/*
* 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.
/*
- * This file provides wimlib_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.
*/
#ifdef HAVE_CONFIG_H
#include "wimlib.h"
#include "wimlib/compress.h"
+#include "wimlib/endianness.h"
+#include "wimlib/error.h"
#include "wimlib/lzx.h"
#include "wimlib/util.h"
-
-#include <stdlib.h>
+#include <pthread.h>
+#include <math.h>
#include <string.h>
+#ifdef ENABLE_LZX_DEBUG
+# include "wimlib/decompress.h"
+#endif
-/* 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];
+#include "divsufsort/divsufsort.h"
- u16 len_codewords[LZX_LENTREE_NUM_SYMBOLS];
- u8 len_lens[LZX_LENTREE_NUM_SYMBOLS];
+typedef u32 block_cost_t;
+#define INFINITE_BLOCK_COST ((block_cost_t)~0U)
- u16 aligned_codewords[LZX_ALIGNEDTREE_NUM_SYMBOLS];
- u8 aligned_lens[LZX_ALIGNEDTREE_NUM_SYMBOLS];
+#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];
};
-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];
+/* 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];
};
-/* Returns the LZX position slot that corresponds to a given formatted offset.
+/* Costs for the LZX main, length, and aligned offset Huffman symbols.
*
- * Logically, this returns the smallest i such that
- * formatted_offset >= lzx_position_base[i].
+ * If a codeword has zero frequency, it must still be assigned some nonzero cost
+ * --- generally a high cost, since even if it gets used in the next iteration,
+ * it probably will not be used very times. */
+struct lzx_costs {
+ u8 main[LZX_MAINCODE_MAX_NUM_SYMBOLS];
+ u8 len[LZX_LENCODE_NUM_SYMBOLS];
+ u8 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS];
+};
+
+/* The LZX main, length, and aligned offset Huffman codes */
+struct lzx_codes {
+ struct lzx_codewords codewords;
+ struct lzx_lens lens;
+};
+
+/* Tables for tallying symbol frequencies in the three LZX alphabets */
+struct lzx_freqs {
+ input_idx_t main[LZX_MAINCODE_MAX_NUM_SYMBOLS];
+ input_idx_t len[LZX_LENCODE_NUM_SYMBOLS];
+ input_idx_t aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS];
+};
+
+/* LZX intermediate match/literal format */
+struct lzx_match {
+ /* Bit Description
+ *
+ * 31 1 if a match, 0 if a literal.
+ *
+ * 30-25 position slot. This can be at most 50, so it will fit in 6
+ * bits.
+ *
+ * 8-24 position footer. This is the offset of the real formatted
+ * offset from the position base. This can be at most 17 bits
+ * (since lzx_extra_bits[LZX_MAX_POSITION_SLOTS - 1] is 17).
+ *
+ * 0-7 length of match, minus 2. This can be at most
+ * (LZX_MAX_MATCH_LEN - 2) == 255, so it will fit in 8 bits. */
+ u32 data;
+};
+
+/* Raw LZ match/literal format: just a length and offset.
*
- * 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);
- }
-}
+ * 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.
+ *
+ * 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
+static void
lzx_write_match(struct output_bitstream *out, int block_type,
- u32 match, const struct lzx_codes *codes)
+ 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
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
* 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;
/* 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
* 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;
* 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;
* 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;
/* 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;
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);
}
+/*
+ * 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
-do_call_insn_translation(u32 *call_insn_target, int input_pos,
- s32 file_size)
+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)
{
- s32 abs_offset;
- s32 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)
+lzx_assert_codes_valid(const struct lzx_codes * codes, unsigned num_main_syms)
{
- 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 const struct lz_params lzx_lz_params = {
-
- /* LZX_MIN_MATCH == 2, but 2-character matches are rarely useful; the
- * minimum match for compression is set to 3 instead. */
- .min_match = 3,
+#ifdef ENABLE_LZX_DEBUG
+ unsigned i;
- .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,
-};
+ 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 */
+}
-/* Documented in wimlib.h */
-WIMLIBAPI unsigned
