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[],
155 const u8 pretree_lens[], unsigned *n)
157 return read_huffsym(istream, pretree_decode_table, pretree_lens,
158 LZX_PRECODE_NUM_SYMBOLS, LZX_PRECODE_TABLEBITS, n,
159 LZX_MAX_PRE_CODEWORD_LEN);
162 /* Reads a Huffman-encoded symbol using the main tree. */
164 read_huffsym_using_maintree(struct input_bitstream *istream,
165 const struct lzx_tables *tables,
167 unsigned num_main_syms)
169 return read_huffsym(istream, tables->maintree_decode_table,
170 tables->maintree_lens, num_main_syms,
171 LZX_MAINCODE_TABLEBITS, n, LZX_MAX_MAIN_CODEWORD_LEN);
174 /* Reads a Huffman-encoded symbol using the length tree. */
176 read_huffsym_using_lentree(struct input_bitstream *istream,
177 const struct lzx_tables *tables,
180 return read_huffsym(istream, tables->lentree_decode_table,
181 tables->lentree_lens, LZX_LENCODE_NUM_SYMBOLS,
182 LZX_LENCODE_TABLEBITS, n, LZX_MAX_LEN_CODEWORD_LEN);
185 /* Reads a Huffman-encoded symbol using the aligned offset tree. */
187 read_huffsym_using_alignedtree(struct input_bitstream *istream,
188 const struct lzx_tables *tables,
191 return read_huffsym(istream, tables->alignedtree_decode_table,
192 tables->alignedtree_lens,
193 LZX_ALIGNEDCODE_NUM_SYMBOLS,
194 LZX_ALIGNEDCODE_TABLEBITS, n,
195 LZX_MAX_ALIGNED_CODEWORD_LEN);
199 * Reads the pretree from the input, then uses the pretree to decode @num_lens
200 * code length values from the input.
202 * @istream: The bit stream for the input. It is positioned on the beginning
203 * of the pretree for the code length values.
204 * @lens: An array that contains the length values from the previous time
205 * the code lengths for this Huffman tree were read, or all
206 * 0's if this is the first time.
207 * @num_lens: Number of length values to decode and return.
211 lzx_read_code_lens(struct input_bitstream *istream, u8 lens[],
214 /* Declare the decoding table and length table for the pretree. */
215 u16 pretree_decode_table[(1 << LZX_PRECODE_TABLEBITS) +
216 (LZX_PRECODE_NUM_SYMBOLS * 2)]
217 _aligned_attribute(DECODE_TABLE_ALIGNMENT);
218 u8 pretree_lens[LZX_PRECODE_NUM_SYMBOLS];
223 /* Read the code lengths of the pretree codes. There are 20 lengths of
225 for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) {
226 ret = bitstream_read_bits(istream, LZX_PRECODE_ELEMENT_SIZE,
230 pretree_lens[i] = len;
233 /* Make the decoding table for the pretree. */
234 ret = make_huffman_decode_table(pretree_decode_table,
235 LZX_PRECODE_NUM_SYMBOLS,
236 LZX_PRECODE_TABLEBITS,
238 LZX_MAX_PRE_CODEWORD_LEN);
242 /* Pointer past the last length value that needs to be filled in. */
243 u8 *lens_end = lens + num_lens;
247 /* Decode a symbol from the input. If the symbol is between 0
248 * and 16, it is the difference from the old length. If it is
249 * between 17 and 19, it is a special code that indicates that
250 * some number of the next lengths are all 0, or some number of
251 * the next lengths are all equal to the next symbol in the
259 ret = read_huffsym_using_pretree(istream, pretree_decode_table,
260 pretree_lens, &tree_code);
264 case 17: /* Run of 0's */
265 ret = bitstream_read_bits(istream, 4, &num_zeroes);
269 while (num_zeroes--) {
271 if (++lens == lens_end)
275 case 18: /* Longer run of 0's */
276 ret = bitstream_read_bits(istream, 5, &num_zeroes);
280 while (num_zeroes--) {
282 if (++lens == lens_end)
286 case 19: /* Run of identical lengths */
287 ret = bitstream_read_bits(istream, 1, &num_same);
291 ret = read_huffsym_using_pretree(istream,
292 pretree_decode_table,
297 value = (signed char)*lens - (signed char)code;
302 if (++lens == lens_end)
306 default: /* Difference from old length. */
307 value = (signed char)*lens - (signed char)tree_code;
311 if (++lens == lens_end)
319 * Reads the header for an LZX-compressed block.
