/* * lzms-compress.c */ /* * Copyright (C) 2013 Eric Biggers * * This file is part of wimlib, a library for working with WIM files. * * wimlib is free software; you can redistribute it and/or modify it under the * terms of the GNU General Public License as published by the Free * Software Foundation; either version 3 of the License, or (at your option) * any later version. * * wimlib is distributed in the hope that it will be useful, but WITHOUT ANY * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR * A PARTICULAR PURPOSE. See the GNU General Public License for more * details. * * You should have received a copy of the GNU General Public License * along with wimlib; if not, see http://www.gnu.org/licenses/. */ /* This a compressor for the LZMS compression format. More details about this * format can be found in lzms-decompress.c. * * This is currently an unsophisticated implementation that is fast but does not * attain the best compression ratios allowed by the format. */ #ifdef HAVE_CONFIG_H # include "config.h" #endif #include "wimlib.h" #include "wimlib/assert.h" #include "wimlib/compiler.h" #include "wimlib/compressor_ops.h" #include "wimlib/compress_common.h" #include "wimlib/endianness.h" #include "wimlib/error.h" #include "wimlib/lzms.h" #include "wimlib/util.h" #include #include /* Stucture used for writing raw bits to the end of the LZMS-compressed data as * a series of 16-bit little endian coding units. */ struct lzms_output_bitstream { /* Buffer variable containing zero or more bits that have been logically * written to the bitstream but not yet written to memory. This must be * at least as large as the coding unit size. */ u16 bitbuf; /* Number of bits in @bitbuf that are valid. */ unsigned num_free_bits; /* Pointer to one past the next position in the compressed data buffer * at which to output a 16-bit coding unit. */ le16 *out; /* Maximum number of 16-bit coding units that can still be output to * the compressed data buffer. */ size_t num_le16_remaining; /* Set to %true if not all coding units could be output due to * insufficient space. */ bool overrun; }; /* Stucture used for range encoding (raw version). */ struct lzms_range_encoder_raw { /* A 33-bit variable that holds the low boundary of the current range. * The 33rd bit is needed to catch carries. */ u64 low; /* Size of the current range. */ u32 range; /* Next 16-bit coding unit to output. */ u16 cache; /* Number of 16-bit coding units whose output has been delayed due to * possible carrying. The first such coding unit is @cache; all * subsequent such coding units are 0xffff. */ u32 cache_size; /* Pointer to the next position in the compressed data buffer at which * to output a 16-bit coding unit. */ le16 *out; /* Maximum number of 16-bit coding units that can still be output to * the compressed data buffer. */ size_t num_le16_remaining; /* %true when the very first coding unit has not yet been output. */ bool first; /* Set to %true if not all coding units could be output due to * insufficient space. */ bool overrun; }; /* Structure used for range encoding. This wraps around `struct * lzms_range_encoder_raw' to use and maintain probability entries. */ struct lzms_range_encoder { /* Pointer to the raw range encoder, which has no persistent knowledge * of probabilities. Multiple lzms_range_encoder's share the same * lzms_range_encoder_raw. */ struct lzms_range_encoder_raw *rc; /* Bits recently encoded by this range encoder. This