X-Git-Url: https://wimlib.net/git/?p=wimlib;a=blobdiff_plain;f=src%2Flzx-compress.c;h=bc50a858bc9b62cf26d9d1b03d7b822591a1eb33;hp=7510457488b5025be14faf52ce6c8210e1410e49;hb=bcf3ccecc8071729f34fe5b393fab64fc02e3d47;hpb=4dd45340f9fe3a533e0f1a9d6b79f8118e45ca2a diff --git a/src/lzx-compress.c b/src/lzx-compress.c index 75104574..bc50a858 100644 --- a/src/lzx-compress.c +++ b/src/lzx-compress.c @@ -109,7 +109,7 @@ * that position at previous positions in the window. With LZX, the minimum * match length is 2 and the maximum match length is 257. The only restriction * on offsets is that LZX does not allow the last 2 bytes of the window to match - * the the beginning of the window. + * the beginning of the window. * * There are a number of algorithms that can be used for this, including hash * chains, binary trees, and suffix arrays. Binary trees generally work well @@ -196,8 +196,10 @@ #include "wimlib/compressor_ops.h" #include "wimlib/compress_common.h" +#include "wimlib/endianness.h" #include "wimlib/error.h" #include "wimlib/lz_mf.h" +#include "wimlib/lz_repsearch.h" #include "wimlib/lzx.h" #include "wimlib/util.h" #include @@ -327,14 +329,24 @@ struct lzx_compressor { /* Allocated size of @cur_window. */ u32 max_window_size; + /* log2 order of the LZX window size for LZ match offset encoding + * purposes. Will be >= LZX_MIN_WINDOW_ORDER and <= + * LZX_MAX_WINDOW_ORDER. + * + * Note: 1 << @window_order is normally equal to @max_window_size, but + * it will be greater than @max_window_size in the event that the + * compressor was created with a non-power-of-2 block size. (See + * lzx_get_window_order().) */ + unsigned window_order; + /* Compression parameters. */ struct lzx_compressor_params params; unsigned (*get_matches_func)(struct lzx_compressor *, const struct lz_match **); void (*skip_bytes_func)(struct lzx_compressor *, unsigned n); - /* Number of symbols in the main alphabet (depends on the - * @max_window_size since it determines the maximum allowed offset). */ + /* Number of symbols in the main alphabet (depends on the @window_order + * since it determines the maximum allowed offset). */ unsigned num_main_syms; /* The current match offset LRU queue. */ @@ -439,10 +451,145 @@ struct lzx_mc_pos_data { }; /* Adaptive state that exists after an approximate minimum-cost path to - * reach this position is taken. */ + * reach this position is taken. + * + * Note: we update this whenever we update the pending minimum-cost + * path. This is in contrast to LZMA, which also has an optimal parser + * that maintains a repeat offset queue per position, but will only + * compute the queue once that position is actually reached in the + * parse, meaning that matches are being considered *starting* at that + * position. However, the two methods seem to have approximately the + * same performance if appropriate optimizations are used. Intuitively + * the LZMA method seems faster, but it actually suffers from 1-2 extra + * hard-to-predict branches at each position. Probably it works better + * for LZMA than LZX because LZMA has a larger adaptive state than LZX, + * and the LZMA encoder considers more possibilities. */ struct lzx_lru_queue queue; }; + +/* + * Structure to keep track of the current state of sending bits to the + * compressed output buffer. + * + * The LZX bitstream is encoded as a sequence of 16-bit coding units. + */ +struct lzx_output_bitstream { + + /* Bits that haven't yet been written to the output buffer. */ + u32 bitbuf; + + /* Number of bits currently held in @bitbuf. */ + u32 bitcount; + + /* Pointer to the start of the output buffer. */ + le16 *start; + + /* Pointer to the position in the output buffer at which the next coding + * unit should be written. */ + le16 *next; + + /* Pointer past the end of the output buffer. */ + le16 *end; +}; + +/* + * Initialize the output bitstream. + * + * @os + * The output bitstream structure to initialize. + * @buffer + * The buffer being written to. + * @size + * Size of @buffer, in bytes. + */ +static void +lzx_init_output(struct lzx_output_bitstream *os, void *buffer, u32 size) +{ + os->bitbuf = 0; + os->bitcount = 0; + os->start = buffer; + os->next = os->start; + os->end = os->start + size / sizeof(le16); +} + +/* + * Write some bits to the output bitstream. + * + * The bits are given by the low-order @num_bits bits of @bits. Higher-order + * bits in @bits cannot be set. At most 17 bits can be written at once. + * + * @max_bits is a compile-time constant that specifies the maximum number of + * bits that can ever be written at the call site. Currently, it is used to + * optimize away the conditional code for writing a second 16-bit coding unit + * when writing fewer than 17 bits. + * + * If the output buffer space is exhausted, then the bits will be ignored, and + * lzx_flush_output() will return 0 when it gets called. + */ +static _always_inline_attribute void +lzx_write_varbits(struct lzx_output_bitstream *os, + const u32 bits, const unsigned int num_bits, + const unsigned int max_num_bits) +{ + /* This code is optimized for LZX, which never needs to write more than + * 17 bits at once. */ + LZX_ASSERT(num_bits <= 17); + LZX_ASSERT(num_bits <= max_num_bits); + LZX_ASSERT(os->bitcount <= 15); + + /* Add the bits to the bit buffer variable. @bitcount will be at most + * 15, so there will be just enough space for the maximum possible + * @num_bits of 17. */ + os->bitcount += num_bits; + os->bitbuf = (os->bitbuf << num_bits) | bits; + + /* Check whether any coding units need to be written. */ + if (os->bitcount >= 16) { + + os->bitcount -= 16; + + /* Write a coding unit, unless it would overflow the buffer. */ + if (os->next != os->end) + *os->next++ = cpu_to_le16(os->bitbuf >> os->bitcount); + + /* If writing 17 bits, a second coding unit might need to be + * written. But because 'max_num_bits' is a compile-time + * constant, the compiler will optimize away this code at most + * call sites. */ + if (max_num_bits == 17 && os->bitcount == 16) { + if (os->next != os->end) + *os->next++ = cpu_to_le16(os->bitbuf); + os->bitcount = 0; + } + } +} + +/* Use when @num_bits is a compile-time constant. Otherwise use + * lzx_write_varbits(). */ +static _always_inline_attribute void +lzx_write_bits(struct lzx_output_bitstream *os, + const u32 bits, const unsigned int num_bits) +{ + lzx_write_varbits(os, bits, num_bits, num_bits); +} + +/* + * Flush the last coding unit to the output buffer if needed. Return the total + * number of bytes written to the output buffer, or 0 if an overflow occurred. + */ +static u32 +lzx_flush_output(struct lzx_output_bitstream *os) +{ + if (os->next == os->end) + return 0; + + if (os->bitcount != 0) + *os->next++ = cpu_to_le16(os->bitbuf << (16 - os->bitcount)); + + return (const u8 *)os->next - (const u8 *)os->start; +} + /* Returns the LZX position slot that corresponds to a given match offset, * taking into account the recent offset queue and updating it if the offset is * found in it. */ @@ -510,11 +657,11 @@ lzx_make_huffman_codes(const struct lzx_freqs *freqs, /* * Output a precomputed LZX match. * - * @out: + * @os: * The bitstream to which to write the match. - * @block_type: - * The type of the LZX block (LZX_BLOCKTYPE_ALIGNED or - * LZX_BLOCKTYPE_VERBATIM) + * @ones_if_aligned + * A mask of all ones if the block is of type LZX_BLOCKTYPE_ALIGNED, + * otherwise 0. * @match: * The match data. * @codes: @@ -522,30 +669,23 @@ lzx_make_huffman_codes(const struct lzx_freqs *freqs, * and aligned offset Huffman codes for the current LZX compressed block. */ static void -lzx_write_match(struct output_bitstream *out, int block_type, +lzx_write_match(struct lzx_output_bitstream *os, unsigned ones_if_aligned, struct lzx_item match, const struct lzx_codes *codes) { - /* low 8 bits are the match length minus 2 */ unsigned match_len_minus_2 = match.data & 0xff; - /* Next 17 bits are the position footer */ - unsigned position_footer = (match.data >> 8) & 0x1ffff; /* 17 bits */ - /* Next 6 bits are the position slot. */ - unsigned position_slot = (match.data >> 25) & 0x3f; /* 6 bits */ + u32 position_footer = (match.data >> 8) & 0x1ffff; + unsigned position_slot = (match.data >> 25) & 0x3f; unsigned len_header; unsigned len_footer; unsigned main_symbol; unsigned num_extra_bits; - unsigned verbatim_bits; - unsigned aligned_bits; /* If the match length is less than MIN_MATCH_LEN (= 2) + - * NUM_PRIMARY_LENS (= 7), the length header contains - * the match length minus MIN_MATCH_LEN, and there is no - * length footer. + * NUM_PRIMARY_LENS (= 7), the length header contains the match length + * minus MIN_MATCH_LEN, and there is no length footer. * - * Otherwise, the length header contains - * NUM_PRIMARY_LENS, and the length footer contains - * the match length minus NUM_PRIMARY_LENS minus + * Otherwise, the length header contains NUM_PRIMARY_LENS, and the + * length footer contains the match length minus NUM_PRIMARY_LENS minus * MIN_MATCH_LEN. */ if (match_len_minus_2 < LZX_NUM_PRIMARY_LENS) { len_header = match_len_minus_2; @@ -563,184 +703,138 @@ lzx_write_match(struct output_bitstream *out, int block_type, main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS; /* Output main symbol. */ - bitstream_put_bits(out, codes->codewords.main[main_symbol], - codes->lens.main[main_symbol]); + lzx_write_varbits(os, codes->codewords.main[main_symbol], + codes->lens.main[main_symbol], + LZX_MAX_MAIN_CODEWORD_LEN); /* If there is a length footer, output it using the * length Huffman code. */ - if (len_header == LZX_NUM_PRIMARY_LENS) - bitstream_put_bits(out, codes->codewords.len[len_footer], - codes->lens.len[len_footer]); + if (len_header == LZX_NUM_PRIMARY_LENS) { + lzx_write_varbits(os, codes->codewords.len[len_footer], + codes->lens.len[len_footer], + LZX_MAX_LEN_CODEWORD_LEN); + } + + /* Output the position footer. */ num_extra_bits = lzx_get_num_extra_bits(position_slot); - /* For aligned offset blocks with at least 3 extra bits, output the - * verbatim bits literally, then the aligned bits encoded using the - * aligned offset code. Otherwise, only the verbatim bits need to be - * output. */ - if ((block_type == LZX_BLOCKTYPE_ALIGNED) && (num_extra_bits >= 3)) { + if ((num_extra_bits & ones_if_aligned) >= 3) { + + /* Aligned offset blocks: The low 3 bits of the position footer + * are Huffman-encoded using the aligned offset code. The + * remaining bits are output literally. */ - verbatim_bits = position_footer >> 3; - bitstream_put_bits(out, verbatim_bits, - num_extra_bits - 3); + lzx_write_varbits(os, + position_footer >> 3, num_extra_bits - 3, 14); - aligned_bits = (position_footer & 7); - bitstream_put_bits(out, - codes->codewords.aligned[aligned_bits], - codes->lens.aligned[aligned_bits]); + lzx_write_varbits(os, + codes->codewords.aligned[position_footer & 7], + codes->lens.aligned[position_footer & 7], + LZX_MAX_ALIGNED_CODEWORD_LEN); } else { - /* verbatim bits is the same as the position - * footer, in this case. */ - bitstream_put_bits(out, position_footer, num_extra_bits); + /* Verbatim blocks, or fewer than 3 extra bits: All position + * footer bits are output literally. */ + lzx_write_varbits(os, position_footer, num_extra_bits, 17); } } /* Output an LZX literal (encoded with the main Huffman code). */ static void -lzx_write_literal(struct output_bitstream *out, u8 literal, +lzx_write_literal(struct lzx_output_bitstream *os, unsigned literal, const struct lzx_codes *codes) { - bitstream_put_bits(out, - codes->codewords.main[literal], - codes->lens.main[literal]); + lzx_write_varbits(os, codes->codewords.main[literal], + codes->lens.main[literal], LZX_MAX_MAIN_CODEWORD_LEN); } static unsigned -lzx_build_precode(const u8 lens[restrict], - const u8 prev_lens[restrict], - const unsigned num_syms, - u32 precode_freqs[restrict LZX_PRECODE_NUM_SYMBOLS], - u8 output_syms[restrict num_syms], - u8 precode_lens[restrict LZX_PRECODE_NUM_SYMBOLS], - u32 precode_codewords[restrict LZX_PRECODE_NUM_SYMBOLS], - unsigned *num_additional_bits_ret) +lzx_compute_precode_items(const u8 lens[restrict], + const u8 prev_lens[restrict], + const unsigned num_lens, + u32 precode_freqs[restrict], + unsigned precode_items[restrict]) { - memset(precode_freqs, 0, - LZX_PRECODE_NUM_SYMBOLS * sizeof(precode_freqs[0])); - - /* Since the code word lengths use a form of RLE encoding, the goal here - * is to find each run of identical lengths when going through