZX_BLOCKTYPE_VERBATIM:
374 if (block_type == LZX_BLOCKTYPE_VERBATIM)
375 LZX_DEBUG("Found verbatim block.");
377 LZX_DEBUG("Reading path lengths for main tree.");
378 /* Read the path lengths for the first 256 elements of the main
380 ret = lzx_read_code_lens(istream, tables->maintree_lens,
383 LZX_DEBUG("Failed to read the code lengths for the "
384 "first 256 elements of the main tree");
388 /* Read the path lengths for the remaining elements of the main
390 LZX_DEBUG("Reading path lengths for remaining elements of "
391 "main tree (%d elements).",
392 num_main_syms - LZX_NUM_CHARS);
393 ret = lzx_read_code_lens(istream,
394 tables->maintree_lens + LZX_NUM_CHARS,
395 num_main_syms - LZX_NUM_CHARS);
397 LZX_DEBUG("Failed to read the path lengths for the "
398 "remaining elements of the main tree");
402 LZX_DEBUG("Building the Huffman decoding "
403 "table for the main tree.");
405 ret = make_huffman_decode_table(tables->maintree_decode_table,
407 LZX_MAINCODE_TABLEBITS,
408 tables->maintree_lens,
409 LZX_MAX_MAIN_CODEWORD_LEN);
411 LZX_DEBUG("Failed to make the decode "
412 "table for the main tree");
416 LZX_DEBUG("Reading path lengths for the length tree.");
417 ret = lzx_read_code_lens(istream, tables->lentree_lens,
418 LZX_LENCODE_NUM_SYMBOLS);
420 LZX_DEBUG("Failed to read the path "
421 "lengths for the length tree");
425 LZX_DEBUG("Building the length tree.");
426 ret = make_huffman_decode_table(tables->lentree_decode_table,
427 LZX_LENCODE_NUM_SYMBOLS,
428 LZX_LENCODE_TABLEBITS,
429 tables->lentree_lens,
430 LZX_MAX_LEN_CODEWORD_LEN);
432 LZX_DEBUG("Failed to build the length Huffman tree");
435 /* The bitstream of compressed literals and matches for this
436 * block directly follows and will be read in
437 * lzx_decompress_block(). */
439 case LZX_BLOCKTYPE_UNCOMPRESSED:
440 LZX_DEBUG("Found uncompressed block.");
441 /* Before reading the three LRU match offsets from the
442 * uncompressed block header, the stream needs to be aligned on
443 * a 16-bit boundary. But, unexpectedly, if the stream is
444 * *already* aligned, the correct thing to do is to throw away
445 * the next 16 bits. */
446 if (istream->bitsleft == 0) {
447 if (istream->data_bytes_left < 14) {
448 LZX_DEBUG("Insufficient length in "
449 "uncompressed block");
453 istream->data_bytes_left -= 2;
455 if (istream->data_bytes_left < 12) {
456 LZX_DEBUG("Insufficient length in "
457 "uncompressed block");
460 istream->bitsleft = 0;
463 queue->R[0] = le32_to_cpu(*(le32*)(istream->data + 0));
464 queue->R[1] = le32_to_cpu(*(le32*)(istream->data + 4));
465 queue->R[2] = le32_to_cpu(*(le32*)(istream->data + 8));
467 istream->data_bytes_left -= 12;
468 /* The uncompressed data of this block directly follows and will
469 * be read in lzx_decompress(). */
472 LZX_DEBUG("Found invalid block");
475 *block_type_ret = block_type;
476 *block_size_ret = block_size;
481 * Decodes a compressed match from a block of LZX-compressed data. A match
482 * refers to some match_offset to a point earlier in the window as well as some
483 * match_len, for which the data is to be copied to the current position in the
486 * @main_element: The start of the match data, as decoded using the main
489 * @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or
490 * LZX_BLOCKTYPE_VERBATIM)
492 * @bytes_remaining: The amount of uncompressed data remaining to be
493 * uncompressed in this block. It is an error if the match
494 * is longer than this number.
