+++ /dev/null
-/*
- * lzx-common.c - Common code for LZX compression and decompression.
- */
-
-/*
- * Copyright (C) 2012, 2013, 2014 Eric Biggers
- *
- * This file is free software; you can redistribute it and/or modify it under
- * the terms of the GNU Lesser General Public License as published by the Free
- * Software Foundation; either version 3 of the License, or (at your option) any
- * later version.
- *
- * This file is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
- * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
- * details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this file; if not, see http://www.gnu.org/licenses/.
- */
-
-#ifdef HAVE_CONFIG_H
-# include "config.h"
-#endif
-
-#include <string.h>
-
-#include "wimlib/bitops.h"
-#include "wimlib/endianness.h"
-#include "wimlib/lzx.h"
-#include "wimlib/unaligned.h"
-#include "wimlib/util.h"
-
-#ifdef __SSE2__
-# include <emmintrin.h>
-#endif
-
-/* Mapping: offset slot => first match offset that uses that offset slot.
- */
-const u32 lzx_offset_slot_base[LZX_MAX_OFFSET_SLOTS] = {
- 0 , 1 , 2 , 3 , 4 , /* 0 --- 4 */
- 6 , 8 , 12 , 16 , 24 , /* 5 --- 9 */
- 32 , 48 , 64 , 96 , 128 , /* 10 --- 14 */
- 192 , 256 , 384 , 512 , 768 , /* 15 --- 19 */
- 1024 , 1536 , 2048 , 3072 , 4096 , /* 20 --- 24 */
- 6144 , 8192 , 12288 , 16384 , 24576 , /* 25 --- 29 */
- 32768 , 49152 , 65536 , 98304 , 131072 , /* 30 --- 34 */
- 196608 , 262144 , 393216 , 524288 , 655360 , /* 35 --- 39 */
- 786432 , 917504 , 1048576, 1179648, 1310720, /* 40 --- 44 */
- 1441792, 1572864, 1703936, 1835008, 1966080, /* 45 --- 49 */
- 2097152 /* 50 */
-};
-
-/* Mapping: offset slot => how many extra bits must be read and added to the
- * corresponding offset slot base to decode the match offset. */
-const u8 lzx_extra_offset_bits[LZX_MAX_OFFSET_SLOTS] = {
- 0 , 0 , 0 , 0 , 1 ,
- 1 , 2 , 2 , 3 , 3 ,
- 4 , 4 , 5 , 5 , 6 ,
- 6 , 7 , 7 , 8 , 8 ,
- 9 , 9 , 10, 10, 11,
- 11, 12, 12, 13, 13,
- 14, 14, 15, 15, 16,
- 16, 17, 17, 17, 17,
- 17, 17, 17, 17, 17,
- 17, 17, 17, 17, 17,
- 17
-};
-
-/* Round the specified compression block size (not LZX block size) up to the
- * next valid LZX window size, and return its order (log2). Or, if the block
- * size is 0 or greater than the largest valid LZX window size, return 0. */
-unsigned
-lzx_get_window_order(size_t max_block_size)
-{
- unsigned order;
-
- if (max_block_size == 0 || max_block_size > LZX_MAX_WINDOW_SIZE)
- return 0;
-
- order = fls32(max_block_size);
-
- if (((u32)1 << order) != max_block_size)
- order++;
-
- return max(order, LZX_MIN_WINDOW_ORDER);
-}
-
-/* Given a valid LZX window order, return the number of symbols that will exist
- * in the main Huffman code. */
-unsigned
-lzx_get_num_main_syms(unsigned window_order)
-{
- u32 window_size = (u32)1 << window_order;
-
- /* NOTE: the calculation *should* be as follows:
- *
- * u32 max_offset = window_size - LZX_MIN_MATCH_LEN;
- * u32 max_adjusted_offset = max_offset + LZX_OFFSET_OFFSET;
- * u32 num_offset_slots = 1 + lzx_get_offset_slot_raw(max_adjusted_offset);
- *
- * However since LZX_MIN_MATCH_LEN == LZX_OFFSET_OFFSET, we would get
- * max_adjusted_offset == window_size, which would bump the number of
- * offset slots up by 1 since every valid LZX window size is equal to a
- * offset slot base value. The format doesn't do this, and instead
- * disallows matches with minimum length and maximum offset. This sets
- * max_adjusted_offset = window_size - 1, so instead we must calculate:
- *
- * num_offset_slots = 1 + lzx_get_offset_slot_raw(window_size - 1);
- *
- * ... which is the same as
- *
- * num_offset_slots = lzx_get_offset_slot_raw(window_size);
- *
- * ... since every valid window size is equal to an offset base value.
