+++ /dev/null
-/*
- * lzms-compress.c
- *
- * A compressor that produces output compatible with the LZMS compression format.
- */
-
-/*
- * Copyright (C) 2013, 2014 Eric Biggers
- *
- * This file is free software; you can redistribute it and/or modify it under
- * the terms of the GNU Lesser General Public License as published by the Free
- * Software Foundation; either version 3 of the License, or (at your option) any
- * later version.
- *
- * This file 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 Lesser General Public License for more
- * details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this file; if not, see http://www.gnu.org/licenses/.
- */
-
-#ifdef HAVE_CONFIG_H
-# include "config.h"
-#endif
-
-#include "wimlib/compress_common.h"
-#include "wimlib/compressor_ops.h"
-#include "wimlib/endianness.h"
-#include "wimlib/error.h"
-#include "wimlib/lz_mf.h"
-#include "wimlib/lz_repsearch.h"
-#include "wimlib/lzms.h"
-#include "wimlib/unaligned.h"
-#include "wimlib/util.h"
-
-#include <string.h>
-#include <limits.h>
-#include <pthread.h>
-
-/* Stucture used for writing raw bits as a series of 16-bit little endian coding
- * units. This starts at the *end* of the compressed data buffer and proceeds
- * backwards. */
-struct lzms_output_bitstream {
-
- /* Bits that haven't yet been written to the output buffer. */
- u64 bitbuf;
-
- /* Number of bits currently held in @bitbuf. */
- unsigned bitcount;
-
- /* Pointer to one past the next position in the compressed data buffer
- * at which to output a 16-bit coding unit. */
- le16 *next;
-
- /* Pointer to the beginning of the output buffer. (The "end" when
- * writing backwards!) */
- le16 *begin;
-};
-
-/* Stucture used for range encoding (raw version). This starts at the
- * *beginning* of the compressed data buffer and proceeds forward. */
-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 beginning of the output buffer. */
- le16 *begin;
-
- /* Pointer to the position in the output buffer at which the next coding
- * unit must be written. */
- le16 *next;
-
- /* Pointer just past the end of the output buffer. */
- le16 *end;
-};
-
-/* 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 is used as an
- * 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. */
-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;
-
- /* 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. */
- u32 codewords[LZMS_MAX_NUM_SYMS];
-};
-
-/* Internal compression parameters */
-struct lzms_compressor_params {
- u32 min_match_length;
- u32 nice_match_length;
- u32 max_search_depth;
- u32 optim_array_length;
-};
-
-/* State of the LZMS compressor */
-struct lzms_compressor {
-
- /* Internal compression parameters */
- struct lzms_compressor_params params;
-
- /* Data currently being compressed */
- u8 *cur_window;
- u32 cur_window_size;
-
- /* Lempel-Ziv match-finder */
- struct lz_mf *mf;
-
- /* Temporary space to store found matches */
- struct lz_match *matches;
-
- /* Per-position data for near-optimal parsing */
- struct lzms_mc_pos_data *optimum;
- struct lzms_mc_pos_data *optimum_end;
-
- /* 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;
-
- /* Used for preprocessing */
- s32 last_target_usages[65536];
-
-#define LZMS_NUM_FAST_LENGTHS 256
- /* Table: length => length slot for small lengths */
- u8 length_slot_fast[LZMS_NUM_FAST_LENGTHS];
-
- /* Table: length => current cost for small match lengths */
- u32 length_cost_fast[LZMS_NUM_FAST_LENGTHS];
-
-#define LZMS_NUM_FAST_OFFSETS 32768
- /* Table: offset => offset slot for small offsets */
- u8 offset_slot_fast[LZMS_NUM_FAST_OFFSETS];
-};
-
-struct lzms_lz_lru_queue {
- u32 recent_offsets[LZMS_NUM_RECENT_OFFSETS + 1];
- u32 prev_offset;
- u32 upcoming_offset;
-};
-
-static void
-lzms_init_lz_lru_queue(struct lzms_lz_lru_queue *queue)
-{
- for (int i = 0; i < LZMS_NUM_RECENT_OFFSETS + 1; i++)
- queue->recent_offsets[i] = i + 1;
-
- queue->prev_offset = 0;
- queue->upcoming_offset = 0;
-}
-
-static void
-lzms_update_lz_lru_queue(struct lzms_lz_lru_queue *queue)
-{
- if (queue->prev_offset != 0) {
- for (int i = LZMS_NUM_RECENT_OFFSETS - 1; i >= 0; i--)
- queue->recent_offsets[i + 1] = queue->recent_offsets[i];
- queue->recent_offsets[0] = queue->prev_offset;
- }
- queue->prev_offset = queue->upcoming_offset;
-}
-
-/*
- * Match chooser position data:
- *
- * An array of these structures is used during the near-optimal match-choosing
- * algorithm. They correspond to consecutive positions in the window and are
- * used to keep track of the cost to reach each position, and the match/literal
- * choices that need to be chosen to reach that position.
- */
-struct lzms_mc_pos_data {
-
- /* The cost, in bits, of the lowest-cost path that has been found to
- * reach this position. This can change as progressively lower cost
- * paths are found to reach this position. */
- u32 cost;
-#define MC_INFINITE_COST UINT32_MAX
-
- /* The match or literal that was taken to reach this position. This can
- * change as progressively lower cost paths are found to reach this
- * position.
- *
- * This variable is divided into two bitfields.
- *
- * Literals:
- * Low bits are 1, high bits are the literal.
- *
- * Explicit offset matches:
- * Low bits are the match length, high bits are the offset plus 2.
- *
- * Repeat offset matches:
- * Low bits are the match length, high bits are the queue index.
- */
- u64 mc_item_data;
-#define MC_OFFSET_SHIFT 32
-#define MC_LEN_MASK (((u64)1 << MC_OFFSET_SHIFT) - 1)
-
- /* The LZMS adaptive state that exists at this position. This is filled
- * in lazily, only after the minimum-cost path to this position is
- * found.
- *
- * Note: the way we handle this adaptive state in the "minimum-cost"
- * parse is actually only an approximation. It's possible for the
- * globally optimal, minimum cost path to contain a prefix, ending at a
- * position, where that path prefix is *not* the minimum cost path to
- * that position. This can happen if such a path prefix results in a
- * different adaptive state which results in lower costs later. We do
- * not solve this problem; we only consider the lowest cost to reach
- * each position, which seems to be an acceptable approximation.
