/*
* 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 Eric Biggers
+ * Copyright (C) 2012, 2013 Eric Biggers
*
* This file is part of wimlib, a library for working with WIM files.
*
/*
- * This file provides lzx_compress(), a function to compress an in-memory buffer
- * of data using LZX compression, as used in the WIM file format.
- *
- * Please see the comments in lzx-decompress.c for more information about this
- * compression format.
- *
- * One thing to keep in mind is that there is no sliding window, since the
- * window is always the entirety of a WIM chunk, which is at most WIM_CHUNK_SIZE
- * ( = 32768) bytes.
- *
- * The basic compression algorithm used here should be familiar if you are
- * familiar with Huffman trees and with other LZ77 and Huffman-based formats
- * such as DEFLATE. Otherwise it can be quite tricky to understand. Basically
- * it is the following:
- *
- * - Preprocess the input data (LZX-specific)
- * - Go through the input data and determine matches. This part is based on
- * code from zlib, and a hash table of 3-character strings is used to
- * accelerate the process of finding matches.
- * - Build the Huffman trees based on the frequencies of symbols determined
- * while recording matches.
- * - Output the block header, including the Huffman trees; then output the
- * compressed stream of matches and literal characters.
- *
- * It is possible for a WIM chunk to include multiple LZX blocks, since for some
- * input data this will produce a better compression ratio (especially since
- * each block can include new Huffman codes). However, producing multiple LZX
- * blocks from one input chunk is not yet implemented.
+ * This file contains a compressor for the LZX compression format, as used in
+ * the WIM file format.
+ *
+ * Format
+ * ======
+ *
+ * First, the primary reference for the LZX compression format is the
+ * specification released by Microsoft.
+ *
+ * Second, the comments in lzx-decompress.c provide some more information about
+ * the LZX compression format, including errors in the Microsoft specification.
+ *
+ * Do note that LZX shares many similarities with DEFLATE, the algorithm used by
+ * zlib and gzip. Both LZX and DEFLATE use LZ77 matching and Huffman coding,
+ * and certain other details are quite similar, such as the method for storing
+ * Huffman codes. However, some of the main differences are:
+ *
+ * - LZX preprocesses the data before attempting to compress it.
+ * - 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 footer" (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 a LRU queue
+ * of match offsets.
+ *
+ * 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. Determine the best known sequence of LZ77 matches ((offset, length) pairs)
+ * and literal bytes to divide the input into. Raw match-finding is done
+ * using a very clever binary tree search based on the "Bt3" algorithm from
+ * 7-Zip. Parsing, or match-choosing, is solved essentially as a
+ * minimum-cost path problem, but using a heuristic forward search based on
+ * the Deflate encoder from 7-Zip rather than a more intuitive backward
+ * search, the latter of which would naively require that all matches be
+ * found. This heuristic search, as well as other heuristics such as limits
+ * on the matches considered, considerably speed up this part of the
+ * algorithm, which is the main bottleneck. Finally, after matches and
+ * literals are chosen, the needed Huffman codes needed to output them are
+ * built.
+ *
+ * 3. Up to a certain number of iterations, use the resulting Huffman codes to
+ * refine a cost model and go back to Step #2 to determine an improved
+ * sequence of matches and literals.
+ *
+ * 4. Up to a certain depth, try splitting the current block to see if the
+ * compression ratio can be improved. This may be the case if parts of the
+ * input differ greatly from each other and could benefit from different
+ * Huffman codes.
+ *
+ * 5. Output the resulting block(s) using the match/literal sequences and the
+ * Huffman codes that were computed for each block.
+ *
+ * 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, match choosing, and block splitting. 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()
+ *
+ * Both wimlib_lzx_compress() and wimlib_lzx_compress2() are designed to
+ * compress an in-memory buffer of up to 32768 bytes. There is no sliding
+ * window. This is suitable for the WIM format, which uses fixed-size chunks
+ * that are seemingly always 32768 bytes. If needed, the compressor potentially
+ * could be extended to support a larger and/or sliding window.
+ *
+ * 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 API are exported from the library, although 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 other open-source projects that made it possible
+ * to implement this code:
+ *
+ * - 7-Zip (author: Igor Pavlov), for the binary tree match-finding
+ * algorithm, the heuristic near-optimal forward match-choosing
+ * algorithm, and the block splitting algorithm.
+ *
+ * - zlib (author: Jean-loup Gailly and Mark Adler), for the hash table
+ * match-finding algorithm.
+ *
+ * - lzx-compress (author: Matthew T. Russotto), on which some parts of this
+ * code were originally based.
*/
-#include "lzx.h"
-#include "compress.h"
-#include <stdlib.h>
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include "wimlib.h"
+#include "wimlib/compress.h"
+#include "wimlib/error.h"
+#include "wimlib/lzx.h"
+#include "wimlib/util.h"
+
+#ifdef ENABLE_LZX_DEBUG
+# include <wimlib/decompress.h>
+#endif
+
#include <string.h>
+/* Experimental parameters not exposed through the API */
+#define LZX_PARAM_OPTIM_ARRAY_SIZE 1024
+#define LZX_PARAM_ACCOUNT_FOR_LRU 1
+#define LZX_PARAM_DONT_SKIP_MATCHES 0
+#define LZX_PARAM_USE_EMPIRICAL_DEFAULT_COSTS 1
+
+/* Currently, this constant can't simply be changed because the code currently
+ * uses a static number of position slots (and may make other assumptions as
+ * well). */
+#define LZX_MAX_WINDOW_SIZE 32768
+
+/* This may be WIM-specific */
+#define LZX_DEFAULT_BLOCK_SIZE 32768
+
+#define LZX_LZ_HASH_BITS 15
+#define LZX_LZ_HASH_SIZE (1 << LZX_LZ_HASH_BITS)
+#define LZX_LZ_HASH_MASK (LZX_LZ_HASH_SIZE - 1)
+#define LZX_LZ_HASH_SHIFT 5
+
+/* Codewords for the LZX main, length, and aligned offset Huffman codes */
+struct lzx_codewords {
+ u16 main[LZX_MAINTREE_NUM_SYMBOLS];
+ u16 len[LZX_LENTREE_NUM_SYMBOLS];
+ u16 aligned[LZX_ALIGNEDTREE_NUM_SYMBOLS];
+};
+
+/* Lengths for the LZX main, length, and aligned offset Huffman codes */
+struct lzx_lens {
+ u8 main[LZX_MAINTREE_NUM_SYMBOLS];
+ u8 len[LZX_LENTREE_NUM_SYMBOLS];
+ u8 aligned[LZX_ALIGNEDTREE_NUM_SYMBOLS];
+};
-/* Structure to contain the Huffman codes for the main, length, and aligned
- * offset trees. */
+/* The LZX main, length, and aligned offset Huffman codes */
struct lzx_codes {
- u16 main_codewords[LZX_MAINTREE_NUM_SYMBOLS];
- u8 main_lens[LZX_MAINTREE_NUM_SYMBOLS];
+ struct lzx_codewords codewords;
+ struct lzx_lens lens;
+};
+
+/* Tables for tallying symbol frequencies in the three LZX alphabets */
+struct lzx_freqs {
+ freq_t main[LZX_MAINTREE_NUM_SYMBOLS];
+ freq_t len[LZX_LENTREE_NUM_SYMBOLS];
+ freq_t aligned[LZX_ALIGNEDTREE_NUM_SYMBOLS];
+};
+
+/* LZX intermediate match/literal format */
+struct lzx_match {
+ /* Bit Description
+ *
+ * 31 1 if a match, 0 if a literal.
+ *
+ * 30-25 position slot. This can be at most 50, so it will fit in 6
+ * bits.
+ *
+ * 8-24 position footer. This is the offset of the real formatted
+ * offset from the position base. This can be at most 17 bits
+ * (since lzx_extra_bits[LZX_NUM_POSITION_SLOTS - 1] is 17).
+ *
+ * 0-7 length of match, minus 2. This can be at most
+ * (LZX_MAX_MATCH - 2) == 255, so it will fit in 8 bits. */
+ u32 data;
+};
+
+/* Raw LZ match/literal format: just a length and offset.
+ *
+ * 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 matched text.
+ *
+ * If @len < LZX_MIN_MATCH, then it's really just a literal byte and @offset is
+ * meaningless. */
+struct raw_match {
+ u16 len;
+ u16 offset;
+};
+
+/* Specification for a LZX block */
+struct lzx_block_spec {
+
+ /* Set to 1 if this block has been split (in two --- we only considser
+ * binary splits). In such cases the rest of the fields are
+ * unimportant, since the relevant information is rather in the
+ * structures for the sub-blocks. */
+ u8 is_split : 1;
+
+ /* One of the LZX_BLOCKTYPE_* constants indicating which type of this
+ * block. */
+ u8 block_type : 2;
+
+ /* 0-based position in the window at which this block starts. */
+ u16 window_pos;
+
+ /* The number of bytes of uncompressed data this block represents. */
+ u16 block_size;
+
+ /* The position in the 'chosen_matches' array in the `struct
+ * lzx_compressor' at which the match/literal specifications for
+ * this block begin. */
+ unsigned chosen_matches_start_pos;
+
+ /* The number of match/literal specifications for this block. */
+ u16 num_chosen_matches;
- u16 len_codewords[LZX_LENTREE_NUM_SYMBOLS];
- u8 len_lens[LZX_LENTREE_NUM_SYMBOLS];
+ /* Huffman codes for this block. */
+ struct lzx_codes codes;
+};
- u16 aligned_codewords[LZX_ALIGNEDTREE_NUM_SYMBOLS];
- u8 aligned_lens[LZX_ALIGNEDTREE_NUM_SYMBOLS];
+/*
+ * 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. */
+ u32 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. */
+ u16 link;
+
+ /* Offset (as in a LZ (length, offset) pair) of the
+ * match or literal that was taken to get to this
+ * position in the approximate minimum-cost parse. */
+ u16 match_offset;
+ } prev;
+ struct {
+ /* Position at which the match or literal starting at
+ * this position ends in the minimum-cost parse. */
+ u16 link;
+
+ /* Offset (as in a LZ (length, offset) pair) of the
+ * match or literal starting at this position in the
+ * approximate minimum-cost parse. */
+ u16 match_offset;
+ } next;
+ };
+#if LZX_PARAM_ACCOUNT_FOR_LRU
+ struct lzx_lru_queue queue;
+#endif
};
-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];
+/* 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.
+ *
+ * 0xe8 byte preprocessing is done directly on the data here before
+ * further compression.
+ *
+ * Note that this compressor does *not* use a sliding window!!!!
+ * It's not needed in the WIM format, since every chunk is compressed
+ * independently. This is by design, to allow random access to the
+ * chunks.
+ *
+ * We reserve a few extra bytes to potentially allow reading off the end
+ * of the array in the match-finding code for optimization purposes.
+ */
+ u8 window[LZX_MAX_WINDOW_SIZE + 12];
+
+ /* Number of bytes of data to be compressed, which is the number of
+ * bytes of data in @window that are actually valid. */
+ unsigned window_size;
+
+ /* The current match offset LRU queue. */
+ struct lzx_lru_queue queue;
+
+ /* Space for sequence of matches/literals that were chosen.
+ *
+ * Each LZX_MAX_WINDOW_SIZE-sized portion of this array is used for a
+ * different block splitting level. */
+ struct lzx_match *chosen_matches;
+
+ /* Structures used during block splitting.
