X-Git-Url: https://wimlib.net/git/?p=wimlib;a=blobdiff_plain;f=src%2Flzx-compress.c;h=513b09dc66ec63c9596f22519c4e777d51de33df;hp=c829a4272d5b2011ba619e5dc06f30c6e93908e0;hb=5d0f0ceca613ee64592512290ab36140e053942b;hpb=720db87557918105b17b51b03f264ddb9b89d2b9 diff --git a/src/lzx-compress.c b/src/lzx-compress.c index c829a427..513b09dc 100644 --- a/src/lzx-compress.c +++ b/src/lzx-compress.c @@ -1,13 +1,9 @@ /* * lzx-compress.c - * - * LZX compression routines, originally based on code written by Matthew T. - * Russotto (liblzxcomp), but heavily modified. */ /* - * 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. * @@ -27,168 +23,285 @@ /* - * This file provides lzx_compress(), a function to compress an in-memory buffer - * of data using LZX compression, as used in the WIM file format. - * - * Please see the comments in lzx-decompress.c for more information about this - * compression format. - * - * One thing to keep in mind is that there is no sliding window, since the - * window is always the entirety of a WIM chunk, which is at most WIM_CHUNK_SIZE - * ( = 32768) bytes. - * - * The basic compression algorithm used here should be familiar if you are - * familiar with Huffman trees and with other LZ77 and Huffman-based formats - * such as DEFLATE. Otherwise it can be quite tricky to understand. Basically - * it is the following: - * - * - Preprocess the input data (LZX-specific) - * - Go through the input data and determine matches. This part is based on - * code from zlib, and a hash table of 3-character strings is used to - * accelerate the process of finding matches. - * - Build the Huffman trees based on the frequencies of symbols determined - * while recording matches. - * - Output the block header, including the Huffman trees; then output the - * compressed stream of matches and literal characters. - * - * It is possible for a WIM chunk to include multiple LZX blocks, since for some - * input data this will produce a better compression ratio (especially since - * each block can include new Huffman codes). However, producing multiple LZX - * blocks from one input chunk is not yet implemented. + * This file contains a compressor for the LZX ("Lempel-Ziv eXtended"?) + * compression format, as used in the WIM (Windows IMaging) file format. This + * code 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. + * + * ---------------------------------------------------------------------------- + * + * Format Overview + * + * The primary reference for LZX is the specification released by Microsoft. + * However, the comments in lzx-decompress.c provide more information about LZX + * and note some errors in the Microsoft specification. + * + * LZX shares many similarities with 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 a "position 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. + * + * - In LZX, match offsets 0 through 2 actually represent entries in an LRU + * queue of match offsets. This is very useful for certain types of files, + * such as binary files that have repeating records. + * + * ---------------------------------------------------------------------------- + * + * Algorithmic Overview + * + * At a high level, any implementation of LZX compression must operate as + * follows: + * + * 1. Preprocess the input data to translate the targets of 32-bit x86 call + * instructions to absolute offsets. (Actually, this is required for WIM, + * but might not be in other places LZX is used.) + * + * 2. Find a sequence of LZ77-style matches and literal bytes that expands to + * the preprocessed data. + * + * 3. Divide the match/literal sequence into one or more LZX blocks, each of + * which may be "uncompressed", "verbatim", or "aligned". + * + * 4. Output each LZX block. + * + * Step (1) is fairly straightforward. It requires looking for 0xe8 bytes in + * the input data and performing a translation on the 4 bytes following each + * one. + * + * Step (4) is complicated, but it is mostly determined by the LZX format. The + * only real choice we have is what algorithm to use to build the length-limited + * canonical Huffman codes. See lzx_write_all_blocks() for details. + * + * That leaves steps (2) and (3) as where all the hard stuff happens. Focusing + * on step (2), we need to do LZ77-style parsing on the input data, or "window", + * to divide it into a sequence of matches and literals. Each position in the + * window might have multiple matches associated with it, and we need to choose + * which one, if any, to actually use. Therefore, the problem can really be + * divided into two areas of concern: (a) finding matches at a given position, + * which we shall call "match-finding", and (b) choosing whether to use a + * match or a literal at a given position, and if using a match, which one (if + * there is more than one available). We shall call this "match-choosing". We + * first consider match-finding, then match-choosing. + * + * ---------------------------------------------------------------------------- + * + * Match-finding + * + * Given a position in the window, we want to find LZ77-style "matches" with + * that position at previous positions in the window. With LZX, the minimum + * match length is 2 and the maximum match length is 257. The only restriction + * on offsets is that LZX does not allow the last 2 bytes of the window to match + * the the beginning of the window. + * + * Depending on how good a compression ratio we want (see the "Match-choosing" + * section), we may want to find: (a) all matches, or (b) just the longest + * match, or (c) just some "promising" matches that we are able to find quickly, + * or (d) just the longest match that we're able to find quickly. Below we + * introduce the match-finding methods that the code currently uses or has + * previously used: + * + * - Hash chains. Maintain a table that maps hash codes, computed from + * fixed-length byte sequences, to linked lists containing previous window + * positions. To search for matches, compute the hash for the current + * position in the window and search the appropriate hash chain. When + * advancing to the next position, prepend the current position to the + * appropriate hash list. This is a good approach for producing matches with + * stategy (d) and is useful for fast compression. Therefore, we provide an + * option to use this method for LZX compression. See lz_hash.c for the + * implementation. + * + * - Binary trees. Similar to hash chains, but each hash bucket contains a + * binary tree of previous window positions rather than a linked list. This + * is a good approach for producing matches with stategy (c) and is useful for + * achieving a good compression ratio. Therefore, we provide an option to use + * this method; see lz_bt.c for the implementation. + * + * - Suffix arrays. This code previously used this method to produce matches + * with stategy (c), but I've dropped it because it was slower than the binary + * trees approach, used more memory, and did not improve the compression ratio + * enough to compensate. Download wimlib v1.6.2 if you want the code. + * However, the suffix array method was basically as follows. Build the + * suffix array for the entire window. The suffix array contains each + * possible window position, sorted by the lexicographic order of the strings + * that begin at those positions. Find the matches at a given position by + * searching the suffix array outwards, in both directions, from the suffix + * array slot for that position. This produces the longest matches first, but + * "matches" that actually occur at later positions in the window must be + * skipped. To do this skipping, use an auxiliary array with dynamically + * constructed linked lists. Also, use the inverse suffix array to quickly + * find the suffix array slot for a given position without doing a binary + * search. + * + * ---------------------------------------------------------------------------- + * + * Match-choosing + * + * Usually, choosing the longest match is best because it encodes the most data + * in that one item. However, sometimes the longest match is not optimal + * because (a) choosing a long match now might prevent using an even longer + * match later, or (b) more generally, what we actually care about is the number + * of bits it will ultimately take to output each match or literal, which is + * actually dependent on the entropy encoding using by the underlying + * compression format. Consequently, a longer match usually, but not always, + * takes fewer bits to encode than multiple shorter matches or literals that + * cover the same data. + * + * This problem of choosing the truly best match/literal sequence is probably + * impossible to solve efficiently when combined with entropy encoding. If we + * knew how many bits it takes to output each match/literal, then we could + * choose the optimal sequence using shortest-path search a la Dijkstra's + * algorithm. However, with entropy encoding, the chosen match/literal sequence + * affects its own encoding. Therefore, we can't know how many bits it will + * take to actually output any one match or literal until we have actually + * chosen the full sequence of matches and literals. + * + * Notwithstanding the entropy encoding problem, we also aren't guaranteed to + * choose the optimal match/literal sequence unless the match-finder (see + * section "Match-finder") provides the match-chooser with all possible matches + * at each position. However, this is not computationally efficient. For + * example, there might be many matches of the same length, and usually (but not + * always) the best choice is the one with the smallest offset. So in practice, + * it's fine to only consider the smallest offset for a given match length at a + * given position. (Actually, for LZX, it's also worth considering repeat + * offsets.) + * + * In addition, as mentioned earlier, in LZX we have the choice of using + * multiple blocks, each of which resets the Huffman codes. This expands the + * search space even further. Therefore, to simplify the problem, we currently + * we don't attempt to actually choose the LZX blocks based on the data. + * Instead, we just divide the data into fixed-size blocks of LZX_DIV_BLOCK_SIZE + * bytes each, and always use verbatim or aligned blocks (never uncompressed). + * A previous version of this code recursively split the input data into + * equal-sized blocks, up to a maximum depth, and chose the lowest-cost block + * divisions. However, this made compression much slower and did not actually + * help very much. It remains an open question whether a sufficiently fast and + * useful block-splitting algorithm is possible for LZX. Essentially the same + * problem also applies to DEFLATE. The Microsoft LZX compressor seemingly does + * do block splitting, although I don't know how fast or useful it is, + * specifically. + * + * Now, back to the entropy encoding problem. The "solution" is to use an + * iterative approach to compute a good, but not necessarily optimal, + * match/literal sequence. Start with a fixed assignment of symbol costs and + * choose an "optimal" match/literal sequence based on those costs, using + * shortest-path seach a la Dijkstra's algorithm. Then, for each iteration of + * the optimization, update the costs based on the entropy encoding of the + * current match/literal sequence, then choose a new match/literal sequence + * based on the updated costs. Usually, the actual cost to output the current + * match/literal sequence will decrease in each iteration until it converges on + * a fixed point. This result may not be the truly optimal match/literal + * sequence, but it usually is much better than one chosen by doing a "greedy" + * parse