- *
- * Note: this adaptive state also does not include the probability
- * entries or current Huffman codewords. Those aren't maintained
- * per-position and are only updated occassionally. */
- struct lzms_adaptive_state {
- struct lzms_lz_lru_queue lru;
- u8 main_state;
- u8 match_state;
- u8 lz_match_state;
- u8 lz_repeat_match_state[LZMS_NUM_RECENT_OFFSETS - 1];
- } state;
-};
-
-static void
-lzms_init_fast_slots(struct lzms_compressor *c)
-{
- /* Create table mapping small lengths to length slots. */
- for (unsigned slot = 0, i = 0; i < LZMS_NUM_FAST_LENGTHS; i++) {
- while (i >= lzms_length_slot_base[slot + 1])
- slot++;
- c->length_slot_fast[i] = slot;
- }
-
- /* Create table mapping small offsets to offset slots. */
- for (unsigned slot = 0, i = 0; i < LZMS_NUM_FAST_OFFSETS; i++) {
- while (i >= lzms_offset_slot_base[slot + 1])
- slot++;
- c->offset_slot_fast[i] = slot;
- }
-}
-
-static inline unsigned
-lzms_get_length_slot_fast(const struct lzms_compressor *c, u32 length)
-{
- if (likely(length < LZMS_NUM_FAST_LENGTHS))
- return c->length_slot_fast[length];
- else
- return lzms_get_length_slot(length);
-}
-
-static inline unsigned
-lzms_get_offset_slot_fast(const struct lzms_compressor *c, u32 offset)
-{
- if (offset < LZMS_NUM_FAST_OFFSETS)
- return c->offset_slot_fast[offset];
- else
- return lzms_get_offset_slot(offset);
-}
-
-/* Initialize the output bitstream @os to write backwards 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->bitcount = 0;
- os->next = out + out_limit;
- os->begin = out;
-}
-
-/*
- * Write some bits, contained in the low @num_bits bits of @bits (ordered from
- * high-order to low-order), to the output bitstream @os.
- *
- * @max_num_bits is a compile-time constant that specifies the maximum number of
- * bits that can ever be written at this call site.
- */
-static inline void
-lzms_output_bitstream_put_varbits(struct lzms_output_bitstream *os,
- u32 bits, unsigned num_bits,
- unsigned max_num_bits)
-{
- LZMS_ASSERT(num_bits <= 48);
-
- /* Add the bits to the bit buffer variable. */
- os->bitcount += num_bits;
- os->bitbuf = (os->bitbuf << num_bits) | bits;
-
- /* Check whether any coding units need to be written. */
- while (os->bitcount >= 16) {
-
- os->bitcount -= 16;
-
- /* Write a coding unit, unless it would underflow the buffer. */
- if (os->next != os->begin)
- put_unaligned_u16_le(os->bitbuf >> os->bitcount, --os->next);
-
- /* Optimization for call sites that never write more than 16
- * bits at once. */
- if (max_num_bits <= 16)
- break;
- }
-}
-
-/* Flush the output bitstream, ensuring that all bits written to it have been
- * written to memory. Returns %true if all bits have been output successfully,
- * or %false if an overrun occurred. */
-static bool
-lzms_output_bitstream_flush(struct lzms_output_bitstream *os)
-{
- if (os->next == os->begin)
- return false;
-
- if (os->bitcount != 0)
- put_unaligned_u16_le(os->bitbuf << (16 - os->bitcount), --os->next);
-
- return true;
-}
-
-/* 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->begin = out;
- rc->next = out - 1;
- rc->end = out + out_limit;
-}
-
-/*
- * 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)
-{
- 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 (likely(rc->next >= rc->begin)) {
- if (rc->next != rc->end) {
- put_unaligned_u16_le(rc->cache +
- (u16)(rc->low >> 32),
- rc->next++);
- }
- } else {
- rc->next++;
- }
- 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->next != rc->end;
-}
-
-/* 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 inline 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 state and probability entry. */
-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];
-
- /* Update the state based on the next bit. */
- enc->state = ((enc->state << 1) | bit) & enc->mask;
-
- /* Get the probability that the bit is 0. */
- prob = lzms_get_probability(prob_entry);
-
- /* Update the probability entry. */
- lzms_update_probability_entry(prob_entry, bit);
-
- /* Encode the bit. */
- lzms_range_encoder_raw_encode_bit(enc->rc, bit, prob);
-}
-
-/* Called when an adaptive Huffman code needs to be rebuilt. */
-static void
-lzms_rebuild_huffman_code(struct lzms_huffman_encoder *enc)
-{
- 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;
-}
-
-/* Encode a symbol using the specified Huffman encoder. */
-static inline void
-lzms_huffman_encode_symbol(struct lzms_huffman_encoder *enc, unsigned sym)
-{
- lzms_output_bitstream_put_varbits(enc->os,
- enc->codewords[sym],
- enc->lens[sym],
- LZMS_MAX_CODEWORD_LEN);
- ++enc->sym_freqs[sym];
- if (++enc->num_syms_written == enc->rebuild_freq)
- lzms_rebuild_huffman_code(enc);
-}
-
-static void
-lzms_update_fast_length_costs(struct lzms_compressor *c);
-
-/* Encode a match length. */
-static void
-lzms_encode_length(struct lzms_compressor *c, u32 length)
-{
- unsigned slot;
- unsigned num_extra_bits;
- u32 extra_bits;
-
- slot = lzms_get_length_slot_fast(c, length);
-
- extra_bits = length - lzms_length_slot_base[slot];
- num_extra_bits = lzms_extra_length_bits[slot];
-
- lzms_huffman_encode_symbol(&c->length_encoder, slot);
- if (c->length_encoder.num_syms_written == 0)