+ *
+ * This can be thought of as a binary tree. block_specs[(1) - 1]
+ * represents to the top-level block (root node), and block_specs[(i*2)
+ * - 1] and block_specs[(i*2+1) - 1] represent the sub-blocks (child
+ * nodes) resulting from a binary split of the block represented by
+ * block_spec[(i) - 1].
+ */
+ struct lzx_block_spec *block_specs;
+
+ /* 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;
+
+ /* Slow algorithm only: The current cost model. */
+ struct lzx_lens costs;
+
+ /* Slow algorithm only: Table that maps the hash codes for 3 character
+ * sequences to the most recent position that sequence (or a sequence
+ * sharing the same hash code) appeared in the window. */
+ u16 *hash_tab;
+
+ /* Slow algorithm only: Table that maps 2-character sequences to the
+ * most recent position that sequence appeared in the window. */
+ u16 *digram_tab;
+
+ /* Slow algorithm only: Table that contains the logical child pointers
+ * in the binary trees in the match-finding code.
+ *
+ * child_tab[i*2] and child_tab[i*2+1] are the left and right pointers,
+ * respectively, from the binary tree root corresponding to window
+ * position i. */
+ u16 *child_tab;
+
+ /* Slow algorithm only: Matches that were already found and are saved in
+ * memory for subsequent queries (e.g. when block splitting). */
+ struct raw_match *cached_matches;
+
+ /* Slow algorithm only: Next position in 'cached_matches' to either
+ * return or fill in. */
+ unsigned cached_matches_pos;
+
+ /* Slow algorithm only: %true if reading from 'cached_matches'; %false
+ * if writing to 'cached_matches'. */
+ bool matches_already_found;
+
+ /* Slow algorithm only: Position in window of next match to return. */
+ unsigned match_window_pos;
+
+ /* Slow algorithm only: No matches returned shall reach past this
+ * position. */
+ unsigned match_window_end;
+
+ /* Slow algorithm only: Temporary space used for match-choosing
+ * algorithm.
+ *
+ * The size of this array must be at least LZX_MAX_MATCH but otherwise
+ * is arbitrary. More space simply allows the match-choosing algorithm
+ * to find better matches (depending on the input, as always). */
+ struct lzx_optimal *optimum;
+
+ /* Slow algorithm only: Variables used by the match-choosing algorithm.
+ *
+ * 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 formatted offset.
* 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)
+static unsigned
+lzx_get_position_slot(unsigned formatted_offset)
{
#if 0
/*
* 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);
+ LZX_ASSERT(2 <= formatted_offset && formatted_offset < 655360);
unsigned mssb_idx = bsr32(formatted_offset);
return (mssb_idx << 1) |
((formatted_offset >> (mssb_idx - 1)) & 1);
}
}
-static u32 lzx_record_literal(u8 literal, void *__main_freq_tab)
+/* Compute the hash code for the next 3-character sequence in the window. */
+static unsigned
+lzx_lz_compute_hash(const u8 *window)
{
- freq_t *main_freq_tab = __main_freq_tab;
- main_freq_tab[literal]++;
- return literal;
+ unsigned hash;
+
+ hash = window[0];
+ hash <<= LZX_LZ_HASH_SHIFT;
+ hash ^= window[1];
+ hash <<= LZX_LZ_HASH_SHIFT;
+ hash ^= window[2];
+ return hash & LZX_LZ_HASH_MASK;
}
-/* 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)
+/* 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 lengths. */
+static void
+lzx_make_huffman_codes(const struct lzx_freqs *freqs,
+ struct lzx_codes *codes)
{
- 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;
-
- 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. */
-
- /* 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;
-
- queue->R2 = queue->R1;
- queue->R1 = queue->R0;
- queue->R0 = match_offset;
-
- /* 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. */
-
- position_slot = lzx_get_position_slot(formatted_offset);
- position_footer = formatted_offset &
- ((1 << lzx_get_num_extra_bits(position_slot)) - 1);
- }
-
- adjusted_match_len = match_len - LZX_MIN_MATCH;
-
- /* Pack the position slot, position footer, and match length into an
- * intermediate representation.
- *
- * bits 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_NUM_POSITION_SLOTS - 1] is 17).
- *
- * 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 match length must be at least 2, so let the adjusted match length
- * be the match length minus 2.
- *
- * 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]++;
- }
- len_pos_header = (position_slot << 3) | len_header;
-
- wimlib_assert(len_pos_header < LZX_MAINTREE_NUM_SYMBOLS - LZX_NUM_CHARS);
-
- freq_tabs->main_freq_table[len_pos_header + LZX_NUM_CHARS]++;
+ make_canonical_huffman_code(LZX_MAINTREE_NUM_SYMBOLS,
+ LZX_MAX_CODEWORD_LEN,
+ freqs->main,
+ codes->lens.main,
+ codes->codewords.main);
- /* Equivalent to:
- * if (lzx_extra_bits[position_slot] >= 3) */
- if (position_slot >= 8)
- freq_tabs->aligned_freq_table[position_footer & 7]++;
+ make_canonical_huffman_code(LZX_LENTREE_NUM_SYMBOLS,
+ LZX_MAX_CODEWORD_LEN,
+ freqs->len,
+ codes->lens.len,
+ codes->codewords.len);
- return match;
+ make_canonical_huffman_code(LZX_ALIGNEDTREE_NUM_SYMBOLS, 8,
+ freqs->aligned,
+ codes->lens.aligned,
+ codes->codewords.aligned);
}
/*
- * Writes a compressed literal match to the output.
+ * Output a LZX match.
*
- * @out: The output bitstream.
- * @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM)
- * @match: The match, encoded as a 32-bit number.
- * @codes: Pointer to a structure that contains the codewords for the
- * main, length, and aligned offset Huffman codes.
+ * @out: The bitstream to write the match to.
+ * @block_type: The type of the LZX block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM)
+ * @match: The match.
+ * @codes: Pointer to a structure that contains the codewords for the
+ * main, length, and aligned offset Huffman codes.
*/
-static int lzx_write_match(struct output_bitstream *out, int block_type,
- u32 match, const struct lzx_codes *codes)
+static void
+lzx_write_match(struct output_bitstream *out, int block_type,
+ struct lzx_match match, const struct lzx_codes *codes)
{
/* low 8 bits are the match length minus 2 */
- unsigned match_len_minus_2 = match & 0xff;
+ unsigned match_len_minus_2 = match.data & 0xff;
/* Next 17 bits are the position footer */
- unsigned position_footer = (match >> 8) & 0x1ffff; /* 17 bits */
+ unsigned position_footer = (match.data >> 8) & 0x1ffff; /* 17 bits */
/* Next 6 bits are the position slot. */
- unsigned position_slot = (match >> 25) & 0x3f; /* 6 bits */
+ unsigned position_slot = (match.data >> 25) & 0x3f; /* 6 bits */
unsigned len_header;
unsigned len_footer;
unsigned len_pos_header;
unsigned num_extra_bits;
unsigned verbatim_bits;
unsigned aligned_bits;
- int ret;
/* If the match length is less than MIN_MATCH (= 2) +
* NUM_PRIMARY_LENS (= 7), the length header contains
main_symbol = len_pos_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
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],
+ unsigned num_syms,
+ freq_t precode_freqs[restrict LZX_PRETREE_NUM_SYMBOLS],
+ u8 output_syms[restrict num_syms],
+ u8 precode_lens[restrict LZX_PRETREE_NUM_SYMBOLS],
+ u16 precode_codewords[restrict LZX_PRETREE_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;
+ signed char delta;
+ unsigned num_additional_bits = 0;
- ZERO_ARRAY(pretree_freqs);
+ memset(precode_freqs, 0,
+ LZX_PRETREE_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
*/
output_syms_idx = 0;
cur_run_len = 1;
- for (i = 1; i <= num_symbols; i++) {
+ for (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;
while (cur_run_len >= 20) {
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;
* follows the magic length. */
while (cur_run_len >= 4) {
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
* */
while (cur_run_len >= 4) {
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;
+ while (cur_run_len > 0) {
+ 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);
+ precode_freqs, precode_lens,
+ precode_codewords);
+
+ if (num_additional_bits_ret)
+ *num_additional_bits_ret = num_additional_bits;
- /* Write the lengths of the pretree codes to the output. */
+ return output_syms_idx;
+}
+
+/*
+ * 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_PRETREE_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)
+{
+ freq_t precode_freqs[LZX_PRETREE_NUM_SYMBOLS];
+ u8 output_syms[num_syms];
+ u8 precode_lens[LZX_PRETREE_NUM_SYMBOLS];
+ u16 precode_codewords[LZX_PRETREE_NUM_SYMBOLS];
+ unsigned i;
+ unsigned num_output_syms;
+ u8 precode_sym;
+
+ num_output_syms = lzx_build_precode(lens,
+ prev_lens,
+ num_syms,
+ precode_freqs,
+ output_syms,
+ precode_lens,
+ precode_codewords,
+ NULL);
+
+ /* Write the lengths of the precode codes to the output. */
for (i = 0; i < LZX_PRETREE_NUM_SYMBOLS; i++)
- bitstream_put_bits(out, pretree_lens[i],
+ bitstream_put_bits(out, precode_lens[i],
LZX_PRETREE_ELEMENT_SIZE);
- /* Write the length symbols, encoded with the pretree, to the output. */
+ /* Write the length symbols, encoded with the precode, to the output. */
- i = 0;
- while (i < output_syms_idx) {
- pretree_sym = output_syms[i++];
+ for (i = 0; i < num_output_syms; ) {
+ precode_sym = output_syms[i++];
- bitstream_put_bits(out, pretree_codewords[pretree_sym],
- pretree_lens[pretree_sym]);
- switch (pretree_sym) {
+ 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);
}
-static void do_call_insn_translation(u32 *call_insn_target, int input_pos,
- int32_t file_size)
+/*
+ * Writes all compressed matches and literal bytes in a LZX block to the the
+ * output bitstream.
+ *
+ * @ostream
+ * The output bitstream.
+ * @block_type
+ * The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM).
+ * @match_tab
+ * The array of matches/literals that will be output (length @match_count).
+ * @match_count
+ * Number of matches/literals to be output.
+ * @codes
+ * Pointer to a structure that contains the codewords for the main, length,
+ * and aligned offset Huffman codes.
+ */
+static void
+lzx_write_matches_and_literals(struct output_bitstream *ostream,
+ int block_type,
+ const struct lzx_match match_tab[],
+ unsigned match_count,
+ const struct lzx_codes *codes)
{
- int32_t abs_offset;
- int32_t rel_offset;
+ for (unsigned i = 0; i < match_count; i++) {
+ struct lzx_match match = match_tab[i];
- rel_offset = le32_to_cpu(*call_insn_target);
- if (rel_offset >= -input_pos && rel_offset < file_size) {
- if (rel_offset < file_size - input_pos) {
- /* "good translation" */
- abs_offset = rel_offset + input_pos;
+ /* High bit of the match indicates whether the match is an
+ * actual match (1) or a literal uncompressed byte (0) */
+ if (match.data & 0x80000000) {
+ /* match */
+ lzx_write_match(ostream, block_type,
+ match, codes);
} else {
- /* "compensating translation" */
- abs_offset = rel_offset - file_size;
+ /* literal byte */
+ bitstream_put_bits(ostream,
+ codes->codewords.main[match.data],
+ codes->lens.main[match.data]);
}
- *call_insn_target = cpu_to_le32(abs_offset);
}
}
-/* This is the reverse of undo_call_insn_preprocessing() in lzx-decompress.c.
