/* * lzms_decompress.c * * A decompressor for the LZMS compression format. */ /* * Copyright (C) 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/. */ /* * This is a decompressor for the LZMS compression format used by Microsoft. * This format is not documented, but it is one of the formats supported by the * compression API available in Windows 8, and as of Windows 8 it is one of the * formats that can be used in WIM files. * * This decompressor only implements "raw" decompression, which decompresses a * single LZMS-compressed block. This behavior is the same as that of * Decompress() in the Windows 8 compression API when using a compression handle * created with CreateDecompressor() with the Algorithm parameter specified as * COMPRESS_ALGORITHM_LZMS | COMPRESS_RAW. Presumably, non-raw LZMS data is a * container format from which the locations and sizes (both compressed and * uncompressed) of the constituent blocks can be determined. * * An LZMS-compressed block must be read in 16-bit little endian units from both * directions. One logical bitstream starts at the front of the block and * proceeds forwards. Another logical bitstream starts at the end of the block * and proceeds backwards. Bits read from the forwards bitstream constitute * binary range-encoded data, whereas bits read from the backwards bitstream * constitute Huffman-encoded symbols or verbatim bits. For both bitstreams, * the ordering of the bits within the 16-bit coding units is such that the * first bit is the high-order bit and the last bit is the low-order bit. * * From these two logical bitstreams, an LZMS decompressor can reconstitute the * series of items that make up the LZMS data representation. Each such item * may be a literal byte or a match. Matches may be either traditional LZ77 * matches or "delta" matches, either of which can have its offset encoded * explicitly or encoded via a reference to a recently used (repeat) offset. * * A traditional LZ77 match consists of a length and offset. It asserts that * the sequence of bytes beginning at the current position and extending for the * length is equal to the same-length sequence of bytes at the offset back in * the data buffer. This type of match can be visualized as follows, with the * caveat that the sequences may overlap: * * offset * -------------------- * | | * B[1...len] A[1...len] * * Decoding proceeds as follows: * * do { * *A++ = *B++; * } while (--length); * * On the other hand, a delta match consists of a "span" as well as a length and * offset. A delta match can be visualized as follows, with the caveat that the * various sequences may overlap: * * offset * ----------------------------- * | | * span | span | * ------------- ------------- * | | | | * D[1...len] C[1...len] B[1...len] A[1...len] * * Decoding proceeds as follows: * * do { * *A++ = *B++ + *C++ - *D++; * } while (--length); * * A delta match asserts that the bytewise differences of the A and B sequences * are equal to the bytewise differences of the C and D sequences. The * sequences within each pair are separated by the same number of bytes, the * "span". The inter-pair distance is the "offset". In LZMS, spans are * restricted to powers of 2 between 2**0 and 2**7 inclusively. Offsets are * restricted to multiples of the span. The stored value for the offset is the * "raw offset", which is the real offset divided by the span. * * Delta matches can cover data containing a series of power-of-2 sized integers * that is linearly increasing or decreasing. Another way of thinking about it * is that a delta match can match a longer sequence that is interrupted by a * non-matching byte, provided that the non-matching byte is a continuation of a * linearly changing pattern. Examples of files that may contain data like this * are uncompressed bitmap images, uncompressed digital audio, and Unicode data * tables. To some extent, this match type is a replacement for delta filters * or multimedia filters that are sometimes used in other compression software * (e.g. 