/* * lzx-compress.c * * LZX compression routines */ /* * Copyright (C) 2012, 2013 Eric Biggers * * This file is part of wimlib, a library for working with WIM files. * * wimlib is free software; you can redistribute it and/or modify it under the * terms of the GNU General Public License as published by the Free * Software Foundation; either version 3 of the License, or (at your option) * any later version. * * wimlib 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 General Public License for more * details. * * You should have received a copy of the GNU General Public License * along with wimlib; if not, see http://www.gnu.org/licenses/. */ /* * This file contains a compressor for the LZX compression format, as used in * the WIM file format. * * Format * ====== * * First, the primary reference for the LZX compression format is the * specification released by Microsoft. * * Second, the comments in lzx-decompress.c provide some more information about * the LZX compression format, including errors in the Microsoft specification. * * Do note that LZX shares many similarities with DEFLATE, the algorithm used by * zlib and gzip. Both LZX and DEFLATE use LZ77 matching and Huffman coding, * and certain other details are quite similar, such as the method for storing * Huffman codes. However, some of the main differences are: * * - LZX preprocesses the data to attempt to make x86 machine code slightly more * compressible before attempting to compress it further. * - LZX uses a "main" alphabet which combines literals and matches, with the * match symbols containing a "length header" (giving all or part of the match * length) and a "position slot" (giving, roughly speaking, the order of * magnitude of the match offset). * - LZX does not have static Huffman blocks; however it does have two types of * dynamic Huffman blocks ("aligned offset" and "verbatim"). * - LZX has a minimum match length of 2 rather than 3. * - In LZX, match offsets 0 through 2 actually represent entries in an LRU * queue of match offsets. This is very useful for certain types of files, * such as binary files that have repeating records. * * Algorithms * ========== * * There are actually two distinct overall algorithms implemented here. We * shall refer to them as the "slow" algorithm and the "fast" algorithm. The * "slow" algorithm spends more time compressing to achieve a higher compression * ratio compared to the "fast" algorithm. More details are presented below. * * Slow algorithm * -------------- * * The "slow" algorithm to generate LZX-compressed data is roughly as follows: * * 1. Preprocess the input data to translate the targets of x86 call * instructions to absolute offsets. * * 2. Build the suffix array and inverse suffix array for the input data. The * suffix array contains the indices of all suffixes of the input data, * sorted lexcographically by the corresponding suffixes. The "position" of * a suffix is the index of that suffix in the original string, whereas the * "rank" of a suffix is the index at which that suffix's position is found * in the suffix array. * * 3. Build the longest common prefix array corresponding to the suffix array. * * 4. For each suffix, find the highest lower ranked suffix that has a lower * position, the lowest higher ranked suffix that has a lower position, and * the length of the common prefix shared between each. This information is * later used to link suffix ranks into a doubly-linked list for searching * the suffix array. * * 5. Set a default cost model for matches/literals. * * 6. Determine the lowest cost sequence of LZ77 matches ((offset, length) * pairs) and literal bytes to divide the input into. Raw match-finding is * done by searching the suffix array using a linked list to avoid * considering any suffixes that start after the current position. Each run * of the match-finder returns the approximate lowest-cost longest match as * well as any shorter matches that have even lower approximate costs. Each * such run also adds the suffix rank of the current position into the linked * list being used to search the suffix array. Parsing, or match-choosing, * is solved as a minimum-cost path problem using a forward "optimal parsing" * algorithm based on the Deflate encoder from 7-Zip. This algorithm moves * forward calculating the minimum cost to reach each byte until either a * very long match is found or until a position is found at which no matches * start or overlap. * * 7. Build the Huffman codes needed to output the matches/literals. * * 8. Up to a certain number of iterations, use the resulting Huffman codes to * refine a cost model and go back to Step #6 to determine an improved * sequence of matches and literals. * * 9. Output the resulting block using the match/literal sequences and the * Huffman codes that were computed for the block. * * Note: the algorithm does not yet attempt to split the input into multiple LZX * blocks; it instead uses a series of blocks of LZX_DIV_BLOCK_SIZE bytes. * * Fast algorithm * -------------- * * The fast algorithm (and the only one available in wimlib v1.5.1 and earlier) * spends much less time on the main bottlenecks of the compression process --- * that is, the match finding and match choosing. Matches are found and chosen * with hash chains using a greedy parse with one position of look-ahead. No * block splitting is done; only compressing the full input into an aligned * offset block is considered. * * Acknowledgments * =============== * * Acknowledgments to several open-source projects and research papers that made * it possible to implement this code: * * - divsufsort (author: Yuta Mori), for the suffix array construction code, * located in a separate directory (divsufsort/). * * - "Linear-Time Longest-Common-Prefix Computation in Suffix Arrays and Its * Applications" (Kasai et al. 2001), for the LCP array computation. * * - "LPF computation revisited" (Crochemore et al. 2009) for the prev and next * array computations. * * - 7-Zip (author: Igor Pavlov) for the algorithm for forward optimal parsing * (match-choosing). * * - zlib (author: Jean-loup Gailly and Mark Adler), for the hash table * match-finding algorithm (used in lz77.c). * * - lzx-compress (author: Matthew T. Russotto), on which some parts of this * code were originally based. */ #ifdef HAVE_CONFIG_H # include "config.h" #endif #include "wimlib.h" #include "wimlib/compressor_ops.h" #include "wimlib/compress_common.h" #include "wimlib/endianness.h" #include "wimlib/error.h" #include "wimlib/lz_hash.h" #include "wimlib/lz_sarray.h" #include "wimlib/lzx.h" #include "wimlib/util.h" #include #ifdef ENABLE_LZX_DEBUG # include "wimlib/decompress_common.h" #endif typedef u32 block_cost_t; #define INFINITE_BLOCK_COST (~(block_cost_t)0) #define LZX_OPTIM_ARRAY_SIZE 4096 #define LZX_DIV_BLOCK_SIZE 32768 #define LZX_MAX_CACHE_PER_POS 10 /* Codewords for the LZX main, length, and aligned offset Huffman codes */ struct lzx_codewords { u16 main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; u16 len[LZX_LENCODE_NUM_SYMBOLS]; u16 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; }; /* Codeword