- lzms_update_fast_length_costs(c);
-
- lzms_output_bitstream_put_varbits(c->length_encoder.os,
- extra_bits, num_extra_bits, 30);
-}
-
-/* Encode an LZ match offset. */
-static void
-lzms_encode_lz_offset(struct lzms_compressor *c, u32 offset)
-{
- unsigned slot;
- unsigned num_extra_bits;
- u32 extra_bits;
-
- slot = lzms_get_offset_slot_fast(c, offset);
-
- extra_bits = offset - lzms_offset_slot_base[slot];
- num_extra_bits = lzms_extra_offset_bits[slot];
-
- lzms_huffman_encode_symbol(&c->lz_offset_encoder, slot);
- lzms_output_bitstream_put_varbits(c->lz_offset_encoder.os,
- extra_bits, num_extra_bits, 30);
-}
-
-/* Encode a literal byte. */
-static void
-lzms_encode_literal(struct lzms_compressor *c, unsigned literal)
-{
- /* Main bit: 0 = a literal, not a match. */
- lzms_range_encode_bit(&c->main_range_encoder, 0);
-
- /* Encode the literal using the current literal Huffman code. */
- lzms_huffman_encode_symbol(&c->literal_encoder, literal);
-}
-
-/* Encode an LZ repeat offset match. */
-static void
-lzms_encode_lz_repeat_offset_match(struct lzms_compressor *c,
- u32 length, unsigned rep_index)
-{
- unsigned i;
-
- /* Main bit: 1 = a match, not a literal. */
- lzms_range_encode_bit(&c->main_range_encoder, 1);
-
- /* Match bit: 0 = an LZ match, not a delta match. */
- lzms_range_encode_bit(&c->match_range_encoder, 0);
-
- /* LZ match bit: 1 = repeat offset, not an explicit offset. */
- lzms_range_encode_bit(&c->lz_match_range_encoder, 1);
-
- /* Encode the repeat 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 < rep_index; i++)
- lzms_range_encode_bit(&c->lz_repeat_match_range_encoders[i], 1);
-
- if (i < LZMS_NUM_RECENT_OFFSETS - 1)
- lzms_range_encode_bit(&c->lz_repeat_match_range_encoders[i], 0);
-
- /* Encode the match length. */
- lzms_encode_length(c, length);
-}
-
-/* Encode an LZ explicit offset match. */
-static void
-lzms_encode_lz_explicit_offset_match(struct lzms_compressor *c,
- u32 length, u32 offset)
-{
- /* Main bit: 1 = a match, not a literal. */
- lzms_range_encode_bit(&c->main_range_encoder, 1);
-
- /* Match bit: 0 = an LZ match, not a delta match. */
- lzms_range_encode_bit(&c->match_range_encoder, 0);
-
- /* LZ match bit: 0 = explicit offset, not a repeat offset. */
- lzms_range_encode_bit(&c->lz_match_range_encoder, 0);
-
- /* Encode the match offset. */
- lzms_encode_lz_offset(c, offset);
-
- /* Encode the match length. */
- lzms_encode_length(c, length);
-}
-
-static void
-lzms_encode_item(struct lzms_compressor *c, u64 mc_item_data)
-{
- u32 len = mc_item_data & MC_LEN_MASK;
- u32 offset_data = mc_item_data >> MC_OFFSET_SHIFT;
-
- if (len == 1)
- lzms_encode_literal(c, offset_data);
- else if (offset_data < LZMS_NUM_RECENT_OFFSETS)
- lzms_encode_lz_repeat_offset_match(c, len, offset_data);
- else
- lzms_encode_lz_explicit_offset_match(c, len, offset_data - LZMS_OFFSET_OFFSET);
-}
-
-/* Encode a list of matches and literals chosen by the parsing algorithm. */
-static void
-lzms_encode_item_list(struct lzms_compressor *c,
- struct lzms_mc_pos_data *cur_optimum_ptr)
-{
- struct lzms_mc_pos_data *end_optimum_ptr;
- u64 saved_item;
- u64 item;
-
- /* The list is currently in reverse order (last item to first item).
- * Reverse it. */
- end_optimum_ptr = cur_optimum_ptr;
- saved_item = cur_optimum_ptr->mc_item_data;
- do {
- item = saved_item;
- cur_optimum_ptr -= item & MC_LEN_MASK;
- saved_item = cur_optimum_ptr->mc_item_data;
- cur_optimum_ptr->mc_item_data = item;
- } while (cur_optimum_ptr != c->optimum);
-
- /* Walk the list of items from beginning to end, encoding each item. */
- do {
- lzms_encode_item(c, cur_optimum_ptr->mc_item_data);
- cur_optimum_ptr += (cur_optimum_ptr->mc_item_data) & MC_LEN_MASK;
- } while (cur_optimum_ptr != end_optimum_ptr);
-}
-
-/* Each bit costs 1 << LZMS_COST_SHIFT units. */
-#define LZMS_COST_SHIFT 6
-
-/*#define LZMS_RC_COSTS_USE_FLOATING_POINT*/
-
-static u32
-lzms_rc_costs[LZMS_PROBABILITY_MAX + 1];
-
-#ifdef LZMS_RC_COSTS_USE_FLOATING_POINT
-# include <math.h>
-#endif
-
-static void
-lzms_do_init_rc_costs(void)
-{
- /* Fill in a table that maps range coding probabilities needed to code a
- * bit X (0 or 1) to the number of bits (scaled by a constant factor, to
- * handle fractional costs) needed to code that bit X.
- *
- * Consider the range of the range decoder. To eliminate exactly half
- * the range (logical probability of 0.5), we need exactly 1 bit. For
- * lower probabilities we need more bits and for higher probabilities we
- * need fewer bits. In general, a logical probability of N will
- * eliminate the proportion 1 - N of the range; this information takes
- * log2(1 / N) bits to encode.
- *
- * The below loop is simply calculating this number of bits for each
- * possible probability allowed by the LZMS compression format, but
- * without using real numbers. To handle fractional probabilities, each
- * cost is multiplied by (1 << LZMS_COST_SHIFT). These techniques are
- * based on those used by LZMA.
- *
- * Note that in LZMS, a probability x really means x / 64, and 0 / 64 is
- * really interpreted as 1 / 64 and 64 / 64 is really interpreted as
- * 63 / 64.
