X-Git-Url: https://wimlib.net/git/?p=wimlib;a=blobdiff_plain;f=src%2Flzx-compress.c;h=3f0626e49b478e7d12bf4c2f3fcec1ae73d78caf;hp=a8e15b24f107cf7239bb24d5416399574e725d99;hb=71abd45bcc85ddb5cf60aba8bbeb53b40780f521;hpb=9024010515ca562dd8730d4ca846b5335ff6e48a diff --git a/src/lzx-compress.c b/src/lzx-compress.c index a8e15b24..3f0626e4 100644 --- a/src/lzx-compress.c +++ b/src/lzx-compress.c @@ -1,12 +1,10 @@ /* * lzx-compress.c * - * LZX compression routines, originally based on code written by Matthew T. - * Russotto (liblzxcomp), but heavily modified. + * LZX compression routines */ /* - * Copyright (C) 2002 Matthew T. Russotto * Copyright (C) 2012, 2013 Eric Biggers * * This file is part of wimlib, a library for working with WIM files. @@ -27,60 +25,404 @@ /* - * This file provides wimlib_lzx_compress(), a function to compress an in-memory - * buffer of data using LZX compression, as used in the WIM file format. - * - * Please see the comments in lzx-decompress.c for more information about this - * compression format. - * - * One thing to keep in mind is that there is no sliding window, since the - * window is always the entirety of a WIM chunk, which is at most WIM_CHUNK_SIZE - * ( = 32768) bytes. - * - * The basic compression algorithm used here should be familiar if you are - * familiar with Huffman trees and with other LZ77 and Huffman-based formats - * such as DEFLATE. Otherwise it can be quite tricky to understand. Basically - * it is the following: - * - * - Preprocess the input data (LZX-specific) - * - Go through the input data and determine matches. This part is based on - * code from zlib, and a hash table of 3-character strings is used to - * accelerate the process of finding matches. - * - Build the Huffman trees based on the frequencies of symbols determined - * while recording matches. - * - Output the block header, including the Huffman trees; then output the - * compressed stream of matches and literal characters. - * - * It is possible for a WIM chunk to include multiple LZX blocks, since for some - * input data this will produce a better compression ratio (especially since - * each block can include new Huffman codes). However, producing multiple LZX - * blocks from one input chunk is not yet implemented. + * This file contains a compressor for the LZX compression format, as used in + * the WIM file format. + * + * Format + * ====== + * + * First, the primary reference for the LZX compression format is the + * specification released by Microsoft. + * + * Second, the comments in lzx-decompress.c provide some more information about + * the LZX compression format, including errors in the Microsoft specification. + * + * Do note that LZX shares many similarities with DEFLATE, the algorithm used by + * zlib and gzip. Both LZX and DEFLATE use LZ77 matching and Huffman coding, + * and certain other details are quite similar, such as the method for storing + * Huffman codes. However, some of the main differences are: + * + * - LZX preprocesses the data before attempting to compress it. + * - LZX uses a "main" alphabet which combines literals and matches, with the + * match symbols containing a "length header" (giving all or part of the match + * length) and a "position footer" (giving, roughly speaking, the order of + * magnitude of the match offset). + * - LZX does not have static Huffman blocks; however it does have two types of + * dynamic Huffman blocks ("aligned offset" and "verbatim"). + * - LZX has a minimum match length of 2 rather than 3. + * - In LZX, match offsets 0 through 2 actually represent entries in a LRU queue + * of match offsets. + * + * Algorithms + * ========== + * + * There are actually two distinct overall algorithms implemented here. We + * shall refer to them as the "slow" algorithm and the "fast" algorithm. The + * "slow" algorithm spends more time compressing to achieve a higher compression + * ratio compared to the "fast" algorithm. More details are presented below. + * + * Slow algorithm + * -------------- + * + * The "slow" algorithm to generate LZX-compressed data is roughly as follows: + * + * 1. Preprocess the input data to translate the targets of x86 call instructions + * to absolute offsets. + * + * 2. Determine the best known sequence of LZ77 matches ((offset, length) pairs) + * and literal bytes to divide the input into. Raw match-finding is done + * using a very clever binary tree search based on the "Bt3" algorithm from + * 7-Zip. Parsing, or match-choosing, is solved essentially as a + * minimum-cost path problem, but using a heuristic forward search based on + * the Deflate encoder from 7-Zip rather than a more intuitive backward + * search, the latter of which would naively require that all matches be + * found. This heuristic search, as well as other heuristics such as limits + * on the matches considered, considerably speed up this part of the + * algorithm, which is the main bottleneck. Finally, after matches and + * literals are chosen, the needed Huffman codes needed to output them are + * built. + * + * 3. Up to a certain number of iterations, use the resulting Huffman codes to + * refine a cost model and go back to Step #2 to determine an improved + * sequence of matches and literals. + * + * 4. Up to a certain depth, try splitting the current block to see if the + * compression ratio can be improved. This may be the case if parts of the + * input differ greatly from each other and could benefit from different + * Huffman codes. + * + * 5. Output the resulting block(s) using the match/literal sequences and the + * Huffman codes that were computed for each block. + * + * Fast algorithm + * -------------- + * + * The fast algorithm (and the only one available in wimlib v1.5.1 and earlier) + * spends much less time on the main bottlenecks of the compression process --- + * that is the match finding, match choosing, and block splitting. Matches are + * found and chosen with hash chains using a greedy parse with one position of + * look-ahead. No block splitting is done; only compressing the full input into + * an aligned offset block is considered. + * + * API + * === + * + * The old API (retained for backward compatibility) consists of just one function: + * + * wimlib_lzx_compress() + * + * The new compressor has more potential parameters and needs more memory, so + * the new API ties up memory allocations and compression parameters into a + * context: + * + * wimlib_lzx_alloc_context() + * wimlib_lzx_compress2() + * wimlib_lzx_free_context() + * + * Both wimlib_lzx_compress() and wimlib_lzx_compress2() are designed to + * compress an in-memory buffer of up to 32768 bytes. There is no sliding + * window. This is suitable for the WIM format, which uses fixed-size chunks + * that are seemingly always 32768 bytes. If needed, the compressor potentially + * could be extended to support a larger and/or sliding window. + * + * Both wimlib_lzx_compress() and wimlib_lzx_compress2() return 0 if the data + * could not be compressed to less than the size of the uncompressed data. + * Again, this is suitable for the WIM format, which stores such data chunks + * uncompressed. + * + * The functions in this API are exported from the library, although this is + * only in case other programs happen to have uses for it other than WIM + * reading/writing as already handled through the rest of the library. + * + * Acknowledgments + * =============== + * + * Acknowledgments to several other open-source projects that made it possible + * to implement this code: + * + * - 7-Zip (author: Igor Pavlov), for the binary tree match-finding + * algorithm, the heuristic near-optimal forward match-choosing + * algorithm, and the block splitting algorithm. + * + * - zlib (author: Jean-loup Gailly and Mark Adler), for the hash table + * match-finding algorithm. + * + * - lzx-compress (author: Matthew T. Russotto), on which some parts of this + * code were originally based. */ +#ifdef HAVE_CONFIG_H +# include "config.h" +#endif + #include "wimlib.h" -#include "lzx.h" -#include "compress.h" -#include +#include "wimlib/compress.h" +#include "wimlib/error.h" +#include "wimlib/lzx.h" +#include "wimlib/util.h" + +#ifdef ENABLE_LZX_DEBUG +# include +#endif + #include +/* Experimental parameters not exposed through the API */ +#define LZX_PARAM_OPTIM_ARRAY_SIZE 1024 +#define LZX_PARAM_ACCOUNT_FOR_LRU 1 +#define LZX_PARAM_DONT_SKIP_MATCHES 0 +#define LZX_PARAM_USE_EMPIRICAL_DEFAULT_COSTS 1 + +/* Currently, this constant can't simply be changed because the code currently + * uses a static number of position slots (and may make other assumptions as + * well). */ +#define LZX_MAX_WINDOW_SIZE 32768 + +/* This may be WIM-specific */ +#define LZX_DEFAULT_BLOCK_SIZE 32768 + +#define LZX_LZ_HASH_BITS 15 +#define LZX_LZ_HASH_SIZE (1 << LZX_LZ_HASH_BITS) +#define LZX_LZ_HASH_MASK (LZX_LZ_HASH_SIZE - 1) +#define LZX_LZ_HASH_SHIFT 5 + +/* Codewords for the LZX main, length, and aligned offset Huffman codes */ +struct lzx_codewords { + u16 main[LZX_MAINTREE_NUM_SYMBOLS]; + u16 len[LZX_LENTREE_NUM_SYMBOLS]; + u16 aligned[LZX_ALIGNEDTREE_NUM_SYMBOLS]; +}; + +/* Lengths for the LZX main, length, and aligned offset Huffman codes */ +struct lzx_lens { + u8 main[LZX_MAINTREE_NUM_SYMBOLS]; + u8 len[LZX_LENTREE_NUM_SYMBOLS]; + u8 aligned[LZX_ALIGNEDTREE_NUM_SYMBOLS]; +}; -/* Structure to contain the Huffman codes for the main, length, and aligned - * offset trees. */ +/* The LZX main, length, and aligned offset Huffman codes */ struct lzx_codes { - u16 main_codewords[LZX_MAINTREE_NUM_SYMBOLS]; - u8 main_lens[LZX_MAINTREE_NUM_SYMBOLS]; + struct lzx_codewords codewords; + struct lzx_lens lens; +}; + +/* Tables for tallying symbol frequencies in the three LZX alphabets */ +struct lzx_freqs { + freq_t main[LZX_MAINTREE_NUM_SYMBOLS]; + freq_t len[LZX_LENTREE_NUM_SYMBOLS]; + freq_t aligned[LZX_ALIGNEDTREE_NUM_SYMBOLS]; +}; + +/* LZX intermediate match/literal format */ +struct lzx_match { + /* Bit Description + * + * 31 1 if a match, 0 if a literal. + * + * 30-25 position slot. This can be at most 50, so it will fit in 6 + * bits. + * + * 8-24 position footer. This is the offset of the real formatted + * offset from the position base. This can be at most 17 bits + * (since lzx_extra_bits[LZX_NUM_POSITION_SLOTS - 1] is 17). + * + * 0-7 length of match, minus 2. This can be at most + * (LZX_MAX_MATCH - 2) == 255, so it will fit in 8 bits. */ + u32 data; +}; + +/* Raw LZ match/literal format: just a length and offset. + * + * The length is the number of bytes of the match, and the offset is the number + * of bytes back in the input the match is from the matched text. + * + * If @len < LZX_MIN_MATCH, then it's really just a literal byte and @offset is + * meaningless. */ +struct raw_match { + u16 len; + u16 offset; +}; + +/* Specification for a LZX block */ +struct lzx_block_spec { + + /* Set to 1 if this block has been split (in two --- we only considser + * binary splits). In such cases the rest of the fields are + * unimportant, since the relevant information is rather in the + * structures for the sub-blocks. */ + u8 is_split : 1; + + /* One of the LZX_BLOCKTYPE_* constants indicating which type of this + * block. */ + u8 block_type : 2; + + /* 0-based position in the window at which this block starts. */ + u16 window_pos; + + /* The number of bytes of uncompressed data this block represents. */ + u16 block_size; + + /* The position in the 'chosen_matches' array in the `struct + * lzx_compressor' at which the match/literal specifications for + * this block begin. */ + unsigned chosen_matches_start_pos; + + /* The number of match/literal specifications for this block. */ + u16 num_chosen_matches; - u16 len_codewords[LZX_LENTREE_NUM_SYMBOLS]; - u8 len_lens[LZX_LENTREE_NUM_SYMBOLS]; + /* Huffman codes for this block. */ + struct lzx_codes codes; +}; - u16 aligned_codewords[LZX_ALIGNEDTREE_NUM_SYMBOLS]; - u8 aligned_lens[LZX_ALIGNEDTREE_NUM_SYMBOLS]; +/* + * An array of these structures is used during the match-choosing algorithm. + * They correspond to consecutive positions in the window and are used to keep + * track of the cost to reach each position, and the match/literal choices that + * need to be chosen to reach that position. + */ +struct lzx_optimal { + /* The approximate minimum cost, in bits, to reach this position in the + * window which has been found so far. */ + u32 cost; + + /* The union here is just for clarity, since the fields are used in two + * slightly different ways. Initially, the @prev structure is filled in + * first, and links go from later in the window to earlier in the + * window. Later, @next structure