them in - * symbol order (including runs of length 1). For each run, as many - * lengths are encoded using RLE as possible, and the rest are output - * literally. - * - * output_syms[] will be filled in with the length symbols that will be - * output, including RLE codes, not yet encoded using the precode. - * - * cur_run_len keeps track of how many code word lengths are in the - * current run of identical lengths. */ - unsigned output_syms_idx = 0; - unsigned cur_run_len = 1; - unsigned num_additional_bits = 0; - for (unsigned i = 1; i <= num_syms; i++) { - - if (i != num_syms && lens[i] == lens[i - 1]) { - /* Still in a run--- keep going. */ - cur_run_len++; - continue; - } + unsigned *itemptr; + unsigned run_start; + unsigned run_end; + unsigned extra_bits; + int delta; + u8 len; + + itemptr = precode_items; + run_start = 0; + do { + /* Find the next run of codeword lengths. */ - /* Run ended! Check if it is a run of zeroes or a run of - * nonzeroes. */ + /* len = the length being repeated */ + len = lens[run_start]; - /* The symbol that was repeated in the run--- not to be confused - * with the length *of* the run (cur_run_len) */ - unsigned len_in_run = lens[i - 1]; + run_end = run_start + 1; - if (len_in_run == 0) { - /* A run of 0's. Encode it in as few length - * codes as we can. */ + /* Fast case for a single length. */ + if (likely(run_end == num_lens || len != lens[run_end])) { + delta = prev_lens[run_start] - len; + if (delta < 0) + delta += 17; + precode_freqs[delta]++; + *itemptr++ = delta; + run_start++; + continue; + } + + /* Extend the run. */ + do { + run_end++; + } while (run_end != num_lens && len == lens[run_end]); - /* The magic length 18 indicates a run of 20 + n zeroes, - * where n is an uncompressed literal 5-bit integer that - * follows the magic length. */ - while (cur_run_len >= 20) { - unsigned additional_bits; + if (len == 0) { + /* Run of zeroes. */ - additional_bits = min(cur_run_len - 20, 0x1f); - num_additional_bits += 5; + /* Symbol 18: RLE 20 to 51 zeroes at a time. */ + while ((run_end - run_start) >= 20) { + extra_bits = min((run_end - run_start) - 20, 0x1f); precode_freqs[18]++; - output_syms[output_syms_idx++] = 18; - output_syms[output_syms_idx++] = additional_bits; - cur_run_len -= 20 + additional_bits; + *itemptr++ = 18 | (extra_bits << 5); + run_start += 20 + extra_bits; } - /* The magic length 17 indicates a run of 4 + n zeroes, - * where n is an uncompressed literal 4-bit integer that - * follows the magic length. */ - while (cur_run_len >= 4) { - unsigned additional_bits; - - additional_bits = min(cur_run_len - 4, 0xf); - num_additional_bits += 4; + /* Symbol 17: RLE 4 to 19 zeroes at a time. */ + if ((run_end - run_start) >= 4) { + extra_bits = min((run_end - run_start) - 4, 0xf); precode_freqs[17]++; - output_syms[output_syms_idx++] = 17; - output_syms[output_syms_idx++] = additional_bits; - cur_run_len -= 4 + additional_bits; + *itemptr++ = 17 | (extra_bits << 5); + run_start += 4 + extra_bits; } - } else { /* A run of nonzero lengths. */ - /* The magic length 19 indicates a run of 4 + n - * nonzeroes, where n is a literal bit that follows the - * magic length, and where the value of the lengths in - * the run is given by an extra length symbol, encoded - * with the precode, that follows the literal bit. - * - * The extra length symbol is encoded as a difference - * from the length of the codeword for the first symbol - * in the run in the previous code. - * */ - while (cur_run_len >= 4) { - unsigned additional_bits; - signed char delta; - - additional_bits = (cur_run_len > 4); - num_additional_bits += 1; - delta = (signed char)prev_lens[i - cur_run_len] - - (signed char)len_in_run; + /* Symbol 19: RLE 4 to 5 of any length at a time. */ + while ((run_end - run_start) >= 4) { + extra_bits = (run_end - run_start) > 4; + delta = prev_lens[run_start] - len; if (delta < 0) delta += 17; precode_freqs[19]++; - precode_freqs[(unsigned char)delta]++; - output_syms[output_syms_idx++] = 19; - output_syms[output_syms_idx++] = additional_bits; - output_syms[output_syms_idx++] = delta; - cur_run_len -= 4 + additional_bits; + precode_freqs[delta]++; + *itemptr++ = 19 | (extra_bits << 5) | (delta << 6); + run_start += 4 + extra_bits; } } - /* Any remaining lengths in the run are outputted without RLE, - * as a difference from the length of that codeword in the - * previous code. */ - while (cur_run_len > 0) { - signed char delta; - - delta = (signed char)prev_lens[i - cur_run_len] - - (signed char)len_in_run; + /* Output any remaining lengths without RLE. */ + while (run_start != run_end) { + delta = prev_lens[run_start] - len; if (delta < 0) delta += 17; - - precode_freqs[(unsigned char)delta]++; - output_syms[output_syms_idx++] = delta; - cur_run_len--; + precode_freqs[delta]++; + *itemptr++ = delta; + run_start++; } + } while (run_start != num_lens); - cur_run_len = 1; - } - - /* Build the precode from the frequencies of the length symbols. */ - - make_canonical_huffman_code(LZX_PRECODE_NUM_SYMBOLS, - LZX_MAX_PRE_CODEWORD_LEN, - precode_freqs, precode_lens, - precode_codewords); - - *num_additional_bits_ret = num_additional_bits; - - return output_syms_idx; + return itemptr - precode_items; } /* @@ -762,68 +856,71 @@ lzx_build_precode(const u8 lens[restrict], * as deltas from the codeword lengths of the corresponding code in the previous * block. * - * @out: + * @os: * Bitstream to which to write the compressed Huffman code. * @lens: * The codeword lengths, indexed by symbol, in the Huffman code. * @prev_lens: * The codeword lengths, indexed by symbol, in the corresponding Huffman * code in the previous block, or all zeroes if this is the first block. - * @num_syms: + * @num_lens: * The number of symbols in the Huffman code. */ static void -lzx_write_compressed_code(struct output_bitstream *out, +lzx_write_compressed_code(struct lzx_output_bitstream *os, const u8 lens[restrict], const u8 prev_lens[restrict], - unsigned num_syms) + unsigned num_lens) { u32 precode_freqs[LZX_PRECODE_NUM_SYMBOLS]; - u8 output_syms[num_syms]; u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS]; u32 precode_codewords[LZX_PRECODE_NUM_SYMBOLS]; + unsigned precode_items[num_lens]; + unsigned