- * See the comment above that function for more information. */
-static void do_call_insn_preprocessing(u8 uncompressed_data[],
- int uncompressed_data_len)
-{
- for (int i = 0; i < uncompressed_data_len - 10; i++) {
- if (uncompressed_data[i] == 0xe8) {
- do_call_insn_translation((u32*)&uncompressed_data[i + 1],
- i,
- LZX_WIM_MAGIC_FILESIZE);
- i += 4;
- }
- }
-}
+static void
+lzx_assert_codes_valid(const struct lzx_codes * codes)
+{
+#ifdef ENABLE_LZX_DEBUG
+ unsigned i;
+
+ for (i = 0; i < LZX_MAINTREE_NUM_SYMBOLS; i++)
+ LZX_ASSERT(codes->lens.main[i] <= LZX_MAX_CODEWORD_LEN);
+
+ for (i = 0; i < LZX_LENTREE_NUM_SYMBOLS; i++)
+ LZX_ASSERT(codes->lens.len[i] <= LZX_MAX_CODEWORD_LEN);
+
+ for (i = 0; i < LZX_ALIGNEDTREE_NUM_SYMBOLS; i++)
+ LZX_ASSERT(codes->lens.aligned[i] <= 8);
+
+ const unsigned tablebits = 10;
+ u16 decode_table[(1 << tablebits) +
+ (2 * max(LZX_MAINTREE_NUM_SYMBOLS, LZX_LENTREE_NUM_SYMBOLS))]
+ _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+ LZX_ASSERT(0 == make_huffman_decode_table(decode_table,
+ LZX_MAINTREE_NUM_SYMBOLS,
+ tablebits,
+ codes->lens.main,
+ LZX_MAX_CODEWORD_LEN));
+ LZX_ASSERT(0 == make_huffman_decode_table(decode_table,
+ LZX_LENTREE_NUM_SYMBOLS,
+ tablebits,
+ codes->lens.len,
+ LZX_MAX_CODEWORD_LEN));
+ LZX_ASSERT(0 == make_huffman_decode_table(decode_table,
+ LZX_ALIGNEDTREE_NUM_SYMBOLS,
+ min(tablebits, 6),
+ codes->lens.aligned,
+ 8));
+#endif /* ENABLE_LZX_DEBUG */
+}
+
+/* Write a LZX aligned offset or verbatim block to the output. */
+static void
+lzx_write_compressed_block(int block_type,
+ unsigned block_size,
+ struct lzx_match * chosen_matches,
+ unsigned num_chosen_matches,
+ const struct lzx_codes * codes,
+ const struct lzx_codes * prev_codes,
+ struct output_bitstream * ostream)
+{
+ unsigned i;
+
+ LZX_ASSERT(block_type == LZX_BLOCKTYPE_ALIGNED ||
+ block_type == LZX_BLOCKTYPE_VERBATIM);
+ LZX_ASSERT(block_size <= LZX_MAX_WINDOW_SIZE);
+ LZX_ASSERT(num_chosen_matches <= LZX_MAX_WINDOW_SIZE);
+ lzx_assert_codes_valid(codes);
+
+ /* The first three bits indicate the type of block and are one of the
+ * LZX_BLOCKTYPE_* constants. */
+ bitstream_put_bits(ostream, block_type, LZX_BLOCKTYPE_NBITS);
+
+ /* 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 (block_size == LZX_DEFAULT_BLOCK_SIZE) {
+ bitstream_put_bits(ostream, 1, 1);
+ } else {
+ bitstream_put_bits(ostream, 0, 1);
+ bitstream_put_bits(ostream, block_size, LZX_BLOCKSIZE_NBITS);
+ }
+
+ /* 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 tree 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->lens.aligned[i],
+ LZX_ALIGNEDTREE_ELEMENT_SIZE);
+
+ LZX_DEBUG("Writing main code...");
+
+ /* Write the pre-tree 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 pre-tree 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,
+ LZX_MAINTREE_NUM_SYMBOLS - LZX_NUM_CHARS);
+
+ LZX_DEBUG("Writing length code...");
+
+ /* Write the pre-tree and lengths for the length code. */
+ lzx_write_compressed_code(ostream,
+ codes->lens.len,
+ prev_codes->lens.len,
+ LZX_LENTREE_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 LZX block of index @block_number, or write its children recursively
+ * if it is a split block.
+ *
+ * @prev_codes is a pointer to the Huffman codes for the most recent block
+ * written, or all zeroes if this is the first block.
+ *
+ * Return a pointer to the Huffman codes for the last block written. */
+static struct lzx_codes *
+lzx_write_block_recursive(struct lzx_compressor *ctx,
+ unsigned block_number,
+ struct lzx_codes * prev_codes,
+ struct output_bitstream *ostream)
+{
+ struct lzx_block_spec *spec = &ctx->block_specs[block_number - 1];
+
+ if (spec->is_split) {
+ prev_codes = lzx_write_block_recursive(ctx, block_number * 2 + 0,
+ prev_codes, ostream);
+ prev_codes = lzx_write_block_recursive(ctx, block_number * 2 + 1,
+ prev_codes, ostream);
+ } else {
+ LZX_DEBUG("Writing block #%u (type=%d, size=%u, num_chosen_matches=%u)...",
+ block_number, spec->block_type, spec->block_size,
+ spec->num_chosen_matches);
+ lzx_write_compressed_block(spec->block_type,
+ spec->block_size,
+ &ctx->chosen_matches[spec->chosen_matches_start_pos],
+ spec->num_chosen_matches,
+ &spec->codes,
+ prev_codes,
+ ostream);
+ prev_codes = &spec->codes;
+ }
+ return prev_codes;
+}
+
+/* Write out the LZX blocks that were computed. */
+static void
+lzx_write_all_blocks(struct lzx_compressor *ctx, struct output_bitstream *ostream)
+{
+ lzx_write_block_recursive(ctx, 1, &ctx->zero_codes, ostream);
+}
+
+static u32
+lzx_record_literal(u8 literal, void *_freqs)
+{
+ struct lzx_freqs *freqs = _freqs;
+
+ freqs->main[literal]++;
+
+ return (u32)literal;
+}
+
+/* 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 *_freqs, void *_queue)
+{
+ struct lzx_freqs *freqs = _freqs;
+ struct lzx_lru_queue *queue = _queue;
+ unsigned position_slot;
+ unsigned position_footer = 0;
+ u32 len_header;
+ u32 len_pos_header;
+ unsigned len_footer;
+ unsigned adjusted_match_len;
+
+ LZX_ASSERT(match_len >= LZX_MIN_MATCH && match_len <= LZX_MAX_MATCH);
+
+ /* 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. */
+
+ /* 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 + 2;
+
+ queue->R2 = queue->R1;
+ queue->R1 = queue->R0;
+ queue->R0 = match_offset;
+
+ /* 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. */
+
+ position_slot = lzx_get_position_slot(formatted_offset);
+ position_footer = formatted_offset &
+ ((1 << lzx_get_num_extra_bits(position_slot)) - 1);
+ }
+
+ adjusted_match_len = match_len - LZX_MIN_MATCH;
+
+
+ /* The match length must be at least 2, so let the adjusted match length
+ * be the match length minus 2.
+ *
+ * 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;
+ freqs->len[len_footer]++;
+ }
+ len_pos_header = (position_slot << 3) | len_header;
+
+ freqs->main[len_pos_header + LZX_NUM_CHARS]++;
+
+ /* Equivalent to:
+ * if (lzx_extra_bits[position_slot] >= 3) */
+ if (position_slot >= 8)
+ freqs->aligned[position_footer & 7]++;
+
+ /* Pack the position slot, position footer, and match length into an
+ * intermediate representation.
+ *
+ * bits 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_NUM_POSITION_SLOTS - 1] is 17).
+ *
+ * 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. */
+ return 0x80000000 |
+ (position_slot << 25) |
+ (position_footer << 8) |
+ (adjusted_match_len);
+}
+
+/* Set the cost model @ctx->costs from the Huffman codeword lengths specified in
+ * @lens.
+ *
+ * These are basically the same thing, except that 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;
+
+ memcpy(&ctx->costs, lens, sizeof(struct lzx_lens));
+
+ for (i = 0; i < LZX_MAINTREE_NUM_SYMBOLS; i++)
+ if (ctx->costs.main[i] == 0)
+ ctx->costs.main[i] = ctx->params.slow.main_nostat_cost;
+
+ for (i = 0; i < LZX_LENTREE_NUM_SYMBOLS; i++)
+ if (ctx->costs.len[i] == 0)
+ ctx->costs.len[i] = ctx->params.slow.len_nostat_cost;
+
+ for (i = 0; i < LZX_ALIGNEDTREE_NUM_SYMBOLS; i++)
+ if (ctx->costs.aligned[i] == 0)
+ ctx->costs.aligned[i] = ctx->params.slow.aligned_nostat_cost;
+}
+
+static u32
+lzx_literal_cost(u8 c, const struct lzx_lens * 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. */
+static unsigned
+lzx_match_cost(unsigned length, unsigned offset, const struct lzx_lens *costs
+
+#if LZX_PARAM_ACCOUNT_FOR_LRU
+ , struct lzx_lru_queue *queue
+#endif
+ )
+{
+ unsigned position_slot, len_header, main_symbol;
+ unsigned cost = 0;
+
+ /* Calculate position slot and length header, then combine them into the
+ * main symbol. */
+
+#if LZX_PARAM_ACCOUNT_FOR_LRU
+ if (offset == queue->R0) {
+ position_slot = 0;
+ } else if (offset == queue->R1) {
+ swap(queue->R0, queue->R1);
+ position_slot = 1;
+ } else if (offset == queue->R2) {
+ swap(queue->R0, queue->R2);
+ position_slot = 2;
+ } else
+#endif
+ position_slot = lzx_get_position_slot(offset + 2);
+
+ len_header = min(length - LZX_MIN_MATCH, LZX_NUM_PRIMARY_LENS);
+ main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS;
+
+ /* Account for main symbol. */
+ cost += costs->main[main_symbol];
+
+ /* Account for extra position information. */
+ unsigned num_extra_bits = lzx_get_num_extra_bits(position_slot);
+ if (num_extra_bits >= 3) {
+ cost += num_extra_bits - 3;
+ cost += costs->aligned[(offset + LZX_MIN_MATCH) & 7];
+ } else {
+ cost += num_extra_bits;
+ }
+
+ /* Account for extra length information. */
+ if (length - LZX_MIN_MATCH >= LZX_NUM_PRIMARY_LENS)
+ cost += costs->len[length - LZX_MIN_MATCH - LZX_NUM_PRIMARY_LENS];
+
+ return cost;
+}
+
+/* This procedure effectively creates a new binary tree corresponding to the
+ * current string at the same time that it searches the existing tree nodes for
+ * matches. This is the same algorithm as that used in GetMatchesSpec1() in
+ * 7-Zip, but it is hopefully explained a little more clearly below. */
+static unsigned
+lzx_lz_get_matches(const u8 window[restrict],
+ const unsigned bytes_remaining,
+ const unsigned strstart,
+ const unsigned max_length,
+ u16 child_tab[restrict],
+ unsigned cur_match,
+ const unsigned prev_len,
+ struct raw_match * const matches)
+{
+ u16 *new_tree_lt_ptr = &child_tab[strstart * 2];
+ u16 *new_tree_gt_ptr = &child_tab[strstart * 2 + 1];
+
+ u16 longest_lt_match_len = 0;
+ u16 longest_gt_match_len = 0;
+
+ /* Maximum number of nodes to walk down before stopping */
+ unsigned depth = max_length;
+
+ /* Length of longest match found so far */
+ unsigned longest_match_len = prev_len;
+
+ /* Maximum length of match to return */
+ unsigned len_limit = min(bytes_remaining, max_length);
+
+ /* Number of matches found so far */
+ unsigned num_matches = 0;
+
+ for (;;) {
+
+ /* Stop if too many nodes were traversed or if there is no next
+ * node */
+ if (depth-- == 0 || cur_match == 0) {
+ *new_tree_gt_ptr = 0;
+ *new_tree_lt_ptr = 0;
+ return num_matches;
+ }
+
+ /* Load the pointers to the children of the binary tree node
+ * corresponding to the current match */
+ u16 * const cur_match_ptrs = &child_tab[cur_match * 2];
+
+ /* Set up pointers to the current match and to the current
+ * string */
+ const u8 * const matchptr = &window[cur_match];
+ const u8 * const strptr = &window[strstart];
+
+ /* Determine position at which to start comparing */
+ u16 len = min(longest_lt_match_len,
+ longest_gt_match_len);
+
+ if (matchptr[len] == strptr[len]) {
+
+ /* Extend the match as far as possible. */
+ while (++len != len_limit)
+ if (matchptr[len] != strptr[len])
+ break;
+
+ /* Record this match if it is the longest found so far.
