X-Git-Url: https://wimlib.net/git/?p=wimlib;a=blobdiff_plain;f=src%2Flzx-compress.c;h=a972cc35bf3c24722372db9538c3b9a72f21f1c8;hp=c876a182dd677be651cffd09b5d96937e283a59e;hb=7953f731d41d728a8881872bcf82fd8f9d1f7ee8;hpb=61db93f82eca3fe9f7676355c709c58cc425a6ad diff --git a/src/lzx-compress.c b/src/lzx-compress.c index c876a182..a972cc35 100644 --- a/src/lzx-compress.c +++ b/src/lzx-compress.c @@ -1,13 +1,11 @@ /* * 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. * @@ -27,751 +25,2310 @@ /* - * This file provides wimlib_lzx_compress(), a function to compress an in-memory - * buffer of data using LZX compression, as used in the WIM file format. - * - * Please see the comments in lzx-decompress.c for more information about this - * compression format. - * - * One thing to keep in mind is that there is no sliding window, since the - * window is always the entirety of a WIM chunk, which is at most WIM_CHUNK_SIZE - * ( = 32768) bytes. - * - * The basic compression algorithm used here should be familiar if you are - * familiar with Huffman trees and with other LZ77 and Huffman-based formats - * such as DEFLATE. Otherwise it can be quite tricky to understand. Basically - * it is the following: - * - * - Preprocess the input data (LZX-specific) - * - Go through the input data and determine matches. This part is based on - * code from zlib, and a hash table of 3-character strings is used to - * accelerate the process of finding matches. - * - Build the Huffman trees based on the frequencies of symbols determined - * while recording matches. - * - Output the block header, including the Huffman trees; then output the - * compressed stream of matches and literal characters. - * - * It is possible for a WIM chunk to include multiple LZX blocks, since for some - * input data this will produce a better compression ratio (especially since - * each block can include new Huffman codes). However, producing multiple LZX - * blocks from one input chunk is not yet implemented. + * This file contains a compressor for the LZX ("Lempel-Ziv eXtended") + * compression format, as used in the WIM (Windows IMaging) file format. + * + * Two different parsing algorithms are implemented: "near-optimal" and "lazy". + * "Near-optimal" is significantly slower than "lazy", but results in a better + * compression ratio. The "near-optimal" algorithm is used at the default + * compression level. + * + * This file may need some slight modifications to be used outside of the WIM + * format. In particular, in other situations the LZX block header might be + * slightly different, and a sliding window rather than a fixed-size window + * might be required. + * + * Note: LZX is a compression format derived from DEFLATE, the format used by + * zlib and gzip. Both LZX and DEFLATE use LZ77 matching and Huffman coding. + * Certain details are quite similar, such as the method for storing Huffman + * codes. However, the main differences are: + * + * - LZX preprocesses the data to attempt to make x86 machine code slightly more + * compressible before attempting to compress it further. + * + * - LZX uses a "main" alphabet which combines literals and matches, with the + * match symbols containing a "length header" (giving all or part of the match + * length) and an "offset slot" (giving, roughly speaking, the order of + * magnitude of the match offset). + * + * - LZX does not have static Huffman blocks (that is, the kind with preset + * Huffman codes); however it does have two types of dynamic Huffman blocks + * ("verbatim" and "aligned"). + * + * - LZX has a minimum match length of 2 rather than 3. Length 2 matches can be + * useful, but generally only if the parser is smart about choosing them. + * + * - In LZX, offset slots 0 through 2 actually represent entries in an LRU queue + * of match offsets. This is very useful for certain types of files, such as + * binary files that have repeating records. */ #ifdef HAVE_CONFIG_H # include "config.h" #endif -#include "wimlib.h" -#include "wimlib/compress.h" +#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 #include +#include + +#define LZX_OPTIM_ARRAY_LENGTH 4096 + +#define LZX_DIV_BLOCK_SIZE 32768 + +#define LZX_CACHE_PER_POS 8 + +#define LZX_MAX_MATCHES_PER_POS (LZX_MAX_MATCH_LEN - LZX_MIN_MATCH_LEN + 1) + +#define LZX_CACHE_LEN (LZX_DIV_BLOCK_SIZE * (LZX_CACHE_PER_POS + 1)) + +struct lzx_compressor; + +/* Codewords for the LZX Huffman codes. */ +struct lzx_codewords { + u32 main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; + u32 len[LZX_LENCODE_NUM_SYMBOLS]; + u32 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; +}; +/* Codeword lengths (in bits) for the LZX Huffman codes. + * A zero length means the corresponding codeword has zero frequency. */ +struct lzx_lens { + u8 main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; + u8 len[LZX_LENCODE_NUM_SYMBOLS]; + u8 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; +}; + +/* Estimated cost, in bits, to output each symbol in the LZX Huffman codes. */ +struct lzx_costs { + u8 main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; + u8 len[LZX_LENCODE_NUM_SYMBOLS]; + u8 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; +}; -/* Structure to contain the Huffman codes for the main, length, and aligned - * offset trees. */ +/* 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; +}; - u16 len_codewords[LZX_LENTREE_NUM_SYMBOLS]; - u8 len_lens[LZX_LENTREE_NUM_SYMBOLS]; +/* Symbol frequency counters for the LZX Huffman codes. */ +struct lzx_freqs { + u32 main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; + u32 len[LZX_LENCODE_NUM_SYMBOLS]; + u32 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; +}; + +/* Intermediate LZX match/literal format */ +struct lzx_item { - 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); } - len_pos_header = (position_slot << 3) | len_header; - wimlib_assert(len_pos_header < LZX_MAINTREE_NUM_SYMBOLS - LZX_NUM_CHARS); + /* If it's an aligned offset block, output the aligned offset code. */ + if (block_type == LZX_BLOCKTYPE_ALIGNED) { + for (int i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) { + lzx_write_bits(os, codes->lens.aligned[i], + LZX_ALIGNEDCODE_ELEMENT_SIZE); + } + } + + /* Output the main code (two parts). */ + lzx_write_compressed_code(os, codes->lens.main, + prev_lens->main, + LZX_NUM_CHARS); + lzx_write_compressed_code(os, codes->lens.main + LZX_NUM_CHARS, + prev_lens->main + LZX_NUM_CHARS, + num_main_syms - LZX_NUM_CHARS); + + /* Output the length code. */ + lzx_write_compressed_code(os, codes->lens.len, + prev_lens->len, + LZX_LENCODE_NUM_SYMBOLS); + + /* Output the compressed matches and literals. */ + lzx_write_items(os, block_type, chosen_items, num_chosen_items, codes); +} + +/* Don't allow matches to span the end of an LZX block. */ +static inline unsigned +maybe_truncate_matches(struct lz_match matches[], unsigned num_matches, + struct lzx_compressor *c) +{ + if (c->match_window_end < c->cur_window_size && num_matches != 0) { + u32 limit = c->match_window_end - c->match_window_pos; + + if (limit >= LZX_MIN_MATCH_LEN) { + + unsigned i = num_matches - 1; + do { + if (matches[i].len >= limit) { + matches[i].len = limit; + + /* Truncation might produce multiple + * matches with length 'limit'. Keep at + * most 1. */ + num_matches = i + 1; + } + } while (i--); + } else { + num_matches = 0; + } + } + return num_matches; +} + +static unsigned +lzx_get_matches_fillcache_singleblock(struct lzx_compressor *c, + const struct lz_match **matches_ret) +{ + struct lz_match *cache_ptr; + struct lz_match *matches; + unsigned num_matches; + + cache_ptr = c->cache_ptr; + matches = cache_ptr + 1; + if (likely(cache_ptr <= c->cache_limit)) { + num_matches = lz_mf_get_matches(c->mf, matches); + cache_ptr->len = num_matches; + c->cache_ptr = matches + num_matches; + } else { + num_matches = 0; + } + c->match_window_pos++; + *matches_ret = matches; + return num_matches; +} + +static unsigned +lzx_get_matches_fillcache_multiblock(struct lzx_compressor *c, + const struct lz_match **matches_ret) +{ + struct lz_match *cache_ptr; + struct lz_match *matches; + unsigned num_matches; + + cache_ptr = c->cache_ptr; + matches = cache_ptr + 1; + if (likely(cache_ptr <= c->cache_limit)) { + num_matches = lz_mf_get_matches(c->mf, matches); + num_matches = maybe_truncate_matches(matches, num_matches, c); + cache_ptr->len = num_matches; + c->cache_ptr = matches + num_matches; + } else { + num_matches = 0; + } + c->match_window_pos++; + *matches_ret = matches; + return num_matches; +} + +static unsigned +lzx_get_matches_usecache(struct lzx_compressor *c, + const struct lz_match **matches_ret) +{ + struct lz_match *cache_ptr; + struct lz_match *matches; + unsigned num_matches; + + cache_ptr = c->cache_ptr; + matches = cache_ptr + 1; + if (cache_ptr <= c->cache_limit) { + num_matches = cache_ptr->len; + c->cache_ptr = matches + num_matches; + } else { + num_matches = 0; + } + c->match_window_pos++; + *matches_ret = matches; + return num_matches; +} + +static unsigned +lzx_get_matches_usecache_nocheck(struct lzx_compressor *c, + const struct lz_match **matches_ret) +{ + struct lz_match *cache_ptr; + struct lz_match *matches; + unsigned num_matches; + + cache_ptr = c->cache_ptr; + matches = cache_ptr + 1; + num_matches = cache_ptr->len; + c->cache_ptr = matches + num_matches; + c->match_window_pos++; + *matches_ret = matches; + return num_matches; +} + +static unsigned +lzx_get_matches_nocache_singleblock(struct lzx_compressor *c, + const struct lz_match **matches_ret) +{ + struct lz_match *matches; + unsigned num_matches; - 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. * - * @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. + * This uses a wrapper function around the underlying match-finder. + * + * Returns the number of matches found and sets *matches_ret to point to the + * matches array. The matches will be sorted by strictly increasing length and + * offset. */ -static 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; + + /* Main code */ + for (i = 0; i < c->num_main_syms; i++) + c->costs.main[i] = lens->main[i] ? lens->main[i] : 15; - wimlib_assert(position_slot < LZX_NUM_POSITION_SLOTS); + /* Length code */ + for (i = 0; i < LZX_LENCODE_NUM_SYMBOLS; i++) + c->costs.len[i] = lens->len[i] ? lens->len[i] : 15; - num_extra_bits = lzx_get_num_extra_bits(position_slot); + /* 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; - /* 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)) { + /* Main code (part 2): Match header symbols */ + for (; i < num_main_syms; i++) + costs->main[i] = 10; - verbatim_bits = position_footer >> 3; - ret = bitstream_put_bits(out, verbatim_bits, - num_extra_bits - 3); - 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; +} - 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; +/* 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; - signed 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; + } - /* Run ended! Check if it is a run of zeroes or a run of - * nonzeroes. */ + cur_optimum_ptr = c->optimum; + cur_optimum_ptr->cost = 0; + cur_optimum_ptr->queue = *begin_queue; - /* 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]; + end_optimum_ptr = cur_optimum_ptr; - if (len_in_run == 0) { - /* A run of 0's. Encode it in as few length - * codes as we can. */ + /* The following loop runs once for each per byte in the window, except + * in a couple shortcut cases. */ + for (;;) { - /* 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) { + /* Find explicit offset matches with the current position. */ + num_matches = lzx_get_matches(c, &matches); - 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 (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); } - /* 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; + 