'xz --delta --lzma2'). However, on most types of files, delta matches * do not seem to be very useful. * * Both LZ and delta matches may use overlapping sequences. Therefore, they * must be decoded as if only one byte is copied at a time. * * For both LZ and delta matches, any match length in [1, 1073809578] can be * represented. Similarly, any match offset in [1, 1180427428] can be * represented. For delta matches, this range applies to the raw offset, so the * real offset may be larger. * * For LZ matches, up to 3 repeat offsets are allowed, similar to some other * LZ-based formats such as LZX and LZMA. They must updated in an LRU fashion, * except for a quirk: inserting anything to the front of the queue must be * delayed by one LZMS item. The reason for this is presumably that there is * almost no reason to code the same match offset twice in a row, since you * might as well have coded a longer match at that offset. For this same * reason, it also is a requirement that when an offset in the queue is used, * that offset is removed from the queue immediately (and made pending for * front-insertion after the following decoded item), and everything to the * right is shifted left one queue slot. This creates a need for an "overflow" * fourth entry in the queue, even though it is only possible to decode * references to the first 3 entries at any given time. The queue must be * initialized to the offsets {1, 2, 3, 4}. * * Repeat delta matches are handled similarly, but for them the queue contains * (power, raw offset) pairs. This queue must be initialized to * {(0, 1), (0, 2), (0, 3), (0, 4)}. * * Bits from the binary range decoder must be used to disambiguate item types. * The range decoder must hold two state variables: the range, which must * initially be set to 0xffffffff, and the current code, which must initially be * set to the first 32 bits read from the forwards bitstream. The range must be * maintained above 0xffff; when it falls below 0xffff, both the range and code * must be left-shifted by 16 bits and the low 16 bits of the code must be * filled in with the next 16 bits from the forwards bitstream. * * To decode each bit, the binary range decoder requires a probability that is * logically a real number between 0 and 1. Multiplying this probability by the * current range and taking the floor gives the bound between the 0-bit region of * the range and the 1-bit region of the range. However, in LZMS, probabilities * are restricted to values of n/64 where n is an integer is between 1 and 63 * inclusively, so the implementation may use integer operations instead. * Following calculation of the bound, if the current code is in the 0-bit * region, the new range becomes the current code and the decoded bit is 0; * otherwise, the bound must be subtracted from both the range and the code, and * the decoded bit is 1. More information about range coding can be found at * https://en.wikipedia.org/wiki/Range_encoding. Furthermore, note that the * LZMA format also uses range coding and has public domain code available for * it. * * The probability used to range-decode each bit must be taken from a table, of * which one instance must exist for each distinct context, or "binary decision * class", in which a range-decoded bit is needed. At each call of the range * decoder, the appropriate probability must be obtained by indexing the * appropriate probability table with the last 4 (in the context disambiguating * literals from matches), 5 (in the context disambiguating LZ matches from * delta matches), or 6 (in all other contexts) bits recently range-decoded in * that context, ordered such that the most recently decoded bit is the * low-order bit of the index. * * Furthermore, each probability entry itself is variable, as its value must be * maintained as n/64 where n is the number of 0 bits in the most recently * decoded 