+ */
+ if (len > longest_match_len) {
+ longest_match_len = len;
+ matches[num_matches].len = len;
+ matches[num_matches].offset = strstart - cur_match;
+ num_matches++;
+
+ if (len == len_limit) {
+ /* Length limit was reached. Link left pointer
+ * in the new tree with left subtree of current
+ * match tree, and link the right pointer in the
+ * new tree with the right subtree of the
+ * current match tree. This in effect deletes
+ * the node for the currrent match, which is
+ * desirable because the current match is the
+ * same as the current string up until the
+ * length limit, so in subsequent queries it
+ * will never be preferable to the current
+ * position. */
+ *new_tree_lt_ptr = cur_match_ptrs[0];
+ *new_tree_gt_ptr = cur_match_ptrs[1];
+ return num_matches;
+ }
+ }
+ }
+
+ if (matchptr[len] < strptr[len]) {
+ /* Case 1: The current match is lexicographically less
+ * than the current string.
+ *
+ * Since we are searching the binary tree structures, we
+ * need to walk down to the *right* subtree of the
+ * current match's node to get to a match that is
+ * lexicographically *greater* than the current match
+ * but still lexicographically *lesser* than the current
+ * string.
+ *
+ * At the same time, we link the entire binary tree
+ * corresponding to the current match into the
+ * appropriate place in the new binary tree being built
+ * for the current string. */
+ *new_tree_lt_ptr = cur_match;
+ new_tree_lt_ptr = &cur_match_ptrs[1];
+ cur_match = *new_tree_lt_ptr;
+ longest_lt_match_len = len;
+ } else {
+ /* Case 2: The current match is lexicographically
+ * greater than the current string.
+ *
+ * This is analogous to Case 1 above, but everything
+ * happens in the other direction.
+ */
+ *new_tree_gt_ptr = cur_match;
+ new_tree_gt_ptr = &cur_match_ptrs[0];
+ cur_match = *new_tree_gt_ptr;
+ longest_gt_match_len = len;
+ }
+ }
+}
+
+/* Equivalent to lzx_lz_get_matches(), but only updates the tree and doesn't
+ * return matches. See that function for details (including comments). */
+static void
+lzx_lz_skip_matches(const u8 window[restrict],
+ const unsigned bytes_remaining,
+ const unsigned strstart,
+ const unsigned max_length,
+ u16 child_tab[restrict],
+ unsigned cur_match,
+ const unsigned prev_len)
+{
+ u16 *new_tree_lt_ptr = &child_tab[strstart * 2];
+ u16 *new_tree_gt_ptr = &child_tab[strstart * 2 + 1];
+
+ u16 longest_lt_match_len = 0;
+ u16 longest_gt_match_len = 0;
+
+ unsigned depth = max_length;
+
+ unsigned longest_match_len = prev_len;
+
+ unsigned len_limit = min(bytes_remaining, max_length);
+
+ for (;;) {
+ if (depth-- == 0 || cur_match == 0) {
+ *new_tree_gt_ptr = 0;
+ *new_tree_lt_ptr = 0;
+ return;
+ }
+
+ u16 * const cur_match_ptrs = &child_tab[cur_match * 2];
+
+ const u8 * const matchptr = &window[cur_match];
+ const u8 * const strptr = &window[strstart];
+
+ u16 len = min(longest_lt_match_len,
+ longest_gt_match_len);
+
+ if (matchptr[len] == strptr[len]) {
+ while (++len != len_limit)
+ if (matchptr[len] != strptr[len])
+ break;
+
+ if (len > longest_match_len) {
+ longest_match_len = len;
+
+ if (len == len_limit) {
+ *new_tree_lt_ptr = cur_match_ptrs[0];
+ *new_tree_gt_ptr = cur_match_ptrs[1];
+ return;
+ }
+ }
+ }
+
+ if (matchptr[len] < strptr[len]) {
+ *new_tree_lt_ptr = cur_match;
+ new_tree_lt_ptr = &cur_match_ptrs[1];
+ cur_match = *new_tree_lt_ptr;
+ longest_lt_match_len = len;
+ } else {
+ *new_tree_gt_ptr = cur_match;
+ new_tree_gt_ptr = &cur_match_ptrs[0];
+ cur_match = *new_tree_gt_ptr;
+ longest_gt_match_len = len;
+ }
+ }
+}
+
+static unsigned
+lzx_lz_get_matches_caching(struct lzx_compressor *ctx,
+ struct raw_match **matches_ret);
+
+/* 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)
+{
+
+#if LZX_PARAM_DONT_SKIP_MATCHES
+ /* Option 1: Still cache the matches from the positions skipped. They
+ * will then be available in later passes. */
+ struct raw_match *matches;
+ while (n--)
+ lzx_lz_get_matches_caching(ctx, &matches);
+#else
+ /* Option 2: Mark the positions skipped as having no matches available,
+ * but we still need to update the binary tree in case subsequent
+ * positions have matches at the current position. */
+ LZX_ASSERT(n <= ctx->match_window_end - ctx->match_window_pos);
+ if (ctx->matches_already_found) {
+ while (n--) {
+ LZX_ASSERT(ctx->cached_matches[ctx->cached_matches_pos].offset ==
+ ctx->match_window_pos);
+ ctx->cached_matches_pos += ctx->cached_matches[ctx->cached_matches_pos].len + 1;
+ ctx->match_window_pos++;
+ }
+ } else {
+ while (n--) {
+ if (ctx->params.slow.use_len2_matches &&
+ ctx->match_window_end - ctx->match_window_pos >= 2) {
+ unsigned c1 = ctx->window[ctx->match_window_pos];
+ unsigned c2 = ctx->window[ctx->match_window_pos + 1];
+ unsigned digram = c1 | (c2 << 8);
+ ctx->digram_tab[digram] = ctx->match_window_pos;
+ }
+ if (ctx->match_window_end - ctx->match_window_pos >= 3) {
+ unsigned hash;
+ unsigned cur_match;
+
+ hash = lzx_lz_compute_hash(&ctx->window[ctx->match_window_pos]);
+
+ cur_match = ctx->hash_tab[hash];
+ ctx->hash_tab[hash] = ctx->match_window_pos;
+
+ lzx_lz_skip_matches(ctx->window,
+ ctx->match_window_end - ctx->match_window_pos,
+ ctx->match_window_pos,
+ ctx->params.slow.num_fast_bytes,
+ ctx->child_tab,
+ cur_match, 1);
+ }
+ ctx->cached_matches[ctx->cached_matches_pos].len = 0;
+ ctx->cached_matches[ctx->cached_matches_pos].offset = ctx->match_window_pos;
+ ctx->cached_matches_pos++;
+ ctx->match_window_pos++;
+ }
+ }
+#endif /* !LZX_PARAM_DONT_SKIP_MATCHES */
+}
+
+/* Retrieve a list of matches available at the next position in the input.
+ *
+ * The return value is the number of matches found, and a pointer to them is
+ * written to @matches_ret. The matches will be sorted in order by length.
+ *
+ * This is essentially a wrapper around lzx_lz_get_matches() that caches its
+ * output the first time and also performs the needed hashing.
