/*
* lzx-compress.c
*
- * LZX compression routines, originally based on code written by Matthew T.
- * Russotto (liblzxcomp), but heavily modified.
+ * A compressor that produces output compatible with the LZX compression format.
*/
/*
- * Copyright (C) 2002 Matthew T. Russotto
- * Copyright (C) 2012, 2013 Eric Biggers
+ * Copyright (C) 2012, 2013, 2014 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 ("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.
*/
-#include "lzx.h"
-#include "compress.h"
-#include <stdlib.h>
+#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;
-/* Structure to contain the Huffman codes for the main, length, and aligned
- * offset trees. */
+/* 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 {
- u16 main_codewords[LZX_MAINTREE_NUM_SYMBOLS];
- u8 main_lens[LZX_MAINTREE_NUM_SYMBOLS];
+ 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];
+};
- u16 len_codewords[LZX_LENTREE_NUM_SYMBOLS];
- u8 len_lens[LZX_LENTREE_NUM_SYMBOLS];
+/* Intermediate LZX match/literal format */
+struct lzx_item {
- u16 aligned_codewords[LZX_ALIGNEDTREE_NUM_SYMBOLS];
- u8 aligned_lens[LZX_ALIGNEDTREE_NUM_SYMBOLS];
+ /* 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;
};
-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];
+/* 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;
};
-/* Returns the LZX position slot that corresponds to a given formatted offset.
- *
- * Logically, this returns the smallest i such that
- * formatted_offset >= lzx_position_base[i].
+/*
+ * Match chooser position data:
*
- * The actual implementation below takes advantage of the regularity of the
- * numbers in the lzx_position_base array to calculate the slot directly from
- * the formatted offset without actually looking at the array.
+ * 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.
*/
-static inline unsigned
-lzx_get_position_slot(unsigned formatted_offset)
-{
-#if 0
- /*
- * Slots 36-49 (formatted_offset >= 262144) can be found by
- * (formatted_offset/131072) + 34 == (formatted_offset >> 17) + 34;
- * however, this check for formatted_offset >= 262144 is commented out
- * because WIM chunks cannot be that large.
+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.
*/
- if (formatted_offset >= 262144) {
- return (formatted_offset >> 17) + 34;
- } else
-#endif
- {
- /* Note: this part here only works if:
- *
- * 2 <= formatted_offset < 655360
- *
- * It is < 655360 because the frequency of the position bases
- * increases starting at the 655360 entry, and it is >= 2
- * because the below calculation fails if the most significant
- * bit is lower than the 2's place. */
- wimlib_assert(formatted_offset >= 2 && formatted_offset < 655360);
- unsigned mssb_idx = bsr32(formatted_offset);
- return (mssb_idx << 1) |
- ((formatted_offset >> (mssb_idx - 1)) & 1);
+ 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)
+ *os->next++ = cpu_to_le16(os->bitbuf >> os->bitcount);
+
+ /* 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)
+ *os->next++ = cpu_to_le16(os->bitbuf);
+ os->bitcount = 0;
+ }
}
}
-static u32
-lzx_record_literal(u8 literal, void *__main_freq_tab)
+/* 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)
{
- freq_t *main_freq_tab = __main_freq_tab;
- main_freq_tab[literal]++;
- return literal;
+ lzx_write_varbits(os, bits, num_bits, num_bits);
}
-/* 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. */
+/*
+ * 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_record_match(unsigned match_offset, unsigned match_len,
- void *__freq_tabs, void *__queue)
-{
- struct lzx_freq_tables *freq_tabs = __freq_tabs;
- struct lru_queue *queue = __queue;
- unsigned position_slot;
- unsigned position_footer = 0;
- u32 match;
- u32 len_header;
- u32 len_pos_header;
- unsigned len_footer;
- unsigned adjusted_match_len;
-
- 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;
+lzx_flush_output(struct lzx_output_bitstream *os)
+{
+ if (os->next == os->end)
+ return 0;
+
+ if (os->bitcount != 0)
+ *os->next++ = cpu_to_le16(os->bitbuf << (16 - os->bitcount));
+
+ 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 {
- /* 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);
+ /* 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);
}
+}
- adjusted_match_len = match_len - LZX_MIN_MATCH;
+/*
+ * 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);
- /* 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).