- */
- for (u32 i = 0; i <= LZMS_PROBABILITY_MAX; i++) {
- u32 prob = i;
-
- if (prob == 0)
- prob = 1;
- else if (prob == LZMS_PROBABILITY_MAX)
- prob = LZMS_PROBABILITY_MAX - 1;
-
- #ifdef LZMS_RC_COSTS_USE_FLOATING_POINT
- lzms_rc_costs[i] = log2((double)LZMS_PROBABILITY_MAX / prob) *
- (1 << LZMS_COST_SHIFT);
- #else
- u32 w = prob;
- u32 bit_count = 0;
- for (u32 j = 0; j < LZMS_COST_SHIFT; j++) {
- w *= w;
- bit_count <<= 1;
- while (w >= ((u32)1 << 16)) {
- w >>= 1;
- ++bit_count;
- }
- }
- lzms_rc_costs[i] = (LZMS_PROBABILITY_BITS << LZMS_COST_SHIFT) -
- (15 + bit_count);
- #endif
- }
-}
-
-static void
-lzms_init_rc_costs(void)
-{
- static pthread_once_t once = PTHREAD_ONCE_INIT;
-
- pthread_once(&once, lzms_do_init_rc_costs);
-}
-
-/* Return the cost to range-encode the specified bit from the specified state.*/
-static inline u32
-lzms_rc_bit_cost(const struct lzms_range_encoder *enc, u8 cur_state, int bit)
-{
- u32 prob_zero;
- u32 prob_correct;
-
- prob_zero = enc->prob_entries[cur_state].num_recent_zero_bits;
-
- if (bit == 0)
- prob_correct = prob_zero;
- else
- prob_correct = LZMS_PROBABILITY_MAX - prob_zero;
-
- return lzms_rc_costs[prob_correct];
-}
-
-/* Return the cost to Huffman-encode the specified symbol. */
-static inline u32
-lzms_huffman_symbol_cost(const struct lzms_huffman_encoder *enc, unsigned sym)
-{
- return (u32)enc->lens[sym] << LZMS_COST_SHIFT;
-}
-
-/* Return the cost to encode the specified literal byte. */
-static inline u32
-lzms_literal_cost(const struct lzms_compressor *c, unsigned literal,
- const struct lzms_adaptive_state *state)
-{
- return lzms_rc_bit_cost(&c->main_range_encoder, state->main_state, 0) +
- lzms_huffman_symbol_cost(&c->literal_encoder, literal);
-}
-
-/* Update the table that directly provides the costs for small lengths. */
-static void
-lzms_update_fast_length_costs(struct lzms_compressor *c)
-{
- u32 len;
- int slot = -1;
- u32 cost = 0;
-
- for (len = 1; len < LZMS_NUM_FAST_LENGTHS; len++) {
-
- while (len >= lzms_length_slot_base[slot + 1]) {
- slot++;
- cost = (u32)(c->length_encoder.lens[slot] +
- lzms_extra_length_bits[slot]) << LZMS_COST_SHIFT;
- }
-
- c->length_cost_fast[len] = cost;
- }
-}
-
-/* Return the cost to encode the specified match length, which must be less than
- * LZMS_NUM_FAST_LENGTHS. */
-static inline u32
-lzms_fast_length_cost(const struct lzms_compressor *c, u32 length)
-{
- LZMS_ASSERT(length < LZMS_NUM_FAST_LENGTHS);
- return c->length_cost_fast[length];
-}
-
-/* Return the cost to encode the specified LZ match offset. */
-static inline u32
-lzms_lz_offset_cost(const struct lzms_compressor *c, u32 offset)
-{
- unsigned slot = lzms_get_offset_slot_fast(c, offset);
-
- return (u32)(c->lz_offset_encoder.lens[slot] +
- lzms_extra_offset_bits[slot]) << LZMS_COST_SHIFT;
-}
-
-/*
- * Consider coding the match at repeat offset index @rep_idx. Consider each
- * length from the minimum (2) to the full match length (@rep_len).
- */
-static inline void
-lzms_consider_lz_repeat_offset_match(const struct lzms_compressor *c,
- struct lzms_mc_pos_data *cur_optimum_ptr,
- u32 rep_len, unsigned rep_idx)
-{
- u32 len;
- u32 base_cost;
- u32 cost;
- unsigned i;
-
- base_cost = cur_optimum_ptr->cost;
-
- base_cost += lzms_rc_bit_cost(&c->main_range_encoder,
- cur_optimum_ptr->state.main_state, 1);
-
- base_cost += lzms_rc_bit_cost(&c->match_range_encoder,
- cur_optimum_ptr->state.match_state, 0);
-
- base_cost += lzms_rc_bit_cost(&c->lz_match_range_encoder,
- cur_optimum_ptr->state.lz_match_state, 1);
-
- for (i = 0; i < rep_idx; i++)
- base_cost += lzms_rc_bit_cost(&c->lz_repeat_match_range_encoders[i],
- cur_optimum_ptr->state.lz_repeat_match_state[i], 1);
-
- if (i < LZMS_NUM_RECENT_OFFSETS - 1)
- base_cost += lzms_rc_bit_cost(&c->lz_repeat_match_range_encoders[i],
- cur_optimum_ptr->state.lz_repeat_match_state[i], 0);
-
- len = 2;
- do {
- cost = base_cost + lzms_fast_length_cost(c, len);
- if (cost < (cur_optimum_ptr + len)->cost) {
- (cur_optimum_ptr + len)->mc_item_data =
- ((u64)rep_idx << MC_OFFSET_SHIFT) | len;
- (cur_optimum_ptr + len)->cost = cost;
- }
- } while (++len <= rep_len);
-}
-
-/*
- * Consider coding each match in @matches as an explicit offset match.
- *
- * @matches must be sorted by strictly increasing length and strictly increasing
- * offset. This is guaranteed by the match-finder.
- *
- * We consider each length from the minimum (2) to the longest
- * (matches[num_matches - 1].len). For each length, we consider only the
- * smallest offset for which that length is available. Although this is not
- * guaranteed to be optimal due to the possibility of a larger offset costing
- * less than a smaller offset to code, this is a very useful heuristic.