+ */
+static unsigned
+lzx_lz_get_matches_caching(struct lzx_compressor *ctx,
+ struct raw_match **matches_ret)
+{
+ unsigned num_matches;
+ struct raw_match *matches;
+
+ LZX_ASSERT(ctx->match_window_end >= ctx->match_window_pos);
+
+ matches = &ctx->cached_matches[ctx->cached_matches_pos + 1];
+
+ if (ctx->matches_already_found) {
+ num_matches = ctx->cached_matches[ctx->cached_matches_pos].len;
+ LZX_ASSERT(ctx->cached_matches[ctx->cached_matches_pos].offset == ctx->match_window_pos);
+
+ for (int i = (int)num_matches - 1; i >= 0; i--) {
+ if (ctx->match_window_pos + matches[i].len > ctx->match_window_end)
+ matches[i].len = ctx->match_window_end - ctx->match_window_pos;
+ else
+ break;
+ }
+ } else {
+ unsigned prev_len = 1;
+ struct raw_match * matches_ret = &ctx->cached_matches[ctx->cached_matches_pos + 1];
+ num_matches = 0;
+
+ if (ctx->params.slow.use_len2_matches &&
+ ctx->match_window_end - ctx->match_window_pos >= 3) {
+ unsigned c1 = ctx->window[ctx->match_window_pos];
+ unsigned c2 = ctx->window[ctx->match_window_pos + 1];
+ unsigned digram = c1 | (c2 << 8);
+ unsigned cur_match;
+
+ cur_match = ctx->digram_tab[digram];
+ ctx->digram_tab[digram] = ctx->match_window_pos;
+ if (cur_match != 0 &&
+ ctx->window[cur_match + 2] != ctx->window[ctx->match_window_pos + 2])
+ {
+ matches_ret->len = 2;
+ matches_ret->offset = ctx->match_window_pos - cur_match;
+ matches_ret++;
+ num_matches++;
+ prev_len = 2;
+ }
+ }
+ if (ctx->match_window_end - ctx->match_window_pos >= 3) {
+ unsigned hash;
+ unsigned cur_match;
+
+ hash = lzx_lz_compute_hash(&ctx->window[ctx->match_window_pos]);
+
+ cur_match = ctx->hash_tab[hash];
+ ctx->hash_tab[hash] = ctx->match_window_pos;
+ num_matches += lzx_lz_get_matches(ctx->window,
+ ctx->match_window_end - ctx->match_window_pos,
+ ctx->match_window_pos,
+ ctx->params.slow.num_fast_bytes,
+ ctx->child_tab,
+ cur_match,
+ prev_len,
+ matches_ret);
+ }
+
+ ctx->cached_matches[ctx->cached_matches_pos].len = num_matches;
+ ctx->cached_matches[ctx->cached_matches_pos].offset = ctx->match_window_pos;
+
+ if (num_matches) {
+ struct raw_match *longest_match_ptr =
+ &ctx->cached_matches[ctx->cached_matches_pos + 1 +
+ num_matches - 1];
+ u16 len = longest_match_ptr->len;
+
+ /* If the longest match returned by the match-finder
+ * reached the number of fast bytes, extend it as much
+ * as possible. */
+ if (len == ctx->params.slow.num_fast_bytes) {
+ const unsigned maxlen =
+ min(ctx->match_window_end - ctx->match_window_pos,
+ LZX_MAX_MATCH);
+
+ const u8 * const matchptr =
+ &ctx->window[ctx->match_window_pos - longest_match_ptr->offset];
+
+ const u8 * const strptr =
+ &ctx->window[ctx->match_window_pos];
+
+ while (len < maxlen && matchptr[len] == strptr[len])
+ len++;
+ }
+ longest_match_ptr->len = len;
+ }
+ }
+ ctx->cached_matches_pos += num_matches + 1;
+ *matches_ret = matches;
+
+#if 0
+ printf("\n");
+ for (unsigned i = 0; i < num_matches; i++)
+ {
+ printf("Len %u Offset %u\n", matches[i].len, matches[i].offset);
+ }
+#endif
+
+ for (unsigned i = 0; i < num_matches; i++) {
+ LZX_ASSERT(matches[i].len <= LZX_MAX_MATCH);
+ if (matches[i].len >= LZX_MIN_MATCH) {
+ LZX_ASSERT(matches[i].offset <= ctx->match_window_pos);
+ LZX_ASSERT(matches[i].len <= ctx->match_window_end - 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));
+ }
+ }
+
+ 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 "best" 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 best 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. It is not a true
+ * "optimal" parser, however, since some shortcuts can be taken; for example, if
+ * a match is very long, the parser just chooses it immediately before too much
+ * time is wasting considering many different alternatives that are unlikely to
+ * be 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)
+ * ctx->hash_tab (must set to 0 before first call)
+ * ctx->cached_matches (internal state; leave uninitialized)
+ * ctx->cached_matches_pos (initialize to 0 before first call; save and
+ * restore value if restarting parse from a
+ * certain position)
+ * ctx->match_window_pos (must initialize to position of next match to
+ * return; subsequent calls return subsequent
+ * matches)
+ * ctx->match_window_end (must initialize to limit of match-finding region;
+ * subsequent calls use the same limit)
+ *
+ * The return value is a (length, offset) pair specifying the match or literal
+ * chosen. For literals, length is either 0 or 1 and offset is meaningless.
+ */
+static struct raw_match
+lzx_lz_get_near_optimal_match(struct lzx_compressor * ctx)
+{
+#if 0
+ /* Testing: literals only */
+ ctx->match_window_pos++;
+ return (struct raw_match) { .len = 0 };
+#elif 0
+ /* Testing: greedy parsing */
+ struct raw_match *matches;
+ unsigned num_matches;
+ struct raw_match match = {.len = 0};
+
+ num_matches = lzx_lz_get_matches_caching(ctx, &matches);
+ if (num_matches) {
+ match = matches[num_matches - 1];
+ lzx_lz_skip_bytes(ctx, match.len - 1);
+ }
+ return match;
+#else
+ unsigned num_possible_matches;
+ struct raw_match *possible_matches;
+ struct raw_match match;
+ unsigned longest_match_len;
+ unsigned len, match_idx;
+
+ 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;
-static const struct lz_params lzx_lz_params = {
+ /* Get matches at this position. */
+ num_possible_matches = lzx_lz_get_matches_caching(ctx, &possible_matches);
- /* LZX_MIN_MATCH == 2, but 2-character matches are rarely useful; the
- * minimum match for compression is set to 3 instead. */
- .min_match = 3,
+ /* If no matches found, return literal. */
+ if (num_possible_matches == 0)
+ return (struct raw_match){ .len = 0 };
- .max_match = LZX_MAX_MATCH,
- .good_match = LZX_MAX_MATCH,
- .nice_match = LZX_MAX_MATCH,
- .max_chain_len = LZX_MAX_MATCH,
- .max_lazy_match = LZX_MAX_MATCH,
- .too_far = 4096,
+ /* The matches that were found are sorted by length. Get the length of
+ * the longest one. */
+ longest_match_len = possible_matches[num_possible_matches - 1].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.slow.num_fast_bytes) {
+ lzx_lz_skip_bytes(ctx, longest_match_len - 1);
+ return possible_matches[num_possible_matches - 1];
+ }
+
+ /* Calculate the cost to reach the next position by outputting a
+ * literal. */
+#if LZX_PARAM_ACCOUNT_FOR_LRU
+ ctx->optimum[0].queue = ctx->queue;
+ ctx->optimum[1].queue = ctx->optimum[0].queue;
+#endif
+ 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. */
+ match_idx = 0;
+ BUILD_BUG_ON(LZX_MIN_MATCH != 2);
+ for (len = LZX_MIN_MATCH; len <= longest_match_len; len++) {
+
+ LZX_ASSERT(match_idx < num_possible_matches);
+
+ #if LZX_PARAM_ACCOUNT_FOR_LRU
+ ctx->optimum[len].queue = ctx->optimum[0].queue;
+ #endif
+ 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
+ #if LZX_PARAM_ACCOUNT_FOR_LRU
+ , &ctx->optimum[len].queue
+ #endif
+ );
+ 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_PARAM_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,
+ &possible_matches);
+
+ unsigned new_len = 0;
+
+ if (num_possible_matches != 0) {
+ new_len = possible_matches[num_possible_matches - 1].len;
+
+ /* Greedy heuristic: if we found a match greater than
+ * the number of fast bytes, stop immediately. */
+ if (new_len > ctx->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[num_possible_matches - 1].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. */
+ u32 cur_cost = ctx->optimum[cur_pos].cost;
+ u32 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;
+ #if LZX_PARAM_ACCOUNT_FOR_LRU
+ ctx->optimum[cur_pos + 1].queue = ctx->optimum[cur_pos].queue;
+ #endif
+ }
+
+ if (num_possible_matches == 0)
+ continue;
+
+ /* Consider proceeding with a match. */
+
+ while (len_end < cur_pos + new_len)
+ ctx->optimum[++len_end].cost = ~(u32)0;
+
+ match_idx = 0;
+ for (len = LZX_MIN_MATCH; len <= new_len; len++) {
+ LZX_ASSERT(match_idx < num_possible_matches);
+ #if LZX_PARAM_ACCOUNT_FOR_LRU
+ struct lzx_lru_queue q = ctx->optimum[cur_pos].queue;
+ #endif
+ u32 cost = cur_cost + lzx_match_cost(len,
+ possible_matches[match_idx].offset,
+ &ctx->costs
+ #if LZX_PARAM_ACCOUNT_FOR_LRU
+ , &q
+ #endif
+ );
+
+ 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;
+ #if LZX_PARAM_ACCOUNT_FOR_LRU
+ ctx->optimum[cur_pos + len].queue = q;
+ #endif
+ }
+
+ if (len == possible_matches[match_idx].len)
+ match_idx++;
+ }
+ }
+#endif
+}
+
+static unsigned
+lzx_huffman_code_output_cost(const u8 lens[restrict],
+ const freq_t freqs[restrict],
+ unsigned num_syms)
+{
+ unsigned cost = 0;
+
+ for (unsigned i = 0; i < num_syms; i++)
+ cost += (unsigned)lens[i] * (unsigned)freqs[i];
+
+ return cost;
+}
+
+/* Return the number of bits required to output the lengths for the specified
+ * Huffman code in compressed format (encoded with a precode). */
+static unsigned
+lzx_code_cost(const u8 lens[], const u8 prev_lens[], unsigned num_syms)
+{
+ u8 output_syms[num_syms];
+ freq_t precode_freqs[LZX_PRETREE_NUM_SYMBOLS];
+ u8 precode_lens[LZX_PRETREE_NUM_SYMBOLS];
+ u16 precode_codewords[LZX_PRETREE_NUM_SYMBOLS];
+ unsigned cost = 0;
+ unsigned num_additional_bits;
+
+ /* Acount for the lengths of the precode itself. */
+ cost += LZX_PRETREE_NUM_SYMBOLS * LZX_PRETREE_ELEMENT_SIZE;
+
+ lzx_build_precode(lens, prev_lens, num_syms,
+ precode_freqs, output_syms,
+ precode_lens, precode_codewords,
+ &num_additional_bits);
+
+ /* Account for all precode symbols output. */
+ cost += lzx_huffman_code_output_cost(precode_lens, precode_freqs,
+ LZX_PRETREE_NUM_SYMBOLS);
+
+ /* Account for additional bits. */
+ cost += num_additional_bits;
+
+ return cost;
+}
+
+/* Account for extra bits in the main symbols. */
+static void
+lzx_update_mainsym_match_costs(int block_type,
+ u8 main_lens[LZX_MAINTREE_NUM_SYMBOLS])
+{
+ unsigned i;
+
+ LZX_ASSERT(block_type == LZX_BLOCKTYPE_ALIGNED ||
+ block_type == LZX_BLOCKTYPE_VERBATIM);
+
+ for (i = LZX_NUM_CHARS; i < LZX_MAINTREE_NUM_SYMBOLS; i++) {
+ unsigned position_slot = (i >> 3) & 0x1f;
+
+ /* If it's a verbatim block, add the number of extra bits
+ * corresponding to the position slot.
+ *
+ * If it's an aligned block and there would normally be at least
+ * 3 extra bits, count 3 less because they will be output as an
+ * aligned offset symbol instead. */
+ unsigned num_extra_bits = lzx_get_num_extra_bits(position_slot);
+
+ if (block_type == LZX_BLOCKTYPE_ALIGNED && num_extra_bits >= 3)
+ num_extra_bits -= 3;
+ main_lens[i] += num_extra_bits;
+ }
+}
+
+/*
+ * Compute the costs, in bits, to output a compressed block as aligned offset
+ * and verbatim.
+ *
+ * @block_size
+ * Number of bytes of uncompressed data the block represents.
+ * @codes
+ * Huffman codes that will be used when outputting the block.
+ * @prev_codes
+ * Huffman codes for the previous block, or all zeroes if this is the first
+ * block.
+ * @freqs
+ * Frequencies of Huffman symbols that will be output in the block.
+ * @aligned_cost_ret
+ * Cost of aligned block will be returned here.
+ * @verbatim_cost_ret
+ * Cost of verbatim block will be returned here.