num_precode_items; + unsigned precode_item; + unsigned precode_sym; unsigned i; - unsigned num_output_syms; - u8 precode_sym; - unsigned dummy; - - num_output_syms = lzx_build_precode(lens, - prev_lens, - num_syms, - precode_freqs, - output_syms, - precode_lens, - precode_codewords, - &dummy); - - /* Write the lengths of the precode codes to the output. */ + for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) - bitstream_put_bits(out, precode_lens[i], - LZX_PRECODE_ELEMENT_SIZE); - - /* Write the length symbols, encoded with the precode, to the output. */ - - for (i = 0; i < num_output_syms; ) { - precode_sym = output_syms[i++]; - - bitstream_put_bits(out, precode_codewords[precode_sym], - precode_lens[precode_sym]); - switch (precode_sym) { - case 17: - bitstream_put_bits(out, output_syms[i++], 4); - break; - case 18: - bitstream_put_bits(out, output_syms[i++], 5); - break; - case 19: - bitstream_put_bits(out, output_syms[i++], 1); - bitstream_put_bits(out, - precode_codewords[output_syms[i]], - precode_lens[output_syms[i]]); - i++; - break; - default: - break; + precode_freqs[i] = 0; + + /* Compute the "items" (RLE / literal tokens and extra bits) with which + * the codeword lengths in the larger code will be output. */ + num_precode_items = lzx_compute_precode_items(lens, + prev_lens, + num_lens, + precode_freqs, + precode_items); + + /* Build the precode. */ + make_canonical_huffman_code(LZX_PRECODE_NUM_SYMBOLS, + LZX_MAX_PRE_CODEWORD_LEN, + precode_freqs, precode_lens, + precode_codewords); + + /* Output the lengths of the codewords in the precode. */ + for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) + lzx_write_bits(os, precode_lens[i], LZX_PRECODE_ELEMENT_SIZE); + + /* Output the encoded lengths of the codewords in the larger code. */ + for (i = 0; i < num_precode_items; i++) { + precode_item = precode_items[i]; + precode_sym = precode_item & 0x1F; + lzx_write_varbits(os, precode_codewords[precode_sym], + precode_lens[precode_sym], + LZX_MAX_PRE_CODEWORD_LEN); + if (precode_sym >= 17) { + if (precode_sym == 17) { + lzx_write_bits(os, precode_item >> 5, 4); + } else if (precode_sym == 18) { + lzx_write_bits(os, precode_item >> 5, 5); + } else { + lzx_write_bits(os, (precode_item >> 5) & 1, 1); + precode_sym = precode_item >> 6; + lzx_write_varbits(os, precode_codewords[precode_sym], + precode_lens[precode_sym], + LZX_MAX_PRE_CODEWORD_LEN); + } } } } @@ -833,7 +930,7 @@ lzx_write_compressed_code(struct output_bitstream *out, * compressed block to the output bitstream in the final compressed * representation. * - * @ostream + * @os * The output bitstream. * @block_type * The chosen type of the LZX compressed block (LZX_BLOCKTYPE_ALIGNED or @@ -847,41 +944,41 @@ lzx_write_compressed_code(struct output_bitstream *out, * LZX compressed block. */ static void -lzx_write_items(struct output_bitstream *ostream, int block_type, +lzx_write_items(struct lzx_output_bitstream *os, int block_type, const struct lzx_item items[], u32 num_items, const struct lzx_codes *codes) { + unsigned ones_if_aligned = 0U - (block_type == LZX_BLOCKTYPE_ALIGNED); + for (u32 i = 0; i < num_items; i++) { /* The high bit of the 32-bit intermediate representation * indicates whether the item is an actual LZ-style match (1) or * a literal byte (0). */ if (items[i].data & 0x80000000) - lzx_write_match(ostream, block_type, items[i], codes); + lzx_write_match(os, ones_if_aligned, items[i], codes); else - lzx_write_literal(ostream, items[i].data, codes); + lzx_write_literal(os, items[i].data, codes); } } /* Write an LZX aligned offset or verbatim block to the output. */ static void lzx_write_compressed_block(int block_type, - unsigned block_size, - unsigned max_window_size, + u32 block_size, + unsigned window_order, unsigned num_main_syms, struct lzx_item * chosen_items, - unsigned num_chosen_items, + u32 num_chosen_items, const struct lzx_codes * codes, const struct lzx_codes * prev_codes, - struct output_bitstream * ostream) + struct lzx_output_bitstream * os) { - unsigned i; - LZX_ASSERT(block_type == LZX_BLOCKTYPE_ALIGNED || block_type == LZX_BLOCKTYPE_VERBATIM); /* The first three bits indicate the type of block and are one of the * LZX_BLOCKTYPE_* constants. */ - bitstream_put_bits(ostream, block_type, 3); + lzx_write_bits(os, block_type, 3); /* Output the block size. * @@ -899,73 +996,59 @@ lzx_write_compressed_block(int block_type, * because WIMs created with chunk size greater than 32768 can seemingly * only be opened by wimlib anyway. */ if (block_size == LZX_DEFAULT_BLOCK_SIZE) { - bitstream_put_bits(ostream, 1, 1); + lzx_write_bits(os, 1, 1); } else { - bitstream_put_bits(ostream, 0, 1); + lzx_write_bits(os, 0, 1); - if (max_window_size >= 65536) - bitstream_put_bits(ostream, block_size >> 16, 8); + if (window_order >= 16) + lzx_write_bits(os, block_size >> 16, 8); - bitstream_put_bits(ostream, block_size, 16); + lzx_write_bits(os, block_size & 0xFFFF, 16); } - /* Write out lengths of the main code. Note that the LZX specification - * incorrectly states that the aligned offset code comes after the - * length code, but in fact it is the very first code to be written - * (before the main code). */ - if (block_type == LZX_BLOCKTYPE_ALIGNED) - for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) - bitstream_put_bits(ostream, codes->lens.aligned[i], - LZX_ALIGNEDCODE_ELEMENT_SIZE); - - /* Write the precode and lengths for the first LZX_NUM_CHARS symbols in - * the main code, which are the codewords for literal bytes. */ - lzx_write_compressed_code(ostream, - codes->lens.main, + /* Output the aligned offset code. */ + if (block_type == LZX_BLOCKTYPE_ALIGNED) { + for (int i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) { + lzx_write_bits(os, codes->lens.aligned[i], + LZX_ALIGNEDCODE_ELEMENT_SIZE); + } + } + + /* Output the main code (two parts). */ + lzx_write_compressed_code(os, codes->lens.main, prev_codes->lens.main, LZX_NUM_CHARS); - - /* Write the precode and lengths for the rest of the main code, which - * are the codewords for match headers. */ - lzx_write_compressed_code(ostream, - codes->lens.main + LZX_NUM_CHARS, + lzx_write_compressed_code(os, codes->lens.main + LZX_NUM_CHARS, prev_codes->lens.main + LZX_NUM_CHARS, num_main_syms - LZX_NUM_CHARS); - /* Write the precode and lengths for the length code. */ - lzx_write_compressed_code(ostream, - codes->lens.len, + /* Output the length code. */ + lzx_write_compressed_code(os, codes->lens.len, prev_codes->lens.len, LZX_LENCODE_NUM_SYMBOLS); - /* Write the actual matches and literals. */ - lzx_write_items(ostream, block_type, - chosen_items, num_chosen_items, codes); + /* Output the compressed matches and literals. */ + lzx_write_items(os, block_type, chosen_items, num_chosen_items, codes); } /* Write out the LZX blocks that were computed. */ static void -lzx_write_all_blocks(struct lzx_compressor *c, struct output_bitstream *ostream) +lzx_write_all_blocks(struct lzx_compressor *c, struct lzx_output_bitstream *os) { const struct lzx_codes *prev_codes = &c->zero_codes; for (unsigned i = 0; i < c->num_blocks; i++) { const struct lzx_block_spec *spec = &c->block_specs[i]; - LZX_DEBUG("Writing block %u/%u (type=%d, size=%u, num_chosen_items=%u)...", - i + 1, c->num_blocks, - spec->block_type, spec->block_size, - spec->num_chosen_items); - lzx_write_compressed_block(spec->block_type, spec->block_size, - c->max_window_size, + c->window_order, c->num_main_syms, spec->chosen_items, spec->num_chosen_items, &spec->codes, prev_codes, - ostream); + os); prev_codes = &spec->codes; } @@ -989,7 +1072,7 @@ lzx_tally_match(unsigned match_len, u32 match_offset, struct lzx_freqs *freqs, struct lzx_lru_queue *queue) { unsigned position_slot; - unsigned position_footer; + u32 position_footer; u32 len_header; unsigned main_symbol; unsigned len_footer; @@ -1001,7 +1084,7 @@ lzx_tally_match(unsigned match_len, u32 match_offset, * as part of the main symbol) and a position footer. */ position_slot = lzx_get_position_slot(match_offset, queue); position_footer = (match_offset + LZX_OFFSET_OFFSET) & - ((1U << lzx_get_num_extra_bits(position_slot)) - 1); + (((u32)1 << lzx_get_num_extra_bits(position_slot)) - 1); /* The match length shall be encoded as a length header (itself encoded * as part of the main symbol) and an optional length footer. */ @@ -1059,46 +1142,27 @@ lzx_literal_cost(u8 c, const struct lzx_costs * costs) return costs->main[c]; } -/* Given a (length, offset) pair that could be turned into a valid LZX match as - * well as costs for the codewords in the main, length, and aligned Huffman - * codes, return the approximate number of bits it will take to represent this - * match in the compressed output. Take into account the match offset LRU - * queue and also updates it. */ +/* Returns the cost, in bits, to output a repeat offset match of the specified + * length and position slot (repeat index) using the specified cost model. */ static u32 -lzx_match_cost(unsigned length, u32 offset, const struct lzx_costs *costs, - struct lzx_lru_queue *queue) +lzx_repmatch_cost(u32 len, unsigned position_slot, const struct lzx_costs *costs) { - unsigned position_slot; unsigned len_header, main_symbol; - unsigned num_extra_bits; u32 cost = 0; - position_slot = lzx_get_position_slot(offset, queue); - - len_header = min(length - LZX_MIN_MATCH_LEN, LZX_NUM_PRIMARY_LENS); + len_header = min(len - LZX_MIN_MATCH_LEN, LZX_NUM_PRIMARY_LENS); main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS; /* Account for main symbol. */ cost += costs->main[main_symbol]; - /* Account for extra position information. */ - num_extra_bits = lzx_get_num_extra_bits(position_slot); - if (num_extra_bits >= 3) { - cost += num_extra_bits - 3; - cost += costs->aligned[(offset + LZX_OFFSET_OFFSET) & 7]; - } else { - cost += num_extra_bits; - } - /* Account for extra length information. */ if (len_header == LZX_NUM_PRIMARY_LENS) - cost += costs->len[length - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS]; + cost += costs->len[len - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS]; return cost; - } - /* Set the cost model @c->costs from the Huffman codeword lengths specified in * @lens. * @@ -1382,7 +1446,24 @@ lzx_match_chooser_reverse_list(struct lzx_compressor *c, unsigned cur_pos) } /* - * lzx_choose_near_optimal_match() - + * Find the longest repeat offset match. + * + * If no match of at least LZX_MIN_MATCH_LEN bytes is found, then return 0. + * + * If a match of at least LZX_MIN_MATCH_LEN bytes is found, then return its + * length and set *slot_ret to the index of its offset in @queue. + */ +static inline u32 +lzx_repsearch(const u8 * const strptr, const u32 bytes_remaining, + const struct lzx_lru_queue *queue, unsigned *slot_ret) +{ + BUILD_BUG_ON(LZX_MIN_MATCH_LEN != 2); + return lz_repsearch(strptr, bytes_remaining, LZX_MAX_MATCH_LEN, + queue->R, LZX_NUM_RECENT_OFFSETS, slot_ret); +} + +/* + * lzx_choose_near_optimal_item() - * * Choose an approximately optimal match or literal to use at the next position * in the string, or "window", being LZ-encoded. @@ -1449,19 +1530,20 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) unsigned num_matches; const struct lz_match *matches; struct lz_match match; - unsigned longest_len; - unsigned longest_rep_len; - u32 longest_rep_offset; + u32 longest_len; + u32 longest_rep_len; + unsigned longest_rep_slot; unsigned cur_pos; unsigned end_pos; + struct lzx_mc_pos_data *optimum = c->optimum; if (c->optimum_cur_idx != c->optimum_end_idx) { /* Case 2: Return the next match/literal already found. */ - match.len = c->optimum[c->optimum_cur_idx].next.link - + match.len = optimum[c->optimum_cur_idx].next.link - c->optimum_cur_idx; - match.offset = c->optimum[c->optimum_cur_idx].next.match_offset; + match.offset = optimum[c->optimum_cur_idx].next.match_offset; - c->optimum_cur_idx = c->optimum[c->optimum_cur_idx].next.link; + c->optimum_cur_idx = optimum[c->optimum_cur_idx].next.link; return match; } @@ -1470,39 +1552,30 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) c->optimum_cur_idx = 0; c->optimum_end_idx = 0; - /* Search for matches at recent offsets. Only keep the one with the - * longest match length. */ - longest_rep_len = LZX_MIN_MATCH_LEN - 1; - if (c->match_window_pos >= 1) { - unsigned limit = min(LZX_MAX_MATCH_LEN, - c->match_window_end - c->match_window_pos); - for (int i = 0; i < LZX_NUM_RECENT_OFFSETS; i++) { - u32 