+/* 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);
+ lzms_output_bitstream_put_bits(enc->os,
+ enc->codewords[sym],
+ enc->lens[sym]);
+ ++enc->sym_freqs[sym];
+ 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;
+ }
+}
+
+static void
+lzms_encode_length(struct lzms_huffman_encoder *enc, u32 length)
+{
+ unsigned slot;
+ unsigned num_extra_bits;
+ u32 extra_bits;
+
+ slot = lzms_get_length_slot(length);
+
+ num_extra_bits = lzms_extra_length_bits[slot];
+
+ extra_bits = length - lzms_length_slot_base[slot];
+
+ lzms_huffman_encode_symbol(enc, slot);
+ lzms_output_bitstream_put_bits(enc->os, extra_bits, num_extra_bits);
+}
+
+static void
+lzms_encode_offset(struct lzms_huffman_encoder *enc, u32 offset)
+{
+ unsigned slot;
+ unsigned num_extra_bits;
+ u32 extra_bits;
+
+ slot = lzms_get_position_slot(offset);
+
+ num_extra_bits = lzms_extra_position_bits[slot];
+
+ extra_bits = offset - lzms_position_slot_base[slot];
+
+ 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->lru.lz.upcoming_offset = 0;
+ ctx->lru.delta.upcoming_offset = 0;
+ ctx->lru.delta.upcoming_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;
+ lzms_update_lru_queues(&ctx->lru);
+}
+
+/* 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_DEBUG("Position %u: Encoding LZ match {length=%u, offset=%u}",
+ ctx->cur_window_pos, length, offset);
+
+ LZMS_ASSERT(length <= ctx->window_size - ctx->cur_window_pos);
+ LZMS_ASSERT(offset <= ctx->cur_window_pos);
+ LZMS_ASSERT(!memcmp(&ctx->window[ctx->cur_window_pos],
+ &ctx->window[ctx->cur_window_pos - offset],
+ length));
+
+ lzms_begin_encode_item(ctx);
+
+ /* 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->lru.lz.recent_offsets[recent_offset_idx])
+ break;
+
+ if (recent_offset_idx == LZMS_NUM_RECENT_OFFSETS) {
+ /* Explicit offset. */
+
+ /* LZ match bit: 0 = explicit offset, not a recent offset. */
+ lzms_range_encode_bit(&ctx->lz_match_range_encoder, 0);
+
+ /* Encode the match offset. */
+ lzms_encode_offset(&ctx->lz_offset_encoder, offset);
+ } else {
+ int i;
+
+ /* Recent offset. */
+
+ /* LZ match bit: 1 = recent 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->lru.lz.recent_offsets[i] = ctx->lru.lz.recent_offsets[i + 1];
+ }
+
+ /* Encode the match length. */
+ lzms_encode_length(&ctx->length_encoder, length);
+
+ /* Save the match offset for later insertion at the front of the LZ
+ * match offset LRU queue. */
+ ctx->lru.lz.upcoming_offset = offset;
+
+ lzms_end_encode_item(ctx, length);
+}
+
+/* Fast heuristic cost evaluation to use in the inner loop of the match-finder.
+ * Unlike lzms_get_lz_match_cost(), which does a true cost evaluation, this
+ * simply prioritize matches based on their offset. */
+static input_idx_t
+lzms_lz_match_cost_fast(input_idx_t length, input_idx_t offset, const void *_lru)
+{
+ const struct lzms_lz_lru_queues *lru = _lru;
+
+ for (input_idx_t i = 0; i < LZMS_NUM_RECENT_OFFSETS; i++)
+ if (offset == lru->recent_offsets[i])
+ return i;
+
+ return offset;
+}
+
+#define LZMS_COST_SHIFT 5
+
+/*#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 >= (1U << 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 bool done = false;
+ static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+
+ if (unlikely(!done)) {
+ pthread_mutex_lock(&mutex);
+ if (!done) {
+ lzms_do_init_rc_costs();
+ done = true;
+ }
+ pthread_mutex_unlock(&mutex);
+ }
+}
+
+/*
+ * Return the cost to range-encode the specified bit when in the specified
+ * state.
+ *
+ * @enc The range encoder to use.
+ * @cur_state Current state, which indicates the probability entry to choose.