-wimlib_lzx_compress(const void *__uncompressed_data, unsigned uncompressed_len,
- void *compressed_data)
+/* 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)
{
- 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;
-
- wimlib_assert(uncompressed_len <= 32768);
-
- if (uncompressed_len < 100)
- return 0;
-
- memset(&freq_tabs, 0, sizeof(freq_tabs));
- queue.R0 = 1;
- queue.R1 = 1;
- queue.R2 = 1;
-
- /* 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);
- memset(uncompressed_data + uncompressed_len, 0, 8);
-
- /* Before doing any actual compression, do the call instruction (0xe8
- * byte) translation on the uncompressed data. */
- do_call_insn_preprocessing(uncompressed_data, uncompressed_len);
-
- /* 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. */
- 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);
+ LZX_ASSERT(block_type == LZX_BLOCKTYPE_ALIGNED ||
+ block_type == LZX_BLOCKTYPE_VERBATIM);
+ lzx_assert_codes_valid(codes, num_main_syms);
- lzx_make_huffman_codes(&freq_tabs, &codes);
+ /* The first three bits indicate the type of block and are one of the
+ * LZX_BLOCKTYPE_* constants. */
+ bitstream_put_bits(ostream, block_type, 3);
- /* Initialize the output bitstream. */
- init_output_bitstream(&ostream, compressed_data, uncompressed_len - 1);
+ /* 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);
- /* 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);
+ if (max_window_size >= 65536)
+ bitstream_put_bits(ostream, block_size >> 16, 8);
- /* 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);
- } else {
- bitstream_put_bits(&ostream, 0, 1);
- bitstream_put_bits(&ostream, uncompressed_len, 16);
+ bitstream_put_bits(ostream, block_size, 16);
}
- /* 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. */
+ /* 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_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)
- return 0;
-
- /* 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)
- return 0;
+ for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++)
+ bitstream_put_bits(ostream, codes->lens.aligned[i],
+ LZX_ALIGNEDCODE_ELEMENT_SIZE);
+
+ LZX_DEBUG("Writing main code...");
+
+ /* Write the precode and lengths for the first LZX_NUM_CHARS symbols in
+ * the main code, which are the codewords for literal bytes. */
+ lzx_write_compressed_code(ostream,
+ codes->lens.main,
+ prev_codes->lens.main,
+ LZX_NUM_CHARS);
+
+ /* Write the precode and lengths for the rest of the main code, which
+ * are the codewords for match headers. */
+ lzx_write_compressed_code(ostream,
+ codes->lens.main + LZX_NUM_CHARS,
+ prev_codes->lens.main + LZX_NUM_CHARS,
+ num_main_syms - LZX_NUM_CHARS);
+
+ LZX_DEBUG("Writing length code...");
+
+ /* Write the precode and lengths for the length code. */
+ lzx_write_compressed_code(ostream,
+ codes->lens.len,
+ prev_codes->lens.len,
+ LZX_LENCODE_NUM_SYMBOLS);
+
+ LZX_DEBUG("Writing matches and literals...");
+
+ /* Write the actual matches and literals. */
+ lzx_write_matches_and_literals(ostream, block_type,
+ chosen_matches, num_chosen_matches,
+ codes);
+
+ LZX_DEBUG("Done writing block.");
+}
- /* Write the pre-tree and symbols for the length tree. */
- ret = lzx_write_compressed_tree(&ostream, codes.len_lens,
- LZX_LENTREE_NUM_SYMBOLS);
- if (ret)
- return 0;
+/* Write out the LZX blocks that were computed. */
+static void
+lzx_write_all_blocks(struct lzx_compressor *ctx, struct output_bitstream *ostream)
+{
- /* Write the compressed literals. */
- ret = lzx_write_compressed_literals(&ostream, block_type,
- match_tab, num_matches, &codes);
- if (ret)
- return 0;
+ 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;
+ }
+}
- ret = flush_output_bitstream(&ostream);
- if (ret)
- return 0;
+/* Constructs an LZX match from a literal byte and updates the main code symbol
+ * frequencies. */
+static u32
+lzx_tally_literal(u8 lit, struct lzx_freqs *freqs)
+{
+ freqs->main[lit]++;
+ return (u32)lit;
+}
+
+/* Constructs an LZX match from an offset and a length, and updates the LRU
+ * queue and the frequency of symbols in the main, length, and aligned offset
+ * alphabets. The return value is a 32-bit number that provides the match in an
+ * intermediate representation documented below. */
+static u32
+lzx_tally_match(unsigned match_len, unsigned match_offset,
+ struct lzx_freqs *freqs, struct lzx_lru_queue *queue)
+{
+ unsigned position_slot;
