+++ /dev/null
-/*
- * lzx-compress.c
- *
- * A compressor that produces output compatible with the LZX compression format.
- */
-
-/*
- * Copyright (C) 2012, 2013, 2014 Eric Biggers
- *
- * This file is free software; you can redistribute it and/or modify it under
- * the terms of the GNU Lesser General Public License as published by the Free
- * Software Foundation; either version 3 of the License, or (at your option) any
- * later version.
- *
- * This file is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
- * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
- * details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this file; if not, see http://www.gnu.org/licenses/.
- */
-
-
-/*
- * This file contains a compressor for the LZX ("Lempel-Ziv eXtended")
- * compression format, as used in the WIM (Windows IMaging) file format.
- *
- * Two different parsing algorithms are implemented: "near-optimal" and "lazy".
- * "Near-optimal" is significantly slower than "lazy", but results in a better
- * compression ratio. The "near-optimal" algorithm is used at the default
- * compression level.
- *
- * This file may need some slight modifications to be used outside of the WIM
- * format. In particular, in other situations the LZX block header might be
- * slightly different, and a sliding window rather than a fixed-size window
- * might be required.
- *
- * Note: LZX is a compression format derived from DEFLATE, the format used by
- * zlib and gzip. Both LZX and DEFLATE use LZ77 matching and Huffman coding.
- * Certain details are quite similar, such as the method for storing Huffman
- * codes. However, the main differences are:
- *
- * - LZX preprocesses the data to attempt to make x86 machine code slightly more
- * compressible before attempting to compress it further.
- *
- * - LZX uses a "main" alphabet which combines literals and matches, with the
- * match symbols containing a "length header" (giving all or part of the match
- * length) and an "offset slot" (giving, roughly speaking, the order of
- * magnitude of the match offset).
- *
- * - LZX does not have static Huffman blocks (that is, the kind with preset
- * Huffman codes); however it does have two types of dynamic Huffman blocks
- * ("verbatim" and "aligned").
- *
- * - LZX has a minimum match length of 2 rather than 3. Length 2 matches can be
- * useful, but generally only if the parser is smart about choosing them.
- *
- * - In LZX, offset slots 0 through 2 actually represent entries in an LRU queue
- * of match offsets. This is very useful for certain types of files, such as
- * binary files that have repeating records.
- */
-
-#ifdef HAVE_CONFIG_H
-# include "config.h"
-#endif
-
-#include "wimlib/compress_common.h"
-#include "wimlib/compressor_ops.h"
-#include "wimlib/endianness.h"
-#include "wimlib/error.h"
-#include "wimlib/lz_mf.h"
-#include "wimlib/lz_repsearch.h"
-#include "wimlib/lzx.h"
-#include "wimlib/util.h"
-
-#include <string.h>
-#include <limits.h>
-
-#define LZX_OPTIM_ARRAY_LENGTH 4096
-
-#define LZX_DIV_BLOCK_SIZE 32768
-
-#define LZX_CACHE_PER_POS 8
-
-#define LZX_MAX_MATCHES_PER_POS (LZX_MAX_MATCH_LEN - LZX_MIN_MATCH_LEN + 1)
-
-#define LZX_CACHE_LEN (LZX_DIV_BLOCK_SIZE * (LZX_CACHE_PER_POS + 1))
-
-struct lzx_compressor;
-
-/* Codewords for the LZX Huffman codes. */
-struct lzx_codewords {
- u32 main[LZX_MAINCODE_MAX_NUM_SYMBOLS];
- u32 len[LZX_LENCODE_NUM_SYMBOLS];
- u32 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS];
-};
-
-/* Codeword lengths (in bits) for the LZX Huffman codes.
- * A zero length means the corresponding codeword has zero frequency. */
-struct lzx_lens {
- u8 main[LZX_MAINCODE_MAX_NUM_SYMBOLS];
- u8 len[LZX_LENCODE_NUM_SYMBOLS];
- u8 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS];
-};
-
-/* Estimated cost, in bits, to output each symbol in the LZX Huffman codes. */
-struct lzx_costs {
- u8 main[LZX_MAINCODE_MAX_NUM_SYMBOLS];
- u8 len[LZX_LENCODE_NUM_SYMBOLS];
- u8 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS];
-};
-
-/* Codewords and lengths for the LZX Huffman codes. */
-struct lzx_codes {
- struct lzx_codewords codewords;
- struct lzx_lens lens;
-};
-
-/* Symbol frequency counters for the LZX Huffman codes. */
-struct lzx_freqs {
- u32 main[LZX_MAINCODE_MAX_NUM_SYMBOLS];
- u32 len[LZX_LENCODE_NUM_SYMBOLS];
- u32 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS];
-};
-
-/* Intermediate LZX match/literal format */
-struct lzx_item {
-
- /* Bits 0 - 9: Main symbol
- * Bits 10 - 17: Length symbol
- * Bits 18 - 22: Number of extra offset bits
- * Bits 23+ : Extra offset bits */
- u64 data;
-};
-
-/* Internal compression parameters */
-struct lzx_compressor_params {
- u32 (*choose_items_for_block)(struct lzx_compressor *, u32, u32);
- u32 num_optim_passes;
- enum lz_mf_algo mf_algo;
- u32 min_match_length;
- u32 nice_match_length;
- u32 max_search_depth;
-};
-
-/*
- * Match chooser position data:
- *
- * An array of these structures is used during the near-optimal 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_mc_pos_data {
-
- /* The cost, in bits, of the lowest-cost path that has been found to
- * reach this position. This can change as progressively lower cost
- * paths are found to reach this position. */
- u32 cost;
-#define MC_INFINITE_COST UINT32_MAX
-
- /* The match or literal that was taken to reach this position. This can
- * change as progressively lower cost paths are found to reach this
- * position.
- *
- * This variable is divided into two bitfields.
- *
- * Literals:
- * Low bits are 1, high bits are the literal.
- *
- * Explicit offset matches:
- * Low bits are the match length, high bits are the offset plus 2.
- *
- * Repeat offset matches:
- * Low bits are the match length, high bits are the queue index.
- */
- u32 mc_item_data;
-#define MC_OFFSET_SHIFT 9
-#define MC_LEN_MASK ((1 << MC_OFFSET_SHIFT) - 1)
-
- /* The state of the LZX recent match offsets queue at this position.
- * This is filled in lazily, only after the minimum-cost path to this
- * position is found.
- *
- * Note: the way we handle this adaptive state in the "minimum-cost"
- * parse is actually only an approximation. It's possible for the
- * globally optimal, minimum cost path to contain a prefix, ending at a
- * position, where that path prefix is *not* the minimum cost path to
- * that position. This can happen if such a path prefix results in a
- * different adaptive state which results in lower costs later. We do
- * not solve this problem; we only consider the lowest cost to reach
- * each position, which seems to be an acceptable approximation. */
- struct lzx_lru_queue queue _aligned_attribute(16);
-
-} _aligned_attribute(16);
-
-/* State of the LZX compressor */
-struct lzx_compressor {
-
- /* Internal compression parameters */
- struct lzx_compressor_params params;
-
- /* The preprocessed buffer of data being compressed */
- u8 *cur_window;
-
- /* Number of bytes of data to be compressed, which is the number of
- * bytes of data in @cur_window that are actually valid. */
- u32 cur_window_size;
-
- /* log2 order of the LZX window size for LZ match offset encoding
- * purposes. Will be >= LZX_MIN_WINDOW_ORDER and <=
- * LZX_MAX_WINDOW_ORDER.
- *
- * Note: 1 << @window_order is normally equal to @max_window_size,
- * a.k.a. the allocated size of @cur_window, but it will be greater than
- * @max_window_size in the event that the compressor was created with a
- * non-power-of-2 block size. (See lzx_get_window_order().) */
- unsigned window_order;
-
- /* Number of symbols in the main alphabet. This depends on
- * @window_order, since @window_order determines the maximum possible
- * offset. It does not, however, depend on the *actual* size of the
- * current data buffer being processed, which might be less than 1 <<
- * @window_order. */
- unsigned num_main_syms;
-
- /* Lempel-Ziv match-finder */
- struct lz_mf *mf;
-
- /* Match-finder wrapper functions and data for near-optimal parsing.
- *
- * When doing more than one match-choosing pass over the data, matches
- * found by the match-finder are cached to achieve a slight speedup when
- * the same matches are needed on subsequent passes. This is suboptimal
- * because different matches may be preferred with different cost
- * models, but it is a very worthwhile speedup. */
- unsigned (*get_matches_func)(struct lzx_compressor *, const struct lz_match **);
- void (*skip_bytes_func)(struct lzx_compressor *, unsigned n);
- u32 match_window_pos;
- u32 match_window_end;
- struct lz_match *cached_matches;
- struct lz_match *cache_ptr;
- struct lz_match *cache_limit;
-
- /* Position data for near-optimal parsing. */
- struct lzx_mc_pos_data optimum[LZX_OPTIM_ARRAY_LENGTH + LZX_MAX_MATCH_LEN];
-
- /* The cost model currently being used for near-optimal parsing. */
- struct lzx_costs costs;
-
- /* The current match offset LRU queue. */
- struct lzx_lru_queue queue;
-
- /* Frequency counters for the current block. */
- struct lzx_freqs freqs;
-
- /* The Huffman codes for the current and previous blocks. */
- struct lzx_codes codes[2];
-
- /* Which 'struct lzx_codes' is being used for the current block. The
- * other was used for the previous block (if this isn't the first
- * block). */
- unsigned int codes_index;
-
- /* Dummy lengths that are always 0. */
- struct lzx_lens zero_lens;
-
- /* Matches/literals that were chosen for the current block. */
- struct lzx_item chosen_items[LZX_DIV_BLOCK_SIZE];
-
- /* Table mapping match offset => offset slot for small offsets */
-#define LZX_NUM_FAST_OFFSETS 32768
- u8 offset_slot_fast[LZX_NUM_FAST_OFFSETS];
-};
-
-/*
- * Structure to keep track of the current state of sending bits to the
- * compressed output buffer.
- *
- * The LZX bitstream is encoded as a sequence of 16-bit coding units.