lengths (in bits) for the LZX main, length, and aligned offset * Huffman codes. * * A 0 length means the codeword has zero frequency. */ struct lzx_lens { u8 main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; u8 len[LZX_LENCODE_NUM_SYMBOLS]; u8 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; }; /* Costs for the LZX main, length, and aligned offset Huffman symbols. * * If a codeword has zero frequency, it must still be assigned some nonzero cost * --- generally a high cost, since even if it gets used in the next iteration, * it probably will not be used very times. */ struct lzx_costs { u8 main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; u8 len[LZX_LENCODE_NUM_SYMBOLS]; u8 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; }; /* The LZX main, length, and aligned offset Huffman codes */ struct lzx_codes { struct lzx_codewords codewords; struct lzx_lens lens; }; /* Tables for tallying symbol frequencies in the three LZX alphabets */ struct lzx_freqs { input_idx_t main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; input_idx_t len[LZX_LENCODE_NUM_SYMBOLS]; input_idx_t aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; }; /* LZX intermediate match/literal format */ struct lzx_match { /* Bit Description * * 31 1 if a match, 0 if a literal. * * 30-25 position slot. This can be at most 50, so it will fit in 6 * bits. * * 8-24 position footer. This is the offset of the real formatted * offset from the position base. This can be at most 17 bits * (since lzx_extra_bits[LZX_MAX_POSITION_SLOTS - 1] is 17). * * 0-7 length of match, minus 2. This can be at most * (LZX_MAX_MATCH_LEN - 2) == 255, so it will fit in 8 bits. */ u32 data; }; /* Specification for an LZX block. */ struct lzx_block_spec { /* One of the LZX_BLOCKTYPE_* constants indicating which type of this * block. */ int block_type; /* 0-based position in the window at which this block starts. */ input_idx_t window_pos; /* The number of bytes of uncompressed data this block represents. */ input_idx_t block_size; /* The position in the 'chosen_matches' array in the `struct * lzx_compressor' at which the match/literal specifications for * this block begin. */ input_idx_t chosen_matches_start_pos; /* The number of match/literal specifications for this block. */ input_idx_t num_chosen_matches; /* Huffman codes for this block. */ struct lzx_codes codes; }; /* Include template for the match-choosing algorithm. */ #define LZ_COMPRESSOR struct lzx_compressor #define LZ_ADAPTIVE_STATE struct lzx_lru_queue struct lzx_compressor; #include "wimlib/lz_optimal.h" /* State of the LZX compressor. */ struct lzx_compressor { /* The parameters that were used to create the compressor. */ struct wimlib_lzx_compressor_params params; /* The buffer of data to be compressed. * * 0xe8 byte preprocessing is done directly on the data here before * further compression. * * Note that this compressor does *not* use a real sliding window!!!! * It's not needed in the WIM format, since every chunk is compressed * independently. This is by design, to allow random access to the * chunks. * * We reserve a few extra bytes to potentially allow reading off the end * of the array in the match-finding code for optimization purposes * (currently only needed for the hash chain match-finder). */ u8 *window; /* Number of bytes of data to be compressed, which is the number of * bytes of data in @window that are actually valid. */ input_idx_t window_size; /* Allocated size of the @window. */ input_idx_t max_window_size; /* Number of symbols in the main alphabet (depends on the * @max_window_size since it determines the maximum allowed offset). */ unsigned num_main_syms; /* The current match offset LRU queue. */ struct lzx_lru_queue queue; /* Space for the sequences of matches/literals that were chosen for each * block. */ struct lzx_match *chosen_matches; /* Information about the LZX blocks the preprocessed input was divided * into. */ struct lzx_block_spec *block_specs; /* Number of LZX blocks the input was divided into; a.k.a. the number of * elements of @block_specs that are valid. */ unsigned num_blocks; /* This is simply filled in with zeroes and used to avoid special-casing * the output of the first compressed Huffman code, which conceptually * has a delta taken from a code with all symbols having zero-length * codewords. */ struct lzx_codes zero_codes; /* The current cost model. */ struct lzx_costs costs; /* Fast algorithm only: Array of hash table links. */ input_idx_t *prev_tab; /* Slow algorithm only: Suffix array match-finder. */ struct lz_sarray lz_sarray; /* Position in window of next match to return. */ input_idx_t match_window_pos; /* The match-finder shall ensure the length of matches does not exceed * this position in the input. */ input_idx_t match_window_end; /* Matches found by the match-finder are cached in the following array * to achieve a slight speedup when the same matches are needed on * subsequent passes. This is suboptimal because different matches may * be preferred with different cost models, but seems to be a worthwhile * speedup. */ struct raw_match *cached_matches; unsigned cached_matches_pos; bool matches_cached; /* Match chooser. */ struct lz_match_chooser mc; }; /* Returns the LZX position slot that corresponds to a given match offset, * taking into account the recent offset queue and updating it if the offset is * found in it. */ static unsigned lzx_get_position_slot(unsigned offset, struct lzx_lru_queue *queue) { unsigned position_slot; /* See if the offset was recently used. */ for (unsigned i = 0; i < LZX_NUM_RECENT_OFFSETS; i++) { if (offset == queue->R[i]) { /* Found it. */ /* Bring the repeat offset to the front of the * queue. Note: this is, in fact, not a real * LRU queue because repeat matches are simply * swapped to the front. */ swap(queue->R[0], queue->R[i]); /* The resulting position slot is simply the first index * at which the offset was found in the queue. */ return i; } } /* The offset was not recently used; look up its real position slot. */ position_slot = lzx_get_position_slot_raw(offset + LZX_OFFSET_OFFSET); /* Bring the new offset to the front of the queue. */ for (unsigned i = LZX_NUM_RECENT_OFFSETS - 1; i > 0; i--) queue->R[i] = queue->R[i - 1]; queue->R[0] = offset; return position_slot; } /* Build the main, length, and aligned offset Huffman codes used in LZX. * * This takes as input the frequency tables for each code and produces as output * a set of tables that map symbols to codewords and codeword lengths. */ static void lzx_make_huffman_codes(const struct lzx_freqs *freqs, struct lzx_codes *codes, unsigned num_main_syms) { make_canonical_huffman_code(num_main_syms, LZX_MAX_MAIN_CODEWORD_LEN, freqs->main, codes->lens.main, codes->codewords.main); make_canonical_huffman_code(LZX_LENCODE_NUM_SYMBOLS, LZX_MAX_LEN_CODEWORD_LEN, freqs->len, codes->lens.len, codes->codewords.len); make_canonical_huffman_code(LZX_ALIGNEDCODE_NUM_SYMBOLS, LZX_MAX_ALIGNED_CODEWORD_LEN, freqs->aligned, codes->lens.aligned, codes->codewords.aligned); } /* * Output a precomputed LZX match. * * @out: * The bitstream