+ * Updated by this function.
+ * @bit The bit to encode (0 or 1).
+ */
+static 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 & enc->mask].num_recent_zero_bits;
+
+ *cur_state = (*cur_state << 1) | bit;
+
+ if (bit == 0)
+ prob_correct = prob_zero;
+ else
+ prob_correct = LZMS_PROBABILITY_MAX - prob_zero;
+
+ return lzms_rc_costs[prob_correct];
+}
+
+static u32
+lzms_huffman_symbol_cost(const struct lzms_huffman_encoder *enc, u32 sym)
+{
+ return enc->lens[sym] << LZMS_COST_SHIFT;
+}
+
+static u32
+lzms_offset_cost(const struct lzms_huffman_encoder *enc, u32 offset)
+{
+ u32 slot;
+ u32 num_extra_bits;
+ u32 cost = 0;
+
+ slot = lzms_get_position_slot(offset);
+
+ cost += lzms_huffman_symbol_cost(enc, slot);
+
+ num_extra_bits = lzms_extra_position_bits[slot];
+
+ cost += num_extra_bits << LZMS_COST_SHIFT;
+
+ return cost;
+}
+
+static u32
+lzms_length_cost(const struct lzms_huffman_encoder *enc, u32 length)
+{
+ u32 slot;
+ u32 num_extra_bits;
+ u32 cost = 0;
+
+ slot = lzms_get_length_slot(length);
+
+ cost += lzms_huffman_symbol_cost(enc, slot);
+
+ num_extra_bits = lzms_extra_length_bits[slot];
+
+ cost += num_extra_bits << LZMS_COST_SHIFT;
+
+ return cost;
+}
+
+static u32
+lzms_get_matches(struct lzms_compressor *ctx,
+ const struct lzms_adaptive_state *state,
+ struct raw_match **matches_ret)
+{
+ *matches_ret = ctx->matches;
+ return lz_sarray_get_matches(&ctx->lz_sarray,
+ ctx->matches,
+ lzms_lz_match_cost_fast,
+ &state->lru);
+}
+
+static void
+lzms_skip_bytes(struct lzms_compressor *ctx, input_idx_t n)
+{
+ while (n--)
+ lz_sarray_skip_position(&ctx->lz_sarray);
+}
+
+static u32
+lzms_get_prev_literal_cost(struct lzms_compressor *ctx,
+ struct lzms_adaptive_state *state)
+{
+ u8 literal = ctx->window[lz_sarray_get_pos(&ctx->lz_sarray) - 1];
+ u32 cost = 0;
+
+ state->lru.upcoming_offset = 0;
+ lzms_update_lz_lru_queues(&state->lru);
+
+ cost += lzms_rc_bit_cost(&ctx->main_range_encoder,
+ &state->main_state, 0);
+
+ cost += lzms_huffman_symbol_cost(&ctx->literal_encoder, literal);
+
+ return cost;
+}
+
+static u32
+lzms_get_lz_match_cost(struct lzms_compressor *ctx,
+ struct lzms_adaptive_state *state,
+ input_idx_t length, input_idx_t offset)
+{
+ u32 cost = 0;
+ int recent_offset_idx;
+
+ cost += lzms_rc_bit_cost(&ctx->main_range_encoder,
+ &state->main_state, 1);
+ cost += lzms_rc_bit_cost(&ctx->match_range_encoder,
+ &state->match_state, 0);
+
+ for (recent_offset_idx = 0;
+ recent_offset_idx < LZMS_NUM_RECENT_OFFSETS;
+ recent_offset_idx++)
+ if (offset == state->lru.recent_offsets[recent_offset_idx])
+ break;
+
+ if (recent_offset_idx == LZMS_NUM_RECENT_OFFSETS) {
+ /* Explicit offset. */
+ cost += lzms_rc_bit_cost(&ctx->lz_match_range_encoder,
+ &state->lz_match_state, 0);
+
+ cost += lzms_offset_cost(&ctx->lz_offset_encoder, offset);
+ } else {
+ int i;
+
+ /* Recent offset. */
+ cost += lzms_rc_bit_cost(&ctx->lz_match_range_encoder,
+ &state->lz_match_state, 1);
+
+ for (i = 0; i < recent_offset_idx; i++)
+ cost += lzms_rc_bit_cost(&ctx->lz_repeat_match_range_encoders[i],
+ &state->lz_repeat_match_state[i], 0);
+
+ if (i < LZMS_NUM_RECENT_OFFSETS - 1)
+ cost += lzms_rc_bit_cost(&ctx->lz_repeat_match_range_encoders[i],
+ &state->lz_repeat_match_state[i], 1);
+
+