is filled in and links go from + * earlier in the window to later in the window. */ + union { + struct { + /* Position of the start of the match or literal that + * was taken to get to this position in the approximate + * minimum-cost parse. */ + u16 link; + + /* Offset (as in a LZ (length, offset) pair) of the + * match or literal that was taken to get to this + * position in the approximate minimum-cost parse. */ + u16 match_offset; + } prev; + struct { + /* Position at which the match or literal starting at + * this position ends in the minimum-cost parse. */ + u16 link; + + /* Offset (as in a LZ (length, offset) pair) of the + * match or literal starting at this position in the + * approximate minimum-cost parse. */ + u16 match_offset; + } next; + }; +#if LZX_PARAM_ACCOUNT_FOR_LRU + struct lzx_lru_queue queue; +#endif }; -struct lzx_freq_tables { - freq_t main_freq_table[LZX_MAINTREE_NUM_SYMBOLS]; - freq_t len_freq_table[LZX_LENTREE_NUM_SYMBOLS]; - freq_t aligned_freq_table[LZX_ALIGNEDTREE_NUM_SYMBOLS]; +/* State of the LZX compressor */ +struct lzx_compressor { + + /* The parameters that were used to create the compressor. */ + struct wimlib_lzx_params params; + + /* The buffer of data to be compressed. + * + * 0xe8 byte preprocessing is done directly on the data here before + * further compression. + * + * Note that this compressor does *not* use a sliding window!!!! + * It's not needed in the WIM format, since every chunk is compressed + * independently. This is by design, to allow random access to the + * chunks. + * + * We reserve a few extra bytes to potentially allow reading off the end + * of the array in the match-finding code for optimization purposes. + */ + u8 window[LZX_MAX_WINDOW_SIZE + 12]; + + /* Number of bytes of data to be compressed, which is the number of + * bytes of data in @window that are actually valid. */ + unsigned window_size; + + /* The current match offset LRU queue. */ + struct lzx_lru_queue queue; + + /* Space for sequence of matches/literals that were chosen. + * + * Each LZX_MAX_WINDOW_SIZE-sized portion of this array is used for a + * different block splitting level. */ + struct lzx_match *chosen_matches; + + /* Structures used during block splitting. + * + * This can be thought of as a binary tree. block_specs[(1) - 1] + * represents to the top-level block (root node), and block_specs[(i*2) + * - 1] and block_specs[(i*2+1) - 1] represent the sub-blocks (child + * nodes) resulting from a binary split of the block represented by + * block_spec[(i) - 1]. + */ + struct lzx_block_spec *block_specs; + + /* This is simply filled in with zeroes and used to avoid special-casing + * the output of the first compressed Huffman code, which conceptually + * has a delta taken from a code with all symbols having zero-length + * codewords. */ + struct lzx_codes zero_codes; + + /* Slow algorithm only: The current cost model. */ + struct lzx_lens costs; + + /* Slow algorithm only: Table that maps the hash codes for 3 character + * sequences to the most recent position that sequence (or a sequence + * sharing the same hash code) appeared in the window. */ + u16 *hash_tab; + + /* Slow algorithm only: Table that maps 2-character sequences to the + * most recent position that sequence appeared in the window. */ + u16 *digram_tab; + + /* Slow algorithm only: Table that contains the logical child pointers + * in the binary trees in the match-finding code. + * + * child_tab[i*2] and child_tab[i*2+1] are the left and right pointers, + * respectively, from the binary tree root corresponding to window + * position i. */ + u16 *child_tab; + + /* Slow algorithm only: Matches that were already found and are saved in + * memory for subsequent queries (e.g. when block splitting). */ + struct raw_match *cached_matches; + + /* Slow algorithm only: Next position in 'cached_matches' to either + * return or fill in. */ + unsigned cached_matches_pos; + + /* Slow algorithm only: %true if reading from 'cached_matches'; %false + * if writing to 'cached_matches'. */ + bool matches_already_found; + + /* Slow algorithm only: Position in window of next match to return. */ + unsigned match_window_pos; + + /* Slow algorithm only: No matches returned shall reach past this + * position. */ + unsigned match_window_end; + + /* Slow algorithm only: Temporary space used for match-choosing + * algorithm. + * + * The size of this array must be at least LZX_MAX_MATCH but otherwise + * is arbitrary. More space simply allows the match-choosing algorithm + * to find better matches (depending on the input, as always). */ + struct lzx_optimal *optimum; + + /* Slow algorithm only: Variables used by the match-choosing algorithm. + * + * When matches have been chosen, optimum_cur_idx is set to the position + * in the window of the next match/literal to return and optimum_end_idx + * is set to the position in the window at the end of the last + * match/literal to return. */ + u32 optimum_cur_idx; + u32 optimum_end_idx; }; /* Returns the LZX position slot that corresponds to a given formatted offset. @@ -92,7 +434,7 @@ struct lzx_freq_tables { * numbers in the lzx_position_base array to calculate the slot directly from * the formatted offset without actually looking at the array. */ -static inline unsigned +static unsigned lzx_get_position_slot(unsigned formatted_offset) { #if 0 @@ -115,146 +457,72 @@ lzx_get_position_slot(unsigned formatted_offset) * increases starting at the 655360 entry, and it is >= 2 * because the below calculation fails if the most significant * bit is lower than the 2's place. */ - wimlib_assert(formatted_offset >= 2 && formatted_offset < 655360); + LZX_ASSERT(2 <= formatted_offset && formatted_offset < 655360); unsigned mssb_idx = bsr32(formatted_offset); return (mssb_idx << 1) | ((formatted_offset >> (mssb_idx - 1)) & 1); } } -static u32 -lzx_record_literal(u8 literal, void *__main_freq_tab) +/* Compute the hash code for the next 3-character sequence in the window. */ +static unsigned +lzx_lz_compute_hash(const u8 *window) { - freq_t *main_freq_tab = __main_freq_tab; - main_freq_tab[literal]++; - return literal; + unsigned hash; + + hash = window[0]; + hash <<= LZX_LZ_HASH_SHIFT; + hash ^= window[1]; + hash <<= LZX_LZ_HASH_SHIFT; + hash ^= window[2]; + return hash & LZX_LZ_HASH_MASK; } -/* Constructs a match from an offset and a length, and updates the LRU queue and - * the frequency of symbols in the main, length, and aligned offset alphabets. - * The return value is a 32-bit number that provides the match in an - * intermediate representation documented below. */ -static u32 -lzx_record_match(unsigned match_offset, unsigned match_len, - void *__freq_tabs, void *__queue) +/* Build the main, length, and aligned offset Huffman codes used in LZX. + * + * This takes as input the frequency tables for each code and produces as output + * a set of tables that map symbols to codewords and lengths. */ +static void +lzx_make_huffman_codes(const struct lzx_freqs *freqs, + struct lzx_codes *codes) { - struct lzx_freq_tables *freq_tabs = __freq_tabs; - struct lru_queue *queue = __queue; - unsigned position_slot; - unsigned position_footer = 0; - u32 match; - u32 len_header; - u32 len_pos_header; - unsigned len_footer; - unsigned adjusted_match_len; - - wimlib_assert(match_len >= LZX_MIN_MATCH && match_len <= LZX_MAX_MATCH); - wimlib_assert(match_offset != 0); - - /* If possible, encode this offset as a repeated offset. */ - if (match_offset == queue->R0) { - position_slot = 0; - } else if (match_offset == queue->R1) { - swap(queue->R0, queue->R1); - position_slot = 1; - } else if (match_offset == queue->R2) { - swap(queue->R0, queue->R2); - position_slot = 2; - } else { - /* Not a repeated offset. */ - - /* offsets of 0, 1, and 2 are reserved for the repeated offset - * codes, so non-repeated offsets must be encoded as 3+. The - * minimum offset is 1, so encode the offsets offset by 2. */ - unsigned formatted_offset = match_offset + LZX_MIN_MATCH; - - queue->R2 = queue->R1; - queue->R1 = queue->R0; - queue->R0 = match_offset; - - /* The (now-formatted) offset will actually be encoded as a - * small position slot number that maps to a certain hard-coded - * offset (position base), followed by a number of extra bits--- - * the position footer--- that are added to the position base to - * get the original formatted offset. */ - - position_slot = lzx_get_position_slot(formatted_offset); - position_footer = formatted_offset & - ((1 << lzx_get_num_extra_bits(position_slot)) - 1); - } - - adjusted_match_len = match_len - LZX_MIN_MATCH; - - /* Pack the position slot, position footer, and match length into an - * intermediate representation. - * - * bits description - * ---- ----------------------------------------------------------- - * - * 31 1 if a match, 0 if a literal. - * - * 30-25 position slot. This can be at most 50, so it will fit in 6 - * bits. - * - * 8-24 position footer. This is the offset of the real formatted - * offset from the position base. This can be at most 17 bits - * (since lzx_extra_bits[LZX_NUM_POSITION_SLOTS - 1] is 17). - * - * 0-7 length of match, offset by 2. This can be at most - * (LZX_MAX_MATCH - 2) == 255, so it will fit in 8 bits. */ - match = 0x80000000 | - (position_slot << 25) | - (position_footer << 8) | - (adjusted_match_len); - - /* The match length must be at least 2, so let the adjusted match length - * be the match length minus 2. - * - * If it is less than 7, the adjusted match length is encoded as a 3-bit - * number offset by 2. Otherwise, the 3-bit length header is all 1's - * and the actual adjusted length is given as a symbol encoded with the - * length tree, offset by 7. - */ - if (adjusted_match_len < LZX_NUM_PRIMARY_LENS) { - len_header = adjusted_match_len; - } else { - len_header = LZX_NUM_PRIMARY_LENS; - len_footer = adjusted_match_len - LZX_NUM_PRIMARY_LENS; - freq_tabs->len_freq_table[len_footer]++; - } - len_pos_header = (position_slot << 3) | len_header; - - wimlib_assert(len_pos_header < LZX_MAINTREE_NUM_SYMBOLS - LZX_NUM_CHARS); - - freq_tabs->main_freq_table[len_pos_header + LZX_NUM_CHARS]++; + make_canonical_huffman_code(LZX_MAINTREE_NUM_SYMBOLS, + LZX_MAX_CODEWORD_LEN, + freqs->main, + codes->lens.main, + codes->codewords.main); - /* Equivalent to: - * if (lzx_extra_bits[position_slot] >= 3) */ - if (position_slot >= 8) - freq_tabs->aligned_freq_table[position_footer & 7]++; + make_canonical_huffman_code(LZX_LENTREE_NUM_SYMBOLS, + LZX_MAX_CODEWORD_LEN, + freqs->len, + codes->lens.len, + codes->codewords.len); - return match; + make_canonical_huffman_code(LZX_ALIGNEDTREE_NUM_SYMBOLS, 8, + freqs->aligned, + codes->lens.aligned, + codes->codewords.aligned); } /* - * Writes a compressed literal match to the output. + * Output a LZX match. * - * @out: The output bitstream. - * @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM) - * @match: The match, encoded as a 32-bit number. - * @codes: Pointer to a structure that contains the codewords for the - * main, length, and aligned offset Huffman codes. + * @out: The bitstream to write the match to. + * @block_type: The type of the LZX block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM) + * @match: The match. + * @codes: Pointer to a structure that contains the codewords for the + * main, length, and aligned offset Huffman codes. */ -static int +static void lzx_write_match(struct output_bitstream *out, int block_type, - u32 match, const struct lzx_codes *codes) + struct lzx_match match, const struct lzx_codes *codes) { /* low 8 bits are the match length minus 2 */ - unsigned match_len_minus_2 = match & 0xff; + unsigned match_len_minus_2 = match.data & 0xff; /* Next 17 bits are the position footer */ - unsigned position_footer = (match >> 8) & 0x1ffff; /* 17 bits */ + unsigned position_footer = (match.data >> 8) & 0x1ffff; /* 17 bits */ /* Next 6 bits are the position slot. */ - unsigned position_slot = (match >> 25) & 0x3f; /* 6 bits */ + unsigned position_slot = (match.data >> 25) & 0x3f; /* 6 bits */ unsigned len_header; unsigned len_footer; unsigned len_pos_header; @@ -262,7 +530,6 @@ lzx_write_match(struct output_bitstream *out, int block_type, unsigned num_extra_bits; unsigned verbatim_bits; unsigned aligned_bits; - int ret; /* If the match length is less than MIN_MATCH (= 2) + * NUM_PRIMARY_LENS (= 7), the length header contains @@ -294,22 +561,16 @@ lzx_write_match(struct output_bitstream *out, int block_type, main_symbol = len_pos_header + LZX_NUM_CHARS; /* Output main symbol. */ - ret = bitstream_put_bits(out, codes->main_codewords[main_symbol], - codes->main_lens[main_symbol]); - if (ret != 0) - return