X-Git-Url: https://wimlib.net/git/?p=wimlib;a=blobdiff_plain;f=src%2Flzx-compress.c;h=c72fd460c84d47a4612fde0214499acad1d17f5c;hp=1bc107ff3f96c80fd544cd5b9873220aaf39b348;hb=69bf8e6b27c11c8dfb0e9794ea43c3b8af72ee38;hpb=9e56d04309e3e6a896319225288f0c86bd36d34e diff --git a/src/lzx-compress.c b/src/lzx-compress.c index 1bc107ff..c72fd460 100644 --- a/src/lzx-compress.c +++ b/src/lzx-compress.c @@ -1,12 +1,10 @@ /* * lzx-compress.c * - * LZX compression routines, originally based on code written by Matthew T. - * Russotto (liblzxcomp), but heavily modified. + * LZX compression routines */ /* - * Copyright (C) 2002 Matthew T. Russotto * Copyright (C) 2012, 2013 Eric Biggers * * This file is part of wimlib, a library for working with WIM files. @@ -27,247 +25,580 @@ /* - * This file provides lzx_compress(), a function to compress an in-memory buffer - * of data using LZX compression, as used in the WIM file format. - * - * Please see the comments in lzx-decompress.c for more information about this - * compression format. - * - * One thing to keep in mind is that there is no sliding window, since the - * window is always the entirety of a WIM chunk, which is at most WIM_CHUNK_SIZE - * ( = 32768) bytes. - * - * The basic compression algorithm used here should be familiar if you are - * familiar with Huffman trees and with other LZ77 and Huffman-based formats - * such as DEFLATE. Otherwise it can be quite tricky to understand. Basically - * it is the following: - * - * - Preprocess the input data (LZX-specific) - * - Go through the input data and determine matches. This part is based on - * code from zlib, and a hash table of 3-character strings is used to - * accelerate the process of finding matches. - * - Build the Huffman trees based on the frequencies of symbols determined - * while recording matches. - * - Output the block header, including the Huffman trees; then output the - * compressed stream of matches and literal characters. - * - * It is possible for a WIM chunk to include multiple LZX blocks, since for some - * input data this will produce a better compression ratio (especially since - * each block can include new Huffman codes). However, producing multiple LZX - * blocks from one input chunk is not yet implemented. + * 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, instead using 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. + * + * API + * === + * + * The old API (retained for backward compatibility) consists of just one + * function: + * + * wimlib_lzx_compress() + * + * The new compressor has more potential parameters and needs more memory, so + * the new API ties up memory allocations and compression parameters into a + * context: + * + * wimlib_lzx_alloc_context() + * wimlib_lzx_compress2() + * wimlib_lzx_free_context() + * wimlib_lzx_set_default_params() + * + * Both wimlib_lzx_compress() and wimlib_lzx_compress2() are designed to + * compress an in-memory buffer of up to the window size, which can be any power + * of two between 2^15 and 2^21 inclusively. However, by default, the WIM + * format uses 2^15, and this is seemingly the only value that is compatible + * with WIMGAPI. In any case, the window is not a true "sliding window" since + * no data is ever "slid out" of the window. This is needed for the WIM format, + * which is designed such that chunks may be randomly accessed. + * + * Both wimlib_lzx_compress() and wimlib_lzx_compress2() return 0 if the data + * could not be compressed to less than the size of the uncompressed data. + * Again, this is suitable for the WIM format, which stores such data chunks + * uncompressed. + * + * The functions in this LZX compression API are exported from the library, + * although with the possible exception of wimlib_lzx_set_default_params(), this + * is only in case other programs happen to have uses for it other than WIM + * reading/writing as already handled through the rest of the library. + * + * 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. */ -#include "lzx.h" -#include "compress.h" -#include +#ifdef HAVE_CONFIG_H +# include "config.h" +#endif + +#include "wimlib.h" +#include "wimlib/compress.h" +#include "wimlib/endianness.h" +#include "wimlib/error.h" +#include "wimlib/lzx.h" +#include "wimlib/util.h" +#include +#include #include +#ifdef ENABLE_LZX_DEBUG +# include "wimlib/decompress.h" +#endif + +#include "divsufsort/divsufsort.h" -/* Structure to contain the Huffman codes for the main, length, and aligned - * offset trees. */ -struct lzx_codes { - u16 main_codewords[LZX_MAINTREE_NUM_SYMBOLS]; - u8 main_lens[LZX_MAINTREE_NUM_SYMBOLS]; +typedef u32 block_cost_t; +#define INFINITE_BLOCK_COST ((block_cost_t)~0U) + +#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]; +}; - u16 len_codewords[LZX_LENTREE_NUM_SYMBOLS]; - u8 len_lens[LZX_LENTREE_NUM_SYMBOLS]; +/* The LZX main, length, and aligned offset Huffman codes */ +struct lzx_codes { + struct lzx_codewords codewords; + struct lzx_lens lens; +}; - u16 aligned_codewords[LZX_ALIGNEDTREE_NUM_SYMBOLS]; - u8 aligned_lens[LZX_ALIGNEDTREE_NUM_SYMBOLS]; +/* 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]; }; -struct lzx_freq_tables { - freq_t main_freq_table[LZX_MAINTREE_NUM_SYMBOLS]; - freq_t len_freq_table[LZX_LENTREE_NUM_SYMBOLS]; - freq_t aligned_freq_table[LZX_ALIGNEDTREE_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; }; -/* Returns the LZX position slot that corresponds to a given formatted offset. +/* Raw LZ match/literal format: just a length and offset. * - * Logically, this returns the smallest i such that - * formatted_offset >= lzx_position_base[i]. + * The length is the number of bytes of the match, and the offset is the number + * of bytes back in the input the match is from the current position. * - * The actual implementation below takes advantage of the regularity of the - * numbers in the lzx_position_base array to calculate the slot directly from - * the formatted offset without actually looking at the array. - */ -static inline unsigned lzx_get_position_slot(unsigned formatted_offset) -{ -#if 0 - /* - * Slots 36-49 (formatted_offset >= 262144) can be found by - * (formatted_offset/131072) + 34 == (formatted_offset >> 17) + 34; - * however, this check for formatted_offset >= 262144 is commented out - * because WIM chunks cannot be that large. - */ - if (formatted_offset >= 262144) { - return (formatted_offset >> 17) + 34; - } else -#endif - { - /* Note: this part here only works if: - * - * 2 <= formatted_offset < 655360 - * - * It is < 655360 because the frequency of the position bases - * increases starting at the 655360 entry, and it is >= 2 - * because the below calculation fails if the most significant - * bit is lower than the 2's place. */ - wimlib_assert(formatted_offset >= 2 && formatted_offset < 655360); - unsigned mssb_idx = bsr32(formatted_offset); - return (mssb_idx << 1) | - ((formatted_offset >> (mssb_idx - 1)) & 1); - } -} + * If @len < LZX_MIN_MATCH_LEN, then it's really just a literal byte and @offset is + * meaningless. */ +struct raw_match { + u16 len; + input_idx_t offset; +}; -static u32 lzx_record_literal(u8 literal, void *__main_freq_tab) -{ - freq_t *main_freq_tab = __main_freq_tab; - main_freq_tab[literal]++; - return literal; -} +/* Specification for an LZX block. */ +struct lzx_block_spec { -/* Constructs a 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_record_match(unsigned match_offset, unsigned match_len, - void *__freq_tabs, void *__queue) -{ - struct lzx_freq_tables *freq_tabs = __freq_tabs; - struct lru_queue *queue = __queue; - unsigned position_slot; - unsigned position_footer = 0; - u32 match; - u32 len_header; - u32 len_pos_header; - unsigned len_footer; - unsigned adjusted_match_len; + /* One of the LZX_BLOCKTYPE_* constants indicating which type of this + * block. */ + int block_type; - wimlib_assert(match_len >= LZX_MIN_MATCH && match_len <= LZX_MAX_MATCH); - wimlib_assert(match_offset != 0); - - /* If possible, encode this offset as a repeated offset. */ - if (match_offset == queue->R0) { - position_slot = 0; - } else if (match_offset == queue->R1) { - swap(queue->R0, queue->R1); - position_slot = 1; - } else if (match_offset == queue->R2) { - swap(queue->R0, queue->R2); - position_slot = 2; - } else { - /* Not a repeated offset. */ + /* 0-based position in the window at which this block starts. */ + input_idx_t window_pos; - /* offsets of 0, 1, and 2 are reserved for the repeated offset - * codes, so non-repeated offsets must be encoded as 3+. The - * minimum offset is 1, so encode the offsets offset by 2. */ - unsigned formatted_offset = match_offset + LZX_MIN_MATCH; + /* The number of bytes of uncompressed data this block represents. */ + input_idx_t block_size; - queue->R2 = queue->R1; - queue->R1 = queue->R0; - queue->R0 = match_offset; + /* 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 (now-formatted) offset will actually be encoded as a - * small position slot number that maps to a certain hard-coded - * offset (position base), followed by a number of extra bits--- - * the position footer--- that are added to the position base to - * get the original formatted offset. */ + /* The number of match/literal specifications for this block. */ + input_idx_t num_chosen_matches; - position_slot = lzx_get_position_slot(formatted_offset); - position_footer = formatted_offset & - ((1 << lzx_get_num_extra_bits(position_slot)) - 1); - } + /* Huffman codes for this block. */ + struct lzx_codes codes; +}; + +/* + * An array of these structures is used during the match-choosing algorithm. + * They correspond to consecutive positions in the window and are used to keep + * track of the cost to reach each position, and the match/literal choices that + * need to be chosen to reach that position. + */ +struct lzx_optimal { + /* The approximate minimum cost, in bits, to reach this position in the + * window which has been found so far. */ + block_cost_t cost; + + /* The union here is just for clarity, since the fields are used in two + * slightly different ways. Initially, the @prev structure is filled in + * first, and links go from later in the window to earlier in the + * window. Later, @next structure is filled in and links go from + * earlier in the window to later in the window. */ + union { + struct { + /* Position of the start of the match or literal that + * was taken to get to this position in the approximate + * minimum-cost parse. */ + input_idx_t link; + + /* Offset (as in an LZ (length, offset) pair) of the + * match or literal that was taken to get to this + * position in the approximate minimum-cost parse. */ + input_idx_t match_offset; + } prev; + struct { + /* Position at which the match or literal starting at + * this position ends in the minimum-cost parse. */ + input_idx_t link; + + /* Offset (as in an LZ (length, offset) pair) of the + * match or literal starting at this position in the + * approximate minimum-cost parse. */ + input_idx_t match_offset; + } next; + }; + + /* The match offset LRU queue that will exist when the approximate + * minimum-cost path to reach this position is taken. */ + struct lzx_lru_queue queue; +}; - adjusted_match_len = match_len - LZX_MIN_MATCH; +/* Suffix array link */ +struct salink { + /* Rank of highest ranked suffix that has rank lower than the suffix + * corresponding to this structure and either has a lower position + * (initially) or has a position lower than the highest position at + * which matches have been searched for so far, or -1 if there is no + * such suffix. */ + input_idx_t prev; + + /* Rank of lowest ranked suffix that has rank greater than the suffix + * corresponding to this structure and either has a lower position + * (intially) or has a position lower than the highest position at which + * matches have been searched for so far, or -1 if there is no such + * suffix. */ + input_idx_t next; + + /* Length of longest common prefix between the suffix corresponding to + * this structure and the suffix with rank @prev, or 0 if @prev is -1. + */ + input_idx_t lcpprev; - /* Pack the position slot, position footer, and match length into an - * intermediate representation. + /* Length of longest common prefix between the suffix corresponding to + * this structure and the suffix with rank @next, or 0 if @next is -1. + */ + input_idx_t lcpnext; +}; + +/* State of the LZX compressor. */ +struct lzx_compressor { + + /* The parameters that were used to create the compressor. */ + struct wimlib_lzx_params params; + + /* The buffer of data to be compressed. * - * bits description - * ---- ----------------------------------------------------------- + * 0xe8 byte preprocessing is done directly on the data here before + * further compression. * - * 31 1 if a match, 0 if a literal. + * 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. * - * 30-25 position slot. This can be at most 50, so it will fit in 6 - * bits. + * We reserve a few extra bytes to potentially allow reading off the end + * of the array in the match-finding code for optimization purposes. + */ + 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; + + /* Suffix array for window. + * This is a mapping from suffix rank to suffix position. */ + input_idx_t *SA; + + /* Inverse suffix array for window. + * This is a mapping from suffix position to suffix rank. + * If 0 <= r < window_size, then ISA[SA[r]] == r. */ + input_idx_t *ISA; + + /* Longest common prefix array corresponding to the suffix array SA. + * LCP[i] is the length of the longest common prefix between the + * suffixes with positions SA[i - 1] and SA[i]. LCP[0] is undefined. + */ + input_idx_t *LCP; + + /* Suffix array links. * - * 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_NUM_POSITION_SLOTS - 1] is 17). + * During a linear scan of the input string to find matches, this array + * used to keep track of which rank suffixes in the suffix array appear + * before the current position. Instead of searching in the original + * suffix array, scans for matches at a given position traverse a linked + * list containing only suffixes that appear before that position. */ + struct salink *salink; + + /* 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; + + /* Slow algorithm only: Temporary space used for match-choosing + * algorithm. * - * 0-7 length of match, offset by 2. This can be at most - * (LZX_MAX_MATCH - 2) == 255, so it will fit in 8 bits. */ - match = 0x80000000 | - (position_slot << 25) | - (position_footer << 8) | - (adjusted_match_len); + * The size of this array must be at least LZX_MAX_MATCH_LEN but + * otherwise is arbitrary. More space simply allows the match-choosing + * algorithm to potentially find better matches (depending on the input, + * as always). */ + struct lzx_optimal *optimum; - /* The match length must be at least 2, so let the adjusted match length - * be the match length minus 2. + /* Slow algorithm only: Variables used by the match-choosing algorithm. * - * If it is less than 7, the adjusted match length is encoded as a 3-bit - * number offset by 2. Otherwise, the 3-bit length header is all 1's - * and the actual adjusted length is given as a symbol encoded with the - * length tree, offset by 7. - */ - if (adjusted_match_len < LZX_NUM_PRIMARY_LENS) { - len_header = adjusted_match_len; - } else { - len_header = LZX_NUM_PRIMARY_LENS; - len_footer = adjusted_match_len - LZX_NUM_PRIMARY_LENS; - freq_tabs->len_freq_table[len_footer]++; + * When matches have been chosen, optimum_cur_idx is set to the position + * in the window of the next match/literal to return and optimum_end_idx + * is set to the position in the window at the end of the last + * match/literal to return. */ + u32 optimum_cur_idx; + u32 optimum_end_idx; +}; + +/* 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; + } } - len_pos_header = (position_slot << 3) | len_header; - wimlib_assert(len_pos_header < LZX_MAINTREE_NUM_SYMBOLS - LZX_NUM_CHARS); + /* The offset was not recently used; look up its real position slot. */ + position_slot = lzx_get_position_slot_raw(offset + LZX_OFFSET_OFFSET); - freq_tabs->main_freq_table[len_pos_header + LZX_NUM_CHARS]++; + /* 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; - /* Equivalent