496 * @window: A pointer to the window into which the uncompressed
497 * data is being written.
499 * @window_pos: The current byte offset in the window.
501 * @tables: The Huffman decoding tables for this LZX block (main
502 * code, length code, and for LZX_BLOCKTYPE_ALIGNED blocks,
503 * also the aligned offset code).
505 * @queue: The least-recently used queue for match offsets.
507 * @istream: The input bitstream.
509 * Returns the length of the match, or a negative number on error. The possible
511 * - Match would exceed the amount of data remaining to be uncompressed.
512 * - Match refers to data before the window.
513 * - The input bitstream ended unexpectedly.
516 lzx_decode_match(unsigned main_element, int block_type,
517 unsigned bytes_remaining, u8 *window,
519 const struct lzx_tables *tables,
520 struct lzx_lru_queue *queue,
521 struct input_bitstream *istream)
523 unsigned length_header;
524 unsigned position_slot;
526 unsigned match_offset;
527 unsigned num_extra_bits;
534 /* The main element is offset by 256 because values under 256 indicate a
536 main_element -= LZX_NUM_CHARS;
538 /* The length header consists of the lower 3 bits of the main element.
539 * The position slot is the rest of it. */
540 length_header = main_element & LZX_NUM_PRIMARY_LENS;
541 position_slot = main_element >> 3;
543 /* If the length_header is less than LZX_NUM_PRIMARY_LENS (= 7), it
544 * gives the match length as the offset from LZX_MIN_MATCH_LEN.
545 * Otherwise, the length is given by an additional symbol encoded using
546 * the length tree, offset by 9 (LZX_MIN_MATCH_LEN +
547 * LZX_NUM_PRIMARY_LENS) */
548 match_len = LZX_MIN_MATCH_LEN + length_header;
549 if (length_header == LZX_NUM_PRIMARY_LENS)
550 match_len += read_huffsym_using_lentree(istream, tables);
552 /* If the position_slot is 0, 1, or 2, the match offset is retrieved
553 * from the LRU queue. Otherwise, the match offset is not in the LRU
555 if (position_slot <= 2) {
556 /* Note: This isn't a real LRU queue, since using the R2 offset
557 * doesn't bump the R1 offset down to R2. This quirk allows all
558 * 3 recent offsets to be handled by the same code. (For R0,
559 * the swap is a no-op.) */
560 match_offset = queue->R[position_slot];
561 queue->R[position_slot] = queue->R[0];
562 queue->R[0] = match_offset;
564 /* Otherwise, the offset was not encoded as one the offsets in
565 * the queue. Depending on the position slot, there is a
566 * certain number of extra bits that need to be read to fully
567 * decode the match offset. */
569 /* Look up the number of extra bits that need to be read. */
570 num_extra_bits = lzx_get_num_extra_bits(position_slot);
572 /* For aligned blocks, if there are at least 3 extra bits, the
573 * actual number of extra bits is 3 less, and they encode a
574 * number of 8-byte words that are added to the offset; there
575 * is then an additional symbol read using the aligned tree that
576 * specifies the actual byte alignment. */
577 if (block_type == LZX_BLOCKTYPE_ALIGNED && num_extra_bits >= 3) {
579 /* There is an error in the LZX "specification" at this
580 * point; it indicates that a Huffman symbol is to be
581 * read only if num_extra_bits is greater than 3, but
582 * actually it is if num_extra_bits is greater than or
583 * equal to 3. (Note that in the case with
584 * num_extra_bits == 3, the assignment to verbatim_bits
585 * will just set it to 0. ) */
586 verbatim_bits = bitstream_read_bits(istream,
589 aligned_bits = read_huffsym_using_alignedtree(istream,
592 /* For non-aligned blocks, or for aligned blocks with
593 * less than 3 extra bits, the extra bits are added
594 * directly to the match offset, and the correction for
595 * the alignment is taken to be 0. */
596 verbatim_bits = bitstream_read_bits(istream, num_extra_bits);
600 /* Calculate the match offset. */
601 match_offset = lzx_position_base[position_slot] +
602 verbatim_bits + aligned_bits - LZX_OFFSET_OFFSET;
604 /* Update the LRU queue. */
605 queue->R[2] = queue->R[1];
606 queue->R[1] = queue->R[0];
607 queue->R[0] = match_offset;