ret; + bitstream_put_bits(out, codes->codewords.main[main_symbol], + codes->lens.main[main_symbol]); /* If there is a length footer, output it using the * length Huffman code. */ if (len_footer != (unsigned)(-1)) { - ret = bitstream_put_bits(out, codes->len_codewords[len_footer], - codes->len_lens[len_footer]); - if (ret != 0) - return ret; + bitstream_put_bits(out, codes->codewords.len[len_footer], + codes->lens.len[len_footer]); } - wimlib_assert(position_slot < LZX_NUM_POSITION_SLOTS); - num_extra_bits = lzx_get_num_extra_bits(position_slot); /* For aligned offset blocks with at least 3 extra bits, output the @@ -319,109 +580,40 @@ lzx_write_match(struct output_bitstream *out, int block_type, if ((block_type == LZX_BLOCKTYPE_ALIGNED) && (num_extra_bits >= 3)) { verbatim_bits = position_footer >> 3; - ret = bitstream_put_bits(out, verbatim_bits, - num_extra_bits - 3); - if (ret != 0) - return ret; + bitstream_put_bits(out, verbatim_bits, + num_extra_bits - 3); aligned_bits = (position_footer & 7); - ret = bitstream_put_bits(out, - codes->aligned_codewords[aligned_bits], - codes->aligned_lens[aligned_bits]); - if (ret != 0) - return ret; + bitstream_put_bits(out, + codes->codewords.aligned[aligned_bits], + codes->lens.aligned[aligned_bits]); } else { /* verbatim bits is the same as the position * footer, in this case. */ - ret = bitstream_put_bits(out, position_footer, num_extra_bits); - if (ret != 0) - return ret; + bitstream_put_bits(out, position_footer, num_extra_bits); } - return 0; } -/* - * Writes all compressed literals in a block, both matches and literal bytes, to - * the output bitstream. - * - * @out: The output bitstream. - * @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM) - * @match_tab[]: The array of matches that will be output. It has length - * of @num_compressed_literals. - * @num_compressed_literals: Number of compressed literals to be output. - * @codes: Pointer to a structure that contains the codewords for the - * main, length, and aligned offset Huffman codes. - */ -static int -lzx_write_compressed_literals(struct output_bitstream *ostream, - int block_type, - const u32 match_tab[], - unsigned num_compressed_literals, - const struct lzx_codes *codes) +static unsigned +lzx_build_precode(const u8 lens[restrict], + const u8 prev_lens[restrict], + unsigned num_syms, + freq_t precode_freqs[restrict LZX_PRETREE_NUM_SYMBOLS], + u8 output_syms[restrict num_syms], + u8 precode_lens[restrict LZX_PRETREE_NUM_SYMBOLS], + u16 precode_codewords[restrict LZX_PRETREE_NUM_SYMBOLS], + unsigned * num_additional_bits_ret) { - unsigned i; - u32 match; - int ret; - - for (i = 0; i < num_compressed_literals; i++) { - match = match_tab[i]; - - /* High bit of the match indicates whether the match is an - * actual match (1) or a literal uncompressed byte (0) */ - if (match & 0x80000000) { - /* match */ - ret = lzx_write_match(ostream, block_type, match, - codes); - if (ret != 0) - return ret; - } else { - /* literal byte */ - wimlib_assert(match < LZX_NUM_CHARS); - ret = bitstream_put_bits(ostream, - codes->main_codewords[match], - codes->main_lens[match]); - if (ret != 0) - return ret; - } - } - return 0; -} - -/* - * Writes a compressed Huffman tree to the output, preceded by the pretree for - * it. - * - * The Huffman tree is represented in the output as a series of path lengths - * from which the canonical Huffman code can be reconstructed. The path lengths - * themselves are compressed using a separate Huffman code, the pretree, which - * consists of LZX_PRETREE_NUM_SYMBOLS (= 20) symbols that cover all possible code - * lengths, plus extra codes for repeated lengths. The path lengths of the - * pretree precede the path lengths of the larger code and are uncompressed, - * consisting of 20 entries of 4 bits each. - * - * @out: The bitstream for the compressed output. - * @lens: The code lengths for the Huffman tree, indexed by symbol. - * @num_symbols: The number of symbols in the code. - */ -static int -lzx_write_compressed_tree(struct output_bitstream *out, - const u8 lens[], unsigned num_symbols) -{ - /* Frequencies of the length symbols, including the RLE symbols (NOT the - * actual lengths themselves). */ - freq_t pretree_freqs[LZX_PRETREE_NUM_SYMBOLS]; - u8 pretree_lens[LZX_PRETREE_NUM_SYMBOLS]; - u16 pretree_codewords[LZX_PRETREE_NUM_SYMBOLS]; - u8 output_syms[num_symbols * 2]; unsigned output_syms_idx; unsigned cur_run_len; unsigned i; unsigned len_in_run; unsigned additional_bits; - char delta; - u8 pretree_sym; + signed char delta; + unsigned num_additional_bits = 0; - ZERO_ARRAY(pretree_freqs); + memset(precode_freqs, 0, + LZX_PRETREE_NUM_SYMBOLS * sizeof(precode_freqs[0])); /* Since the code word lengths use a form of RLE encoding, the goal here * is to find each run of identical lengths when going through them in @@ -437,9 +629,9 @@ lzx_write_compressed_tree(struct output_bitstream *out, */ output_syms_idx = 0; cur_run_len = 1; - for (i = 1; i <= num_symbols; i++) { + for (i = 1; i <= num_syms; i++) { - if (i != num_symbols && lens[i] == lens[i - 1]) { + if (i != num_syms && lens[i] == lens[i - 1]) { /* Still in a run--- keep going. */ cur_run_len++; continue; @@ -462,7 +654,8 @@ lzx_write_compressed_tree(struct output_bitstream *out, while (cur_run_len >= 20) { additional_bits = min(cur_run_len - 20, 0x1f); - pretree_freqs[18]++; + num_additional_bits += 5; + precode_freqs[18]++; output_syms[output_syms_idx++] = 18; output_syms[output_syms_idx++] = additional_bits; cur_run_len -= 20 + additional_bits; @@ -473,7 +666,8 @@ lzx_write_compressed_tree(struct output_bitstream *out, * follows the magic length. */ while (cur_run_len >= 4) { additional_bits = min(cur_run_len - 4, 0xf); - pretree_freqs[17]++; + num_additional_bits += 4; + precode_freqs[17]++; output_syms[output_syms_idx++] = 17; output_syms[output_syms_idx++] = additional_bits; cur_run_len -= 4 + additional_bits; @@ -487,7 +681,7 @@ 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 @@ -495,11 +689,13 @@ lzx_write_compressed_tree(struct output_bitstream *out, * */ while (cur_run_len >= 4) { additional_bits = (cur_run_len > 4); - delta = -(char)len_in_run; + num_additional_bits += 1; + delta = (signed char)prev_lens[i - cur_run_len] - + (signed char)len_in_run; if (delta < 0) delta += 17; - pretree_freqs[19]++; - pretree_freqs[(unsigned char)delta]++; + precode_freqs[19]++; + precode_freqs[(unsigned char)delta]++; output_syms[output_syms_idx++] = 19; output_syms[output_syms_idx++] = additional_bits; output_syms[output_syms_idx++] = delta; @@ -510,41 +706,88 @@ 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; + while (cur_run_len > 0) { + delta = (signed char)prev_lens[i - cur_run_len] - + (signed char)len_in_run; if (delta < 0) delta += 17; - pretree_freqs[(unsigned char)delta]++; + precode_freqs[(unsigned char)delta]++; output_syms[output_syms_idx++] = delta; + cur_run_len--; } cur_run_len = 1; } - wimlib_assert(output_syms_idx < ARRAY_LEN(output_syms)); - - /* Build the pretree from the frequencies of the length symbols. */ + /* Build the precode from the frequencies of the length symbols. */ make_canonical_huffman_code(LZX_PRETREE_NUM_SYMBOLS, LZX_MAX_CODEWORD_LEN, - pretree_freqs, pretree_lens, - pretree_codewords); + precode_freqs, precode_lens, + precode_codewords); + + if (num_additional_bits_ret) + *num_additional_bits_ret = num_additional_bits; + + return output_syms_idx; +} - /* Write the lengths of the pretree codes to the output. */ +/* + * Writes a compressed Huffman code to the output, preceded by the precode for + * it. + * + * The Huffman code is represented in the output as a series of path lengths + * from which the canonical Huffman code can be reconstructed. The path lengths + * themselves are compressed using a separate Huffman code, the precode, which + * consists of LZX_PRETREE_NUM_SYMBOLS (= 20) symbols that cover all possible + * code lengths, plus extra codes for repeated lengths. The path lengths of the + * precode precede the path lengths of the larger code and are uncompressed, + * consisting of 20 entries of 4 bits each. + * + * @out: Bitstream to write the code to. + * @lens: The code lengths for the Huffman code, indexed by symbol. + * @prev_lens: Code lengths for this Huffman code, indexed by symbol, + * in the *previous block*, or all zeroes if this is the + * first block. + * @num_syms: The number of symbols in the code. + */ +static void +lzx_write_compressed_code(struct output_bitstream *out, + const u8 lens[restrict], + const u8 prev_lens[restrict], + unsigned num_syms) +{ + freq_t precode_freqs[LZX_PRETREE_NUM_SYMBOLS]; + u8 output_syms[num_syms]; + u8 precode_lens[LZX_PRETREE_NUM_SYMBOLS]; + u16 precode_codewords[LZX_PRETREE_NUM_SYMBOLS]; + unsigned i; + unsigned num_output_syms; + u8 precode_sym; + + num_output_syms = lzx_build_precode(lens, + prev_lens, + num_syms, + precode_freqs, + output_syms, + precode_lens, + precode_codewords, + NULL); + + /* Write the lengths of the precode codes to the output. */ for (i = 0; i < LZX_PRETREE_NUM_SYMBOLS; i++) - bitstream_put_bits(out, pretree_lens[i], + bitstream_put_bits(out, precode_lens[i], LZX_PRETREE_ELEMENT_SIZE); - /* Write the length symbols, encoded with the pretree, to the output. */ + /* Write the length symbols, encoded with the precode, to the output. */ - i = 0; - while (i < output_syms_idx) { - pretree_sym = output_syms[i++]; + for (i = 0; i < num_output_syms; ) { + precode_sym = output_syms[i++]; - bitstream_put_bits(out, pretree_codewords[pretree_sym], - pretree_lens[pretree_sym]); - switch (pretree_sym) { + bitstream_put_bits(out, precode_codewords[precode_sym], + precode_lens[precode_sym]); + switch (precode_sym) { case 17: bitstream_put_bits(out, output_syms[i++], 4); break; @@ -554,47 +797,1684 @@ 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. */ +/* + * Writes all compressed matches and literal bytes in a LZX block to the the + * output bitstream. + * + * @ostream + * The output bitstream. + * @block_type + * The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM). + * @match_tab + * The array of matches/literals that will be output (length @match_count). + * @match_count + * Number of matches/literals to be output. + * @codes + * Pointer to a structure that contains the codewords for the main, length, + * and aligned offset Huffman codes. + */ static void -lzx_make_huffman_codes(const struct lzx_freq_tables *freq_tabs, - struct lzx_codes *codes) +lzx_write_matches_and_literals(struct output_bitstream *ostream, + int block_type, + const struct lzx_match match_tab[], + unsigned match_count, + const struct lzx_codes *codes) { - make_canonical_huffman_code(LZX_MAINTREE_NUM_SYMBOLS, - LZX_MAX_CODEWORD_LEN, - freq_tabs->main_freq_table, - codes->main_lens, - codes->main_codewords); + for (unsigned i = 0; i < match_count; i++) { + struct lzx_match match = match_tab[i]; - make_canonical_huffman_code(LZX_LENTREE_NUM_SYMBOLS, - LZX_MAX_CODEWORD_LEN, - freq_tabs->len_freq_table, - codes->len_lens, - codes->len_codewords); + /* High bit of the match indicates whether the match is an + * actual match (1) or a literal uncompressed byte (0) */ + if (match.data & 0x80000000) { + /* match */ + lzx_write_match(ostream, block_type, + match, codes); + } else { + /* literal byte */ + bitstream_put_bits(ostream, + codes->codewords.main[match.data], + codes->lens.main[match.data]); + } + } +} - make_canonical_huffman_code(LZX_ALIGNEDTREE_NUM_SYMBOLS, 8, - freq_tabs->aligned_freq_table, - codes->aligned_lens, - codes->aligned_codewords); + +static void +lzx_assert_codes_valid(const struct lzx_codes * codes) +{ +#ifdef ENABLE_LZX_DEBUG + unsigned i; + + for (i = 0; i < LZX_MAINTREE_NUM_SYMBOLS; i++) + LZX_ASSERT(codes->lens.main[i] <= LZX_MAX_CODEWORD_LEN); + + for (i = 0; i < LZX_LENTREE_NUM_SYMBOLS; i++) + LZX_ASSERT(codes->lens.len[i] <= LZX_MAX_CODEWORD_LEN); + + for (i = 0; i < LZX_ALIGNEDTREE_NUM_SYMBOLS; i++) + LZX_ASSERT(codes->lens.aligned[i] <= 8); + + const unsigned tablebits = 10; + u16 decode_table[(1 << tablebits) + + (2 * max(LZX_MAINTREE_NUM_SYMBOLS, LZX_LENTREE_NUM_SYMBOLS))] + _aligned_attribute(DECODE_TABLE_ALIGNMENT); + LZX_ASSERT(0 == make_huffman_decode_table(decode_table, + LZX_MAINTREE_NUM_SYMBOLS, + tablebits, + codes->lens.main, + LZX_MAX_CODEWORD_LEN)); + LZX_ASSERT(0 == make_huffman_decode_table(decode_table, + LZX_LENTREE_NUM_SYMBOLS, + tablebits, + codes->lens.len, + LZX_MAX_CODEWORD_LEN)); + LZX_ASSERT(0 == make_huffman_decode_table(decode_table, + LZX_ALIGNEDTREE_NUM_SYMBOLS, + min(tablebits, 6), + codes->lens.aligned, + 8)); +#endif /* ENABLE_LZX_DEBUG */ } +/* Write a LZX aligned offset or verbatim block to the