+ */
+static void
+lzx_compute_compressed_block_costs(unsigned block_size,
+ const struct lzx_codes *codes,
+ const struct lzx_codes *prev_codes,
+ const struct lzx_freqs *freqs,
+ unsigned * aligned_cost_ret,
+ unsigned * verbatim_cost_ret)
+{
+ unsigned common_cost = 0;
+ unsigned aligned_cost = 0;
+ unsigned verbatim_cost = 0;
+
+ u8 updated_main_lens[LZX_MAINTREE_NUM_SYMBOLS];
+
+ /* Account for cost of block header. */
+ common_cost += LZX_BLOCKTYPE_NBITS;
+ if (block_size == LZX_DEFAULT_BLOCK_SIZE)
+ common_cost += 1;
+ else
+ common_cost += LZX_BLOCKSIZE_NBITS;
+
+ /* Account for cost of outputting aligned offset code. */
+ aligned_cost += LZX_ALIGNEDTREE_NUM_SYMBOLS * LZX_ALIGNEDTREE_ELEMENT_SIZE;
+
+ /* Account for cost of outputting main and length codes. */
+ common_cost += lzx_code_cost(codes->lens.main,
+ prev_codes->lens.main,
+ LZX_NUM_CHARS);
+ common_cost += lzx_code_cost(codes->lens.main + LZX_NUM_CHARS,
+ prev_codes->lens.main + LZX_NUM_CHARS,
+ LZX_MAINTREE_NUM_SYMBOLS - LZX_NUM_CHARS);
+ common_cost += lzx_code_cost(codes->lens.len,
+ prev_codes->lens.len,
+ LZX_LENTREE_NUM_SYMBOLS);
+
+ /* Account for cost to output main, length, and aligned symbols, taking
+ * into account extra position bits. */
+
+ memcpy(updated_main_lens, codes->lens.main, LZX_MAINTREE_NUM_SYMBOLS);
+ lzx_update_mainsym_match_costs(LZX_BLOCKTYPE_VERBATIM, updated_main_lens);
+ verbatim_cost += lzx_huffman_code_output_cost(updated_main_lens,
+ freqs->main,
+ LZX_MAINTREE_NUM_SYMBOLS);
+ memcpy(updated_main_lens, codes->lens.main, LZX_MAINTREE_NUM_SYMBOLS);
+ lzx_update_mainsym_match_costs(LZX_BLOCKTYPE_ALIGNED, updated_main_lens);
+ aligned_cost += lzx_huffman_code_output_cost(updated_main_lens,
+ freqs->main,
+ LZX_MAINTREE_NUM_SYMBOLS);
+
+ common_cost += lzx_huffman_code_output_cost(codes->lens.len,
+ freqs->len,
+ LZX_LENTREE_NUM_SYMBOLS);
+
+ aligned_cost += lzx_huffman_code_output_cost(codes->lens.aligned,
+ freqs->aligned,
+ LZX_ALIGNEDTREE_NUM_SYMBOLS);
+
+ *aligned_cost_ret = aligned_cost + common_cost;
+ *verbatim_cost_ret = verbatim_cost + common_cost;
+}
+
+/* Prepare a (nonsplit) compressed block. */
+static unsigned
+lzx_prepare_compressed_block(struct lzx_compressor *ctx, unsigned block_number,
+ struct lzx_codes *prev_codes)
+{
+ struct lzx_block_spec *spec = &ctx->block_specs[block_number - 1];
+ unsigned orig_cached_matches_pos = ctx->cached_matches_pos;
+ struct lzx_lru_queue orig_queue = ctx->queue;
+ struct lzx_freqs freqs;
+ unsigned cost;
+
+ /* Here's where the real work happens. The following loop runs one or
+ * more times, each time using a cost model based on the Huffman codes
+ * computed from the previous iteration (the first iteration uses a
+ * default model). Each iteration of the loop uses a heuristic
+ * algorithm to divide the block into near-optimal matches/literals from
+ * beginning to end. */
+ LZX_ASSERT(ctx->params.slow.num_optim_passes >= 1);
+ spec->num_chosen_matches = 0;
+ for (unsigned pass = 0; pass < ctx->params.slow.num_optim_passes; pass++)
+ {
+ LZX_DEBUG("Block %u: Match-choosing pass %u of %u",
+ block_number, pass + 1,
+ ctx->params.slow.num_optim_passes);
+
+ /* Reset frequency tables. */
+ memset(&freqs, 0, sizeof(freqs));
+
+ /* Reset match offset LRU queue. */
+ ctx->queue = orig_queue;
+
+ /* Reset match-finding position. */
+ ctx->cached_matches_pos = orig_cached_matches_pos;
+ ctx->match_window_pos = spec->window_pos;
+ ctx->match_window_end = spec->window_pos + spec->block_size;
+
+ /* Set cost model. */
+ lzx_set_costs(ctx, &spec->codes.lens);
+
+ unsigned window_pos = spec->window_pos;
+ unsigned end = window_pos + spec->block_size;
+
+ while (window_pos < end) {
+ struct raw_match match;
+ struct lzx_match lzx_match;
+
+ match = lzx_lz_get_near_optimal_match(ctx);
+
+ if (match.len >= LZX_MIN_MATCH) {
+
+ /* Best to output a match here. */
+
+ LZX_ASSERT(match.len <= LZX_MAX_MATCH);
+ LZX_ASSERT(!memcmp(&ctx->window[window_pos],
+ &ctx->window[window_pos - match.offset],
+ match.len));
+
+ /* Tally symbol frequencies. */
+ lzx_match.data = lzx_record_match(match.offset,
+ match.len,
+ &freqs,
+ &ctx->queue);
+
+ window_pos += match.len;
+ } else {
+ /* Best to output a literal here. */
+
+ /* Tally symbol frequencies. */
+ lzx_match.data = lzx_record_literal(ctx->window[window_pos],
+ &freqs);
+
+ window_pos += 1;
+ }
+
+ /* If it's the last pass, save the match/literal in
+ * intermediate form. */
+ if (pass == ctx->params.slow.num_optim_passes - 1) {
+ ctx->chosen_matches[spec->chosen_matches_start_pos +
+ spec->num_chosen_matches] = lzx_match;
+
+ spec->num_chosen_matches++;
+ }
+ }
+ LZX_ASSERT(window_pos == end);
+
+ /* Build Huffman codes using the new frequencies. */
+ lzx_make_huffman_codes(&freqs, &spec->codes);
+
+ /* The first time we get here is when the full input has been
+ * processed, so the match-finding is done. */
+ ctx->matches_already_found = true;
+ }
+
+ LZX_DEBUG("Block %u: saved %u matches/literals @ %u",
+ block_number, spec->num_chosen_matches,
+ spec->chosen_matches_start_pos);
+
+ unsigned aligned_cost;
+ unsigned verbatim_cost;
+
+ lzx_compute_compressed_block_costs(spec->block_size,
+ &spec->codes,
+ prev_codes,
+ &freqs,
+ &aligned_cost,
+ &verbatim_cost);
+
+ /* Choose whether to make the block aligned offset or verbatim. */
+ if (aligned_cost < verbatim_cost) {
+ spec->block_type = LZX_BLOCKTYPE_ALIGNED;
+ cost = aligned_cost;
+ LZX_DEBUG("Using aligned block (cost %u vs %u for verbatim)",
+ aligned_cost, verbatim_cost);
+ } else {
+ spec->block_type = LZX_BLOCKTYPE_VERBATIM;
+ cost = verbatim_cost;
+ LZX_DEBUG("Using verbatim block (cost %u vs %u for aligned)",
+ verbatim_cost, aligned_cost);
+ }
+
+ LZX_DEBUG("Block %u is %u => %u bytes unsplit.",
+ block_number, spec->block_size, cost / 8);
+
+ return cost;
+}
+
+/*
+ * lzx_prepare_block_recursive() -
+ *
+ * Given a (possibly nonproper) sub-sequence of the preprocessed input, compute
+ * the LZX block(s) that it should be output as.
+ *
+ * This function initially considers the case where the given sub-sequence of
+ * the preprocessed input be output as a single block. This block is calculated
+ * and its cost (number of bits required to output it) is computed.
+ *
+ * Then, if @max_split_level is greater than zero, a split into two evenly sized
+ * subblocks is considered. The block is recursively split in this way,
+ * potentially up to the depth specified by @max_split_level. The cost of the
+ * split block is compared to the cost of the single block, and the lower cost
+ * solution is used.
+ *
+ * For each compressed output block computed, the sequence of matches/literals
+ * and the corresponding Huffman codes for the block are produced and saved.
+ *
+ * The return value is the approximate number of bits the block (or all
+ * subblocks, in the case that the split block had lower cost), will take up
+ * when written to the compressed output.