where we always chooe the longest match. + * + * An alternative to both greedy parsing and iterative, near-optimal parsing is + * "lazy" parsing. Briefly, "lazy" parsing considers just the longest match at + * each position, but it waits to choose that match until it has also examined + * the next position. This is actually a useful approach; it's used by zlib, + * for example. Therefore, for fast compression we combine lazy parsing with + * the hash chain max-finder. For normal/high compression we combine + * near-optimal parsing with the binary tree match-finder. + * + * Anyway, if you've read through this comment, you hopefully should have a + * better idea of why things are done in a certain way in this LZX compressor, + * as well as in other compressors for LZ77-based formats (including third-party + * ones). In my opinion, the phrase "compression algorithm" is often mis-used + * in place of "compression format", since there can be many different + * algorithms that all generate compressed data in the same format. The + * challenge is to design an algorithm that is efficient but still gives a good + * compression ratio. */ -#include "lzx.h" -#include "compress.h" -#include +#ifdef HAVE_CONFIG_H +# include "config.h" +#endif + +#include "wimlib.h" +#include "wimlib/compressor_ops.h" +#include "wimlib/compress_common.h" +#include "wimlib/endianness.h" +#include "wimlib/error.h" +#include "wimlib/lz.h" +#include "wimlib/lz_hash.h" +#include "wimlib/lz_bt.h" +#include "wimlib/lzx.h" +#include "wimlib/util.h" #include +#ifdef ENABLE_LZX_DEBUG +# include "wimlib/decompress_common.h" +#endif -/* Structure to contain the Huffman codes for the main, length, and aligned - * offset trees. */ -struct lzx_codes { - u16 main_codewords[LZX_MAINTREE_NUM_SYMBOLS]; - u8 main_lens[LZX_MAINTREE_NUM_SYMBOLS]; +#define LZX_OPTIM_ARRAY_SIZE 4096 - u16 len_codewords[LZX_LENTREE_NUM_SYMBOLS]; - u8 len_lens[LZX_LENTREE_NUM_SYMBOLS]; +#define LZX_DIV_BLOCK_SIZE 32768 - u16 aligned_codewords[LZX_ALIGNEDTREE_NUM_SYMBOLS]; - u8 aligned_lens[LZX_ALIGNEDTREE_NUM_SYMBOLS]; -}; +#define LZX_CACHE_PER_POS 8 + +#define LZX_CACHE_LEN (LZX_DIV_BLOCK_SIZE * (LZX_CACHE_PER_POS + 1)) +#define LZX_CACHE_SIZE (LZX_CACHE_LEN * sizeof(struct lz_match)) +#define LZX_MAX_MATCHES_PER_POS (LZX_MAX_MATCH_LEN - LZX_MIN_MATCH_LEN + 1) -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]; +/* Codewords for the LZX main, length, and aligned offset Huffman codes */ +struct lzx_codewords { + u32 main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; + u32 len[LZX_LENCODE_NUM_SYMBOLS]; + u32 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; }; -/* Returns the LZX position slot that corresponds to a given formatted offset. +/* Codeword lengths (in bits) for the LZX main, length, and aligned offset + * Huffman codes. * - * Logically, this returns the smallest i such that - * formatted_offset >= lzx_position_base[i]. - * - * 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. + * A 0 length means the codeword has zero frequency. */ -static inline unsigned -lzx_get_position_slot(unsigned formatted_offset) -{ -#if 0 - /* - * Slots 36-49 (formatted_offset >= 262144) can be found by - * (formatted_offset/131072) + 34 == (formatted_offset >> 17) + 34; - * however, this check for formatted_offset >= 262144 is commented out - * because WIM chunks cannot be that large. - */ - if (formatted_offset >= 262144) { - return (formatted_offset >> 17) + 34; - } else -#endif - { - /* Note: this part here only works if: - * - * 2 <= formatted_offset < 655360 - * - * It is < 655360 because the frequency of the position bases - * increases starting at the 655360 entry, and it is >= 2 - * because the below calculation fails if the most significant - * bit is lower than the 2's place. */ - wimlib_assert(formatted_offset >= 2 && formatted_offset < 655360); - unsigned mssb_idx = bsr32(formatted_offset); - return (mssb_idx << 1) | - ((formatted_offset >> (mssb_idx - 1)) & 1); - } -} - -static u32 -lzx_record_literal(u8 literal, void *__main_freq_tab) -{ - freq_t *main_freq_tab = __main_freq_tab; - main_freq_tab[literal]++; - return literal; -} - -/* Constructs a match from an offset and a length, and updates the LRU queue and - * the frequency of symbols in the main, length, and aligned offset alphabets. - * The return value is a 32-bit number that provides the match in an - * intermediate representation documented below. */ -static u32 -lzx_record_match(unsigned match_offset, unsigned match_len, - void *__freq_tabs, void *__queue) -{ - struct lzx_freq_tables *freq_tabs = __freq_tabs; - struct lru_queue *queue = __queue; - unsigned position_slot; - unsigned position_footer = 0; - u32 match; - u32 len_header; - u32 len_pos_header; - unsigned len_footer; - unsigned adjusted_match_len; - - wimlib_assert(match_len >= LZX_MIN_MATCH && match_len <= LZX_MAX_MATCH); - wimlib_assert(match_offset != 0); - - /* If possible, encode this offset as a repeated offset. */ - if (match_offset == queue->R0) { - position_slot = 0; - } else if (match_offset == queue->R1) { - swap(queue->R0, queue->R1); - position_slot = 1; - } else if (match_offset == queue->R2) { - swap(queue->R0, queue->R2); - position_slot = 2; - } else { - /* Not a repeated offset. */ - - /* offsets of 0, 1, and 2 are reserved for the repeated offset - * codes, so non-repeated offsets must be encoded as 3+. The - * minimum offset is 1, so encode the offsets offset by 2. */ - unsigned formatted_offset = match_offset + LZX_MIN_MATCH; - - queue->R2 = queue->R1; - queue->R1 = queue->R0; - queue->R0 = match_offset; +struct lzx_lens { + u8 main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; + u8 len[LZX_LENCODE_NUM_SYMBOLS]; + u8 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; +}; - /* 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. */ +/* Costs for the LZX main, length, and aligned offset Huffman symbols. + * + * If a codeword has zero frequency, it must still be assigned some nonzero cost + * --- generally a high cost, since even if it gets used in the next iteration, + * it probably will not be used very many times. */ +struct lzx_costs { + u8 main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; + u8 len[LZX_LENCODE_NUM_SYMBOLS]; + u8 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; +}; - position_slot = lzx_get_position_slot(formatted_offset); - position_footer = formatted_offset & - ((1 << lzx_get_num_extra_bits(position_slot)) - 1); - } +/* The LZX main, length, and aligned offset Huffman codes */ +struct lzx_codes { + struct lzx_codewords codewords; + struct lzx_lens lens; +}; - adjusted_match_len = match_len - LZX_MIN_MATCH; +/* Tables for tallying symbol frequencies in the three LZX alphabets */ +struct lzx_freqs { + u32 main[LZX_MAINCODE_MAX_NUM_SYMBOLS]; + u32 len[LZX_LENCODE_NUM_SYMBOLS]; + u32 aligned[LZX_ALIGNEDCODE_NUM_SYMBOLS]; +}; - /* Pack the position slot, position footer, and match length into an - * intermediate representation. - * - * bits description - * ---- ----------------------------------------------------------- +/* LZX intermediate match/literal format */ +struct lzx_item { + /* Bit Description * * 31 1 if a match, 0 if a literal. * @@ -197,230 +310,347 @@ lzx_record_match(unsigned match_offset, unsigned match_len, * * 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). + * (since lzx_extra_bits[LZX_MAX_POSITION_SLOTS - 1] is 17). * - * 0-7 length of match, offset by 2. This can be at most - * (LZX_MAX_MATCH - 2) == 255, so it will fit in 8 bits. */ - match = 0x80000000 | - (position_slot << 25) | - (position_footer << 8) | - (adjusted_match_len); + * 0-7 length of match, minus 2. This can be at most + * (LZX_MAX_MATCH_LEN - 2) == 255, so it will fit in 8 bits. */ + u32 data; +}; + +/* Specification for an LZX block. */ +struct lzx_block_spec { + + /* One of the LZX_BLOCKTYPE_* constants indicating which type of this + * block. */ + int block_type; + + /* 0-based position in the window at which this block starts. */ + u32 window_pos; - /* The match length must be at least 2, so let the adjusted match length - * be the match length minus 2. + /* The number of bytes of uncompressed data this block represents. */ + u32 block_size; + + /* The match/literal sequence for this block. */ + struct lzx_item *chosen_items; + + /* The length of the @chosen_items sequence. */ + u32 num_chosen_items; + + /* Huffman codes for this block. */ + struct lzx_codes codes; +}; + +/* State of the LZX compressor. */ +struct lzx_compressor { + + /* The parameters that were used to create the compressor. */ + struct wimlib_lzx_compressor_params params; + + /* The buffer of data to be compressed. * - * If it is less than 7, the adjusted match length is encoded as a 3-bit - * number offset by 2. Otherwise, the 3-bit length header is all 1's - * and the actual adjusted length is given as a symbol encoded with the - * length tree, offset by 7. - */ - if (adjusted_match_len < LZX_NUM_PRIMARY_LENS) { - len_header = adjusted_match_len; - } else { - len_header = LZX_NUM_PRIMARY_LENS; - len_footer = adjusted_match_len - LZX_NUM_PRIMARY_LENS; - freq_tabs->len_freq_table[len_footer]++; + * 0xe8 byte preprocessing is done directly on the data here before + * further compression. + * + * Note that this compressor does *not* use a real sliding window!!!! + * It's not needed in the WIM format, since every chunk is compressed + * independently. This is by design, to allow random access to the + * chunks. + * + * We reserve a few extra bytes to potentially allow reading off the end + * of the array in the match-finding code for optimization purposes + * (currently only needed for the hash chain match-finder). */ + u8 *window; + + /* Number of bytes of data to be compressed, which is the number of + * bytes of data in @window that are actually valid. */ + u32 window_size; + + /* Allocated size of the @window. */ + u32 max_window_size; + + /* Number of symbols in the main alphabet (depends on the + * @max_window_size since it determines the maximum allowed offset). */ + unsigned num_main_syms; + + /* The current match offset LRU queue. */ + struct lzx_lru_queue queue; + + /* Space for the sequences of matches/literals that were chosen for each + * block. */ + struct lzx_item *chosen_items; + + /* Information about the LZX blocks the preprocessed input was divided + * into. */ + struct lzx_block_spec *block_specs; + + /* Number of LZX blocks the input was divided into; a.k.a. the number of + * elements of @block_specs that are valid. */ + unsigned num_blocks; + + /* This is simply filled in with zeroes and used to avoid special-casing + * the output of the first compressed Huffman code, which conceptually + * has a delta taken from a code with all symbols having zero-length + * codewords. */ + struct lzx_codes zero_codes; + + /* The current cost model. */ + struct lzx_costs costs; + + /* Fast algorithm only: Array of hash table links. */ + u32 *prev_tab; + + /* Slow algorithm only: Binary tree match-finder. */ + struct lz_bt mf; + + /* Position in window of next match to return. */ + u32 match_window_pos; + + /* The end-of-block position. We can't allow any matches to span this + * position. */ + u32 match_window_end; + + /* Matches found by the match-finder are cached in the following array + * to achieve a slight speedup when the same matches are needed on + * subsequent passes. This is suboptimal because different matches may + * be preferred with different cost models, but seems to be a worthwhile + * speedup. */ + struct lz_match *cached_matches; + struct lz_match *cache_ptr; + bool matches_cached; + struct lz_match *cache_limit; + + /* Match-chooser state. + * When matches have been chosen, optimum_cur_idx is set to the