are used as in * index into @prob_entries. */ u32 state; /* Bitmask for @state to prevent its value from exceeding the number of * probability entries. */ u32 mask; /* Probability entries being used for this range encoder. */ struct lzms_probability_entry prob_entries[LZMS_MAX_NUM_STATES]; }; /* Structure used for Huffman encoding, optionally encoding larger "values" as a * Huffman symbol specifying a slot and a slot-dependent number of extra bits. * */ struct lzms_huffman_encoder { /* Bitstream to write Huffman-encoded symbols and verbatim bits to. * Multiple lzms_huffman_encoder's share the same lzms_output_bitstream. */ struct lzms_output_bitstream *os; /* Pointer to the slot base table to use. */ const u32 *slot_base_tab; /* Number of symbols that have been written using this code far. Reset * to 0 whenever the code is rebuilt. */ u32 num_syms_written; /* When @num_syms_written reaches this number, the Huffman code must be * rebuilt. */ u32 rebuild_freq; /* Number of symbols in the represented Huffman code. */ unsigned num_syms; /* Running totals of symbol frequencies. These are diluted slightly * whenever the code is rebuilt. */ u32 sym_freqs[LZMS_MAX_NUM_SYMS]; /* The length, in bits, of each symbol in the Huffman code. */ u8 lens[LZMS_MAX_NUM_SYMS]; /* The codeword of each symbol in the Huffman code. */ u16 codewords[LZMS_MAX_NUM_SYMS]; }; /* State of the LZMS compressor. */ struct lzms_compressor { /* Pointer to a buffer holding the preprocessed data to compress. */ u8 *window; /* Current position in @buffer. */ u32 cur_window_pos; /* Size of the data in @buffer. */ u32 window_size; /* Temporary array used by lz_analyze_block(); must be at least as long * as the window. */ u32 *prev_tab; /* Maximum block size this compressor instantiation allows. This is the * allocated size of @window. */ u32 max_block_size; /* Raw range encoder which outputs to the beginning of the compressed * data buffer, proceeding forwards. */ struct lzms_range_encoder_raw rc; /* Bitstream which outputs to the end of the compressed data buffer, * proceeding backwards. */ struct lzms_output_bitstream os; /* Range encoders. */ struct lzms_range_encoder main_range_encoder; struct lzms_range_encoder match_range_encoder; struct lzms_range_encoder lz_match_range_encoder; struct lzms_range_encoder lz_repeat_match_range_encoders[LZMS_NUM_RECENT_OFFSETS - 1]; struct lzms_range_encoder delta_match_range_encoder; struct lzms_range_encoder delta_repeat_match_range_encoders[LZMS_NUM_RECENT_OFFSETS - 1]; /* Huffman encoders. */ struct lzms_huffman_encoder literal_encoder; struct lzms_huffman_encoder lz_offset_encoder; struct lzms_huffman_encoder length_encoder; struct lzms_huffman_encoder delta_power_encoder; struct lzms_huffman_encoder delta_offset_encoder; /* LRU (least-recently-used) queue of LZ match offsets. */ u64 recent_lz_offsets[LZMS_NUM_RECENT_OFFSETS + 1]; /* LRU (least-recently-used) queue of delta match powers. */ u32 recent_delta_powers[LZMS_NUM_RECENT_OFFSETS + 1]; /* LRU (least-recently-used) queue of delta match offsets. */ u32 recent_delta_offsets[LZMS_NUM_RECENT_OFFSETS + 1]; /* These variables are used to delay updates to the LRU queues by one * decoded item. */ u32 prev_lz_offset; u32 prev_delta_power; u32 prev_delta_offset; u32 upcoming_lz_offset; u32 upcoming_delta_power; u32 upcoming_delta_offset; /* Used for preprocessing. */ s32 last_target_usages[65536]; }; struct lzms_match { u32 length; u32 