- */
-static inline void
-lzms_consider_lz_explicit_offset_matches(const struct lzms_compressor *c,
- struct lzms_mc_pos_data *cur_optimum_ptr,
- const struct lz_match matches[],
- u32 num_matches)
-{
- u32 len;
- u32 i;
- u32 base_cost;
- u32 position_cost;
- u32 cost;
-
- base_cost = cur_optimum_ptr->cost;
-
- base_cost += lzms_rc_bit_cost(&c->main_range_encoder,
- cur_optimum_ptr->state.main_state, 1);
-
- base_cost += lzms_rc_bit_cost(&c->match_range_encoder,
- cur_optimum_ptr->state.match_state, 0);
-
- base_cost += lzms_rc_bit_cost(&c->lz_match_range_encoder,
- cur_optimum_ptr->state.lz_match_state, 0);
- len = 2;
- i = 0;
- do {
- position_cost = base_cost + lzms_lz_offset_cost(c, matches[i].offset);
- do {
- cost = position_cost + lzms_fast_length_cost(c, len);
- if (cost < (cur_optimum_ptr + len)->cost) {
- (cur_optimum_ptr + len)->mc_item_data =
- ((u64)(matches[i].offset + LZMS_OFFSET_OFFSET)
- << MC_OFFSET_SHIFT) | len;
- (cur_optimum_ptr + len)->cost = cost;
- }
- } while (++len <= matches[i].len);
- } while (++i != num_matches);
-}
-
-static void
-lzms_init_adaptive_state(struct lzms_adaptive_state *state)
-{
- unsigned i;
-
- lzms_init_lz_lru_queue(&state->lru);
- state->main_state = 0;
- state->match_state = 0;
- state->lz_match_state = 0;
- for (i = 0; i < LZMS_NUM_RECENT_OFFSETS - 1; i++)
- state->lz_repeat_match_state[i] = 0;
-}
-
-static inline void
-lzms_update_main_state(struct lzms_adaptive_state *state, int is_match)
-{
- state->main_state = ((state->main_state << 1) | is_match) % LZMS_NUM_MAIN_STATES;
-}
-
-static inline void
-lzms_update_match_state(struct lzms_adaptive_state *state, int is_delta)
-{
- state->match_state = ((state->match_state << 1) | is_delta) % LZMS_NUM_MATCH_STATES;
-}
-
-static inline void
-lzms_update_lz_match_state(struct lzms_adaptive_state *state, int is_repeat_offset)
-{
- state->lz_match_state = ((state->lz_match_state << 1) | is_repeat_offset) % LZMS_NUM_LZ_MATCH_STATES;
-}
-
-static inline void
-lzms_update_lz_repeat_match_state(struct lzms_adaptive_state *state, int rep_idx)
-{
- int i;
-
- for (i = 0; i < rep_idx; i++)
- state->lz_repeat_match_state[i] =
- ((state->lz_repeat_match_state[i] << 1) | 1) %
- LZMS_NUM_LZ_REPEAT_MATCH_STATES;
-
- if (i < LZMS_NUM_RECENT_OFFSETS - 1)
- state->lz_repeat_match_state[i] =
- ((state->lz_repeat_match_state[i] << 1) | 0) %
- LZMS_NUM_LZ_REPEAT_MATCH_STATES;
-}
-
-/*
- * The main near-optimal parsing routine.
- *
- * Briefly, the algorithm does an approximate minimum-cost path search to find a
- * "near-optimal" sequence of matches and literals to output, based on the
- * current cost model. The algorithm steps forward, position by position (byte
- * by byte), and updates the minimum cost path to reach each later position that
- * can be reached using a match or literal from the current position. This is
- * essentially Dijkstra's algorithm in disguise: the graph nodes are positions,
- * the graph edges are possible matches/literals to code, and the cost of each
- * edge is the estimated number of bits that will be required to output the
- * corresponding match or literal. But one difference is that we actually
- * compute the lowest-cost path in pieces, where each piece is terminated when
- * there are no choices to be made.
- *
- * Notes:
- *
- * - This does not output any delta matches.
- *
- * - The costs of literals and matches are estimated using the range encoder
- * states and the semi-adaptive Huffman codes. Except for range encoding
- * states, costs are assumed to be constant throughout a single run of the
- * parsing algorithm, which can parse up to @optim_array_length bytes of data.
- * This introduces a source of inaccuracy because the probabilities and
- * Huffman codes can change over this part of the data.
- */
-static void
-lzms_near_optimal_parse(struct lzms_compressor *c)
-{
- const u8 *window_ptr;
- const u8 *window_end;
- struct lzms_mc_pos_data *cur_optimum_ptr;
- struct lzms_mc_pos_data *end_optimum_ptr;
- u32 num_matches;
- u32 longest_len;
- u32 rep_max_len;
- unsigned rep_max_idx;
- unsigned literal;
- unsigned i;
- u32 cost;
- u32 len;
- u32 offset_data;
-
- window_ptr = c->cur_window;
- window_end = window_ptr + c->cur_window_size;
-
- lzms_init_adaptive_state(&c->optimum[0].state);
-
-begin:
- /* Start building a new list of items, which will correspond to the next
- * piece of the overall minimum-cost path. */
-
- cur_optimum_ptr = c->optimum;
- cur_optimum_ptr->cost = 0;
- end_optimum_ptr = cur_optimum_ptr;
-
- /* States should currently be consistent with the encoders. */
- LZMS_ASSERT(cur_optimum_ptr->state.main_state == c->main_range_encoder.state);
- LZMS_ASSERT(cur_optimum_ptr->state.match_state == c->match_range_encoder.state);
- LZMS_ASSERT(cur_optimum_ptr->state.lz_match_state == c->lz_match_range_encoder.state);
- for (i = 0; i < LZMS_NUM_RECENT_OFFSETS - 1; i++)
- LZMS_ASSERT(cur_optimum_ptr->state.lz_repeat_match_state[i] ==
- c->lz_repeat_match_range_encoders[i].state);
-
- if (window_ptr == window_end)
- return;
-
- /* The following loop runs once for each per byte in the window, except
- * in a couple shortcut cases. */
- for (;;) {
-
- /* Find explicit offset matches with the current position. */
- num_matches = lz_mf_get_matches(c->mf, c->matches);
-
- if (num_matches) {
- /*
- * Find the longest repeat offset match with the current
- * position.