64 bits with that same entry. This allows the compressed * representation to adapt to the input and use fewer bits to represent the most * likely data; note that LZMA uses a similar scheme. Initially, the most * recently 64 decoded bits for each probability entry are assumed to be * 0x0000000055555555 (high order to low order); therefore, all probabilities * are initially 48/64. During the course of decoding, each probability may be * updated to as low as 0/64 (as a result of reading many consecutive 1 bits * with that entry) or as high as 64/64 (as a result of reading many consecutive * 0 bits with that entry); however, probabilities of 0/64 and 64/64 cannot be * used as-is but rather must be adjusted to 1/64 and 63/64, respectively, * before being used for range decoding. * * Representations of the LZMS items themselves must be read from the backwards * bitstream. For this, there are 5 different Huffman codes used: * * - The literal code, used for decoding literal bytes. Each of the 256 * symbols represents a literal byte. This code must be rebuilt whenever * 1024 symbols have been decoded with it. * * - The LZ offset code, used for decoding the offsets of standard LZ77 * matches. Each symbol represents an offset slot, which corresponds to a * base value and some number of extra bits which must be read and added to * the base value to reconstitute the full offset. The number of symbols in * this code is the number of offset slots needed to represent all possible * offsets in the uncompressed block. This code must be rebuilt whenever * 1024 symbols have been decoded with it. * * - The length code, used for decoding length symbols. Each of the 54 symbols * represents a length slot, which corresponds to a base value and some * number of extra bits which must be read and added to the base value to * reconstitute the full length. This code must be rebuilt whenever 512 * symbols have been decoded with it. * * - The delta offset code, used for decoding the raw offsets of delta matches. * Each symbol corresponds to an offset slot, which corresponds to a base * value and some number of extra bits which must be read and added to the * base value to reconstitute the full raw offset. The number of symbols in * this code is equal to the number of symbols in the LZ offset code. This * code must be rebuilt whenever 1024 symbols have been decoded with it. * * - The delta power code, used for decoding the powers of delta matches. Each * of the 8 symbols corresponds to a power. This code must be rebuilt * whenever 512 symbols have been decoded with it. * * Initially, each Huffman code must be built assuming that each symbol in that * code has frequency 1. Following that, each code must be rebuilt each time a * certain number of symbols, as noted above, has been decoded with it. The * symbol frequencies for a code must be halved after each rebuild of that code; * this makes the codes adapt to the more recent data. * * Like other compression formats such as XPRESS, LZX, and DEFLATE, the LZMS * format requires that all Huffman codes be constructed in canonical form. * This form requires that same-length codewords be lexicographically ordered * the same way as the corresponding symbols and that all shorter codewords * lexicographically precede longer codewords. Such a code can be constructed * directly from codeword lengths. * * Even with the canonical code restriction, the same frequencies can be used to * construct multiple valid Huffman codes. Therefore, the decompressor needs to * construct the right one. Specifically, the LZMS format requires that the * Huffman code be constructed as if the well-known priority queue algorithm is * used and frequency ties are always broken in favor of leaf nodes. * * Codewords in LZMS are guaranteed to not exceed 15 bits. The format otherwise * places no restrictions on codeword length. Therefore, the Huffman code * construction algorithm that a correct LZMS decompressor