output. */ static void -do_call_insn_translation(u32 *call_insn_target, int input_pos, - int32_t file_size) +lzx_write_compressed_block(int block_type, + unsigned block_size, + struct lzx_match * chosen_matches, + unsigned num_chosen_matches, + const struct lzx_codes * codes, + const struct lzx_codes * prev_codes, + struct output_bitstream * ostream) { - int32_t abs_offset; - int32_t rel_offset; + unsigned i; + + LZX_ASSERT(block_type == LZX_BLOCKTYPE_ALIGNED || + block_type == LZX_BLOCKTYPE_VERBATIM); + LZX_ASSERT(block_size <= LZX_MAX_WINDOW_SIZE); + LZX_ASSERT(num_chosen_matches <= LZX_MAX_WINDOW_SIZE); + lzx_assert_codes_valid(codes); + + /* The first three bits indicate the type of block and are one of the + * LZX_BLOCKTYPE_* constants. */ + bitstream_put_bits(ostream, block_type, LZX_BLOCKTYPE_NBITS); + + /* The next bit indicates whether the block size is the default (32768), + * indicated by a 1 bit, or whether the block size is given by the next + * 16 bits, indicated by a 0 bit. */ + if (block_size == LZX_DEFAULT_BLOCK_SIZE) { + bitstream_put_bits(ostream, 1, 1); + } else { + bitstream_put_bits(ostream, 0, 1); + bitstream_put_bits(ostream, block_size, LZX_BLOCKSIZE_NBITS); + } + + /* Write out lengths of the main code. Note that the LZX specification + * incorrectly states that the aligned offset code comes after the + * length code, but in fact it is the very first tree to be written + * (before the main code). */ + if (block_type == LZX_BLOCKTYPE_ALIGNED) + for (i = 0; i < LZX_ALIGNEDTREE_NUM_SYMBOLS; i++) + bitstream_put_bits(ostream, codes->lens.aligned[i], + LZX_ALIGNEDTREE_ELEMENT_SIZE); + + LZX_DEBUG("Writing main code..."); + + /* Write the pre-tree and lengths for the first LZX_NUM_CHARS symbols in + * the main code, which are the codewords for literal bytes. */ + lzx_write_compressed_code(ostream, + codes->lens.main, + prev_codes->lens.main, + LZX_NUM_CHARS); + + /* Write the pre-tree and lengths for the rest of the main code, which + * are the codewords for match headers. */ + lzx_write_compressed_code(ostream, + codes->lens.main + LZX_NUM_CHARS, + prev_codes->lens.main + LZX_NUM_CHARS, + LZX_MAINTREE_NUM_SYMBOLS - LZX_NUM_CHARS); + + LZX_DEBUG("Writing length code..."); + + /* Write the pre-tree and lengths for the length code. */ + lzx_write_compressed_code(ostream, + codes->lens.len, + prev_codes->lens.len, + LZX_LENTREE_NUM_SYMBOLS); + + LZX_DEBUG("Writing matches and literals..."); + + /* Write the actual matches and literals. */ + lzx_write_matches_and_literals(ostream, block_type, + chosen_matches, num_chosen_matches, + codes); + + LZX_DEBUG("Done writing block."); +} + +/* Write the LZX block of index @block_number, or write its children recursively + * if it is a split block. + * + * @prev_codes is a pointer to the Huffman codes for the most recent block + * written, or all zeroes if this is the first block. + * + * Return a pointer to the Huffman codes for the last block written. */ +static struct lzx_codes * +lzx_write_block_recursive(struct lzx_compressor *ctx, + unsigned block_number, + struct lzx_codes * prev_codes, + struct output_bitstream *ostream) +{ + struct lzx_block_spec *spec = &ctx->block_specs[block_number - 1]; + + if (spec->is_split) { + prev_codes = lzx_write_block_recursive(ctx, block_number * 2 + 0, + prev_codes, ostream); + prev_codes = lzx_write_block_recursive(ctx, block_number * 2 + 1, + prev_codes, ostream); + } else { + LZX_DEBUG("Writing block #%u (type=%d, size=%u, num_chosen_matches=%u)...", + block_number, spec->block_type, spec->block_size, + spec->num_chosen_matches); + lzx_write_compressed_block(spec->block_type, + spec->block_size, + &ctx->chosen_matches[spec->chosen_matches_start_pos], + spec->num_chosen_matches, + &spec->codes, + prev_codes, + ostream); + prev_codes = &spec->codes; + } + return prev_codes; +} + +/* Write out the LZX blocks that were computed. */ +static void +lzx_write_all_blocks(struct lzx_compressor *ctx, struct output_bitstream *ostream) +{ + lzx_write_block_recursive(ctx, 1, &ctx->zero_codes, ostream); +} + +static u32 +lzx_record_literal(u8 literal, void *_freqs) +{ + struct lzx_freqs *freqs = _freqs; + + freqs->main[literal]++; + + return (u32)literal; +} + +/* Constructs a match from an offset and a length, and updates the LRU queue and + * the frequency of symbols in the main, length, and aligned offset alphabets. + * The return value is a 32-bit number that provides the match in an + * intermediate representation documented below. */ +static u32 +lzx_record_match(unsigned match_offset, unsigned match_len, + void *_freqs, void *_queue) +{ + struct lzx_freqs *freqs = _freqs; + struct lzx_lru_queue *queue = _queue; + unsigned position_slot; + unsigned position_footer = 0; + u32 len_header; + u32 len_pos_header; + unsigned len_footer; + unsigned adjusted_match_len; + + LZX_ASSERT(match_len >= LZX_MIN_MATCH && match_len <= LZX_MAX_MATCH); + + /* If possible, encode this offset as a repeated offset. */ + if (match_offset == queue->R0) { + position_slot = 0; + } else if (match_offset == queue->R1) { + swap(queue->R0, queue->R1); + position_slot = 1; + } else if (match_offset == queue->R2) { + swap(queue->R0, queue->R2); + position_slot = 2; + } else { + /* Not a repeated offset. */ + + /* offsets of 0, 1, and 2 are reserved for the repeated offset + * codes, so non-repeated offsets must be encoded as 3+. The + * minimum offset is 1, so encode the offsets offset by 2. */ + unsigned formatted_offset = match_offset + 2; + + queue->R2 = queue->R1; + queue->R1 = queue->R0; + queue->R0 = match_offset; + + /* The (now-formatted) offset will actually be encoded as a + * small position slot number that maps to a certain hard-coded + * offset (position base), followed by a number of extra bits--- + * the position footer--- that are added to the position base to + * get the original formatted offset. */ + + position_slot = lzx_get_position_slot(formatted_offset); + position_footer = formatted_offset & + ((1 << lzx_get_num_extra_bits(position_slot)) - 1); + } + + adjusted_match_len = match_len - LZX_MIN_MATCH; + + + /* The match length must be at least 2, so let the adjusted match length + * be the match length minus 2. + * + * If it is less than 7, the adjusted match length is encoded as a 3-bit + * number offset by 2. Otherwise, the 3-bit length header is all 1's + * and the actual adjusted length is given as a symbol encoded with the + * length tree, offset by 7. + */ + if (adjusted_match_len < LZX_NUM_PRIMARY_LENS) { + len_header = adjusted_match_len; + } else { + len_header = LZX_NUM_PRIMARY_LENS; + len_footer = adjusted_match_len - LZX_NUM_PRIMARY_LENS; + freqs->len[len_footer]++; + } + len_pos_header = (position_slot << 3) | len_header; + + freqs->main[len_pos_header + LZX_NUM_CHARS]++; + + /* Equivalent to: + * if (lzx_extra_bits[position_slot] >= 3) */ + if (position_slot >= 8) + freqs->aligned[position_footer & 7]++; + + /* Pack the position slot, position footer, and match length into an + * intermediate representation. + * + * bits description + * ---- ----------------------------------------------------------- + * + * 31 1 if a match, 0 if a literal. + * + * 30-25 position slot. This can be at most 50, so it will fit in 6 + * bits. + * + * 8-24 position footer. This is the offset of the real formatted + * offset from the position base. This can be at most 17 bits + * (since lzx_extra_bits[LZX_NUM_POSITION_SLOTS - 1] is 17). + * + * 0-7 length of match, offset by 2. This can be at most + * (LZX_MAX_MATCH - 2) == 255, so it will fit in 8 bits. */ + return 0x80000000 | + (position_slot << 25) | + (position_footer << 8) | + (adjusted_match_len); +} + +/* Set the cost model @ctx->costs from the Huffman codeword lengths specified in + * @lens. + * + * These are basically the same thing, except that the Huffman codewords with + * length 0 correspond to symbols with zero frequency that still need to be + * assigned actual costs. The specific values assigned are arbitrary, but they + * should be fairly high (near the maximum codeword length) to take into account + * the fact that uses of these symbols are expected to be rare. + */ +static void +lzx_set_costs(struct lzx_compressor * ctx, const struct lzx_lens * lens) +{ + unsigned i; + + memcpy(&ctx->costs, lens, sizeof(struct lzx_lens)); + + for (i = 0; i < LZX_MAINTREE_NUM_SYMBOLS; i++) + if (ctx->costs.main[i] == 0) + ctx->costs.main[i] = ctx->params.slow.main_nostat_cost; + + for (i = 0; i < LZX_LENTREE_NUM_SYMBOLS; i++) + if (ctx->costs.len[i] == 0) + ctx->costs.len[i] = ctx->params.slow.len_nostat_cost; + + for (i = 0; i < LZX_ALIGNEDTREE_NUM_SYMBOLS; i++) + if (ctx->costs.aligned[i] == 0) + ctx->costs.aligned[i] = ctx->params.slow.aligned_nostat_cost; +} + +static u32 +lzx_literal_cost(u8 c, const struct lzx_lens * costs) +{ + return costs->main[c]; +} + +/* Given a (length, offset) pair that could be turned into a valid LZX match as + * well as costs for the codewords in the main, length, and aligned Huffman + * codes, return the approximate number of bits it will take to represent this + * match in the compressed output. */ +static unsigned +lzx_match_cost(unsigned length, unsigned offset, const struct lzx_lens *costs + +#if LZX_PARAM_ACCOUNT_FOR_LRU + , struct lzx_lru_queue *queue +#endif + ) +{ + unsigned position_slot, len_header, main_symbol; + unsigned cost = 0; + + /* Calculate position slot and length header, then combine them into the + * main symbol. */ + +#if LZX_PARAM_ACCOUNT_FOR_LRU + if (offset == queue->R0) { + position_slot = 0; + } else if (offset == queue->R1) { + swap(queue->R0, queue->R1); + position_slot = 1; + } else if (offset == queue->R2) { + swap(queue->R0, queue->R2); + position_slot = 2; + } else +#endif + position_slot = lzx_get_position_slot(offset + 2); + + len_header = min(length - LZX_MIN_MATCH, LZX_NUM_PRIMARY_LENS); + main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS; + + /* Account for main symbol. */ + cost += costs->main[main_symbol]; + + /* Account for extra position information. */ + unsigned num_extra_bits = lzx_get_num_extra_bits(position_slot); + if (num_extra_bits >= 3) { + cost += num_extra_bits - 3; + cost += costs->aligned[(offset + LZX_MIN_MATCH) & 7]; + } else { + cost += num_extra_bits; + } + + /* Account for extra length information. */ + if (length - LZX_MIN_MATCH >= LZX_NUM_PRIMARY_LENS) + cost += costs->len[length - LZX_MIN_MATCH - LZX_NUM_PRIMARY_LENS]; + + return cost; +} + +/* This procedure effectively creates a new binary tree corresponding to the + * current string at the same time that it searches the existing tree nodes for + * matches. This is the same algorithm as that used in GetMatchesSpec1() in + * 7-Zip, but it is hopefully explained a little more clearly below. */ +static unsigned +lzx_lz_get_matches(const u8 window[restrict], + const unsigned bytes_remaining, + const unsigned strstart, + const unsigned max_length, + u16 child_tab[restrict], + unsigned cur_match, + const unsigned prev_len, + struct raw_match * const matches) +{ + u16 *new_tree_lt_ptr = &child_tab[strstart * 2]; + u16 *new_tree_gt_ptr = &child_tab[strstart * 2 + 1]; + + u16 longest_lt_match_len = 0; + u16 longest_gt_match_len = 0; + + /* Maximum number of nodes to walk down before stopping */ + unsigned depth = max_length; + + /* Length of longest match found so far */ + unsigned longest_match_len = prev_len; + + /* Maximum length of match to return */ + unsigned len_limit = min(bytes_remaining, max_length); + + /* Number of matches found so far */ + unsigned num_matches = 0; + + for (;;) { + + /* Stop if too many nodes were traversed or if there is no next + * node */ + if (depth-- == 0 || cur_match == 0) { + *new_tree_gt_ptr = 0; + *new_tree_lt_ptr = 0; + return num_matches; + } + + /* Load the pointers to the children of the binary tree node + * corresponding to the current match */ + u16 * const cur_match_ptrs = &child_tab[cur_match * 2]; + + /* Set up pointers to the current match and to the current + * string */ + const u8 * const matchptr = &window[cur_match]; + const u8 * const strptr = &window[strstart]; + + /* Determine position at which to start comparing */ + u16 len = min(longest_lt_match_len, + longest_gt_match_len); + + if (matchptr[len] == strptr[len]) { + + /* Extend the match as far as possible. */ + while (++len != len_limit) + if (matchptr[len] != strptr[len]) + break; + + /* Record this match if it is the longest found so far. + */ + if (len > longest_match_len) { + longest_match_len = len; + matches[num_matches].len = len; + matches[num_matches].offset = strstart - cur_match; + num_matches++; + + if (len == len_limit) { + /* Length