- *
- * Heuristics:
- *
- * - Only search for repeat offset matches if the
- * match-finder already found at least one match.
- *
- * - Only consider the longest repeat offset match. It
- * seems to be rare for the optimal parse to include a
- * repeat offset match that doesn't have the longest
- * length (allowing for the possibility that not all
- * of that length is actually used).
- */
- if (likely(window_ptr - c->cur_window >= LZMS_MAX_INIT_RECENT_OFFSET)) {
- BUILD_BUG_ON(LZMS_NUM_RECENT_OFFSETS != 3);
- rep_max_len = lz_repsearch3(window_ptr,
- window_end - window_ptr,
- cur_optimum_ptr->state.lru.recent_offsets,
- &rep_max_idx);
- } else {
- rep_max_len = 0;
- }
-
- if (rep_max_len) {
- /* If there's a very long repeat offset match,
- * choose it immediately. */
- if (rep_max_len >= c->params.nice_match_length) {
-
- lz_mf_skip_positions(c->mf, rep_max_len - 1);
- window_ptr += rep_max_len;
-
- if (cur_optimum_ptr != c->optimum)
- lzms_encode_item_list(c, cur_optimum_ptr);
-
- lzms_encode_lz_repeat_offset_match(c, rep_max_len,
- rep_max_idx);
-
- c->optimum[0].state = cur_optimum_ptr->state;
-
- lzms_update_main_state(&c->optimum[0].state, 1);
- lzms_update_match_state(&c->optimum[0].state, 0);
- lzms_update_lz_match_state(&c->optimum[0].state, 1);
- lzms_update_lz_repeat_match_state(&c->optimum[0].state,
- rep_max_idx);
-
- c->optimum[0].state.lru.upcoming_offset =
- c->optimum[0].state.lru.recent_offsets[rep_max_idx];
-
- for (i = rep_max_idx; i < LZMS_NUM_RECENT_OFFSETS; i++)
- c->optimum[0].state.lru.recent_offsets[i] =
- c->optimum[0].state.lru.recent_offsets[i + 1];
-
- lzms_update_lz_lru_queue(&c->optimum[0].state.lru);
- goto begin;
- }
-
- /* If reaching any positions for the first time,
- * initialize their costs to "infinity". */
- while (end_optimum_ptr < cur_optimum_ptr + rep_max_len)
- (++end_optimum_ptr)->cost = MC_INFINITE_COST;
-
- /* Consider coding a repeat offset match. */
- lzms_consider_lz_repeat_offset_match(c, cur_optimum_ptr,
- rep_max_len, rep_max_idx);
- }
-
- longest_len = c->matches[num_matches - 1].len;
-
- /* If there's a very long explicit offset match, choose
- * it immediately. */
- if (longest_len >= c->params.nice_match_length) {
-
- lz_mf_skip_positions(c->mf, longest_len - 1);
- window_ptr += longest_len;
-
- if (cur_optimum_ptr != c->optimum)
- lzms_encode_item_list(c, cur_optimum_ptr);
-
- lzms_encode_lz_explicit_offset_match(c, longest_len,
- c->matches[num_matches - 1].offset);
-
- c->optimum[0].state = cur_optimum_ptr->state;
-
- lzms_update_main_state(&c->optimum[0].state, 1);
- lzms_update_match_state(&c->optimum[0].state, 0);
- lzms_update_lz_match_state(&c->optimum[0].state, 0);
-
- c->optimum[0].state.lru.upcoming_offset =
- c->matches[num_matches - 1].offset;
-
- lzms_update_lz_lru_queue(&c->optimum[0].state.lru);
- goto begin;
- }
-
- /* If reaching any positions for the first time,
- * initialize their costs to "infinity". */
- while (end_optimum_ptr < cur_optimum_ptr + longest_len)
- (++end_optimum_ptr)->cost = MC_INFINITE_COST;
-
- /* Consider coding an explicit offset match. */
- lzms_consider_lz_explicit_offset_matches(c, cur_optimum_ptr,
- c->matches, num_matches);
- } else {
- /* No matches found. The only choice at this position
- * is to code a literal. */
-
- if (end_optimum_ptr == cur_optimum_ptr)
- (++end_optimum_ptr)->cost = MC_INFINITE_COST;
- }
-
- /* Consider coding a literal.
-
- * To avoid an extra unpredictable brench, actually checking the
- * preferability of coding a literal is integrated into the
- * adaptive state update code below. */
- literal = *window_ptr++;
- cost = cur_optimum_ptr->cost +
- lzms_literal_cost(c, literal, &cur_optimum_ptr->state);
-
- /* Advance to the next position. */
- cur_optimum_ptr++;
-
- /* The lowest-cost path to the current position is now known.
- * Finalize the adaptive state that results from taking this
- * lowest-cost path. */
-
- if (cost < cur_optimum_ptr->cost) {
- /* Literal */
- cur_optimum_ptr->cost = cost;
- cur_optimum_ptr->mc_item_data = ((u64)literal << MC_OFFSET_SHIFT) | 1;
-
- cur_optimum_ptr->state = (cur_optimum_ptr - 1)->state;
-
- lzms_update_main_state(&cur_optimum_ptr->state, 0);
-
- cur_optimum_ptr->state.lru.upcoming_offset = 0;
- } else {
- /* LZ match */
- len = cur_optimum_ptr->mc_item_data & MC_LEN_MASK;
- offset_data = cur_optimum_ptr->mc_item_data >> MC_OFFSET_SHIFT;
-
- cur_optimum_ptr->state = (cur_optimum_ptr - len)->state;
-
- lzms_update_main_state(&cur_optimum_ptr->state, 1);
- lzms_update_match_state(&cur_optimum_ptr->state, 0);
-
- if (offset_data >= LZMS_NUM_RECENT_OFFSETS) {
-
- /* Explicit offset LZ match */
-
- lzms_update_lz_match_state(&cur_optimum_ptr->state, 0);
-
- cur_optimum_ptr->state.lru.upcoming_offset =
- offset_data - LZMS_OFFSET_OFFSET;
- } else {
- /* Repeat offset LZ match */
-
- lzms_update_lz_match_state(&cur_optimum_ptr->state, 1);
- lzms_update_lz_repeat_match_state(&cur_optimum_ptr->state,
- offset_data);
-
- cur_optimum_ptr->state.lru.upcoming_offset =
- cur_optimum_ptr->state.lru.recent_offsets[offset_data];
-
- for (i = offset_data; i < LZMS_NUM_RECENT_OFFSETS; i++)
- cur_optimum_ptr->state.lru.recent_offsets[i] =
- cur_optimum_ptr->state.lru.recent_offsets[i + 1];
- }
- }
-
- lzms_update_lz_lru_queue(&cur_optimum_ptr->state.lru);
-
- /*
- * This loop will terminate when either of the following
- * conditions is true:
- *
- * (1) cur_optimum_ptr == end_optimum_ptr
- *
- * There are no paths that extend beyond the current
- * position. In this case, any path to a later position
- * must pass through the current position, so we can go
- * ahead and choose the list of items that led to this
- * position.