position + * in the window of the next match/literal to return and optimum_end_idx + * is set to the position in the window at the end of the last + * match/literal to return. */ + struct lzx_mc_pos_data *optimum; + unsigned optimum_cur_idx; + unsigned optimum_end_idx; +}; + +/* + * Match chooser position data: + * + * An array of these structures is used during the match-choosing algorithm. + * They correspond to consecutive positions in the window and are used to keep + * track of the cost to reach each position, and the match/literal choices that + * need to be chosen to reach that position. + */ +struct lzx_mc_pos_data { + /* The approximate minimum cost, in bits, to reach this position in the + * window which has been found so far. */ + u32 cost; +#define MC_INFINITE_COST ((u32)~0UL) + + /* The union here is just for clarity, since the fields are used in two + * slightly different ways. Initially, the @prev structure is filled in + * first, and links go from later in the window to earlier in the + * window. Later, @next structure is filled in and links go from + * earlier in the window to later in the window. */ + union { + struct { + /* Position of the start of the match or literal that + * was taken to get to this position in the approximate + * minimum-cost parse. */ + u32 link; + + /* Offset (as in an LZ (length, offset) pair) of the + * match or literal that was taken to get to this + * position in the approximate minimum-cost parse. */ + u32 match_offset; + } prev; + struct { + /* Position at which the match or literal starting at + * this position ends in the minimum-cost parse. */ + u32 link; + + /* Offset (as in an LZ (length, offset) pair) of the + * match or literal starting at this position in the + * approximate minimum-cost parse. */ + u32 match_offset; + } next; + }; + + /* Adaptive state that exists after an approximate minimum-cost path to + * reach this position is taken. */ + struct lzx_lru_queue queue; +}; + +/* Returns the LZX position slot that corresponds to a given match offset, + * taking into account the recent offset queue and updating it if the offset is + * found in it. */ +static unsigned +lzx_get_position_slot(u32 offset, struct lzx_lru_queue *queue) +{ + unsigned position_slot; + + /* See if the offset was recently used. */ + for (int i = 0; i < LZX_NUM_RECENT_OFFSETS; i++) { + if (offset == queue->R[i]) { + /* Found it. */ + + /* Bring the repeat offset to the front of the + * queue. Note: this is, in fact, not a real + * LRU queue because repeat matches are simply + * swapped to the front. */ + swap(queue->R[0], queue->R[i]); + + /* The resulting position slot is simply the first index + * at which the offset was found in the queue. */ + return i; + } } - len_pos_header = (position_slot << 3) | len_header; - wimlib_assert(len_pos_header < LZX_MAINTREE_NUM_SYMBOLS - LZX_NUM_CHARS); + /* The offset was not recently used; look up its real position slot. */ + position_slot = lzx_get_position_slot_raw(offset + LZX_OFFSET_OFFSET); - freq_tabs->main_freq_table[len_pos_header + LZX_NUM_CHARS]++; + /* Bring the new offset to the front of the queue. */ + for (int i = LZX_NUM_RECENT_OFFSETS - 1; i > 0; i--) + queue->R[i] = queue->R[i - 1]; + queue->R[0] = offset; - /* Equivalent to: - * if (lzx_extra_bits[position_slot] >= 3) */ - if (position_slot >= 8) - freq_tabs->aligned_freq_table[position_footer & 7]++; + return position_slot; +} - return match; +/* Build the main, length, and aligned offset Huffman codes used in LZX. + * + * This takes as input the frequency tables for each code and produces as output + * a set of tables that map symbols to codewords and codeword lengths. */ +static void +lzx_make_huffman_codes(const struct lzx_freqs *freqs, + struct lzx_codes *codes, + unsigned num_main_syms) +{ + make_canonical_huffman_code(num_main_syms, + LZX_MAX_MAIN_CODEWORD_LEN, + freqs->main, + codes->lens.main, + codes->codewords.main); + + make_canonical_huffman_code(LZX_LENCODE_NUM_SYMBOLS, + LZX_MAX_LEN_CODEWORD_LEN, + freqs->len, + codes->lens.len, + codes->codewords.len); + + make_canonical_huffman_code(LZX_ALIGNEDCODE_NUM_SYMBOLS, + LZX_MAX_ALIGNED_CODEWORD_LEN, + freqs->aligned, + codes->lens.aligned, + codes->codewords.aligned); } /* - * Writes a compressed literal match to the output. + * Output a precomputed LZX match. * - * @out: The output bitstream. - * @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM) - * @match: The match, encoded as a 32-bit number. - * @codes: Pointer to a structure that contains the codewords for the - * main, length, and aligned offset Huffman codes. + * @out: + * The bitstream to which to write the match. + * @block_type: + * The type of the LZX block (LZX_BLOCKTYPE_ALIGNED or + * LZX_BLOCKTYPE_VERBATIM) + * @match: + * The match data. + * @codes: + * Pointer to a structure that contains the codewords for the main, length, + * and aligned offset Huffman codes for the current LZX compressed block. */ -static int +static void lzx_write_match(struct output_bitstream *out, int block_type, - u32 match, const struct lzx_codes *codes) + struct lzx_item match, const struct lzx_codes *codes) { /* low 8 bits are the match length minus 2 */ - unsigned match_len_minus_2 = match & 0xff; + unsigned match_len_minus_2 = match.data & 0xff; /* Next 17 bits are the position footer */ - unsigned position_footer = (match >> 8) & 0x1ffff; /* 17 bits */ + unsigned position_footer = (match.data >> 8) & 0x1ffff; /* 17 bits */ /* Next 6 bits are the position slot. */ - unsigned position_slot = (match >> 25) & 0x3f; /* 6 bits */ + unsigned position_slot = (match.data >> 25) & 0x3f; /* 6 bits */ unsigned len_header; unsigned len_footer; - unsigned len_pos_header; unsigned main_symbol; unsigned num_extra_bits; unsigned verbatim_bits; unsigned aligned_bits; - int ret; - /* If the match length is less than MIN_MATCH (= 2) + + /* If the match length is less than MIN_MATCH_LEN (= 2) + * NUM_PRIMARY_LENS (= 7), the length header contains - * the match length minus MIN_MATCH, and there is no + * the match length minus MIN_MATCH_LEN, and there is no * length footer. * * Otherwise, the length header contains * NUM_PRIMARY_LENS, and the length footer contains * the match length minus NUM_PRIMARY_LENS minus - * MIN_MATCH. */ + * MIN_MATCH_LEN. */ if (match_len_minus_2 < LZX_NUM_PRIMARY_LENS) { len_header = match_len_minus_2; - /* No length footer-- mark it with a special - * value. */ - len_footer = (unsigned)(-1); } else { len_header = LZX_NUM_PRIMARY_LENS; len_footer = match_len_minus_2 - LZX_NUM_PRIMARY_LENS; } - /* Combine the position slot with the length header into - * a single symbol that will be encoded with the main - * tree. */ - len_pos_header = (position_slot << 3) | len_header; - - /* The actual main symbol is offset by LZX_NUM_CHARS because - * values under LZX_NUM_CHARS are used to indicate a literal - * byte rather than a match. */ - main_symbol = len_pos_header + LZX_NUM_CHARS; + /* Combine the position slot with the length header into a single symbol + * that will be encoded with the main code. + * + * The actual main symbol is offset by LZX_NUM_CHARS because values + * under LZX_NUM_CHARS are used to indicate a literal byte rather than a + * match. */ + main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS; /* Output main symbol. */ - ret = bitstream_put_bits(out, codes->main_codewords[main_symbol], - codes->main_lens[main_symbol]); - if (ret != 0) - return ret; + bitstream_put_bits(out, codes->codewords.main[main_symbol], + codes->lens.main[main_symbol]); /* If there is a length footer, output it using the * length Huffman code. */ - if (len_footer != (unsigned)(-1)) { - ret = bitstream_put_bits(out, codes->len_codewords[len_footer], - codes->len_lens[len_footer]); - if (ret != 0) - return ret; - } - - wimlib_assert(position_slot < LZX_NUM_POSITION_SLOTS); + if (len_header == LZX_NUM_PRIMARY_LENS) + bitstream_put_bits(out, codes->codewords.len[len_footer], + codes->lens.len[len_footer]); num_extra_bits = lzx_get_num_extra_bits(position_slot); /* For aligned offset blocks with at least 3 extra bits, output the * verbatim bits literally, then the aligned bits encoded using the - * aligned offset tree. Otherwise, only the verbatim bits need to be + * aligned offset code. Otherwise, only the verbatim bits need to be * output. */ if ((block_type == LZX_BLOCKTYPE_ALIGNED) && (num_extra_bits >= 3)) { verbatim_bits = position_footer >> 3; - ret = bitstream_put_bits(out, verbatim_bits, - num_extra_bits - 3); - if (ret != 0) - return ret; + bitstream_put_bits(out, verbatim_bits, + num_extra_bits - 3); aligned_bits = (position_footer & 7); - ret = bitstream_put_bits(out, - codes->aligned_codewords[aligned_bits], - codes->aligned_lens[aligned_bits]); - if (ret != 0) - return ret; + bitstream_put_bits(out, + codes->codewords.aligned[aligned_bits], + codes->lens.aligned[aligned_bits]); } else { /* verbatim bits is the same as the position * footer, in this case. */ - ret = bitstream_put_bits(out, position_footer, num_extra_bits); - if (ret != 0) - return ret; + bitstream_put_bits(out, position_footer, num_extra_bits); } - return 0; } -/* - * Writes all compressed literals in a block, both matches and literal bytes, to - * the output bitstream. - * - * @out: The output bitstream. - * @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM) - * @match_tab[]: The array of matches that will be output. It has length - * of @num_compressed_literals. - * @num_compressed_literals: Number of compressed literals to be output. - * @codes: Pointer to a structure that contains the codewords for the - * main, length, and aligned offset Huffman codes. - */ -static int -lzx_write_compressed_literals(struct output_bitstream *ostream, - int block_type, - const u32 match_tab[], - unsigned num_compressed_literals, - const struct lzx_codes *codes) +/* Output an LZX literal (encoded with the main Huffman code). */ +static void +lzx_write_literal(struct output_bitstream *out, u8 literal, + const struct lzx_codes *codes) { - unsigned i; - u32 match; - int ret; - - for (i = 0; i < num_compressed_literals; i++) { - match = match_tab[i]; - - /* High bit of the match indicates whether the match is an - * actual match (1) or a literal uncompressed byte (0) */ - if (match & 0x80000000) { - /* match */ - ret = lzx_write_match(ostream, block_type, match, - codes); - if (ret != 0) - return ret; - } else { - /* literal byte */ - wimlib_assert(match < LZX_NUM_CHARS); - ret = bitstream_put_bits(ostream, - codes->main_codewords[match], - codes->main_lens[match]); - if (ret != 0) - return ret; - } - } - return 0; + bitstream_put_bits(out, + codes->codewords.main[literal], + codes->lens.main[literal]); } -/* - * Writes a compressed Huffman tree to the output, preceded by the pretree for - * it. - * - * The Huffman tree is represented in the output as a series of path lengths - * from which the canonical Huffman code can be reconstructed. The path lengths - * themselves are compressed using a separate Huffman code, the pretree, which - * consists of LZX_PRETREE_NUM_SYMBOLS (= 20) symbols that cover all possible code - * lengths, plus extra codes for repeated lengths. The path lengths of the - * pretree precede the path lengths of the larger code and are uncompressed, - * consisting of 20 entries of 4 bits each. - * - * @out: The bitstream for the compressed output. - * @lens: The code lengths for the Huffman tree, indexed by symbol. - * @num_symbols: The number of symbols in the code. - */ -static int -lzx_write_compressed_tree(struct output_bitstream *out, - const u8 lens[], unsigned num_symbols) -{ - /* Frequencies of the length symbols, including the RLE symbols (NOT the - * actual lengths themselves). */ - freq_t