- */
-struct lzx_output_bitstream {
-
- /* Bits that haven't yet been written to the output buffer. */
- u32 bitbuf;
-
- /* Number of bits currently held in @bitbuf. */
- u32 bitcount;
-
- /* Pointer to the start of the output buffer. */
- le16 *start;
-
- /* Pointer to the position in the output buffer at which the next coding
- * unit should be written. */
- le16 *next;
-
- /* Pointer past the end of the output buffer. */
- le16 *end;
-};
-
-/*
- * Initialize the output bitstream.
- *
- * @os
- * The output bitstream structure to initialize.
- * @buffer
- * The buffer being written to.
- * @size
- * Size of @buffer, in bytes.
- */
-static void
-lzx_init_output(struct lzx_output_bitstream *os, void *buffer, u32 size)
-{
- os->bitbuf = 0;
- os->bitcount = 0;
- os->start = buffer;
- os->next = os->start;
- os->end = os->start + size / sizeof(le16);
-}
-
-/*
- * Write some bits to the output bitstream.
- *
- * The bits are given by the low-order @num_bits bits of @bits. Higher-order
- * bits in @bits cannot be set. At most 17 bits can be written at once.
- *
- * @max_num_bits is a compile-time constant that specifies the maximum number of
- * bits that can ever be written at the call site. Currently, it is used to
- * optimize away the conditional code for writing a second 16-bit coding unit
- * when writing fewer than 17 bits.
- *
- * If the output buffer space is exhausted, then the bits will be ignored, and
- * lzx_flush_output() will return 0 when it gets called.
- */
-static inline void
-lzx_write_varbits(struct lzx_output_bitstream *os,
- const u32 bits, const unsigned int num_bits,
- const unsigned int max_num_bits)
-{
- /* This code is optimized for LZX, which never needs to write more than
- * 17 bits at once. */
- LZX_ASSERT(num_bits <= 17);
- LZX_ASSERT(num_bits <= max_num_bits);
- LZX_ASSERT(os->bitcount <= 15);
-
- /* Add the bits to the bit buffer variable. @bitcount will be at most
- * 15, so there will be just enough space for the maximum possible
- * @num_bits of 17. */
- os->bitcount += num_bits;
- os->bitbuf = (os->bitbuf << num_bits) | bits;
-
- /* Check whether any coding units need to be written. */
- if (os->bitcount >= 16) {
-
- os->bitcount -= 16;
-
- /* Write a coding unit, unless it would overflow the buffer. */
- if (os->next != os->end)
- put_unaligned_u16_le(os->bitbuf >> os->bitcount, os->next++);
-
- /* If writing 17 bits, a second coding unit might need to be
- * written. But because 'max_num_bits' is a compile-time
- * constant, the compiler will optimize away this code at most
- * call sites. */
- if (max_num_bits == 17 && os->bitcount == 16) {
- if (os->next != os->end)
- put_unaligned_u16_le(os->bitbuf, os->next++);
- os->bitcount = 0;
- }
- }
-}
-
-/* Use when @num_bits is a compile-time constant. Otherwise use
- * lzx_write_varbits(). */
-static inline void
-lzx_write_bits(struct lzx_output_bitstream *os,
- const u32 bits, const unsigned int num_bits)
-{
- lzx_write_varbits(os, bits, num_bits, num_bits);
-}
-
-/*
- * Flush the last coding unit to the output buffer if needed. Return the total
- * number of bytes written to the output buffer, or 0 if an overflow occurred.
- */
-static u32
-lzx_flush_output(struct lzx_output_bitstream *os)
-{
- if (os->next == os->end)
- return 0;
-
- if (os->bitcount != 0)
- put_unaligned_u16_le(os->bitbuf << (16 - os->bitcount), os->next++);
-
- return (const u8 *)os->next - (const u8 *)os->start;
-}
-
-/* Build the main, length, and aligned offset Huffman codes used in LZX.
- *
- * This takes as input the frequency tables for each code and produces as output
- * a set of tables that map symbols to codewords and codeword lengths. */
-static void
-lzx_make_huffman_codes(const struct lzx_freqs *freqs, struct lzx_codes *codes,
- unsigned num_main_syms)
-{
- make_canonical_huffman_code(num_main_syms,
- LZX_MAX_MAIN_CODEWORD_LEN,
- freqs->main,
- codes->lens.main,
- codes->codewords.main);
-
- make_canonical_huffman_code(LZX_LENCODE_NUM_SYMBOLS,
- LZX_MAX_LEN_CODEWORD_LEN,
- freqs->len,
- codes->lens.len,
- codes->codewords.len);
-
- make_canonical_huffman_code(LZX_ALIGNEDCODE_NUM_SYMBOLS,
- LZX_MAX_ALIGNED_CODEWORD_LEN,
- freqs->aligned,
- codes->lens.aligned,
- codes->codewords.aligned);
-}
-
-static unsigned
-lzx_compute_precode_items(const u8 lens[restrict],
- const u8 prev_lens[restrict],
- const unsigned num_lens,
- u32 precode_freqs[restrict],
- unsigned precode_items[restrict])
-{
- unsigned *itemptr;
- unsigned run_start;
- unsigned run_end;
- unsigned extra_bits;
- int delta;
- u8 len;
-
- itemptr = precode_items;
- run_start = 0;
- do {
- /* Find the next run of codeword lengths. */
-
- /* len = the length being repeated */
- len = lens[run_start];
-
- run_end = run_start + 1;
-
- /* Fast case for a single length. */
- if (likely(run_end == num_lens || len != lens[run_end])) {
- delta = prev_lens[run_start] - len;
- if (delta < 0)
- delta += 17;
- precode_freqs[delta]++;
- *itemptr++ = delta;
- run_start++;
- continue;
- }
-
- /* Extend the run. */
- do {
- run_end++;
- } while (run_end != num_lens && len == lens[run_end]);
-
- if (len == 0) {
- /* Run of zeroes. */
-
- /* Symbol 18: RLE 20 to 51 zeroes at a time. */
- while ((run_end - run_start) >= 20) {
- extra_bits = min((run_end - run_start) - 20, 0x1f);
- precode_freqs[18]++;
- *itemptr++ = 18 | (extra_bits << 5);
- run_start += 20 + extra_bits;
- }
-
- /* Symbol 17: RLE 4 to 19 zeroes at a time. */
- if ((run_end - run_start) >= 4) {
- extra_bits = min((run_end - run_start) - 4, 0xf);
- precode_freqs[17]++;
- *itemptr++ = 17 | (extra_bits << 5);
- run_start += 4 + extra_bits;
- }
- } else {
-
- /* A run of nonzero lengths. */
-
- /* Symbol 19: RLE 4 to 5 of any length at a time. */
- while ((run_end - run_start) >= 4) {
- extra_bits = (run_end - run_start) > 4;
- delta = prev_lens[run_start] - len;
- if (delta < 0)
- delta += 17;
- precode_freqs[19]++;
- precode_freqs[delta]++;
- *itemptr++ = 19 | (extra_bits << 5) | (delta << 6);
- run_start += 4 + extra_bits;
- }
- }
-
- /* Output any remaining lengths without RLE. */
- while (run_start != run_end) {
- delta = prev_lens[run_start] - len;
- if (delta < 0)
- delta += 17;
- precode_freqs[delta]++;
- *itemptr++ = delta;
- run_start++;
- }
- } while (run_start != num_lens);
-
- return itemptr - precode_items;
-}
-
-/*
- * Output a Huffman code in the compressed form used in LZX.
- *
- * The Huffman code is represented in the output as a logical series of codeword
- * lengths from which the Huffman code, which must be in canonical form, can be
- * reconstructed.
- *
- * The codeword lengths are themselves compressed using a separate Huffman code,
- * the "precode", which contains a symbol for each possible codeword length in
- * the larger code as well as several special symbols to represent repeated
- * codeword lengths (a form of run-length encoding). The precode is itself
- * constructed in canonical form, and its codeword lengths are represented
- * literally in 20 4-bit fields that immediately precede the compressed codeword
- * lengths of the larger code.
- *
- * Furthermore, the codeword lengths of the larger code are actually represented
- * as deltas from the codeword lengths of the corresponding code in the previous
- * block.
- *
- * @os:
- * Bitstream to which to write the compressed Huffman code.
- * @lens:
- * The codeword lengths, indexed by symbol, in the Huffman code.
- * @prev_lens:
- * The codeword lengths, indexed by symbol, in the corresponding Huffman
- * code in the previous block, or all zeroes if this is the first block.
- * @num_lens:
- * The number of symbols in the Huffman code.