- *
- * (2) cur_optimum_ptr == c->optimum_end
- *
- * This bounds the number of times the algorithm can step
- * forward before it is guaranteed to start choosing items.
- * This limits the memory usage. It also guarantees that
- * the parser will not go too long without updating the
- * probability tables.
- *
- * Note: no check for end-of-window is needed because
- * end-of-window will trigger condition (1).
- */
- if (cur_optimum_ptr == end_optimum_ptr ||
- cur_optimum_ptr == c->optimum_end)
- {
- c->optimum[0].state = cur_optimum_ptr->state;
- break;
- }
- }
-
- /* Output the current list of items that constitute the minimum-cost
- * path to the current position. */
- lzms_encode_item_list(c, cur_optimum_ptr);
- goto begin;
-}
-
-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;
- LZMS_ASSERT(is_power_of_2(num_states));
- enc->mask = num_states - 1;
- lzms_init_probability_entries(enc->prob_entries, num_states);
-}
-
-static void
-lzms_init_huffman_encoder(struct lzms_huffman_encoder *enc,
- struct lzms_output_bitstream *os,
- unsigned num_syms,
- unsigned rebuild_freq)
-{
- enc->os = os;
- enc->num_syms_written = 0;
- enc->rebuild_freq = rebuild_freq;
- enc->num_syms = num_syms;
- for (unsigned i = 0; i < num_syms; i++)
- enc->sym_freqs[i] = 1;
-
- make_canonical_huffman_code(enc->num_syms,
- LZMS_MAX_CODEWORD_LEN,
- enc->sym_freqs,
- enc->lens,
- enc->codewords);
-}
-
-/* Prepare the LZMS compressor for compressing a block of data. */
-static void
-lzms_prepare_compressor(struct lzms_compressor *c, const u8 *udata, u32 ulen,
- le16 *cdata, u32 clen16)
-{
- unsigned num_offset_slots;
-
- /* Copy the uncompressed data into the @c->cur_window buffer. */
- memcpy(c->cur_window, udata, ulen);
- c->cur_window_size = ulen;
-
- /* Initialize the raw range encoder (writing forwards). */
- lzms_range_encoder_raw_init(&c->rc, cdata, clen16);
-
- /* Initialize the output bitstream for Huffman symbols and verbatim bits
- * (writing backwards). */
- lzms_output_bitstream_init(&c->os, cdata, clen16);
-
- /* Calculate the number of offset slots required. */
- num_offset_slots = lzms_get_offset_slot(ulen - 1) + 1;
-
- /* Initialize a Huffman encoder for each alphabet. */
- lzms_init_huffman_encoder(&c->literal_encoder, &c->os,
- LZMS_NUM_LITERAL_SYMS,
- LZMS_LITERAL_CODE_REBUILD_FREQ);
-
- lzms_init_huffman_encoder(&c->lz_offset_encoder, &c->os,
- num_offset_slots,
- LZMS_LZ_OFFSET_CODE_REBUILD_FREQ);
-
- lzms_init_huffman_encoder(&c->length_encoder, &c->os,
- LZMS_NUM_LENGTH_SYMS,
- LZMS_LENGTH_CODE_REBUILD_FREQ);
-
- lzms_init_huffman_encoder(&c->delta_offset_encoder, &c->os,
- num_offset_slots,
- LZMS_DELTA_OFFSET_CODE_REBUILD_FREQ);
-
- lzms_init_huffman_encoder(&c->delta_power_encoder, &c->os,
- 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(&c->main_range_encoder,
- &c->rc, LZMS_NUM_MAIN_STATES);
-
- lzms_init_range_encoder(&c->match_range_encoder,
- &c->rc, LZMS_NUM_MATCH_STATES);
-
- lzms_init_range_encoder(&c->lz_match_range_encoder,
- &c->rc, LZMS_NUM_LZ_MATCH_STATES);
-
- for (unsigned i = 0; i < ARRAY_LEN(c->lz_repeat_match_range_encoders); i++)
- lzms_init_range_encoder(&c->lz_repeat_match_range_encoders[i],
- &c->rc, LZMS_NUM_LZ_REPEAT_MATCH_STATES);
-
- lzms_init_range_encoder(&c->delta_match_range_encoder,
- &c->rc, LZMS_NUM_DELTA_MATCH_STATES);
-
- for (unsigned i = 0; i < ARRAY_LEN(c->delta_repeat_match_range_encoders); i++)
- lzms_init_range_encoder(&c->delta_repeat_match_range_encoders[i],
- &c->rc, LZMS_NUM_DELTA_REPEAT_MATCH_STATES);
-
- /* Set initial length costs for lengths < LZMS_NUM_FAST_LENGTHS. */
- lzms_update_fast_length_costs(c);
-}
-
-/* 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 *c, u8 *cdata, size_t csize_avail)
-{
- size_t num_forwards_bytes;
- size_t num_backwards_bytes;
-
- /* 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(&c->os))
- return 0;
-
- if (!lzms_range_encoder_raw_flush(&c->rc))
- return 0;
-
- if (c->rc.next > c->os.next)
- 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 backwards bitstream to be
- * adjacent to the data output by the forward bitstream, and calculate
- * the compressed size that this results in. */
- num_forwards_bytes = (u8*)c->rc.next - (u8*)cdata;
- num_backwards_bytes = ((u8*)cdata + csize_avail) - (u8*)c->os.next;
-
- memmove(cdata + num_forwards_bytes, c->os.next, num_backwards_bytes);
-
- return num_forwards_bytes + num_backwards_bytes;
-}
-
-/* Set internal compression parameters for the specified compression level and
- * maximum window size. */
-static void
-lzms_build_params(unsigned int compression_level,
- struct lzms_compressor_params *params)
-{
- /* Allow length 2 matches if the compression level is sufficiently high.