+ */
+static unsigned
+lzx_prepare_block_recursive(struct lzx_compressor * ctx,
+ unsigned block_number,
+ unsigned max_split_level,
+ struct lzx_codes **prev_codes_p)
+{
+ struct lzx_block_spec *spec = &ctx->block_specs[block_number - 1];
+ unsigned cost;
+ unsigned orig_cached_matches_pos;
+ struct lzx_lru_queue orig_queue, nonsplit_queue;
+ struct lzx_codes *prev_codes = *prev_codes_p;
+
+ LZX_DEBUG("Preparing block %u...", block_number);
+
+ /* Save positions of chosen and cached matches, and the match offset LRU
+ * queue, so that they can be restored if splitting is attempted. */
+ orig_cached_matches_pos = ctx->cached_matches_pos;
+ orig_queue = ctx->queue;
+
+ /* Consider outputting the input subsequence as a single block. */
+ spec->is_split = 0;
+ cost = lzx_prepare_compressed_block(ctx, block_number, prev_codes);
+ nonsplit_queue = ctx->queue;
+
+ *prev_codes_p = &spec->codes;
+
+ /* If the maximum split level is at least one, consider splitting the
+ * block in two. */
+ if (max_split_level--) {
+
+ LZX_DEBUG("Calculating split of block %u...", block_number);
+
+ struct lzx_block_spec *spec1, *spec2;
+ unsigned split_cost;
+
+ ctx->cached_matches_pos = orig_cached_matches_pos;
+ ctx->queue = orig_queue;
+
+ /* Prepare and get the cost of the first sub-block. */
+ spec1 = &ctx->block_specs[block_number * 2 - 1];
+ spec1->codes.lens = spec->codes.lens;
+ spec1->window_pos = spec->window_pos;
+ spec1->block_size = spec->block_size / 2;
+ spec1->chosen_matches_start_pos = spec->chosen_matches_start_pos +
+ LZX_MAX_WINDOW_SIZE;
+ split_cost = lzx_prepare_block_recursive(ctx,
+ block_number * 2,
+ max_split_level,
+ &prev_codes);
+
+ /* Prepare and get the cost of the second sub-block. */
+ spec2 = spec1 + 1;
+ spec2->codes.lens = spec->codes.lens;
+ spec2->window_pos = spec->window_pos + spec1->block_size;
+ spec2->block_size = spec->block_size - spec1->block_size;
+ spec2->chosen_matches_start_pos = spec1->chosen_matches_start_pos +
+ spec1->block_size;
+ split_cost += lzx_prepare_block_recursive(ctx,
+ block_number * 2 + 1,
+ max_split_level,
+ &prev_codes);
+
+ /* Compare the cost of the whole block with that of the split
+ * block. Choose the lower cost solution. */
+ if (split_cost < cost) {
+ LZX_DEBUG("Splitting block %u is worth it "
+ "(%u => %u bytes).",
+ block_number, cost / 8, split_cost / 8);
+ spec->is_split = 1;
+ cost = split_cost;
+ *prev_codes_p = prev_codes;
+ } else {
+ LZX_DEBUG("Splitting block %u is NOT worth it "
+ "(%u => %u bytes).",
+ block_number, cost / 8, split_cost / 8);
+ ctx->queue = nonsplit_queue;
+ }
+ }
+
+ return cost;
+}
+
+/* Empirical averages */
+static const u8 lzx_default_mainsym_costs[LZX_MAINTREE_NUM_SYMBOLS] = {
+ 7, 9, 9, 10, 9, 10, 10, 10, 9, 10, 9, 10, 10, 9, 10, 10, 9, 10, 10, 11,
+ 10, 10, 10, 11, 10, 11, 11, 11, 10, 11, 11, 11, 8, 11, 9, 10, 9, 10, 11,
+ 11, 9, 9, 11, 10, 10, 9, 9, 9, 8, 8, 8, 8, 8, 9, 9, 9, 8, 8, 9, 9, 9, 9,
+ 10, 10, 10, 8, 9, 8, 8, 8, 8, 9, 9, 9, 10, 10, 8, 8, 9, 9, 8, 10, 9, 8,
+ 8, 9, 8, 9, 9, 10, 10, 10, 9, 10, 11, 9, 10, 8, 9, 8, 8, 8, 8, 9, 8, 8,
+ 9, 9, 8, 8, 8, 8, 8, 10, 8, 8, 7, 8, 9, 9, 9, 9, 10, 11, 10, 10, 11, 11,
+ 10, 11, 11, 10, 10, 11, 11, 11, 10, 10, 11, 10, 11, 10, 11, 11, 10, 11,
+ 11, 12, 11, 11, 11, 12, 11, 11, 11, 11, 11, 11, 11, 12, 10, 11, 11, 11,
+ 11, 11, 11, 12, 11, 11, 11, 11, 11, 12, 11, 11, 10, 11, 11, 11, 11, 11,
+ 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11,
+ 10, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 12, 11, 11, 10, 11,
+ 11, 11, 11, 12, 11, 11, 10, 11, 11, 11, 10, 12, 11, 11, 10, 10, 11, 10,
+ 10, 11, 11, 11, 10, 11, 11, 11, 10, 11, 11, 11, 10, 11, 11, 11, 10, 11,
+ 10, 9, 8, 7, 10, 10, 11, 10, 11, 7, 9, 9, 11, 11, 11, 12, 11, 9, 10, 10,
+ 12, 12, 13, 13, 12, 11, 10, 12, 12, 14, 14, 14, 13, 12, 9, 12, 13, 14,
+ 14, 14, 14, 14, 9, 10, 13, 14, 14, 14, 14, 14, 9, 9, 11, 11, 13, 13, 13,
+ 14, 9, 9, 11, 12, 12, 13, 13, 13, 8, 8, 11, 11, 12, 12, 12, 11, 9, 9,
+ 10, 11, 12, 12, 12, 11, 8, 9, 10, 10, 11, 12, 11, 10, 9, 9, 10, 11, 11,
+ 12, 11, 10, 8, 9, 10, 10, 11, 11, 11, 9, 9, 9, 10, 11, 11, 11, 11, 9, 8,
+ 8, 10, 10, 11, 11, 11, 9, 9, 9, 10, 10, 11, 11, 11, 9, 9, 8, 9, 10, 11,
+ 11, 11, 9, 10, 9, 10, 11, 11, 11, 11, 9, 14, 9, 9, 10, 10, 11, 10, 9,
+ 14, 9, 10, 11, 11, 11, 11, 9, 14, 9, 10, 10, 11, 11, 11, 9, 14, 10, 10,
+ 11, 11, 12, 11, 10, 14, 10, 10, 10, 11, 11, 11, 10, 14, 11, 11, 11, 11,
+ 12, 12, 10, 14, 10, 11, 11, 11, 12, 11, 10, 14, 11, 11, 11, 12, 12, 12,
+ 11, 15, 11, 11, 11, 12, 12, 12, 11, 14, 12, 12, 12, 12, 13, 12, 11, 15,
+ 12, 12, 12, 13, 13, 13, 12, 15, 14, 13, 14, 14, 14, 14, 13,
+};
+
+/* Empirical averages */
+static const u8 lzx_default_lensym_costs[LZX_LENTREE_NUM_SYMBOLS] = {
+ 5, 5, 5, 5, 5, 6, 5, 5, 6, 7, 7, 7, 8, 8, 7, 8, 9, 9, 9, 9, 10, 9, 9,
+ 10, 9, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 12, 12, 12, 11, 12, 12,
+ 12, 12, 12, 12, 13, 12, 12, 12, 13, 12, 13, 13, 12, 12, 13, 12, 13, 13,
+ 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 14, 13, 14, 13, 14, 13,
+ 14, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
+ 14, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
+ 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
+ 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
+ 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
+ 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
+ 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
+ 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
+ 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
+ 14, 14, 14, 14, 14, 14, 14, 14, 14, 10,
};
/*
- * Performs LZX compression on a block of data.
- *
- * @__uncompressed_data: Pointer to the data to be compressed.
- * @uncompressed_len: Length, in bytes, of the data to be compressed.
- * @compressed_data: Pointer to a location at least (@uncompressed_len - 1)
- * bytes long into which the compressed data may be
- * written.
- * @compressed_len_ret: A pointer to an unsigned int into which the length of
- * the compressed data may be returned.
- *
- * Returns zero if compression was successfully performed. In that case
- * @compressed_data and @compressed_len_ret will contain the compressed data and
- * its length. A return value of nonzero means that compressing the data did
- * not reduce its size, and @compressed_data will not contain the full
- * compressed data.
+ * Set default symbol costs.
*/
-int lzx_compress(const void *__uncompressed_data, unsigned uncompressed_len,
- void *compressed_data, unsigned *compressed_len_ret)
+static void
+lzx_set_default_costs(struct lzx_lens * lens)
{
- 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;
- if (uncompressed_len < 100)
- return 1;
+#if LZX_PARAM_USE_EMPIRICAL_DEFAULT_COSTS
+ memcpy(&lens->main, lzx_default_mainsym_costs, LZX_MAINTREE_NUM_SYMBOLS);
+ memcpy(&lens->len, lzx_default_lensym_costs, LZX_LENTREE_NUM_SYMBOLS);
- memset(&freq_tabs, 0, sizeof(freq_tabs));
- queue.R0 = 1;
- queue.R1 = 1;
- queue.R2 = 1;
+#else
+ /* Literal symbols */
+ for (i = 0; i < LZX_NUM_CHARS; i++)
+ lens->main[i] = 8;
- /* 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);
+ /* Match header symbols */
+ for (; i < LZX_MAINTREE_NUM_SYMBOLS; i++)
+ lens->main[i] = 10;
- /* Before doing any actual compression, do the call instruction (0xe8
- * byte) translation on the uncompressed data. */
- do_call_insn_preprocessing(uncompressed_data, uncompressed_len);
+ /* Length symbols */
+ for (i = 0; i < LZX_LENTREE_NUM_SYMBOLS; i++)
+ lens->len[i] = 8;
+#endif
+
+ /* Aligned offset symbols */
+ for (i = 0; i < LZX_ALIGNEDTREE_NUM_SYMBOLS; i++)
+ lens->aligned[i] = 3;
+}
- /* 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. */
+/*
+ * lzx_prepare_blocks() -
+ *
+ * Calculate the blocks to split the preprocessed data into.
+ *
+ * Input --- the preprocessed data:
+ *
+ * ctx->window[]
+ * ctx->window_size
+ *
+ * Working space:
+ * Match finding:
+ * ctx->hash_tab
+ * ctx->child_tab
+ * ctx->cached_matches
+ * ctx->cached_matches_pos
+ * ctx->matches_already_found
+ *
+ * Block cost modeling:
+ * ctx->costs
+ * ctx->block_specs (also an output)
+ *
+ * Match choosing:
+ * ctx->optimum
+ * ctx->optimum_cur_idx
+ * ctx->optimum_end_idx
+ * ctx->chosen_matches (also an output)
+ *
+ * Output --- the block specifications and the corresponding match/literal data:
+ *
+ * ctx->block_specs[]
+ * ctx->chosen_matches[]
+ *
+ * The return value is the approximate number of bits the compressed data will
+ * take up.
+ */
+static unsigned
+lzx_prepare_blocks(struct lzx_compressor * ctx)
+{
+ /* This function merely does some initializations, then passes control
+ * to lzx_prepare_block_recursive(). */
+
+ /* 1. Initialize match-finding variables. */
+
+ /* Zero all entries in the hash table, indicating that no length-3
+ * character sequences have been discovered in the input yet. */
+ memset(ctx->hash_tab, 0, LZX_LZ_HASH_SIZE * 2 * sizeof(ctx->hash_tab[0]));
+ if (ctx->params.slow.use_len2_matches)
+ memset(ctx->digram_tab, 0, 256 * 256 * sizeof(ctx->digram_tab[0]));
+ /* Note: ctx->child_tab need not be initialized. */
+
+ /* No matches have been found and cached yet. */
+ ctx->cached_matches_pos = 0;
+ ctx->matches_already_found = false;
+
+ /* 2. Initialize match-choosing variables. */
+ ctx->optimum_cur_idx = 0;
+ ctx->optimum_end_idx = 0;
+ /* Note: ctx->optimum need not be initialized. */
+ ctx->block_specs[0].chosen_matches_start_pos = 0;
+
+ /* 3. Set block 1 (index 0) to represent the entire input data. */
+ ctx->block_specs[0].block_size = ctx->window_size;
+ ctx->block_specs[0].window_pos = 0;
+
+ /* 4. Set up a default Huffman symbol cost model for block 1 (index 0).