uses need not * implement length-limited code construction. But if it does (e.g. by virtue * of being shared among multiple compression algorithms), the details of how it * does so are unimportant, provided that the maximum codeword length parameter * is set to at least 15 bits. * * After all LZMS items have been decoded, the data must be postprocessed to * translate absolute address encoded in x86 instructions into their original * relative addresses. * * Details omitted above can be found in the code. Note that in the absence of * an official specification there is no guarantee that this decompressor * handles all possible cases. */ #ifdef HAVE_CONFIG_H # include "config.h" #endif #include "wimlib/compress_common.h" #include "wimlib/decompress_common.h" #include "wimlib/decompressor_ops.h" #include "wimlib/error.h" #include "wimlib/lzms_common.h" #include "wimlib/util.h" /* The TABLEBITS values can be changed; they only affect decoding speed. */ #define LZMS_LITERAL_TABLEBITS 10 #define LZMS_LENGTH_TABLEBITS 10 #define LZMS_LZ_OFFSET_TABLEBITS 10 #define LZMS_DELTA_OFFSET_TABLEBITS 10 #define LZMS_DELTA_POWER_TABLEBITS 8 struct lzms_range_decoder { /* The relevant part of the current range. Although the logical range * for range decoding is a very large integer, only a small portion * matters at any given time, and it can be normalized (shifted left) * whenever it gets too small. */ u32 range; /* The current position in the range encoded by the portion of the input * read so far. */ u32 code; /* Pointer to the next little-endian 16-bit integer in the compressed * input data (reading forwards). */ const le16 *next; /* Pointer to the end of the compressed input data. */ const le16 *end; }; typedef u64 bitbuf_t; struct lzms_input_bitstream { /* Holding variable for bits that have been read from the compressed * data. The bit ordering is high to low. */ bitbuf_t bitbuf; /* Number of bits currently held in @bitbuf. */ unsigned bitsleft; /* Pointer to the one past the next little-endian 16-bit integer in the * compressed input data (reading backwards). */ const le16 *next; /* Pointer to the beginning of the compressed input data. */ const le16 *begin; }; #define BITBUF_NBITS (8 * sizeof(bitbuf_t)) /* Bookkeeping information for an adaptive Huffman code */ struct lzms_huffman_rebuild_info { unsigned num_syms_until_rebuild; unsigned num_syms; unsigned rebuild_freq; u32 *codewords; u32 *freqs; u16 *decode_table; unsigned table_bits; }; struct lzms_decompressor { /* 'last_target_usages' is in union with everything else because it is * only used for postprocessing. */ union { struct { struct lzms_probabilites probs; u16 literal_decode_table[(1 << LZMS_LITERAL_TABLEBITS) + (2 * LZMS_NUM_LITERAL_SYMS)] _aligned_attribute(DECODE_TABLE_ALIGNMENT); u32 literal_freqs[LZMS_NUM_LITERAL_SYMS]; struct lzms_huffman_rebuild_info literal_rebuild_info; u16 lz_offset_decode_table[(1 << LZMS_LZ_OFFSET_TABLEBITS) + ( 2 * LZMS_MAX_NUM_OFFSET_SYMS)] _aligned_attribute(DECODE_TABLE_ALIGNMENT); u32 lz_offset_freqs[LZMS_MAX_NUM_OFFSET_SYMS]; struct lzms_huffman_rebuild_info lz_offset_rebuild_info; u16 length_decode_table[(1 << LZMS_LENGTH_TABLEBITS) + (2 * LZMS_NUM_LENGTH_SYMS)] _aligned_attribute(DECODE_TABLE_ALIGNMENT); u32 length_freqs[LZMS_NUM_LENGTH_SYMS]; struct lzms_huffman_rebuild_info length_rebuild_info; u16 delta_offset_decode_table[(1 << LZMS_DELTA_OFFSET_TABLEBITS) + (2 * LZMS_MAX_NUM_OFFSET_SYMS)] _aligned_attribute(DECODE_TABLE_ALIGNMENT); u32 delta_offset_freqs[LZMS_MAX_NUM_OFFSET_SYMS]; struct lzms_huffman_rebuild_info delta_offset_rebuild_info; u16 delta_power_decode_table[(1 << LZMS_DELTA_POWER_TABLEBITS) + (2 * LZMS_NUM_DELTA_POWER_SYMS)] _aligned_attribute(DECODE_TABLE_ALIGNMENT); u32 delta_power_freqs[LZMS_NUM_DELTA_POWER_SYMS]; struct lzms_huffman_rebuild_info delta_power_rebuild_info; u32 codewords[LZMS_MAX_NUM_SYMS]; }; // struct s32 last_target_usages[65536]; }; // union }; /* Initialize