+ 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.
*
- * 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.
+ * 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.
*
- * 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;
+ * 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 {
- len_header = LZX_NUM_PRIMARY_LENS;
- len_footer = adjusted_match_len - LZX_NUM_PRIMARY_LENS;
- freq_tabs->len_freq_table[len_footer]++;
+ 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);
+ }
}
- len_pos_header = (position_slot << 3) | len_header;
- wimlib_assert(len_pos_header < LZX_MAINTREE_NUM_SYMBOLS - LZX_NUM_CHARS);
+ /* 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;
- freq_tabs->main_freq_table[len_pos_header + LZX_NUM_CHARS]++;
+ matches = c->cache_ptr;
+ num_matches = lz_mf_get_matches(c->mf, matches);
+ c->match_window_pos++;
+ *matches_ret = matches;
+ return num_matches;
+}
- /* Equivalent to:
- * if (lzx_extra_bits[position_slot] >= 3) */
- if (position_slot >= 8)
- freq_tabs->aligned_freq_table[position_footer & 7]++;
+static unsigned
+lzx_get_matches_nocache_multiblock(struct lzx_compressor *c,
+ const struct lz_match **matches_ret)
+{
+ struct lz_match *matches;
+ unsigned num_matches;
- return match;
+ 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;
}
/*
- * Writes a compressed literal match to the output.
+ * Find matches at the next position in the window.
+ *
+ * This uses a wrapper function around the underlying match-finder.
*
- * @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.
+ * 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 int
-lzx_write_match(struct output_bitstream *out, int block_type,
- u32 match, const struct lzx_codes *codes)
-{
- /* low 8 bits are the match length minus 2 */
- unsigned match_len_minus_2 = match & 0xff;
- /* Next 17 bits are the position footer */
- unsigned position_footer = (match >> 8) & 0x1ffff; /* 17 bits */
- /* Next 6 bits are the position slot. */
- unsigned position_slot = (match >> 25) & 0x3f; /* 6 bits */
+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 len_footer;
- unsigned len_pos_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;
- 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
- * the match length minus MIN_MATCH, and there is no
- * length footer.
- *
- * Otherwise, the length header contains
- * NUM_PRIMARY_LENS, and the length footer contains
- * the match length minus NUM_PRIMARY_LENS minus
- * MIN_MATCH. */
- if (match_len_minus_2 < LZX_NUM_PRIMARY_LENS) {
- len_header = match_len_minus_2;
- /* No length footer-- mark it with a special
- * value. */
- len_footer = (unsigned)(-1);
+ 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_footer = match_len_minus_2 - LZX_NUM_PRIMARY_LENS;
+ len_symbol = len - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS;
+ c->freqs.len[len_symbol]++;
}
- /* Combine the position slot with the length header into
- * a single symbol that will be encoded with the main
- * tree. */
- len_pos_header = (position_slot << 3) | len_header;
-
- /* The actual main symbol is offset by LZX_NUM_CHARS because
- * values under LZX_NUM_CHARS are used to indicate a literal
- * byte rather than a match. */
- main_symbol = len_pos_header + LZX_NUM_CHARS;
-
- /* Output main symbol. */
- ret = bitstream_put_bits(out, codes->main_codewords[main_symbol],
- codes->main_lens[main_symbol]);
- if (ret != 0)
- return ret;
-
- /* 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;
+ 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;
- wimlib_assert(position_slot < LZX_NUM_POSITION_SLOTS);
+ /* Main code */
+ for (i = 0; i < c->num_main_syms; i++)
+ c->costs.main[i] = lens->main[i] ? lens->main[i] : 15;
- num_extra_bits = lzx_get_num_extra_bits(position_slot);
+ /* Length code */
+ for (i = 0; i < LZX_LENCODE_NUM_SYMBOLS; i++)
+ c->costs.len[i] = lens->len[i] ? lens->len[i] : 15;