offset = c->queue.R[i]; - const u8 *strptr = &c->cur_window[c->match_window_pos]; - const u8 *matchptr = strptr - offset; - unsigned len = 0; - while (len < limit && strptr[len] == matchptr[len]) - len++; - if (len > longest_rep_len) { - longest_rep_len = len; - longest_rep_offset = offset; - } - } + /* Search for matches at repeat offsets. As a heuristic, we only keep + * the one with the longest match length. */ + if (likely(c->match_window_pos >= 1)) { + longest_rep_len = lzx_repsearch(&c->cur_window[c->match_window_pos], + c->match_window_end - c->match_window_pos, + &c->queue, + &longest_rep_slot); + } else { + longest_rep_len = 0; } - /* If there's a long match with a recent offset, take it. */ + /* If there's a long match with a repeat offset, choose it immediately. */ if (longest_rep_len >= c->params.nice_match_length) { lzx_skip_bytes(c, longest_rep_len); return (struct lz_match) { .len = longest_rep_len, - .offset = longest_rep_offset, + .offset = c->queue.R[longest_rep_slot], }; } - /* Search other matches. */ + /* Find other matches. */ num_matches = lzx_get_matches(c, &matches); - /* If there's a long match, take it. */ + /* If there's a long match, choose it immediately. */ if (num_matches) { longest_len = matches[num_matches - 1].len; if (longest_len >= c->params.nice_match_length) { @@ -1513,12 +1586,11 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) longest_len = 1; } - /* Calculate the cost to reach the next position by coding a literal. - */ - c->optimum[1].queue = c->queue; - c->optimum[1].cost = lzx_literal_cost(c->cur_window[c->match_window_pos - 1], + /* Calculate the cost to reach the next position by coding a literal. */ + optimum[1].queue = c->queue; + optimum[1].cost = lzx_literal_cost(c->cur_window[c->match_window_pos - 1], &c->costs); - c->optimum[1].prev.link = 0; + optimum[1].prev.link = 0; /* Calculate the cost to reach any position up to and including that * reached by the longest match. @@ -1552,41 +1624,49 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) } do { + u32 cost; unsigned len_header; unsigned main_symbol; - u32 cost; cost = position_cost; - len_header = min(len - LZX_MIN_MATCH_LEN, LZX_NUM_PRIMARY_LENS); + if (len - LZX_MIN_MATCH_LEN < LZX_NUM_PRIMARY_LENS) { + len_header = len - LZX_MIN_MATCH_LEN; + } else { + len_header = LZX_NUM_PRIMARY_LENS; + cost += c->costs.len[len - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS]; + } + main_symbol = ((position_slot << 3) | len_header) + LZX_NUM_CHARS; cost += c->costs.main[main_symbol]; - if (len_header == LZX_NUM_PRIMARY_LENS) - cost += c->costs.len[len - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS]; - c->optimum[len].queue = queue; - c->optimum[len].prev.link = 0; - c->optimum[len].prev.match_offset = offset; - c->optimum[len].cost = cost; + optimum[len].queue = queue; + optimum[len].prev.link = 0; + optimum[len].prev.match_offset = offset; + optimum[len].cost = cost; } while (++len <= matches[i].len); } end_pos = longest_len; - if (longest_rep_len >= LZX_MIN_MATCH_LEN) { - struct lzx_lru_queue queue; + if (longest_rep_len) { + + LZX_ASSERT(longest_rep_len >= LZX_MIN_MATCH_LEN); + u32 cost; while (end_pos < longest_rep_len) - c->optimum[++end_pos].cost = MC_INFINITE_COST; + optimum[++end_pos].cost = MC_INFINITE_COST; - queue = c->queue; - cost = lzx_match_cost(longest_rep_len, longest_rep_offset, - &c->costs, &queue); - if (cost <= c->optimum[longest_rep_len].cost) { - c->optimum[longest_rep_len].queue = queue; - c->optimum[longest_rep_len].prev.link = 0; - c->optimum[longest_rep_len].prev.match_offset = longest_rep_offset; - c->optimum[longest_rep_len].cost = cost; + cost = lzx_repmatch_cost(longest_rep_len, longest_rep_slot, + &c->costs); + if (cost <= optimum[longest_rep_len].cost) { + optimum[longest_rep_len].queue = c->queue; + swap(optimum[longest_rep_len].queue.R[0], + optimum[longest_rep_len].queue.R[longest_rep_slot]); + optimum[longest_rep_len].prev.link = 0; + optimum[longest_rep_len].prev.match_offset = + optimum[longest_rep_len].queue.R[0]; + optimum[longest_rep_len].cost = cost; } } @@ -1594,17 +1674,16 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) * position. The algorithm may find multiple paths to reach each * position; only the lowest-cost path is saved. * - * The progress of the parse is tracked in the @c->optimum array, which - * for each position contains the minimum cost to reach that position, - * the index of the start of the match/literal taken to reach that - * position through the minimum-cost path, the offset of the match taken - * (not relevant for literals), and the adaptive state that will exist - * at that position after the minimum-cost path is taken. The @cur_pos + * The progress of the parse is tracked in the @optimum array, which for + * each position contains the minimum cost to reach that position, the + * index of the start of the match/literal taken to reach that position + * through the minimum-cost path, the offset of the match taken (not + * relevant for literals), and the adaptive state that will exist at + * that position after the minimum-cost path is taken. The @cur_pos * variable stores the position at which the algorithm is currently * considering coding choices, and the @end_pos variable stores the * greatest position at which the costs of coding choices have been - * saved. (Actually, the algorithm guarantees that all positions up to - * and including @end_pos are reachable by at least one path.) + * saved. * * The loop terminates when any one of the following conditions occurs: * @@ -1620,7 +1699,7 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) * match/literal list. * * 3. Failing either of the above in a degenerate case, the loop - * terminates when space in the @c->optimum array is exhausted. + * terminates when space in the @optimum array is exhausted. * This terminates the algorithm and forces it to start returning * matches/literals even though they may not be globally optimal. * @@ -1642,24 +1721,14 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) if (cur_pos == end_pos || cur_pos == LZX_OPTIM_ARRAY_LENGTH) return lzx_match_chooser_reverse_list(c, cur_pos); - /* Search for matches at