- */
- unsigned num_offset_slots = lzx_get_offset_slot_raw(window_size);
-
- /* Now calculate the number of main symbols as LZX_NUM_CHARS literal
- * symbols, plus 8 symbols per offset slot (since there are 8 possible
- * length headers, and we need all (offset slot, length header)
- * combinations). */
- return LZX_NUM_CHARS + (num_offset_slots << 3);
-}
-
-static void
-do_translate_target(void *target, s32 input_pos)
-{
- s32 abs_offset, rel_offset;
-
- rel_offset = get_unaligned_u32_le(target);
- if (rel_offset >= -input_pos && rel_offset < LZX_WIM_MAGIC_FILESIZE) {
- if (rel_offset < LZX_WIM_MAGIC_FILESIZE - input_pos) {
- /* "good translation" */
- abs_offset = rel_offset + input_pos;
- } else {
- /* "compensating translation" */
- abs_offset = rel_offset - LZX_WIM_MAGIC_FILESIZE;
- }
- put_unaligned_u32_le(abs_offset, target);
- }
-}
-
-static void
-undo_translate_target(void *target, s32 input_pos)
-{
- s32 abs_offset, rel_offset;
-
- abs_offset = get_unaligned_u32_le(target);
- if (abs_offset >= 0) {
- if (abs_offset < LZX_WIM_MAGIC_FILESIZE) {
- /* "good translation" */
- rel_offset = abs_offset - input_pos;
- put_unaligned_u32_le(rel_offset, target);
- }
- } else {
- if (abs_offset >= -input_pos) {
- /* "compensating translation" */
- rel_offset = abs_offset + LZX_WIM_MAGIC_FILESIZE;
- put_unaligned_u32_le(rel_offset, target);
- }
- }
-}
-
-/*
- * Do or undo the 'E8' preprocessing used in LZX. Before compression, the
- * uncompressed data is preprocessed by changing the targets of x86 CALL
- * instructions from relative offsets to absolute offsets. After decompression,
- * the translation is undone by changing the targets of x86 CALL instructions
- * from absolute offsets to relative offsets.
- *
- * Note that despite its intent, E8 preprocessing can be done on any data even
- * if it is not actually x86 machine code. In fact, E8 preprocessing appears to
- * always be used in LZX-compressed resources in WIM files; there is no bit to
- * indicate whether it is used or not, unlike in the LZX compressed format as
- * used in cabinet files, where a bit is reserved for that purpose.
- *
- * E8 preprocessing is disabled in the last 6 bytes of the uncompressed data,
- * which really means the 5-byte call instruction cannot start in the last 10
- * bytes of the uncompressed data. This is one of the errors in the LZX
- * documentation.
- *
- * E8 preprocessing does not appear to be disabled after the 32768th chunk of a
- * WIM resource, which apparently is another difference from the LZX compression
- * used in cabinet files.
- *
- * E8 processing is supposed to take the file size as a parameter, as it is used
- * in calculating the translated jump targets. But in WIM files, this file size
- * is always the same (LZX_WIM_MAGIC_FILESIZE == 12000000).
- */
-static void
-lzx_e8_filter(u8 *data, u32 size, void (*process_target)(void *, s32))
-{
-
-#if !defined(__SSE2__) && !defined(__AVX2__)
- /*
- * A worthwhile optimization is to push the end-of-buffer check into the
- * relatively rare E8 case. This is possible if we replace the last six
- * bytes of data with E8 bytes; then we are guaranteed to hit an E8 byte
- * before reaching end-of-buffer. In addition, this scheme guarantees
- * that no translation can begin following an E8 byte in the last 10
- * bytes because a 4-byte offset containing E8 as its high byte is a
- * large negative number that is not valid for translation. That is
- * exactly what we need.