+ * The model will be refined later. */
+ lzx_set_default_costs(&ctx->block_specs[0].codes.lens);
+
+ /* 5. Initialize the match offset LRU queue. */
+ ctx->queue = (struct lzx_lru_queue){1, 1, 1};
+
+ /* 6. Pass control to recursive procedure. */
+ struct lzx_codes * prev_codes = &ctx->zero_codes;
+ return lzx_prepare_block_recursive(ctx, 1,
+ ctx->params.slow.num_split_passes,
+ &prev_codes);
+}
- num_matches = lz_analyze_block(uncompressed_data, uncompressed_len,
- match_tab, lzx_record_match,
- lzx_record_literal, &freq_tabs,
- &queue, freq_tabs.main_freq_table,
+/*
+ * 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
+ *
+ * Working space:
+ * ctx->queue
+ *
+ * Output --- the block specifications and the corresponding match/literal data:
+ *
+ * ctx->block_specs[]
+ * ctx->chosen_matches[]
+ */
+static void
+lzx_prepare_block_fast(struct lzx_compressor * ctx)
+{
+ unsigned num_matches;
+ struct lzx_freqs freqs;
+ struct lzx_block_spec *spec;
+
+ /* Parameters to hash chain LZ match finder */
+ 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,
+ .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,
+ };
+
+ /* Initialize symbol frequencies and match offset LRU queue. */
+ memset(&freqs, 0, sizeof(struct lzx_freqs));
+ ctx->queue = (struct lzx_lru_queue){ 1, 1, 1 };
+
+ /* Determine series of matches/literals to output. */
+ num_matches = lz_analyze_block(ctx->window,
+ ctx->window_size,
+ (u32*)ctx->chosen_matches,
+ lzx_record_match,
+ lzx_record_literal,
+ &freqs,
+ &ctx->queue,
+ &freqs,
&lzx_lz_params);
- lzx_make_huffman_codes(&freq_tabs, &codes);
- /* Initialize the output bitstream. */
- init_output_bitstream(&ostream, compressed_data, uncompressed_len - 1);
+ /* Set up block specification. */
+ spec = &ctx->block_specs[0];
+ spec->is_split = 0;
+ spec->block_type = LZX_BLOCKTYPE_ALIGNED;
+ spec->window_pos = 0;
+ spec->block_size = ctx->window_size;
+ spec->num_chosen_matches = num_matches;
+ spec->chosen_matches_start_pos = 0;
+ lzx_make_huffman_codes(&freqs, &spec->codes);
+}
- /* 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);
+static void
+do_call_insn_translation(u32 *call_insn_target, int input_pos,
+ s32 file_size)
+{
+ s32 abs_offset;
+ s32 rel_offset;
- /* 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);
+ 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);
}
+}
- /* Write out the aligned offset tree. Note that M$ lies and says that
- * the aligned offset tree comes after the length tree, but that is
- * wrong; it actually is before the main tree. */
- if (block_type == LZX_BLOCKTYPE_ALIGNED)
- for (i = 0; i < LZX_ALIGNEDTREE_NUM_SYMBOLS; i++)
- bitstream_put_bits(&ostream, codes.aligned_lens[i],
- LZX_ALIGNEDTREE_ELEMENT_SIZE);
+/* 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;
+ }
+ }
+}
- /* Write the pre-tree and lengths for the first LZX_NUM_CHARS symbols in the
- * main tree. */
- ret = lzx_write_compressed_tree(&ostream, codes.main_lens,
- LZX_NUM_CHARS);
- if (ret != 0)
- return ret;
-
- /* Write the pre-tree and symbols for the rest of the main tree. */
- ret = lzx_write_compressed_tree(&ostream, codes.main_lens +
- LZX_NUM_CHARS,
- LZX_MAINTREE_NUM_SYMBOLS -
- LZX_NUM_CHARS);
- if (ret != 0)
- return ret;
-
- /* Write the pre-tree and symbols for the length tree. */
- ret = lzx_write_compressed_tree(&ostream, codes.len_lens,
- LZX_LENTREE_NUM_SYMBOLS);
- if (ret != 0)
- return ret;
-
- /* Write the compressed literals. */
- ret = lzx_write_compressed_literals(&ostream, block_type,
- match_tab, num_matches, &codes);
- if (ret != 0)
- return ret;
-
- ret = flush_output_bitstream(&ostream);
- if (ret != 0)
- return ret;
+/* 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;
+ unsigned compressed_len;
- compressed_len = ostream.bit_output - (u8*)compressed_data;
+ if (uncompressed_len < 100) {
+ LZX_DEBUG("Too small to bother compressing.");
+ return 0;
+ }
+
+ if (uncompressed_len > 32768) {
+ LZX_DEBUG("Only up to 32768 bytes of uncompressed data are supported.");
+ return 0;
+ }
+
+ wimlib_assert(lzx_ctx != NULL);
+
+ 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...");
- *compressed_len_ret = compressed_len;
+ /* 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...");
-#ifdef ENABLE_VERIFY_COMPRESSION
- /* Verify that we really get the same thing back when decompressing. */
- u8 buf[uncompressed_len];
- ret = lzx_decompress(compressed_data, compressed_len, buf,
- uncompressed_len);
- if (ret != 0) {
- ERROR("lzx_compress(): Failed to decompress data we compressed");
- abort();
+ /* Generate the compressed data. */
+ init_output_bitstream(&ostream, compressed_data, ctx->window_size - 1);
+ lzx_write_all_blocks(ctx, &ostream);
+
+ LZX_DEBUG("Flushing bitstream...");
+ if (flush_output_bitstream(&ostream)) {
+ /* If the bitstream cannot be flushed, then the output space was
+ * exhausted. */
+ LZX_DEBUG("Data did not compress to less than original length!");
+ return 0;
}
- 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();
+ /* Compute the length of the compressed data. */
+ compressed_len = ostream.bit_output - (u8*)compressed_data;
+
+ LZX_DEBUG("Done: compressed %u => %u bytes.",
+ uncompressed_len, compressed_len);
+
+#if defined(ENABLE_LZX_DEBUG) || defined(ENABLE_VERIFY_COMPRESSION)
+ /* Verify that we really get the same thing back when decompressing. */
+ {
+ u8 buf[uncompressed_len];
+ int ret;
+ unsigned i;
+
+ ret = wimlib_lzx_decompress(compressed_data, compressed_len,
+ buf, uncompressed_len);
+ if (ret) {
+ ERROR("Failed to decompress data we "
+ "compressed using LZX algorithm");
+ wimlib_assert(0);
+ return 0;
+ }
+
+ bool bad = false;
+ const u8 * udata = uncompressed_data;
+ for (i = 0; i < uncompressed_len; i++) {
+ if (buf[i] != udata[i]) {
+ bad = true;
+ ERROR("Data we compressed using LZX algorithm "
+ "didn't decompress to original "
+ "(difference at idx %u: c %#02x, u %#02x)",
+ i, buf[i], udata[i]);
+ }
+ }
+ if (bad) {
+ wimlib_assert(0);
+ return 0;
}
}
#endif
+ 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));
+}
+
+/* API function documented in wimlib.h */
+WIMLIBAPI int
+wimlib_lzx_alloc_context(const struct wimlib_lzx_params *params,
+ struct wimlib_lzx_context **ctx_pp)
+{
+
+ LZX_DEBUG("Allocating LZX context...");
+
+ 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,
+ .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,
+ .slow = {
+ .use_len2_matches = 1,
+ .num_fast_bytes = 32,
+ .num_optim_passes = 3,
+ .num_split_passes = 3,
+ .main_nostat_cost = 15,
+ .len_nostat_cost = 15,
+ .aligned_nostat_cost = 7,
+ },
+ };
+
+ if (params == NULL) {
+ LZX_DEBUG("Using default algorithm and parameters.");
+ params = &slow_default;
+ }
+
+ if (params->algorithm != WIMLIB_LZX_ALGORITHM_SLOW &&
+ params->algorithm != WIMLIB_LZX_ALGORITHM_FAST)
+ {
+ LZX_DEBUG("Invalid algorithm.");
+ return WIMLIB_ERR_INVALID_PARAM;
+ }
+
+ if (params->use_defaults) {
+ if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW)
+ params = &slow_default;
+ else
+ params = &fast_default;
+ }
+
+ if (params->size_of_this != sizeof(struct wimlib_lzx_params)) {
+ LZX_DEBUG("Invalid parameter structure size!");
+ return WIMLIB_ERR_INVALID_PARAM;
+ }
+
+ if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) {
+ if (params->slow.num_fast_bytes < 3 ||
+ params->slow.num_fast_bytes > 257)
+ {
+ LZX_DEBUG("Invalid number of fast bytes!");
+ return WIMLIB_ERR_INVALID_PARAM;
+ }
+
+ if (params->slow.num_optim_passes < 1)
+ {
+ LZX_DEBUG("Invalid number of optimization passes!");
+ return WIMLIB_ERR_INVALID_PARAM;
+ }
+
+ if (params->slow.main_nostat_cost < 1 ||
+ params->slow.main_nostat_cost > 16)
+ {
+ LZX_DEBUG("Invalid main_nostat_cost!");
+ return WIMLIB_ERR_INVALID_PARAM;
+ }
+
+ if (params->slow.len_nostat_cost < 1 ||
+ params->slow.len_nostat_cost > 16)
+ {
+ LZX_DEBUG("Invalid len_nostat_cost!");
+ return WIMLIB_ERR_INVALID_PARAM;
+ }
+
+ if (params->slow.aligned_nostat_cost < 1 ||
+ params->slow.aligned_nostat_cost > 8)
+ {
+ LZX_DEBUG("Invalid aligned_nostat_cost!");
+ return WIMLIB_ERR_INVALID_PARAM;
+ }
+ }
+
+ if (ctx_pp == NULL) {
+ LZX_DEBUG("Check parameters only.");
+ return 0;
+ }
+
+ ctx = *(struct lzx_compressor**)ctx_pp;
+
+ if (ctx && lzx_params_compatible(&ctx->params, params))
+ return 0;
+
+ LZX_DEBUG("Allocating memory.");
+
+ ctx = MALLOC(sizeof(struct lzx_compressor));
+ if (ctx == NULL)
+ goto err;
+
+ size_t block_specs_length;
+
+ if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW)
+ block_specs_length = ((1 << (params->slow.num_split_passes + 1)) - 1);
+ else
+ block_specs_length = 1;
+ ctx->block_specs = MALLOC(block_specs_length * sizeof(ctx->block_specs[0]));
+ if (ctx->block_specs == NULL)
+ goto err_free_ctx;
+
+ if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) {
+ ctx->hash_tab = MALLOC((LZX_LZ_HASH_SIZE + 2 * LZX_MAX_WINDOW_SIZE) *
+ sizeof(ctx->hash_tab[0]));
+ if (ctx->hash_tab == NULL)
+ goto err_free_block_specs;
+ ctx->child_tab = ctx->hash_tab + LZX_LZ_HASH_SIZE;
+ } else {
+ ctx->hash_tab = NULL;
+ ctx->child_tab = NULL;
+ }
+
+ if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW &&
+ params->slow.use_len2_matches)
+ {
+ ctx->digram_tab = MALLOC(256 * 256 * sizeof(ctx->digram_tab[0]));
+ if (ctx->digram_tab == NULL)
+ goto err_free_hash_tab;
+ } else {
+ ctx->digram_tab = NULL;
+ }
+
+ if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) {
+ ctx->cached_matches = MALLOC(10 * LZX_MAX_WINDOW_SIZE *
+ sizeof(ctx->cached_matches[0]));
+ if (ctx->cached_matches == NULL)
+ goto err_free_digram_tab;
+ } else {
+ ctx->cached_matches = NULL;
+ }
+
+ if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) {
+ ctx->optimum = MALLOC((LZX_PARAM_OPTIM_ARRAY_SIZE + LZX_MAX_MATCH) *
+ sizeof(ctx->optimum[0]));
+ if (ctx->optimum == NULL)
+ goto err_free_cached_matches;
+ } else {
+ ctx->optimum = NULL;
+ }
+
+ size_t chosen_matches_length;
+ if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW)
+ chosen_matches_length = LZX_MAX_WINDOW_SIZE *
+ (params->slow.num_split_passes + 1);
+ else
+ chosen_matches_length = LZX_MAX_WINDOW_SIZE;
+
+ ctx->chosen_matches = MALLOC(chosen_matches_length *
+ sizeof(ctx->chosen_matches[0]));
+ if (ctx->chosen_matches == NULL)
+ goto err_free_optimum;
+
+ 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_free_optimum:
+ FREE(ctx->optimum);
+err_free_cached_matches:
+ FREE(ctx->cached_matches);
+err_free_digram_tab:
+ FREE(ctx->digram_tab);
+err_free_hash_tab:
+ FREE(ctx->hash_tab);
+err_free_block_specs:
+ FREE(ctx->block_specs);
+err_free_ctx:
+ FREE(ctx);
+err:
+ 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->optimum);
+ FREE(ctx->cached_matches);
+ FREE(ctx->digram_tab);
+ FREE(ctx->hash_tab);
+ FREE(ctx->block_specs);
+ 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;
+ unsigned compressed_len;
+
+ ret = wimlib_lzx_alloc_context(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