recent offsets. */ - longest_rep_len = LZX_MIN_MATCH_LEN - 1; - unsigned limit = min(LZX_MAX_MATCH_LEN, - c->match_window_end - c->match_window_pos); - for (int i = 0; i < LZX_NUM_RECENT_OFFSETS; i++) { - u32 offset = c->optimum[cur_pos].queue.R[i]; - const u8 *strptr = &c->cur_window[c->match_window_pos]; - const u8 *matchptr = strptr - offset; - unsigned len = 0; - while (len < limit && strptr[len] == matchptr[len]) - len++; - if (len > longest_rep_len) { - longest_rep_len = len; - longest_rep_offset = offset; - } - } + /* Search for matches at repeat offsets. Again, as a heuristic + * we only keep the longest one. */ + longest_rep_len = lzx_repsearch(&c->cur_window[c->match_window_pos], + c->match_window_end - c->match_window_pos, + &optimum[cur_pos].queue, + &longest_rep_slot); - /* If we found a long match at a recent offset, choose it + /* If we found a long match at a repeat offset, choose it * immediately. */ if (longest_rep_len >= c->params.nice_match_length) { /* Build the list of matches to return and get @@ -1667,8 +1736,9 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) match = lzx_match_chooser_reverse_list(c, cur_pos); /* Append the long match to the end of the list. */ - c->optimum[cur_pos].next.match_offset = longest_rep_offset; - c->optimum[cur_pos].next.link = cur_pos + longest_rep_len; + optimum[cur_pos].next.match_offset = + optimum[cur_pos].queue.R[longest_rep_slot]; + optimum[cur_pos].next.link = cur_pos + longest_rep_len; c->optimum_end_idx = cur_pos + longest_rep_len; /* Skip over the remaining bytes of the long match. */ @@ -1678,10 +1748,10 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) return match; } - /* Search other matches. */ + /* Find other matches. */ num_matches = lzx_get_matches(c, &matches); - /* If there's a long match, take it. */ + /* If there's a long match, choose it immediately. */ if (num_matches) { longest_len = matches[num_matches - 1].len; if (longest_len >= c->params.nice_match_length) { @@ -1690,9 +1760,9 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) match = lzx_match_chooser_reverse_list(c, cur_pos); /* Append the long match to the end of the list. */ - c->optimum[cur_pos].next.match_offset = + optimum[cur_pos].next.match_offset = matches[num_matches - 1].offset; - c->optimum[cur_pos].next.link = cur_pos + longest_len; + optimum[cur_pos].next.link = cur_pos + longest_len; c->optimum_end_idx = cur_pos + longest_len; /* Skip over the remaining bytes of the long match. */ @@ -1705,17 +1775,19 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) longest_len = 1; } + /* If we are reaching any positions for the first time, we need + * to initialize their costs to infinity. */ while (end_pos < cur_pos + longest_len) - c->optimum[++end_pos].cost = MC_INFINITE_COST; + optimum[++end_pos].cost = MC_INFINITE_COST; /* Consider coding a literal. */ - cost = c->optimum[cur_pos].cost + + cost = optimum[cur_pos].cost + lzx_literal_cost(c->cur_window[c->match_window_pos - 1], &c->costs); - if (cost < c->optimum[cur_pos + 1].cost) { - c->optimum[cur_pos + 1].queue = c->optimum[cur_pos].queue; - c->optimum[cur_pos + 1].cost = cost; - c->optimum[cur_pos + 1].prev.link = cur_pos; + if (cost < optimum[cur_pos + 1].cost) { + optimum[cur_pos + 1].queue = optimum[cur_pos].queue; + optimum[cur_pos + 1].cost = cost; + optimum[cur_pos + 1].prev.link = cur_pos; } /* Consider coding a match. @@ -1728,16 +1800,25 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) * length. */ for (unsigned i = 0, len = 2; i < num_matches; i++) { u32 offset; - struct lzx_lru_queue queue; u32 position_cost; unsigned position_slot; unsigned num_extra_bits; offset = matches[i].offset; - queue = c->optimum[cur_pos].queue; - position_cost = c->optimum[cur_pos].cost; + position_cost = optimum[cur_pos].cost; + + /* Yet another optimization: instead of calling + * lzx_get_position_slot(), hand-inline the search of + * the repeat offset queue. Then we can omit the + * extra_bits calculation for repeat offset matches, and + * also only compute the updated queue if we actually do + * find a new lowest cost path. */ + for (position_slot = 0; position_slot < LZX_NUM_RECENT_OFFSETS; position_slot++) + if (offset == optimum[cur_pos].queue.R[position_slot]) + goto have_position_cost; + + position_slot = lzx_get_position_slot_raw(offset + LZX_OFFSET_OFFSET); - position_slot = lzx_get_position_slot(offset, &queue); num_extra_bits = lzx_get_num_extra_bits(position_slot); if (num_extra_bits >= 3) { position_cost += num_extra_bits - 3; @@ -1747,51 +1828,89 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c) position_cost += num_extra_bits; } + have_position_cost: + do { + u32 cost; unsigned len_header; unsigned main_symbol; - u32 cost; cost = position_cost; - len_header = min(len - LZX_MIN_MATCH_LEN, - LZX_NUM_PRIMARY_LENS); - main_symbol = ((position_slot << 3) | len_header) + - LZX_NUM_CHARS; - cost += c->costs.main[main_symbol]; - if (len_header == LZX_NUM_PRIMARY_LENS) { + if (len - LZX_MIN_MATCH_LEN < LZX_NUM_PRIMARY_LENS) { + len_header = len - LZX_MIN_MATCH_LEN; + } else { + len_header = LZX_NUM_PRIMARY_LENS; cost += c->costs.len[len - LZX_MIN_MATCH_LEN - LZX_NUM_PRIMARY_LENS]; } - if (cost < c->optimum[cur_pos + len].cost) { - c->optimum[cur_pos + len].queue = queue; - c->optimum[cur_pos + len].prev.link = cur_pos; - c->optimum[cur_pos + len].prev.match_offset = offset; - c->optimum[cur_pos + len].cost = cost; + + main_symbol = ((position_slot << 3) | len_header) + + LZX_NUM_CHARS; + cost += c->costs.main[main_symbol]; + + if (cost < optimum[cur_pos + len].cost) { + if (position_slot < LZX_NUM_RECENT_OFFSETS) { + optimum[cur_pos + len].queue = optimum[cur_pos].queue; + swap(optimum[cur_pos + len].queue.R[0], + optimum[cur_pos + len].queue.R[position_slot]); + } else { + optimum[cur_pos + len].queue.R[0] = offset; + optimum[cur_pos + len].queue.R[1] = optimum[cur_pos].queue.R[0]; + optimum[cur_pos + len].queue.R[2] = optimum[cur_pos].queue.R[1]; + } + optimum[cur_pos + len].prev.link = cur_pos; + optimum[cur_pos + len].prev.match_offset = offset; + optimum[cur_pos + len].cost = cost; } } while (++len <= matches[i].len); } - if (longest_rep_len >= LZX_MIN_MATCH_LEN) { - struct