- */
-static void
-lzx_write_compressed_code(struct lzx_output_bitstream *os,
- const u8 lens[restrict],
- const u8 prev_lens[restrict],
- unsigned num_lens)
-{
- u32 precode_freqs[LZX_PRECODE_NUM_SYMBOLS];
- u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS];
- u32 precode_codewords[LZX_PRECODE_NUM_SYMBOLS];
- unsigned precode_items[num_lens];
- unsigned num_precode_items;
- unsigned precode_item;
- unsigned precode_sym;
- unsigned i;
-
- for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++)
- precode_freqs[i] = 0;
-
- /* Compute the "items" (RLE / literal tokens and extra bits) with which
- * the codeword lengths in the larger code will be output. */
- num_precode_items = lzx_compute_precode_items(lens,
- prev_lens,
- num_lens,
- precode_freqs,
- precode_items);
-
- /* Build the precode. */
- make_canonical_huffman_code(LZX_PRECODE_NUM_SYMBOLS,
- LZX_MAX_PRE_CODEWORD_LEN,
- precode_freqs, precode_lens,
- precode_codewords);
-
- /* Output the lengths of the codewords in the precode. */
- for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++)
- lzx_write_bits(os, precode_lens[i], LZX_PRECODE_ELEMENT_SIZE);
-
- /* Output the encoded lengths of the codewords in the larger code. */
- for (i = 0; i < num_precode_items; i++) {
- precode_item = precode_items[i];
- precode_sym = precode_item & 0x1F;
- lzx_write_varbits(os, precode_codewords[precode_sym],
- precode_lens[precode_sym],
- LZX_MAX_PRE_CODEWORD_LEN);
- if (precode_sym >= 17) {
- if (precode_sym == 17) {
- lzx_write_bits(os, precode_item >> 5, 4);
- } else if (precode_sym == 18) {
- lzx_write_bits(os, precode_item >> 5, 5);
- } else {
- lzx_write_bits(os, (precode_item >> 5) & 1, 1);
- precode_sym = precode_item >> 6;
- lzx_write_varbits(os, precode_codewords[precode_sym],
- precode_lens[precode_sym],
- LZX_MAX_PRE_CODEWORD_LEN);
- }
- }
- }
-}
-
-/* Output a match or literal. */
-static inline void
-lzx_write_item(struct lzx_output_bitstream *os, struct lzx_item item,
- unsigned ones_if_aligned, const struct lzx_codes *codes)
-{
- u64 data = item.data;
- unsigned main_symbol;
- unsigned len_symbol;
- unsigned num_extra_bits;
- u32 extra_bits;
-
- main_symbol = data & 0x3FF;
-
- lzx_write_varbits(os, codes->codewords.main[main_symbol],
- codes->lens.main[main_symbol],
- LZX_MAX_MAIN_CODEWORD_LEN);
-
- if (main_symbol < LZX_NUM_CHARS) /* Literal? */
- return;
-
- len_symbol = (data >> 10) & 0xFF;
-
- if (len_symbol != LZX_LENCODE_NUM_SYMBOLS) {
- lzx_write_varbits(os, codes->codewords.len[len_symbol],
- codes->lens.len[len_symbol],
- LZX_MAX_LEN_CODEWORD_LEN);
- }
-
- num_extra_bits = (data >> 18) & 0x1F;
- if (num_extra_bits == 0) /* Small offset or repeat offset match? */
- return;
-
- extra_bits = data >> 23;
-
- /*if (block_type == LZX_BLOCKTYPE_ALIGNED && num_extra_bits >= 3) {*/
- if ((num_extra_bits & ones_if_aligned) >= 3) {
-
- /* Aligned offset blocks: The low 3 bits of the extra offset
- * bits are Huffman-encoded using the aligned offset code. The
- * remaining bits are output literally. */
-
- lzx_write_varbits(os, extra_bits >> 3, num_extra_bits - 3, 14);
-
- lzx_write_varbits(os, codes->codewords.aligned[extra_bits & 7],
- codes->lens.aligned[extra_bits & 7],
- LZX_MAX_ALIGNED_CODEWORD_LEN);
- } else {
- /* Verbatim blocks, or fewer than 3 extra bits: All extra
- * offset bits are output literally. */
- lzx_write_varbits(os, extra_bits, num_extra_bits, 17);
- }
-}
-
-/*
- * Write all matches and literal bytes (which were precomputed) in an LZX
- * compressed block to the output bitstream in the final compressed
- * representation.
- *
- * @os
- * The output bitstream.
- * @block_type
- * The chosen type of the LZX compressed block (LZX_BLOCKTYPE_ALIGNED or
- * LZX_BLOCKTYPE_VERBATIM).
- * @items
- * The array of matches/literals to output.
- * @num_items
- * Number of matches/literals to output (length of @items).
- * @codes
- * The main, length, and aligned offset Huffman codes for the current
- * LZX compressed block.
- */
-static void
-lzx_write_items(struct lzx_output_bitstream *os, int block_type,
- const struct lzx_item items[], u32 num_items,
- const struct lzx_codes *codes)
-{
- unsigned ones_if_aligned = 0U - (block_type == LZX_BLOCKTYPE_ALIGNED);
-
- for (u32 i = 0; i < num_items; i++)
- lzx_write_item(os, items[i], ones_if_aligned, codes);
-}
-
-/* Write an LZX aligned offset or verbatim block to the output bitstream. */
-static void
-lzx_write_compressed_block(int block_type,
- u32 block_size,
- unsigned window_order,
- unsigned num_main_syms,
- struct lzx_item * chosen_items,
- u32 num_chosen_items,
- const struct lzx_codes * codes,
- const struct lzx_lens * prev_lens,
- struct lzx_output_bitstream * os)
-{
- LZX_ASSERT(block_type == LZX_BLOCKTYPE_ALIGNED ||
- block_type == LZX_BLOCKTYPE_VERBATIM);
-
- /* The first three bits indicate the type of block and are one of the
- * LZX_BLOCKTYPE_* constants. */
- lzx_write_bits(os, block_type, 3);
-
- /* Output the block size.
- *
- * The original LZX format seemed to always encode the block size in 3
- * bytes. However, the implementation in WIMGAPI, as used in WIM files,
- * uses the first bit to indicate whether the block is the default size
- * (32768) or a different size given explicitly by the next 16 bits.
- *
- * By default, this compressor uses a window size of 32768 and therefore
- * follows the WIMGAPI behavior. However, this compressor also supports
- * window sizes greater than 32768 bytes, which do not appear to be
- * supported by WIMGAPI. In such cases, we retain the default size bit
- * to mean a size of 32768 bytes but output non-default block size in 24
- * bits rather than 16. The compatibility of this behavior is unknown
- * because WIMs created with chunk size greater than 32768 can seemingly
- * only be opened by wimlib anyway. */
- if (block_size == LZX_DEFAULT_BLOCK_SIZE) {
- lzx_write_bits(os, 1, 1);
- } else {
- lzx_write_bits(os, 0, 1);
-
- if (window_order >= 16)
- lzx_write_bits(os, block_size >> 16, 8);
-
- lzx_write_bits(os, block_size & 0xFFFF, 16);
- }
-
- /* If it's an aligned offset block, output the aligned offset code. */
- if (block_type == LZX_BLOCKTYPE_ALIGNED) {
- for (int i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
- lzx_write_bits(os, codes->lens.aligned[i],
- LZX_ALIGNEDCODE_ELEMENT_SIZE);
- }
- }
-
- /* Output the main code (two parts). */
- lzx_write_compressed_code(os, codes->lens.main,
- prev_lens->main,
- LZX_NUM_CHARS);
- lzx_write_compressed_code(os, codes->lens.main + LZX_NUM_CHARS,
- prev_lens->main + LZX_NUM_CHARS,
- num_main_syms - LZX_NUM_CHARS);
-
- /* Output the length code. */
- lzx_write_compressed_code(os, codes->lens.len,
- prev_lens->len,
- LZX_LENCODE_NUM_SYMBOLS);
-
- /* Output the compressed matches and literals. */
- lzx_write_items(os, block_type, chosen_items, num_chosen_items, codes);
-}
-
-/* Don't allow matches to span the end of an LZX block. */
-static inline unsigned
-maybe_truncate_matches(struct lz_match matches[], unsigned num_matches,
- struct lzx_compressor *c)
-{
- if (c->match_window_end < c->cur_window_size && num_matches != 0) {
- u32 limit = c->match_window_end - c->match_window_pos;
-
- if (limit >= LZX_MIN_MATCH_LEN) {
-
- unsigned i = num_matches - 1;
- do {
- if (matches[i].len >= limit) {
- matches[i].len = limit;
-
- /* Truncation might produce multiple
- * matches with length 'limit'. Keep at
- * most 1. */
- num_matches = i + 1;
- }
- } while (i--);
- } else {
- num_matches = 0;
- }
- }
- return num_matches;
-}
-
-static unsigned
-lzx_get_matches_fillcache_singleblock(struct lzx_compressor *c,
- const struct lz_match **matches_ret)
-{
- struct lz_match *cache_ptr;
- struct lz_match *matches;
- unsigned num_matches;
-
- cache_ptr = c->cache_ptr;
- matches = cache_ptr + 1;
- if (likely(cache_ptr <= c->cache_limit)) {
- num_matches = lz_mf_get_matches(c->mf, matches);
- cache_ptr->len = num_matches;
- c->cache_ptr = matches + num_matches;
- } else {
- num_matches = 0;
- }
- c->match_window_pos++;
- *matches_ret = matches;
- return num_matches;
-}
-
-static unsigned
-lzx_get_matches_fillcache_multiblock(struct lzx_compressor *c,
- const struct lz_match **matches_ret)
-{
- struct lz_match *cache_ptr;
- struct lz_match *matches;
- unsigned num_matches;
-
- cache_ptr = c->cache_ptr;
- matches = cache_ptr + 1;
- if (likely(cache_ptr <= c->cache_limit)) {
- num_matches = lz_mf_get_matches(c->mf, matches);
- num_matches = maybe_truncate_matches(matches, num_matches, c);
- cache_ptr->len = num_matches;
- c->cache_ptr = matches + num_matches;
- } else {
- num_matches = 0;
- }
- c->match_window_pos++;
- *matches_ret = matches;
- return num_matches;
-}
-
-static unsigned
-lzx_get_matches_usecache(struct lzx_compressor *c,
- const struct lz_match **matches_ret)
-{
- struct lz_match *cache_ptr;
- struct lz_match *matches;
- unsigned num_matches;
-
- cache_ptr = c->cache_ptr;
- matches = cache_ptr + 1;
- if (cache_ptr <= c->cache_limit) {
- num_matches = cache_ptr->len;
- c->cache_ptr = matches + num_matches;
- } else {
- num_matches = 0;
- }
- c->match_window_pos++;
- *matches_ret = matches;
- return num_matches;
-}
-
-static unsigned
-lzx_get_matches_usecache_nocheck(struct lzx_compressor *c,
- const struct lz_match **matches_ret)
-{
- struct lz_match *cache_ptr;
- struct lz_match *matches;
- unsigned num_matches;
-
- cache_ptr = c->cache_ptr;
- matches = cache_ptr + 1;
- num_matches = cache_ptr->len;
- c->cache_ptr = matches + num_matches;
- c->match_window_pos++;
- *matches_ret = matches;
- return num_matches;
-}
-
-static unsigned
-lzx_get_matches_nocache_singleblock(struct lzx_compressor *c,
- const struct lz_match **matches_ret)
-{
- struct lz_match *matches;
- unsigned num_matches;
-
- matches = c->cache_ptr;
- num_matches = lz_mf_get_matches(c->mf, matches);
- c->match_window_pos++;
- *matches_ret = matches;
- return num_matches;
-}
-
-static unsigned
-lzx_get_matches_nocache_multiblock(struct lzx_compressor *c,
- const struct lz_match **matches_ret)
-{
- struct lz_match *matches;
- unsigned num_matches;
-
- matches = c->cache_ptr;
- num_matches = lz_mf_get_matches(c->mf, matches);
- num_matches = maybe_truncate_matches(matches, num_matches, c);
- c->match_window_pos++;
- *matches_ret = matches;
- return num_matches;
-}
-
-/*
- * Find matches at the next position in the window.