limit was reached. Link left pointer + * in the new tree with left subtree of current + * match tree, and link the right pointer in the + * new tree with the right subtree of the + * current match tree. This in effect deletes + * the node for the currrent match, which is + * desirable because the current match is the + * same as the current string up until the + * length limit, so in subsequent queries it + * will never be preferable to the current + * position. */ + *new_tree_lt_ptr = cur_match_ptrs[0]; + *new_tree_gt_ptr = cur_match_ptrs[1]; + return num_matches; + } + } + } + + if (matchptr[len] < strptr[len]) { + /* Case 1: The current match is lexicographically less + * than the current string. + * + * Since we are searching the binary tree structures, we + * need to walk down to the *right* subtree of the + * current match's node to get to a match that is + * lexicographically *greater* than the current match + * but still lexicographically *lesser* than the current + * string. + * + * At the same time, we link the entire binary tree + * corresponding to the current match into the + * appropriate place in the new binary tree being built + * for the current string. */ + *new_tree_lt_ptr = cur_match; + new_tree_lt_ptr = &cur_match_ptrs[1]; + cur_match = *new_tree_lt_ptr; + longest_lt_match_len = len; + } else { + /* Case 2: The current match is lexicographically + * greater than the current string. + * + * This is analogous to Case 1 above, but everything + * happens in the other direction. + */ + *new_tree_gt_ptr = cur_match; + new_tree_gt_ptr = &cur_match_ptrs[0]; + cur_match = *new_tree_gt_ptr; + longest_gt_match_len = len; + } + } +} + +/* Equivalent to lzx_lz_get_matches(), but only updates the tree and doesn't + * return matches. See that function for details (including comments). */ +static void +lzx_lz_skip_matches(const u8 window[restrict], + const unsigned bytes_remaining, + const unsigned strstart, + const unsigned max_length, + u16 child_tab[restrict], + unsigned cur_match, + const unsigned prev_len) +{ + u16 *new_tree_lt_ptr = &child_tab[strstart * 2]; + u16 *new_tree_gt_ptr = &child_tab[strstart * 2 + 1]; + + u16 longest_lt_match_len = 0; + u16 longest_gt_match_len = 0; + + unsigned depth = max_length; + + unsigned longest_match_len = prev_len; + + unsigned len_limit = min(bytes_remaining, max_length); + + for (;;) { + if (depth-- == 0 || cur_match == 0) { + *new_tree_gt_ptr = 0; + *new_tree_lt_ptr = 0; + return; + } + + u16 * const cur_match_ptrs = &child_tab[cur_match * 2]; + + const u8 * const matchptr = &window[cur_match]; + const u8 * const strptr = &window[strstart]; + + u16 len = min(longest_lt_match_len, + longest_gt_match_len); + + if (matchptr[len] == strptr[len]) { + while (++len != len_limit) + if (matchptr[len] != strptr[len]) + break; + + if (len > longest_match_len) { + longest_match_len = len; + + if (len == len_limit) { + *new_tree_lt_ptr = cur_match_ptrs[0]; + *new_tree_gt_ptr = cur_match_ptrs[1]; + return; + } + } + } + + if (matchptr[len] < strptr[len]) { + *new_tree_lt_ptr = cur_match; + new_tree_lt_ptr = &cur_match_ptrs[1]; + cur_match = *new_tree_lt_ptr; + longest_lt_match_len = len; + } else { + *new_tree_gt_ptr = cur_match; + new_tree_gt_ptr = &cur_match_ptrs[0]; + cur_match = *new_tree_gt_ptr; + longest_gt_match_len = len; + } + } +} + +static unsigned +lzx_lz_get_matches_caching(struct lzx_compressor *ctx, + struct raw_match **matches_ret); + +/* Tell the match-finder to skip the specified number of bytes (@n) in the + * input. */ +static void +lzx_lz_skip_bytes(struct lzx_compressor *ctx, unsigned n) +{ + +#if LZX_PARAM_DONT_SKIP_MATCHES + /* Option 1: Still cache the matches from the positions skipped. They + * will then be available in later passes. */ + struct raw_match *matches; + while (n--) + lzx_lz_get_matches_caching(ctx, &matches); +#else + /* Option 2: Mark the positions skipped as having no matches available, + * but we still need to update the binary tree in case subsequent + * positions have matches at the current position. */ + LZX_ASSERT(n <= ctx->match_window_end - ctx->match_window_pos); + if (ctx->matches_already_found) { + while (n--) { + LZX_ASSERT(ctx->cached_matches[ctx->cached_matches_pos].offset == + ctx->match_window_pos); + ctx->cached_matches_pos += ctx->cached_matches[ctx->cached_matches_pos].len + 1; + ctx->match_window_pos++; + } + } else { + while (n--) { + if (ctx->params.slow.use_len2_matches && + ctx->match_window_end - ctx->match_window_pos >= 2) { + unsigned c1 = ctx->window[ctx->match_window_pos]; + unsigned c2 = ctx->window[ctx->match_window_pos + 1]; + unsigned digram = c1 | (c2 << 8); + ctx->digram_tab[digram] = ctx->match_window_pos; + } + if (ctx->match_window_end - ctx->match_window_pos >= 3) { + unsigned hash; + unsigned cur_match; + + hash = lzx_lz_compute_hash(&ctx->window[ctx->match_window_pos]); + + cur_match = ctx->hash_tab[hash]; + ctx->hash_tab[hash] = ctx->match_window_pos; + + lzx_lz_skip_matches(ctx->window, + ctx->match_window_end - ctx->match_window_pos, + ctx->match_window_pos, + ctx->params.slow.num_fast_bytes, + ctx->child_tab, + cur_match, 1); + } + ctx->cached_matches[ctx->cached_matches_pos].len = 0; + ctx->cached_matches[ctx->cached_matches_pos].offset = ctx->match_window_pos; + ctx->cached_matches_pos++; + ctx->match_window_pos++; + } + } +#endif /* !LZX_PARAM_DONT_SKIP_MATCHES */ +} + +/* Retrieve a list of matches available at the next position in the input. + * + * The return value is the number of matches found, and a pointer to them is + * written to @matches_ret. The matches will be sorted in order by length. + * + * This is essentially a wrapper around lzx_lz_get_matches() that caches its + * output the first time and also performs the needed hashing. + */ +static unsigned +lzx_lz_get_matches_caching(struct lzx_compressor *ctx, + struct raw_match **matches_ret) +{ + unsigned num_matches; + struct raw_match *matches; + + LZX_ASSERT(ctx->match_window_end >= ctx->match_window_pos); + + matches = &ctx->cached_matches[ctx->cached_matches_pos + 1]; + + if (ctx->matches_already_found) { + num_matches = ctx->cached_matches[ctx->cached_matches_pos].len; + LZX_ASSERT(ctx->cached_matches[ctx->cached_matches_pos].offset == ctx->match_window_pos); + + for (int i = (int)num_matches - 1; i >= 0; i--) { + if (ctx->match_window_pos + matches[i].len > ctx->match_window_end) + matches[i].len = ctx->match_window_end - ctx->match_window_pos; + else + break; + } + } else { + unsigned prev_len = 1; + struct raw_match * matches_ret = &ctx->cached_matches[ctx->cached_matches_pos + 1]; + num_matches = 0; + + if (ctx->params.slow.use_len2_matches && + ctx->match_window_end - ctx->match_window_pos >= 3) { + unsigned c1 = ctx->window[ctx->match_window_pos]; + unsigned c2 = ctx->window[ctx->match_window_pos + 1]; + unsigned digram = c1 | (c2 << 8); + unsigned cur_match; + + cur_match = ctx->digram_tab[digram]; + ctx->digram_tab[digram] = ctx->match_window_pos; + if (cur_match != 0 && + ctx->window[cur_match + 2] != ctx->window[ctx->match_window_pos + 2]) + { + matches_ret->len = 2; + matches_ret->offset = ctx->match_window_pos - cur_match; + matches_ret++; + num_matches++; + prev_len = 2; + } + } + if (ctx->match_window_end - ctx->match_window_pos >= 3) { + unsigned hash; + unsigned cur_match; + + hash = lzx_lz_compute_hash(&ctx->window[ctx->match_window_pos]); + + cur_match = ctx->hash_tab[hash]; + ctx->hash_tab[hash] = ctx->match_window_pos; + num_matches += lzx_lz_get_matches(ctx->window, + ctx->match_window_end - ctx->match_window_pos, + ctx->match_window_pos, + ctx->params.slow.num_fast_bytes, + ctx->child_tab, + cur_match, + prev_len, + matches_ret); + } + + ctx->cached_matches[ctx->cached_matches_pos].len = num_matches; + ctx->cached_matches[ctx->cached_matches_pos].offset = ctx->match_window_pos; + + if (num_matches) { + struct raw_match *longest_match_ptr = + &ctx->cached_matches[ctx->cached_matches_pos + 1 + + num_matches - 1]; + u16 len = longest_match_ptr->len; + + /* If the longest match returned by the match-finder + * reached the number of fast bytes, extend it as much + * as possible. */ + if (len == ctx->params.slow.num_fast_bytes) { + const unsigned maxlen = + min(ctx->match_window_end - ctx->match_window_pos, + LZX_MAX_MATCH); + + const u8 * const matchptr = + &ctx->window[ctx->match_window_pos - longest_match_ptr->offset]; + + const u8 * const strptr = + &ctx->window[ctx->match_window_pos]; + + while (len < maxlen && matchptr[len] == strptr[len]) + len++; + } + longest_match_ptr->len = len; + } + } + ctx->cached_matches_pos += num_matches + 1; + *matches_ret = matches; + +#if 0 + printf("\n"); + for (unsigned i = 0; i < num_matches; i++) + { + printf("Len %u Offset %u\n", matches[i].len, matches[i].offset); + } +#endif + + for (unsigned i = 0; i < num_matches; i++) { + LZX_ASSERT(matches[i].len <= LZX_MAX_MATCH); + if (matches[i].len >= LZX_MIN_MATCH) { + LZX_ASSERT(matches[i].offset <= ctx->match_window_pos); + LZX_ASSERT(matches[i].len <= ctx->match_window_end - ctx->match_window_pos); + LZX_ASSERT(!memcmp(&ctx->window[ctx->match_window_pos], + &ctx->window[ctx->match_window_pos - matches[i].offset], + matches[i].len)); + } + } + + ctx->match_window_pos++; + return num_matches; +} + +/* + * Reverse the linked list of near-optimal matches so that they can be returned + * in forwards order. + * + * Returns the first match in the list. + */ +static struct raw_match +lzx_lz_reverse_near_optimal_match_list(struct lzx_compressor *ctx, + unsigned cur_pos) +{ + unsigned prev_link, saved_prev_link; + unsigned prev_match_offset, saved_prev_match_offset; + + ctx->optimum_end_idx = cur_pos; + + saved_prev_link = ctx->optimum[cur_pos].prev.link; + saved_prev_match_offset = ctx->optimum[cur_pos].prev.match_offset; + + do { + prev_link = saved_prev_link; + prev_match_offset = saved_prev_match_offset; + + saved_prev_link = ctx->optimum[prev_link].prev.link; + saved_prev_match_offset = ctx->optimum[prev_link].prev.match_offset; + + ctx->optimum[prev_link].next.link = cur_pos; + ctx->optimum[prev_link].next.match_offset = prev_match_offset; + + cur_pos = prev_link; + } while (cur_pos != 0); + + ctx->optimum_cur_idx = ctx->optimum[0].next.link; + + return (struct raw_match) + { .len = ctx->optimum_cur_idx, + .offset = ctx->optimum[0].next.match_offset, + }; +} + +/* + * lzx_lz_get_near_optimal_match() - + * + * Choose the "best" match or literal to use at the next position in the input. + * + * Unlike a "greedy" parser that always takes the longest match, or even a + * parser with one match/literal look-ahead like zlib, the algorithm used here + * may look ahead many matches/literals to determine the best match/literal to + * output next. The motivation is that the compression ratio is improved if the + * compressor can do things like use a shorter-than-possible match in order to + * allow a longer match later, and also take into account the Huffman code cost + * model rather than simply assuming that longer is better. It is not a true + * "optimal" parser, however, since some shortcuts can be taken; for example, if + * a match is very long, the parser just chooses it immediately before too much + * time is wasting considering many different alternatives that are unlikely to + * be better. + * + * This algorithm is based on that used in 7-Zip's DEFLATE encoder. + * + * Each call to this function does one of two things: + * + * 1. Build a near-optimal sequence of matches/literals, up to some point, that + * will be returned by subsequent calls to this function, then return the + * first one. + * + * OR + * + * 2. Return the next match/literal previously computed by a call to this + * function; + * + * This function relies on the following state in the compressor context: + * + * ctx->window (read-only: preprocessed data being compressed) + * ctx->cost (read-only: cost model to use) + * ctx->optimum (internal state; leave uninitialized) + * ctx->optimum_cur_idx (must set to 0 before first call) + * ctx->optimum_end_idx (must set to 0 before first call) + * ctx->hash_tab (must set to 0 before first call) + * ctx->cached_matches (internal state; leave uninitialized) + * ctx->cached_matches_pos (initialize to 0 before first call; save and + * restore value if restarting parse from a + * certain position) + * ctx->match_window_pos (must initialize to position of next match to + * return; subsequent calls return subsequent + * matches) + * ctx->match_window_end (must initialize to limit of match-finding region; + * subsequent calls use the same limit) + * + * The return value is a (length, offset) pair specifying the match or