- /* For aligned offset blocks with at least 3 extra bits, output the
- * verbatim bits literally, then the aligned bits encoded using the
- * aligned offset tree. Otherwise, only the verbatim bits need to be
- * output. */
- if ((block_type == LZX_BLOCKTYPE_ALIGNED) && (num_extra_bits >= 3)) {
+ /* 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;
- verbatim_bits = position_footer >> 3;
- ret = bitstream_put_bits(out, verbatim_bits,
- num_extra_bits - 3);
- if (ret != 0)
- return ret;
+ /* Main code (part 2): Match header symbols */
+ for (; i < num_main_syms; i++)
+ costs->main[i] = 10;
- 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;
+ /* 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 {
- /* 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;
+ len_header = LZX_NUM_PRIMARY_LENS;
+
+ /* Account for length symbol. */
+ cost = costs->len[len - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS];
}
- return 0;
+
+ /* 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))];
}
/*
- * 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.
+ * 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 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 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;
- 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;
+ 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 {
- /* 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;
+ position_cost += num_extra_bits;
}
- }
- return 0;
+ 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
}
/*
- * 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.
+ * Search for repeat offset matches with the current position.
*/
-static int
-lzx_write_compressed_tree(struct output_bitstream *out,
- const u8 lens[], unsigned num_symbols)
-{
- /* Frequencies of the length symbols, including the RLE symbols (NOT the
- * actual lengths themselves). */
- freq_t pretree_freqs[LZX_PRETREE_NUM_SYMBOLS];
- u8 pretree_lens[LZX_PRETREE_NUM_SYMBOLS];
- u16 pretree_codewords[LZX_PRETREE_NUM_SYMBOLS];
- u8 output_syms[num_symbols * 2];
- unsigned output_syms_idx;
- unsigned cur_run_len;
- unsigned i;
- unsigned len_in_run;
- unsigned additional_bits;
- char delta;
- u8 pretree_sym;
-
- ZERO_ARRAY(pretree_freqs);
-
- /* Since the code word lengths use a form of RLE encoding, the goal here
- * is to find each run of identical lengths when going through them in
- * symbol order (including runs of length 1). For each run, as many
- * lengths are encoded using RLE as possible, and the rest are output
- * literally.
- *
- * output_syms[] will be filled in with the length symbols that will be
- * output, including RLE codes, not yet encoded using the pre-tree.
+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.
*
- * cur_run_len keeps track of how many code word lengths are in the
- * current run of identical lengths.
- */
- output_syms_idx = 0;
- cur_run_len = 1;
- for (i = 1; i <= num_symbols; i++) {
+ * *begin_queue is the current state of the match offset LRU queue. */
- if (i != num_symbols && lens[i] == lens[i - 1]) {
- /* Still in a run--- keep going. */
- cur_run_len++;
- continue;
+ 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;
+ }
}
- /* Run ended! Check if it is a run of zeroes or a run of
- * nonzeroes. */
+ /* Consider coding a literal.
- /* The symbol that was repeated in the run--- not to be confused
- * with the length *of* the run (cur_run_len) */
- len_in_run = lens[i - 1];
+ * 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);
- if (len_in_run == 0) {
- /* A run of 0's. Encode it in as few length
- * codes as we can. */
+ /* Advance to the next position. */
+ cur_optimum_ptr++;
- /* The magic length 18 indicates a run of 20 + n zeroes,
- * where n is an uncompressed literal 5-bit integer that
- * follows the magic length. */
- while (cur_run_len >= 20) {
+ /* The lowest-cost path to the current position is now known.