the input bitstream @is to read backwards from the compressed data * buffer @in that is @count 16-bit integers long. */ static void lzms_input_bitstream_init(struct lzms_input_bitstream *is, const le16 *in, size_t count) { is->bitbuf = 0; is->bitsleft = 0; is->next = in + count; is->begin = in; } /* Ensure that at least @num_bits bits are in the bitbuffer variable. * @num_bits cannot be more than 32. */ static inline void lzms_ensure_bits(struct lzms_input_bitstream *is, unsigned num_bits) { unsigned avail; if (is->bitsleft >= num_bits) return; avail = BITBUF_NBITS - is->bitsleft; if (UNALIGNED_ACCESS_IS_FAST && CPU_IS_LITTLE_ENDIAN && WORDSIZE == 8 && likely((u8 *)is->next - (u8 *)is->begin >= 8)) { is->next -= avail >> 4; is->bitbuf |= load_u64_unaligned(is->next) << (avail & 15); is->bitsleft += avail & ~15; } else { if (likely(is->next != is->begin)) is->bitbuf |= (bitbuf_t)le16_to_cpu(*--is->next) << (avail - 16); if (likely(is->next != is->begin)) is->bitbuf |=(bitbuf_t)le16_to_cpu(*--is->next) << (avail - 32); is->bitsleft += 32; } } /* Get @num_bits bits from the bitbuffer variable. */ static inline bitbuf_t lzms_peek_bits(struct lzms_input_bitstream *is, unsigned num_bits) { return (is->bitbuf >> 1) >> (BITBUF_NBITS - num_bits - 1); } /* Remove @num_bits bits from the bitbuffer variable. */ static inline void lzms_remove_bits(struct lzms_input_bitstream *is, unsigned num_bits) { is->bitbuf <<= num_bits; is->bitsleft -= num_bits; } /* Remove and return @num_bits bits from the bitbuffer variable. */ static inline bitbuf_t lzms_pop_bits(struct lzms_input_bitstream *is, unsigned num_bits) { bitbuf_t bits = lzms_peek_bits(is, num_bits); lzms_remove_bits(is, num_bits); return bits; } /* Read @num_bits bits from the input bitstream. */ static inline bitbuf_t lzms_read_bits(struct lzms_input_bitstream *is, unsigned num_bits) { lzms_ensure_bits(is, num_bits); return lzms_pop_bits(is, num_bits); } /* Initialize the range decoder @rd to read forwards from the compressed data * buffer @in that is @count 16-bit integers long. */ static void lzms_range_decoder_init(struct lzms_range_decoder *rd, const le16 *in, size_t count) { rd->range = 0xffffffff; rd->code = ((u32)le16_to_cpu(in[0]) << 16) | le16_to_cpu(in[1]); rd->next = in + 2; rd->end = in + count; } /* * Decode a bit using the range coder. The current state specifies the * probability entry to use. The state and probability entry will be updated * based on the decoded bit. */ static inline int lzms_decode_bit(struct lzms_range_decoder *rd, u32 *state_p, u32 num_states, struct lzms_probability_entry *probs) { struct lzms_probability_entry *prob_entry; u32 prob; u32 bound; /* Load the probability entry corresponding to the current state. */ prob_entry = &probs[*state_p]; /* Update the state early. We'll still need to OR the state with 1 * later if the decoded bit is a 1. */ *state_p = (*state_p << 1) & (num_states - 1); /* Get the probability (out of LZMS_PROBABILITY_DENOMINATOR) that the * next bit is 0. */ prob = lzms_get_probability(prob_entry); /* Normalize if needed. */ if (!(rd->range & 0xFFFF0000)) { rd->range <<= 16; rd->code <<= 16; if (likely(rd->next != rd->end)) rd->code |= le16_to_cpu(*rd->next++); } /* Based on the probability, calculate the bound between the 0-bit * region and the 1-bit region of the range. */ bound = (rd->range >> LZMS_PROBABILITY_BITS) * prob; if (rd->code < bound) { /* Current code is in the 0-bit region of the range. */ rd->range = bound; /* Update the state and probability entry based on the decoded bit. */ lzms_update_probability_entry(prob_entry, 0); return 0; } else { /* Current code is in the 1-bit region of the range. */ rd->range -= bound; rd->code -= bound; /* Update the state and probability entry based on the decoded bit. */ lzms_update_probability_entry(prob_entry, 1); *state_p |= 1; return 1; } } static void lzms_build_huffman_code(struct lzms_huffman_rebuild_info *rebuild_info) { make_canonical_huffman_code(rebuild_info->num_syms, LZMS_MAX_CODEWORD_LENGTH, rebuild_info->freqs, (u8 *)rebuild_info->decode_table, rebuild_info->codewords); make_huffman_decode_table(rebuild_info->decode_table, rebuild_info->num_syms, rebuild_info->table_bits, (u8 *)rebuild_info->decode_table, LZMS_MAX_CODEWORD_LENGTH); rebuild_info->num_syms_until_rebuild = rebuild_info->rebuild_freq; } static void lzms_init_huffman_code(struct lzms_huffman_rebuild_info *rebuild_info, unsigned num_syms, unsigned rebuild_freq, u32 *codewords, u32 *freqs, u16 *decode_table, unsigned table_bits) { rebuild_info->num_syms = num_syms; rebuild_info->rebuild_freq = rebuild_freq; rebuild_info->codewords = codewords; rebuild_info->freqs = freqs; rebuild_info->decode_table = decode_table; rebuild_info->table_bits = table_bits; lzms_init_symbol_frequencies(freqs, num_syms); lzms_build_huffman_code(rebuild_info); } static void lzms_init_huffman_codes(struct lzms_decompressor *d, unsigned num_offset_slots) { lzms_init_huffman_code(&d->literal_rebuild_info, LZMS_NUM_LITERAL_SYMS, LZMS_LITERAL_CODE_REBUILD_FREQ, d->codewords, d->literal_freqs, d->literal_decode_table, LZMS_LITERAL_TABLEBITS); lzms_init_huffman_code(&d->lz_offset_rebuild_info, num_offset_slots, LZMS_LZ_OFFSET_CODE_REBUILD_FREQ, d->codewords, d->lz_offset_freqs, d->lz_offset_decode_table, LZMS_LZ_OFFSET_TABLEBITS); lzms_init_huffman_code(&d->length_rebuild_info, LZMS_NUM_LENGTH_SYMS, LZMS_LENGTH_CODE_REBUILD_FREQ, d->codewords, d->length_freqs, d->length_decode_table, LZMS_LENGTH_TABLEBITS); lzms_init_huffman_code(&d->delta_offset_rebuild_info, num_offset_slots, LZMS_DELTA_OFFSET_CODE_REBUILD_FREQ, d->codewords, d->delta_offset_freqs, d->delta_offset_decode_table, LZMS_DELTA_OFFSET_TABLEBITS); lzms_init_huffman_code(&d->delta_power_rebuild_info, LZMS_NUM_DELTA_POWER_SYMS, LZMS_DELTA_POWER_CODE_REBUILD_FREQ, d->codewords, d->delta_power_freqs, d->delta_power_decode_table, LZMS_DELTA_POWER_TABLEBITS); } static noinline void lzms_rebuild_huffman_code(struct lzms_huffman_rebuild_info *rebuild_info) { lzms_build_huffman_code(rebuild_info); lzms_dilute_symbol_frequencies(rebuild_info->freqs, rebuild_info->num_syms); } static inline unsigned lzms_decode_huffman_symbol(struct lzms_input_bitstream *is, u16 decode_table[], unsigned table_bits, u32 freqs[], struct lzms_huffman_rebuild_info *rebuild_info) { unsigned key_bits; unsigned entry; unsigned sym; lzms_ensure_bits(is, LZMS_MAX_CODEWORD_LENGTH); /* Index the decode table by the next table_bits bits of the input. */ key_bits = lzms_peek_bits(is, table_bits); entry = decode_table[key_bits]; if (likely(entry < 0xC000)) { /* Fast case: The decode table directly provided the symbol and * codeword length. The low 11 bits are the symbol, and the * high 5 bits are the codeword length. */ lzms_remove_bits(is, entry >> 11); sym = entry & 0x7FF; } else { /* Slow case: The codeword for the symbol is longer than * table_bits, so the symbol does not have an entry directly in * the first (1 << table_bits) entries of the decode table. * Traverse the appropriate binary tree bit-by-bit in order to * decode the symbol. */ lzms_remove_bits(is, table_bits); do { key_bits = (entry & 0x3FFF) + lzms_pop_bits(is, 1); } while ((entry = decode_table[key_bits]) >= 0xC000); sym = entry; } freqs[sym]++; if (--rebuild_info->num_syms_until_rebuild == 0) lzms_rebuild_huffman_code(rebuild_info); return sym; } static inline unsigned lzms_decode_literal(struct lzms_decompressor *d, struct lzms_input_bitstream *is) { return lzms_decode_huffman_symbol(is, d->literal_decode_table, LZMS_LITERAL_TABLEBITS, d->literal_freqs, &d->literal_rebuild_info); } static inline u32 lzms_decode_lz_offset(struct lzms_decompressor *d, struct lzms_input_bitstream *is) { unsigned slot = lzms_decode_huffman_symbol(is, d->lz_offset_decode_table, LZMS_LZ_OFFSET_TABLEBITS, d->lz_offset_freqs, &d->lz_offset_rebuild_info); return