to which to write the match. * @block_type: * The type of the LZX block (LZX_BLOCKTYPE_ALIGNED or * LZX_BLOCKTYPE_VERBATIM) * @match: * The match, as a (length, offset) pair. * @codes: * Pointer to a structure that contains the codewords for the main, length, * and aligned offset Huffman codes for the current LZX compressed block. */ static void lzx_write_match(struct output_bitstream *out, int block_type, struct lzx_match match, const struct lzx_codes *codes) { /* low 8 bits are the match length minus 2 */ unsigned match_len_minus_2 = match.data & 0xff; /* Next 17 bits are the position footer */ unsigned position_footer = (match.data >> 8) & 0x1ffff; /* 17 bits */ /* Next 6 bits are the position slot. */ unsigned position_slot = (match.data >> 25) & 0x3f; /* 6 bits */ unsigned len_header; unsigned len_footer; unsigned main_symbol; unsigned num_extra_bits; unsigned verbatim_bits; unsigned aligned_bits; /* If the match length is less than MIN_MATCH_LEN (= 2) + * NUM_PRIMARY_LENS (= 7), the length header contains * the match length minus MIN_MATCH_LEN, and there is no * length footer. * * Otherwise, the length header contains * NUM_PRIMARY_LENS, and the length footer contains * the match length minus NUM_PRIMARY_LENS minus * MIN_MATCH_LEN. */ if (match_len_minus_2 < LZX_NUM_PRIMARY_LENS) { len_header = match_len_minus_2; /* No length footer-- mark it with a special * value. */ len_footer = (unsigned)(-1); } else { len_header = LZX_NUM_PRIMARY_LENS; len_footer = match_len_minus_2 - LZX_NUM_PRIMARY_LENS; } /* Combine the position slot with the length header into a single symbol * that will be encoded with the main code. * * The actual main symbol is offset by LZX_NUM_CHARS because values * under LZX_NUM_CHARS are used to indicate a literal byte rather than a * match. */ main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS; /* Output main symbol. */ bitstream_put_bits(out, codes->codewords.main[main_symbol], codes->lens.main[main_symbol]); /* If there is a length footer, output it using the * length Huffman code. */ if (len_footer != (unsigned)(-1)) { bitstream_put_bits(out, codes->codewords.len[len_footer], codes->lens.len[len_footer]); } num_extra_bits = lzx_get_num_extra_bits(position_slot); /* For aligned offset blocks with at least 3 extra bits, output the * verbatim bits literally, then the aligned bits encoded using the * aligned offset code. Otherwise, only the verbatim bits need to be * output. */ if ((block_type == LZX_BLOCKTYPE_ALIGNED) && (num_extra_bits >= 3)) { verbatim_bits = position_footer >> 3; bitstream_put_bits(out, verbatim_bits, num_extra_bits - 3); aligned_bits = (position_footer & 7); bitstream_put_bits(out, codes->codewords.aligned[aligned_bits], codes->lens.aligned[aligned_bits]); } else { /* verbatim bits is the same as the position * footer, in this case. */ bitstream_put_bits(out, position_footer, num_extra_bits); } } /* Output an LZX literal (encoded with the main Huffman code). */ static void lzx_write_literal(struct output_bitstream *out, u8 literal, const struct lzx_codes *codes) { bitstream_put_bits(out, codes->codewords.main[literal], codes->lens.main[literal]); } static unsigned lzx_build_precode(const u8 lens[restrict], const u8 prev_lens[restrict], const unsigned num_syms, input_idx_t precode_freqs[restrict LZX_PRECODE_NUM_SYMBOLS], u8 output_syms[restrict num_syms], u8 precode_lens[restrict LZX_PRECODE_NUM_SYMBOLS], u16 precode_codewords[restrict LZX_PRECODE_NUM_SYMBOLS], unsigned *num_additional_bits_ret) { memset(precode_freqs, 0, LZX_PRECODE_NUM_SYMBOLS * sizeof(precode_freqs[0])); /* Since the code word lengths use a form of RLE encoding, the goal here * is to find each run of identical lengths when going through them in * symbol order (including runs of length 1). For each run, as many * lengths are encoded using RLE as possible, and the rest are output * literally. * * output_syms[] will be filled in with the length symbols that will be * output, including RLE codes, not yet encoded using the precode. * * cur_run_len keeps track of how many code word lengths are in the * current run of identical lengths. */ unsigned output_syms_idx = 0; unsigned cur_run_len = 1; unsigned num_additional_bits = 0; for (unsigned i = 1; i <= num_syms; i++) { if (i != num_syms && lens[i] == lens[i - 1]) { /* Still in a run--- keep going. */ cur_run_len++; continue; } /* Run ended! Check if it is a run of zeroes or a run of * nonzeroes. */ /* The symbol that was repeated in the run--- not to be confused * with the length *of* the run (cur_run_len) */ unsigned len_in_run = lens[i - 1]; if (len_in_run == 0) { /* A run of 0's. Encode it in as few length * codes as we can. */ /* The magic length 18 indicates a run of 20 + n zeroes, * where n is an uncompressed literal 5-bit integer that * follows the magic length. */ while (cur_run_len >= 20) { unsigned additional_bits; additional_bits = min(cur_run_len - 20, 0x1f); num_additional_bits += 5; precode_freqs[18]++; output_syms[output_syms_idx++] = 18; output_syms[output_syms_idx++] = additional_bits; cur_run_len -= 20 + additional_bits; } /* The magic length 17 indicates a run of 4 + n zeroes, * where n is an uncompressed literal 4-bit integer that * follows the magic length. */ while (cur_run_len >= 4) { unsigned additional_bits; additional_bits = min(cur_run_len - 4, 0xf); num_additional_bits += 4; precode_freqs[17]++; output_syms[output_syms_idx++] = 17; output_syms[output_syms_idx++] = additional_bits; cur_run_len -= 4 + additional_bits; } } else { /* A run of nonzero lengths. */ /* The magic length 19 indicates a run of 4 + n * nonzeroes, where n is a literal bit that follows the * magic length, and where the value of the lengths in * the run is given by an extra length symbol, encoded * with the precode, that follows the literal bit. * * The extra length symbol is encoded as a difference * from the length of the codeword for the first symbol * in the run in the previous code. * */ while (cur_run_len >= 4) { unsigned additional_bits; signed char delta; additional_bits = (cur_run_len > 4); num_additional_bits += 1; delta = (signed char)prev_lens[i - cur_run_len] - (signed char)len_in_run; if (delta < 0) delta += 17; precode_freqs[19]++; precode_freqs[(unsigned char)delta]++; output_syms[output_syms_idx++] = 19; output_syms[output_syms_idx++] = additional_bits; output_syms[output_syms_idx++] = delta; cur_run_len -= 4 + additional_bits; } } /* Any remaining lengths in the run are outputted without RLE, * as a difference from the length of that codeword in the * previous code. */ while (cur_run_len > 0) { signed char delta; delta = (signed char)prev_lens[i - cur_run_len] - (signed char)len_in_run; if (delta < 0) delta += 17; precode_freqs[(unsigned char)delta]++; output_syms[output_syms_idx++] = delta; cur_run_len--; } cur_run_len = 1; } /* Build the precode from the frequencies of the length symbols. */ make_canonical_huffman_code(LZX_PRECODE_NUM_SYMBOLS, LZX_MAX_PRE_CODEWORD_LEN, precode_freqs, precode_lens, precode_codewords); *num_additional_bits_ret = num_additional_bits; return output_syms_idx; } /* * Output a Huffman