321 * @istream: The input bitstream.
322 * @block_size_ret: A pointer to an int into which the size of the block,
323 * in bytes, will be returned.
324 * @block_type_ret: A pointer to an int into which the type of the block
325 * (LZX_BLOCKTYPE_*) will be returned.
326 * @tables: A pointer to an lzx_tables structure in which the
327 * main tree, the length tree, and possibly the
328 * aligned offset tree will be constructed.
329 * @queue: A pointer to the least-recently-used queue into which
330 * R0, R1, and R2 will be written (only for uncompressed
331 * blocks, which contain this information in the header)
334 lzx_read_block_header(struct input_bitstream *istream,
335 unsigned num_main_syms,
336 unsigned max_window_size,
337 unsigned *block_size_ret,
338 unsigned *block_type_ret,
339 struct lzx_tables *tables,
340 struct lzx_lru_queue *queue)
346 ret = bitstream_ensure_bits(istream, 4);
350 /* The first three bits tell us what kind of block it is, and are one
351 * of the LZX_BLOCKTYPE_* values. */
352 block_type = bitstream_read_bits_nocheck(istream, 3);
354 /* Read the block size. This mirrors the behavior
355 * lzx_write_compressed_block() in lzx-compress.c; see that for more
357 if (bitstream_read_bits_nocheck(istream, 1)) {
358 block_size = LZX_DEFAULT_BLOCK_SIZE;
363 ret = bitstream_read_bits(istream, 8, &tmp);
368 ret = bitstream_read_bits(istream, 8, &tmp);
374 if (max_window_size >= 65536) {
375 ret = bitstream_read_bits(istream, 8, &tmp);
383 switch (block_type) {
384 case LZX_BLOCKTYPE_ALIGNED:
385 /* Read the path lengths for the elements of the aligned tree,
388 for (unsigned i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
391 ret = bitstream_read_bits(istream,
392 LZX_ALIGNEDCODE_ELEMENT_SIZE,
396 tables->alignedtree_lens[i] = len;
399 LZX_DEBUG("Building the aligned tree.");
400 ret = make_huffman_decode_table(tables->alignedtree_decode_table,
401 LZX_ALIGNEDCODE_NUM_SYMBOLS,
402 LZX_ALIGNEDCODE_TABLEBITS,
403 tables->alignedtree_lens,
404 LZX_MAX_ALIGNED_CODEWORD_LEN);
406 LZX_DEBUG("Failed to make the decode table for the "
407 "aligned offset tree");
411 /* Fall though, since the rest of the header for aligned offset
412 * blocks is the same as that for verbatim blocks */
414 case LZX_BLOCKTYPE_VERBATIM:
415 if (block_type == LZX_BLOCKTYPE_VERBATIM)
416 LZX_DEBUG("Found verbatim block.");
418 LZX_DEBUG("Reading path lengths for main tree.");
419 /* Read the path lengths for the first 256 elements of the main
421 ret = lzx_read_code_lens(istream, tables->maintree_lens,
424 LZX_DEBUG("Failed to read the code lengths for the "
425 "first 256 elements of the main tree");
429 /* Read the path lengths for the remaining elements of the main
431 LZX_DEBUG("Reading path lengths for remaining elements of "
432 "main tree (%d elements).",
433 num_main_syms - LZX_NUM_CHARS);
434 ret = lzx_read_code_lens(istream,
435 tables->maintree_lens + LZX_NUM_CHARS,
436 num_main_syms - LZX_NUM_CHARS);
438 LZX_DEBUG("Failed to read the path lengths for the "
439 "remaining elements of the main tree");
443 LZX_DEBUG("Building the Huffman decoding "
444 "table for the main tree.");
446 ret = make_huffman_decode_table(tables->maintree_decode_table,
448 LZX_MAINCODE_TABLEBITS,
449 tables->maintree_lens,
450 LZX_MAX_MAIN_CODEWORD_LEN);
452 LZX_DEBUG("Failed to make the decode "
453 "table for the main tree");
457 LZX_DEBUG("Reading path lengths for the length tree.");
458 ret = lzx_read_code_lens(istream, tables->lentree_lens,
459 LZX_LENCODE_NUM_SYMBOLS);
461 LZX_DEBUG("Failed to read the path "
462 "lengths for the length tree");