to: - * if (lzx_extra_bits[position_slot] >= 3) */ - if (position_slot >= 8) - freq_tabs->aligned_freq_table[position_footer & 7]++; + return position_slot; +} - return match; +/* 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); } /* - * Writes a compressed literal match to the output. + * Output an LZX match. * - * @out: The output bitstream. - * @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM) - * @match: The match, encoded as a 32-bit number. - * @codes: Pointer to a structure that contains the codewords for the - * main, length, and aligned offset Huffman codes. + * @out: The bitstream to write the match to. + * @block_type: The type of the LZX block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM) + * @match: The match. + * @codes: Pointer to a structure that contains the codewords for the + * main, length, and aligned offset Huffman codes. */ -static int lzx_write_match(struct output_bitstream *out, int block_type, - u32 match, const struct lzx_codes *codes) +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 & 0xff; + unsigned match_len_minus_2 = match.data & 0xff; /* Next 17 bits are the position footer */ - unsigned position_footer = (match >> 8) & 0x1ffff; /* 17 bits */ + unsigned position_footer = (match.data >> 8) & 0x1ffff; /* 17 bits */ /* Next 6 bits are the position slot. */ - unsigned position_slot = (match >> 25) & 0x3f; /* 6 bits */ + unsigned position_slot = (match.data >> 25) & 0x3f; /* 6 bits */ unsigned len_header; unsigned len_footer; - unsigned len_pos_header; unsigned main_symbol; unsigned num_extra_bits; unsigned verbatim_bits; unsigned aligned_bits; - int ret; - /* If the match length is less than MIN_MATCH (= 2) + + /* 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, and there is no + * 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. */ + * 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 @@ -278,143 +609,60 @@ static int lzx_write_match(struct output_bitstream *out, int block_type, 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 - * tree. */ - len_pos_header = (position_slot << 3) | len_header; - - /* 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 = len_pos_header + LZX_NUM_CHARS; + /* 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. */ - ret = bitstream_put_bits(out, codes->main_codewords[main_symbol], - codes->main_lens[main_symbol]); - if (ret != 0) - return ret; + 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)) { - ret = bitstream_put_bits(out, codes->len_codewords[len_footer], - codes->len_lens[len_footer]); - if (ret != 0) - return ret; + bitstream_put_bits(out, codes->codewords.len[len_footer], + codes->lens.len[len_footer]); } - wimlib_assert(position_slot < LZX_NUM_POSITION_SLOTS); - 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 tree. Otherwise, only the verbatim bits need to be + * 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; - ret = bitstream_put_bits(out, verbatim_bits, - num_extra_bits - 3); - if (ret != 0) - return ret; + bitstream_put_bits(out, verbatim_bits, + num_extra_bits - 3); aligned_bits = (position_footer & 7); - ret = bitstream_put_bits(out, - codes->aligned_codewords[aligned_bits], - codes->aligned_lens[aligned_bits]); - if (ret != 0) - return ret; + 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. */ - ret = bitstream_put_bits(out, position_footer, num_extra_bits); - if (ret != 0) - return ret; + bitstream_put_bits(out, position_footer, num_extra_bits); } - return 0; } -/* - * Writes all compressed literals in a block, both matches and literal bytes, to - * the output bitstream. - * - * @out: The output bitstream. - * @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM) - * @match_tab[]: The array of matches that will be output. It has length - * of @num_compressed_literals. - * @num_compressed_literals: Number of compressed literals to be output. - * @codes: Pointer to a structure that contains the codewords for the - * main, length, and aligned offset Huffman codes. - */ -static int lzx_write_compressed_literals(struct output_bitstream *ostream, - int block_type, - const u32 match_tab[], - unsigned num_compressed_literals, - const struct lzx_codes *codes) +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) { - unsigned i; - u32 match; - int ret; - - for (i = 0; i < num_compressed_literals; i++) { - match = match_tab[i]; - - /* High bit of the match indicates whether the match is an - * actual match (1) or a literal uncompressed byte (0) */ - if (match & 0x80000000) { - /* match */ - ret = lzx_write_match(ostream, block_type, match, - codes); - if (ret != 0) - return ret; - } else { - /* literal byte */ - wimlib_assert(match < LZX_NUM_CHARS); - ret = bitstream_put_bits(ostream, - codes->main_codewords[match], - codes->main_lens[match]); - if (ret != 0) - return ret; - } - } - return 0; -} - -/* - * Writes a compressed Huffman tree to the output, preceded by the pretree for - * it. - * - * The Huffman tree is represented in the output as a series of path lengths - * from which the canonical Huffman code can be reconstructed. The path lengths - * themselves are compressed using a separate Huffman code, the pretree, which - * consists of LZX_PRETREE_NUM_SYMBOLS (= 20) symbols that cover all possible code - * lengths, plus extra codes for repeated lengths. The path lengths of the - * pretree precede the path lengths of the larger code and are uncompressed, - * consisting of 20 entries of 4 bits each. - * - * @out: The bitstream for the compressed output. - * @lens: The code lengths for the Huffman tree, indexed by symbol. - * @num_symbols: The number of symbols in the code. - */ -static int lzx_write_compressed_tree(struct output_bitstream *out, - const u8 lens[], unsigned num_symbols) -{ - /* Frequencies of the length symbols, including the RLE symbols (NOT the - * actual lengths themselves). */ - freq_t pretree_freqs[LZX_PRETREE_NUM_SYMBOLS]; - u8 pretree_lens[LZX_PRETREE_NUM_SYMBOLS]; - u16 pretree_codewords[LZX_PRETREE_NUM_SYMBOLS]; - u8 output_syms[num_symbols * 2]; - unsigned output_syms_idx; - unsigned cur_run_len; - unsigned i; - unsigned len_in_run; - unsigned additional_bits; - char delta; - u8 pretree_sym; - - ZERO_ARRAY(pretree_freqs); + 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 @@ -423,16 +671,16 @@ static int lzx_write_compressed_tree(struct output_bitstream *out, * literally. * * output_syms[] will be filled in with the length symbols that will be - * output, including RLE codes, not yet encoded using the pre-tree. + * 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. - */ - output_syms_idx = 0; - cur_run_len = 1; - for (i = 1; i <= num_symbols; i++) { + * 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_symbols && lens[i] == lens[i - 1]) { + if (i != num_syms && lens[i] == lens[i - 1]) { /* Still in a run--- keep going. */ cur_run_len++; continue; @@ -443,7 +691,7 @@ static int lzx_write_compressed_tree(struct output_bitstream *out, /* The symbol that was repeated in the run--- not to be confused * with the length *of* the run (cur_run_len) */ - len_in_run = lens[i - 1]; + unsigned len_in_run = lens[i - 1]; if (len_in_run == 0) { /* A run of 0's. Encode it in as few length @@ -453,9 +701,11 @@ static int lzx_write_compressed_tree(struct output_bitstream *out, * 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); - pretree_freqs[18]++; + 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; @@ -465,8 +715,11 @@ static int lzx_write_compressed_tree(struct output_bitstream *out, * 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); - pretree_freqs[17]++; + 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; @@ -480,19 +733,24 @@ static int lzx_write_compressed_tree(struct output_bitstream *out, * 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 pretree, that follows the literal bit. + * 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 tree. + * in the run in the previous code. * */ while (cur_run_len >= 4) { + unsigned additional_bits; + signed char delta; + additional_bits = (cur_run_len > 4); - delta = -(char)len_in_run; + num_additional_bits += 1; + delta = (signed char)prev_lens[i - cur_run_len] - + (signed char)len_in_run; if (delta < 0) delta += 17; - pretree_freqs[19]++; - pretree_freqs[(unsigned char)delta]++; + 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; @@ -502,42 +760,91 @@ static int lzx_write_compressed_tree(struct output_bitstream *out, /* Any remaining lengths in the run are outputted without RLE, * as a difference from the length of that codeword in the - * previous tree. */ - while (cur_run_len--) { - delta = -(char)len_in_run; + * 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; - pretree_freqs[(unsigned char)delta]++; + precode_freqs[(unsigned char)delta]++; output_syms[output_syms_idx++] = delta; + cur_run_len--; } cur_run_len = 1; } - wimlib_assert(output_syms_idx < ARRAY_LEN(output_syms)); - - /* Build the pretree from the frequencies of the length symbols. */ + /* Build the precode from the frequencies of the length symbols. */ - make_canonical_huffman_code(LZX_PRETREE_NUM_SYMBOLS, - LZX_MAX_CODEWORD_LEN, - pretree_freqs, pretree_lens, - pretree_codewords); + make_canonical_huffman_code(LZX_PRECODE_NUM_SYMBOLS, + LZX_MAX_PRE_CODEWORD_LEN, + precode_freqs, precode_lens, + precode_codewords); - /* Write the lengths of the pretree codes to the output. */ - for (i = 0; i < LZX_PRETREE_NUM_SYMBOLS; i++) - bitstream_put_bits(out, pretree_lens[i], - LZX_PRETREE_ELEMENT_SIZE); + *num_additional_bits_ret = num_additional_bits; - /* Write the length symbols, encoded with the pretree, to the output. */ - - i = 0; - while (i < output_syms_idx) { - pretree_sym = output_syms[i++]; + return output_syms_idx; +} - bitstream_put_bits(out, pretree_codewords[pretree_sym], - pretree_lens[pretree_sym]); - switch (pretree_sym) { +/* + * Writes a compressed Huffman code to the output, preceded by the precode for + * it. + * + * The Huffman code is represented in the output as a series of path lengths + * from which the canonical Huffman code can be reconstructed. The path lengths + * themselves are compressed using a separate Huffman code, the precode, which + * consists of LZX_PRECODE_NUM_SYMBOLS (= 20) symbols that cover all possible + * code lengths, plus extra codes for repeated lengths. The path lengths of the + * precode precede the path lengths of the larger code and are uncompressed, + * consisting of 20 entries of 4 bits each. + * + * @out: Bitstream to write the code to. + * @lens: The code lengths for the Huffman code, indexed by symbol. + * @prev_lens: Code lengths for this Huffman code, indexed by symbol, + * in the *previous block*, or all zeroes if this is the + * first block. + * @num_syms: The number of symbols in the 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; @@ -547,227 +854,1720 @@ static int lzx_write_compressed_tree(struct output_bitstream *out, case 19: bitstream_put_bits(out, output_syms[i++], 1); bitstream_put_bits(out, - pretree_codewords[output_syms[i]], - pretree_lens[output_syms[i]]); + precode_codewords[output_syms[i]], + precode_lens[output_syms[i]]); i++; break; default: break; } } - return 0; } -/* Builds the canonical Huffman code for the main tree, the length tree, and the - * aligned offset tree. */ -static void lzx_make_huffman_codes(const struct lzx_freq_tables *freq_tabs, - struct lzx_codes *codes) -{ - make_canonical_huffman_code(LZX_MAINTREE_NUM_SYMBOLS, - LZX_MAX_CODEWORD_LEN, - freq_tabs->main_freq_table, - codes->main_lens, - codes->main_codewords); - - make_canonical_huffman_code(LZX_LENTREE_NUM_SYMBOLS, - LZX_MAX_CODEWORD_LEN, - freq_tabs->len_freq_table, - codes->len_lens, - codes->len_codewords); - - make_canonical_huffman_code(LZX_ALIGNEDTREE_NUM_SYMBOLS, 8, - freq_tabs->aligned_freq_table, - codes->aligned_lens, - codes->aligned_codewords); -} - -static void do_call_insn_translation(u32 *call_insn_target, int input_pos, - int32_t file_size) +/* + * Writes all compressed matches and literal bytes in an LZX block to the the + * output bitstream. + * + * @ostream + * The output bitstream. + * @block_type + * The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM). + * @match_tab + * The array of matches/literals that will be output (length @match_count). + * @match_count + * Number of matches/literals to be output. + * @codes + * Pointer to a structure that contains the codewords for the main, length, + * and aligned offset Huffman codes. + */ +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) { - int32_t abs_offset; - int32_t rel_offset; + for (unsigned i = 0; i < match_count; i++) { + struct lzx_match match = match_tab[i]; - 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; + /* High bit of the match indicates whether the match is an + * actual match (1) or a literal uncompressed byte (0) */ + if (match.data & 0x80000000) { + /* match */ + lzx_write_match(ostream, block_type, + match, codes); } else { - /* "compensating translation" */ - abs_offset = rel_offset - file_size; + /* literal byte */ + bitstream_put_bits(ostream, + codes->codewords.main[match.data], + codes->lens.main[match.data]); } - *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 uncompressed_data[], - int uncompressed_data_len) -{ - for (int i = 0; i < uncompressed_data_len - 10; i++) { - if (uncompressed_data[i] == 0xe8) { - do_call_insn_translation((u32*)&uncompressed_data[i + 1], - i, - LZX_WIM_MAGIC_FILESIZE); - i += 4; - } - } -} +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 */ +} -static const struct lz_params lzx_lz_params = { +/* 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_MIN_MATCH == 2, but 2-character matches are rarely useful; the - * minimum match for compression is set to 3 instead. */ - .min_match = 3, + LZX_ASSERT(block_type == LZX_BLOCKTYPE_ALIGNED || + block_type == LZX_BLOCKTYPE_VERBATIM); + lzx_assert_codes_valid(codes, num_main_syms); - .max_match = LZX_MAX_MATCH, - .good_match = LZX_MAX_MATCH, - .nice_match = LZX_MAX_MATCH, - .max_chain_len = LZX_MAX_MATCH, - .max_lazy_match = LZX_MAX_MATCH, - .too_far = 4096, -}; + /* The first three bits indicate the type of block and are one of the + * LZX_BLOCKTYPE_* constants. */ + bitstream_put_bits(ostream, block_type, 3); -/* - * Performs LZX compression on a block of data. - * - * @__uncompressed_data: Pointer to the data to be compressed. - * @uncompressed_len: Length, in bytes, of the data to be compressed. - * @compressed_data: Pointer to a location at least (@uncompressed_len - 1) - * bytes long into which the compressed data may be - * written. - * @compressed_len_ret: A pointer to an unsigned int into which the length of - * the compressed data may be returned. - * - * Returns zero if compression was successfully performed. In that case - * @compressed_data and @compressed_len_ret will contain the compressed data and - * its length. A return value of nonzero means that compressing the data did - * not reduce its size, and @compressed_data will not contain the full - * compressed data. - */ -int lzx_compress(const void *__uncompressed_data, unsigned uncompressed_len, - void *compressed_data, unsigned *compressed_len_ret) -{ - struct output_bitstream ostream; - u8 uncompressed_data[uncompressed_len + 8]; - struct lzx_freq_tables freq_tabs; - struct lzx_codes codes; - u32 match_tab[uncompressed_len]; - struct lru_queue queue; - unsigned num_matches; - unsigned compressed_len; - unsigned i; - int ret; - int block_type = LZX_BLOCKTYPE_ALIGNED; + /* 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 (uncompressed_len < 100) - return 1; + if (max_window_size >= 65536) + bitstream_put_bits(ostream, block_size >> 16, 8); - memset(&freq_tabs, 0, sizeof(freq_tabs)); - queue.R0 = 1; - queue.R1 = 1; - queue.R2 = 1; + bitstream_put_bits(ostream, block_size, 16); + } - /* The input data must be preprocessed. To avoid changing the original - * input, copy it to a temporary buffer. */ - memcpy(uncompressed_data, __uncompressed_data, uncompressed_len); + /* 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."); +} - /* Before doing any actual compression, do the call instruction (0xe8 - * byte) translation on the uncompressed data. */ - do_call_insn_preprocessing(uncompressed_data, uncompressed_len); +/* Write out the LZX blocks that were computed. */ +static void +lzx_write_all_blocks(struct lzx_compressor *ctx, struct output_bitstream *ostream) +{ - /* Determine the sequence of matches and literals that will be output, - * and in the process, keep counts of the number of times each symbol - * will be output, so that the Huffman trees can be made. */ + 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; + } +} - num_matches = lz_analyze_block(uncompressed_data, uncompressed_len, - match_tab, lzx_record_match, - lzx_record_literal, &freq_tabs, - &queue, freq_tabs.main_freq_table, - &lzx_lz_params); +/* 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; +} - lzx_make_huffman_codes(&freq_tabs, &codes); +/* 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; - /* Initialize the output bitstream. */ - init_output_bitstream(&ostream, compressed_data, uncompressed_len - 1); + LZX_ASSERT(match_len >= LZX_MIN_MATCH_LEN && match_len <= LZX_MAX_MATCH_LEN); - /* The first three bits tell us what kind of block it is, and are one - * of the LZX_BLOCKTYPE_* values. */ - bitstream_put_bits(&ostream, block_type, 3); + /* 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 next bit indicates whether the block size is the default (32768), - * indicated by a 1 bit, or whether the block size is given by the next - * 16 bits, indicated by a 0 bit. */ - if (uncompressed_len == 32768) { - bitstream_put_bits(&ostream, 1, 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 { - bitstream_put_bits(&ostream, 0, 1); - bitstream_put_bits(&ostream, uncompressed_len, 16); + /* 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]++; } - /* Write out the aligned offset tree. Note that M$ lies and says that - * the aligned offset tree comes after the length tree, but that is - * wrong; it actually is before the main tree. */ - if (block_type == LZX_BLOCKTYPE_ALIGNED) - for (i = 0; i < LZX_ALIGNEDTREE_NUM_SYMBOLS; i++) - bitstream_put_bits(&ostream, codes.aligned_lens[i], - LZX_ALIGNEDTREE_ELEMENT_SIZE); - - /* Write the pre-tree and lengths for the first LZX_NUM_CHARS symbols in the - * main tree. */ - ret = lzx_write_compressed_tree(&ostream, codes.main_lens, - LZX_NUM_CHARS); - if (ret != 0) - return ret; - - /* Write the pre-tree and symbols for the rest of the main tree. */ - ret = lzx_write_compressed_tree(&ostream, codes.main_lens + - LZX_NUM_CHARS, - LZX_MAINTREE_NUM_SYMBOLS - - LZX_NUM_CHARS); - if (ret != 0) - return ret; - - /* Write the pre-tree and symbols for the length tree. */ - ret = lzx_write_compressed_tree(&ostream, codes.len_lens, - LZX_LENTREE_NUM_SYMBOLS); - if (ret != 0) - return ret; - - /* Write the compressed literals. */ - ret = lzx_write_compressed_literals(&ostream, block_type, - match_tab, num_matches, &codes); - if (ret != 0) - return ret; - - ret = flush_output_bitstream(&ostream); - if (ret != 0) - return ret; - - compressed_len = ostream.bit_output - (u8*)compressed_data; - - *compressed_len_ret = compressed_len; - -#ifdef ENABLE_VERIFY_COMPRESSION - /* Verify that we really get the same thing back when decompressing. */ - u8 buf[uncompressed_len]; - ret = lzx_decompress(compressed_data, compressed_len, buf, - uncompressed_len); - if (ret != 0) { - ERROR("lzx_compress(): Failed to decompress data we compressed"); - abort(); - } - - for (i = 0; i < uncompressed_len; i++) { - if (buf[i] != *((u8*)__uncompressed_data + i)) { - ERROR("lzx_compress(): Data we compressed didn't " - "decompress to the original data (difference at " - "byte %u of %u)", i + 1, uncompressed_len); - abort(); - } - } -#endif - return 0; + /* 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 block_cost_t +lzx_match_cost_fast(unsigned offset, const struct lzx_lru_queue *queue) +{ + /* It seems well worth it to take the time to give priority to recently + * used offsets. */ + for (unsigned i = 0; i < LZX_NUM_RECENT_OFFSETS; i++) + if (offset == queue->R[i]) + return i; + + BUILD_BUG_ON(LZX_MAX_WINDOW_SIZE >= (block_cost_t)~0U); + 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; + } +} + +/* Advance the suffix array match-finder to the next position. */ +static void +lzx_lz_update_salink(input_idx_t i, + const input_idx_t SA[restrict], + const input_idx_t ISA[restrict], + struct salink link[restrict]) +{ + /* r = Rank of the suffix at the current position. */ + const input_idx_t r = ISA[i]; + + /* next = rank of LOWEST ranked suffix that is ranked HIGHER than the + * current suffix AND has a LOWER position, or -1 if none exists. */ + const input_idx_t next = link[r].next; + + /* prev = rank of HIGHEST ranked suffix that is ranked LOWER than the + * current suffix AND has a LOWER position, or -1 if none exists. */ + const input_idx_t prev = link[r].prev; + + /* Link the suffix at the current position into the linked list that + * contains all suffixes in the suffix array that are appear at or + * before the current position, sorted by rank. + * + * Save the values of all fields we overwrite so that rollback is + * possible. */ + if (next != (input_idx_t)~0U) { + + link[next].prev = r; + link[next].lcpprev = link[r].lcpnext; + } + + if (prev != (input_idx_t)~0U) { + + link[prev].next = r; + link[prev].lcpnext = link[r].lcpprev; + } +} + +/* + * Use the suffix array match-finder to retrieve a list of LZ matches at the + * current position. + * + * [in] @i Current position in the window. + * [in] @SA Suffix array for the window. + * [in] @ISA Inverse suffix array for the window. + * [inout] @link Suffix array links used internally by the match-finder. + * [out] @matches The (length, offset) pairs of the resulting matches will + * be written here, sorted in decreasing order by + * length. All returned lengths will be unique. + * [in] @queue Recently used match offsets, used when evaluating the + * cost of matches. + * [in] @min_match_len Minimum match length to return. + * [in] @max_matches_to_consider Maximum number of matches to consider at + * the position. + * [in] @max_matches_to_return Maximum number of matches to return. + * + * The return value is the number of matches found and written to @matches. + */ +static unsigned +lzx_lz_get_matches(const input_idx_t i, + const input_idx_t SA[const restrict], + const input_idx_t ISA[const restrict], + struct salink link[const restrict], + struct raw_match matches[const restrict], + const struct lzx_lru_queue * const restrict queue, + const unsigned min_match_len, + const u32 max_matches_to_consider, + const u32 max_matches_to_return) +{ + /* r = Rank of the suffix at the current position. */ + const input_idx_t r = ISA[i]; + + /* Prepare for searching the current position. */ + lzx_lz_update_salink(i, SA, ISA, link); + + /* L = rank of next suffix to the left; + * R = rank of next suffix to the right; + * lenL = length of match between current position and the suffix with rank L; + * lenR = length of match between current position and the suffix with rank R. + * + * This is left and right relative to the rank of the current suffix. + * Since the suffixes in the suffix array are sorted, the longest + * matches are immediately to the left and right (using the linked list + * to ignore all suffixes that occur later in the window). The match + * length decreases the farther left and right we go. We shall keep the + * length on both sides in sync in order to choose the lowest-cost match + * of each length. + */ + input_idx_t L = link[r].prev; + input_idx_t R = link[r].next; + input_idx_t lenL = link[r].lcpprev; + input_idx_t lenR = link[r].lcpnext; + + /* nmatches = number of matches found so far. */ + unsigned nmatches = 0; + + /* best_cost = cost of lowest-cost match found so far. + * + * We keep track of this so that we can ignore shorter matches that do + * not have lower costs than a longer matches already found. + */ + block_cost_t best_cost = INFINITE_BLOCK_COST; + + /* count_remaining = maximum number of possible matches remaining to be + * considered. */ + u32 count_remaining = max_matches_to_consider; + + /* pending = match currently being considered for a specific