+ * Finalize the recent offsets queue that results from taking
+ * this lowest-cost path. */
- additional_bits = min(cur_run_len - 20, 0x1f);
- pretree_freqs[18]++;
- output_syms[output_syms_idx++] = 18;
- output_syms[output_syms_idx++] = additional_bits;
- cur_run_len -= 20 + additional_bits;
+ 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;
+}
- /* The magic length 17 indicates a run of 4 + n zeroes,
- * where n is an uncompressed literal 4-bit integer that
- * follows the magic length. */
- while (cur_run_len >= 4) {
- additional_bits = min(cur_run_len - 4, 0xf);
- pretree_freqs[17]++;
- output_syms[output_syms_idx++] = 17;
- output_syms[output_syms_idx++] = additional_bits;
- cur_run_len -= 4 + additional_bits;
+/* 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;
+ }
- /* A run of nonzero lengths. */
+ 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;
+ }
- /* The magic length 19 indicates a run of 4 + n
- * nonzeroes, where n is a literal bit that follows the
- * magic length, and where the value of the lengths in
- * the run is given by an extra length symbol, encoded
- * with the pretree, that follows the literal bit.
+ if (prev_len == 0 || cur_score > prev_score) {
+ /* No previous match, or the current match is better
+ * than the previous match.
*
- * The extra length symbol is encoded as a difference
- * from the length of the codeword for the first symbol
- * in the run in the previous tree.
- * */
- while (cur_run_len >= 4) {
- additional_bits = (cur_run_len > 4);
- delta = -(char)len_in_run;
- if (delta < 0)
- delta += 17;
- pretree_freqs[19]++;
- pretree_freqs[(unsigned char)delta]++;
- output_syms[output_syms_idx++] = 19;
- output_syms[output_syms_idx++] = additional_bits;
- output_syms[output_syms_idx++] = delta;
- cur_run_len -= 4 + additional_bits;
+ * 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;
}
- /* 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;
- if (delta < 0)
- delta += 17;
+ /* Current match is not better than the previous match, so
+ * output the previous match. */
+
+ skip_len = prev_len - 2;
- pretree_freqs[(unsigned char)delta]++;
- output_syms[output_syms_idx++] = delta;
+ 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;
+ }
- cur_run_len = 1;
+ 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];
}
- wimlib_assert(output_syms_idx < ARRAY_LEN(output_syms));
+ /* Account for output of the aligned offset code. */
+ aligned_cost += LZX_ALIGNEDCODE_ELEMENT_SIZE * LZX_ALIGNEDCODE_NUM_SYMBOLS;
- /* Build the pretree from the frequencies of the length symbols. */
+ if (aligned_cost < verbatim_cost)
+ return LZX_BLOCKTYPE_ALIGNED;
+ else
+ return LZX_BLOCKTYPE_VERBATIM;
+}
- make_canonical_huffman_code(LZX_PRETREE_NUM_SYMBOLS,
- LZX_MAX_CODEWORD_LEN,
- pretree_freqs, pretree_lens,
- pretree_codewords);
+/* 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;
+ }
- /* Write the lengths of the pretree codes to the output. */
- for (i = 0; i < LZX_PRETREE_NUM_SYMBOLS; i++)
- bitstream_put_bits(out, pretree_lens[i],
- LZX_PRETREE_ELEMENT_SIZE);
+ /* No matches will extend beyond the end of the block. */
+ c->match_window_end = block_start_pos + block_size;
- /* Write the length symbols, encoded with the pretree, to the output. */
+ /* 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;
+ }
- i = 0;
- while (i < output_syms_idx) {
- pretree_sym = output_syms[i++];
-
- bitstream_put_bits(out, pretree_codewords[pretree_sym],
- pretree_lens[pretree_sym]);
- switch (pretree_sym) {
- case 17:
- bitstream_put_bits(out, output_syms[i++], 4);