466 LZX_DEBUG("Building the length tree.");
467 ret = make_huffman_decode_table(tables->lentree_decode_table,
468 LZX_LENCODE_NUM_SYMBOLS,
469 LZX_LENCODE_TABLEBITS,
470 tables->lentree_lens,
471 LZX_MAX_LEN_CODEWORD_LEN);
473 LZX_DEBUG("Failed to build the length Huffman tree");
476 /* The bitstream of compressed literals and matches for this
477 * block directly follows and will be read in
478 * lzx_decompress_block(). */
480 case LZX_BLOCKTYPE_UNCOMPRESSED:
481 LZX_DEBUG("Found uncompressed block.");
482 /* Before reading the three LRU match offsets from the
483 * uncompressed block header, the stream needs to be aligned on
484 * a 16-bit boundary. But, unexpectedly, if the stream is
485 * *already* aligned, the correct thing to do is to throw away
486 * the next 16 bits. */
487 if (istream->bitsleft == 0) {
488 if (istream->data_bytes_left < 14) {
489 LZX_DEBUG("Insufficient length in "
490 "uncompressed block");
494 istream->data_bytes_left -= 2;
496 if (istream->data_bytes_left < 12) {
497 LZX_DEBUG("Insufficient length in "
498 "uncompressed block");
501 istream->bitsleft = 0;
504 queue->R[0] = le32_to_cpu(*(le32*)(istream->data + 0));
505 queue->R[1] = le32_to_cpu(*(le32*)(istream->data + 4));
506 queue->R[2] = le32_to_cpu(*(le32*)(istream->data + 8));
508 istream->data_bytes_left -= 12;
509 /* The uncompressed data of this block directly follows and will
510 * be read in lzx_decompress(). */
513 LZX_DEBUG("Found invalid block");
516 *block_type_ret = block_type;
517 *block_size_ret = block_size;
522 * Decodes a compressed match from a block of LZX-compressed data. A match
523 * refers to some match_offset to a point earlier in the window as well as some
524 * match_len, for which the data is to be copied to the current position in the
527 * @main_element: The start of the match data, as decoded using the main
530 * @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or
531 * LZX_BLOCKTYPE_VERBATIM)
533 * @bytes_remaining: The amount of uncompressed data remaining to be
534 * uncompressed in this block. It is an error if the match
535 * is longer than this number.
537 * @window: A pointer to the window into which the uncompressed
538 * data is being written.
540 * @window_pos: The current byte offset in the window.
542 * @tables: The Huffman decoding tables for this LZX block (main
543 * code, length code, and for LZX_BLOCKTYPE_ALIGNED blocks,
544 * also the aligned offset code).
546 * @queue: The least-recently used queue for match offsets.
548 * @istream: The input bitstream.
550 * Returns the length of the match, or a negative number on error. The possible
552 * - Match would exceed the amount of data remaining to be uncompressed.
553 * - Match refers to data before the window.
554 * - The input bitstream ended unexpectedly.
557 lzx_decode_match(unsigned main_element, int block_type,
558 unsigned bytes_remaining, u8 *window,
560 const struct lzx_tables *tables,
561 struct lzx_lru_queue *queue,
562 struct input_bitstream *istream)
564 unsigned length_header;
565 unsigned position_slot;
567 unsigned match_offset;
568 unsigned additional_len;
569 unsigned num_extra_bits;
577 /* The main element is offset by 256 because values under 256 indicate a
579 main_element -= LZX_NUM_CHARS;
581 /* The length header consists of the lower 3 bits of the main element.
582 * The position slot is the rest of it. */
583 length_header = main_element & LZX_NUM_PRIMARY_LENS;
584 position_slot = main_element >> 3;
586 /* If the length_header is less than LZX_NUM_PRIMARY_LENS (= 7), it
587 * gives the match length as the offset from LZX_MIN_MATCH_LEN.