literal + * chosen. For literals, length is either 0 or 1 and offset is meaningless. + */ +static struct raw_match +lzx_lz_get_near_optimal_match(struct lzx_compressor * ctx) +{ +#if 0 + /* Testing: literals only */ + ctx->match_window_pos++; + return (struct raw_match) { .len = 0 }; +#elif 0 + /* Testing: greedy parsing */ + struct raw_match *matches; + unsigned num_matches; + struct raw_match match = {.len = 0}; + + num_matches = lzx_lz_get_matches_caching(ctx, &matches); + if (num_matches) { + match = matches[num_matches - 1]; + lzx_lz_skip_bytes(ctx, match.len - 1); + } + return match; +#else + unsigned num_possible_matches; + struct raw_match *possible_matches; + struct raw_match match; + unsigned longest_match_len; + unsigned len, match_idx; + + if (ctx->optimum_cur_idx != ctx->optimum_end_idx) { + /* Case 2: Return the next match/literal already found. */ + match.len = ctx->optimum[ctx->optimum_cur_idx].next.link - + ctx->optimum_cur_idx; + match.offset = ctx->optimum[ctx->optimum_cur_idx].next.match_offset; + + ctx->optimum_cur_idx = ctx->optimum[ctx->optimum_cur_idx].next.link; + return match; + } + + /* Case 1: Compute a new list of matches/literals to return. */ + + ctx->optimum_cur_idx = 0; + ctx->optimum_end_idx = 0; + + /* Get matches at this position. */ + num_possible_matches = lzx_lz_get_matches_caching(ctx, &possible_matches); + + /* If no matches found, return literal. */ + if (num_possible_matches == 0) + return (struct raw_match){ .len = 0 }; + + /* The matches that were found are sorted by length. Get the length of + * the longest one. */ + longest_match_len = possible_matches[num_possible_matches - 1].len; + + /* Greedy heuristic: if the longest match that was found is greater + * than the number of fast bytes, return it immediately; don't both + * doing more work. */ + if (longest_match_len > ctx->params.slow.num_fast_bytes) { + lzx_lz_skip_bytes(ctx, longest_match_len - 1); + return possible_matches[num_possible_matches - 1]; + } + + /* Calculate the cost to reach the next position by outputting a + * literal. */ +#if LZX_PARAM_ACCOUNT_FOR_LRU + ctx->optimum[0].queue = ctx->queue; + ctx->optimum[1].queue = ctx->optimum[0].queue; +#endif + ctx->optimum[1].cost = lzx_literal_cost(ctx->window[ctx->match_window_pos], + &ctx->costs); + ctx->optimum[1].prev.link = 0; + + /* Calculate the cost to reach any position up to and including that + * reached by the longest match, using the shortest (i.e. closest) match + * that reaches each position. */ + match_idx = 0; + BUILD_BUG_ON(LZX_MIN_MATCH != 2); + for (len = LZX_MIN_MATCH; len <= longest_match_len; len++) { + + LZX_ASSERT(match_idx < num_possible_matches); + + #if LZX_PARAM_ACCOUNT_FOR_LRU + ctx->optimum[len].queue = ctx->optimum[0].queue; + #endif + ctx->optimum[len].prev.link = 0; + ctx->optimum[len].prev.match_offset = possible_matches[match_idx].offset; + ctx->optimum[len].cost = lzx_match_cost(len, + possible_matches[match_idx].offset, + &ctx->costs + #if LZX_PARAM_ACCOUNT_FOR_LRU + , &ctx->optimum[len].queue + #endif + ); + if (len == possible_matches[match_idx].len) + match_idx++; + } + + unsigned cur_pos = 0; + + /* len_end: greatest index forward at which costs have been calculated + * so far */ + unsigned len_end = longest_match_len; + + + for (;;) { + /* Advance to next position. */ + cur_pos++; + + if (cur_pos == len_end || cur_pos == LZX_PARAM_OPTIM_ARRAY_SIZE) + return lzx_lz_reverse_near_optimal_match_list(ctx, cur_pos); + + /* retrieve the number of matches available at this position */ + num_possible_matches = lzx_lz_get_matches_caching(ctx, + &possible_matches); + + unsigned new_len = 0; + + if (num_possible_matches != 0) { + new_len = possible_matches[num_possible_matches - 1].len; + + /* Greedy heuristic: if we found a match greater than + * the number of fast bytes, stop immediately. */ + if (new_len > ctx->params.slow.num_fast_bytes) { + + /* Build the list of matches to return and get + * the first one. */ + match = lzx_lz_reverse_near_optimal_match_list(ctx, cur_pos); + + /* Append the long match to the end of the list. */ + ctx->optimum[cur_pos].next.match_offset = + possible_matches[num_possible_matches - 1].offset; + ctx->optimum[cur_pos].next.link = cur_pos + new_len; + ctx->optimum_end_idx = cur_pos + new_len; + + /* Skip over the remaining bytes of the long match. */ + lzx_lz_skip_bytes(ctx, new_len - 1); + + /* Return first match in the list */ + return match; + } + } + + /* Consider proceeding with a literal byte. */ + u32 cur_cost = ctx->optimum[cur_pos].cost; + u32 cur_plus_literal_cost = cur_cost + + lzx_literal_cost(ctx->window[ctx->match_window_pos - 1], + &ctx->costs); + if (cur_plus_literal_cost < ctx->optimum[cur_pos + 1].cost) { + ctx->optimum[cur_pos + 1].cost = cur_plus_literal_cost; + ctx->optimum[cur_pos + 1].prev.link = cur_pos; + #if LZX_PARAM_ACCOUNT_FOR_LRU + ctx->optimum[cur_pos + 1].queue = ctx->optimum[cur_pos].queue; + #endif + } + + if (num_possible_matches == 0) + continue; + + /* Consider proceeding with a match. */ + + while (len_end < cur_pos + new_len) + ctx->optimum[++len_end].cost = ~(u32)0; + + match_idx = 0; + for (len = LZX_MIN_MATCH; len <= new_len; len++) { + LZX_ASSERT(match_idx < num_possible_matches); + #if LZX_PARAM_ACCOUNT_FOR_LRU + struct lzx_lru_queue q = ctx->optimum[cur_pos].queue; + #endif + u32 cost = cur_cost + lzx_match_cost(len, + possible_matches[match_idx].offset, + &ctx->costs + #if LZX_PARAM_ACCOUNT_FOR_LRU + , &q + #endif + ); + + if (cost < ctx->optimum[cur_pos + len].cost) { + ctx->optimum[cur_pos + len].cost = cost; + ctx->optimum[cur_pos + len].prev.link = cur_pos; + ctx->optimum[cur_pos + len].prev.match_offset = + possible_matches[match_idx].offset; + #if LZX_PARAM_ACCOUNT_FOR_LRU + ctx->optimum[cur_pos + len].queue = q; + #endif + } + + if (len == possible_matches[match_idx].len) + match_idx++; + } + } +#endif +} + +static unsigned +lzx_huffman_code_output_cost(const u8 lens[restrict], + const freq_t freqs[restrict], + unsigned num_syms) +{ + unsigned cost = 0; + + for (unsigned i = 0; i < num_syms; i++) + cost += (unsigned)lens[i] * (unsigned)freqs[i]; + + return cost; +} + +/* Return the number of bits required to output the lengths for the specified + * Huffman code in compressed format (encoded with a precode). */ +static unsigned +lzx_code_cost(const u8 lens[], const u8 prev_lens[], unsigned num_syms) +{ + u8 output_syms[num_syms]; + freq_t precode_freqs[LZX_PRETREE_NUM_SYMBOLS]; + u8 precode_lens[LZX_PRETREE_NUM_SYMBOLS]; + u16 precode_codewords[LZX_PRETREE_NUM_SYMBOLS]; + unsigned cost = 0; + unsigned num_additional_bits; + + /* Acount for the lengths of the precode itself. */ + cost += LZX_PRETREE_NUM_SYMBOLS * LZX_PRETREE_ELEMENT_SIZE; + + lzx_build_precode(lens, prev_lens, num_syms, + precode_freqs, output_syms, + precode_lens, precode_codewords, + &num_additional_bits); + + /* Account for all precode symbols output. */ + cost += lzx_huffman_code_output_cost(precode_lens, precode_freqs, + LZX_PRETREE_NUM_SYMBOLS); + + /* Account for additional bits. */ + cost += num_additional_bits; + + return cost; +} + +/* Account for extra bits in the main symbols. */ +static void +lzx_update_mainsym_match_costs(int block_type, + u8 main_lens[LZX_MAINTREE_NUM_SYMBOLS]) +{ + unsigned i; + + LZX_ASSERT(block_type == LZX_BLOCKTYPE_ALIGNED || + block_type == LZX_BLOCKTYPE_VERBATIM); + + for (i = LZX_NUM_CHARS; i < LZX_MAINTREE_NUM_SYMBOLS; i++) { + unsigned position_slot = (i >> 3) & 0x1f; + + /* If it's a verbatim block, add the number of extra bits + * corresponding to the position slot. + * + * If it's an aligned block and there would normally be at least + * 3 extra bits, count 3 less because they will be output as an + * aligned offset symbol instead. */ + unsigned num_extra_bits = lzx_get_num_extra_bits(position_slot); + + if (block_type == LZX_BLOCKTYPE_ALIGNED && num_extra_bits >= 3) + num_extra_bits -= 3; + main_lens[i] += num_extra_bits; + } +} + +/* + * Compute the costs, in bits, to output a compressed block as aligned offset + * and verbatim. + * + * @block_size + * Number of bytes of uncompressed data the block represents. + * @codes + * Huffman codes that will be used when outputting the block. + * @prev_codes + * Huffman codes for the previous block, or all zeroes if this is the first + * block. + * @freqs + * Frequencies of Huffman symbols that will be output in the block. + * @aligned_cost_ret + * Cost of aligned block will be returned here. + * @verbatim_cost_ret + * Cost of verbatim block will be returned here. + */ +static void +lzx_compute_compressed_block_costs(unsigned block_size, + const struct lzx_codes *codes, + const struct lzx_codes *prev_codes, + const struct lzx_freqs *freqs, + unsigned * aligned_cost_ret, + unsigned * verbatim_cost_ret) +{ + unsigned common_cost = 0; + unsigned aligned_cost = 0; + unsigned verbatim_cost = 0; + + u8 updated_main_lens[LZX_MAINTREE_NUM_SYMBOLS]; + + /* Account for cost of block header. */ + common_cost += LZX_BLOCKTYPE_NBITS; + if (block_size == LZX_DEFAULT_BLOCK_SIZE) + common_cost += 1; + else + common_cost += LZX_BLOCKSIZE_NBITS; + + /* Account for cost of outputting aligned offset code. */ + aligned_cost += LZX_ALIGNEDTREE_NUM_SYMBOLS * LZX_ALIGNEDTREE_ELEMENT_SIZE; + + /* Account for cost of outputting main and length codes. */ + common_cost += lzx_code_cost(codes->lens.main, + prev_codes->lens.main, + LZX_NUM_CHARS); + common_cost += lzx_code_cost(codes->lens.main + LZX_NUM_CHARS, + prev_codes->lens.main + LZX_NUM_CHARS, + LZX_MAINTREE_NUM_SYMBOLS - LZX_NUM_CHARS); + common_cost += lzx_code_cost(codes->lens.len, + prev_codes->lens.len, + LZX_LENTREE_NUM_SYMBOLS); + + /* Account for cost to output main, length, and aligned symbols, taking + * into account extra position bits. */ + + memcpy(updated_main_lens, codes->lens.main, LZX_MAINTREE_NUM_SYMBOLS); + lzx_update_mainsym_match_costs(LZX_BLOCKTYPE_VERBATIM, updated_main_lens); + verbatim_cost += lzx_huffman_code_output_cost(updated_main_lens, + freqs->main, + LZX_MAINTREE_NUM_SYMBOLS); + memcpy(updated_main_lens, codes->lens.main, LZX_MAINTREE_NUM_SYMBOLS); + lzx_update_mainsym_match_costs(LZX_BLOCKTYPE_ALIGNED, updated_main_lens); + aligned_cost += lzx_huffman_code_output_cost(updated_main_lens, + freqs->main, + LZX_MAINTREE_NUM_SYMBOLS); + + common_cost += lzx_huffman_code_output_cost(codes->lens.len, + freqs->len, + LZX_LENTREE_NUM_SYMBOLS); + + aligned_cost += lzx_huffman_code_output_cost(codes->lens.aligned, + freqs->aligned, + LZX_ALIGNEDTREE_NUM_SYMBOLS); + + *aligned_cost_ret = aligned_cost + common_cost; + *verbatim_cost_ret = verbatim_cost + common_cost; +} + +/* Prepare a (nonsplit) compressed block. */ +static unsigned +lzx_prepare_compressed_block(struct lzx_compressor *ctx, unsigned block_number, + struct lzx_codes *prev_codes) +{ + struct lzx_block_spec *spec = &ctx->block_specs[block_number - 1]; + unsigned orig_cached_matches_pos = ctx->cached_matches_pos; + struct lzx_lru_queue orig_queue = ctx->queue; + struct lzx_freqs freqs; + unsigned cost; + + /* Here's where the real work happens. The following loop runs one or + * more times, each time using a cost model based on the Huffman codes + * computed from the previous iteration (the first iteration uses a + * default model). Each iteration of the loop uses a heuristic + * algorithm to divide the block into near-optimal matches/literals from + * beginning to end. */ + LZX_ASSERT(ctx->params.slow.num_optim_passes >= 1); + spec->num_chosen_matches = 0; + for (unsigned pass = 0; pass < ctx->params.slow.num_optim_passes; pass++) + { + LZX_DEBUG("Block %u: Match-choosing pass %u of %u", + block_number, pass + 1, + ctx->params.slow.num_optim_passes); + + /* Reset frequency tables. */ + memset(&freqs, 0, sizeof(freqs)); + + /* Reset match offset LRU queue. */ + ctx->queue = orig_queue; + + /* Reset match-finding position. */ + ctx->cached_matches_pos = orig_cached_matches_pos; + ctx->match_window_pos = spec->window_pos; + ctx->match_window_end = spec->window_pos + spec->block_size; + + /* Set cost model. */ + lzx_set_costs(ctx, &spec->codes.lens); + + unsigned window_pos = spec->window_pos; + unsigned end = window_pos + spec->block_size; + + while (window_pos < end) { + struct raw_match match; + struct lzx_match lzx_match; + + match = lzx_lz_get_near_optimal_match(ctx); + + if (match.len >= LZX_MIN_MATCH) { + + /* Best to output a match here. */ + + LZX_ASSERT(match.len <= LZX_MAX_MATCH); + LZX_ASSERT(!memcmp(&ctx->window[window_pos], + &ctx->window[window_pos - match.offset], + match.len)); + + /* Tally symbol frequencies. */ + lzx_match.data = lzx_record_match(match.offset, + match.len, + &freqs, + &ctx->queue); + + window_pos += match.len; + } else { + /* Best to output a literal here. */ + + /* Tally symbol frequencies. */ + lzx_match.data = lzx_record_literal(ctx->window[window_pos], + &freqs); + + window_pos += 1; + } + + /* If it's the last pass, save the match/literal in + * intermediate form. */ + if (pass == ctx->params.slow.num_optim_passes - 1) { + ctx->chosen_matches[spec->chosen_matches_start_pos + + spec->num_chosen_matches] = lzx_match; + + spec->num_chosen_matches++; + } + } + LZX_ASSERT(window_pos == end); + + /* Build Huffman codes using the new frequencies. */ + lzx_make_huffman_codes(&freqs, &spec->codes); + + /* The first time we get here is when the full input has been + * processed, so the match-finding is done. */ + ctx->matches_already_found = true; + } + + LZX_DEBUG("Block %u: saved %u matches/literals @ %u", + block_number, spec->num_chosen_matches, + spec->chosen_matches_start_pos); + + unsigned aligned_cost; + unsigned verbatim_cost; + + lzx_compute_compressed_block_costs(spec->block_size, + &spec->codes, + prev_codes, + &freqs, + &aligned_cost, + &verbatim_cost); + + /* Choose whether to make the block aligned offset or verbatim. */ + if (aligned_cost < verbatim_cost) { + spec->block_type = LZX_BLOCKTYPE_ALIGNED; + cost = aligned_cost; + LZX_DEBUG("Using aligned block (cost %u vs %u for verbatim)", + aligned_cost, verbatim_cost); + } else { + spec->block_type = LZX_BLOCKTYPE_VERBATIM; + cost = verbatim_cost; + LZX_DEBUG("Using verbatim block (cost %u vs %u for aligned)", + verbatim_cost, aligned_cost); + } + + LZX_DEBUG("Block %u is %u => %u bytes unsplit.", + block_number, spec->block_size, cost / 8); + + return cost; +} + +/* + * lzx_prepare_block_recursive() - + * + * Given a (possibly nonproper) sub-sequence of the preprocessed input, compute + * the LZX block(s) that it should be output as. + * + * This function initially considers the case where the given sub-sequence of + * the preprocessed input be output as a single block. This block is calculated + * and its cost (number of bits required to output it) is computed. + * + * Then, if @max_split_level is greater than zero, a split into two evenly sized + * subblocks is considered. The block is recursively split in this way, + * potentially up to the depth specified by @max_split_level. The cost of the + * split block is compared to the cost of the single block, and the lower cost + * solution is used. + * + * For each compressed output block computed, the sequence of matches/literals + * and the corresponding Huffman codes for the block are produced and saved. + * + * The return value is the approximate number of bits the block (or all + * subblocks, in the case that the split block had lower cost), will take up + * when written to the compressed output. + */ +static unsigned +lzx_prepare_block_recursive(struct lzx_compressor * ctx, + unsigned block_number, + unsigned max_split_level, + struct lzx_codes **prev_codes_p) +{ + struct lzx_block_spec *spec = &ctx->block_specs[block_number - 1]; + unsigned cost; + unsigned orig_cached_matches_pos; + struct lzx_lru_queue orig_queue, nonsplit_queue; + struct lzx_codes *prev_codes = *prev_codes_p; + + LZX_DEBUG("Preparing block %u...", block_number); + + /* Save positions of chosen and cached matches, and the match offset LRU + * queue, so that they can be restored if splitting is attempted. */ + orig_cached_matches_pos = ctx->cached_matches_pos; + orig_queue = ctx->queue; + + /* Consider outputting the input subsequence as a single block. */ + spec->is_split = 0; + cost = lzx_prepare_compressed_block(ctx, block_number, prev_codes); + nonsplit_queue = ctx->queue; + + *prev_codes_p = &spec->codes; + + /* If the maximum split level is at least one, consider splitting the + * block in two. */ + if (max_split_level--) { + + LZX_DEBUG("Calculating split of block %u...", block_number); + + struct lzx_block_spec *spec1, *spec2; + unsigned split_cost; + + ctx->cached_matches_pos = orig_cached_matches_pos; + ctx->queue = orig_queue; + + /* Prepare and get the cost of the first sub-block. */ + spec1 = &ctx->block_specs[block_number * 2 - 1]; + spec1->codes.lens = spec->codes.lens; + spec1->window_pos = spec->window_pos; + spec1->block_size = spec->block_size / 2; + spec1->chosen_matches_start_pos = spec->chosen_matches_start_pos + + LZX_MAX_WINDOW_SIZE; + split_cost = lzx_prepare_block_recursive(ctx, + block_number * 2, + max_split_level, + &prev_codes); + + /* Prepare and get the cost of the second sub-block. */ + spec2 = spec1 + 1; + spec2->codes.lens = spec->codes.lens; + spec2->window_pos = spec->window_pos + spec1->block_size; + spec2->block_size = spec->block_size - spec1->block_size; + spec2->chosen_matches_start_pos = spec1->chosen_matches_start_pos + + spec1->block_size; + split_cost += lzx_prepare_block_recursive(ctx, + block_number * 2 + 1, + max_split_level, + &prev_codes); + + /* Compare the cost of the whole block with that of the split + * block. Choose the lower cost solution. */ + if (split_cost < cost) { + LZX_DEBUG("Splitting block %u is worth it " + "(%u => %u bytes).", + block_number, cost / 8, split_cost / 8); + spec->is_split = 1; + cost = split_cost; + *prev_codes_p = prev_codes; + } else { + LZX_DEBUG("Splitting block %u is NOT worth it " + "(%u => %u bytes).", + block_number, cost / 8, split_cost / 8); + ctx->queue = nonsplit_queue; + } + } + + return cost; +} + +/* Empirical averages */ +static const u8 lzx_default_mainsym_costs[LZX_MAINTREE_NUM_SYMBOLS] = { + 7, 9, 9, 10, 9, 10, 10, 10, 9, 10, 9, 10, 10, 9, 10, 10, 9, 10, 10, 11, + 10, 10, 10, 11, 10, 11, 11, 11, 10, 11, 11, 11, 8, 11, 9, 10, 9, 10, 11, + 11, 9, 9, 11, 10, 10, 9, 9, 9, 8, 8, 8, 8, 8, 9, 9, 9, 8, 8, 9, 9, 9, 9, + 10, 10, 10, 8, 9, 8, 8, 8, 8, 9, 9, 9, 10, 10, 8, 8, 9, 9, 8, 10, 9, 8, + 8, 9, 8, 9, 9, 10, 10, 10, 9, 10, 11, 9, 10, 8, 9, 8, 8, 8, 8, 9, 8, 8, + 9, 9, 8, 8, 8, 8, 8, 10, 8, 8, 7, 8, 9, 9, 9, 9, 10, 11, 10, 10, 11, 11, + 10, 11, 11, 10, 10, 11, 11, 11, 10, 10, 11, 10, 11, 10, 11, 11, 10, 11, + 11, 12, 11, 11, 11, 12, 11, 11, 11, 11, 11, 11, 11, 12, 10, 11, 11, 11, + 11, 11, 11, 12, 11, 11, 11, 11, 11, 12, 11, 11, 10, 11, 11, 11, 11, 11, + 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, + 10, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 12, 11, 11, 10, 11, + 11, 11, 11, 12, 11, 11, 10, 11, 11, 11, 10, 12, 11, 11, 10, 10, 11, 10, + 10, 11, 11, 11, 10, 11, 11, 11, 10, 11, 11, 11, 10, 11, 11, 11, 10, 11, + 10, 9, 8, 7, 10, 10, 11, 10, 11, 7, 9, 9, 11, 11, 11, 12, 11, 9, 10, 10, + 12, 12, 13, 13, 12, 11, 10, 12, 12, 14, 14, 14, 13, 12, 9, 12, 13, 14, + 14, 14, 14, 14, 9, 10, 13, 14, 14, 14, 14, 14, 9, 9, 11, 11, 13, 13, 13, + 14, 9, 9, 11, 12, 12, 13, 13, 13, 8, 8, 11, 11, 12, 12, 12, 11, 9, 9, + 10, 11, 12, 12, 12, 11, 8, 9, 10, 10, 11, 12, 11, 10, 9, 9, 10, 11, 11, + 12, 11, 10, 8, 9, 10, 10, 11, 11, 11, 9, 9, 9, 10, 11, 11, 11, 11, 9, 8, + 8, 10, 10, 11, 11, 11, 9, 9, 9, 10, 10, 11, 11, 11, 9, 9, 8, 9, 10, 11, + 11, 11, 9, 10, 9, 10, 11, 11, 11, 11, 9, 14, 9, 9, 10, 10, 11, 10, 9, + 14, 9, 10, 11, 11, 11, 11, 9, 14, 9, 10, 10, 11, 11, 11, 9, 14, 10, 10, + 11, 11, 12, 11, 10, 14, 10, 10, 10, 11, 11, 11, 10, 14, 11, 11, 11, 11, + 12, 12, 10, 14, 10, 11, 11, 11, 12, 11, 10, 14, 11, 11, 11, 12, 12, 12, + 11, 15, 11, 11, 11, 12, 12, 12, 11, 14, 12, 12, 12, 12, 13, 12, 11, 15, + 12, 12, 12, 13, 13, 13, 12, 15, 14, 13, 14, 14, 14, 14, 13, +}; + +/* Empirical averages */ +static const u8 lzx_default_lensym_costs[LZX_LENTREE_NUM_SYMBOLS] = { + 5, 5, 5, 5, 5, 6, 5, 5, 6, 7, 7, 7, 8, 8, 7, 8, 9, 9, 9, 9, 10, 9, 9, + 10, 9, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 12, 12, 12, 11, 12, 12, + 12, 12, 12, 12, 13, 12, 12, 12, 13, 12, 13, 13, 12, 12, 13, 12, 13, 13, + 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 14, 13, 14, 13, 14, 13, + 14, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, + 14, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, + 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, + 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, + 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, + 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, + 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, + 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, + 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, + 14, 14, 14, 14, 14, 14, 14, 14, 14, 10, +}; + +/* + * Set default symbol costs. + */ +static void +lzx_set_default_costs(struct lzx_lens * lens) +{ + unsigned i; + +#if LZX_PARAM_USE_EMPIRICAL_DEFAULT_COSTS + memcpy(&lens->main, lzx_default_mainsym_costs, LZX_MAINTREE_NUM_SYMBOLS); + memcpy(&lens->len, lzx_default_lensym_costs, LZX_LENTREE_NUM_SYMBOLS); + +#else + /* Literal symbols */ + for (i = 0; i < LZX_NUM_CHARS; i++) + lens->main[i] = 8; + + /* Match header symbols */ + for (; i < LZX_MAINTREE_NUM_SYMBOLS; i++) + lens->main[i] = 10; + + /* Length symbols */ + for (i = 0; i < LZX_LENTREE_NUM_SYMBOLS; i++) + lens->len[i] = 8; +#endif + + /* Aligned offset symbols */ + for (i = 0; i < LZX_ALIGNEDTREE_NUM_SYMBOLS; i++) + lens->aligned[i] = 3; +} + +/* + * lzx_prepare_blocks() - + * + * Calculate the blocks to split the preprocessed data into. + * + * Input --- the preprocessed data: + * + * ctx->window[] + * ctx->window_size + * + * Working space: + * Match finding: + * ctx->hash_tab + * ctx->child_tab + * ctx->cached_matches + * ctx->cached_matches_pos + * ctx->matches_already_found + * + * Block cost modeling: + * ctx->costs + * ctx->block_specs (also an output) + * + * Match choosing: + * ctx->optimum + * ctx->optimum_cur_idx + * ctx->optimum_end_idx + * ctx->chosen_matches (also an output) + * + * Output --- the block specifications and the corresponding match/literal data: + * + * ctx->block_specs[] + * ctx->chosen_matches[] + * + * The return value is the approximate number of bits the compressed data will + * take up. + */ +static unsigned +lzx_prepare_blocks(struct lzx_compressor * ctx) +{ + /* This function merely does some initializations, then passes control + * to lzx_prepare_block_recursive(). */ + + /* 1. Initialize match-finding variables. */ + + /* Zero all entries in the hash table, indicating that no length-3 + * character sequences have been discovered in the input yet. */ + memset(ctx->hash_tab, 0, LZX_LZ_HASH_SIZE * 2 * sizeof(ctx->hash_tab[0])); + if (ctx->params.slow.use_len2_matches) + memset(ctx->digram_tab, 0, 256 * 256 * sizeof(ctx->digram_tab[0])); + /* Note: ctx->child_tab need not be initialized. */ + + /* No matches have been found and cached yet. */ + ctx->cached_matches_pos = 0; + ctx->matches_already_found = false; + + /* 2. Initialize match-choosing variables. */ + ctx->optimum_cur_idx = 0; + ctx->optimum_end_idx = 0; + /* Note: ctx->optimum need not be initialized. */ + ctx->block_specs[0].chosen_matches_start_pos = 0; + + /* 3. Set block 1 (index 0) to represent the entire input data. */ + ctx->block_specs[0].block_size = ctx->window_size; + ctx->block_specs[0].window_pos = 0; + + /* 4. Set up a default Huffman symbol cost model for block 1 (index 0). + * The model will be refined later. */ + lzx_set_default_costs(&ctx->block_specs[0].codes.lens); + + /* 5. Initialize the match offset LRU queue. */ + ctx->queue = (struct lzx_lru_queue){1, 1, 1}; + + /* 6. Pass control to recursive procedure. */ + struct lzx_codes * prev_codes = &ctx->zero_codes; + return lzx_prepare_block_recursive(ctx, 1, + ctx->params.slow.num_split_passes, + &prev_codes); +} + +/* + * This is the fast version of lzx_prepare_blocks(). This version "quickly" + * prepares a single compressed block containing the entire input. See the + * description of the "Fast algorithm" at the beginning of this file for more + * information. + * + * Input --- the preprocessed data: + * + * ctx->window[] + * ctx->window_size + * + * Working space: + * ctx->queue + * + * Output --- the block specifications and the corresponding match/literal data: + * + * ctx->block_specs[] + * ctx->chosen_matches[] + */ +static void +lzx_prepare_block_fast(struct lzx_compressor * ctx) +{ + unsigned num_matches; + struct lzx_freqs freqs; + struct lzx_block_spec *spec; + + /* Parameters to hash chain LZ match finder */ + static const struct lz_params lzx_lz_params = { + /* LZX_MIN_MATCH == 2, but 2-character matches are rarely + * useful; the minimum match for compression is set to 3 + * instead. */ + .min_match = 3, + .max_match = LZX_MAX_MATCH, + .good_match = LZX_MAX_MATCH, + .nice_match = LZX_MAX_MATCH, + .max_chain_len = LZX_MAX_MATCH, + .max_lazy_match = LZX_MAX_MATCH, + .too_far = 4096, + }; + + /* Initialize symbol frequencies and match offset