offset; }; /* Initialize the output bitstream @os to write forwards to the specified * compressed data buffer @out that is @out_limit 16-bit integers long. */ static void lzms_output_bitstream_init(struct lzms_output_bitstream *os, le16 *out, size_t out_limit) { os->bitbuf = 0; os->num_free_bits = 16; os->out = out + out_limit; os->num_le16_remaining = out_limit; os->overrun = false; } /* Write @num_bits bits, contained in the low @num_bits bits of @bits (ordered * from high-order to low-order), to the output bitstream @os. */ static void lzms_output_bitstream_put_bits(struct lzms_output_bitstream *os, u32 bits, unsigned num_bits) { bits &= (1U << num_bits) - 1; while (num_bits > os->num_free_bits) { if (unlikely(os->num_le16_remaining == 0)) { os->overrun = true; return; } unsigned num_fill_bits = os->num_free_bits; os->bitbuf <<= num_fill_bits; os->bitbuf |= bits >> (num_bits - num_fill_bits); *--os->out = cpu_to_le16(os->bitbuf); --os->num_le16_remaining; os->num_free_bits = 16; num_bits -= num_fill_bits; bits &= (1U << num_bits) - 1; } os->bitbuf <<= num_bits; os->bitbuf |= bits; os->num_free_bits -= num_bits; } /* Flush the output bitstream, ensuring that all bits written to it have been * written to memory. Returns %true if all bits were output successfully, or * %false if an overrun occurred. */ static bool lzms_output_bitstream_flush(struct lzms_output_bitstream *os) { if (os->num_free_bits != 16) lzms_output_bitstream_put_bits(os, 0, os->num_free_bits + 1); return !os->overrun; } /* Initialize the range encoder @rc to write forwards to the specified * compressed data buffer @out that is @out_limit 16-bit integers long. */ static void lzms_range_encoder_raw_init(struct lzms_range_encoder_raw *rc, le16 *out, size_t out_limit) { rc->low = 0; rc->range = 0xffffffff; rc->cache = 0; rc->cache_size = 1; rc->out = out; rc->num_le16_remaining = out_limit; rc->first = true; rc->overrun = false; } /* * Attempt to flush bits from the range encoder. * * Note: this is based on the public domain code for LZMA written by Igor * Pavlov. The only differences in this function are that in LZMS the bits must * be output in 16-bit coding units instead of 8-bit coding units, and that in * LZMS the first coding unit is not ignored by the decompressor, so the encoder * cannot output a dummy value to that position. * * The basic idea is that we're writing bits from @rc->low to the output. * However, due to carrying, the writing of coding units with value 0xffff, as * well as one prior coding unit, must be delayed until it is determined whether * a carry is needed. */ static void lzms_range_encoder_raw_shift_low(struct lzms_range_encoder_raw *rc) { LZMS_DEBUG("low=%"PRIx64", cache=%"PRIx64", cache_size=%u", rc->low, rc->cache, rc->cache_size); if ((u32)(rc->low) < 0xffff0000 || (u32)(rc->low >> 32) != 0) { /* Carry not needed (rc->low < 0xffff0000), or carry occurred * ((rc->low >> 32) != 0, a.k.a. the carry bit is 1). */ do { if (!rc->first) { if (rc->num_le16_remaining == 0) { rc->overrun = true; return; } *rc->out++ = cpu_to_le16(rc->cache + (u16)(rc->low >> 32)); --rc->num_le16_remaining; } else { rc->first = false; } rc->cache = 0xffff; } while (--rc->cache_size != 0); rc->cache = (rc->low >> 16) & 0xffff; } ++rc->cache_size; rc->low = (rc->low & 0xffff) << 16; } static void lzms_range_encoder_raw_normalize(struct lzms_range_encoder_raw *rc) { if (rc->range <= 0xffff) { rc->range <<= 16; lzms_range_encoder_raw_shift_low(rc); } } static