/* * lzx_common.c - Common code for LZX compression and decompression. */ /* * Copyright (C) 2012, 2013, 2014, 2015 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 #ifdef __SSE2__ # include #endif #ifdef __AVX2__ # include #endif #include "wimlib/bitops.h" #include "wimlib/endianness.h" #include "wimlib/lzx_common.h" #include "wimlib/unaligned.h" #include "wimlib/util.h" /* Mapping: offset slot => first match offset that uses that offset slot. */ const u32 lzx_offset_slot_base[LZX_MAX_OFFSET_SLOTS + 1] = { 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 /* extra */ }; /* 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, }; /* Round the specified buffer size up to the next valid LZX window size, and * return its order (log2). Or, if the buffer size is 0 or greater than the * largest valid LZX window size, return 0. */ unsigned lzx_get_window_order(size_t max_bufsize) { unsigned order; if (max_bufsize == 0 || max_bufsize > LZX_MAX_WINDOW_SIZE) return 0; order = fls32(max_bufsize); if (((u32)1 << order) != max_bufsize) 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) { /* Note: one would expect that the maximum match offset would be * 'window_size - LZX_MIN_MATCH_LEN', which would occur if the first two * bytes were to match the last two bytes. However, the format * disallows this case. This reduces the number of needed offset slots * by 1. */ u32 window_size = (u32)1 << window_order; u32 max_adjusted_offset = (window_size - LZX_MIN_MATCH_LEN - 1) + LZX_OFFSET_ADJUSTMENT; unsigned num_offset_slots = 30; while (max_adjusted_offset >= lzx_offset_slot_base[num_offset_slots]) num_offset_slots++; return LZX_NUM_CHARS + (num_offset_slots * LZX_NUM_LEN_HEADERS); } static void do_translate_target(void *target, s32 input_pos) { s32 abs_offset, rel_offset; rel_offset = get_unaligned_le32(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_le32(abs_offset, target); } } static void undo_translate_target(void *target, s32 input_pos) { s32 abs_offset, rel_offset; abs_offset = get_unaligned_le32(target); if (abs_offset >= 0) { if (abs_offset < LZX_WIM_MAGIC_FILESIZE) { /* "good translation" */ rel_offset = abs_offset - input_pos; put_unaligned_le32(rel_offset, target); } } else { if (abs_offset >= -input_pos) { /* "compensating translation" */ rel_offset = abs_offset + LZX_WIM_MAGIC_FILESIZE; put_unaligned_le32(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 __AVX2__ 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; } #else 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; } #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_preprocess(u8 *data, u32 size) { lzx_e8_filter(data, size, do_translate_target); } void lzx_postprocess(u8 *data, u32 size) { lzx_e8_filter(data, size, undo_translate_target); }