- */
- u8 *tail;
- u8 saved_bytes[6];
- u8 *p;
-
- if (size <= 10)
- return;
-
- tail = &data[size - 6];
- memcpy(saved_bytes, tail, 6);
- memset(tail, 0xE8, 6);
- p = data;
- for (;;) {
- while (*p != 0xE8)
- p++;
- if (p >= tail)
- break;
- (*process_target)(p + 1, p - data);
- p += 5;
- }
- memcpy(tail, saved_bytes, 6);
-#else
- /* SSE2 or AVX-2 optimized version for x86_64 */
-
- u8 *p = data;
- u64 valid_mask = ~0;
-
- if (size <= 10)
- return;
-#ifdef __AVX2__
-# define ALIGNMENT_REQUIRED 32
-#else
-# define ALIGNMENT_REQUIRED 16
-#endif
-
- /* Process one byte at a time until the pointer is properly aligned. */
- while ((uintptr_t)p % ALIGNMENT_REQUIRED != 0) {
- if (p >= data + size - 10)
- return;
- if (*p == 0xE8 && (valid_mask & 1)) {
- (*process_target)(p + 1, p - data);
- valid_mask &= ~0x1F;
- }
- p++;
- valid_mask >>= 1;
- valid_mask |= (u64)1 << 63;
- }
-
- if (data + size - p >= 64) {
-
- /* Vectorized processing */
-
- /* Note: we use a "trap" E8 byte to eliminate the need to check
- * for end-of-buffer in the inner loop. This byte is carefully
- * positioned so that it will never be changed by a previous
- * translation before it is detected. */
-
- u8 *trap = p + ((data + size - p) & ~31) - 32 + 4;
- u8 saved_byte = *trap;
- *trap = 0xE8;
-
- for (;;) {
- u32 e8_mask;
- u8 *orig_p = p;
- #ifdef __SSE2__
- const __m128i e8_bytes = _mm_set1_epi8(0xE8);
- for (;;) {
- /* Read the next 32 bytes of data and test them
- * for E8 bytes. */
- __m128i bytes1 = *(const __m128i *)p;
- __m128i bytes2 = *(const __m128i *)(p + 16);
- __m128i cmpresult1 = _mm_cmpeq_epi8(bytes1, e8_bytes);
- __m128i cmpresult2 = _mm_cmpeq_epi8(bytes2, e8_bytes);
- u32 mask1 = _mm_movemask_epi8(cmpresult1);
- u32 mask2 = _mm_movemask_epi8(cmpresult2);
- /* The masks have a bit set for each E8 byte.
- * We stay in this fast inner loop as long as
- * there are no E8 bytes. */
- if (mask1 | mask2) {
- e8_mask = mask1 | (mask2 << 16);
- break;
- }
- p += 32;
- }
- #else
- /* AVX-2 */
- const __m256i e8_bytes = _mm256_set1_epi8(0xE8);
- for (;;) {
- __m256i bytes = *(const __m256i *)p;
- __m256i cmpresult = _mm256_cmpeq_epi8(bytes, e8_bytes);
- e8_mask = _mm256_movemask_epi8(cmpresult);
- if (e8_mask)
- break;
- p += 32;
- }
- #endif
-
- /* Did we pass over data with no E8 bytes? */
- if (p != orig_p)
- valid_mask = ~0;
-
- /* Are we nearing end-of-buffer? */
- if (p == trap - 4)
- break;
-
- /* Process the E8 bytes. However, the AND with
- * 'valid_mask' ensures we never process an E8 byte that
- * was itself part of a translation target. */
- while ((e8_mask &= valid_mask)) {
- unsigned bit = ffs32(e8_mask);
- (*process_target)(p + bit + 1, p + bit - data);
- valid_mask &= ~((u64)0x1F << bit);
- }
-
- valid_mask >>= 32;
- valid_mask |= 0xFFFFFFFF00000000;
- p += 32;
- }
-
- *trap = saved_byte;
- }
-
- /* Approaching the end of the buffer; process one byte a time. */
- while (p < data + size - 10) {
- if (*p == 0xE8 && (valid_mask & 1)) {
- (*process_target)(p + 1, p - data);
- valid_mask &= ~0x1F;
- }
- p++;
- valid_mask >>= 1;
- valid_mask |= (u64)1 << 63;
- }
-#endif /* __SSE2__ || __AVX2__ */
-}
-
-void
-lzx_do_e8_preprocessing(u8 *data, u32 size)
-{
- lzx_e8_filter(data, size, do_translate_target);
-}
-
-void
-lzx_undo_e8_preprocessing(u8 *data, u32 size)
-{
- lzx_e8_filter(data, size, undo_translate_target);
-}
projects / wimlib / blobdiff