588 * Otherwise, the length is given by an additional symbol encoded using
589 * the length tree, offset by 9 (LZX_MIN_MATCH_LEN +
590 * LZX_NUM_PRIMARY_LENS) */
591 match_len = LZX_MIN_MATCH_LEN + length_header;
592 if (length_header == LZX_NUM_PRIMARY_LENS) {
593 ret = read_huffsym_using_lentree(istream, tables,
597 match_len += additional_len;
601 /* If the position_slot is 0, 1, or 2, the match offset is retrieved
602 * from the LRU queue. Otherwise, the match offset is not in the LRU
604 switch (position_slot) {
606 match_offset = queue->R[0];
609 match_offset = queue->R[1];
610 swap(queue->R[0], queue->R[1]);
613 /* The queue doesn't work quite the same as a real LRU queue,
614 * since using the R2 offset doesn't bump the R1 offset down to
616 match_offset = queue->R[2];
617 swap(queue->R[0], queue->R[2]);
620 /* Otherwise, the offset was not encoded as one the offsets in
621 * the queue. Depending on the position slot, there is a
622 * certain number of extra bits that need to be read to fully
623 * decode the match offset. */
625 /* Look up the number of extra bits that need to be read. */
626 num_extra_bits = lzx_get_num_extra_bits(position_slot);
628 /* For aligned blocks, if there are at least 3 extra bits, the
629 * actual number of extra bits is 3 less, and they encode a
630 * number of 8-byte words that are added to the offset; there
631 * is then an additional symbol read using the aligned tree that
632 * specifies the actual byte alignment. */
633 if (block_type == LZX_BLOCKTYPE_ALIGNED && num_extra_bits >= 3) {
635 /* There is an error in the LZX "specification" at this
636 * point; it indicates that a Huffman symbol is to be
637 * read only if num_extra_bits is greater than 3, but
638 * actually it is if num_extra_bits is greater than or
639 * equal to 3. (Note that in the case with
640 * num_extra_bits == 3, the assignment to verbatim_bits
641 * will just set it to 0. ) */
642 ret = bitstream_read_bits(istream, num_extra_bits - 3,
649 ret = read_huffsym_using_alignedtree(istream, tables,
654 /* For non-aligned blocks, or for aligned blocks with
655 * less than 3 extra bits, the extra bits are added
656 * directly to the match offset, and the correction for
657 * the alignment is taken to be 0. */
658 ret = bitstream_read_bits(istream, num_extra_bits,
666 /* Calculate the match offset. */
667 match_offset = lzx_position_base[position_slot] +
668 verbatim_bits + aligned_bits - LZX_OFFSET_OFFSET;
670 /* Update the LRU queue. */
671 queue->R[2] = queue->R[1];
672 queue->R[1] = queue->R[0];
673 queue->R[0] = match_offset;
677 /* Verify that the match is in the bounds of the part of the window
678 * currently in use, then copy the source of the match to the current
681 if (match_len > bytes_remaining) {
682 LZX_DEBUG("Match of length %u bytes overflows "
683 "uncompressed block size", match_len);
687 if (match_offset > window_pos) {
688 LZX_DEBUG("Match of length %u bytes references "
689 "data before window (match_offset = %u, "
691 match_len, match_offset, window_pos);
695 match_dest = window + window_pos;
696 match_src = match_dest - match_offset;
699 printf("Match: src %u, dst %u, len %u\n", match_src - window,
703 for (i = 0; i < match_len; i++) {
704 match_dest[i] = match_src[i];
705 putchar(match_src[i]);
710 for (i = 0; i < match_len; i++)
711 match_dest[i] = match_src[i];
718 undo_call_insn_translation(u32 *call_insn_target, s32 input_pos)
723 abs_offset = le32_to_cpu(*call_insn_target);
724 if (abs_offset >= -input_pos && abs_offset < LZX_WIM_MAGIC_FILESIZE) {
725 if (abs_offset >= 0) {
726 /* "good translation" */
727 rel_offset = abs_offset - input_pos;
729 /* "compensating translation" */
730 rel_offset = abs_offset + LZX_WIM_MAGIC_FILESIZE;
732 *call_insn_target = cpu_to_le32(rel_offset);
736 /* Undo the 'E8' preprocessing, where the targets of x86 CALL instructions were
737 * changed from relative offsets to absolute offsets.
739 * Note that this call instruction preprocessing can and will be used on any
740 * data even if it is not actually x86 machine code. In fact, this type of
741 * preprocessing appears to always be used in LZX-compressed resources in WIM
742 * files; there is no bit to indicate whether it is used or not, unlike in the
743 * LZX compressed format as used in cabinet files, where a bit is reserved for
746 * Call instruction preprocessing is disabled in the last 6 bytes of the
747 * uncompressed data, which really means the 5-byte call instruction cannot
748 * start in the last 10 bytes of the uncompressed data. This is one of the
749 * errors in the LZX documentation.
751 * Call instruction preprocessing does not appear to be disabled after the
752 * 32768th chunk of a WIM stream, which is apparently is yet another difference
753 * from the LZX compression used in cabinet files.