- break;
- case 18:
- bitstream_put_bits(out, output_syms[i++], 5);
- break;
- case 19:
- bitstream_put_bits(out, output_syms[i++], 1);
- bitstream_put_bits(out,
- pretree_codewords[output_syms[i]],
- pretree_lens[output_syms[i]]);
- i++;
- break;
- default:
- break;
+ /* 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;
+ }
}
- }
- return 0;
+ } 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);
}
-/* 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)
+/* Initialize c->offset_slot_fast. */
+static void
+lzx_init_offset_slot_fast(struct lzx_compressor *c)
{
- make_canonical_huffman_code(LZX_MAINTREE_NUM_SYMBOLS,
- LZX_MAX_CODEWORD_LEN,
- freq_tabs->main_freq_table,
- codes->main_lens,
- codes->main_codewords);
+ u8 slot = 0;
+
+ for (u32 offset = 0; offset < LZX_NUM_FAST_OFFSETS; offset++) {
- make_canonical_huffman_code(LZX_LENTREE_NUM_SYMBOLS,
- LZX_MAX_CODEWORD_LEN,
- freq_tabs->len_freq_table,
- codes->len_lens,
- codes->len_codewords);
+ while (offset + LZX_OFFSET_OFFSET >= lzx_offset_slot_base[slot + 1])
+ slot++;
- make_canonical_huffman_code(LZX_ALIGNEDTREE_NUM_SYMBOLS, 8,
- freq_tabs->aligned_freq_table,
- codes->aligned_lens,
- codes->aligned_codewords);
+ c->offset_slot_fast[offset] = slot;
+ }
}
+/* Set internal compression parameters for the specified compression level and
+ * maximum window size. */
static void
-do_call_insn_translation(u32 *call_insn_target, int input_pos,
- int32_t file_size)
+lzx_build_params(unsigned int compression_level, u32 max_window_size,
+ struct lzx_compressor_params *lzx_params)
{
- int32_t abs_offset;
- int32_t rel_offset;
+ if (compression_level < 25) {
- 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;
+ /* 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++;
}
- *call_insn_target = cpu_to_le32(abs_offset);
+
+ /* 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);
}
}
-/* This is the reverse of undo_call_insn_preprocessing() in lzx-decompress.c.
- * See the comment above that function for more information. */
+/* Given the internal compression parameters and maximum window size, build the
+ * Lempel-Ziv match-finder parameters. */
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;
- }
- }
+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 const struct lz_params lzx_lz_params = {
+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;
- /* LZX_MIN_MATCH == 2, but 2-character matches are rarely useful; the
- * minimum match for compression is set to 3 instead. */
- .min_match = 3,
+ window_order = lzx_get_window_order(max_block_size);
+ if (window_order == 0)
+ return 0;
+ max_window_size = max_block_size;
- .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,
-};
+ lzx_build_params(compression_level, max_window_size, ¶ms);
-/*
- * Performs LZX compression on a block of data.
- *
- * @__uncompressed_data: Pointer to the data to be compressed.
- * @uncompressed_len: Length, in bytes, of the data to be compressed.
- * @compressed_data: Pointer to a location at least (@uncompressed_len - 1)
- * bytes long into which the compressed data may be
- * written.
- * @compressed_len_ret: A pointer to an unsigned int into which the length of
- * the compressed data may be returned.
- *
- * Returns zero if compression was successfully performed. In that case
- * @compressed_data and @compressed_len_ret will contain the compressed data and
- * its length. A return value of nonzero means that compressing the data did
- * not reduce its size, and @compressed_data will not contain the full
- * compressed data.