lzms_offset_slot_base[slot] + lzms_read_bits(is, lzms_extra_offset_bits[slot]); } static inline u32 lzms_decode_length(struct lzms_decompressor *d, struct lzms_input_bitstream *is) { unsigned slot = lzms_decode_huffman_symbol(is, d->length_decode_table, LZMS_LENGTH_TABLEBITS, d->length_freqs, &d->length_rebuild_info); u32 length = lzms_length_slot_base[slot]; unsigned num_extra_bits = lzms_extra_length_bits[slot]; /* Usually most lengths are short and have no extra bits. */ if (num_extra_bits) length += lzms_read_bits(is, num_extra_bits); return length; } static inline u32 lzms_decode_delta_offset(struct lzms_decompressor *d, struct lzms_input_bitstream *is) { unsigned slot = lzms_decode_huffman_symbol(is, d->delta_offset_decode_table, LZMS_DELTA_OFFSET_TABLEBITS, d->delta_offset_freqs, &d->delta_offset_rebuild_info); return lzms_offset_slot_base[slot] + lzms_read_bits(is, lzms_extra_offset_bits[slot]); } static inline unsigned lzms_decode_delta_power(struct lzms_decompressor *d, struct lzms_input_bitstream *is) { return lzms_decode_huffman_symbol(is, d->delta_power_decode_table, LZMS_DELTA_POWER_TABLEBITS, d->delta_power_freqs, &d->delta_power_rebuild_info); } static int lzms_create_decompressor(size_t max_bufsize, void **d_ret) { struct lzms_decompressor *d; if (max_bufsize > LZMS_MAX_BUFFER_SIZE) return WIMLIB_ERR_INVALID_PARAM; d = ALIGNED_MALLOC(sizeof(struct lzms_decompressor), DECODE_TABLE_ALIGNMENT); if (!d) return WIMLIB_ERR_NOMEM; *d_ret = d; return 0; } /* * Decompress @in_nbytes bytes of LZMS-compressed data at @in and write the * uncompressed data, which had original size @out_nbytes, to @out. Return 0 if * successful or -1 if the compressed data is invalid. */ static int lzms_decompress(const void * const restrict in, const size_t in_nbytes, void * const restrict out, const size_t out_nbytes, void * const restrict _d) { struct lzms_decompressor *d = _d; u8 *out_next = out; u8 * const out_end = out + out_nbytes; struct lzms_range_decoder rd; struct lzms_input_bitstream is; /* LRU queues for match sources */ u32 recent_lz_offsets[LZMS_NUM_LZ_REPS + 1]; u64 recent_delta_pairs[LZMS_NUM_DELTA_REPS + 1]; u32 pending_lz_offset = 0; u64 pending_delta_pair = 0; const u8 *lz_offset_still_pending; const u8 *delta_pair_still_pending; /* States and probability entries for item type disambiguation */ u32 main_state = 0; u32 match_state = 0; u32 lz_state = 0; u32 delta_state = 0; u32 lz_rep_states[LZMS_NUM_LZ_REP_DECISIONS] = {}; u32 delta_rep_states[LZMS_NUM_DELTA_REP_DECISIONS] = {}; /* * Requirements on the compressed data: * * 1. LZMS-compressed data is a series of 16-bit integers, so the * compressed data buffer cannot take up an odd number of bytes. * 2. To prevent poor performance on some architectures, we require that * the compressed data buffer is 2-byte aligned. * 3. There must be at least 4 bytes of compressed data, since otherwise * we cannot even initialize the range decoder. */ if ((in_nbytes & 1) || ((uintptr_t)in & 1) || (in_nbytes < 4)) return -1; lzms_range_decoder_init(&rd, in, in_nbytes / sizeof(le16)); lzms_input_bitstream_init(&is, in, in_nbytes / sizeof(le16)); lzms_init_probabilities(&d->probs); lzms_init_huffman_codes(d, lzms_get_num_offset_slots(out_nbytes)); for (int i = 0; i < LZMS_NUM_LZ_REPS + 1; i++) recent_lz_offsets[i] = i + 1; for (int i = 0; i < LZMS_NUM_DELTA_REPS + 1; i++) recent_delta_pairs[i] = i + 1; /* Main decode loop */ while (out_next != out_end) { if (!lzms_decode_bit(&rd, &main_state, LZMS_NUM_MAIN_PROBS, d->probs.main)) { /* Literal */ *out_next++ = lzms_decode_literal(d, &is); } else if (!lzms_decode_bit(&rd, &match_state, LZMS_NUM_MATCH_PROBS, d->probs.match)) { /* LZ match */ u32 offset; u32 length; if (!lzms_decode_bit(&rd, &lz_state, LZMS_NUM_LZ_PROBS, d->probs.lz)) { /* Explicit offset */ offset = lzms_decode_lz_offset(d, &is); } else { /* Repeat offset */ if (pending_lz_offset != 0 && out_next != lz_offset_still_pending) { STATIC_ASSERT(LZMS_NUM_LZ_REPS == 