610 /* Verify that the match is in the bounds of the part of the window
611 * currently in use, then copy the source of the match to the current
614 if (unlikely(match_len > bytes_remaining)) {
615 LZX_DEBUG("Match of length %u bytes overflows "
616 "uncompressed block size", match_len);
620 if (unlikely(match_offset > window_pos)) {
621 LZX_DEBUG("Match of length %u bytes references "
622 "data before window (match_offset = %u, "
624 match_len, match_offset, window_pos);
628 match_dest = window + window_pos;
629 match_src = match_dest - match_offset;
632 printf("Match: src %u, dst %u, len %u\n", match_src - window,
636 for (i = 0; i < match_len; i++) {
637 match_dest[i] = match_src[i];
638 putchar(match_src[i]);
643 for (i = 0; i < match_len; i++)
644 match_dest[i] = match_src[i];
651 undo_call_insn_translation(u32 *call_insn_target, s32 input_pos)
656 abs_offset = le32_to_cpu(*call_insn_target);
657 if (abs_offset >= 0) {
658 if (abs_offset < LZX_WIM_MAGIC_FILESIZE) {
659 /* "good translation" */
660 rel_offset = abs_offset - input_pos;
662 *call_insn_target = cpu_to_le32(rel_offset);
665 if (abs_offset >= -input_pos) {
666 /* "compensating translation" */
667 rel_offset = abs_offset + LZX_WIM_MAGIC_FILESIZE;
669 *call_insn_target = cpu_to_le32(rel_offset);
674 /* Undo the 'E8' preprocessing, where the targets of x86 CALL instructions were
675 * changed from relative offsets to absolute offsets.
677 * Note that this call instruction preprocessing can and will be used on any
678 * data even if it is not actually x86 machine code. In fact, this type of
679 * preprocessing appears to always be used in LZX-compressed resources in WIM
680 * files; there is no bit to indicate whether it is used or not, unlike in the
681 * LZX compressed format as used in cabinet files, where a bit is reserved for
684 * Call instruction preprocessing is disabled in the last 6 bytes of the
685 * uncompressed data, which really means the 5-byte call instruction cannot
686 * start in the last 10 bytes of the uncompressed data. This is one of the
687 * errors in the LZX documentation.
689 * Call instruction preprocessing does not appear to be disabled after the
690 * 32768th chunk of a WIM stream, which is apparently is yet another difference
691 * from the LZX compression used in cabinet files.
693 * Call instruction processing is supposed to take the file size as a parameter,
694 * as it is used in calculating the translated jump targets. But in WIM files,
695 * this file size is always the same (LZX_WIM_MAGIC_FILESIZE == 12000000).*/
697 undo_call_insn_preprocessing(u8 *uncompressed_data, size_t uncompressed_size)
701 /* SSE2 vectorized implementation for x86_64. This speeds up LZX
702 * decompression by about 5-8% overall. (Usually --- the performance
703 * actually regresses slightly in the degenerate case that the data
704 * consists entirely of 0xe8 bytes.) */
705 __m128i *p128 = (__m128i *)uncompressed_data;
706 u32 valid_mask = 0xFFFFFFFF;
708 if (uncompressed_size >= 32 &&
709 ((uintptr_t)uncompressed_data % 16 == 0))
711 __m128i * const end128 = p128 + uncompressed_size / 16 - 1;
713 /* Create a vector of all 0xe8 bytes */
714 const __m128i e8_bytes = _mm_set1_epi8(0xe8);
716 /* Iterate through the 16-byte vectors in the input. */
718 /* Compare the current 16-byte vector with the vector of
719 * all 0xe8 bytes. This produces 0xff where the byte is
720 * 0xe8 and 0x00 where it is not. */
721 __m128i cmpresult = _mm_cmpeq_epi8(*p128, e8_bytes);
723 /* Map the comparison results into a single 16-bit
724 * number. It will contain a 1 bit when the
725 * corresponding byte in the current 16-byte vector is
726 * an e8 byte. Note: the low-order bit corresponds to
727 * the first (lowest address) byte. */
728 u32 e8_mask = _mm_movemask_epi8(cmpresult);
731 /* If e8_mask is 0, then none of these 16 bytes
732 * have value 0xe8. No e8 translation is
733 * needed, and there is no restriction that
734 * carries over to the next 16 bytes. */
735 valid_mask = 0xFFFFFFFF;
737 /* At least one byte has value 0xe8.