code in the compressed form used in LZX. * * The Huffman code is represented in the output as a logical series of codeword * lengths from which the Huffman code, which must be in canonical form, can be * reconstructed. * * The codeword lengths are themselves compressed using a separate Huffman code, * the "precode", which contains a symbol for each possible codeword length in * the larger code as well as several special symbols to represent repeated * codeword lengths (a form of run-length encoding). The precode is itself * constructed in canonical form, and its codeword lengths are represented * literally in 20 4-bit fields that immediately precede the compressed codeword * lengths of the larger code. * * Furthermore, the codeword lengths of the larger code are actually represented * as deltas from the codeword lengths of the corresponding code in the previous * block. * * @out: * Bitstream to which to write the compressed Huffman code. * @lens: * The codeword lengths, indexed by symbol, in the Huffman code. * @prev_lens: * The codeword lengths, indexed by symbol, in the corresponding Huffman * code in the previous block, or all zeroes if this is the first block. * @num_syms: * The number of symbols in the Huffman code. */ static void lzx_write_compressed_code(struct output_bitstream *out, const u8 lens[restrict], const u8 prev_lens[restrict], unsigned num_syms) { input_idx_t precode_freqs[LZX_PRECODE_NUM_SYMBOLS]; u8 output_syms[num_syms]; u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS]; u16 precode_codewords[LZX_PRECODE_NUM_SYMBOLS]; unsigned i; unsigned num_output_syms; u8 precode_sym; unsigned dummy; num_output_syms = lzx_build_precode(lens, prev_lens, num_syms, precode_freqs, output_syms, precode_lens, precode_codewords, &dummy); /* Write the lengths of the precode codes to the output. */ for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) bitstream_put_bits(out, precode_lens[i], LZX_PRECODE_ELEMENT_SIZE); /* Write the length symbols, encoded with the precode, to the output. */ for (i = 0; i < num_output_syms; ) { precode_sym = output_syms[i++]; bitstream_put_bits(out, precode_codewords[precode_sym], precode_lens[precode_sym]); switch (precode_sym) { case 17: bitstream_put_bits(out, output_syms[i++], 4); break; case 18: bitstream_put_bits(out, output_syms[i++], 5); break; case 19: bitstream_put_bits(out, output_syms[i++], 1); bitstream_put_bits(out, precode_codewords[output_syms[i]], precode_lens[output_syms[i]]); i++; break; default: break; } } } /* * Write all matches and literal bytes (which were precomputed) in an LZX * compressed block to the output bitstream in the final compressed * representation. * * @ostream * The output bitstream. * @block_type * The chosen type of the LZX compressed block (LZX_BLOCKTYPE_ALIGNED or * LZX_BLOCKTYPE_VERBATIM). * @match_tab * The array of matches/literals to output. * @match_count * Number of matches/literals to output (length of @match_tab). * @codes * The main, length, and aligned offset Huffman codes for the current * LZX compressed block. */ static void lzx_write_matches_and_literals(struct output_bitstream *ostream, int block_type, const struct lzx_match match_tab[], unsigned match_count, const struct lzx_codes *codes) { for (unsigned i = 0; i < match_count; i++) { struct lzx_match match = match_tab[i]; /* The high bit of the 32-bit intermediate representation * indicates whether the item is an actual LZ-style match (1) or * a literal byte (0). */ if (match.data & 0x80000000) lzx_write_match(ostream, block_type, match, codes); else lzx_write_literal(ostream, match.data, codes); } } static void lzx_assert_codes_valid(const struct lzx_codes * codes, unsigned num_main_syms) { #ifdef ENABLE_LZX_DEBUG unsigned i; for (i = 0; i < num_main_syms; i++) LZX_ASSERT(codes->lens.main[i] <= LZX_MAX_MAIN_CODEWORD_LEN); for (i = 0; i < LZX_LENCODE_NUM_SYMBOLS; i++) LZX_ASSERT(codes->lens.len[i] <= LZX_MAX_LEN_CODEWORD_LEN); for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) LZX_ASSERT(codes->lens.aligned[i] <= LZX_MAX_ALIGNED_CODEWORD_LEN); const unsigned tablebits = 10; u16 decode_table[(1 << tablebits) + (2 * max(num_main_syms, LZX_LENCODE_NUM_SYMBOLS))] _aligned_attribute(DECODE_TABLE_ALIGNMENT); LZX_ASSERT(0 == make_huffman_decode_table(decode_table, num_main_syms, min(tablebits, LZX_MAINCODE_TABLEBITS), codes->lens.main, LZX_MAX_MAIN_CODEWORD_LEN)); LZX_ASSERT(0 == make_huffman_decode_table(decode_table, LZX_LENCODE_NUM_SYMBOLS, min(tablebits, LZX_LENCODE_TABLEBITS), codes->lens.len, LZX_MAX_LEN_CODEWORD_LEN)); LZX_ASSERT(0 == make_huffman_decode_table(decode_table, LZX_ALIGNEDCODE_NUM_SYMBOLS, min(tablebits, LZX_ALIGNEDCODE_TABLEBITS), codes->lens.aligned, LZX_MAX_ALIGNED_CODEWORD_LEN)); #endif /* ENABLE_LZX_DEBUG */ } /* Write an LZX aligned offset or verbatim block to the output. */ static void lzx_write_compressed_block(int block_type, unsigned block_size, unsigned max_window_size, unsigned num_main_syms, struct lzx_match * chosen_matches, unsigned num_chosen_matches, const struct lzx_codes * codes, const struct lzx_codes * prev_codes, struct output_bitstream * ostream) { unsigned i; LZX_ASSERT(block_type == LZX_BLOCKTYPE_ALIGNED || block_type == LZX_BLOCKTYPE_VERBATIM); lzx_assert_codes_valid(codes, num_main_syms); /* The first three bits indicate the type of block and are one of the * LZX_BLOCKTYPE_* constants. */ bitstream_put_bits(ostream, block_type, 3); /* Output the block size. * * The original LZX format seemed to always encode the block size in 3 * bytes. However, the implementation in WIMGAPI, as used in WIM files, * uses the first bit to indicate whether the block is the default size * (32768) or a different size given explicitly by the next 16 bits. * * By default, this compressor uses a window size of 32768 and therefore * follows the WIMGAPI behavior. However, this compressor also supports * window sizes greater than 32768 bytes, which do not appear to be * supported by WIMGAPI. In such cases, we retain the default size bit * to mean a size of 32768 bytes but output non-default block size in 24 * bits rather than 16. The compatibility of this behavior is unknown * because WIMs created with chunk size greater than 32768 can seemingly * only be opened by wimlib anyway. */ if (block_size == LZX_DEFAULT_BLOCK_SIZE) { bitstream_put_bits(ostream, 1, 1); } else { bitstream_put_bits(ostream, 0, 1); if (max_window_size >= 65536) bitstream_put_bits(ostream, block_size >> 16, 8); bitstream_put_bits(ostream, block_size, 16); } /* Write out lengths of the main code. Note that the LZX specification * incorrectly states that the aligned offset code comes after the * length code, but in fact it is the very first code to be written * (before the main code). */ if (block_type == LZX_BLOCKTYPE_ALIGNED) for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) bitstream_put_bits(ostream, codes->lens.aligned[i], LZX_ALIGNEDCODE_ELEMENT_SIZE); LZX_DEBUG("Writing main code..."); /* Write the precode and lengths for the first LZX_NUM_CHARS symbols in * the main code, which are the codewords for literal bytes. */ lzx_write_compressed_code(ostream, codes->lens.main, prev_codes->lens.main, LZX_NUM_CHARS); /* Write the precode and lengths for the rest of the main code, which * are the codewords for match headers. */ lzx_write_compressed_code(ostream, codes->lens.main + LZX_NUM_CHARS, prev_codes->lens.main + LZX_NUM_CHARS, num_main_syms - LZX_NUM_CHARS); LZX_DEBUG("Writing length code..."); /* Write the precode and lengths for the length code. */ lzx_write_compressed_code(ostream, codes->lens.len, prev_codes->lens.len, LZX_LENCODE_NUM_SYMBOLS); LZX_DEBUG("Writing matches and literals..."); /* Write the actual matches and literals. */ lzx_write_matches_and_literals(ostream, block_type, chosen_matches, num_chosen_matches, codes); LZX_DEBUG("Done writing block."); } /* Write out the LZX blocks that were computed. */ static void lzx_write_all_blocks(struct lzx_compressor *ctx, struct output_bitstream *ostream) { const struct lzx_codes *prev_codes = &ctx->zero_codes; for (unsigned i = 0; i < ctx->num_blocks; i++) { const struct lzx_block_spec *spec = &ctx->block_specs[i]; LZX_DEBUG("Writing block %u/%u (type=%d, size=%u, num_chosen_matches=%u)...", i + 1, ctx->num_blocks, spec->block_type, spec->block_size, spec->num_chosen_matches); lzx_write_compressed_block(spec->block_type, spec->block_size, ctx->max_window_size, ctx->num_main_syms, &ctx->chosen_matches[spec->chosen_matches_start_pos], spec->num_chosen_matches, &spec->codes, prev_codes, ostream); prev_codes = &spec->codes; } } /* Constructs an LZX match from a literal byte and updates the main code symbol * frequencies. */ static u32 lzx_tally_literal(u8 lit, struct lzx_freqs *freqs) { freqs->main[lit]++; return (u32)lit; } /* Constructs an LZX match from an offset and a length, and updates the LRU * queue and the frequency of symbols in the main, length, and aligned offset * alphabets. The return value is a 32-bit number that provides the match in an * intermediate representation documented below. */ static u32 lzx_tally_match(unsigned match_len, unsigned match_offset, struct lzx_freqs *freqs, struct lzx_lru_queue *queue) { unsigned position_slot; unsigned position_footer; u32 len_header; unsigned main_symbol; unsigned len_footer; unsigned adjusted_match_len; LZX_ASSERT(match_len >= LZX_MIN_MATCH_LEN && match_len <= LZX_MAX_MATCH_LEN); /* The match offset shall be encoded as a position slot (itself encoded * as part of the main symbol) and a position footer. */ position_slot = lzx_get_position_slot(match_offset, queue); position_footer = (match_offset + LZX_OFFSET_OFFSET) & ((1U << lzx_get_num_extra_bits(position_slot)) - 1); /* The match length shall be encoded as a length header (itself encoded * as part of the main symbol) and an optional length footer. */ adjusted_match_len = match_len - LZX_MIN_MATCH_LEN; if (adjusted_match_len < LZX_NUM_PRIMARY_LENS) { /* No length footer needed. */ len_header = adjusted_match_len; } else { /* Length footer needed. It will be encoded using the length * code. */ len_header = LZX_NUM_PRIMARY_LENS; len_footer = adjusted_match_len - LZX_NUM_PRIMARY_LENS; freqs->len[len_footer]++; } /* Account for the main symbol. */ main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS; freqs->main[main_symbol]++; /* In an aligned offset block, 3 bits of the position footer are output * as an aligned offset symbol. Account for this, although we may * ultimately decide to output the block as verbatim. */ /* The following check is equivalent to: * * if (lzx_extra_bits[position_slot] >= 3) * * Note that this correctly excludes position slots that correspond to * recent offsets. */ if (position_slot >= 8) freqs->aligned[position_footer & 7]++; /* Pack the position slot, position footer, and match length into an * intermediate representation. See `struct lzx_match' for details. */ LZX_ASSERT(LZX_MAX_POSITION_SLOTS <= 64); LZX_ASSERT(lzx_get_num_extra_bits(LZX_MAX_POSITION_SLOTS - 1) <= 17); LZX_ASSERT(LZX_MAX_MATCH_LEN - LZX_MIN_MATCH_LEN + 1 <= 256); LZX_ASSERT(position_slot <= (1U << (31 - 25)) - 1); LZX_ASSERT(position_footer <= (1U << (25 - 8)) - 1); LZX_ASSERT(adjusted_match_len <= (1U << (8 - 0)) - 1); return 0x80000000 | (position_slot << 25) | (position_footer << 8) | (adjusted_match_len); } struct lzx_record_ctx { struct lzx_freqs freqs; struct lzx_lru_queue queue; struct lzx_match *matches; }; static void lzx_record_match(unsigned len, unsigned offset, void *_ctx) { struct lzx_record_ctx *ctx = _ctx; (ctx->matches++)->data = lzx_tally_match(len, offset, &ctx->freqs, &ctx->queue); } static void lzx_record_literal(u8 lit, void *_ctx) { struct lzx_record_ctx *ctx = _ctx; (ctx->matches++)->data = lzx_tally_literal(lit, &ctx->freqs); } /* Returns the cost, in bits, to output a literal byte using the specified cost * model. */ static unsigned lzx_literal_cost(u8 c, const struct lzx_costs * costs) { return costs->main[c]; } /* Given a (length, offset) pair that could be turned into a valid LZX match as * well as costs for the codewords in the main, length, and aligned Huffman * codes, return the approximate number of bits it will take to represent this * match in the compressed output. Take into account the match offset LRU * queue and optionally update it. */ static unsigned lzx_match_cost(unsigned length, unsigned offset, const struct lzx_costs *costs, struct lzx_lru_queue *queue) { unsigned position_slot; unsigned len_header, main_symbol; unsigned cost = 0; position_slot = lzx_get_position_slot(offset, queue); len_header = min(length - LZX_MIN_MATCH_LEN, LZX_NUM_PRIMARY_LENS); main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS; /* Account for main symbol. */ cost += costs->main[main_symbol]; /* Account for extra position information. */ unsigned num_extra_bits = lzx_get_num_extra_bits(position_slot); if (num_extra_bits >= 3) { cost += num_extra_bits - 3; cost += costs->aligned[(offset + LZX_OFFSET_OFFSET) & 7]; } else { cost += num_extra_bits; } /* Account for extra length information. */ if (len_header == LZX_NUM_PRIMARY_LENS) cost += costs->len[length - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS]; return cost; } /* Fast heuristic cost evaluation to use in the inner loop of the match-finder. * Unlike lzx_match_cost() which does a true cost evaluation, this simply * prioritize matches based on their offset. */ static input_idx_t lzx_match_cost_fast(input_idx_t length, input_idx_t offset, const void *_queue) { const struct lzx_lru_queue *queue = _queue; /* It seems well worth it to take the time to give priority to recently * used offsets. */ for (input_idx_t i = 0; i < LZX_NUM_RECENT_OFFSETS; i++) if (offset == queue->R[i]) return i; return offset; } /* Set the cost model @ctx->costs from the Huffman codeword lengths specified in * @lens. * * The cost model and codeword lengths are almost the same thing, but the * Huffman codewords with length 0 correspond to symbols with zero frequency * that still need to be assigned actual costs. The specific values assigned * are arbitrary, but they should be fairly high (near the maximum codeword * length) to take into account the fact that uses of these symbols are expected * to be rare. */ static void