- *
- * This uses a wrapper function around the underlying match-finder.
- *
- * Returns the number of matches found and sets *matches_ret to point to the
- * matches array. The matches will be sorted by strictly increasing length and
- * offset.
- */
-static inline unsigned
-lzx_get_matches(struct lzx_compressor *c, const struct lz_match **matches_ret)
-{
- return (*c->get_matches_func)(c, matches_ret);
-}
-
-static void
-lzx_skip_bytes_fillcache(struct lzx_compressor *c, unsigned n)
-{
- struct lz_match *cache_ptr;
-
- cache_ptr = c->cache_ptr;
- c->match_window_pos += n;
- lz_mf_skip_positions(c->mf, n);
- if (cache_ptr <= c->cache_limit) {
- do {
- cache_ptr->len = 0;
- cache_ptr += 1;
- } while (--n && cache_ptr <= c->cache_limit);
- }
- c->cache_ptr = cache_ptr;
-}
-
-static void
-lzx_skip_bytes_usecache(struct lzx_compressor *c, unsigned n)
-{
- struct lz_match *cache_ptr;
-
- cache_ptr = c->cache_ptr;
- c->match_window_pos += n;
- if (cache_ptr <= c->cache_limit) {
- do {
- cache_ptr += 1 + cache_ptr->len;
- } while (--n && cache_ptr <= c->cache_limit);
- }
- c->cache_ptr = cache_ptr;
-}
-
-static void
-lzx_skip_bytes_usecache_nocheck(struct lzx_compressor *c, unsigned n)
-{
- struct lz_match *cache_ptr;
-
- cache_ptr = c->cache_ptr;
- c->match_window_pos += n;
- do {
- cache_ptr += 1 + cache_ptr->len;
- } while (--n);
- c->cache_ptr = cache_ptr;
-}
-
-static void
-lzx_skip_bytes_nocache(struct lzx_compressor *c, unsigned n)
-{
- c->match_window_pos += n;
- lz_mf_skip_positions(c->mf, n);
-}
-
-/*
- * Skip the specified number of positions in the window (don't search for
- * matches at them).
- *
- * This uses a wrapper function around the underlying match-finder.
- */
-static inline void
-lzx_skip_bytes(struct lzx_compressor *c, unsigned n)
-{
- return (*c->skip_bytes_func)(c, n);
-}
-
-/* Tally, and optionally record, the specified literal byte. */
-static inline void
-lzx_declare_literal(struct lzx_compressor *c, unsigned literal,
- struct lzx_item **next_chosen_item)
-{
- unsigned main_symbol = literal;
-
- c->freqs.main[main_symbol]++;
-
- if (next_chosen_item) {
- *(*next_chosen_item)++ = (struct lzx_item) {
- .data = main_symbol,
- };
- }
-}
-
-/* Tally, and optionally record, the specified repeat offset match. */
-static inline void
-lzx_declare_repeat_offset_match(struct lzx_compressor *c,
- unsigned len, unsigned rep_index,
- struct lzx_item **next_chosen_item)
-{
- unsigned len_header;
- unsigned main_symbol;
- unsigned len_symbol;
-
- if (len - LZX_MIN_MATCH_LEN < LZX_NUM_PRIMARY_LENS) {
- len_header = len - LZX_MIN_MATCH_LEN;
- len_symbol = LZX_LENCODE_NUM_SYMBOLS;
- } else {
- len_header = LZX_NUM_PRIMARY_LENS;
- len_symbol = len - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS;
- c->freqs.len[len_symbol]++;
- }
-
- main_symbol = LZX_NUM_CHARS + ((rep_index << 3) | len_header);
-
- c->freqs.main[main_symbol]++;
-
- if (next_chosen_item) {
- *(*next_chosen_item)++ = (struct lzx_item) {
- .data = (u64)main_symbol | ((u64)len_symbol << 10),
- };
- }
-}
-
-/* Tally, and optionally record, the specified explicit offset match. */
-static inline void
-lzx_declare_explicit_offset_match(struct lzx_compressor *c, unsigned len, u32 offset,
- struct lzx_item **next_chosen_item)
-{
- unsigned len_header;
- unsigned main_symbol;
- unsigned len_symbol;
- unsigned offset_slot;
- unsigned num_extra_bits;
- u32 extra_bits;
-
- if (len - LZX_MIN_MATCH_LEN < LZX_NUM_PRIMARY_LENS) {
- len_header = len - LZX_MIN_MATCH_LEN;
- len_symbol = LZX_LENCODE_NUM_SYMBOLS;
- } else {
- len_header = LZX_NUM_PRIMARY_LENS;
- len_symbol = len - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS;
- c->freqs.len[len_symbol]++;
- }
-
- offset_slot = lzx_get_offset_slot_raw(offset + LZX_OFFSET_OFFSET);
-
- main_symbol = LZX_NUM_CHARS + ((offset_slot << 3) | len_header);
-
- c->freqs.main[main_symbol]++;
-
- if (offset_slot >= 8)
- c->freqs.aligned[(offset + LZX_OFFSET_OFFSET) & 7]++;
-
- if (next_chosen_item) {
-
- num_extra_bits = lzx_extra_offset_bits[offset_slot];
-
- extra_bits = (offset + LZX_OFFSET_OFFSET) -
- lzx_offset_slot_base[offset_slot];
-
- *(*next_chosen_item)++ = (struct lzx_item) {
- .data = (u64)main_symbol |
- ((u64)len_symbol << 10) |
- ((u64)num_extra_bits << 18) |
- ((u64)extra_bits << 23),
- };
- }
-}
-
-/* Tally, and optionally record, the specified match or literal. */
-static inline void
-lzx_declare_item(struct lzx_compressor *c, u32 mc_item_data,
- struct lzx_item **next_chosen_item)
-{
- u32 len = mc_item_data & MC_LEN_MASK;
- u32 offset_data = mc_item_data >> MC_OFFSET_SHIFT;
-
- if (len == 1)
- lzx_declare_literal(c, offset_data, next_chosen_item);
- else if (offset_data < LZX_NUM_RECENT_OFFSETS)
- lzx_declare_repeat_offset_match(c, len, offset_data,
- next_chosen_item);
- else
- lzx_declare_explicit_offset_match(c, len,
- offset_data - LZX_OFFSET_OFFSET,
- next_chosen_item);
-}
-
-static inline void
-lzx_record_item_list(struct lzx_compressor *c,
- struct lzx_mc_pos_data *cur_optimum_ptr,
- struct lzx_item **next_chosen_item)
-{
- struct lzx_mc_pos_data *end_optimum_ptr;
- u32 saved_item;
- u32 item;
-
- /* The list is currently in reverse order (last item to first item).
- * Reverse it. */
- end_optimum_ptr = cur_optimum_ptr;
- saved_item = cur_optimum_ptr->mc_item_data;
- do {
- item = saved_item;
- cur_optimum_ptr -= item & MC_LEN_MASK;
- saved_item = cur_optimum_ptr->mc_item_data;
- cur_optimum_ptr->mc_item_data = item;
- } while (cur_optimum_ptr != c->optimum);
-
- /* Walk the list of items from beginning to end, tallying and recording
- * each item. */
- do {
- lzx_declare_item(c, cur_optimum_ptr->mc_item_data, next_chosen_item);
- cur_optimum_ptr += (cur_optimum_ptr->mc_item_data) & MC_LEN_MASK;
- } while (cur_optimum_ptr != end_optimum_ptr);
-}
-
-static inline void
-lzx_tally_item_list(struct lzx_compressor *c, struct lzx_mc_pos_data *cur_optimum_ptr)
-{
- /* Since we're just tallying the items, we don't need to reverse the
- * list. Processing the items in reverse order is fine. */
- do {
- lzx_declare_item(c, cur_optimum_ptr->mc_item_data, NULL);
- cur_optimum_ptr -= (cur_optimum_ptr->mc_item_data & MC_LEN_MASK);
- } while (cur_optimum_ptr != c->optimum);
-}
-
-/* Tally, and optionally (if next_chosen_item != NULL) record, in order, all
- * items in the current list of items found by the match-chooser. */
-static void
-lzx_declare_item_list(struct lzx_compressor *c, struct lzx_mc_pos_data *cur_optimum_ptr,
- struct lzx_item **next_chosen_item)
-{
- if (next_chosen_item)
- lzx_record_item_list(c, cur_optimum_ptr, next_chosen_item);
- else
- lzx_tally_item_list(c, cur_optimum_ptr);
-}
-
-/* Set the cost model @c->costs from the Huffman codeword lengths specified in
- * @lens.