+ /* Initial update of the LZ match offset LRU queue. */
+ for (; i < LZMS_NUM_RECENT_OFFSETS; i++)
+ state->lru.recent_offsets[i] = state->lru.recent_offsets[i + 1];
+ }
+
+ cost += lzms_length_cost(&ctx->length_encoder, length);
+
+ state->lru.upcoming_offset = offset;
+ lzms_update_lz_lru_queues(&state->lru);
+
+ return cost;
+}
+
+static struct raw_match
+lzms_get_near_optimal_match(struct lzms_compressor *ctx)
+{
+ struct lzms_adaptive_state initial_state;
+
+ initial_state.lru = ctx->lru.lz;
+ initial_state.main_state = ctx->main_range_encoder.state;
+ initial_state.match_state = ctx->match_range_encoder.state;
+ initial_state.lz_match_state = ctx->lz_match_range_encoder.state;
+ for (int i = 0; i < LZMS_NUM_RECENT_OFFSETS - 1; i++)
+ initial_state.lz_repeat_match_state[i] =
+ ctx->lz_repeat_match_range_encoders[i].state;
+ return lz_get_near_optimal_match(&ctx->mc,
+ lzms_get_matches,
+ lzms_skip_bytes,
+ lzms_get_prev_literal_cost,
+ lzms_get_lz_match_cost,
+ ctx,
+ &initial_state);
+}
+
+/*
+ * The main loop for the LZMS compressor.
+ *
+ * Notes:
+ *
+ * - This uses near-optimal LZ parsing backed by a suffix-array match-finder.
+ * More details can be found in the corresponding files (lz_optimal.h,
+ * lz_sarray.{h,c}).
+ *
+ * - This does not output any delta matches. It would take a specialized
+ * algorithm to find them, then more code in lz_optimal.h and here to handle
+ * evaluating and outputting them.
+ *
+ * - 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 (from the
+ * `struct wimlib_lzms_compressor_params') 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_encode(struct lzms_compressor *ctx)
+{
+ struct raw_match match;
+
+ /* Load window into suffix array match-finder. */
+ lz_sarray_load_window(&ctx->lz_sarray, ctx->window, ctx->window_size);
+
+ /* Reset the match-chooser. */
+ lz_match_chooser_begin(&ctx->mc);
+
+ while (ctx->cur_window_pos != ctx->window_size) {
+ match = lzms_get_near_optimal_match(ctx);
+ if (match.len <= 1)
+ lzms_encode_literal(ctx, ctx->window[ctx->cur_window_pos]);
+ else
+ lzms_encode_lz_match(ctx, match.len, match.offset);
+ }
+}
+
+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,
+ 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);
+}
+
+/* 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);
+ 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);
+
+ /* 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,
+ LZMS_NUM_LITERAL_SYMS,
+ LZMS_LITERAL_CODE_REBUILD_FREQ);
+
+ lzms_init_huffman_encoder(&ctx->lz_offset_encoder, &ctx->os,
+ num_position_slots,
+ LZMS_LZ_OFFSET_CODE_REBUILD_FREQ);
+
+ lzms_init_huffman_encoder(&ctx->length_encoder, &ctx->os,
+ LZMS_NUM_LEN_SYMS,
+ LZMS_LENGTH_CODE_REBUILD_FREQ);
+
+ lzms_init_huffman_encoder(&ctx->delta_offset_encoder, &ctx->os,
+ num_position_slots,
+ LZMS_DELTA_OFFSET_CODE_REBUILD_FREQ);
+
+ lzms_init_huffman_encoder(&ctx->delta_power_encoder, &ctx->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(&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 LRU match information. */
+ lzms_init_lru_queues(&ctx->lru);
+}
+
+/* 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 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*)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 % 2 == 0);
+ return compressed_size;
+}
+