length. */ + struct raw_match pending; + block_cost_t pending_cost; + + while (lenL >= min_match_len || lenR >= min_match_len) + { + pending.len = lenL; + pending_cost = INFINITE_BLOCK_COST; + block_cost_t cost; + + /* Extend left. */ + if (lenL >= min_match_len && lenL >= lenR) { + for (;;) { + + if (--count_remaining == 0) + goto out_save_pending; + + input_idx_t offset = i - SA[L]; + + /* Save match if it has smaller cost. */ + cost = lzx_match_cost_fast(offset, queue); + if (cost < pending_cost) { + pending.offset = offset; + pending_cost = cost; + } + + if (link[L].lcpprev < lenL) { + /* Match length decreased. */ + + lenL = link[L].lcpprev; + + /* Save the pending match unless the + * right side still may have matches of + * this length to be scanned, or if a + * previous (longer) match had lower + * cost. */ + if (pending.len > lenR) { + if (pending_cost < best_cost) { + best_cost = pending_cost; + matches[nmatches++] = pending; + if (nmatches == max_matches_to_return) + return nmatches; + } + pending.len = lenL; + pending_cost = INFINITE_BLOCK_COST; + } + if (lenL < min_match_len || lenL < lenR) + break; + } + L = link[L].prev; + } + } + + pending.len = lenR; + + /* Extend right. */ + if (lenR >= min_match_len && lenR > lenL) { + for (;;) { + + if (--count_remaining == 0) + goto out_save_pending; + + input_idx_t offset = i - SA[R]; + + /* Save match if it has smaller cost. */ + cost = lzx_match_cost_fast(offset, queue); + if (cost < pending_cost) { + pending.offset = offset; + pending_cost = cost; + } + + if (link[R].lcpnext < lenR) { + /* Match length decreased. */ + + lenR = link[R].lcpnext; + + /* Save the pending match unless a + * previous (longer) match had lower + * cost. */ + if (pending_cost < best_cost) { + matches[nmatches++] = pending; + best_cost = pending_cost; + if (nmatches == max_matches_to_return) + return nmatches; + } + + if (lenR < min_match_len || lenR <= lenL) + break; + + pending.len = lenR; + pending_cost = INFINITE_BLOCK_COST; + } + R = link[R].next; + } + } + } + goto out; + +out_save_pending: + if (pending_cost != INFINITE_BLOCK_COST) + matches[nmatches++] = pending; + +out: + return nmatches; +} + + +/* 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, unsigned 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; + lzx_lz_update_salink(ctx->match_window_pos++, ctx->SA, + ctx->ISA, ctx->salink); + } + } +} + +/* Retrieve a list of matches available at the next position in the input. + * + * The matches are written to ctx->matches in decreasing order of length, and + * the return value is the number of matches found. */ +static unsigned +lzx_lz_get_matches_caching(struct lzx_compressor *ctx, + const struct lzx_lru_queue *queue, + struct raw_match **matches_ret) +{ + unsigned 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 { + unsigned min_match_len = LZX_MIN_MATCH_LEN; + if (!ctx->params.alg_params.slow.use_len2_matches) + min_match_len = max(min_match_len, 3); + const u32 max_search_depth = ctx->params.alg_params.slow.max_search_depth; + const u32 max_matches_per_pos = ctx->params.alg_params.slow.max_matches_per_pos; + + if (unlikely(max_search_depth == 0 || max_matches_per_pos == 0)) + num_matches = 0; + else + num_matches = lzx_lz_get_matches(ctx->match_window_pos, + ctx->SA, + ctx->ISA, + ctx->salink, + matches, + queue, + min_match_len, + max_search_depth, + max_matches_per_pos); + 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 (unsigned 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 (unsigned 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; +} + +/* + * Reverse the linked list of near-optimal matches so that they can be returned + * in forwards order. + * + * Returns the first match in the list. + */ +static struct raw_match +lzx_lz_reverse_near_optimal_match_list(struct lzx_compressor *ctx, + unsigned cur_pos) +{ + unsigned prev_link, saved_prev_link; + unsigned prev_match_offset, saved_prev_match_offset; + + ctx->optimum_end_idx = cur_pos; + + saved_prev_link = ctx->optimum[cur_pos].prev.link; + saved_prev_match_offset = ctx->optimum[cur_pos].prev.match_offset; + + do { + prev_link = saved_prev_link; + prev_match_offset = saved_prev_match_offset; + + saved_prev_link = ctx->optimum[prev_link].prev.link; + saved_prev_match_offset = ctx->optimum[prev_link].prev.match_offset; + + ctx->optimum[prev_link].next.link = cur_pos; + ctx->optimum[prev_link].next.match_offset = prev_match_offset; + + cur_pos = prev_link; + } while (cur_pos != 0); + + ctx->optimum_cur_idx = ctx->optimum[0].next.link; + + return (struct raw_match) + { .len = ctx->optimum_cur_idx, + .offset = ctx->optimum[0].next.match_offset, + }; +} + +/* + * lzx_lz_get_near_optimal_match() - + * + * Choose the optimal match or literal to use at the next position in the input. + * + * Unlike a greedy parser that always takes the longest match, or even a + * parser with one match/literal look-ahead like zlib, the algorithm used here + * may look ahead many matches/literals to determine the optimal match/literal to + * output next. The motivation is that the compression ratio is improved if the + * compressor can do things like use a shorter-than-possible match in order to + * allow a longer match later, and also take into account the Huffman code cost + * model rather than simply assuming that longer is better. + * + * Still, this is not truly an optimal parser because very long matches are + * taken immediately, and the raw match-finder takes some shortcuts. This is + * done to avoid considering many different alternatives that are unlikely to + * be significantly better. + * + * This algorithm is based on that used in 7-Zip's DEFLATE encoder. + * + * Each call to this function does one of two things: + * + * 1. Build a near-optimal sequence of matches/literals, up to some point, that + * will be returned by subsequent calls to this function, then return the + * first one. + * + * OR + * + * 2. Return the next match/literal previously computed by a call to this + * function; + * + * This function relies on the following state in the compressor context: + * + * ctx->window (read-only: preprocessed data being compressed) + * ctx->cost (read-only: cost model to use) + * ctx->optimum (internal state; leave uninitialized) + * ctx->optimum_cur_idx (must set to 0 before first call) + * ctx->optimum_end_idx (must set to 0 before first call) + * + * Plus any state used by the raw match-finder. + * + * The return value is a (length, offset) pair specifying the match or literal + * chosen. For literals, the length is less than LZX_MIN_MATCH_LEN and the + * offset is meaningless. + */ +static struct raw_match +lzx_lz_get_near_optimal_match(struct lzx_compressor * ctx) +{ + unsigned num_possible_matches; + struct raw_match *possible_matches; + struct raw_match match; + unsigned longest_match_len; + + if (ctx->optimum_cur_idx != ctx->optimum_end_idx) { + /* Case 2: Return the next match/literal already found. */ + match.len = ctx->optimum[ctx->optimum_cur_idx].next.link - + ctx->optimum_cur_idx; + match.offset = ctx->optimum[ctx->optimum_cur_idx].next.match_offset; + + ctx->optimum_cur_idx = ctx->optimum[ctx->optimum_cur_idx].next.link; + return match; + } + + /* Case 1: Compute a new list of matches/literals to return. */ + + ctx->optimum_cur_idx = 0; + ctx->optimum_end_idx = 0; + + /* Get matches at this position. */ + num_possible_matches = lzx_lz_get_matches_caching(ctx, &ctx->queue, &possible_matches); + + /* If no matches found, return literal. */ + if (num_possible_matches == 0) + return (struct raw_match){ .len = 0 }; + + /* The matches that were found are sorted in decreasing order by length. + * Get the length of the longest one. */ + longest_match_len = possible_matches[0].len; + + /* Greedy heuristic: if the longest match that was found is greater + * than the number of fast bytes, return it immediately; don't both + * doing more work. */ + if (longest_match_len > ctx->params.alg_params.slow.num_fast_bytes) { + lzx_lz_skip_bytes(ctx, longest_match_len - 1); + return possible_matches[0]; + } + + /* Calculate the cost to reach the next