- *
- * The cost model and codeword lengths are almost the same thing, but the
- * Huffman codewords with length 0 correspond to symbols with zero frequency
- * that still need to be assigned actual costs. The specific values assigned
- * are arbitrary, but they should be fairly high (near the maximum codeword
- * length) to take into account the fact that uses of these symbols are expected
- * to be rare. */
-static void
-lzx_set_costs(struct lzx_compressor *c, const struct lzx_lens * lens)
-{
- unsigned i;
-
- /* Main code */
- for (i = 0; i < c->num_main_syms; i++)
- c->costs.main[i] = lens->main[i] ? lens->main[i] : 15;
-
- /* Length code */
- for (i = 0; i < LZX_LENCODE_NUM_SYMBOLS; i++)
- c->costs.len[i] = lens->len[i] ? lens->len[i] : 15;
-
- /* Aligned offset code */
- for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++)
- c->costs.aligned[i] = lens->aligned[i] ? lens->aligned[i] : 7;
-}
-
-/* Set default LZX Huffman symbol costs to bootstrap the iterative optimization
- * algorithm. */
-static void
-lzx_set_default_costs(struct lzx_costs * costs, unsigned num_main_syms)
-{
- unsigned i;
-
- /* Main code (part 1): Literal symbols */
- for (i = 0; i < LZX_NUM_CHARS; i++)
- costs->main[i] = 8;
-
- /* Main code (part 2): Match header symbols */
- for (; i < num_main_syms; i++)
- costs->main[i] = 10;
-
- /* Length code */
- for (i = 0; i < LZX_LENCODE_NUM_SYMBOLS; i++)
- costs->len[i] = 8;
-
- /* Aligned offset code */
- for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++)
- costs->aligned[i] = 3;
-}
-
-/* Return the cost, in bits, to output a literal byte using the specified cost
- * model. */
-static inline u32
-lzx_literal_cost(unsigned literal, const struct lzx_costs * costs)
-{
- return costs->main[literal];
-}
-
-/* Return the cost, in bits, to output a match of the specified length and
- * offset slot using the specified cost model. Does not take into account
- * extra offset bits. */
-static inline u32
-lzx_match_cost_raw(unsigned len, unsigned offset_slot,
- const struct lzx_costs *costs)
-{
- u32 cost;
- unsigned len_header;
- unsigned main_symbol;
-
- if (len - LZX_MIN_MATCH_LEN < LZX_NUM_PRIMARY_LENS) {
- len_header = len - LZX_MIN_MATCH_LEN;
- cost = 0;
- } else {
- len_header = LZX_NUM_PRIMARY_LENS;
-
- /* Account for length symbol. */
- cost = costs->len[len - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS];
- }
-
- /* Account for main symbol. */
- main_symbol = LZX_NUM_CHARS + ((offset_slot << 3) | len_header);
- cost += costs->main[main_symbol];
-
- return cost;
-}
-
-/* Equivalent to lzx_match_cost_raw(), but assumes the length is small enough
- * that it doesn't require a length symbol. */
-static inline u32
-lzx_match_cost_raw_smalllen(unsigned len, unsigned offset_slot,
- const struct lzx_costs *costs)
-{
- LZX_ASSERT(len < LZX_MIN_MATCH_LEN + LZX_NUM_PRIMARY_LENS);
- return costs->main[LZX_NUM_CHARS +
- ((offset_slot << 3) | (len - LZX_MIN_MATCH_LEN))];
-}
-
-/*
- * Consider coding the match at repeat offset index @rep_idx. Consider each
- * length from the minimum (2) to the full match length (@rep_len).
- */
-static inline void
-lzx_consider_repeat_offset_match(struct lzx_compressor *c,
- struct lzx_mc_pos_data *cur_optimum_ptr,
- unsigned rep_len, unsigned rep_idx)
-{
- u32 base_cost = cur_optimum_ptr->cost;
- u32 cost;
- unsigned len;
-
-#if 1 /* Optimized version */
-
- if (rep_len < LZX_MIN_MATCH_LEN + LZX_NUM_PRIMARY_LENS) {
- /* All lengths being considered are small. */
- len = 2;
- do {
- cost = base_cost +
- lzx_match_cost_raw_smalllen(len, rep_idx, &c->costs);
- if (cost < (cur_optimum_ptr + len)->cost) {
- (cur_optimum_ptr + len)->mc_item_data =
- (rep_idx << MC_OFFSET_SHIFT) | len;
- (cur_optimum_ptr + len)->cost = cost;
- }
- } while (++len <= rep_len);
- } else {
- /* Some lengths being considered are small, and some are big.
- * Start with the optimized loop for small lengths, then switch
- * to the optimized loop for big lengths. */
- len = 2;
- do {
- cost = base_cost +
- lzx_match_cost_raw_smalllen(len, rep_idx, &c->costs);
- if (cost < (cur_optimum_ptr + len)->cost) {
- (cur_optimum_ptr + len)->mc_item_data =
- (rep_idx << MC_OFFSET_SHIFT) | len;
- (cur_optimum_ptr + len)->cost = cost;
- }
- } while (++len < LZX_MIN_MATCH_LEN + LZX_NUM_PRIMARY_LENS);
-
- /* The main symbol is now fixed. */
- base_cost += c->costs.main[LZX_NUM_CHARS +
- ((rep_idx << 3) | LZX_NUM_PRIMARY_LENS)];
- do {
- cost = base_cost +
- c->costs.len[len - LZX_MIN_MATCH_LEN -
- LZX_NUM_PRIMARY_LENS];
- if (cost < (cur_optimum_ptr + len)->cost) {
- (cur_optimum_ptr + len)->mc_item_data =
- (rep_idx << MC_OFFSET_SHIFT) | len;
- (cur_optimum_ptr + len)->cost = cost;
- }
- } while (++len <= rep_len);
- }
-
-#else /* Unoptimized version */
-
- len = 2;
- do {
- cost = base_cost +
- lzx_match_cost_raw(len, rep_idx, &c->costs);
- if (cost < (cur_optimum_ptr + len)->cost) {
- (cur_optimum_ptr + len)->mc_item_data =
- (rep_idx << MC_OFFSET_SHIFT) | len;
- (cur_optimum_ptr + len)->cost = cost;
- }
- } while (++len <= rep_len);
-#endif
-}
-
-/*
- * Consider coding each match in @matches as an explicit offset match.
- *
- * @matches must be sorted by strictly increasing length and strictly
- * increasing offset. This is guaranteed by the match-finder.
- *
- * We consider each length from the minimum (2) to the longest
- * (matches[num_matches - 1].len). For each length, we consider only
- * the smallest offset for which that length is available. Although
- * this is not guaranteed to be optimal due to the possibility of a
- * larger offset costing less than a smaller offset to code, this is a
- * very useful heuristic.
- */
-static inline void
-lzx_consider_explicit_offset_matches(struct lzx_compressor *c,
- struct lzx_mc_pos_data *cur_optimum_ptr,
- const struct lz_match matches[],
- unsigned num_matches)
-{
- LZX_ASSERT(num_matches > 0);
-
- unsigned i;
- unsigned len;
- unsigned offset_slot;
- u32 position_cost;
- u32 cost;
- u32 offset_data;
-
-
-#if 1 /* Optimized version */
-
- if (matches[num_matches - 1].offset < LZX_NUM_FAST_OFFSETS) {
-
- /*
- * Offset is small; the offset slot can be looked up directly in
- * c->offset_slot_fast.
- *
- * Additional optimizations:
- *
- * - Since the offset is small, it falls in the exponential part
- * of the offset slot bases and the number of extra offset
- * bits can be calculated directly as (offset_slot >> 1) - 1.
- *
- * - Just consider the number of extra offset bits; don't
- * account for the aligned offset code. Usually this has
- * almost no effect on the compression ratio.
- *
- * - Start out in a loop optimized for small lengths. When the
- * length becomes high enough that a length symbol will be
- * needed, jump into a loop optimized for big lengths.
- */
-
- LZX_ASSERT(offset_slot <= 37); /* for extra bits formula */
-
- len = 2;
- i = 0;
- do {
- offset_slot = c->offset_slot_fast[matches[i].offset];
- position_cost = cur_optimum_ptr->cost +
- ((offset_slot >> 1) - 1);
- offset_data = matches[i].offset + LZX_OFFSET_OFFSET;
- do {
- if (len >= LZX_MIN_MATCH_LEN + LZX_NUM_PRIMARY_LENS)
- goto biglen;
- cost = position_cost +
- lzx_match_cost_raw_smalllen(len, offset_slot,
- &c->costs);
- if (cost < (cur_optimum_ptr + len)->cost) {
- (cur_optimum_ptr + len)->cost = cost;
- (cur_optimum_ptr + len)->mc_item_data =
- (offset_data << MC_OFFSET_SHIFT) | len;
- }
- } while (++len <= matches[i].len);
- } while (++i != num_matches);
-
- return;
-
- do {
- offset_slot = c->offset_slot_fast[matches[i].offset];
- biglen:
- position_cost = cur_optimum_ptr->cost +
- ((offset_slot >> 1) - 1) +
- c->costs.main[LZX_NUM_CHARS +
- ((offset_slot << 3) |
- LZX_NUM_PRIMARY_LENS)];
- offset_data = matches[i].offset + LZX_OFFSET_OFFSET;
- do {
- cost = position_cost +
- c->costs.len[len - LZX_MIN_MATCH_LEN -
- LZX_NUM_PRIMARY_LENS];
- if (cost < (cur_optimum_ptr + len)->cost) {
- (cur_optimum_ptr + len)->cost = cost;
- (cur_optimum_ptr + len)->mc_item_data =
- (offset_data << MC_OFFSET_SHIFT) | len;
- }
- } while (++len <= matches[i].len);
- } while (++i != num_matches);
- } else {
- len = 2;
- i = 0;
- do {
- offset_data = matches[i].offset + LZX_OFFSET_OFFSET;
- offset_slot = lzx_get_offset_slot_raw(offset_data);
- position_cost = cur_optimum_ptr->cost +
- lzx_extra_offset_bits[offset_slot];
- do {
- cost = position_cost +
- lzx_match_cost_raw(len, offset_slot, &c->costs);
- if (cost < (cur_optimum_ptr + len)->cost) {
- (cur_optimum_ptr + len)->cost = cost;
- (cur_optimum_ptr + len)->mc_item_data =
- (offset_data << MC_OFFSET_SHIFT) | len;
- }
- } while (++len <= matches[i].len);
- } while (++i != num_matches);
- }
-
-#else /* Unoptimized version */
-
- unsigned num_extra_bits;
-
- len = 2;
- i = 0;
- do {
- offset_data = matches[i].offset + LZX_OFFSET_OFFSET;
- position_cost = cur_optimum_ptr->cost;
- offset_slot = lzx_get_offset_slot_raw(offset_data);
- num_extra_bits = lzx_extra_offset_bits[offset_slot];
- if (num_extra_bits >= 3) {
- position_cost += num_extra_bits - 3;
- position_cost += c->costs.aligned[offset_data & 7];
- } else {
- position_cost += num_extra_bits;
- }
- do {
- cost = position_cost +
- lzx_match_cost_raw(len, offset_slot, &c->costs);
- if (cost < (cur_optimum_ptr + len)->cost) {
- (cur_optimum_ptr + len)->cost = cost;
- (cur_optimum_ptr + len)->mc_item_data =
- (offset_data << MC_OFFSET_SHIFT) | len;
- }
- } while (++len <= matches[i].len);
- } while (++i != num_matches);
-#endif
-}
-
-/*
- * Search for repeat offset matches with the current position.