bool lzms_range_encoder_raw_flush(struct lzms_range_encoder_raw *rc) { for (unsigned i = 0; i < 4; i++) lzms_range_encoder_raw_shift_low(rc); return !rc->overrun; } /* Encode the next bit using the range encoder (raw version). * * @prob is the chance out of LZMS_PROBABILITY_MAX that the next bit is 0. */ static void lzms_range_encoder_raw_encode_bit(struct lzms_range_encoder_raw *rc, int bit, u32 prob) { lzms_range_encoder_raw_normalize(rc); u32 bound = (rc->range >> LZMS_PROBABILITY_BITS) * prob; if (bit == 0) { rc->range = bound; } else { rc->low += bound; rc->range -= bound; } } /* Encode a bit using the specified range encoder. This wraps around * lzms_range_encoder_raw_encode_bit() to handle using and updating the * appropriate probability table. */ static void lzms_range_encode_bit(struct lzms_range_encoder *enc, int bit) { struct lzms_probability_entry *prob_entry; u32 prob; /* Load the probability entry corresponding to the current state. */ prob_entry = &enc->prob_entries[enc->state]; /* Treat the number of zero bits in the most recently encoded * LZMS_PROBABILITY_MAX bits with this probability entry as the chance, * out of LZMS_PROBABILITY_MAX, that the next bit will be a 0. However, * don't allow 0% or 100% probabilities. */ prob = prob_entry->num_recent_zero_bits; if (prob == 0) prob = 1; else if (prob == LZMS_PROBABILITY_MAX) prob = LZMS_PROBABILITY_MAX - 1; /* Encode the next bit. */ lzms_range_encoder_raw_encode_bit(enc->rc, bit, prob); /* Update the state based on the newly encoded bit. */ enc->state = ((enc->state << 1) | bit) & enc->mask; /* Update the recent bits, including the cached count of 0's. */ BUILD_BUG_ON(LZMS_PROBABILITY_MAX > sizeof(prob_entry->recent_bits) * 8); if (bit == 0) { if (prob_entry->recent_bits & (1ULL << (LZMS_PROBABILITY_MAX - 1))) { /* Replacing 1 bit with 0 bit; increment the zero count. */ prob_entry->num_recent_zero_bits++; } } else { if (!(prob_entry->recent_bits & (1ULL << (LZMS_PROBABILITY_MAX - 1)))) { /* Replacing 0 bit with 1 bit; decrement the zero count. */ prob_entry->num_recent_zero_bits--; } } prob_entry->recent_bits = (prob_entry->recent_bits << 1) | bit; } /* Encode a symbol using the specified Huffman encoder. */ static void lzms_huffman_encode_symbol(struct lzms_huffman_encoder *enc, u32 sym) { LZMS_ASSERT(sym < enc->num_syms); if (enc->num_syms_written == enc->rebuild_freq) { /* Adaptive code needs to be rebuilt. */ LZMS_DEBUG("Rebuilding code (num_syms=%u)", enc->num_syms); make_canonical_huffman_code(enc->num_syms, LZMS_MAX_CODEWORD_LEN, enc->sym_freqs, enc->lens, enc->codewords); /* Dilute the frequencies. */ for (unsigned i = 0; i < enc->num_syms; i++) { enc->sym_freqs[i] >>= 1; enc->sym_freqs[i] += 1; } enc->num_syms_written = 0; } lzms_output_bitstream_put_bits(enc->os, enc->codewords[sym], enc->lens[sym]); ++enc->num_syms_written; ++enc->sym_freqs[sym]; } /* Encode a number as a Huffman symbol specifying a slot, plus a number of * slot-dependent extra bits. */ static void lzms_encode_value(struct lzms_huffman_encoder *enc, u32 value) { unsigned slot; unsigned num_extra_bits; u32 extra_bits; LZMS_ASSERT(enc->slot_base_tab != NULL); slot = lzms_get_slot(value, enc->slot_base_tab, enc->num_syms); /* Get the number of extra bits needed to represent the range of values * that share the slot. */ num_extra_bits = bsr32(enc->slot_base_tab[slot + 1] - enc->slot_base_tab[slot]); /* Calculate the extra bits as the