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; + } + } - /* A run of nonzero lengths. */ + /* Consider coding a literal. - /* 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. - * - * 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 = -(signed 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; + * To avoid an extra unpredictable brench, actually checking the + * preferability of coding a literal is integrated into the + * queue update code below. */ + literal = *window_ptr++; + cost = cur_optimum_ptr->cost + lzx_literal_cost(literal, &c->costs); + + /* Advance to the next position. */ + cur_optimum_ptr++; + + /* The lowest-cost path to the current position is now known. + * Finalize the recent offsets queue that results from taking + * this lowest-cost path. */ + + if (cost < cur_optimum_ptr->cost) { + /* Literal: queue remains unchanged. */ + cur_optimum_ptr->cost = cost; + cur_optimum_ptr->mc_item_data = (literal << MC_OFFSET_SHIFT) | 1; + cur_optimum_ptr->queue = (cur_optimum_ptr - 1)->queue; + } else { + /* Match: queue update is needed. */ + len = cur_optimum_ptr->mc_item_data & MC_LEN_MASK; + offset_data = cur_optimum_ptr->mc_item_data >> MC_OFFSET_SHIFT; + if (offset_data >= LZX_NUM_RECENT_OFFSETS) { + /* Explicit offset match: offset is inserted at front */ + cur_optimum_ptr->queue.R[0] = offset_data - LZX_OFFSET_OFFSET; + cur_optimum_ptr->queue.R[1] = (cur_optimum_ptr - len)->queue.R[0]; + cur_optimum_ptr->queue.R[2] = (cur_optimum_ptr - len)->queue.R[1]; + } else { + /* Repeat offset match: offset is swapped to front */ + cur_optimum_ptr->queue = (cur_optimum_ptr - len)->queue; + swap(cur_optimum_ptr->queue.R[0], + cur_optimum_ptr->queue.R[offset_data]); } } - /* 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 = -(signed char)len_in_run; - if (delta < 0) - delta += 17; + /* + * 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; +} - pretree_freqs[(unsigned char)delta]++; - output_syms[output_syms_idx++] = delta; +/* 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; + } } - cur_run_len = 1; - } + /* 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; + } - wimlib_assert(output_syms_idx < ARRAY_LEN(output_syms)); + 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; + } - /* Build the pretree from the frequencies of the length symbols. */ + 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; + } - make_canonical_huffman_code(LZX_PRETREE_NUM_SYMBOLS, - LZX_MAX_CODEWORD_LEN, - pretree_freqs, pretree_lens, - pretree_codewords); + if (prev_len == 0 || cur_score > prev_score) { + /* No previous match, or the current match is better + * than the previous match. + * + * If there's a previous match, then output a literal in + * its place. + * + * In both cases, if the current match is very long, + * then output it immediately. Otherwise, attempt a + * lazy match by waiting to see if there's a better + * match at the next position. */ - /* 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); + if (prev_len) + lzx_declare_literal(c, *(window_ptr - 2), &next_chosen_item); - /* Write the length symbols, encoded with the pretree, to the output. */ + prev_len = cur_len; + prev_offset_data = cur_offset_data; + prev_score = cur_score; - 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; + if (prev_len >= c->params.nice_match_length) { + skip_len = prev_len - 1; + goto output_prev_match; + } + continue; + } + + /* Current match is not better than the previous match, so + * output the previous match. */ + + skip_len = prev_len - 2; + + output_prev_match: + if (prev_offset_data < LZX_NUM_RECENT_OFFSETS) { + lzx_declare_repeat_offset_match(c, prev_len, + prev_offset_data, + &next_chosen_item); + swap(c->queue.R[0], c->queue.R[prev_offset_data]); + } else { + lzx_declare_explicit_offset_match(c, prev_len, + prev_offset_data - LZX_OFFSET_OFFSET, + &next_chosen_item); + c->queue.R[2] = c->queue.R[1]; + c->queue.R[1] = c->queue.R[0]; + c->queue.R[0] = prev_offset_data - LZX_OFFSET_OFFSET; } + lz_mf_skip_positions(mf, skip_len); + window_ptr += skip_len; + prev_len = 0; } - return 0; + + return next_chosen_item - c->chosen_items; } -/* 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) +/* 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) { - make_canonical_huffman_code(LZX_MAINTREE_NUM_SYMBOLS, - LZX_MAX_CODEWORD_LEN, - freq_tabs->main_freq_table, - codes->main_lens, - codes->main_codewords); + 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]; + } - make_canonical_huffman_code(LZX_LENTREE_NUM_SYMBOLS, - LZX_MAX_CODEWORD_LEN, - freq_tabs->len_freq_table, - codes->len_lens, - codes->len_codewords); + /* Account for output of the aligned offset code. */ + aligned_cost += LZX_ALIGNEDCODE_ELEMENT_SIZE * LZX_ALIGNEDCODE_NUM_SYMBOLS; - make_canonical_huffman_code(LZX_ALIGNEDTREE_NUM_SYMBOLS, 8, - freq_tabs->aligned_freq_table, - codes->aligned_lens, - codes->aligned_codewords); + if (aligned_cost < verbatim_cost) + return LZX_BLOCKTYPE_ALIGNED; + else + return LZX_BLOCKTYPE_VERBATIM; } -static void -do_call_insn_translation(u32 *call_insn_target, int input_pos, - s32 file_size) +/* Near-optimal parsing */ +static u32 +lzx_choose_near_optimal_items_for_block(struct lzx_compressor *c, + u32 block_start_pos, u32 block_size) { - s32 abs_offset; - s32 rel_offset; + 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; + } - 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; + /* No matches will extend beyond the end of the block. */ + c->match_window_end = block_start_pos + block_size; + + /* The first optimization pass will use a default cost model. Each + * additional optimization pass will use a cost model computed from the + * previous pass. + * + * To improve performance we only generate the array containing the + * matches and literals in intermediate form on the final pass. For + * earlier passes, tallying symbol frequencies is sufficient. */ + lzx_set_default_costs(&c->costs, c->num_main_syms); + + next_chosen_item_ptr = NULL; + orig_queue = c->queue; + do { + /* Reset the match-finder wrapper. */ + c->match_window_pos = block_start_pos; + c->cache_ptr = c->cached_matches; + + if (num_passes_remaining == 1) { + /* Last pass: actually generate the items. */ + next_chosen_item = c->chosen_items; + next_chosen_item_ptr = &next_chosen_item; } - *call_insn_target = cpu_to_le32(abs_offset); - } + + /* Choose the items. */ + lzx_optim_pass(c, next_chosen_item_ptr); + + if (num_passes_remaining > 1) { + /* This isn't the last pass. */ + + /* Make the Huffman codes from the symbol frequencies. */ + lzx_make_huffman_codes(&c->freqs, &c->codes[c->codes_index], + c->num_main_syms); + + /* Update symbol costs. */ + lzx_set_costs(c, &c->codes[c->codes_index].lens); + + /* Reset symbol frequencies. */ + memset(&c->freqs, 0, sizeof(c->freqs)); + + /* Reset the match offset LRU queue to what it was at + * the beginning of the block. */ + c->queue = orig_queue; + + /* Choose appopriate match-finder wrapper functions. */ + if (c->cache_ptr <= c->cache_limit) { + c->get_matches_func = lzx_get_matches_usecache_nocheck; + c->skip_bytes_func = lzx_skip_bytes_usecache_nocheck; + } else { + c->get_matches_func = lzx_get_matches_usecache; + c->skip_bytes_func = lzx_skip_bytes_usecache; + } + } + } while (--num_passes_remaining); + + /* Return the number of items chosen. */ + return next_chosen_item - c->chosen_items; } -/* This is the reverse of undo_call_insn_preprocessing() in lzx-decompress.c. - * See the comment above that function for more information. */ +/* + * Choose the matches/literals with which to output the block of data beginning + * at '&c->cur_window[block_start_pos]' and extending for 'block_size' bytes. + * + * The frequences of the Huffman symbols in the block will be tallied in + * 'c->freqs'. + * + * 'c->queue' must specify the state of the queue at the beginning of this block. + * This function will update it to