- */
-static inline unsigned
-lzx_repsearch(const u8 * const strptr, const u32 bytes_remaining,
- const struct lzx_lru_queue *queue, unsigned *rep_max_idx_ret)
-{
- BUILD_BUG_ON(LZX_NUM_RECENT_OFFSETS != 3);
- return lz_repsearch3(strptr, min(bytes_remaining, LZX_MAX_MATCH_LEN),
- queue->R, rep_max_idx_ret);
-}
-
-/*
- * The main near-optimal parsing routine.
- *
- * Briefly, the algorithm does an approximate minimum-cost path search to find a
- * "near-optimal" sequence of matches and literals to output, based on the
- * current cost model. The algorithm steps forward, position by position (byte
- * by byte), and updates the minimum cost path to reach each later position that
- * can be reached using a match or literal from the current position. This is
- * essentially Dijkstra's algorithm in disguise: the graph nodes are positions,
- * the graph edges are possible matches/literals to code, and the cost of each
- * edge is the estimated number of bits that will be required to output the
- * corresponding match or literal. But one difference is that we actually
- * compute the lowest-cost path in pieces, where each piece is terminated when
- * there are no choices to be made.
- *
- * This function will run this algorithm on the portion of the window from
- * &c->cur_window[c->match_window_pos] to &c->cur_window[c->match_window_end].
- *
- * On entry, c->queue must be the current state of the match offset LRU queue,
- * and c->costs must be the current cost model to use for Huffman symbols.
- *
- * On exit, c->queue will be the state that the LRU queue would be in if the
- * chosen items were to be coded.
- *
- * If next_chosen_item != NULL, then all items chosen will be recorded (saved in
- * the chosen_items array). Otherwise, all items chosen will only be tallied
- * (symbol frequencies tallied in c->freqs).
- */
-static void
-lzx_optim_pass(struct lzx_compressor *c, struct lzx_item **next_chosen_item)
-{
- const u8 *block_end;
- struct lzx_lru_queue *begin_queue;
- const u8 *window_ptr;
- struct lzx_mc_pos_data *cur_optimum_ptr;
- struct lzx_mc_pos_data *end_optimum_ptr;
- const struct lz_match *matches;
- unsigned num_matches;
- unsigned longest_len;
- unsigned rep_max_len;
- unsigned rep_max_idx;
- unsigned literal;
- unsigned len;
- u32 cost;
- u32 offset_data;
-
- block_end = &c->cur_window[c->match_window_end];
- begin_queue = &c->queue;
-begin:
- /* Start building a new list of items, which will correspond to the next
- * piece of the overall minimum-cost path.
- *
- * *begin_queue is the current state of the match offset LRU queue. */
-
- window_ptr = &c->cur_window[c->match_window_pos];
-
- if (window_ptr == block_end) {
- c->queue = *begin_queue;
- return;
- }
-
- cur_optimum_ptr = c->optimum;
- cur_optimum_ptr->cost = 0;
- cur_optimum_ptr->queue = *begin_queue;
-
- end_optimum_ptr = cur_optimum_ptr;
-
- /* The following loop runs once for each per byte in the window, except
- * in a couple shortcut cases. */
- for (;;) {
-
- /* Find explicit offset matches with the current position. */
- num_matches = lzx_get_matches(c, &matches);
-
- if (num_matches) {
- /*
- * Find the longest repeat offset match with the current
- * position.
- *
- * Heuristics:
- *
- * - Only search for repeat offset matches if the
- * match-finder already found at least one match.
- *
- * - Only consider the longest repeat offset match. It
- * seems to be rare for the optimal parse to include a
- * repeat offset match that doesn't have the longest
- * length (allowing for the possibility that not all
- * of that length is actually used).
- */
- rep_max_len = lzx_repsearch(window_ptr,
- block_end - window_ptr,
- &cur_optimum_ptr->queue,
- &rep_max_idx);
-
- if (rep_max_len) {
- /* If there's a very long repeat offset match,
- * choose it immediately. */
- if (rep_max_len >= c->params.nice_match_length) {
-
- swap(cur_optimum_ptr->queue.R[0],
- cur_optimum_ptr->queue.R[rep_max_idx]);
- begin_queue = &cur_optimum_ptr->queue;
-
- cur_optimum_ptr += rep_max_len;
- cur_optimum_ptr->mc_item_data =
- (rep_max_idx << MC_OFFSET_SHIFT) |
- rep_max_len;
-
- lzx_skip_bytes(c, rep_max_len - 1);
- break;
- }
-
- /* If reaching any positions for the first time,
- * initialize their costs to "infinity". */
- while (end_optimum_ptr < cur_optimum_ptr + rep_max_len)
- (++end_optimum_ptr)->cost = MC_INFINITE_COST;
-
- /* Consider coding a repeat offset match. */
- lzx_consider_repeat_offset_match(c,
- cur_optimum_ptr,
- rep_max_len,
- rep_max_idx);
- }
-
- longest_len = matches[num_matches - 1].len;
-
- /* If there's a very long explicit offset match, choose
- * it immediately. */
- if (longest_len >= c->params.nice_match_length) {
-
- cur_optimum_ptr->queue.R[2] =
- cur_optimum_ptr->queue.R[1];
- cur_optimum_ptr->queue.R[1] =
- cur_optimum_ptr->queue.R[0];
- cur_optimum_ptr->queue.R[0] =
- matches[num_matches - 1].offset;
- begin_queue = &cur_optimum_ptr->queue;
-
- offset_data = matches[num_matches - 1].offset +
- LZX_OFFSET_OFFSET;
- cur_optimum_ptr += longest_len;
- cur_optimum_ptr->mc_item_data =
- (offset_data << MC_OFFSET_SHIFT) |
- longest_len;
-
- lzx_skip_bytes(c, longest_len - 1);
- break;
- }
-
- /* If reaching any positions for the first time,
- * initialize their costs to "infinity". */
- while (end_optimum_ptr < cur_optimum_ptr + longest_len)
- (++end_optimum_ptr)->cost = MC_INFINITE_COST;
-
- /* Consider coding an explicit offset match. */
- lzx_consider_explicit_offset_matches(c, cur_optimum_ptr,
- matches, num_matches);
- } else {
- /* No matches found. The only choice at this position
- * is to code a literal. */
-
- if (end_optimum_ptr == cur_optimum_ptr) {
- #if 1
- /* Optimization for single literals. */
- if (likely(cur_optimum_ptr == c->optimum)) {
- lzx_declare_literal(c, *window_ptr++,
- next_chosen_item);
- if (window_ptr == block_end) {
- c->queue = cur_optimum_ptr->queue;
- return;
- }
- continue;
- }
- #endif
- (++end_optimum_ptr)->cost = MC_INFINITE_COST;
- }
- }
-
- /* Consider coding a literal.
-
- * To avoid an extra unpredictable brench, actually checking the
- * preferability of coding a literal is integrated into the
- * queue update code below. */
- literal = *window_ptr++;
- cost = cur_optimum_ptr->cost + lzx_literal_cost(literal, &c->costs);
-
- /* Advance to the next position. */
- cur_optimum_ptr++;
-
- /* The lowest-cost path to the current position is now known.
- * Finalize the recent offsets queue that results from taking
- * this lowest-cost path. */
-
- if (cost < cur_optimum_ptr->cost) {
- /* Literal: queue remains unchanged. */
- cur_optimum_ptr->cost = cost;
- cur_optimum_ptr->mc_item_data = (literal << MC_OFFSET_SHIFT) | 1;
- cur_optimum_ptr->queue = (cur_optimum_ptr - 1)->queue;
- } else {
- /* Match: queue update is needed. */
- len = cur_optimum_ptr->mc_item_data & MC_LEN_MASK;
- offset_data = cur_optimum_ptr->mc_item_data >> MC_OFFSET_SHIFT;
- if (offset_data >= LZX_NUM_RECENT_OFFSETS) {
- /* Explicit offset match: offset is inserted at front */
- cur_optimum_ptr->queue.R[0] = offset_data - LZX_OFFSET_OFFSET;
- cur_optimum_ptr->queue.R[1] = (cur_optimum_ptr - len)->queue.R[0];
- cur_optimum_ptr->queue.R[2] = (cur_optimum_ptr - len)->queue.R[1];
- } else {
- /* Repeat offset match: offset is swapped to front */
- cur_optimum_ptr->queue = (cur_optimum_ptr - len)->queue;
- swap(cur_optimum_ptr->queue.R[0],
- cur_optimum_ptr->queue.R[offset_data]);
- }
- }
-
- /*
- * This loop will terminate when either of the following
- * conditions is true:
- *
- * (1) cur_optimum_ptr == end_optimum_ptr
- *
- * There are no paths that extend beyond the current
- * position. In this case, any path to a later position
- * must pass through the current position, so we can go
- * ahead and choose the list of items that led to this
- * position.
- *
- * (2) cur_optimum_ptr == &c->optimum[LZX_OPTIM_ARRAY_LENGTH]
- *
- * This bounds the number of times the algorithm can step
- * forward before it is guaranteed to start choosing items.
- * This limits the memory usage. But
- * LZX_OPTIM_ARRAY_LENGTH is high enough that on most
- * inputs this limit is never reached.
- *
- * Note: no check for end-of-block is needed because
- * end-of-block will trigger condition (1).