LRU queue. */ + memset(&freqs, 0, sizeof(struct lzx_freqs)); + ctx->queue = (struct lzx_lru_queue){ 1, 1, 1 }; + + /* Determine series of matches/literals to output. */ + num_matches = lz_analyze_block(ctx->window, + ctx->window_size, + (u32*)ctx->chosen_matches, + lzx_record_match, + lzx_record_literal, + &freqs, + &ctx->queue, + &freqs, + &lzx_lz_params); + + + /* Set up block specification. */ + spec = &ctx->block_specs[0]; + spec->is_split = 0; + spec->block_type = LZX_BLOCKTYPE_ALIGNED; + spec->window_pos = 0; + spec->block_size = ctx->window_size; + spec->num_chosen_matches = num_matches; + spec->chosen_matches_start_pos = 0; + lzx_make_huffman_codes(&freqs, &spec->codes); +} + +static void +do_call_insn_translation(u32 *call_insn_target, int input_pos, + s32 file_size) +{ + s32 abs_offset; + s32 rel_offset; rel_offset = le32_to_cpu(*call_insn_target); if (rel_offset >= -input_pos && rel_offset < file_size) { @@ -610,158 +2490,367 @@ do_call_insn_translation(u32 *call_insn_target, int input_pos, } /* This is the reverse of undo_call_insn_preprocessing() in lzx-decompress.c. - * See the comment above that function for more information. */ + * See the comment above that function for more information. */ static void -do_call_insn_preprocessing(u8 uncompressed_data[], int uncompressed_data_len) +do_call_insn_preprocessing(u8 data[], int size) { - 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, + for (int i = 0; i < size - 10; i++) { + if (data[i] == 0xe8) { + do_call_insn_translation((u32*)&data[i + 1], i, LZX_WIM_MAGIC_FILESIZE); i += 4; } } } - -static const struct lz_params lzx_lz_params = { - - /* LZX_MIN_MATCH == 2, but 2-character matches are rarely useful; the - * minimum match for compression is set to 3 instead. */ - .min_match = 3, - - .max_match = LZX_MAX_MATCH, - .good_match = LZX_MAX_MATCH, - .nice_match = LZX_MAX_MATCH, - .max_chain_len = LZX_MAX_MATCH, - .max_lazy_match = LZX_MAX_MATCH, - .too_far = 4096, -}; - -/* Documented in wimlib.h */ +/* API function documented in wimlib.h */ WIMLIBAPI unsigned -wimlib_lzx_compress(const void *__uncompressed_data, unsigned uncompressed_len, - void *compressed_data) +wimlib_lzx_compress2(const void * const restrict uncompressed_data, + unsigned const uncompressed_len, + void * const restrict compressed_data, + struct wimlib_lzx_context * const restrict lzx_ctx) { + struct lzx_compressor *ctx = (struct lzx_compressor*)lzx_ctx; struct output_bitstream ostream; - u8 uncompressed_data[uncompressed_len + 8]; - struct lzx_freq_tables freq_tabs; - struct lzx_codes codes; - u32 match_tab[uncompressed_len]; - struct lru_queue queue; - unsigned num_matches; unsigned compressed_len; - unsigned i; - int ret; - int block_type = LZX_BLOCKTYPE_ALIGNED; - wimlib_assert(uncompressed_len <= 32768); + if (uncompressed_len < 100) { + LZX_DEBUG("Too small to bother compressing."); + return 0; + } - if (uncompressed_len < 100) + if (uncompressed_len > 32768) { + LZX_DEBUG("Only up to 32768 bytes of uncompressed data are supported."); return 0; + } - memset(&freq_tabs, 0, sizeof(freq_tabs)); - queue.R0 = 1; - queue.R1 = 1; - queue.R2 = 1; + wimlib_assert(lzx_ctx != NULL); - /* 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("Attempting to compress %u bytes...", uncompressed_len); + + /* The input data must be preprocessed. To avoid changing the original + * input, copy it to a temporary buffer. */ + memcpy(ctx->window, uncompressed_data, uncompressed_len); + ctx->window_size = uncompressed_len; + + /* This line is unnecessary; it just avoids inconsequential accesses of + * uninitialized memory that would show up in memory-checking tools such + * as valgrind. */ + memset(&ctx->window[ctx->window_size], 0, 12); + + LZX_DEBUG("Preprocessing data..."); /* 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. */ + do_call_insn_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, ctx->window_size - 1); + 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..."); + if (flush_output_bitstream(&ostream)) { + /* If the bitstream cannot be flushed, then the output space was + * exhausted. */ + LZX_DEBUG("Data did not compress to less than original length!"); + return 0; + } - /* The next bit indicates whether the block size is the default (32768), - * indicated by a 1 bit, or whether the block size is given by the next - * 16 bits, indicated by a 0 bit. */ - if (uncompressed_len == 32768) { - bitstream_put_bits(&ostream, 1, 1); - } else { - bitstream_put_bits(&ostream, 0, 1); - bitstream_put_bits(&ostream, uncompressed_len, 16); + /* Compute the length of the compressed data. */ + compressed_len = ostream.bit_output - (u8*)compressed_data; + + LZX_DEBUG("Done: compressed %u => %u bytes.", + uncompressed_len, compressed_len); + +#if defined(ENABLE_LZX_DEBUG) || defined(ENABLE_VERIFY_COMPRESSION) + /* Verify that we really get the same thing back when decompressing. */ + { + u8 buf[uncompressed_len]; + int ret; + unsigned i; + + ret = wimlib_lzx_decompress(compressed_data, compressed_len, + buf, uncompressed_len); + if (ret) { + ERROR("Failed to decompress data we " + "compressed using LZX algorithm"); + wimlib_assert(0); + return 0; + } + + bool bad = false; + const u8 * udata = uncompressed_data; + for (i = 0; i < uncompressed_len; i++) { + if (buf[i] != udata[i]) { + bad = true; + ERROR("Data we compressed using LZX algorithm " + "didn't decompress to original " + "(difference at idx %u: c %#02x, u %#02x)", + i, buf[i], udata[i]); + } + } + if (bad) { + wimlib_assert(0); + return 0; + } } +#endif + return compressed_len; +} - /* 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); +static bool +lzx_params_compatible(const struct wimlib_lzx_params *oldparams, + const struct wimlib_lzx_params *newparams) +{ + return 0 == memcmp(oldparams, newparams, sizeof(struct wimlib_lzx_params)); +} - /* 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; +/* API function documented in wimlib.h */ +WIMLIBAPI int +wimlib_lzx_alloc_context(const struct wimlib_lzx_params *params, + struct wimlib_lzx_context **ctx_pp) +{ - /* 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..."); + + struct lzx_compressor *ctx; + + static const struct wimlib_lzx_params fast_default = { + .size_of_this = sizeof(struct wimlib_lzx_params), + .algorithm = WIMLIB_LZX_ALGORITHM_FAST, + .use_defaults = 0, + .fast = { + }, + }; + static const struct wimlib_lzx_params slow_default = { + .size_of_this = sizeof(struct wimlib_lzx_params), + .algorithm = WIMLIB_LZX_ALGORITHM_SLOW, + .use_defaults = 0, + .slow = { + .use_len2_matches = 1, + .num_fast_bytes = 32, + .num_optim_passes = 3, + .num_split_passes = 3, + .main_nostat_cost = 15, + .len_nostat_cost = 15, + .aligned_nostat_cost = 7, + }, + }; + + if (params == NULL) { + LZX_DEBUG("Using default algorithm and parameters."); + params = &slow_default; + } - /* 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 (params->algorithm != WIMLIB_LZX_ALGORITHM_SLOW && + params->algorithm != WIMLIB_LZX_ALGORITHM_FAST) + { + LZX_DEBUG("Invalid algorithm."); + return WIMLIB_ERR_INVALID_PARAM; + } + + if (params->use_defaults) { + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) + params = &slow_default; + else + params = &fast_default; + } + + if (params->size_of_this != sizeof(struct wimlib_lzx_params)) { + LZX_DEBUG("Invalid parameter structure size!"); + return WIMLIB_ERR_INVALID_PARAM; + } + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { + if (params->slow.num_fast_bytes < 3 || + params->slow.num_fast_bytes > 257) + { + LZX_DEBUG("Invalid number of fast bytes!"); + return WIMLIB_ERR_INVALID_PARAM; + } + + if (params->slow.num_optim_passes < 1) + { + LZX_DEBUG("Invalid number of optimization passes!"); + return WIMLIB_ERR_INVALID_PARAM; + } + + if (params->slow.main_nostat_cost < 1 || + params->slow.main_nostat_cost > 16) + { + LZX_DEBUG("Invalid main_nostat_cost!"); + return WIMLIB_ERR_INVALID_PARAM; + } + + if (params->slow.len_nostat_cost < 1 || + params->slow.len_nostat_cost > 16) + { + LZX_DEBUG("Invalid len_nostat_cost!"); + return WIMLIB_ERR_INVALID_PARAM; + } + + if (params->slow.aligned_nostat_cost < 1 || + params->slow.aligned_nostat_cost > 8) + { + LZX_DEBUG("Invalid aligned_nostat_cost!"); + return WIMLIB_ERR_INVALID_PARAM; + } + } - /* Write the compressed literals. */ - ret = lzx_write_compressed_literals(&ostream, block_type, - match_tab, num_matches, &codes); - if (ret) + if (ctx_pp == NULL) { + LZX_DEBUG("Check parameters only."); return 0; + } + + ctx = *(struct lzx_compressor**)ctx_pp; - ret = flush_output_bitstream(&ostream); - if (ret) + if (ctx && lzx_params_compatible(&ctx->params, params)) return 0; - compressed_len = ostream.bit_output - (u8*)compressed_data; + LZX_DEBUG("Allocating memory."); + + ctx = MALLOC(sizeof(struct lzx_compressor)); + if (ctx == NULL) + goto err; -#ifdef ENABLE_VERIFY_COMPRESSION - /* Verify that we really get the same thing back when decompressing. */ - u8 buf[uncompressed_len]; - ret = wimlib_lzx_decompress(compressed_data, compressed_len, - buf, uncompressed_len); - if (ret != 0) { - ERROR("lzx_compress(): Failed to decompress data we compressed"); - abort(); + size_t block_specs_length; + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) + block_specs_length = ((1 << (params->slow.num_split_passes + 1)) - 1); + else + block_specs_length = 1; + ctx->block_specs = MALLOC(block_specs_length * sizeof(ctx->block_specs[0])); + if (ctx->block_specs == NULL) + goto err_free_ctx; + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { + ctx->hash_tab = MALLOC((LZX_LZ_HASH_SIZE + 2 * LZX_MAX_WINDOW_SIZE) * + sizeof(ctx->hash_tab[0])); + if (ctx->hash_tab == NULL) + goto err_free_block_specs; + ctx->child_tab = ctx->hash_tab + LZX_LZ_HASH_SIZE; + } else { + ctx->hash_tab = NULL; + ctx->child_tab = NULL; } - 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->algorithm == WIMLIB_LZX_ALGORITHM_SLOW && + params->slow.use_len2_matches) + { + ctx->digram_tab = MALLOC(256 * 256 * sizeof(ctx->digram_tab[0])); + if (ctx->digram_tab == NULL) + goto err_free_hash_tab; + } else { + ctx->digram_tab = NULL; } -#endif + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { + ctx->cached_matches = MALLOC(10 * LZX_MAX_WINDOW_SIZE * + sizeof(ctx->cached_matches[0])); + if (ctx->cached_matches == NULL) + goto err_free_digram_tab; + } else { + ctx->cached_matches = NULL; + } + + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) { + ctx->optimum = MALLOC((LZX_PARAM_OPTIM_ARRAY_SIZE + LZX_MAX_MATCH) * + sizeof(ctx->optimum[0])); + if (ctx->optimum == NULL) + goto err_free_cached_matches; + } else { + ctx->optimum = NULL; + } + + size_t chosen_matches_length; + if (params->algorithm == WIMLIB_LZX_ALGORITHM_SLOW) + chosen_matches_length = LZX_MAX_WINDOW_SIZE * + (params->slow.num_split_passes + 1); + else + chosen_matches_length = LZX_MAX_WINDOW_SIZE; + + ctx->chosen_matches = MALLOC(chosen_matches_length * + sizeof(ctx->chosen_matches[0])); + if (ctx->chosen_matches == NULL) + goto err_free_optimum; + + memcpy(&ctx->params, params, sizeof(struct wimlib_lzx_params)); + memset(&ctx->zero_codes, 0, sizeof(ctx->zero_codes)); + + LZX_DEBUG("Successfully allocated new LZX context."); + + wimlib_lzx_free_context(*ctx_pp); + *ctx_pp = (struct wimlib_lzx_context*)ctx; + return 0; + +err_free_optimum: + FREE(ctx->optimum); +err_free_cached_matches: + FREE(ctx->cached_matches); +err_free_digram_tab: + FREE(ctx->digram_tab); +err_free_hash_tab: + FREE(ctx->hash_tab); +err_free_block_specs: + FREE(ctx->block_specs); +err_free_ctx: + FREE(ctx); +err: + LZX_DEBUG("Ran out of memory."); + return WIMLIB_ERR_NOMEM; +} + +/* API function documented in wimlib.h */ +WIMLIBAPI void +wimlib_lzx_free_context(struct wimlib_lzx_context *_ctx) +{ + struct lzx_compressor *ctx = (struct lzx_compressor*)_ctx; + + if (ctx) { + FREE(ctx->chosen_matches); + FREE(ctx->optimum); + FREE(ctx->cached_matches); + FREE(ctx->digram_tab); + FREE(ctx->hash_tab); + FREE(ctx->block_specs); + FREE(ctx); + } +} + +/* API function documented in wimlib.h */ +WIMLIBAPI unsigned +wimlib_lzx_compress(const void * const restrict uncompressed_data, + unsigned const uncompressed_len, + void * const restrict compressed_data) +{ + int ret; + struct wimlib_lzx_context *ctx; + unsigned compressed_len; + + ret = wimlib_lzx_alloc_context(NULL, &ctx); + if (ret) { + wimlib_assert(ret != WIMLIB_ERR_INVALID_PARAM); + WARNING("Couldn't allocate LZX compression context: %"TS"", + wimlib_get_error_string(ret)); + return 0; + } + + compressed_len = wimlib_lzx_compress2(uncompressed_data, + uncompressed_len, + compressed_data, + ctx); + + wimlib_lzx_free_context(ctx); + return compressed_len; }