+ unsigned position_footer;
+ u32 len_header;
+ unsigned main_symbol;
+ unsigned len_footer;
+ unsigned adjusted_match_len;
+
+ LZX_ASSERT(match_len >= LZX_MIN_MATCH_LEN && match_len <= LZX_MAX_MATCH_LEN);
+
+ /* The match offset shall be encoded as a position slot (itself encoded
+ * as part of the main symbol) and a position footer. */
+ position_slot = lzx_get_position_slot(match_offset, queue);
+ position_footer = (match_offset + LZX_OFFSET_OFFSET) &
+ ((1U << lzx_get_num_extra_bits(position_slot)) - 1);
+
+ /* The match length shall be encoded as a length header (itself encoded
+ * as part of the main symbol) and an optional length footer. */
+ adjusted_match_len = match_len - LZX_MIN_MATCH_LEN;
+ if (adjusted_match_len < LZX_NUM_PRIMARY_LENS) {
+ /* No length footer needed. */
+ len_header = adjusted_match_len;
+ } else {
+ /* Length footer needed. It will be encoded using the length
+ * code. */
+ len_header = LZX_NUM_PRIMARY_LENS;
+ len_footer = adjusted_match_len - LZX_NUM_PRIMARY_LENS;
+ freqs->len[len_footer]++;
+ }
+
+ /* Account for the main symbol. */
+ main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS;
+
+ freqs->main[main_symbol]++;
+
+ /* In an aligned offset block, 3 bits of the position footer are output
+ * as an aligned offset symbol. Account for this, although we may
+ * ultimately decide to output the block as verbatim. */
+
+ /* The following check is equivalent to:
+ *
+ * if (lzx_extra_bits[position_slot] >= 3)
+ *
+ * Note that this correctly excludes position slots that correspond to
+ * recent offsets. */
+ if (position_slot >= 8)
+ freqs->aligned[position_footer & 7]++;
+
+ /* Pack the position slot, position footer, and match length into an
+ * intermediate representation. See `struct lzx_match' for details.
+ */
+ LZX_ASSERT(LZX_MAX_POSITION_SLOTS <= 64);
+ LZX_ASSERT(lzx_get_num_extra_bits(LZX_MAX_POSITION_SLOTS - 1) <= 17);
+ LZX_ASSERT(LZX_MAX_MATCH_LEN - LZX_MIN_MATCH_LEN + 1 <= 256);
+
+ LZX_ASSERT(position_slot <= (1U << (31 - 25)) - 1);
+ LZX_ASSERT(position_footer <= (1U << (25 - 8)) - 1);
+ LZX_ASSERT(adjusted_match_len <= (1U << (8 - 0)) - 1);
+ return 0x80000000 |
+ (position_slot << 25) |
+ (position_footer << 8) |
+ (adjusted_match_len);
+}
+
+struct lzx_record_ctx {
+ struct lzx_freqs freqs;
+ struct lzx_lru_queue queue;
+ struct lzx_match *matches;
+};
+
+static void
+lzx_record_match(unsigned len, unsigned offset, void *_ctx)
+{
+ struct lzx_record_ctx *ctx = _ctx;
+
+ (ctx->matches++)->data = lzx_tally_match(len, offset, &ctx->freqs, &ctx->queue);
+}
+
+static void
+lzx_record_literal(u8 lit, void *_ctx)
+{
+ struct lzx_record_ctx *ctx = _ctx;
+
+ (ctx->matches++)->data = lzx_tally_literal(lit, &ctx->freqs);
+}
+
+/* Returns the cost, in bits, to output a literal byte using the specified cost
+ * model. */
+static unsigned
+lzx_literal_cost(u8 c, const struct lzx_costs * costs)
+{
+ return costs->main[c];
+}
+
+/* Given a (length, offset) pair that could be turned into a valid LZX match as
+ * well as costs for the codewords in the main, length, and aligned Huffman
+ * codes, return the approximate number of bits it will take to represent this
+ * match in the compressed output. Take into account the match offset LRU
+ * queue and optionally update it. */
+static unsigned
+lzx_match_cost(unsigned length, unsigned offset, const struct lzx_costs *costs,
+ struct lzx_lru_queue *queue)
+{
+ unsigned position_slot;
+ unsigned len_header, main_symbol;
+ unsigned cost = 0;
+
+ position_slot = lzx_get_position_slot(offset, queue);
- compressed_len = ostream.bit_output - (u8*)compressed_data;
+ len_header = min(length - LZX_MIN_MATCH_LEN, LZX_NUM_PRIMARY_LENS);
+ main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS;
-#ifdef ENABLE_VERIFY_COMPRESSION
- /* Verify that we really get the same thing back when decompressing. */
+ /* 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)
{
- u8 buf[uncompressed_len];
- ret = wimlib_lzx_decompress(compressed_data, compressed_len,
- buf, uncompressed_len);
- if (ret != 0) {
- ERROR("lzx_compress(): Failed to decompress data we compressed");
- abort();
+ 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;
+ }
}
- 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();
+ 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;
}
git://wimlib.net / wimlib / blobdiff