pretree_freqs[LZX_PRETREE_NUM_SYMBOLS]; - u8 pretree_lens[LZX_PRETREE_NUM_SYMBOLS]; - u16 pretree_codewords[LZX_PRETREE_NUM_SYMBOLS]; - u8 output_syms[num_symbols * 2]; - unsigned output_syms_idx; - unsigned cur_run_len; - unsigned i; - unsigned len_in_run; - unsigned additional_bits; - char delta; - u8 pretree_sym; - - ZERO_ARRAY(pretree_freqs); +static unsigned +lzx_build_precode(const u8 lens[restrict], + const u8 prev_lens[restrict], + const unsigned num_syms, + u32 precode_freqs[restrict LZX_PRECODE_NUM_SYMBOLS], + u8 output_syms[restrict num_syms], + u8 precode_lens[restrict LZX_PRECODE_NUM_SYMBOLS], + u32 precode_codewords[restrict LZX_PRECODE_NUM_SYMBOLS], + unsigned *num_additional_bits_ret) +{ + memset(precode_freqs, 0, + LZX_PRECODE_NUM_SYMBOLS * sizeof(precode_freqs[0])); /* Since the code word lengths use a form of RLE encoding, the goal here * is to find each run of identical lengths when going through them in @@ -429,16 +659,16 @@ lzx_write_compressed_tree(struct output_bitstream *out, * literally. * * output_syms[] will be filled in with the length symbols that will be - * output, including RLE codes, not yet encoded using the pre-tree. + * output, including RLE codes, not yet encoded using the precode. * * cur_run_len keeps track of how many code word lengths are in the - * current run of identical lengths. - */ - output_syms_idx = 0; - cur_run_len = 1; - for (i = 1; i <= num_symbols; i++) { + * current run of identical lengths. */ + unsigned output_syms_idx = 0; + unsigned cur_run_len = 1; + unsigned num_additional_bits = 0; + for (unsigned i = 1; i <= num_syms; i++) { - if (i != num_symbols && lens[i] == lens[i - 1]) { + if (i != num_syms && lens[i] == lens[i - 1]) { /* Still in a run--- keep going. */ cur_run_len++; continue; @@ -449,7 +679,7 @@ lzx_write_compressed_tree(struct output_bitstream *out, /* The symbol that was repeated in the run--- not to be confused * with the length *of* the run (cur_run_len) */ - len_in_run = lens[i - 1]; + unsigned len_in_run = lens[i - 1]; if (len_in_run == 0) { /* A run of 0's. Encode it in as few length @@ -459,9 +689,11 @@ lzx_write_compressed_tree(struct output_bitstream *out, * where n is an uncompressed literal 5-bit integer that * follows the magic length. */ while (cur_run_len >= 20) { + unsigned additional_bits; additional_bits = min(cur_run_len - 20, 0x1f); - pretree_freqs[18]++; + num_additional_bits += 5; + precode_freqs[18]++; output_syms[output_syms_idx++] = 18; output_syms[output_syms_idx++] = additional_bits; cur_run_len -= 20 + additional_bits; @@ -471,8 +703,11 @@ lzx_write_compressed_tree(struct output_bitstream *out, * where n is an uncompressed literal 4-bit integer that * follows the magic length. */ while (cur_run_len >= 4) { + unsigned additional_bits; + additional_bits = min(cur_run_len - 4, 0xf); - pretree_freqs[17]++; + num_additional_bits += 4; + precode_freqs[17]++; output_syms[output_syms_idx++] = 17; output_syms[output_syms_idx++] = additional_bits; cur_run_len -= 4 + additional_bits; @@ -486,19 +721,24 @@ lzx_write_compressed_tree(struct output_bitstream *out, * nonzeroes, where n is a literal bit that follows the * magic length, and where the value of the lengths in * the run is given by an extra length symbol, encoded - * with the pretree, that follows the literal bit. + * with the precode, that follows the literal bit. * * The extra length symbol is encoded as a difference * from the length of the codeword for the first symbol - * in the run in the previous tree. + * in the run in the previous code. * */ while (cur_run_len >= 4) { + unsigned additional_bits; + signed char delta; + additional_bits = (cur_run_len > 4); - delta = -(char)len_in_run; + num_additional_bits += 1; + delta = (signed char)prev_lens[i - cur_run_len] - + (signed char)len_in_run; if (delta < 0) delta += 17; - pretree_freqs[19]++; - pretree_freqs[(unsigned char)delta]++; + precode_freqs[19]++; + precode_freqs[(unsigned char)delta]++; output_syms[output_syms_idx++] = 19; output_syms[output_syms_idx++] = additional_bits; output_syms[output_syms_idx++] = delta; @@ -508,42 +748,101 @@ lzx_write_compressed_tree(struct output_bitstream *out, /* Any remaining lengths in the run are outputted without RLE, * as a difference from the length of that codeword in the - * previous tree. */ - while (cur_run_len--) { - delta = -(char)len_in_run; + * previous code. */ + while (cur_run_len > 0) { + signed char delta; + + delta = (signed char)prev_lens[i - cur_run_len] - + (signed char)len_in_run; if (delta < 0) delta += 17; - pretree_freqs[(unsigned char)delta]++; + precode_freqs[(unsigned char)delta]++; output_syms[output_syms_idx++] = delta; + cur_run_len--; } cur_run_len = 1; } - wimlib_assert(output_syms_idx < ARRAY_LEN(output_syms)); - - /* Build the pretree from the frequencies of the length symbols. */ - - make_canonical_huffman_code(LZX_PRETREE_NUM_SYMBOLS, - LZX_MAX_CODEWORD_LEN, - pretree_freqs, pretree_lens, - pretree_codewords); + /* Build the precode from the frequencies of the length symbols. */ - /* 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); + make_canonical_huffman_code(LZX_PRECODE_NUM_SYMBOLS, + LZX_MAX_PRE_CODEWORD_LEN, + precode_freqs, precode_lens, + precode_codewords); - /* Write the length symbols, encoded with the pretree, to the output. */ + *num_additional_bits_ret = num_additional_bits; - i = 0; - while (i < output_syms_idx) { - pretree_sym = output_syms[i++]; + return output_syms_idx; +} - bitstream_put_bits(out, pretree_codewords[pretree_sym], - pretree_lens[pretree_sym]); - switch (pretree_sym) { +/* + * 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. + * + * @out: + * 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_syms: + * The number of symbols in the Huffman code. + */ +static void +lzx_write_compressed_code(struct output_bitstream *out, + const u8 lens[restrict], + const u8 prev_lens[restrict], + unsigned num_syms) +{ + u32 precode_freqs[LZX_PRECODE_NUM_SYMBOLS]; + u8 output_syms[num_syms]; + u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS]; + u32 precode_codewords[LZX_PRECODE_NUM_SYMBOLS]; + unsigned i; + unsigned num_output_syms; + u8 precode_sym; + unsigned dummy; + + num_output_syms = lzx_build_precode(lens, + prev_lens, + num_syms, + precode_freqs, + output_syms, + precode_lens, + precode_codewords, + &dummy); + + /* Write the lengths of the precode codes to the output. */ + for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) + bitstream_put_bits(out, precode_lens[i], + LZX_PRECODE_ELEMENT_SIZE); + + /* Write the length symbols, encoded with the precode, to the output. */ + + for (i = 0; i < num_output_syms; ) { + precode_sym = output_syms[i++]; + + bitstream_put_bits(out, precode_codewords[precode_sym], + precode_lens[precode_sym]); + switch (precode_sym) { case 17: bitstream_put_bits(out, output_syms[i++], 4); break; @@ -553,219 +852,1522 @@ lzx_write_compressed_tree(struct output_bitstream *out, case 19: bitstream_put_bits(out, output_syms[i++], 1); bitstream_put_bits(out, - pretree_codewords[output_syms[i]], - pretree_lens[output_syms[i]]); + precode_codewords[output_syms[i]], + precode_lens[output_syms[i]]); i++; break; default: break; } } - return 0; } -/* Builds the canonical Huffman code for the main tree, the length tree, and the - * aligned offset tree. */ -static void -lzx_make_huffman_codes(const struct lzx_freq_tables *freq_tabs, - struct lzx_codes *codes) +/* + * Write all matches and literal bytes (which were precomputed) in an LZX + * compressed block to the output bitstream in the final compressed + * representation. + * + * @ostream + * 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 output_bitstream *ostream, int block_type, + const struct lzx_item items[], u32 num_items, + const struct lzx_codes *codes) +{ + for (u32 i = 0; i < num_items; i++) { + /* The high bit of the 32-bit intermediate representation + * indicates whether the item is an actual LZ-style match (1) or + * a literal byte (0). */ + if (items[i].data & 0x80000000) + lzx_write_match(ostream, block_type, items[i], codes); + else + lzx_write_literal(ostream, items[i].data, codes); + } +} + +static void +lzx_assert_codes_valid(const struct lzx_codes * codes, unsigned num_main_syms) +{ +#ifdef ENABLE_LZX_DEBUG + unsigned i; + + for (i = 0; i < num_main_syms; i++) + LZX_ASSERT(codes->lens.main[i] <= LZX_MAX_MAIN_CODEWORD_LEN); + + for (i = 0; i < LZX_LENCODE_NUM_SYMBOLS; i++) + LZX_ASSERT(codes->lens.len[i] <= LZX_MAX_LEN_CODEWORD_LEN); + + for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) + LZX_ASSERT(codes->lens.aligned[i] <= LZX_MAX_ALIGNED_CODEWORD_LEN); + + const unsigned tablebits = 10; + u16 decode_table[(1 << tablebits) + + (2 * max(num_main_syms, LZX_LENCODE_NUM_SYMBOLS))] + _aligned_attribute(DECODE_TABLE_ALIGNMENT); + LZX_ASSERT(0 == make_huffman_decode_table(decode_table, + num_main_syms, + min(tablebits, LZX_MAINCODE_TABLEBITS), + codes->lens.main, + LZX_MAX_MAIN_CODEWORD_LEN)); + LZX_ASSERT(0 == make_huffman_decode_table(decode_table, + LZX_LENCODE_NUM_SYMBOLS, + min(tablebits, LZX_LENCODE_TABLEBITS), + codes->lens.len, + LZX_MAX_LEN_CODEWORD_LEN)); + LZX_ASSERT(0 == make_huffman_decode_table(decode_table, + LZX_ALIGNEDCODE_NUM_SYMBOLS, + min(tablebits, LZX_ALIGNEDCODE_TABLEBITS), + codes->lens.aligned, + LZX_MAX_ALIGNED_CODEWORD_LEN)); +#endif /* ENABLE_LZX_DEBUG */ +} + +/* Write an LZX aligned offset or verbatim block to the output. */ +static void +lzx_write_compressed_block(int block_type, + unsigned block_size, + unsigned max_window_size, + unsigned num_main_syms, + struct lzx_item * chosen_items, + unsigned num_chosen_items, + const struct lzx_codes * codes, + const struct lzx_codes * prev_codes, + struct output_bitstream * ostream) +{ + unsigned i; + + LZX_ASSERT(block_type == LZX_BLOCKTYPE_ALIGNED || + block_type == LZX_BLOCKTYPE_VERBATIM); + lzx_assert_codes_valid(codes, num_main_syms); + + /* The first three bits indicate the type of block and are one of the + * LZX_BLOCKTYPE_* constants. */ + bitstream_put_bits(ostream, block_type, 3); + + /* Output the block size. + * + * The original LZX format seemed to always encode the block size in 3 + * bytes. However, the implementation in WIMGAPI, as used in WIM files, + * uses the first bit to indicate whether the block is the default size + * (32768) or a different size given explicitly by the next 16 bits. + * + * By default, this compressor uses a window size of 32768 and therefore + * follows the WIMGAPI behavior. However, this compressor also supports + * window sizes greater than 32768 bytes, which do not appear to be + * supported by WIMGAPI. In such cases, we retain the default size bit + * to mean a size of 32768 bytes but output non-default block size in 24 + * bits rather than 16. The compatibility of this behavior is unknown + * because WIMs created with chunk size greater than 32768 can seemingly + * only be opened by wimlib anyway. */ + if (block_size == LZX_DEFAULT_BLOCK_SIZE) { + bitstream_put_bits(ostream, 1, 1); + } else { + bitstream_put_bits(ostream, 0, 1); + + if (max_window_size >= 65536) + bitstream_put_bits(ostream, block_size >> 16, 8); + + bitstream_put_bits(ostream, block_size, 16); + } + + /* Write out lengths of the main code. Note that the LZX specification + * incorrectly states that the aligned offset code comes after the + * length code, but in fact it is the very first code to be written + * (before the main code). */ + if (block_type == LZX_BLOCKTYPE_ALIGNED) + for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) + bitstream_put_bits(ostream, codes->lens.aligned[i], + LZX_ALIGNEDCODE_ELEMENT_SIZE); + + LZX_DEBUG("Writing main code..."); + + /* Write the precode and lengths for the first LZX_NUM_CHARS symbols in + * the main code, which