lzx_set_costs(struct lzx_compressor * ctx, const struct lzx_lens * lens) { unsigned i; unsigned num_main_syms = ctx->num_main_syms; /* Main code */ for (i = 0; i < num_main_syms; i++) { ctx->costs.main[i] = lens->main[i]; if (ctx->costs.main[i] == 0) ctx->costs.main[i] = ctx->params.alg_params.slow.main_nostat_cost; } /* Length code */ for (i = 0; i < LZX_LENCODE_NUM_SYMBOLS; i++) { ctx->costs.len[i] = lens->len[i]; if (ctx->costs.len[i] == 0) ctx->costs.len[i] = ctx->params.alg_params.slow.len_nostat_cost; } /* Aligned offset code */ for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) { ctx->costs.aligned[i] = lens->aligned[i]; if (ctx->costs.aligned[i] == 0) ctx->costs.aligned[i] = ctx->params.alg_params.slow.aligned_nostat_cost; } } /* Tell the match-finder to skip the specified number of bytes (@n) in the * input. */ static void lzx_lz_skip_bytes(struct lzx_compressor *ctx, input_idx_t n) { LZX_ASSERT(n <= ctx->match_window_end - ctx->match_window_pos); if (ctx->matches_cached) { ctx->match_window_pos += n; while (n--) { ctx->cached_matches_pos += ctx->cached_matches[ctx->cached_matches_pos].len + 1; } } else { while (n--) { ctx->cached_matches[ctx->cached_matches_pos++].len = 0; lz_sarray_skip_position(&ctx->lz_sarray); ctx->match_window_pos++; } LZX_ASSERT(lz_sarray_get_pos(&ctx->lz_sarray) == ctx->match_window_pos); } } /* Retrieve a list of matches available at the next position in the input. * * A pointer to the matches array is written into @matches_ret, and the return * value is the number of matches found. */ static u32 lzx_lz_get_matches_caching(struct lzx_compressor *ctx, const struct lzx_lru_queue *queue, struct raw_match **matches_ret) { u32 num_matches; struct raw_match *matches; LZX_ASSERT(ctx->match_window_pos <= ctx->match_window_end); matches = &ctx->cached_matches[ctx->cached_matches_pos + 1]; if (ctx->matches_cached) { num_matches = matches[-1].len; } else { LZX_ASSERT(lz_sarray_get_pos(&ctx->lz_sarray) == ctx->match_window_pos); num_matches = lz_sarray_get_matches(&ctx->lz_sarray, matches, lzx_match_cost_fast, queue); matches[-1].len = num_matches; } ctx->cached_matches_pos += num_matches + 1; *matches_ret = matches; /* Cap the length of returned matches to the number of bytes remaining, * if it is not the whole window. */ if (ctx->match_window_end < ctx->window_size) { unsigned maxlen = ctx->match_window_end - ctx->match_window_pos; for (u32 i = 0; i < num_matches; i++) if (matches[i].len > maxlen) matches[i].len = maxlen; } #if 0 fprintf(stderr, "Pos %u/%u: %u matches\n", ctx->match_window_pos, ctx->match_window_end, num_matches); for (unsigned i = 0; i < num_matches; i++) fprintf(stderr, "\tLen %u Offset %u\n", matches[i].len, matches[i].offset); #endif #ifdef ENABLE_LZX_DEBUG for (u32 i = 0; i < num_matches; i++) { LZX_ASSERT(matches[i].len >= LZX_MIN_MATCH_LEN); LZX_ASSERT(matches[i].len <= LZX_MAX_MATCH_LEN); LZX_ASSERT(matches[i].len <= ctx->match_window_end - ctx->match_window_pos); LZX_ASSERT(matches[i].offset > 0); LZX_ASSERT(matches[i].offset <= ctx->match_window_pos); LZX_ASSERT(!memcmp(&ctx->window[ctx->match_window_pos], &ctx->window[ctx->match_window_pos - matches[i].offset], matches[i].len)); } #endif ctx->match_window_pos++; return num_matches; } static u32 lzx_get_prev_literal_cost(struct lzx_compressor *ctx, struct lzx_lru_queue *queue) { return lzx_literal_cost(ctx->window[ctx->match_window_pos - 1], &ctx->costs); } static u32 lzx_get_match_cost(struct lzx_compressor *ctx, struct lzx_lru_queue *queue, input_idx_t length, input_idx_t offset) { return lzx_match_cost(length, offset, &ctx->costs, queue); } static struct raw_match lzx_lz_get_near_optimal_match(struct lzx_compressor *ctx) { return lz_get_near_optimal_match(&ctx->mc, lzx_lz_get_matches_caching, lzx_lz_skip_bytes, lzx_get_prev_literal_cost, lzx_get_match_cost, ctx, &ctx->queue); } /* Set default symbol costs for the LZX Huffman codes. */ static void lzx_set_default_costs(struct lzx_costs * costs, unsigned num_main_syms) { unsigned i; /* Main code (part 1): Literal symbols */ for (i = 0; i < LZX_NUM_CHARS; i++) costs->main[i] = 8; /* Main code (part 2): Match header symbols */ for (; i < num_main_syms; i++) costs->main[i] = 10; /* Length code */ for (i = 0; i < LZX_LENCODE_NUM_SYMBOLS; i++) costs->len[i] = 8; /* Aligned offset code */ for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) costs->aligned[i] = 3; } /* Given the frequencies of symbols in an LZX-compressed block and the * corresponding Huffman codes, return LZX_BLOCKTYPE_ALIGNED or * LZX_BLOCKTYPE_VERBATIM if an aligned offset or verbatim block, respectively, * will take fewer bits to output. */ static int lzx_choose_verbatim_or_aligned(const struct lzx_freqs * freqs, const struct lzx_codes * codes) { unsigned aligned_cost = 0; unsigned verbatim_cost = 0; /* Verbatim blocks have a constant 3 bits per position footer. Aligned * offset blocks have an aligned offset symbol per position footer, plus * an extra 24 bits per block to output the lengths necessary to * reconstruct the aligned offset code itself. */ for (unsigned i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) { verbatim_cost += 3 * freqs->aligned[i]; aligned_cost += codes->lens.aligned[i] * freqs->aligned[i]; } aligned_cost += LZX_ALIGNEDCODE_ELEMENT_SIZE * LZX_ALIGNEDCODE_NUM_SYMBOLS; if (aligned_cost < verbatim_cost) return LZX_BLOCKTYPE_ALIGNED; else return LZX_BLOCKTYPE_VERBATIM; } /* Find a near-optimal sequence of matches/literals with which to output the * specified LZX block, then set the block's type to that which has the minimum * cost to output (either verbatim or aligned). */ static void lzx_optimize_block(struct lzx_compressor *ctx, struct lzx_block_spec *spec, unsigned num_passes) { const struct lzx_lru_queue orig_queue = ctx->queue; struct lzx_freqs freqs; unsigned orig_window_pos = spec->window_pos; unsigned orig_cached_pos = ctx->cached_matches_pos; LZX_ASSERT(ctx->match_window_pos == spec->window_pos); ctx->match_window_end = spec->window_pos + spec->block_size; spec->chosen_matches_start_pos = spec->window_pos; LZX_ASSERT(num_passes >= 1); /* The first optimal parsing pass is done using the cost model already * set in ctx->costs. Each later pass is done using a cost model * computed from the previous pass. */ for (unsigned pass = 0; pass < num_passes; pass++) { ctx->match_window_pos = orig_window_pos; ctx->cached_matches_pos = orig_cached_pos; ctx->queue = orig_queue; spec->num_chosen_matches = 0; memset(&freqs, 0, sizeof(freqs)); for (unsigned i = spec->window_pos; i < spec->window_pos + spec->block_size; ) { struct raw_match raw_match; struct lzx_match lzx_match; raw_match = lzx_lz_get_near_optimal_match(ctx); if (raw_match.len >= LZX_MIN_MATCH_LEN) { if (unlikely(raw_match.len == LZX_MIN_MATCH_LEN && raw_match.offset == ctx->max_window_size - LZX_MIN_MATCH_LEN)) { /* Degenerate case where the parser * generated the minimum match length * with the maximum offset. There * aren't actually enough position slots * to represent this offset, as noted in * the comments in * lzx_get_num_main_syms(), so we cannot * allow it. Use literals instead. * * Note