the state of the queue at the end of this + * block. + * + * Returns the number of matches/literals that were chosen and written to + * 'c->chosen_items' in the 'struct lzx_item' intermediate representation. + */ +static u32 +lzx_choose_items_for_block(struct lzx_compressor *c, + u32 block_start_pos, u32 block_size) +{ + return (*c->params.choose_items_for_block)(c, block_start_pos, block_size); +} + +/* Initialize c->offset_slot_fast. */ static void -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_init_offset_slot_fast(struct lzx_compressor *c) +{ + u8 slot = 0; + + for (u32 offset = 0; offset < LZX_NUM_FAST_OFFSETS; offset++) { + + while (offset + LZX_OFFSET_OFFSET >= lzx_offset_slot_base[slot + 1]) + slot++; + + c->offset_slot_fast[offset] = slot; } } +/* Set internal compression parameters for the specified compression level and + * maximum window size. */ +static void +lzx_build_params(unsigned int compression_level, u32 max_window_size, + struct lzx_compressor_params *lzx_params) +{ + if (compression_level < 25) { -static const struct lz_params lzx_lz_params = { + /* Fast compression: Use lazy parsing. */ - /* LZX_MIN_MATCH == 2, but 2-character matches are rarely useful; the - * minimum match for compression is set to 3 instead. */ - .min_match = 3, + lzx_params->choose_items_for_block = lzx_choose_lazy_items_for_block; + lzx_params->num_optim_passes = 1; - .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, -}; + /* 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 { -/* API function documented in wimlib.h */ -WIMLIBAPI unsigned -wimlib_lzx_compress(const void *_uncompressed_data, unsigned uncompressed_len, - void *compressed_data) -{ - 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; + /* Normal / high compression: Use near-optimal parsing. */ - wimlib_assert(uncompressed_len <= 32768); + lzx_params->choose_items_for_block = lzx_choose_near_optimal_items_for_block; - if (uncompressed_len < 100) - return 0; + /* Set a number of optimization passes appropriate for the + * compression level. */ + + lzx_params->num_optim_passes = 1; + + if (compression_level >= 40) + lzx_params->num_optim_passes++; + + /* Use more optimization passes for higher compression levels. + * But the more passes there are, the less they help --- so + * don't add them linearly. */ + if (compression_level >= 70) { + lzx_params->num_optim_passes++; + if (compression_level >= 100) + lzx_params->num_optim_passes++; + if (compression_level >= 150) + lzx_params->num_optim_passes++; + if (compression_level >= 200) + lzx_params->num_optim_passes++; + if (compression_level >= 300) + lzx_params->num_optim_passes++; + } + + /* When doing near-optimal parsing, the hash chain match-finding + * algorithm is good if the window size is small and we're only + * doing one optimization pass. Otherwise, the binary tree + * algorithm is the way to go. */ + if (max_window_size <= 32768 && lzx_params->num_optim_passes == 1) + lzx_params->mf_algo = LZ_MF_HASH_CHAINS; + else + lzx_params->mf_algo = LZ_MF_BINARY_TREES; + + /* When doing near-optimal parsing, allow length 2 matches if + * the compression level is sufficiently high. */ + if (compression_level >= 45) + lzx_params->min_match_length = 2; + else + lzx_params->min_match_length = 3; + + /* Scale nice_match_length and max_search_depth with the + * compression level. */ + lzx_params->nice_match_length = min(((u64)compression_level * 32) / 50, + LZX_MAX_MATCH_LEN); + lzx_params->max_search_depth = min(((u64)compression_level * 50) / 50, + LZX_MAX_MATCH_LEN); + } +} + +/* Given the internal compression parameters and maximum window size, build the + * Lempel-Ziv match-finder parameters. */ +static void +lzx_build_mf_params(const struct lzx_compressor_params *lzx_params, + u32 max_window_size, struct lz_mf_params *mf_params) +{ + memset(mf_params, 0, sizeof(*mf_params)); + + mf_params->algorithm = lzx_params->mf_algo; + mf_params->max_window_size = max_window_size; + mf_params->min_match_len = lzx_params->min_match_length; + mf_params->max_match_len = LZX_MAX_MATCH_LEN; + mf_params->max_search_depth = lzx_params->max_search_depth; + mf_params->nice_match_len = lzx_params->nice_match_length; +} - memset(&freq_tabs, 0, sizeof(freq_tabs)); - queue.R0 = 1; - queue.R1 = 1; - queue.R2 = 1; +static void +lzx_free_compressor(void *_c); - /* The input data must be preprocessed. To avoid changing the original - * input, copy it to a temporary buffer. */ - memcpy(uncompressed_data, _uncompressed_data, uncompressed_len); - memset(uncompressed_data + uncompressed_len, 0, 8); +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; - /* Before doing any actual compression, do the call instruction (0xe8 - * byte) translation on the uncompressed data. */ - do_call_insn_preprocessing(uncompressed_data, uncompressed_len); + window_order = lzx_get_window_order(max_block_size); + if (window_order == 0) + return 0; + max_window_size = max_block_size; - /* 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_build_params(compression_level, max_window_size, ¶ms); - 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); + size += sizeof(struct lzx_compressor); - lzx_make_huffman_codes(&freq_tabs, &codes); + /* cur_window */ + size += max_window_size; - /* Initialize the output bitstream. */ - init_output_bitstream(&ostream, compressed_data, uncompressed_len - 1); + /* mf */ + size += lz_mf_get_needed_memory(params.mf_algo, max_window_size); - /* 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); + /* 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; +} - /* 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); +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 { - bitstream_put_bits(&ostream, 0, 1); - bitstream_put_bits(&ostream, uncompressed_len, 16); + c->cached_matches = MALLOC(LZX_MAX_MATCHES_PER_POS * + sizeof(struct lz_match)); + if (!c->cached_matches) + goto oom; } - /* 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) - return 0; + lzx_init_offset_slot_fast(c); - /* Write the pre-tree and symbols for the rest of the main tree. */ - ret = lzx_write_compressed_tree(&ostream, codes.main_lens + - LZX_NUM_CHARS, - LZX_MAINTREE_NUM_SYMBOLS - - LZX_NUM_CHARS); - if (ret) - return 0; + *c_ret = c; + return 0; - /* Write the pre-tree and symbols for the length tree. */ - ret = lzx_write_compressed_tree(&ostream, codes.len_lens, - LZX_LENTREE_NUM_SYMBOLS); - if (ret) - return 0; +oom: + lzx_free_compressor(c); + return WIMLIB_ERR_NOMEM; +} - /* Write the compressed literals. */ - ret = lzx_write_compressed_literals(&ostream, block_type, - match_tab, num_matches, &codes); - if (ret) +static size_t +lzx_compress(const void *uncompressed_data, size_t uncompressed_size, + void *compressed_data, size_t compressed_size_avail, void *_c) +{ + struct lzx_compressor *c = _c; + struct lzx_output_bitstream os; + u32 num_chosen_items; + const struct lzx_lens *prev_lens; + u32 block_start_pos; + u32 block_size; + int block_type; + + /* Don't bother compressing very small inputs. */ + if (uncompressed_size < 100) return 0; - ret = flush_output_bitstream(&ostream); - if (ret) - return 0; + /* The input data must be preprocessed. To avoid changing the original + * input data, copy it to a temporary buffer. */ + memcpy(c->cur_window, uncompressed_data, uncompressed_size); + c->cur_window_size = uncompressed_size; - compressed_len = ostream.bit_output - (u8*)compressed_data; - -#ifdef ENABLE_VERIFY_COMPRESSION - /* Verify that we really get the same thing back when decompressing. */ - { - u8 buf[uncompressed_len]; - ret = wimlib_lzx_decompress(compressed_data, compressed_len, - buf, uncompressed_len); - if (ret != 0) { - ERROR("lzx_compress(): Failed to decompress data we compressed"); - abort(); - } + /* 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 compressed_len; } + +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, +};