are the codewords for literal bytes. */ + lzx_write_compressed_code(ostream, + codes->lens.main, + prev_codes->lens.main, + LZX_NUM_CHARS); + + /* Write the precode and lengths for the rest of the main code, which + * are the codewords for match headers. */ + lzx_write_compressed_code(ostream, + codes->lens.main + LZX_NUM_CHARS, + prev_codes->lens.main + LZX_NUM_CHARS, + num_main_syms - LZX_NUM_CHARS); + + LZX_DEBUG("Writing length code..."); + + /* Write the precode and lengths for the length code. */ + lzx_write_compressed_code(ostream, + codes->lens.len, + prev_codes->lens.len, + LZX_LENCODE_NUM_SYMBOLS); + + LZX_DEBUG("Writing matches and literals..."); + + /* Write the actual matches and literals. */ + lzx_write_items(ostream, block_type, + chosen_items, num_chosen_items, codes); + + LZX_DEBUG("Done writing block."); +} + +/* Write out the LZX blocks that were computed. */ +static void +lzx_write_all_blocks(struct lzx_compressor *ctx, struct output_bitstream *ostream) +{ + + const struct lzx_codes *prev_codes = &ctx->zero_codes; + for (unsigned i = 0; i < ctx->num_blocks; i++) { + const struct lzx_block_spec *spec = &ctx->block_specs[i]; + + LZX_DEBUG("Writing block %u/%u (type=%d, size=%u, num_chosen_items=%u)...", + i + 1, ctx->num_blocks, + spec->block_type, spec->block_size, + spec->num_chosen_items); + + lzx_write_compressed_block(spec->block_type, + spec->block_size, + ctx->max_window_size, + ctx->num_main_syms, + spec->chosen_items, + spec->num_chosen_items, + &spec->codes, + prev_codes, + ostream); + + prev_codes = &spec->codes; + } +} + +/* Constructs an LZX match from a literal byte and updates the main code symbol + * frequencies. */ +static inline u32 +lzx_tally_literal(u8 lit, struct lzx_freqs *freqs) +{ + freqs->main[lit]++; + return (u32)lit; +} + +/* Constructs an LZX match from an offset and a length, and updates the LRU + * queue and the frequency of symbols in the main, length, and aligned offset + * alphabets. The return value is a 32-bit number that provides the match in an + * intermediate representation documented below. */ +static inline u32 +lzx_tally_match(unsigned match_len, u32 match_offset, + struct lzx_freqs *freqs, struct lzx_lru_queue *queue) +{ + unsigned position_slot; + unsigned position_footer; + u32 len_header; + unsigned main_symbol; + unsigned len_footer; + unsigned adjusted_match_len; + + LZX_ASSERT(match_len >= LZX_MIN_MATCH_LEN && match_len <= LZX_MAX_MATCH_LEN); + + /* The match offset shall be encoded as a position slot (itself encoded + * as part of the main symbol) and a position footer. */ + position_slot = lzx_get_position_slot(match_offset, queue); + position_footer = (match_offset + LZX_OFFSET_OFFSET) & + ((1U << lzx_get_num_extra_bits(position_slot)) - 1); + + /* The match length shall be encoded as a length header (itself encoded + * as part of the main symbol) and an optional length footer. */ + adjusted_match_len = match_len - LZX_MIN_MATCH_LEN; + if (adjusted_match_len < LZX_NUM_PRIMARY_LENS) { + /* No length footer needed. */ + len_header = adjusted_match_len; + } else { + /* Length footer needed. It will be encoded using the length + * code. */ + len_header = LZX_NUM_PRIMARY_LENS; + len_footer = adjusted_match_len - LZX_NUM_PRIMARY_LENS; + freqs->len[len_footer]++; + } + + /* Account for the main symbol. */ + main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS; + + freqs->main[main_symbol]++; + + /* In an aligned offset block, 3 bits of the position footer are output + * as an aligned offset symbol. Account for this, although we may + * ultimately decide to output the block as verbatim. */ + + /* The following check is equivalent to: + * + * if (lzx_extra_bits[position_slot] >= 3) + * + * Note that this correctly excludes position slots that correspond to + * recent offsets. */ + if (position_slot >= 8) + freqs->aligned[position_footer & 7]++; + + /* Pack the position slot, position footer, and match length into an + * intermediate representation. See `struct lzx_item' for details. + */ + LZX_ASSERT(LZX_MAX_POSITION_SLOTS <= 64); + LZX_ASSERT(lzx_get_num_extra_bits(LZX_MAX_POSITION_SLOTS - 1) <= 17); + LZX_ASSERT(LZX_MAX_MATCH_LEN - LZX_MIN_MATCH_LEN + 1 <= 256); + + LZX_ASSERT(position_slot <= (1U << (31 - 25)) - 1); + LZX_ASSERT(position_footer <= (1U << (25 - 8)) - 1); + LZX_ASSERT(adjusted_match_len <= (1U << (8 - 0)) - 1); + return 0x80000000 | + (position_slot << 25) | + (position_footer << 8) | + (adjusted_match_len); +} + +struct lzx_record_ctx { + struct lzx_freqs freqs; + struct lzx_lru_queue queue; + struct lzx_item *matches; +}; + +static void +lzx_record_match(unsigned len, unsigned offset, void *_ctx) +{ + struct lzx_record_ctx *ctx = _ctx; + + (ctx->matches++)->data = lzx_tally_match(len, offset, &ctx->freqs, &ctx->queue); +} + +static void +lzx_record_literal(u8 lit, void *_ctx) +{ + struct lzx_record_ctx *ctx = _ctx; + + (ctx->matches++)->data = lzx_tally_literal(lit, &ctx->freqs); +} + +/* Returns the cost, in bits, to output a literal byte using the specified cost + * model. */ +static u32 +lzx_literal_cost(u8 c, const struct lzx_costs * costs) +{ + return costs->main[c]; +} + +/* Given a (length, offset) pair that could be turned into a valid LZX match as + * well as costs for the codewords in the main, length, and aligned Huffman + * codes, return the approximate number of bits it will take to represent this + * match in the compressed output. Take into account the match offset LRU + * queue and also updates it. */ +static u32 +lzx_match_cost(unsigned length, u32 offset, const struct lzx_costs *costs, + struct lzx_lru_queue *queue) { - make_canonical_huffman_code(LZX_MAINTREE_NUM_SYMBOLS, - LZX_MAX_CODEWORD_LEN, - freq_tabs->main_freq_table, - codes->main_lens, - codes->main_codewords); + unsigned position_slot; + unsigned len_header, main_symbol; + unsigned num_extra_bits; + u32 cost = 0; + + position_slot = lzx_get_position_slot(offset, queue); + + len_header = min(length - LZX_MIN_MATCH_LEN, LZX_NUM_PRIMARY_LENS); + main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS; + + /* Account for main symbol. */ + cost += costs->main[main_symbol]; + + /* Account for extra position information. */ + num_extra_bits = lzx_get_num_extra_bits(position_slot); + if (num_extra_bits >= 3) { + cost += num_extra_bits - 3; + cost += costs->aligned[(offset + LZX_OFFSET_OFFSET) & 7]; + } else { + cost += num_extra_bits; + } + + /* Account for extra length information. */ + if (len_header == LZX_NUM_PRIMARY_LENS) + cost += costs->len[length - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS]; - make_canonical_huffman_code(LZX_LENTREE_NUM_SYMBOLS, - LZX_MAX_CODEWORD_LEN, - freq_tabs->len_freq_table, - codes->len_lens, - codes->len_codewords); + return cost; - make_canonical_huffman_code(LZX_ALIGNEDTREE_NUM_SYMBOLS, 8, - freq_tabs->aligned_freq_table, - codes->aligned_lens, - codes->aligned_codewords); } +/* Set the cost model @ctx->costs from the Huffman codeword lengths specified in + * @lens. + * + * The cost model and codeword lengths are almost the same thing, but the + * Huffman codewords with length 0 correspond to symbols with zero frequency + * that still need to be assigned actual costs. The specific values assigned + * are arbitrary, but they should be fairly high (near the maximum codeword + * length) to take into account the fact that uses of these symbols are expected + * to be rare. */ static void -do_call_insn_translation(u32 *call_insn_target, int input_pos, - int32_t file_size) +lzx_set_costs(struct lzx_compressor * ctx, const struct lzx_lens * lens) +{ + unsigned i; + unsigned num_main_syms = ctx->num_main_syms; + + /* Main code */ + for (i = 0; i < num_main_syms; i++) { + ctx->costs.main[i] = lens->main[i]; + if (ctx->costs.main[i] == 0) + ctx->costs.main[i] = ctx->params.alg_params.slow.main_nostat_cost; + } + + /* Length code */ + for (i = 0; i < LZX_LENCODE_NUM_SYMBOLS; i++) { + ctx->costs.len[i] = lens->len[i]; + if (ctx->costs.len[i] == 0) + ctx->costs.len[i] = ctx->params.alg_params.slow.len_nostat_cost; + } + + /* Aligned offset code */ + for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) { + ctx->costs.aligned[i] = lens->aligned[i]; + if (ctx->costs.aligned[i] == 0) + ctx->costs.aligned[i] = ctx->params.alg_params.slow.aligned_nostat_cost; + } +} + +/* Retrieve a list of matches available at the next position in the input. + * + * A pointer to the matches array is written into @matches_ret, and the return + * value is the number of matches found. */ +static unsigned +lzx_get_matches(struct lzx_compressor *ctx, + const struct lz_match **matches_ret) { - int32_t abs_offset; - int32_t rel_offset; + struct lz_match *cache_ptr; + struct lz_match *matches; + unsigned num_matches; + + LZX_ASSERT(ctx->match_window_pos < ctx->match_window_end); + + cache_ptr = ctx->cache_ptr; + matches = cache_ptr + 1; + if (likely(cache_ptr <= ctx->cache_limit)) { + if (ctx->matches_cached) { + num_matches = cache_ptr->len; + } else { + num_matches = lz_bt_get_matches(&ctx->mf, matches); + cache_ptr->len = num_matches; + } + } else { + num_matches = 0; + } + + /* Don't allow matches to span the end of an LZX block. */ + if (ctx->match_window_end < ctx->window_size && num_matches != 0) { + unsigned limit = ctx->match_window_end - ctx->match_window_pos; + + if (limit >= LZX_MIN_MATCH_LEN) { + + unsigned i = num_matches - 1; + do { + if (matches[i].len >= limit) { + matches[i].len = limit; - 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; + /* Truncation might produce multiple + * matches with length 'limit'. Keep at + * most 1. */ + num_matches = i + 1; + } + } while (i--); } else { - /* "compensating translation" */ - abs_offset = rel_offset - file_size; + num_matches = 0; } - *call_insn_target = cpu_to_le32(abs_offset); + cache_ptr->len = num_matches; } + +#if 0 + fprintf(stderr, "Pos %u/%u: %u matches\n", + ctx->match_window_pos, ctx->window_size, num_matches); + for (unsigned i = 0; i < num_matches; i++) + fprintf(stderr, "\tLen %u Offset %u\n", matches[i].len, matches[i].offset); +#endif + +#ifdef ENABLE_LZX_DEBUG + for (unsigned i = 0; i < num_matches; i++) { + LZX_ASSERT(matches[i].len >= LZX_MIN_MATCH_LEN); + LZX_ASSERT(matches[i].len <= LZX_MAX_MATCH_LEN); + LZX_ASSERT(matches[i].len <= ctx->match_window_end - ctx->match_window_pos); + LZX_ASSERT(matches[i].offset > 0); + LZX_ASSERT(matches[i].offset <= ctx->match_window_pos); + LZX_ASSERT(!memcmp(&ctx->window[ctx->match_window_pos], + &ctx->window[ctx->match_window_pos - matches[i].offset], + matches[i].len)); + if (i) { + LZX_ASSERT(matches[i].len > matches[i - 1].len); + LZX_ASSERT(matches[i].offset > matches[i - 1].offset); + } + } +#endif + ctx->match_window_pos++; + ctx->cache_ptr = matches + num_matches; + *matches_ret = matches; + return num_matches; } -/* This is the reverse of undo_call_insn_preprocessing() in lzx-decompress.c. - * See the comment above that function for more information. */ static void -do_call_insn_preprocessing(u8 uncompressed_data[], int uncompressed_data_len) -{ - for (int i = 0; i < uncompressed_data_len - 10; i++) { - if (uncompressed_data[i] == 0xe8) { - do_call_insn_translation((u32*)&uncompressed_data[i + 1], - i, - LZX_WIM_MAGIC_FILESIZE); - i += 4; +lzx_skip_bytes(struct lzx_compressor *ctx, unsigned n) +{ + struct lz_match *cache_ptr; + + LZX_ASSERT(n <= ctx->match_window_end - ctx->match_window_pos); + + cache_ptr = ctx->cache_ptr; + ctx->match_window_pos += n; + if (ctx->matches_cached) { + while (n-- && cache_ptr <= ctx->cache_limit) + cache_ptr += 1 + cache_ptr->len; + } else { + lz_bt_skip_positions(&ctx->mf, n); + while (n-- && cache_ptr <= ctx->cache_limit) { + cache_ptr->len = 0; + cache_ptr += 1; } } + ctx->cache_ptr = cache_ptr; } +/* + * Reverse the linked list of near-optimal matches so that they can be returned + * in forwards order. + * + * Returns the first match in the list. + */ +static struct lz_match +lzx_match_chooser_reverse_list(struct lzx_compressor *ctx, unsigned cur_pos) +{ + unsigned prev_link, saved_prev_link; + unsigned prev_match_offset, saved_prev_match_offset; -static const struct lz_params lzx_lz_params = { + ctx->optimum_end_idx = cur_pos; - /* LZX_MIN_MATCH == 2, but 2-character matches are rarely useful; the - * minimum match for compression is set to 3 instead. */ - .min_match = 3, + saved_prev_link = ctx->optimum[cur_pos].prev.link; + saved_prev_match_offset = ctx->optimum[cur_pos].prev.match_offset; - .