lzx_lru_queue queue; - - while (end_pos < cur_pos + longest_rep_len) - c->optimum[++end_pos].cost = MC_INFINITE_COST; + /* Consider coding a repeat offset match. + * + * As a heuristic, we only consider the longest length of the + * longest repeat offset match. This does not, however, + * necessarily mean that we will never consider any other repeat + * offsets, because above we detect repeat offset matches that + * were found by the regular match-finder. Therefore, this + * special handling of the longest repeat-offset match is only + * helpful for coding a repeat offset match that was *not* found + * by the match-finder, e.g. due to being obscured by a less + * distant match that is at least as long. + * + * Note: an alternative, used in LZMA, is to consider every + * length of every repeat offset match. This is a more thorough + * search, and it makes it unnecessary to detect repeat offset + * matches that were found by the regular match-finder. But by + * my tests, for LZX the LZMA method slows down the compressor + * by ~10% and doesn't actually help the compression ratio too + * much. + * + * Also tested a compromise approach: consider every 3rd length + * of the longest repeat offset match. Still didn't seem quite + * worth it, though. + */ + if (longest_rep_len) { - queue = c->optimum[cur_pos].queue; + LZX_ASSERT(longest_rep_len >= LZX_MIN_MATCH_LEN); - cost = c->optimum[cur_pos].cost + - lzx_match_cost(longest_rep_len, longest_rep_offset, - &c->costs, &queue); - if (cost <= c->optimum[cur_pos + longest_rep_len].cost) { - c->optimum[cur_pos + longest_rep_len].queue = - queue; - c->optimum[cur_pos + longest_rep_len].prev.link = + while (end_pos < cur_pos + longest_rep_len) + optimum[++end_pos].cost = MC_INFINITE_COST; + + cost = optimum[cur_pos].cost + + lzx_repmatch_cost(longest_rep_len, longest_rep_slot, + &c->costs); + if (cost <= optimum[cur_pos + longest_rep_len].cost) { + optimum[cur_pos + longest_rep_len].queue = + optimum[cur_pos].queue; + swap(optimum[cur_pos + longest_rep_len].queue.R[0], + optimum[cur_pos + longest_rep_len].queue.R[longest_rep_slot]); + optimum[cur_pos + longest_rep_len].prev.link = cur_pos; - c->optimum[cur_pos + longest_rep_len].prev.match_offset = - longest_rep_offset; - c->optimum[cur_pos + longest_rep_len].cost = + optimum[cur_pos + longest_rep_len].prev.match_offset = + optimum[cur_pos + longest_rep_len].queue.R[0]; + optimum[cur_pos + longest_rep_len].cost = cost; } } @@ -1925,7 +2044,7 @@ lzx_choose_items_for_block(struct lzx_compressor *c, struct lzx_block_spec *spec struct lz_match lz_match; struct lzx_item lzx_item; - LZX_ASSERT(num_passes >= 1); + LZX_ASSERT(num_passes_remaining >= 1); LZX_ASSERT(lz_mf_get_position(c->mf) == spec->window_pos); c->match_window_end = spec->window_pos + spec->block_size; @@ -2111,13 +2230,17 @@ static void lzx_free_compressor(void *_c); static u64 -lzx_get_needed_memory(size_t max_window_size, unsigned int compression_level) +lzx_get_needed_memory(size_t max_block_size, unsigned int compression_level) { struct lzx_compressor_params params; u64 size = 0; + unsigned window_order; + u32 max_window_size; - if (!lzx_window_size_valid(max_window_size)) + window_order = lzx_get_window_order(max_block_size); + if (window_order == 0) return 0; + max_window_size = max_block_size; lzx_build_params(compression_level, max_window_size, ¶ms); @@ -2143,15 +2266,19 @@ lzx_get_needed_memory(size_t max_window_size, unsigned int compression_level) } static int -lzx_create_compressor(size_t max_window_size, unsigned int compression_level, +lzx_create_compressor(size_t max_block_size, unsigned int compression_level, void **c_ret) { struct lzx_compressor *c; struct lzx_compressor_params params; struct lz_mf_params mf_params; + unsigned window_order; + u32 max_window_size; - if (!lzx_window_size_valid(max_window_size)) + window_order = lzx_get_window_order(max_block_size); + if (window_order == 0) return WIMLIB_ERR_INVALID_PARAM; + max_window_size = max_block_size; lzx_build_params(compression_level, max_window_size, ¶ms); lzx_build_mf_params(¶ms, max_window_size, &mf_params); @@ -2163,8 +2290,9 @@ lzx_create_compressor(size_t max_window_size, unsigned int compression_level, goto oom; c->params = params; - c->num_main_syms = lzx_get_num_main_syms(max_window_size); + c->num_main_syms = lzx_get_num_main_syms(window_order); c->max_window_size = max_window_size; + c->window_order = window_order; c->cur_window = ALIGNED_MALLOC(max_window_size, 16); if (!c->cur_window) @@ -2219,44 +2347,28 @@ lzx_compress(const void *uncompressed_data, size_t uncompressed_size, void *compressed_data, size_t compressed_size_avail, void *_c) { struct lzx_compressor *c = _c; - struct output_bitstream ostream; - size_t compressed_size; + struct lzx_output_bitstream os; - if (uncompressed_size < 100) { - LZX_DEBUG("Too small to bother compressing."); + /* Don't bother compressing very small inputs. */ + if (uncompressed_size < 100) return 0; - } - - LZX_DEBUG("Attempting to compress %zu bytes...", - uncompressed_size); /* The input data must be preprocessed. To avoid changing the original * input, copy it to a temporary buffer. */ memcpy(c->cur_window, uncompressed_data, uncompressed_size); c->cur_window_size = uncompressed_size; - /* Before doing any actual compression, do the call instruction (0xe8 - * byte) translation on the uncompressed data. */ + /* Preprocess the data. */ lzx_do_e8_preprocessing(c->cur_window, c->cur_window_size); /* Prepare the compressed data. */ lzx_prepare_blocks(c); - /* Generate the compressed data. */ - init_output_bitstream(&ostream, compressed_data, compressed_size_avail); - lzx_write_all_blocks(c, &ostream); - - compressed_size = flush_output_bitstream(&ostream); - if (compressed_size == (u32)~0UL) { - LZX_DEBUG("Data did not compress to %zu bytes or less!", - compressed_size_avail); - return 0; - } - - LZX_DEBUG("Done: compressed %zu => %zu bytes.", - uncompressed_size, compressed_size); - - return compressed_size; + /* Generate the compressed data and return its size, or 0 if an overflow + * occurred. */ + lzx_init_output(&os, compressed_data, compressed_size_avail); + lzx_write_all_blocks(c, &os); + return lzx_flush_output(&os); } static void