that this case only occurs if * the match-finder can generate matches * to the very start of the window. The * suffix array match-finder can, * although typical hash chain and * binary tree match-finders use 0 as a * null value and therefore cannot * generate such matches. */ BUILD_BUG_ON(LZX_MIN_MATCH_LEN != 2); lzx_match.data = lzx_tally_literal(ctx->window[i], &freqs); i += 1; ctx->chosen_matches[spec->chosen_matches_start_pos + spec->num_chosen_matches++] = lzx_match; lzx_match.data = lzx_tally_literal(ctx->window[i], &freqs); i += 1; } else { lzx_match.data = lzx_tally_match(raw_match.len, raw_match.offset, &freqs, &ctx->queue); i += raw_match.len; } } else { lzx_match.data = lzx_tally_literal(ctx->window[i], &freqs); i += 1; } ctx->chosen_matches[spec->chosen_matches_start_pos + spec->num_chosen_matches++] = lzx_match; } lzx_make_huffman_codes(&freqs, &spec->codes, ctx->num_main_syms); if (pass < num_passes - 1) lzx_set_costs(ctx, &spec->codes.lens); ctx->matches_cached = true; } spec->block_type = lzx_choose_verbatim_or_aligned(&freqs, &spec->codes); ctx->matches_cached = false; } static void lzx_optimize_blocks(struct lzx_compressor *ctx) { lzx_lru_queue_init(&ctx->queue); lz_match_chooser_begin(&ctx->mc); const unsigned num_passes = ctx->params.alg_params.slow.num_optim_passes; for (unsigned i = 0; i < ctx->num_blocks; i++) lzx_optimize_block(ctx, &ctx->block_specs[i], num_passes); } /* Prepare the input window into one or more LZX blocks ready to be output. */ static void lzx_prepare_blocks(struct lzx_compressor * ctx) { /* Initialize the match-finder. */ lz_sarray_load_window(&ctx->lz_sarray, ctx->window, ctx->window_size); ctx->cached_matches_pos = 0; ctx->matches_cached = false; ctx->match_window_pos = 0; /* Set up a default cost model. */ lzx_set_default_costs(&ctx->costs, ctx->num_main_syms); /* TODO: The compression ratio could be slightly improved by performing * data-dependent block splitting instead of using fixed-size blocks. * Doing so well is a computationally hard problem, however. */ ctx->num_blocks = DIV_ROUND_UP(ctx->window_size, LZX_DIV_BLOCK_SIZE); for (unsigned i = 0; i < ctx->num_blocks; i++) { unsigned pos = LZX_DIV_BLOCK_SIZE * i; ctx->block_specs[i].window_pos = pos; ctx->block_specs[i].block_size = min(ctx->window_size - pos, LZX_DIV_BLOCK_SIZE); } /* Determine sequence of matches/literals to output for each block. */ lzx_optimize_blocks(ctx); } /* * This is the fast version of lzx_prepare_blocks(). This version "quickly" * prepares a single compressed block containing the entire input. See the * description of the "Fast algorithm" at the beginning of this file for more * information. * * Input --- the preprocessed data: * * ctx->window[] * ctx->window_size * * Output --- the block specification and the corresponding match/literal data: * * ctx->block_specs[] * ctx->num_blocks * ctx->chosen_matches[] */ static void lzx_prepare_block_fast(struct lzx_compressor * ctx) { struct lzx_record_ctx record_ctx; struct lzx_block_spec *spec; /* Parameters to hash chain LZ match finder * (lazy with 1 match lookahead) */ static const struct lz_params lzx_lz_params = { /* Although LZX_MIN_MATCH_LEN == 2, length 2 matches typically * aren't worth choosing when using greedy or lazy parsing. */ .min_match = 3, .max_match = LZX_MAX_MATCH_LEN, .max_offset = LZX_MAX_WINDOW_SIZE, .good_match = LZX_MAX_MATCH_LEN, .nice_match = LZX_MAX_MATCH_LEN, .max_chain_len = LZX_MAX_MATCH_LEN, .max_lazy_match = LZX_MAX_MATCH_LEN, .too_far = 4096, }; /* Initialize symbol frequencies and match offset LRU queue. */ memset(&record_ctx.freqs, 0, sizeof(struct lzx_freqs)); lzx_lru_queue_init(&record_ctx.queue); record_ctx.matches = ctx->chosen_matches; /* Determine series of matches/literals to output. */ lz_analyze_block(ctx->window, ctx->window_size, lzx_record_match, lzx_record_literal, &record_ctx, &lzx_lz_params, ctx->prev_tab); /* Set up block specification. */ spec = &ctx->block_specs[0]; spec->block_type = LZX_BLOCKTYPE_ALIGNED; spec->window_pos = 0; spec->block_size = ctx->window_size; spec->num_chosen_matches = (record_ctx.matches - ctx->chosen_matches); spec->chosen_matches_start_pos = 0; lzx_make_huffman_codes(&record_ctx.freqs, &spec->codes, ctx->num_main_syms); ctx->num_blocks = 1; } static void do_call_insn_translation(u32 *call_insn_target, int input_pos, s32 file_size) { s32 abs_offset; s32 rel_offset; rel_offset = le32_to_cpu(*call_insn_target); if (rel_offset >= -input_pos && rel_offset < file_size) { if (rel_offset < file_size - input_pos) { /* "good translation" */ abs_offset = rel_offset + input_pos; } else { /* "compensating translation" */ abs_offset = rel_offset - file_size; } *call_insn_target = cpu_to_le32(abs_offset); } } /* This is the reverse of undo_call_insn_preprocessing() in lzx-decompress.c. * See the comment above that function for more information. */ static void do_call_insn_preprocessing(u8 data[], int size) { for (int i = 0; i < size - 10; i++) { if (data[i] == 0xe8) { do_call_insn_translation((u32*)&data[i + 1], i, LZX_WIM_MAGIC_FILESIZE); i += 4; } } } static size_t lzx_compress(const void *uncompressed_data, size_t uncompressed_size, void *compressed_data, size_t compressed_size_avail, void *_ctx) { struct lzx_compressor *ctx = _ctx; struct output_bitstream ostream; size_t compressed_size; if (uncompressed_size < 100) { LZX_DEBUG("Too small to bother compressing."); return 0; } if (uncompressed_size > ctx->max_window_size) { LZX_DEBUG("Can't compress %zu bytes using window of %u bytes!", uncompressed_size, ctx->max_window_size); return 0; } LZX_DEBUG("Attempting to compress %zu bytes...", uncompressed_size); /* The input data must be preprocessed. To avoid changing the original * input, copy it to a temporary buffer. */ memcpy(ctx->window, uncompressed_data, uncompressed_size); ctx->window_size = uncompressed_size; /* This line is unnecessary; it just avoids inconsequential accesses of * uninitialized memory that would show up in memory-checking tools such * as valgrind. */ memset(&ctx->window[ctx->window_size], 0, 12); LZX_DEBUG("Preprocessing data..."); /* Before doing any actual compression, do the call instruction (0xe8 * byte) translation on the uncompressed data. */ do_call_insn_preprocessing(ctx->window, ctx->window_size); LZX_DEBUG("Preparing blocks..."); /* Prepare the compressed data. */ if (ctx->params.algorithm == WIMLIB_LZX_ALGORITHM_FAST) lzx_prepare_block_fast(ctx); else lzx_prepare_blocks(ctx); LZX_DEBUG("Writing compressed blocks..."); /* Generate the compressed data. */ init_output_bitstream(&ostream, compressed_data, compressed_size_avail); lzx_write_all_blocks(ctx, &ostream); LZX_DEBUG("Flushing bitstream..."); compressed_size = flush_output_bitstream(&ostream); if (compressed_size == ~(input_idx_t)0) { LZX_DEBUG("Data did not compress to %zu bytes or less!", compressed_size_avail); return 0; } LZX_DEBUG("Done: compressed %zu => %zu bytes.", uncompressed_size, compressed_size); /* Verify that we really get the same thing back when decompressing. * Although this could be disabled by default in all cases, it only * takes around 2-3% of the