offset from the slot base. */ extra_bits = value - enc->slot_base_tab[slot]; /* Output the slot (Huffman-encoded), then the extra bits (verbatim). */ lzms_huffman_encode_symbol(enc, slot); lzms_output_bitstream_put_bits(enc->os, extra_bits, num_extra_bits); } static void lzms_begin_encode_item(struct lzms_compressor *ctx) { ctx->upcoming_delta_offset = 0; ctx->upcoming_lz_offset = 0; ctx->upcoming_delta_power = 0; } static void lzms_end_encode_item(struct lzms_compressor *ctx, u32 length) { LZMS_ASSERT(ctx->window_size - ctx->cur_window_pos >= length); ctx->cur_window_pos += length; /* Update LRU queues */ if (ctx->prev_lz_offset != 0) { for (int i = LZMS_NUM_RECENT_OFFSETS - 1; i >= 0; i--) ctx->recent_lz_offsets[i + 1] = ctx->recent_lz_offsets[i]; ctx->recent_lz_offsets[0] = ctx->prev_lz_offset; } if (ctx->prev_delta_offset != 0) { for (int i = LZMS_NUM_RECENT_OFFSETS - 1; i >= 0; i--) { ctx->recent_delta_powers[i + 1] = ctx->recent_delta_powers[i]; ctx->recent_delta_offsets[i + 1] = ctx->recent_delta_offsets[i]; } ctx->recent_delta_powers[0] = ctx->prev_delta_power; ctx->recent_delta_offsets[0] = ctx->prev_delta_offset; } ctx->prev_lz_offset = ctx->upcoming_lz_offset; ctx->prev_delta_offset = ctx->upcoming_delta_offset; ctx->prev_delta_power = ctx->upcoming_delta_power; } /* Encode a literal byte. */ static void lzms_encode_literal(struct lzms_compressor *ctx, u8 literal) { LZMS_DEBUG("Position %u: Encoding literal 0x%02x ('%c')", ctx->cur_window_pos, literal, literal); lzms_begin_encode_item(ctx); /* Main bit: 0 = a literal, not a match. */ lzms_range_encode_bit(&ctx->main_range_encoder, 0); /* Encode the literal using the current literal Huffman code. */ lzms_huffman_encode_symbol(&ctx->literal_encoder, literal); lzms_end_encode_item(ctx, 1); } /* Encode a (length, offset) pair (LZ match). */ static void lzms_encode_lz_match(struct lzms_compressor *ctx, u32 length, u32 offset) { int recent_offset_idx; lzms_begin_encode_item(ctx); LZMS_DEBUG("Position %u: Encoding LZ match {length=%u, offset=%u}", ctx->cur_window_pos, length, offset); /* Main bit: 1 = a match, not a literal. */ lzms_range_encode_bit(&ctx->main_range_encoder, 1); /* Match bit: 0 = a LZ match, not a delta match. */ lzms_range_encode_bit(&ctx->match_range_encoder, 0); /* Determine if the offset can be represented as a recent offset. */ for (recent_offset_idx = 0; recent_offset_idx < LZMS_NUM_RECENT_OFFSETS; recent_offset_idx++) if (offset == ctx->recent_lz_offsets[recent_offset_idx]) break; if (recent_offset_idx == LZMS_NUM_RECENT_OFFSETS) { /* Explicit offset. */ /* LZ match bit: 0 = explicit offset, not a repeat offset. */ lzms_range_encode_bit(&ctx->lz_match_range_encoder, 0); /* Encode the match offset. */ lzms_encode_value(&ctx->lz_offset_encoder, offset); } else { int i; /* Repeat offset. */ /* LZ match bit: 1 = repeat offset, not an explicit offset. */ lzms_range_encode_bit(&ctx->lz_match_range_encoder, 1); /* Encode the recent offset index. A 1 bit is encoded for each * index passed up. This sequence of 1 bits is terminated by a * 0 bit, or automatically when (LZMS_NUM_RECENT_OFFSETS - 1) 1 * bits have been encoded. */ for (i = 0; i < recent_offset_idx; i++) lzms_range_encode_bit(&ctx->lz_repeat_match_range_encoders[i], 1); if (i < LZMS_NUM_RECENT_OFFSETS - 1) lzms_range_encode_bit(&ctx->lz_repeat_match_range_encoders[i], 0); /* Initial update of the LZ match offset LRU queue. */ for (; i < LZMS_NUM_RECENT_OFFSETS; i++) ctx->recent_lz_offsets[i] = ctx->recent_lz_offsets[i + 1]; } /* Encode the match length. */ lzms_encode_value(&ctx->length_encoder, length); /* Save the match offset for later insertion at the front of the LZ * match offset LRU queue. */ ctx->upcoming_lz_offset = offset; lzms_end_encode_item(ctx, length); } static void lzms_record_literal(u8 literal, void *_ctx) { struct lzms_compressor *ctx = _ctx; lzms_encode_literal(ctx, literal); } static void lzms_record_match(unsigned length, unsigned offset, void *_ctx) { struct lzms_compressor *ctx = _ctx; lzms_encode_lz_match(ctx, length, offset); } static void lzms_fast_encode(struct lzms_compressor *ctx) { static const struct lz_params lzms_lz_params = { .min_match = 3, .max_match = UINT_MAX, .max_offset = UINT_MAX, .nice_match = 64, .good_match = 32, .max_chain_len = 64, .max_lazy_match = 258, .too_far = 4096, }; lz_analyze_block(ctx->window, ctx->window_size, lzms_record_match, lzms_record_literal, ctx, &lzms_lz_params, ctx->prev_tab); } #if 0 static struct lzms_match lzms_get_best_match(struct lzms_compressor *ctx) { struct lzms_match match; /* TODO */ match.length = 0; return match; } static void lzms_slow_encode(struct lzms_compressor *ctx) { struct lzms_match match; /* TODO */ while (ctx->cur_window_pos != ctx->window_size) { match = lzms_get_best_match(ctx); if (match.length == 0) { /* Literal */ lzms_encode_literal(ctx, ctx->window[ctx->cur_window_pos]); } else { /* LZ match */ lzms_encode_lz_match(ctx, match.length, match.offset); } } } #endif static void lzms_init_range_encoder(struct lzms_range_encoder *enc, struct lzms_range_encoder_raw *rc, u32 num_states) { enc->rc = rc; enc->state = 0; enc->mask = num_states - 1; for (u32 i = 0; i < num_states; i++) { enc->prob_entries[i].num_recent_zero_bits = LZMS_INITIAL_PROBABILITY; enc->prob_entries[i].recent_bits = LZMS_INITIAL_RECENT_BITS; } } static void lzms_init_huffman_encoder(struct lzms_huffman_encoder *enc, struct lzms_output_bitstream *os, const u32 *slot_base_tab, unsigned num_syms, unsigned rebuild_freq) { enc->os = os; enc->slot_base_tab = slot_base_tab; enc->num_syms_written = rebuild_freq; enc->rebuild_freq = rebuild_freq; enc->num_syms = num_syms; for (unsigned i = 0; i < num_syms; i++) enc->sym_freqs[i] = 1; } /* Initialize the LZMS compressor. */ static void lzms_init_compressor(struct lzms_compressor *ctx, const u8 *udata, u32 ulen, le16 *cdata, u32 clen16) { unsigned num_position_slots; /* Copy the uncompressed data into the @ctx->window buffer. */ memcpy(ctx->window, udata, ulen); memset(&ctx->window[ulen], 0, 8); ctx->cur_window_pos = 0; ctx->window_size = ulen; /* Initialize the raw range encoder (writing forwards). */ lzms_range_encoder_raw_init(&ctx->rc, cdata, clen16); /* Initialize the output bitstream for Huffman symbols and verbatim bits * (writing backwards). */ lzms_output_bitstream_init(&ctx->os, cdata, clen16); /* Initialize position and length slot bases if not done already. */ lzms_init_slot_bases(); /* Calculate the number of position slots needed for this compressed * block. */ num_position_slots = lzms_get_position_slot(ulen - 1) + 1; LZMS_DEBUG("Using %u position slots", num_position_slots); /* Initialize Huffman encoders for each alphabet used in the compressed * representation. */ lzms_init_huffman_encoder(&ctx->literal_encoder, &ctx->os, NULL, LZMS_NUM_LITERAL_SYMS, LZMS_LITERAL_CODE_REBUILD_FREQ); lzms_init_huffman_encoder(&ctx->lz_offset_encoder, &ctx->os, lzms_position_slot_base, num_position_slots, LZMS_LZ_OFFSET_CODE_REBUILD_FREQ); lzms_init_huffman_encoder(&ctx->length_encoder, &ctx->os, lzms_length_slot_base, LZMS_NUM_LEN_SYMS, LZMS_LENGTH_CODE_REBUILD_FREQ); lzms_init_huffman_encoder(&ctx->delta_offset_encoder, &ctx->os, lzms_position_slot_base, num_position_slots, LZMS_DELTA_OFFSET_CODE_REBUILD_FREQ); lzms_init_huffman_encoder(&ctx->delta_power_encoder, &ctx->os, NULL, LZMS_NUM_DELTA_POWER_SYMS, LZMS_DELTA_POWER_CODE_REBUILD_FREQ); /* Initialize range encoders, all of which wrap around the same * lzms_range_encoder_raw. */ lzms_init_range_encoder(&ctx->main_range_encoder, &ctx->rc, LZMS_NUM_MAIN_STATES); lzms_init_range_encoder(&ctx->match_range_encoder, &ctx->rc, LZMS_NUM_MATCH_STATES); lzms_init_range_encoder(&ctx->lz_match_range_encoder, &ctx->rc, LZMS_NUM_LZ_MATCH_STATES); for (size_t i = 0; i < ARRAY_LEN(ctx->lz_repeat_match_range_encoders); i++) lzms_init_range_encoder(&ctx->lz_repeat_match_range_encoders[i], &ctx->rc, LZMS_NUM_LZ_REPEAT_MATCH_STATES); lzms_init_range_encoder(&ctx->delta_match_range_encoder, &ctx->rc, LZMS_NUM_DELTA_MATCH_STATES); for (size_t i = 0; i < ARRAY_LEN(ctx->delta_repeat_match_range_encoders); i++) lzms_init_range_encoder(&ctx->delta_repeat_match_range_encoders[i], &ctx->rc, LZMS_NUM_DELTA_REPEAT_MATCH_STATES); /* Initialize the LRU queue for recent match offsets. */ for (size_t i = 0; i < LZMS_NUM_RECENT_OFFSETS + 1; i++) ctx->recent_lz_offsets[i] = i + 1; for (size_t i = 0; i < LZMS_NUM_RECENT_OFFSETS + 1; i++) { ctx->recent_delta_powers[i] = 0; ctx->recent_delta_offsets[i] = i + 1; } ctx->prev_lz_offset = 0; ctx->prev_delta_offset = 0; ctx->prev_delta_power = 0; ctx->upcoming_lz_offset = 0; ctx->upcoming_delta_offset = 0; ctx->upcoming_delta_power = 0; } /* Flush the output streams, prepare the final compressed data, and return its * size in bytes. * * A return value of 0 indicates that the data could not be compressed to fit in * the available space. */ static size_t lzms_finalize(struct lzms_compressor *ctx, u8 *cdata, size_t csize_avail) { size_t num_forwards_bytes; size_t num_backwards_bytes; size_t compressed_size; /* Flush both the forwards and backwards streams, and make sure they * didn't cross each other and start overwriting each other's data. */ if (!lzms_output_bitstream_flush(&ctx->os)) { LZMS_DEBUG("Backwards bitstream overrun."); return 0; } if (!lzms_range_encoder_raw_flush(&ctx->rc)) { LZMS_DEBUG("Forwards bitstream overrun."); return 0; } if (ctx->rc.out > ctx->os.out) { LZMS_DEBUG("Two bitstreams crossed."); return 0; } /* Now the compressed buffer contains the data output by the forwards * bitstream, then empty space, then data output by the backwards * bitstream. Move the data output by the forwards bitstream to be * adjacent to the data output by the backwards bitstream, and calculate * the compressed size that this results in. */ num_forwards_bytes = (u8*)ctx->rc.out - (u8*)cdata; num_backwards_bytes = ((u8*)cdata + csize_avail) - (u8*)ctx->os.out; memmove(cdata + num_forwards_bytes, ctx->os.out, num_backwards_bytes); compressed_size = num_forwards_bytes + num_backwards_bytes; LZMS_DEBUG("num_forwards_bytes=%zu, num_backwards_bytes=%zu, " "compressed_size=%zu", num_forwards_bytes, num_backwards_bytes, compressed_size); LZMS_ASSERT(!