755 * Call instruction processing is supposed to take the file size as a parameter,
756 * as it is used in calculating the translated jump targets. But in WIM files,
757 * this file size is always the same (LZX_WIM_MAGIC_FILESIZE == 12000000).*/
759 undo_call_insn_preprocessing(u8 *uncompressed_data, size_t uncompressed_size)
763 /* SSE2 vectorized implementation for x86_64. This speeds up LZX
764 * decompression by about 5-8% overall. (Usually --- the performance
765 * actually regresses slightly in the degenerate case that the data
766 * consists entirely of 0xe8 bytes.) */
767 __m128i *p128 = (__m128i *)uncompressed_data;
768 u32 valid_mask = 0xFFFFFFFF;
770 if (uncompressed_size >= 32 &&
771 ((uintptr_t)uncompressed_data % 16 == 0))
773 __m128i * const end128 = p128 + uncompressed_size / 16 - 1;
775 /* Create a vector of all 0xe8 bytes */
776 const __m128i e8_bytes = _mm_set1_epi8(0xe8);
778 /* Iterate through the 16-byte vectors in the input. */
780 /* Compare the current 16-byte vector with the vector of
781 * all 0xe8 bytes. This produces 0xff where the byte is
782 * 0xe8 and 0x00 where it is not. */
783 __m128i cmpresult = _mm_cmpeq_epi8(*p128, e8_bytes);
785 /* Map the comparison results into a single 16-bit
786 * number. It will contain a 1 bit when the
787 * corresponding byte in the current 16-byte vector is
788 * an e8 byte. Note: the low-order bit corresponds to
789 * the first (lowest address) byte. */
790 u32 e8_mask = _mm_movemask_epi8(cmpresult);
793 /* If e8_mask is 0, then none of these 16 bytes
794 * have value 0xe8. No e8 translation is
795 * needed, and there is no restriction that
796 * carries over to the next 16 bytes. */
797 valid_mask = 0xFFFFFFFF;
799 /* At least one byte has value 0xe8.
801 * The AND with valid_mask accounts for the fact
802 * that we can't start an e8 translation that
803 * overlaps the previous one. */
804 while ((e8_mask &= valid_mask)) {
806 /* Count the number of trailing zeroes
807 * in e8_mask. This will produce the
808 * index of the byte, within the 16, at
809 * which the next e8 translation should
811 u32 bit = __builtin_ctz(e8_mask);
813 /* Do the e8 translation. */
814 u8 *p8 = (u8 *)p128 + bit;
815 undo_call_insn_translation((s32 *)(p8 + 1),
816 p8 - uncompressed_data);
818 /* Don't start an e8 translation in the
820 valid_mask &= ~((u32)0x1F << bit);
822 /* Moving on to the next vector. Shift and set
823 * valid_mask accordingly. */
825 valid_mask |= 0xFFFF0000;
827 } while (++p128 < end128);
831 while (!(valid_mask & 1)) {
836 u8 *p8 = uncompressed_data;
837 #endif /* !__SSE2__ */
839 if (uncompressed_size > 10) {
840 /* Finish any bytes that weren't processed by the vectorized
842 u8 *p8_end = uncompressed_data + uncompressed_size - 10;
845 undo_call_insn_translation((s32 *)(p8 + 1),
846 p8 - uncompressed_data);
851 } while (p8 < p8_end);
856 * Decompresses an LZX-compressed block of data from which the header has already
859 * @block_type: The type of the block (LZX_BLOCKTYPE_VERBATIM or
860 * LZX_BLOCKTYPE_ALIGNED)
861 * @block_size: The size of the block, in bytes.
862 * @num_main_syms: Number of symbols in the main alphabet.
863 * @window: Pointer to the decompression window.
864 * @window_pos: The current position in the window. Will be 0 for the first
866 * @tables: The Huffman decoding tables for the block (main, length, and
867 * aligned offset, the latter only for LZX_BLOCKTYPE_ALIGNED)
868 * @queue: The least-recently-used queue for match offsets.
869 * @istream: The input bitstream for the compressed literals.