739 * The AND with valid_mask accounts for the fact
740 * that we can't start an e8 translation that
741 * overlaps the previous one. */
742 while ((e8_mask &= valid_mask)) {
744 /* Count the number of trailing zeroes
745 * in e8_mask. This will produce the
746 * index of the byte, within the 16, at
747 * which the next e8 translation should
749 u32 bit = __builtin_ctz(e8_mask);
751 /* Do the e8 translation. */
752 u8 *p8 = (u8 *)p128 + bit;
753 undo_call_insn_translation((s32 *)(p8 + 1),
754 p8 - uncompressed_data);
756 /* Don't start an e8 translation in the
758 valid_mask &= ~((u32)0x1F << bit);
760 /* Moving on to the next vector. Shift and set
761 * valid_mask accordingly. */
763 valid_mask |= 0xFFFF0000;
765 } while (++p128 < end128);
769 while (!(valid_mask & 1)) {
774 u8 *p8 = uncompressed_data;
775 #endif /* !__SSE2__ */
777 if (uncompressed_size > 10) {
778 /* Finish any bytes that weren't processed by the vectorized
780 u8 *p8_end = uncompressed_data + uncompressed_size - 10;
783 undo_call_insn_translation((s32 *)(p8 + 1),
784 p8 - uncompressed_data);
789 } while (p8 < p8_end);
794 * Decompresses an LZX-compressed block of data from which the header has already
797 * @block_type: The type of the block (LZX_BLOCKTYPE_VERBATIM or
798 * LZX_BLOCKTYPE_ALIGNED)
799 * @block_size: The size of the block, in bytes.
800 * @window: Pointer to the decompression window.
801 * @window_pos: The current position in the window. Will be 0 for the first
803 * @tables: The Huffman decoding tables for the block (main, length, and
804 * aligned offset, the latter only for LZX_BLOCKTYPE_ALIGNED)
805 * @queue: The least-recently-used queue for match offsets.
806 * @istream: The input bitstream for the compressed literals.