(compressed_size & 1)); return compressed_size; } static size_t lzms_compress(const void *uncompressed_data, size_t uncompressed_size, void *compressed_data, size_t compressed_size_avail, void *_ctx) { struct lzms_compressor *ctx = _ctx; size_t compressed_size; LZMS_DEBUG("uncompressed_size=%zu, compressed_size_avail=%zu", uncompressed_size, compressed_size_avail); /* Make sure the uncompressed size is compatible with this compressor. */ if (uncompressed_size > ctx->max_block_size) { LZMS_DEBUG("Can't compress %zu bytes: LZMS context " "only supports %u bytes", uncompressed_size, ctx->max_block_size); return 0; } /* Don't bother compressing extremely small inputs. */ if (uncompressed_size < 4) return 0; /* Cap the available compressed size to a 32-bit integer, and round it * down to the nearest multiple of 2. */ if (compressed_size_avail > UINT32_MAX) compressed_size_avail = UINT32_MAX; if (compressed_size_avail & 1) compressed_size_avail--; /* Initialize the compressor structures. */ lzms_init_compressor(ctx, uncompressed_data, uncompressed_size, compressed_data, compressed_size_avail / 2); /* Preprocess the uncompressed data. */ lzms_x86_filter(ctx->window, ctx->window_size, ctx->last_target_usages, false); /* Determine and output a literal/match sequence that decompresses to * the preprocessed data. */ lzms_fast_encode(ctx); /* Get and return the compressed data size. */ compressed_size = lzms_finalize(ctx, compressed_data, compressed_size_avail); if (compressed_size == 0) { LZMS_DEBUG("Data did not compress to requested size or less."); return 0; } LZMS_DEBUG("Compressed %zu => %zu bytes", uncompressed_size, compressed_size); #if defined(ENABLE_VERIFY_COMPRESSION) || defined(ENABLE_LZMS_DEBUG) /* Verify that we really get the same thing back when decompressing. */ { struct wimlib_decompressor *decompressor; LZMS_DEBUG("Verifying LZMS compression."); if (0 == wimlib_create_decompressor(WIMLIB_COMPRESSION_TYPE_LZMS, ctx->max_block_size, NULL, &decompressor)) { int ret; ret = wimlib_decompress(compressed_data, compressed_size, ctx->window, uncompressed_size, decompressor); wimlib_free_decompressor(decompressor); if (ret) { ERROR("Failed to decompress data we " "compressed using LZMS algorithm"); wimlib_assert(0); return 0; } if (memcmp(uncompressed_data, ctx->window, uncompressed_size)) { ERROR("Data we compressed using LZMS algorithm " "didn't decompress to original"); wimlib_assert(0); return 0; } } else { WARNING("Failed to create decompressor for " "data verification!"); } } #endif /* ENABLE_LZMS_DEBUG || ENABLE_VERIFY_COMPRESSION */ return compressed_size; } static void lzms_free_compressor(void *_ctx) { struct lzms_compressor *ctx = _ctx; if (ctx) { FREE(ctx->window); FREE(ctx->prev_tab); FREE(ctx); } } static int lzms_create_compressor(size_t max_block_size, const struct wimlib_compressor_params_header *params, void **ctx_ret) { struct lzms_compressor *ctx; if (max_block_size == 0 || max_block_size >= INT32_MAX) { LZMS_DEBUG("Invalid max_block_size (%u)", max_block_size); return WIMLIB_ERR_INVALID_PARAM; } ctx = CALLOC(1, sizeof(struct lzms_compressor)); if (ctx == NULL) goto oom; ctx->window = MALLOC(max_block_size + 8); if (ctx->window == NULL) goto oom; ctx->prev_tab = MALLOC(max_block_size * sizeof(ctx->prev_tab[0])); if (ctx->prev_tab == NULL) goto oom; ctx->max_block_size = max_block_size; *ctx_ret = ctx; return 0; oom: lzms_free_compressor(ctx); return WIMLIB_ERR_NOMEM; } const struct compressor_ops lzms_compressor_ops = { .create_compressor = lzms_create_compressor, .compress = lzms_compress, .free_compressor = lzms_free_compressor, };