872 lzx_decompress_block(int block_type, unsigned block_size,
873 unsigned num_main_syms,
876 const struct lzx_tables *tables,
877 struct lzx_lru_queue *queue,
878 struct input_bitstream *istream)
880 unsigned main_element;
885 end = window_pos + block_size;
886 while (window_pos < end) {
887 ret = read_huffsym_using_maintree(istream, tables,
893 if (main_element < LZX_NUM_CHARS) {
894 /* literal: 0 to LZX_NUM_CHARS - 1 */
895 window[window_pos++] = main_element;
897 /* match: LZX_NUM_CHARS to num_main_syms - 1 */
898 match_len = lzx_decode_match(main_element,
908 window_pos += match_len;
915 lzx_decompress(const void *compressed_data, size_t compressed_size,
916 void *uncompressed_data, size_t uncompressed_size,
919 struct lzx_decompressor *ctx = _ctx;
920 struct input_bitstream istream;
921 struct lzx_lru_queue queue;
926 bool e8_preprocessing_done;
928 LZX_DEBUG("compressed_data = %p, compressed_size = %zu, "
929 "uncompressed_data = %p, uncompressed_size = %zu, "
930 "max_window_size=%u).",
931 compressed_data, compressed_size,
932 uncompressed_data, uncompressed_size,
933 ctx->max_window_size);
935 if (uncompressed_size > ctx->max_window_size) {
936 LZX_DEBUG("Uncompressed size of %zu exceeds "
937 "window size of %u!",
938 uncompressed_size, ctx->max_window_size);
942 memset(ctx->tables.maintree_lens, 0, sizeof(ctx->tables.maintree_lens));
943 memset(ctx->tables.lentree_lens, 0, sizeof(ctx->tables.lentree_lens));
944 lzx_lru_queue_init(&queue);
945 init_input_bitstream(&istream, compressed_data, compressed_size);
947 e8_preprocessing_done = false; /* Set to true if there may be 0xe8 bytes
948 in the uncompressed data. */
950 /* The compressed data will consist of one or more blocks. The
951 * following loop decompresses one block, and it runs until there all
952 * the compressed data has been decompressed, so there are no more
956 window_pos < uncompressed_size;
957 window_pos += block_size)
959 LZX_DEBUG("Reading block header.");
960 ret = lzx_read_block_header(&istream, ctx->num_main_syms,
961 ctx->max_window_size, &block_size,
962 &block_type, &ctx->tables, &queue);
966 LZX_DEBUG("block_size = %u, window_pos = %u",
967 block_size, window_pos);
969 if (block_size > uncompressed_size - window_pos) {
970 LZX_DEBUG("Expected a block size of at "
971 "most %zu bytes (found %u bytes)",
972 uncompressed_size - window_pos, block_size);
976 switch (block_type) {
977 case LZX_BLOCKTYPE_VERBATIM:
978 case LZX_BLOCKTYPE_ALIGNED:
979 if (block_type == LZX_BLOCKTYPE_VERBATIM)
980 LZX_DEBUG("LZX_BLOCKTYPE_VERBATIM");
982 LZX_DEBUG("LZX_BLOCKTYPE_ALIGNED");
983 ret = lzx_decompress_block(block_type,
994 if (ctx->tables.maintree_lens[0xe8] != 0)
995 e8_preprocessing_done = true;
997 case LZX_BLOCKTYPE_UNCOMPRESSED:
998 LZX_DEBUG("LZX_BLOCKTYPE_UNCOMPRESSED");
999 if (istream.data_bytes_left < block_size) {
1000 LZX_DEBUG("Unexpected end of input when "
1001 "reading %u bytes from LZX bitstream "
1002 "(only have %u bytes left)",
1003 block_size, istream.data_bytes_left);
1006 memcpy(&((u8*)uncompressed_data)[window_pos], istream.data,
1008 istream.data += block_size;
1009 istream.data_bytes_left -= block_size;
1010 /* Re-align bitstream if an odd number of bytes were
1012 if (istream.data_bytes_left && (block_size & 1)) {
1013 istream.data_bytes_left--;
1016 e8_preprocessing_done = true;
1020 if (e8_preprocessing_done)
1021 undo_call_insn_preprocessing(uncompressed_data, uncompressed_size);
1026 lzx_free_decompressor(void *_ctx)
1028 struct lzx_decompressor *ctx = _ctx;
1034 lzx_create_decompressor(size_t max_window_size,
1035 const struct wimlib_decompressor_params_header *params,
1038 struct lzx_decompressor *ctx;
1040 if (!lzx_window_size_valid(max_window_size))
1041 return WIMLIB_ERR_INVALID_PARAM;
1043 ctx = MALLOC(sizeof(struct lzx_decompressor));
1045 return WIMLIB_ERR_NOMEM;
1047 ctx->max_window_size = max_window_size;
1048 ctx->num_main_syms = lzx_get_num_main_syms(max_window_size);
1054 const struct decompressor_ops lzx_decompressor_ops = {
1055 .create_decompressor = lzx_create_decompressor,
1056 .decompress = lzx_decompress,
1057 .free_decompressor = lzx_free_decompressor,