position by outputting a + * literal. */ + ctx->optimum[0].queue = ctx->queue; + ctx->optimum[1].queue = ctx->optimum[0].queue; + ctx->optimum[1].cost = lzx_literal_cost(ctx->window[ctx->match_window_pos], + &ctx->costs); + ctx->optimum[1].prev.link = 0; + + /* Calculate the cost to reach any position up to and including that + * reached by the longest match, using the shortest (i.e. closest) match + * that reaches each position. */ + BUILD_BUG_ON(LZX_MIN_MATCH_LEN != 2); + for (unsigned len = LZX_MIN_MATCH_LEN, match_idx = num_possible_matches - 1; + len <= longest_match_len; len++) { + + LZX_ASSERT(match_idx < num_possible_matches); + + ctx->optimum[len].queue = ctx->optimum[0].queue; + ctx->optimum[len].prev.link = 0; + ctx->optimum[len].prev.match_offset = possible_matches[match_idx].offset; + ctx->optimum[len].cost = lzx_match_cost(len, + possible_matches[match_idx].offset, + &ctx->costs, + &ctx->optimum[len].queue); + if (len == possible_matches[match_idx].len) + match_idx--; + } + + unsigned cur_pos = 0; + + /* len_end: greatest index forward at which costs have been calculated + * so far */ + unsigned len_end = longest_match_len; + + for (;;) { + /* Advance to next position. */ + cur_pos++; + + if (cur_pos == len_end || cur_pos == LZX_OPTIM_ARRAY_SIZE) + return lzx_lz_reverse_near_optimal_match_list(ctx, cur_pos); + + /* retrieve the number of matches available at this position */ + num_possible_matches = lzx_lz_get_matches_caching(ctx, &ctx->optimum[cur_pos].queue, + &possible_matches); + + unsigned new_len = 0; + + if (num_possible_matches != 0) { + new_len = possible_matches[0].len; + + /* Greedy heuristic: if we found a match greater than + * the number of fast bytes, stop immediately. */ + if (new_len > ctx->params.alg_params.slow.num_fast_bytes) { + + /* Build the list of matches to return and get + * the first one. */ + match = lzx_lz_reverse_near_optimal_match_list(ctx, cur_pos); + + /* Append the long match to the end of the list. */ + ctx->optimum[cur_pos].next.match_offset = + possible_matches[0].offset; + ctx->optimum[cur_pos].next.link = cur_pos + new_len; + ctx->optimum_end_idx = cur_pos + new_len; + + /* Skip over the remaining bytes of the long match. */ + lzx_lz_skip_bytes(ctx, new_len - 1); + + /* Return first match in the list */ + return match; + } + } + + /* Consider proceeding with a literal byte. */ + block_cost_t cur_cost = ctx->optimum[cur_pos].cost; + block_cost_t cur_plus_literal_cost = cur_cost + + lzx_literal_cost(ctx->window[ctx->match_window_pos - 1], + &ctx->costs); + if (cur_plus_literal_cost < ctx->optimum[cur_pos + 1].cost) { + ctx->optimum[cur_pos + 1].cost = cur_plus_literal_cost; + ctx->optimum[cur_pos + 1].prev.link = cur_pos; + ctx->optimum[cur_pos + 1].queue = ctx->optimum[cur_pos].queue; + } + + if (num_possible_matches == 0) + continue; + + /* Consider proceeding with a match. */ + + while (len_end < cur_pos + new_len) + ctx->optimum[++len_end].cost = INFINITE_BLOCK_COST; + + for (unsigned len = LZX_MIN_MATCH_LEN, match_idx = num_possible_matches - 1; + len <= new_len; len++) { + LZX_ASSERT(match_idx < num_possible_matches); + struct lzx_lru_queue q = ctx->optimum[cur_pos].queue; + block_cost_t cost = cur_cost + lzx_match_cost(len, + possible_matches[match_idx].offset, + &ctx->costs, + &q); + + if (cost < ctx->optimum[cur_pos + len].cost) { + ctx->optimum[cur_pos + len].cost = cost; + ctx->optimum[cur_pos + len].prev.link = cur_pos; + ctx->optimum[cur_pos + len].prev.match_offset = + possible_matches[match_idx].offset; + ctx->optimum[cur_pos + len].queue = q; + } + + if (len == possible_matches[match_idx].len) + match_idx--; + } + } +} + +/* + * Set default symbol costs. + */ +static void +lzx_set_default_costs(struct lzx_costs * costs, unsigned num_main_syms) +{ + unsigned i; + + /* Literal symbols */ + for (i = 0; i < LZX_NUM_CHARS; i++) + costs->main[i] = 8; + + /* Match header symbols */ + for (; i < num_main_syms; i++) + costs->main[i] = 10; + + /* Length symbols */ + for (i = 0; i < LZX_LENCODE_NUM_SYMBOLS; i++) + costs->len[i] = 8; + + /* Aligned offset symbols */ + for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) + costs->aligned[i] = 3; +} + +/* Given the frequencies of symbols in a 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 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 its type to that which has the minimum cost to + * output. */ +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) { + 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); + ctx->optimum_cur_idx = 0; + ctx->optimum_end_idx = 0; + + 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); +} + +/* Initialize the suffix array match-finder for the specified input. */ +static void +lzx_lz_init_matchfinder(const u8 T[const restrict], + const input_idx_t n, + input_idx_t SA[const restrict], + input_idx_t ISA[const restrict], + input_idx_t LCP[const restrict], + struct salink link[const restrict], + const unsigned max_match_len) +{ + /* Compute SA (Suffix Array). */ + + { + /* ISA and link are used as temporary space. */ + BUILD_BUG_ON(LZX_MIN_WINDOW_SIZE * sizeof(ISA[0]) < 256 * sizeof(saidx_t)); + BUILD_BUG_ON(LZX_MIN_WINDOW_SIZE * 2 * sizeof(link[0]) < 256 * 256 * sizeof(saidx_t)); + + if (sizeof(input_idx_t) == sizeof(saidx_t)) { + divsufsort(T, SA, n, (saidx_t*)ISA, (saidx_t*)link); + } else { + saidx_t sa[n]; + divsufsort(T, sa, n, (saidx_t*)ISA, (saidx_t*)link); + for (input_idx_t i = 0; i < n; i++) + SA[i] = sa[i]; + } + } + +#ifdef ENABLE_LZX_DEBUG + + LZX_ASSERT(n > 0); + + /* Verify suffix array. */ + { + bool found[n]; + ZERO_ARRAY(found); + for (input_idx_t r = 0; r < n; r++) { + input_idx_t i = SA[r]; + LZX_ASSERT(i < n); + LZX_ASSERT(!found[i]); + found[i] = true; + } + } + + for (input_idx_t r = 0; r < n - 1; r++) { + + input_idx_t i1 = SA[r]; + input_idx_t i2 = SA[r + 1]; + + input_idx_t n1 = n - i1; + input_idx_t n2 = n - i2; + + LZX_ASSERT(memcmp(&T[i1], &T[i2], min(n1, n2)) <= 0); + } + LZX_DEBUG("Verified SA (len %u)", n); +#endif /* ENABLE_LZX_DEBUG */ + + /* Compute ISA (Inverse Suffix Array) */ + for (input_idx_t r = 0; r < n; r++) + ISA[SA[r]] = r; + + /* Compute LCP (longest common prefix) array. + * + * Algorithm adapted from Kasai et al. 2001: "Linear-Time + * Longest-Common-Prefix Computation in Suffix Arrays and Its + * Applications". */ + { + input_idx_t h = 0; + for (input_idx_t i = 0; i < n; i++) { + input_idx_t r = ISA[i]; + if (r > 0) { + input_idx_t j = SA[r - 1]; + + input_idx_t lim = min(n - i, n - j); + + while (h < lim && T[i + h] == T[j + h]) + h++; + LCP[r] = h; + if (h > 0) + h--; + } + } + } + +#ifdef ENABLE_LZX_DEBUG + /* Verify LCP array. */ + for (input_idx_t r = 0; r < n - 1; r++) { + LZX_ASSERT(ISA[SA[r]] == r); + LZX_ASSERT(ISA[SA[r + 1]] == r + 1); + + input_idx_t i1 = SA[r]; + input_idx_t i2 = SA[r + 1]; + input_idx_t lcp = LCP[r + 1]; + + input_idx_t n1 = n - i1; + input_idx_t n2 = n - i2; + + LZX_ASSERT(lcp <= min(n1, n2)); + + LZX_ASSERT(memcmp(&T[i1], &T[i2], lcp) == 0); + if (lcp < min(n1, n2)) + LZX_ASSERT(T[i1 + lcp] != T[i2 + lcp]); + } +#endif /* ENABLE_LZX_DEBUG */ + + /* Compute salink.next and salink.lcpnext. + * + * Algorithm adapted from Crochemore et al. 2009: + * "LPF computation revisited". + * + * Note: we cap lcpnext to the maximum match length so that the + * match-finder need not worry about it later. */ + link[n - 1].next = (input_idx_t)~0U; + link[n - 1].prev = (input_idx_t)~0U; + link[n - 1].lcpnext = 0; + link[n - 1].lcpprev = 0; + for (input_idx_t r = n - 2; r != (input_idx_t)~0U; r--) { + input_idx_t t = r + 1; + input_idx_t l = LCP[t]; + while (t != (input_idx_t)~0 && SA[t] > SA[r]) { + l = min(l, link[t].lcpnext); + t = link[t].next; + } + link[r].next = t; + link[r].lcpnext = min(l, max_match_len); + LZX_ASSERT(t == (input_idx_t)~0U || l <= n - SA[t]); + LZX_ASSERT(l <= n - SA[r]); + LZX_ASSERT(memcmp(&T[SA[r]], &T[SA[t]], l) == 0); + } + + /* Compute salink.prev and salink.lcpprev. + * + * Algorithm adapted from Crochemore et al. 2009: + * "LPF computation revisited". + * + * Note: we cap lcpprev to the maximum match length so