809 lzx_decompress_block(int block_type, unsigned block_size,
812 const struct lzx_tables *tables,
813 struct lzx_lru_queue *queue,
814 struct input_bitstream *istream)
816 unsigned main_element;
820 end = window_pos + block_size;
821 while (window_pos < end) {
822 main_element = read_huffsym_using_maintree(istream, tables);
823 if (main_element < LZX_NUM_CHARS) {
824 /* literal: 0 to LZX_NUM_CHARS - 1 */
825 window[window_pos++] = main_element;
827 /* match: LZX_NUM_CHARS to num_main_syms - 1 */
828 match_len = lzx_decode_match(main_element,
836 if (unlikely(match_len < 0))
838 window_pos += match_len;
845 lzx_decompress(const void *compressed_data, size_t compressed_size,
846 void *uncompressed_data, size_t uncompressed_size,
849 struct lzx_decompressor *ctx = _ctx;
850 struct input_bitstream istream;
851 struct lzx_lru_queue queue;
856 bool e8_preprocessing_done;
858 LZX_DEBUG("compressed_data = %p, compressed_size = %zu, "
859 "uncompressed_data = %p, uncompressed_size = %zu, "
860 "max_window_size=%u).",
861 compressed_data, compressed_size,
862 uncompressed_data, uncompressed_size,
863 ctx->max_window_size);
865 if (uncompressed_size > ctx->max_window_size) {
866 LZX_DEBUG("Uncompressed size of %zu exceeds "
867 "window size of %u!",
868 uncompressed_size, ctx->max_window_size);
872 memset(ctx->tables.maintree_lens, 0, sizeof(ctx->tables.maintree_lens));
873 memset(ctx->tables.lentree_lens, 0, sizeof(ctx->tables.lentree_lens));
874 lzx_lru_queue_init(&queue);
875 init_input_bitstream(&istream, compressed_data, compressed_size);
877 e8_preprocessing_done = false; /* Set to true if there may be 0xe8 bytes
878 in the uncompressed data. */
880 /* The compressed data will consist of one or more blocks. The
881 * following loop decompresses one block, and it runs until there all
882 * the compressed data has been decompressed, so there are no more
886 window_pos < uncompressed_size;
887 window_pos += block_size)
889 LZX_DEBUG("Reading block header.");
890 ret = lzx_read_block_header(&istream, ctx->num_main_syms,
891 ctx->max_window_size, &block_size,
892 &block_type, &ctx->tables, &queue);
896 LZX_DEBUG("block_size = %u, window_pos = %u",
897 block_size, window_pos);
899 if (block_size > uncompressed_size - window_pos) {
900 LZX_DEBUG("Expected a block size of at "
901 "most %zu bytes (found %u bytes)",
902 uncompressed_size - window_pos, block_size);
906 switch (block_type) {
907 case LZX_BLOCKTYPE_VERBATIM:
908 case LZX_BLOCKTYPE_ALIGNED:
909 if (block_type == LZX_BLOCKTYPE_VERBATIM)
910 LZX_DEBUG("LZX_BLOCKTYPE_VERBATIM");
912 LZX_DEBUG("LZX_BLOCKTYPE_ALIGNED");
913 ret = lzx_decompress_block(block_type,
923 if (ctx->tables.maintree_lens[0xe8] != 0)
924 e8_preprocessing_done = true;
926 case LZX_BLOCKTYPE_UNCOMPRESSED:
927 LZX_DEBUG("LZX_BLOCKTYPE_UNCOMPRESSED");
928 if (istream.data_bytes_left < block_size) {
929 LZX_DEBUG("Unexpected end of input when "
930 "reading %u bytes from LZX bitstream "
931 "(only have %u bytes left)",
932 block_size, istream.data_bytes_left);
935 memcpy(&((u8*)uncompressed_data)[window_pos], istream.data,
937 istream.data += block_size;
938 istream.data_bytes_left -= block_size;
939 /* Re-align bitstream if an odd number of bytes were
941 if (istream.data_bytes_left && (block_size & 1)) {
942 istream.data_bytes_left--;
945 e8_preprocessing_done = true;
949 if (e8_preprocessing_done)
950 undo_call_insn_preprocessing(uncompressed_data, uncompressed_size);
955 lzx_free_decompressor(void *_ctx)
957 struct lzx_decompressor *ctx = _ctx;
963 lzx_create_decompressor(size_t max_window_size,
964 const struct wimlib_decompressor_params_header *params,
967 struct lzx_decompressor *ctx;
969 if (!lzx_window_size_valid(max_window_size))
970 return WIMLIB_ERR_INVALID_PARAM;
972 ctx = MALLOC(sizeof(struct lzx_decompressor));
974 return WIMLIB_ERR_NOMEM;
976 ctx->max_window_size = max_window_size;
977 ctx->num_main_syms = lzx_get_num_main_syms(max_window_size);
983 const struct decompressor_ops lzx_decompressor_ops = {
984 .create_decompressor = lzx_create_decompressor,
985 .decompress = lzx_decompress,
986 .free_decompressor = lzx_free_decompressor,