running time of the slow algorithm to do the * verification. */ if (ctx->params.algorithm == WIMLIB_LZX_ALGORITHM_SLOW #if defined(ENABLE_LZX_DEBUG) || defined(ENABLE_VERIFY_COMPRESSION) || 1 #endif ) { struct wimlib_decompressor *decompressor; if (0 == wimlib_create_decompressor(WIMLIB_COMPRESSION_TYPE_LZX, ctx->max_window_size, NULL, &decompressor)) { int ret; ret = wimlib_decompress(compressed_data, compressed_size, ctx->window, uncompressed_size, decompressor); wimlib_free_decompressor(decompressor); if (ret) { ERROR("Failed to decompress data we " "compressed using LZX algorithm"); wimlib_assert(0); return 0; } if (memcmp(uncompressed_data, ctx->window, uncompressed_size)) { ERROR("Data we compressed using LZX algorithm " "didn't decompress to original"); wimlib_assert(0); return 0; } } else { WARNING("Failed to create decompressor for " "data verification!"); } } return compressed_size; } static void lzx_free_compressor(void *_ctx) { struct lzx_compressor *ctx = _ctx; if (ctx) { FREE(ctx->chosen_matches); FREE(ctx->cached_matches); lz_match_chooser_destroy(&ctx->mc); lz_sarray_destroy(&ctx->lz_sarray); FREE(ctx->block_specs); FREE(ctx->prev_tab); FREE(ctx->window); FREE(ctx); } } static const struct wimlib_lzx_compressor_params lzx_fast_default = { .hdr = { .size = sizeof(struct wimlib_lzx_compressor_params), }, .algorithm = WIMLIB_LZX_ALGORITHM_FAST, .use_defaults = 0, .alg_params = { .fast = { }, }, }; static const struct wimlib_lzx_compressor_params lzx_slow_default = { .hdr = { .size = sizeof(struct wimlib_lzx_compressor_params), }, .algorithm = WIMLIB_LZX_ALGORITHM_SLOW, .use_defaults = 0, .alg_params = { .slow = { .use_len2_matches = 1, .nice_match_length = 32, .num_optim_passes = 2, .max_search_depth = 50, .max_matches_per_pos = 3, .main_nostat_cost = 15, .len_nostat_cost = 15, .aligned_nostat_cost = 7, }, }, }; static const struct wimlib_lzx_compressor_params * lzx_get_params(const struct wimlib_compressor_params_header *_params) { const struct wimlib_lzx_compressor_params *params = (const struct wimlib_lzx_compressor_params*)_params; if (params == NULL) { LZX_DEBUG("Using default algorithm and parameters."); params = &lzx_slow_default; } else { if (params->use_defaults) { if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) params = &lzx_slow_default; else params = &lzx_fast_default; } } return params; } static int lzx_create_compressor(size_t window_size, const struct wimlib_compressor_params_header *_params, void **ctx_ret) { const struct wimlib_lzx_compressor_params *params = lzx_get_params(_params); struct lzx_compressor *ctx; LZX_DEBUG("Allocating LZX context..."); if (!lzx_window_size_valid(window_size)) return WIMLIB_ERR_INVALID_PARAM; LZX_DEBUG("Allocating memory."); ctx = CALLOC(1, sizeof(struct lzx_compressor)); if (ctx == NULL) goto oom; ctx->num_main_syms = lzx_get_num_main_syms(window_size); ctx->max_window_size = window_size; ctx->window = MALLOC(window_size + 12); if (ctx->window == NULL) goto oom; if (params->algorithm == WIMLIB_LZX_ALGORITHM_FAST) { ctx->prev_tab = MALLOC(window_size * sizeof(ctx->prev_tab[0])); if (ctx->prev_tab == NULL) goto oom; } size_t block_specs_length = DIV_ROUND_UP(window_size, LZX_DIV_BLOCK_SIZE); ctx->block_specs = MALLOC(block_specs_length * sizeof(ctx->block_specs[0])); if (ctx->block_specs == NULL) goto oom; if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { unsigned min_match_len = LZX_MIN_MATCH_LEN; if (!params->alg_params.slow.use_len2_matches) min_match_len = max(min_match_len, 3); if (!lz_sarray_init(&ctx->lz_sarray, window_size, min_match_len, LZX_MAX_MATCH_LEN, params->alg_params.slow.max_search_depth, params->alg_params.slow.max_matches_per_pos)) goto oom; } if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { if (!lz_match_chooser_init(&ctx->mc, LZX_OPTIM_ARRAY_SIZE, params->alg_params.slow.nice_match_length, LZX_MAX_MATCH_LEN)) goto oom; } if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { u32 cache_per_pos; cache_per_pos = params->alg_params.slow.max_matches_per_pos; if (cache_per_pos > LZX_MAX_CACHE_PER_POS) cache_per_pos = LZX_MAX_CACHE_PER_POS; ctx->cached_matches = MALLOC(window_size * (cache_per_pos + 1) * sizeof(ctx->cached_matches[0])); if (ctx->cached_matches == NULL) goto oom; } ctx->chosen_matches = MALLOC(window_size * sizeof(ctx->chosen_matches[0])); if (ctx->chosen_matches == NULL) goto oom; memcpy(&ctx->params, params, sizeof(struct wimlib_lzx_compressor_params)); memset(&ctx->zero_codes, 0, sizeof(ctx->zero_codes)); LZX_DEBUG("Successfully allocated new LZX context."); *ctx_ret = ctx; return 0; oom: lzx_free_compressor(ctx); return WIMLIB_ERR_NOMEM; } static u64 lzx_get_needed_memory(size_t max_block_size, const struct wimlib_compressor_params_header *_params) { const struct wimlib_lzx_compressor_params *params = lzx_get_params(_params); u64 size = 0; size += sizeof(struct lzx_compressor); size += max_block_size + 12; size += DIV_ROUND_UP(max_block_size, LZX_DIV_BLOCK_SIZE) * sizeof(((struct lzx_compressor*)0)->block_specs[0]); if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { size += max_block_size * sizeof(((struct lzx_compressor*)0)->chosen_matches[0]); size += lz_sarray_get_needed_memory(max_block_size); size += lz_match_chooser_get_needed_memory(LZX_OPTIM_ARRAY_SIZE, params->alg_params.slow.nice_match_length, LZX_MAX_MATCH_LEN); u32 cache_per_pos; cache_per_pos = params->alg_params.slow.max_matches_per_pos; if (cache_per_pos > LZX_MAX_CACHE_PER_POS) cache_per_pos = LZX_MAX_CACHE_PER_POS; size += max_block_size * (cache_per_pos + 1) * sizeof(((struct lzx_compressor*)0)->cached_matches[0]); } else { size += max_block_size * sizeof(((struct lzx_compressor*)0)->prev_tab[0]); } return size; } static bool lzx_params_valid(const struct wimlib_compressor_params_header *_params) { const struct wimlib_lzx_compressor_params *params = (const struct wimlib_lzx_compressor_params*)_params; if (params->hdr.size != sizeof(struct wimlib_lzx_compressor_params)) { LZX_DEBUG("Invalid parameter structure size!"); return false; } if (params->algorithm != WIMLIB_LZX_ALGORITHM_SLOW && params->algorithm != WIMLIB_LZX_ALGORITHM_FAST) { LZX_DEBUG("Invalid algorithm."); return false; } if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW && !params->use_defaults) { if (params->alg_params.slow.num_optim_passes < 1) { LZX_DEBUG("Invalid number of optimization passes!"); return false; } if (params->alg_params.slow.main_nostat_cost < 1 || params->alg_params.slow.main_nostat_cost > 16) { LZX_DEBUG("Invalid main_nostat_cost!"); return false; } if (params->alg_params.slow.len_nostat_cost < 1 || params->alg_params.slow.len_nostat_cost > 16) { LZX_DEBUG("Invalid len_nostat_cost!"); return false; } if (params->alg_params.slow.aligned_nostat_cost < 1 || params->alg_params.slow.aligned_nostat_cost > 8) { LZX_DEBUG("Invalid aligned_nostat_cost!"); return false; } } return true; } const struct compressor_ops lzx_compressor_ops = { .params_valid = lzx_params_valid, .get_needed_memory = lzx_get_needed_memory, .create_compressor = lzx_create_compressor, .compress = lzx_compress, .free_compressor = lzx_free_compressor, };