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, -}; + do { + prev_link = saved_prev_link; + prev_match_offset = saved_prev_match_offset; + + saved_prev_link = ctx->optimum[prev_link].prev.link; + saved_prev_match_offset = ctx->optimum[prev_link].prev.match_offset; + + ctx->optimum[prev_link].next.link = cur_pos; + ctx->optimum[prev_link].next.match_offset = prev_match_offset; + + cur_pos = prev_link; + } while (cur_pos != 0); + + ctx->optimum_cur_idx = ctx->optimum[0].next.link; + + return (struct lz_match) + { .len = ctx->optimum_cur_idx, + .offset = ctx->optimum[0].next.match_offset, + }; +} /* - * Performs LZX compression on a block of data. + * lzx_get_near_optimal_match() - + * + * Choose an approximately optimal match or literal to use at the next position + * in the string, or "window", being LZ-encoded. + * + * This is based on algorithms used in 7-Zip, including the DEFLATE encoder + * and the LZMA encoder, written by Igor Pavlov. + * + * Unlike a greedy parser that always takes the longest match, or even a "lazy" + * parser with one match/literal look-ahead like zlib, the algorithm used here + * may look ahead many matches/literals to determine the approximately optimal + * match/literal to code next. The motivation is that the compression ratio is + * improved if the compressor can do things like use a shorter-than-possible + * match in order to allow a longer match later, and also take into account the + * estimated real cost of coding each match/literal based on the underlying + * entropy encoding. + * + * Still, this is not a true optimal parser for several reasons: + * + * - Real compression formats use entropy encoding of the literal/match + * sequence, so the real cost of coding each match or literal is unknown until + * the parse is fully determined. It can be approximated based on iterative + * parses, but the end result is not guaranteed to be globally optimal. + * + * - Very long matches are chosen immediately. This is because locations with + * long matches are likely to have many possible alternatives that would cause + * slow optimal parsing, but also such locations are already highly + * compressible so it is not too harmful to just grab the longest match. + * + * - Not all possible matches at each location are considered because the + * underlying match-finder limits the number and type of matches produced at + * each position. For example, for a given match length it's usually not + * worth it to only consider matches other than the lowest-offset match, + * except in the case of a repeat offset. + * + * - Although we take into account the adaptive state (in LZX, the recent offset + * queue), coding decisions made with respect to the adaptive state will be + * locally optimal but will not necessarily be globally optimal. This is + * because the algorithm only keeps the least-costly path to get to a given + * location and does not take into account that a slightly more costly path + * could result in a different adaptive state that ultimately results in a + * lower global cost. + * + * - The array space used by this function is bounded, so in degenerate cases it + * is forced to start returning matches/literals before the algorithm has + * really finished. * - * Please see the documentation for the 'compress_func_t' type in write.c for - * the exact behavior of this function and how to call it. + * Each call to this function does one of two things: + * + * 1. Build a sequence of near-optimal matches/literals, up to some point, that + * will be returned by subsequent calls to this function, then return the + * first one. + * + * OR + * + * 2. Return the next match/literal previously computed by a call to this + * function. + * + * The return value is a (length, offset) pair specifying the match or literal + * chosen. For literals, the length is 0 or 1 and the offset is meaningless. */ -unsigned -lzx_compress(const void *__uncompressed_data, unsigned uncompressed_len, - void *compressed_data) +static struct lz_match +lzx_get_near_optimal_match(struct lzx_compressor *ctx) { - 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; + const struct lz_match *matches; + struct lz_match match; + unsigned longest_len; + unsigned longest_rep_len; + u32 longest_rep_offset; + unsigned cur_pos; + unsigned end_pos; + + if (ctx->optimum_cur_idx != ctx->optimum_end_idx) { + /* Case 2: Return the next match/literal already found. */ + match.len = ctx->optimum[ctx->optimum_cur_idx].next.link - + ctx->optimum_cur_idx; + match.offset = ctx->optimum[ctx->optimum_cur_idx].next.match_offset; + + ctx->optimum_cur_idx = ctx->optimum[ctx->optimum_cur_idx].next.link; + return match; + } + + /* Case 1: Compute a new list of matches/literals to return. */ + + ctx->optimum_cur_idx = 0; + ctx->optimum_end_idx = 0; + + /* Search for matches at recent offsets. Only keep the one with the + * longest match length. */ + longest_rep_len = LZX_MIN_MATCH_LEN - 1; + if (ctx->match_window_pos >= 1) { + unsigned limit = min(LZX_MAX_MATCH_LEN, + ctx->match_window_end - ctx->match_window_pos); + for (int i = 0; i < LZX_NUM_RECENT_OFFSETS; i++) { + u32 offset = ctx->queue.R[i]; + const u8 *strptr = &ctx->window[ctx->match_window_pos]; + const u8 *matchptr = strptr - offset; + unsigned len = 0; + while (len < limit && strptr[len] == matchptr[len]) + len++; + if (len > longest_rep_len) { + longest_rep_len = len; + longest_rep_offset = offset; + } + } + } + + /* If there's a long match with a recent offset, take it. */ + if (longest_rep_len >= ctx->params.alg_params.slow.nice_match_length) { + lzx_skip_bytes(ctx, longest_rep_len); + return (struct lz_match) { + .len = longest_rep_len, + .offset = longest_rep_offset, + }; + } + + /* Search other matches. */ + num_matches = lzx_get_matches(ctx, &matches); + + /* If there's a long match, take it. */ + if (num_matches) { + longest_len = matches[num_matches - 1].len; + if (longest_len >= ctx->params.alg_params.slow.nice_match_length) { + lzx_skip_bytes(ctx, longest_len - 1); + return matches[num_matches - 1]; + } + } else { + longest_len = 1; + } + + /* Calculate the cost to reach the next position by coding a literal. + */ + ctx->optimum[1].queue = ctx->queue; + ctx->optimum[1].cost = lzx_literal_cost(ctx->window[ctx->match_window_pos - 1], + &ctx->costs); + ctx->optimum[1].prev.link = 0; + + /* Calculate the cost to reach any position up to and including that + * reached by the longest match. + * + * Note: We consider only the lowest-offset match that reaches each + * position. + * + * Note: Some of the cost calculation stays the same for each offset, + * regardless of how many lengths it gets used for. Therefore, to + * improve performance, we hand-code the cost calculation instead of + * calling lzx_match_cost() to do a from-scratch cost evaluation at each + * length. */ + for (unsigned i = 0, len = 2; i < num_matches; i++) { + u32 offset; + struct lzx_lru_queue queue; + u32 position_cost; + unsigned position_slot; + unsigned num_extra_bits; + + offset = matches[i].offset; + queue = ctx->queue; + position_cost = 0; + + position_slot = lzx_get_position_slot(offset, &queue); + num_extra_bits = lzx_get_num_extra_bits(position_slot); + if (num_extra_bits >= 3) { + position_cost += num_extra_bits - 3; + position_cost += ctx->costs.aligned[(offset + LZX_OFFSET_OFFSET) & 7]; + } else { + position_cost += num_extra_bits; + } + + do { + unsigned len_header; + unsigned main_symbol; + u32 cost; + + cost = position_cost; + + len_header = min(len - LZX_MIN_MATCH_LEN, LZX_NUM_PRIMARY_LENS); + main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS; + cost += ctx->costs.main[main_symbol]; + if (len_header == LZX_NUM_PRIMARY_LENS) + cost += ctx->costs.len[len - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS]; + + ctx->optimum[len].queue = queue; + ctx->optimum[len].prev.link = 0; + ctx->optimum[len].prev.match_offset = offset; + ctx->optimum[len].cost = cost; + } while (++len <= matches[i].len); + } + end_pos = longest_len; + + if (longest_rep_len >= LZX_MIN_MATCH_LEN) { + struct lzx_lru_queue queue; + u32 cost; + + while (end_pos < longest_rep_len) + ctx->optimum[++end_pos].cost = MC_INFINITE_COST; + + queue = ctx->queue; + cost = lzx_match_cost(longest_rep_len, longest_rep_offset, + &ctx->costs, &queue); + if (cost <= ctx->optimum[longest_rep_len].cost) { + ctx->optimum[longest_rep_len].queue = queue; + ctx->optimum[longest_rep_len].prev.link = 0; + ctx->optimum[longest_rep_len].prev.match_offset = longest_rep_offset; + ctx->optimum[longest_rep_len].cost = cost; + } + } + + /* Step forward, calculating the estimated minimum cost to reach each + * position. The algorithm may find multiple paths to reach each + * position; only the lowest-cost path is saved. + * + * The progress of the parse is tracked in the @ctx->optimum array, which + * for each position contains the minimum cost to reach that position, + * the index of the start of the match/literal taken to reach that + * position through the minimum-cost path, the offset of the match taken + * (not relevant for literals), and the adaptive state that will exist + * at that position after the minimum-cost path is taken. The @cur_pos + * variable stores the position at which the algorithm is currently + * considering coding choices, and the @end_pos variable stores the + * greatest position at which the costs of coding choices have been + * saved. (Actually, the algorithm guarantees that all positions up to + * and including @end_pos are reachable by at least one path.) + * + * The loop terminates when any one of the following conditions occurs: + * + * 1. A match with length greater than or equal to @nice_match_length is + * found. When this occurs, the algorithm chooses this match + * unconditionally, and consequently the near-optimal match/literal + * sequence up to and including that match is fully determined and it + * can begin returning the match/literal list. + * + * 2. @cur_pos reaches a position not overlapped by a preceding match. + * In such cases, the near-optimal match/literal sequence up to + * @cur_pos is fully determined and it can begin returning the + * match/literal list. + * + * 3. Failing either of the above in a degenerate case, the loop + * terminates when space in the @ctx->optimum array is exhausted. + * This terminates the algorithm and forces it to start returning + * matches/literals even though they may not be globally optimal. + * + * Upon loop termination, a nonempty list of matches/literals will have + * been produced and stored in the @optimum array. These + * matches/literals are linked in reverse order, so the last thing this + * function does is reverse this list and return the first + * match/literal, leaving the rest to be returned immediately by + * subsequent calls to this function. + */ + cur_pos = 0; + for (;;) { + u32 cost; + + /* Advance to next position. */ + cur_pos++; + + /* Check termination conditions (2) and (3) noted above. */ + if (cur_pos == end_pos || cur_pos == LZX_OPTIM_ARRAY_SIZE) + return