that the + * match-finder need not worry about it later. */ + link[0].prev = (input_idx_t)~0; + link[0].next = (input_idx_t)~0; + link[0].lcpprev = 0; + link[0].lcpnext = 0; + for (input_idx_t r = 1; r < n; r++) { + input_idx_t t = r - 1; + input_idx_t l = LCP[r]; + while (t != (input_idx_t)~0 && SA[t] > SA[r]) { + l = min(l, link[t].lcpprev); + t = link[t].prev; + } + link[r].prev = t; + link[r].lcpprev = min(l, max_match_len); + LZX_ASSERT(t == (input_idx_t)~0 || l <= n - SA[t]); + LZX_ASSERT(l <= n - SA[r]); + LZX_ASSERT(memcmp(&T[SA[r]], &T[SA[t]], l) == 0); + } +} + +/* 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. */ + lzx_lz_init_matchfinder(ctx->window, ctx->window_size, + ctx->SA, ctx->ISA, ctx->LCP, ctx->salink, + LZX_MAX_MATCH_LEN); + 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); + + 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; + } + } +} + +/* API function documented in wimlib.h */ +WIMLIBAPI unsigned +wimlib_lzx_compress2(const void * const restrict uncompressed_data, + unsigned const uncompressed_len, + void * const restrict compressed_data, + struct wimlib_lzx_context * const restrict lzx_ctx) +{ + struct lzx_compressor *ctx = (struct lzx_compressor*)lzx_ctx; + struct output_bitstream ostream; + input_idx_t compressed_len; + + if (uncompressed_len < 100) { + LZX_DEBUG("Too small to bother compressing."); + return 0; + } + + if (uncompressed_len > ctx->max_window_size) { + LZX_DEBUG("Can't compress %u bytes using window of %u bytes!", + uncompressed_len, ctx->max_window_size); + return 0; + } + + LZX_DEBUG("Attempting to compress %u bytes...", uncompressed_len); + + /* The input data must be preprocessed. To avoid changing the original + * input, copy it to a temporary buffer. */ + memcpy(ctx->window, uncompressed_data, uncompressed_len); + ctx->window_size = uncompressed_len; + + /* 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, ctx->window_size - 1); + lzx_write_all_blocks(ctx, &ostream); + + LZX_DEBUG("Flushing bitstream..."); + compressed_len = flush_output_bitstream(&ostream); + if (compressed_len == ~(input_idx_t)0) { + LZX_DEBUG("Data did not compress to less than original length!"); + return 0; + } + + LZX_DEBUG("Done: compressed %u => %u bytes.", + uncompressed_len, compressed_len); + + /* 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 + ) + { + /* The decompression buffer can be any temporary space that's no + * longer needed. */ + u8 *buf = (u8*)(ctx->SA ? ctx->SA : ctx->prev_tab); + + if (wimlib_lzx_decompress2(compressed_data, compressed_len, + buf, uncompressed_len, ctx->max_window_size)) + { + ERROR("Failed to decompress data we " + "compressed using LZX algorithm"); + wimlib_assert(0); + return 0; + } + + if (memcmp(uncompressed_data, buf, uncompressed_len)) { + ERROR("Data we compressed using LZX algorithm " + "didn't decompress to original"); + wimlib_assert(0); + return 0; + } + } + return compressed_len; +} + +static bool +lzx_params_compatible(const struct wimlib_lzx_params *oldparams, + const struct wimlib_lzx_params *newparams) +{ + return 0 == memcmp(oldparams, newparams, sizeof(struct wimlib_lzx_params)); +} + +static struct wimlib_lzx_params lzx_user_default_params; +static struct wimlib_lzx_params *lzx_user_default_params_ptr; + +static bool +lzx_params_valid(const struct wimlib_lzx_params *params) +{ + /* Validate parameters. */ + if (params->size_of_this != sizeof(struct wimlib_lzx_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) { + 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; +} + +/* API function documented in wimlib.h */ +WIMLIBAPI int +wimlib_lzx_set_default_params(const struct wimlib_lzx_params * params) +{ + if (params) { + if (!lzx_params_valid(params)) + return WIMLIB_ERR_INVALID_PARAM; + lzx_user_default_params = *params; + lzx_user_default_params_ptr = &lzx_user_default_params; + } else { + lzx_user_default_params_ptr = NULL; + } + return 0; +} + +/* API function documented in wimlib.h */ +WIMLIBAPI int +wimlib_lzx_alloc_context(u32 window_size, + const struct wimlib_lzx_params *params, + struct wimlib_lzx_context **ctx_pp) +{ + + LZX_DEBUG("Allocating LZX context..."); + + if (!lzx_window_size_valid(window_size)) + return WIMLIB_ERR_INVALID_PARAM; + + struct lzx_compressor *ctx; + + static const struct wimlib_lzx_params fast_default = { + .size_of_this = sizeof(struct wimlib_lzx_params), + .algorithm = WIMLIB_LZX_ALGORITHM_FAST, + .use_defaults = 0, + .alg_params = { + .fast = { + }, + }, + }; + static const struct wimlib_lzx_params slow_default = { + .size_of_this = sizeof(struct wimlib_lzx_params), + .algorithm = WIMLIB_LZX_ALGORITHM_SLOW, + .use_defaults = 0, + .alg_params = { + .slow = { + .use_len2_matches = 1, + .num_fast_bytes = 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, + }, + }, + }; + + if (params) { + if (!lzx_params_valid(params)) + return WIMLIB_ERR_INVALID_PARAM; + } else { + LZX_DEBUG("Using default algorithm and parameters."); + if (lzx_user_default_params_ptr) + params = lzx_user_default_params_ptr; + else + params = &slow_default; + } + + if (params->use_defaults) { + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) + params = &slow_default; + else + params = &fast_default; + } + + if (ctx_pp) { + ctx = *(struct lzx_compressor**)ctx_pp; + + if (ctx && + lzx_params_compatible(&ctx->params, params) && + ctx->max_window_size == window_size) + return 0; + } else { + LZX_DEBUG("Check parameters only."); + return 0; + } + + LZX_DEBUG("Allocating memory."); + + ctx = CALLOC(1, sizeof(struct lzx_compressor)); + if (ctx == NULL) + goto err; + + 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 err; + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_FAST) { + ctx->prev_tab = MALLOC(window_size * sizeof(ctx->prev_tab[0])); + if (ctx->prev_tab == NULL) + goto err; + } + + 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 err; + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { + ctx->SA = MALLOC(3U * window_size * sizeof(ctx->SA[0])); + if (ctx->SA == NULL) + goto err; + ctx->ISA = ctx->SA + window_size; + ctx->LCP = ctx->ISA + window_size; + + ctx->salink = MALLOC(window_size * sizeof(ctx->salink[0])); + if (ctx->salink == NULL) + goto err; + } + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { + ctx->optimum = MALLOC((LZX_OPTIM_ARRAY_SIZE + LZX_MAX_MATCH_LEN) * + sizeof(ctx->optimum[0])); + if (ctx->optimum == NULL) + goto err; + } + + 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 err; + } + + ctx->chosen_matches = MALLOC(window_size * sizeof(ctx->chosen_matches[0])); + if (ctx->chosen_matches == NULL) + goto err; + + memcpy(&ctx->params, params, sizeof(struct wimlib_lzx_params)); + memset(&ctx->zero_codes, 0, sizeof(ctx->zero_codes)); + + LZX_DEBUG("Successfully allocated new LZX context."); + + wimlib_lzx_free_context(*ctx_pp); + *ctx_pp = (struct wimlib_lzx_context*)ctx; + return 0; + +err: + wimlib_lzx_free_context((struct wimlib_lzx_context*)ctx); + LZX_DEBUG("Ran out of memory."); + return WIMLIB_ERR_NOMEM; +} + +/* API function documented in wimlib.h */ +WIMLIBAPI void +wimlib_lzx_free_context(struct wimlib_lzx_context *_ctx) +{ + struct lzx_compressor *ctx = (struct lzx_compressor*)_ctx; + + if (ctx) { + FREE(ctx->chosen_matches); + FREE(ctx->cached_matches); + FREE(ctx->optimum); + FREE(ctx->salink); + FREE(ctx->SA); + FREE(ctx->block_specs); + FREE(ctx->prev_tab); + FREE(ctx->window); + FREE(ctx); + } +} + +/* API function documented in wimlib.h */ +WIMLIBAPI unsigned +wimlib_lzx_compress(const void * const restrict uncompressed_data, + unsigned const uncompressed_len, + void * const restrict compressed_data) +{ + int ret; + struct wimlib_lzx_context *ctx = NULL; + unsigned compressed_len; + + ret = wimlib_lzx_alloc_context(32768, NULL, &ctx); + if (ret) { + wimlib_assert(ret != WIMLIB_ERR_INVALID_PARAM); + WARNING("Couldn't allocate LZX compression context: %"TS"", + wimlib_get_error_string(ret)); + return 0; + } + + compressed_len = wimlib_lzx_compress2(uncompressed_data, + uncompressed_len, + compressed_data, + ctx); + + wimlib_lzx_free_context(ctx); + + return compressed_len; }