3); recent_lz_offsets[3] = recent_lz_offsets[2]; recent_lz_offsets[2] = recent_lz_offsets[1]; recent_lz_offsets[1] = recent_lz_offsets[0]; recent_lz_offsets[0] = pending_lz_offset; pending_lz_offset = 0; } STATIC_ASSERT(LZMS_NUM_LZ_REPS == 3); if (!lzms_decode_bit(&rd, &lz_rep_states[0], LZMS_NUM_LZ_REP_PROBS, d->probs.lz_rep[0])) { offset = recent_lz_offsets[0]; recent_lz_offsets[0] = recent_lz_offsets[1]; recent_lz_offsets[1] = recent_lz_offsets[2]; recent_lz_offsets[2] = recent_lz_offsets[3]; } else if (!lzms_decode_bit(&rd, &lz_rep_states[1], LZMS_NUM_LZ_REP_PROBS, d->probs.lz_rep[1])) { offset = recent_lz_offsets[1]; recent_lz_offsets[1] = recent_lz_offsets[2]; recent_lz_offsets[2] = recent_lz_offsets[3]; } else { offset = recent_lz_offsets[2]; recent_lz_offsets[2] = recent_lz_offsets[3]; } } if (pending_lz_offset != 0) { STATIC_ASSERT(LZMS_NUM_LZ_REPS == 3); recent_lz_offsets[3] = recent_lz_offsets[2]; recent_lz_offsets[2] = recent_lz_offsets[1]; recent_lz_offsets[1] = recent_lz_offsets[0]; recent_lz_offsets[0] = pending_lz_offset; } pending_lz_offset = offset; length = lzms_decode_length(d, &is); if (unlikely(length > out_end - out_next)) return -1; if (unlikely(offset > out_next - (u8 *)out)) return -1; lz_copy(out_next, length, offset, out_end, LZMS_MIN_MATCH_LENGTH); out_next += length; lz_offset_still_pending = out_next; } else { /* Delta match */ /* (See beginning of file for more information.) */ u32 power; u32 raw_offset; u32 span; u32 offset; const u8 *matchptr; u32 length; if (!lzms_decode_bit(&rd, &delta_state, LZMS_NUM_DELTA_PROBS, d->probs.delta)) { /* Explicit offset */ power = lzms_decode_delta_power(d, &is); raw_offset = lzms_decode_delta_offset(d, &is); } else { /* Repeat offset */ u64 val; if (pending_delta_pair != 0 && out_next != delta_pair_still_pending) { STATIC_ASSERT(LZMS_NUM_DELTA_REPS == 3); recent_delta_pairs[3] = recent_delta_pairs[2]; recent_delta_pairs[2] = recent_delta_pairs[1]; recent_delta_pairs[1] = recent_delta_pairs[0]; recent_delta_pairs[0] = pending_delta_pair; pending_delta_pair = 0; } STATIC_ASSERT(LZMS_NUM_DELTA_REPS == 3); if (!lzms_decode_bit(&rd, &delta_rep_states[0], LZMS_NUM_DELTA_REP_PROBS, d->probs.delta_rep[0])) { val = recent_delta_pairs[0]; recent_delta_pairs[0] = recent_delta_pairs[1]; recent_delta_pairs[1] = recent_delta_pairs[2]; recent_delta_pairs[2] = recent_delta_pairs[3]; } else if (!lzms_decode_bit(&rd, &delta_rep_states[1], LZMS_NUM_DELTA_REP_PROBS, d->probs.delta_rep[1])) { val = recent_delta_pairs[1]; recent_delta_pairs[1] = recent_delta_pairs[2]; recent_delta_pairs[2] = recent_delta_pairs[3]; } else { val = recent_delta_pairs[2]; recent_delta_pairs[2] = recent_delta_pairs[3]; } power = val >> 32; raw_offset = (u32)val; } if (pending_delta_pair != 0) { STATIC_ASSERT(LZMS_NUM_DELTA_REPS == 3); recent_delta_pairs[3] = recent_delta_pairs[2]; recent_delta_pairs[2] = recent_delta_pairs[1]; recent_delta_pairs[1] = recent_delta_pairs[0]; recent_delta_pairs[0] = pending_delta_pair; } pending_delta_pair = raw_offset | ((u64)power << 32); length = lzms_decode_length(d, &is); span = (u32)1 << power; offset = raw_offset << power; /* raw_offset<> power != raw_offset)) return -1; /* offset+span overflows? */ if (unlikely(offset + span < offset)) return -1; /* buffer underrun? */ if (unlikely(offset + span > out_next - (u8 *)out)) return -1; /* buffer overrun? */ if (unlikely(length > out_end - out_next)) return -1; matchptr = out_next - offset; do { *out_next = *matchptr + *(out_next - span) - *(matchptr - span); out_next++; matchptr++; } while (--length); delta_pair_still_pending = out_next; } } lzms_x86_filter(out, out_nbytes, d->last_target_usages, true); return 0; } static void lzms_free_decompressor(void *_d) { struct lzms_decompressor *d = _d; ALIGNED_FREE(d); } const struct decompressor_ops lzms_decompressor_ops = { .create_decompressor = lzms_create_decompressor, .decompress = lzms_decompress, .free_decompressor = lzms_free_decompressor, };