- */
-int
-lzx_compress(const void *__uncompressed_data, unsigned uncompressed_len,
- void *compressed_data, unsigned *compressed_len_ret)
-{
- struct output_bitstream ostream;
- u8 uncompressed_data[uncompressed_len + 8];
- struct lzx_freq_tables freq_tabs;
- struct lzx_codes codes;
- u32 match_tab[uncompressed_len];
- struct lru_queue queue;
- unsigned num_matches;
- unsigned compressed_len;
- unsigned i;
- int ret;
- int block_type = LZX_BLOCKTYPE_ALIGNED;
+ size += sizeof(struct lzx_compressor);
- if (uncompressed_len < 100)
- return 1;
+ /* cur_window */
+ size += max_window_size;
- memset(&freq_tabs, 0, sizeof(freq_tabs));
- queue.R0 = 1;
- queue.R1 = 1;
- queue.R2 = 1;
+ /* mf */
+ size += lz_mf_get_needed_memory(params.mf_algo, max_window_size);
- /* 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);
+ /* 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;
+}
- /* Before doing any actual compression, do the call instruction (0xe8
- * byte) translation on the uncompressed data. */
- do_call_insn_preprocessing(uncompressed_data, uncompressed_len);
+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;
+ }
- /* 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_init_offset_slot_fast(c);
- num_matches = lz_analyze_block(uncompressed_data, uncompressed_len,
- match_tab, lzx_record_match,
- lzx_record_literal, &freq_tabs,
- &queue, freq_tabs.main_freq_table,
- &lzx_lz_params);
+ *c_ret = c;
+ return 0;
- lzx_make_huffman_codes(&freq_tabs, &codes);
+oom:
+ lzx_free_compressor(c);
+ return WIMLIB_ERR_NOMEM;
+}
- /* Initialize the output bitstream. */
- init_output_bitstream(&ostream, compressed_data, uncompressed_len - 1);
+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;
- /* 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);
+ /* Don't bother compressing very small inputs. */
+ if (uncompressed_size < 100)
+ return 0;
- /* 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);
- }
+ /* 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;
- /* Write out the aligned offset tree. Note that M$ lies and says that
- * the aligned offset tree comes after the length tree, but that is
- * wrong; it actually is before the main tree. */
- if (block_type == LZX_BLOCKTYPE_ALIGNED)
- for (i = 0; i < LZX_ALIGNEDTREE_NUM_SYMBOLS; i++)
- bitstream_put_bits(&ostream, codes.aligned_lens[i],
- LZX_ALIGNEDTREE_ELEMENT_SIZE);
-
- /* Write the pre-tree and lengths for the first LZX_NUM_CHARS symbols in the
- * main tree. */
- ret = lzx_write_compressed_tree(&ostream, codes.main_lens,
- LZX_NUM_CHARS);
- if (ret != 0)
- return ret;
-
- /* Write the pre-tree and symbols for the rest of the main tree. */
- ret = lzx_write_compressed_tree(&ostream, codes.main_lens +
- LZX_NUM_CHARS,
- LZX_MAINTREE_NUM_SYMBOLS -
- LZX_NUM_CHARS);
- if (ret != 0)
- return ret;
-
- /* Write the pre-tree and symbols for the length tree. */
- ret = lzx_write_compressed_tree(&ostream, codes.len_lens,
- LZX_LENTREE_NUM_SYMBOLS);
- if (ret != 0)
- return ret;
-
- /* Write the compressed literals. */
- ret = lzx_write_compressed_literals(&ostream, block_type,
- match_tab, num_matches, &codes);
- if (ret != 0)
- return ret;
-
- ret = flush_output_bitstream(&ostream);
- if (ret != 0)
- return ret;
-
- compressed_len = ostream.bit_output - (u8*)compressed_data;
-
- *compressed_len_ret = compressed_len;
-
-#ifdef ENABLE_VERIFY_COMPRESSION
- /* Verify that we really get the same thing back when decompressing. */
- u8 buf[uncompressed_len];
- ret = lzx_decompress(compressed_data, compressed_len, buf,
- uncompressed_len);
- if (ret != 0) {
- ERROR("lzx_compress(): Failed to decompress data we compressed");
- abort();
- }
+ /* Preprocess the data. */
+ lzx_do_e8_preprocessing(c->cur_window, c->cur_window_size);
- 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();
- }
+ /* 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);
}
-#endif
- return 0;
}
+
+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