lzx_match_chooser_reverse_list(ctx, cur_pos); + + /* Search for matches at recent offsets. */ + longest_rep_len = LZX_MIN_MATCH_LEN - 1; + unsigned limit = min(LZX_MAX_MATCH_LEN, + ctx->match_window_end - ctx->match_window_pos); + for (int i = 0; i < LZX_NUM_RECENT_OFFSETS; i++) { + u32 offset = ctx->optimum[cur_pos].queue.R[i]; + const u8 *strptr = &ctx->window[ctx->match_window_pos]; + const u8 *matchptr = strptr - offset; + unsigned len = 0; + while (len < limit && strptr[len] == matchptr[len]) + len++; + if (len > longest_rep_len) { + longest_rep_len = len; + longest_rep_offset = offset; + } + } + + /* If we found a long match at a recent offset, choose it + * immediately. */ + if (longest_rep_len >= ctx->params.alg_params.slow.nice_match_length) { + /* Build the list of matches to return and get + * the first one. */ + match = lzx_match_chooser_reverse_list(ctx, cur_pos); + + /* Append the long match to the end of the list. */ + ctx->optimum[cur_pos].next.match_offset = longest_rep_offset; + ctx->optimum[cur_pos].next.link = cur_pos + longest_rep_len; + ctx->optimum_end_idx = cur_pos + longest_rep_len; + + /* Skip over the remaining bytes of the long match. */ + lzx_skip_bytes(ctx, longest_rep_len); + + /* Return first match in the list. */ + return match; + } + + /* Search other matches. */ + num_matches = lzx_get_matches(ctx, &matches); + + /* If there's a long match, take it. */ + if (num_matches) { + longest_len = matches[num_matches - 1].len; + if (longest_len >= ctx->params.alg_params.slow.nice_match_length) { + /* Build the list of matches to return and get + * the first one. */ + match = lzx_match_chooser_reverse_list(ctx, cur_pos); + + /* Append the long match to the end of the list. */ + ctx->optimum[cur_pos].next.match_offset = + matches[num_matches - 1].offset; + ctx->optimum[cur_pos].next.link = cur_pos + longest_len; + ctx->optimum_end_idx = cur_pos + longest_len; + + /* Skip over the remaining bytes of the long match. */ + lzx_skip_bytes(ctx, longest_len - 1); + + /* Return first match in the list. */ + return match; + } + } else { + longest_len = 1; + } + + while (end_pos < cur_pos + longest_len) + ctx->optimum[++end_pos].cost = MC_INFINITE_COST; + + /* Consider coding a literal. */ + cost = ctx->optimum[cur_pos].cost + + lzx_literal_cost(ctx->window[ctx->match_window_pos - 1], + &ctx->costs); + if (cost < ctx->optimum[cur_pos + 1].cost) { + ctx->optimum[cur_pos + 1].queue = ctx->optimum[cur_pos].queue; + ctx->optimum[cur_pos + 1].cost = cost; + ctx->optimum[cur_pos + 1].prev.link = cur_pos; + } + + /* Consider coding a match. + * + * The hard-coded cost calculation is done for the same reason + * stated in the comment for the similar loop earlier. + * Actually, it is *this* one that has the biggest effect on + * performance; overall LZX compression is > 10% faster with + * this code compared to calling lzx_match_cost() with each + * length. */ + for (unsigned i = 0, len = 2; i < num_matches; i++) { + u32 offset; + struct lzx_lru_queue queue; + u32 position_cost; + unsigned position_slot; + unsigned num_extra_bits; + + offset = matches[i].offset; + queue = ctx->optimum[cur_pos].queue; + position_cost = ctx->optimum[cur_pos].cost; + + position_slot = lzx_get_position_slot(offset, &queue); + num_extra_bits = lzx_get_num_extra_bits(position_slot); + if (num_extra_bits >= 3) { + position_cost += num_extra_bits - 3; + position_cost += ctx->costs.aligned[ + (offset + LZX_OFFSET_OFFSET) & 7]; + } else { + position_cost += num_extra_bits; + } + + do { + unsigned len_header; + unsigned main_symbol; + u32 cost; + + cost = position_cost; + + len_header = min(len - LZX_MIN_MATCH_LEN, + LZX_NUM_PRIMARY_LENS); + main_symbol = ((position_slot << 3) | len_header) + + LZX_NUM_CHARS; + cost += ctx->costs.main[main_symbol]; + if (len_header == LZX_NUM_PRIMARY_LENS) { + cost += ctx->costs.len[len - + LZX_MIN_MATCH_LEN - + LZX_NUM_PRIMARY_LENS]; + } + if (cost < ctx->optimum[cur_pos + len].cost) { + ctx->optimum[cur_pos + len].queue = queue; + ctx->optimum[cur_pos + len].prev.link = cur_pos; + ctx->optimum[cur_pos + len].prev.match_offset = offset; + ctx->optimum[cur_pos + len].cost = cost; + } + } while (++len <= matches[i].len); + } + + if (longest_rep_len >= LZX_MIN_MATCH_LEN) { + struct lzx_lru_queue queue; + + while (end_pos < cur_pos + longest_rep_len) + ctx->optimum[++end_pos].cost = MC_INFINITE_COST; + + queue = ctx->optimum[cur_pos].queue; + + cost = ctx->optimum[cur_pos].cost + + lzx_match_cost(longest_rep_len, longest_rep_offset, + &ctx->costs, &queue); + if (cost <= ctx->optimum[cur_pos + longest_rep_len].cost) { + ctx->optimum[cur_pos + longest_rep_len].queue = + queue; + ctx->optimum[cur_pos + longest_rep_len].prev.link = + cur_pos; + ctx->optimum[cur_pos + longest_rep_len].prev.match_offset = + longest_rep_offset; + ctx->optimum[cur_pos + longest_rep_len].cost = + cost; + } + } + } +} + +/* Set default symbol costs for the LZX Huffman codes. */ +static void +lzx_set_default_costs(struct lzx_costs * costs, unsigned num_main_syms) +{ unsigned i; - int ret; - int block_type = LZX_BLOCKTYPE_ALIGNED; - wimlib_assert(uncompressed_len <= 32768); + /* Main code (part 1): Literal symbols */ + for (i = 0; i < LZX_NUM_CHARS; i++) + costs->main[i] = 8; + + /* Main code (part 2): Match header symbols */ + for (; i < num_main_syms; i++) + costs->main[i] = 10; + + /* Length code */ + for (i = 0; i < LZX_LENCODE_NUM_SYMBOLS; i++) + costs->len[i] = 8; + + /* Aligned offset code */ + for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) + costs->aligned[i] = 3; +} + +/* 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) +{ + unsigned aligned_cost = 0; + unsigned verbatim_cost = 0; + + /* Verbatim blocks have a constant 3 bits per position footer. Aligned + * offset blocks have an aligned offset symbol per position footer, plus + * an extra 24 bits per block to output the lengths necessary to + * reconstruct the aligned offset code itself. */ + for (unsigned i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) { + verbatim_cost += 3 * freqs->aligned[i]; + aligned_cost += codes->lens.aligned[i] * freqs->aligned[i]; + } + aligned_cost += LZX_ALIGNEDCODE_ELEMENT_SIZE * LZX_ALIGNEDCODE_NUM_SYMBOLS; + if (aligned_cost < verbatim_cost) + return LZX_BLOCKTYPE_ALIGNED; + else + return LZX_BLOCKTYPE_VERBATIM; +} + +/* Find a near-optimal sequence of matches/literals with which to output the + * specified LZX block, then set the block's type to that which has the minimum + * cost to output (either verbatim or aligned). */ +static void +lzx_optimize_block(struct lzx_compressor *ctx, struct lzx_block_spec *spec, + unsigned num_passes) +{ + const struct lzx_lru_queue orig_queue = ctx->queue; + unsigned num_passes_remaining = num_passes; + struct lzx_freqs freqs; + const u8 *window_ptr; + const u8 *window_end; + struct lzx_item *next_chosen_match; + struct lz_match lz_match; + struct lzx_item lzx_item; + + LZX_ASSERT(num_passes >= 1); + LZX_ASSERT(lz_bt_get_position(&ctx->mf) == spec->window_pos); + + ctx->match_window_end = spec->window_pos + spec->block_size; + ctx->matches_cached = false; + + /* The first optimal parsing pass is done using the cost model already + * set in ctx->costs. Each later pass is done using a cost model + * computed from the previous pass. + * + * To improve performance we only generate the array containing the + * matches and literals in intermediate form on the final pass. */ + + while (--num_passes_remaining) { + ctx->match_window_pos = spec->window_pos; + ctx->cache_ptr = ctx->cached_matches; + memset(&freqs, 0, sizeof(freqs)); + window_ptr = &ctx->window[spec->window_pos]; + window_end = window_ptr + spec->block_size; + + while (window_ptr != window_end) { + + lz_match = lzx_get_near_optimal_match(ctx); + + LZX_ASSERT(!(lz_match.len == LZX_MIN_MATCH_LEN && + lz_match.offset == ctx->max_window_size - + LZX_MIN_MATCH_LEN)); + if (lz_match.len >= LZX_MIN_MATCH_LEN) { + lzx_tally_match(lz_match.len, lz_match.offset, + &freqs, &ctx->queue); + window_ptr += lz_match.len; + } else { + lzx_tally_literal(*window_ptr, &freqs); + window_ptr += 1; + } + } + lzx_make_huffman_codes(&freqs, &spec->codes, ctx->num_main_syms); + lzx_set_costs(ctx, &spec->codes.lens); + ctx->queue = orig_queue; + ctx->matches_cached = true; + } + + ctx->match_window_pos = spec->window_pos; + ctx->cache_ptr = ctx->cached_matches; + memset(&freqs, 0, sizeof(freqs)); + window_ptr = &ctx->window[spec->window_pos]; + window_end = window_ptr + spec->block_size; + + spec->chosen_items = &ctx->chosen_items[spec->window_pos]; + next_chosen_match = spec->chosen_items; + + while (window_ptr != window_end) { + lz_match = lzx_get_near_optimal_match(ctx); + + LZX_ASSERT(!(lz_match.len == LZX_MIN_MATCH_LEN && + lz_match.offset == ctx->max_window_size - + LZX_MIN_MATCH_LEN)); + if (lz_match.len >= LZX_MIN_MATCH_LEN) { + lzx_item.data = lzx_tally_match(lz_match.len, + lz_match.offset, + &freqs, &ctx->queue); + window_ptr += lz_match.len; + } else { + lzx_item.data = lzx_tally_literal(*window_ptr, &freqs); + window_ptr += 1; + } + *next_chosen_match++ = lzx_item; + } + spec->num_chosen_items = next_chosen_match - spec->chosen_items; + lzx_make_huffman_codes(&freqs, &spec->codes, ctx->num_main_syms); + spec->block_type = lzx_choose_verbatim_or_aligned(&freqs, &spec->codes); +} - if (uncompressed_len < 100) +/* Prepare the input window into one or more LZX blocks ready to be output. */ +static void +lzx_prepare_blocks(struct lzx_compressor * ctx) +{ + /* Set up a default cost model. */ + lzx_set_default_costs(&ctx->costs, ctx->num_main_syms); + + /* Set up the block specifications. + * 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. */ + ctx->num_blocks = DIV_ROUND_UP(ctx->window_size, LZX_DIV_BLOCK_SIZE); + for (unsigned i = 0; i < ctx->num_blocks; i++) { + unsigned pos = LZX_DIV_BLOCK_SIZE * i; + ctx->block_specs[i].window_pos = pos; + ctx->block_specs[i].block_size = min(ctx->window_size - pos, + LZX_DIV_BLOCK_SIZE); + } + + /* Load the window into the match-finder. */ + lz_bt_load_window(&ctx->mf, ctx->window, ctx->window_size); + + /* Determine sequence of matches/literals to output for each block. */ + lzx_lru_queue_init(&ctx->queue); + ctx->optimum_cur_idx = 0; + ctx->optimum_end_idx = 0; + for (unsigned i = 0; i < ctx->num_blocks; i++) { + lzx_optimize_block(ctx, &ctx->block_specs[i], + ctx->params.alg_params.slow.num_optim_passes); + } +} + +/* + * This is the fast version of lzx_prepare_blocks(). This version "quickly" + * prepares a single compressed block containing the entire input. See the + * description of the "Fast algorithm" at the beginning of this file for more + * information. + * + * Input --- the preprocessed data: + * + * ctx->window[] + * ctx->window_size + * + * Output --- the block specification and the corresponding match/literal data: + * + * ctx->block_specs[] + * ctx->num_blocks + * ctx->chosen_items[] + */ +static void +lzx_prepare_block_fast(struct lzx_compressor * ctx) +{ + struct lzx_record_ctx record_ctx; + struct lzx_block_spec *spec; + + /* Parameters to hash chain LZ match finder + * (lazy with 1 match lookahead) */ + static const struct lz_params lzx_lz_params = { + /* Although LZX_MIN_MATCH_LEN == 2, length 2 matches typically + * aren't worth choosing when using greedy or lazy parsing. */ + .min_match = 3, + .max_match = LZX_MAX_MATCH_LEN, + .max_offset = LZX_MAX_WINDOW_SIZE, + .good_match = LZX_MAX_MATCH_LEN, + .nice_match = LZX_MAX_MATCH_LEN, + .max_chain_len = LZX_MAX_MATCH_LEN, + .max_lazy_match = LZX_MAX_MATCH_LEN, + .too_far = 4096, + }; + + /* Initialize symbol frequencies and match offset LRU queue. */ + memset(&record_ctx.freqs, 0, sizeof(struct lzx_freqs)); + lzx_lru_queue_init(&record_ctx.queue); + record_ctx.matches = ctx->chosen_items; + + /* Determine series of matches/literals to output. */ + lz_analyze_block(ctx->window, + ctx->window_size, + lzx_record_match, + lzx_record_literal, + &record_ctx, + &lzx_lz_params, + ctx->prev_tab); + + /* Set up block specification. */ + spec = &ctx->block_specs[0]; + spec->block_type = LZX_BLOCKTYPE_ALIGNED; + spec->window_pos = 0; + spec->block_size = ctx->window_size; + spec->num_chosen_items = (record_ctx.matches - ctx->chosen_items); + spec->chosen_items = ctx->chosen_items; + lzx_make_huffman_codes(&record_ctx.freqs, &spec->codes, + ctx->num_main_syms); + ctx->num_blocks = 1; +} + +static size_t +lzx_compress(const void *uncompressed_data, size_t uncompressed_size, + void *compressed_data, size_t compressed_size_avail, void *_ctx) +{ + struct lzx_compressor *ctx = _ctx; + struct output_bitstream ostream; + size_t compressed_size; + + if (uncompressed_size < 100) { + LZX_DEBUG("Too small to bother compressing."); + return 0; + } + + if (uncompressed_size > ctx->max_window_size) { + LZX_DEBUG("Can't compress %zu bytes using window of %u bytes!", + uncompressed_size, ctx->max_window_size); return 0; + } + + LZX_DEBUG("Attempting to compress %zu bytes...", + uncompressed_size); + + /* The input data must be preprocessed. To avoid changing the original + * input, copy it to a temporary buffer. */ + memcpy(ctx->window, uncompressed_data, uncompressed_size); + ctx->window_size = uncompressed_size; - memset(&freq_tabs, 0, sizeof(freq_tabs)); - queue.R0 = 1; - queue.R1 = 1; - queue.R2 = 1; + /* This line is unnecessary; it just avoids inconsequential accesses of + * uninitialized memory that would show up in memory-checking tools such + * as valgrind. */ + memset(&ctx->window[ctx->window_size], 0, 12); - /* 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); + LZX_DEBUG("Preprocessing data..."); /* Before doing any actual compression, do the call instruction (0xe8 - * byte) translation on the uncompressed data. */ - do_call_insn_preprocessing(uncompressed_data, uncompressed_len); + * byte) translation on the uncompressed data. */ + lzx_do_e8_preprocessing(ctx->window, ctx->window_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_DEBUG("Preparing blocks..."); - 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); + /* Prepare the compressed data. */ + if (ctx->params.algorithm == WIMLIB_LZX_ALGORITHM_FAST) + lzx_prepare_block_fast(ctx); + else + lzx_prepare_blocks(ctx); - lzx_make_huffman_codes(&freq_tabs, &codes); + LZX_DEBUG("Writing compressed blocks..."); - /* Initialize the output bitstream. */ - init_output_bitstream(&ostream, compressed_data, uncompressed_len - 1); + /* Generate the compressed data. */ + init_output_bitstream(&ostream, compressed_data, compressed_size_avail); + lzx_write_all_blocks(ctx, &ostream); - /* 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); + LZX_DEBUG("Flushing bitstream..."); + compressed_size = flush_output_bitstream(&ostream); + if (compressed_size == (u32)~0UL) { + LZX_DEBUG("Data did not compress to %zu bytes or less!", + compressed_size_avail); + return 0; + } - /* The next bit indicates whether the block size is the default (32768), - * indicated by a 1 bit, or whether the block size is given by the next - * 16 bits, indicated by a 0 bit. */ - if (uncompressed_len == 32768) { - bitstream_put_bits(&ostream, 1, 1); + LZX_DEBUG("Done: compressed %zu => %zu bytes.", + uncompressed_size, compressed_size); + + /* Verify that we really get the same thing back when decompressing. + * Although this could be disabled by default in all cases, it only + * takes around 2-3% of the running time of the slow algorithm to do the + * verification. */ + if (ctx->params.algorithm == WIMLIB_LZX_ALGORITHM_SLOW + #if defined(ENABLE_LZX_DEBUG) || defined(ENABLE_VERIFY_COMPRESSION) + || 1 + #endif + ) + { + struct wimlib_decompressor *decompressor; + + if (0 == wimlib_create_decompressor(WIMLIB_COMPRESSION_TYPE_LZX, + ctx->max_window_size, + NULL, + &decompressor)) + { + int ret; + ret = wimlib_decompress(compressed_data, + compressed_size, + ctx->window, + uncompressed_size, + decompressor); + wimlib_free_decompressor(decompressor); + + if (ret) { + ERROR("Failed to decompress data we " + "compressed using LZX algorithm"); + wimlib_assert(0); + return 0; + } + if (memcmp(uncompressed_data, ctx->window, uncompressed_size)) { + ERROR("Data we compressed using LZX algorithm " + "didn't decompress to original"); + wimlib_assert(0); + return 0; + } + } else { + WARNING("Failed to create decompressor for " + "data verification!"); + } + } + return compressed_size; +} + +static void +lzx_free_compressor(void *_ctx) +{ + struct lzx_compressor *ctx = _ctx; + + if (ctx) { + FREE(ctx->chosen_items); + FREE(ctx->cached_matches); + FREE(ctx->optimum); + lz_bt_destroy(&ctx->mf); + FREE(ctx->block_specs); + FREE(ctx->prev_tab); + FREE(ctx->window); + FREE(ctx); + } +} + +static const struct wimlib_lzx_compressor_params lzx_fast_default = { + .hdr = { + .size = sizeof(struct wimlib_lzx_compressor_params), + }, + .algorithm = WIMLIB_LZX_ALGORITHM_FAST, + .use_defaults = 0, + .alg_params = { + .fast = { + }, + }, +}; +static const struct wimlib_lzx_compressor_params lzx_slow_default = { + .hdr = { + .size = sizeof(struct wimlib_lzx_compressor_params), + }, + .algorithm = WIMLIB_LZX_ALGORITHM_SLOW, + .use_defaults = 0, + .alg_params = { + .slow = { + .use_len2_matches = 1, + .nice_match_length = 32, + .num_optim_passes = 2, + .max_search_depth = 50, + .main_nostat_cost = 15, + .len_nostat_cost = 15, + .aligned_nostat_cost = 7, + }, + }, +}; + +static const struct wimlib_lzx_compressor_params * +lzx_get_params(const struct wimlib_compressor_params_header *_params) +{ + const struct wimlib_lzx_compressor_params *params = + (const struct wimlib_lzx_compressor_params*)_params; + + if (params == NULL) { + LZX_DEBUG("Using default algorithm and parameters."); + params = &lzx_slow_default; } else { - bitstream_put_bits(&ostream, 0, 1); - bitstream_put_bits(&ostream, uncompressed_len, 16); + if (params->use_defaults) { + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) + params = &lzx_slow_default; + else + params = &lzx_fast_default; + } } + return params; +} - /* 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; +static int +lzx_create_compressor(size_t window_size, + const struct wimlib_compressor_params_header *_params, + void **ctx_ret) +{ + const struct wimlib_lzx_compressor_params *params = lzx_get_params(_params); + struct lzx_compressor *ctx; - /* 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; + LZX_DEBUG("Allocating LZX context..."); - /* 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; + if (!lzx_window_size_valid(window_size)) + return WIMLIB_ERR_INVALID_PARAM; - /* Write the compressed literals. */ - ret = lzx_write_compressed_literals(&ostream, block_type, - match_tab, num_matches, &codes); - if (ret) - return 0; + ctx = CALLOC(1, sizeof(struct lzx_compressor)); + if (ctx == NULL) + goto oom; - ret = flush_output_bitstream(&ostream); - if (ret) - return 0; + ctx->num_main_syms = lzx_get_num_main_syms(window_size); + ctx->max_window_size = window_size; + ctx->window = MALLOC(window_size + 12); + if (ctx->window == NULL) + goto oom; + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_FAST) { + ctx->prev_tab = MALLOC(window_size * sizeof(ctx->prev_tab[0])); + if (ctx->prev_tab == NULL) + goto oom; + } + + size_t block_specs_length = DIV_ROUND_UP(window_size, LZX_DIV_BLOCK_SIZE); + ctx->block_specs = MALLOC(block_specs_length * sizeof(ctx->block_specs[0])); + if (ctx->block_specs == NULL) + goto oom; + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { + unsigned min_match_len = LZX_MIN_MATCH_LEN; + if (!params->alg_params.slow.use_len2_matches) + min_match_len = max(min_match_len, 3); + + if (!lz_bt_init(&ctx->mf, + window_size, + min_match_len, + LZX_MAX_MATCH_LEN, + params->alg_params.slow.nice_match_length, + params->alg_params.slow.max_search_depth)) + goto oom; + } + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { + ctx->optimum = MALLOC((LZX_OPTIM_ARRAY_SIZE + + min(params->alg_params.slow.nice_match_length, + LZX_MAX_MATCH_LEN)) * + sizeof(ctx->optimum[0])); + if (ctx->optimum == NULL) + goto oom; + } + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { + ctx->cached_matches = MALLOC(LZX_CACHE_SIZE); + if (ctx->cached_matches == NULL) + goto oom; + ctx->cache_limit = ctx->cached_matches + + LZX_CACHE_LEN - (LZX_MAX_MATCHES_PER_POS + 1); + } - compressed_len = ostream.bit_output - (u8*)compressed_data; + ctx->chosen_items = MALLOC(window_size * sizeof(ctx->chosen_items[0])); + if (ctx->chosen_items == NULL) + goto oom; -#ifdef ENABLE_VERIFY_COMPRESSION - /* Verify that we really get the same thing back when decompressing. */ - u8 buf[uncompressed_len]; - ret = lzx_decompress(compressed_data, compressed_len, buf, - uncompressed_len); - if (ret != 0) { - ERROR("lzx_compress(): Failed to decompress data we compressed"); - abort(); + memcpy(&ctx->params, params, sizeof(struct wimlib_lzx_compressor_params)); + memset(&ctx->zero_codes, 0, sizeof(ctx->zero_codes)); + + LZX_DEBUG("Successfully allocated new LZX context."); + + *ctx_ret = ctx; + return 0; + +oom: + lzx_free_compressor(ctx); + return WIMLIB_ERR_NOMEM; +} + +static u64 +lzx_get_needed_memory(size_t max_block_size, + const struct wimlib_compressor_params_header *_params) +{ + const struct wimlib_lzx_compressor_params *params = lzx_get_params(_params); + + u64 size = 0; + + size += sizeof(struct lzx_compressor); + + size += max_block_size + 12; + + size += DIV_ROUND_UP(max_block_size, LZX_DIV_BLOCK_SIZE) * + sizeof(((struct lzx_compressor*)0)->block_specs[0]); + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { + size += max_block_size * sizeof(((struct lzx_compressor*)0)->chosen_items[0]); + size += lz_bt_get_needed_memory(max_block_size); + size += (LZX_OPTIM_ARRAY_SIZE + + min(params->alg_params.slow.nice_match_length, + LZX_MAX_MATCH_LEN)) * + sizeof(((struct lzx_compressor *)0)->optimum[0]); + size += LZX_CACHE_SIZE; + } else { + size += max_block_size * sizeof(((struct lzx_compressor*)0)->prev_tab[0]); } + return size; +} + +static bool +lzx_params_valid(const struct wimlib_compressor_params_header *_params) +{ + const struct wimlib_lzx_compressor_params *params = + (const struct wimlib_lzx_compressor_params*)_params; - 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(); + if (params->hdr.size != sizeof(struct wimlib_lzx_compressor_params)) { + LZX_DEBUG("Invalid parameter structure size!"); + return false; + } + + if (params->algorithm != WIMLIB_LZX_ALGORITHM_SLOW && + params->algorithm != WIMLIB_LZX_ALGORITHM_FAST) + { + LZX_DEBUG("Invalid algorithm."); + return false; + } + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW && + !params->use_defaults) + { + if (params->alg_params.slow.num_optim_passes < 1) + { + LZX_DEBUG("Invalid number of optimization passes!"); + return false; + } + + if (params->alg_params.slow.main_nostat_cost < 1 || + params->alg_params.slow.main_nostat_cost > 16) + { + LZX_DEBUG("Invalid main_nostat_cost!"); + return false; + } + + if (params->alg_params.slow.len_nostat_cost < 1 || + params->alg_params.slow.len_nostat_cost > 16) + { + LZX_DEBUG("Invalid len_nostat_cost!"); + return false; + } + + if (params->alg_params.slow.aligned_nostat_cost < 1 || + params->alg_params.slow.aligned_nostat_cost > 8) + { + LZX_DEBUG("Invalid aligned_nostat_cost!"); + return false; } } -#endif - return compressed_len; + return true; } + +const struct compressor_ops lzx_compressor_ops = { + .params_valid = lzx_params_valid, + .get_needed_memory = lzx_get_needed_memory, + .create_compressor = lzx_create_compressor, + .compress = lzx_compress, + .free_compressor = lzx_free_compressor, +};