- */
- if (compression_level >= 45)
- params->min_match_length = 2;
- else
- params->min_match_length = 3;
-
- /* Scale nice_match_length and max_search_depth with the compression
- * level. But to allow an optimization on length cost calculations,
- * don't allow nice_match_length to exceed LZMS_NUM_FAST_LENGTH. */
- params->nice_match_length = ((u64)compression_level * 32) / 50;
- if (params->nice_match_length < params->min_match_length)
- params->nice_match_length = params->min_match_length;
- if (params->nice_match_length > LZMS_NUM_FAST_LENGTHS)
- params->nice_match_length = LZMS_NUM_FAST_LENGTHS;
- params->max_search_depth = compression_level;
-
- params->optim_array_length = 1024;
-}
-
-/* Given the internal compression parameters and maximum window size, build the
- * Lempel-Ziv match-finder parameters. */
-static void
-lzms_build_mf_params(const struct lzms_compressor_params *lzms_params,
- u32 max_window_size, struct lz_mf_params *mf_params)
-{
- memset(mf_params, 0, sizeof(*mf_params));
-
- /* Choose an appropriate match-finding algorithm. */
- if (max_window_size <= 2097152)
- mf_params->algorithm = LZ_MF_BINARY_TREES;
- else if (max_window_size <= 33554432)
- mf_params->algorithm = LZ_MF_LCP_INTERVAL_TREE;
- else
- mf_params->algorithm = LZ_MF_LINKED_SUFFIX_ARRAY;
-
- mf_params->max_window_size = max_window_size;
- mf_params->min_match_len = lzms_params->min_match_length;
- mf_params->max_search_depth = lzms_params->max_search_depth;
- mf_params->nice_match_len = lzms_params->nice_match_length;
-}
-
-static void
-lzms_free_compressor(void *_c);
-
-static u64
-lzms_get_needed_memory(size_t max_block_size, unsigned int compression_level)
-{
- struct lzms_compressor_params params;
- struct lz_mf_params mf_params;
- u64 size = 0;
-
- if (max_block_size >= INT32_MAX)
- return 0;
-
- lzms_build_params(compression_level, ¶ms);
- lzms_build_mf_params(¶ms, max_block_size, &mf_params);
-
- size += sizeof(struct lzms_compressor);
-
- /* cur_window */
- size += max_block_size;
-
- /* mf */
- size += lz_mf_get_needed_memory(mf_params.algorithm, max_block_size);
-
- /* matches */
- size += min(params.max_search_depth, params.nice_match_length) *
- sizeof(struct lz_match);
-
- /* optimum */
- size += (params.optim_array_length + params.nice_match_length) *
- sizeof(struct lzms_mc_pos_data);
-
- return size;
-}
-
-static int
-lzms_create_compressor(size_t max_block_size, unsigned int compression_level,
- void **ctx_ret)
-{
- struct lzms_compressor *c;
- struct lzms_compressor_params params;
- struct lz_mf_params mf_params;
-
- if (max_block_size >= INT32_MAX)
- return WIMLIB_ERR_INVALID_PARAM;
-
- lzms_build_params(compression_level, ¶ms);
- lzms_build_mf_params(¶ms, max_block_size, &mf_params);
- if (!lz_mf_params_valid(&mf_params))
- return WIMLIB_ERR_INVALID_PARAM;
-
- c = CALLOC(1, sizeof(struct lzms_compressor));
- if (!c)
- goto oom;
-
- c->params = params;
-
- c->cur_window = MALLOC(max_block_size);
- if (!c->cur_window)
- goto oom;
-
- c->mf = lz_mf_alloc(&mf_params);
- if (!c->mf)
- goto oom;
-
- c->matches = MALLOC(min(params.max_search_depth,
- params.nice_match_length) *
- sizeof(struct lz_match));
- if (!c->matches)
- goto oom;
-
- c->optimum = MALLOC((params.optim_array_length +
- params.nice_match_length) *
- sizeof(struct lzms_mc_pos_data));
- if (!c->optimum)
- goto oom;
- c->optimum_end = &c->optimum[params.optim_array_length];
-
- lzms_init_rc_costs();
-
- lzms_init_fast_slots(c);
-
- *ctx_ret = c;
- return 0;
-
-oom:
- lzms_free_compressor(c);
- return WIMLIB_ERR_NOMEM;
-}
-
-static size_t
-lzms_compress(const void *uncompressed_data, size_t uncompressed_size,
- void *compressed_data, size_t compressed_size_avail, void *_c)
-{
- struct lzms_compressor *c = _c;
-
- /* 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_prepare_compressor(c, uncompressed_data, uncompressed_size,
- compressed_data, compressed_size_avail / 2);
-
- /* Preprocess the uncompressed data. */
- lzms_x86_filter(c->cur_window, c->cur_window_size,
- c->last_target_usages, false);
-
- /* Load the window into the match-finder. */
- lz_mf_load_window(c->mf, c->cur_window, c->cur_window_size);
-
- /* Compute and encode a literal/match sequence that decompresses to the
- * preprocessed data. */
- lzms_near_optimal_parse(c);
-
- /* Return the compressed data size or 0. */
- return lzms_finalize(c, compressed_data, compressed_size_avail);
-}
-
-static void
-lzms_free_compressor(void *_c)
-{
- struct lzms_compressor *c = _c;
-
- if (c) {
- FREE(c->cur_window);
- lz_mf_free(c->mf);
- FREE(c->matches);
- FREE(c->optimum);
- FREE(c);
- }
-}
-
-const struct compressor_ops lzms_compressor_ops = {
- .get_needed_memory = lzms_get_needed_memory,
- .create_compressor = lzms_create_compressor,
- .compress = lzms_compress,
- .free_compressor = lzms_free_compressor,
-};
git://wimlib.net / wimlib / blobdiff