- */
- if (cur_optimum_ptr == end_optimum_ptr ||
- cur_optimum_ptr == &c->optimum[LZX_OPTIM_ARRAY_LENGTH])
- {
- begin_queue = &cur_optimum_ptr->queue;
- break;
- }
- }
-
- /* Choose the current list of items that constitute the minimum-cost
- * path to the current position. */
- lzx_declare_item_list(c, cur_optimum_ptr, next_chosen_item);
- goto begin;
-}
-
-/* Fast heuristic scoring for lazy parsing: how "good" is this match? */
-static inline unsigned
-lzx_explicit_offset_match_score(unsigned len, u32 adjusted_offset)
-{
- unsigned score = len;
-
- if (adjusted_offset < 2048)
- score++;
-
- if (adjusted_offset < 1024)
- score++;
-
- return score;
-}
-
-static inline unsigned
-lzx_repeat_offset_match_score(unsigned len, unsigned slot)
-{
- return len + 3;
-}
-
-/* Lazy parsing */
-static u32
-lzx_choose_lazy_items_for_block(struct lzx_compressor *c,
- u32 block_start_pos, u32 block_size)
-{
- const u8 *window_ptr;
- const u8 *block_end;
- struct lz_mf *mf;
- struct lz_match *matches;
- unsigned num_matches;
- unsigned cur_len;
- u32 cur_offset_data;
- unsigned cur_score;
- unsigned rep_max_len;
- unsigned rep_max_idx;
- unsigned rep_score;
- unsigned prev_len;
- unsigned prev_score;
- u32 prev_offset_data;
- unsigned skip_len;
- struct lzx_item *next_chosen_item;
-
- window_ptr = &c->cur_window[block_start_pos];
- block_end = window_ptr + block_size;
- matches = c->cached_matches;
- mf = c->mf;
- next_chosen_item = c->chosen_items;
-
- prev_len = 0;
- prev_offset_data = 0;
- prev_score = 0;
-
- while (window_ptr != block_end) {
-
- /* Find explicit offset matches with the current position. */
- num_matches = lz_mf_get_matches(mf, matches);
- window_ptr++;
-
- if (num_matches == 0 ||
- (matches[num_matches - 1].len == 3 &&
- matches[num_matches - 1].offset >= 8192 - LZX_OFFSET_OFFSET &&
- matches[num_matches - 1].offset != c->queue.R[0] &&
- matches[num_matches - 1].offset != c->queue.R[1] &&
- matches[num_matches - 1].offset != c->queue.R[2]))
- {
- /* No match found, or the only match found was a distant
- * length 3 match. Output the previous match if there
- * is one; otherwise output a literal. */
-
- no_match_found:
-
- if (prev_len) {
- skip_len = prev_len - 2;
- goto output_prev_match;
- } else {
- lzx_declare_literal(c, *(window_ptr - 1),
- &next_chosen_item);
- continue;
- }
- }
-
- /* Find the longest repeat offset match with the current
- * position. */
- if (likely(block_end - (window_ptr - 1) >= 2)) {
- rep_max_len = lzx_repsearch((window_ptr - 1),
- block_end - (window_ptr - 1),
- &c->queue, &rep_max_idx);
- } else {
- rep_max_len = 0;
- }
-
- cur_len = matches[num_matches - 1].len;
- cur_offset_data = matches[num_matches - 1].offset + LZX_OFFSET_OFFSET;
- cur_score = lzx_explicit_offset_match_score(cur_len, cur_offset_data);
-
- /* Select the better of the explicit and repeat offset matches. */
- if (rep_max_len >= 3 &&
- (rep_score = lzx_repeat_offset_match_score(rep_max_len,
- rep_max_idx)) >= cur_score)
- {
- cur_len = rep_max_len;
- cur_offset_data = rep_max_idx;
- cur_score = rep_score;
- }
-
- if (unlikely(cur_len > block_end - (window_ptr - 1))) {
- /* Nearing end of block. */
- cur_len = block_end - (window_ptr - 1);
- if (cur_len < 3)
- goto no_match_found;
- }
-
- if (prev_len == 0 || cur_score > prev_score) {
- /* No previous match, or the current match is better
- * than the previous match.
- *
- * If there's a previous match, then output a literal in
- * its place.
- *
- * In both cases, if the current match is very long,
- * then output it immediately. Otherwise, attempt a
- * lazy match by waiting to see if there's a better
- * match at the next position. */
-
- if (prev_len)
- lzx_declare_literal(c, *(window_ptr - 2), &next_chosen_item);
-
- prev_len = cur_len;
- prev_offset_data = cur_offset_data;
- prev_score = cur_score;
-
- if (prev_len >= c->params.nice_match_length) {
- skip_len = prev_len - 1;
- goto output_prev_match;
- }
- continue;
- }
-
- /* Current match is not better than the previous match, so
- * output the previous match. */
-
- skip_len = prev_len - 2;
-
- output_prev_match:
- if (prev_offset_data < LZX_NUM_RECENT_OFFSETS) {
- lzx_declare_repeat_offset_match(c, prev_len,
- prev_offset_data,
- &next_chosen_item);
- swap(c->queue.R[0], c->queue.R[prev_offset_data]);
- } else {
- lzx_declare_explicit_offset_match(c, prev_len,
- prev_offset_data - LZX_OFFSET_OFFSET,
- &next_chosen_item);
- c->queue.R[2] = c->queue.R[1];
- c->queue.R[1] = c->queue.R[0];
- c->queue.R[0] = prev_offset_data - LZX_OFFSET_OFFSET;
- }
- lz_mf_skip_positions(mf, skip_len);
- window_ptr += skip_len;
- prev_len = 0;
- }
-
- return next_chosen_item - c->chosen_items;
-}
-
-/* Given the frequencies of symbols in an LZX-compressed block and the
- * corresponding Huffman codes, return LZX_BLOCKTYPE_ALIGNED or
- * LZX_BLOCKTYPE_VERBATIM if an aligned offset or verbatim block, respectively,
- * will take fewer bits to output. */
-static int
-lzx_choose_verbatim_or_aligned(const struct lzx_freqs * freqs,
- const struct lzx_codes * codes)
-{
- u32 aligned_cost = 0;
- u32 verbatim_cost = 0;
-
- /* A verbatim block requires 3 bits in each place that an aligned symbol
- * would be used in an aligned offset block. */
- for (unsigned i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
- verbatim_cost += 3 * freqs->aligned[i];
- aligned_cost += codes->lens.aligned[i] * freqs->aligned[i];
- }
-
- /* Account for output of the aligned offset code. */
- aligned_cost += LZX_ALIGNEDCODE_ELEMENT_SIZE * LZX_ALIGNEDCODE_NUM_SYMBOLS;
-
- if (aligned_cost < verbatim_cost)
- return LZX_BLOCKTYPE_ALIGNED;
- else
- return LZX_BLOCKTYPE_VERBATIM;
-}
-
-/* Near-optimal parsing */
-static u32
-lzx_choose_near_optimal_items_for_block(struct lzx_compressor *c,
- u32 block_start_pos, u32 block_size)
-{
- u32 num_passes_remaining = c->params.num_optim_passes;
- struct lzx_lru_queue orig_queue;
- struct lzx_item *next_chosen_item;
- struct lzx_item **next_chosen_item_ptr;
-
- /* Choose appropriate match-finder wrapper functions. */
- if (num_passes_remaining > 1) {
- if (block_size == c->cur_window_size)
- c->get_matches_func = lzx_get_matches_fillcache_singleblock;
- else
- c->get_matches_func = lzx_get_matches_fillcache_multiblock;
- c->skip_bytes_func = lzx_skip_bytes_fillcache;
- } else {
- if (block_size == c->cur_window_size)
- c->get_matches_func = lzx_get_matches_nocache_singleblock;
- else
- c->get_matches_func = lzx_get_matches_nocache_multiblock;
- c->skip_bytes_func = lzx_skip_bytes_nocache;
- }
-
- /* No matches will extend beyond the end of the block. */
- c->match_window_end = block_start_pos + block_size;
-
- /* The first optimization pass will use a default cost model. Each
- * additional optimization pass will use a cost model computed from the
- * previous pass.
- *
- * To improve performance we only generate the array containing the
- * matches and literals in intermediate form on the final pass. For
- * earlier passes, tallying symbol frequencies is sufficient. */
- lzx_set_default_costs(&c->costs, c->num_main_syms);
-
- next_chosen_item_ptr = NULL;
- orig_queue = c->queue;
- do {
- /* Reset the match-finder wrapper. */
- c->match_window_pos = block_start_pos;
- c->cache_ptr = c->cached_matches;
-
- if (num_passes_remaining == 1) {
- /* Last pass: actually generate the items. */
- next_chosen_item = c->chosen_items;
- next_chosen_item_ptr = &next_chosen_item;
- }
-
- /* Choose the items. */
- lzx_optim_pass(c, next_chosen_item_ptr);
-
- if (num_passes_remaining > 1) {
- /* This isn't the last pass. */
-
- /* Make the Huffman codes from the symbol frequencies. */
- lzx_make_huffman_codes(&c->freqs, &c->codes[c->codes_index],
- c->num_main_syms);
-
- /* Update symbol costs. */
- lzx_set_costs(c, &c->codes[c->codes_index].lens);
-
- /* Reset symbol frequencies. */
- memset(&c->freqs, 0, sizeof(c->freqs));
-
- /* Reset the match offset LRU queue to what it was at
- * the beginning of the block. */
- c->queue = orig_queue;
-
- /* Choose appopriate match-finder wrapper functions. */
- if (c->cache_ptr <= c->cache_limit) {
- c->get_matches_func = lzx_get_matches_usecache_nocheck;
- c->skip_bytes_func = lzx_skip_bytes_usecache_nocheck;
- } else {
- c->get_matches_func = lzx_get_matches_usecache;
- c->skip_bytes_func = lzx_skip_bytes_usecache;
- }
- }
- } while (--num_passes_remaining);
-
- /* Return the number of items chosen. */
- return next_chosen_item - c->chosen_items;
-}
-
-/*
- * Choose the matches/literals with which to output the block of data beginning
- * at '&c->cur_window[block_start_pos]' and extending for 'block_size' bytes.
- *
- * The frequences of the Huffman symbols in the block will be tallied in
- * 'c->freqs'.
- *
- * 'c->queue' must specify the state of the queue at the beginning of this block.
- * This function will update it to the state of the queue at the end of this
- * block.
- *
- * Returns the number of matches/literals that were chosen and written to
- * 'c->chosen_items' in the 'struct lzx_item' intermediate representation.
- */
-static u32
-lzx_choose_items_for_block(struct lzx_compressor *c,
- u32 block_start_pos, u32 block_size)
-{
- return (*c->params.choose_items_for_block)(c, block_start_pos, block_size);
-}
-
-/* Initialize c->offset_slot_fast. */
-static void
-lzx_init_offset_slot_fast(struct lzx_compressor *c)
-{
- u8 slot = 0;
-
- for (u32 offset = 0; offset < LZX_NUM_FAST_OFFSETS; offset++) {
-
- while (offset + LZX_OFFSET_OFFSET >= lzx_offset_slot_base[slot + 1])
- slot++;
-
- c->offset_slot_fast[offset] = slot;
- }
-}
-
-/* Set internal compression parameters for the specified compression level and
- * maximum window size. */
-static void
-lzx_build_params(unsigned int compression_level, u32 max_window_size,
- struct lzx_compressor_params *lzx_params)
-{
- if (compression_level < 25) {
-
- /* Fast compression: Use lazy parsing. */
-
- lzx_params->choose_items_for_block = lzx_choose_lazy_items_for_block;
- lzx_params->num_optim_passes = 1;
-
- /* When lazy parsing, the hash chain match-finding algorithm is
- * fastest unless the window is too large.
- *
- * TODO: something like hash arrays would actually be better
- * than binary trees on large windows. */
- if (max_window_size <= 262144)
- lzx_params->mf_algo = LZ_MF_HASH_CHAINS;
- else
- lzx_params->mf_algo = LZ_MF_BINARY_TREES;
-
- /* When lazy parsing, don't bother with length 2 matches. */
- lzx_params->min_match_length = 3;
-
- /* Scale nice_match_length and max_search_depth with the
- * compression level. */
- lzx_params->nice_match_length = 25 + compression_level * 2;
- lzx_params->max_search_depth = 25 + compression_level;
- } else {
-
- /* Normal / high compression: Use near-optimal parsing. */
-
- lzx_params->choose_items_for_block = lzx_choose_near_optimal_items_for_block;
-
- /* Set a number of optimization passes appropriate for the
- * compression level. */
-
- lzx_params->num_optim_passes = 1;
-
- if (compression_level >= 40)
- lzx_params->num_optim_passes++;
-
- /* Use more optimization passes for higher compression levels.
- * But the more passes there are, the less they help --- so
- * don't add them linearly. */
- if (compression_level >= 70) {
- lzx_params->num_optim_passes++;
- if (compression_level >= 100)
- lzx_params->num_optim_passes++;
- if (compression_level >= 150)
- lzx_params->num_optim_passes++;
- if (compression_level >= 200)
- lzx_params->num_optim_passes++;
- if (compression_level >= 300)
- lzx_params->num_optim_passes++;
- }
-
- /* When doing near-optimal parsing, the hash chain match-finding
- * algorithm is good if the window size is small and we're only
- * doing one optimization pass. Otherwise, the binary tree
- * algorithm is the way to go. */
- if (max_window_size <= 32768 && lzx_params->num_optim_passes == 1)
- lzx_params->mf_algo = LZ_MF_HASH_CHAINS;
- else
- lzx_params->mf_algo = LZ_MF_BINARY_TREES;
-
- /* When doing near-optimal parsing, allow length 2 matches if
- * the compression level is sufficiently high. */
- if (compression_level >= 45)
- lzx_params->min_match_length = 2;
- else
- lzx_params->min_match_length = 3;
-
- /* Scale nice_match_length and max_search_depth with the
- * compression level. */
- lzx_params->nice_match_length = min(((u64)compression_level * 32) / 50,
- LZX_MAX_MATCH_LEN);
- lzx_params->max_search_depth = min(((u64)compression_level * 50) / 50,
- LZX_MAX_MATCH_LEN);
- }
-}
-
-/* Given the internal compression parameters and maximum window size, build the
- * Lempel-Ziv match-finder parameters. */
-static void
-lzx_build_mf_params(const struct lzx_compressor_params *lzx_params,
- u32 max_window_size, struct lz_mf_params *mf_params)
-{
- memset(mf_params, 0, sizeof(*mf_params));
-
- mf_params->algorithm = lzx_params->mf_algo;
- mf_params->max_window_size = max_window_size;
- mf_params->min_match_len = lzx_params->min_match_length;
- mf_params->max_match_len = LZX_MAX_MATCH_LEN;
- mf_params->max_search_depth = lzx_params->max_search_depth;
- mf_params->nice_match_len = lzx_params->nice_match_length;
-}
-
-static void
-lzx_free_compressor(void *_c);
-
-static u64
-lzx_get_needed_memory(size_t max_block_size, unsigned int compression_level)
-{
- struct lzx_compressor_params params;
- u64 size = 0;
- unsigned window_order;
- u32 max_window_size;
-
- window_order = lzx_get_window_order(max_block_size);
- if (window_order == 0)
- return 0;
- max_window_size = max_block_size;
-
- lzx_build_params(compression_level, max_window_size, ¶ms);
-
- size += sizeof(struct lzx_compressor);
-
- /* cur_window */
- size += max_window_size;
-
- /* mf */
- size += lz_mf_get_needed_memory(params.mf_algo, max_window_size);
-
- /* cached_matches */
- if (params.num_optim_passes > 1)
- size += LZX_CACHE_LEN * sizeof(struct lz_match);
- else
- size += LZX_MAX_MATCHES_PER_POS * sizeof(struct lz_match);
- return size;
-}
-
-static int
-lzx_create_compressor(size_t max_block_size, unsigned int compression_level,
- void **c_ret)
-{
- struct lzx_compressor *c;
- struct lzx_compressor_params params;
- struct lz_mf_params mf_params;
- unsigned window_order;
- u32 max_window_size;
-
- window_order = lzx_get_window_order(max_block_size);
- if (window_order == 0)
- return WIMLIB_ERR_INVALID_PARAM;
- max_window_size = max_block_size;
-
- lzx_build_params(compression_level, max_window_size, ¶ms);
- lzx_build_mf_params(¶ms, max_window_size, &mf_params);
- if (!lz_mf_params_valid(&mf_params))
- return WIMLIB_ERR_INVALID_PARAM;
-
- c = CALLOC(1, sizeof(struct lzx_compressor));
- if (!c)
- goto oom;
-
- c->params = params;
- c->num_main_syms = lzx_get_num_main_syms(window_order);
- c->window_order = window_order;
-
- /* The window is allocated as 16-byte aligned to speed up memcpy() and
- * enable lzx_e8_filter() optimization on x86_64. */
- c->cur_window = ALIGNED_MALLOC(max_window_size, 16);
- if (!c->cur_window)
- goto oom;
-
- c->mf = lz_mf_alloc(&mf_params);
- if (!c->mf)
- goto oom;
-
- if (params.num_optim_passes > 1) {
- c->cached_matches = MALLOC(LZX_CACHE_LEN *
- sizeof(struct lz_match));
- if (!c->cached_matches)
- goto oom;
- c->cache_limit = c->cached_matches + LZX_CACHE_LEN -
- (LZX_MAX_MATCHES_PER_POS + 1);
- } else {
- c->cached_matches = MALLOC(LZX_MAX_MATCHES_PER_POS *
- sizeof(struct lz_match));
- if (!c->cached_matches)
- goto oom;
- }
-
- lzx_init_offset_slot_fast(c);
-
- *c_ret = c;
- return 0;
-
-oom:
- lzx_free_compressor(c);
- return WIMLIB_ERR_NOMEM;
-}
-
-static size_t
-lzx_compress(const void *uncompressed_data, size_t uncompressed_size,
- void *compressed_data, size_t compressed_size_avail, void *_c)
-{
- struct lzx_compressor *c = _c;
- struct lzx_output_bitstream os;
- u32 num_chosen_items;
- const struct lzx_lens *prev_lens;
- u32 block_start_pos;
- u32 block_size;
- int block_type;
-
- /* Don't bother compressing very small inputs. */
- if (uncompressed_size < 100)
- return 0;
-
- /* The input data must be preprocessed. To avoid changing the original
- * input data, copy it to a temporary buffer. */
- memcpy(c->cur_window, uncompressed_data, uncompressed_size);
- c->cur_window_size = uncompressed_size;
-
- /* Preprocess the data. */
- lzx_do_e8_preprocessing(c->cur_window, c->cur_window_size);
-
- /* Load the window into the match-finder. */
- lz_mf_load_window(c->mf, c->cur_window, c->cur_window_size);
-
- /* Initialize the match offset LRU queue. */
- lzx_lru_queue_init(&c->queue);
-
- /* Initialize the output bitstream. */
- lzx_init_output(&os, compressed_data, compressed_size_avail);
-
- /* Compress the data block by block.
- *
- * TODO: The compression ratio could be slightly improved by performing
- * data-dependent block splitting instead of using fixed-size blocks.
- * Doing so well is a computationally hard problem, however. */
- block_start_pos = 0;
- c->codes_index = 0;
- prev_lens = &c->zero_lens;
- do {
- /* Compute the block size. */
- block_size = min(LZX_DIV_BLOCK_SIZE,
- uncompressed_size - block_start_pos);
-
- /* Reset symbol frequencies. */
- memset(&c->freqs, 0, sizeof(c->freqs));
-
- /* Prepare the matches/literals for the block. */
- num_chosen_items = lzx_choose_items_for_block(c,
- block_start_pos,
- block_size);
-
- /* Make the Huffman codes from the symbol frequencies. */
- lzx_make_huffman_codes(&c->freqs, &c->codes[c->codes_index],
- c->num_main_syms);
-
- /* Choose the best block type.
- *
- * Note: we currently don't consider uncompressed blocks. */
- block_type = lzx_choose_verbatim_or_aligned(&c->freqs,
- &c->codes[c->codes_index]);
-
- /* Write the compressed block to the output buffer. */
- lzx_write_compressed_block(block_type,
- block_size,
- c->window_order,
- c->num_main_syms,
- c->chosen_items,
- num_chosen_items,
- &c->codes[c->codes_index],
- prev_lens,
- &os);
-
- /* The current codeword lengths become the previous lengths. */
- prev_lens = &c->codes[c->codes_index].lens;
- c->codes_index ^= 1;
-
- block_start_pos += block_size;
-
- } while (block_start_pos != uncompressed_size);
-
- return lzx_flush_output(&os);
-}
-
-static void
-lzx_free_compressor(void *_c)
-{
- struct lzx_compressor *c = _c;
-
- if (c) {
- ALIGNED_FREE(c->cur_window);
- lz_mf_free(c->mf);
- FREE(c->cached_matches);
- FREE(c);
- }
-}
-
-const struct compressor_ops lzx_compressor_ops = {
- .get_needed_memory = lzx_get_needed_memory,
- .create_compressor = lzx_create_compressor,
- .compress = lzx_compress,
- .free_compressor = lzx_free_compressor,
-};
git://wimlib.net / wimlib / blobdiff