debian: Prepare for upload

[xz/debian.git] / src / liblzma / lzma / lzma_encoder.c

///////////////////////////////////////////////////////////////////////////////
//
/// \file       lzma_encoder.c
/// \brief      LZMA encoder
///
//  Authors:    Igor Pavlov
//              Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "lzma2_encoder.h"
#include "lzma_encoder_private.h"
#include "fastpos.h"


/////////////
// Literal //
/////////////

static inline void
literal_matched(lzma_range_encoder *rc, probability *subcoder,
                uint32_t match_byte, uint32_t symbol)
{
        uint32_t offset = 0x100;
        symbol += UINT32_C(1) << 8;

        do {
                match_byte <<= 1;
                const uint32_t match_bit = match_byte & offset;
                const uint32_t subcoder_index
                                = offset + match_bit + (symbol >> 8);
                const uint32_t bit = (symbol >> 7) & 1;
                rc_bit(rc, &subcoder[subcoder_index], bit);

                symbol <<= 1;
                offset &= ~(match_byte ^ symbol);

        } while (symbol < (UINT32_C(1) << 16));
}


static inline void
literal(lzma_lzma1_encoder *coder, lzma_mf *mf, uint32_t position)
{
        // Locate the literal byte to be encoded and the subcoder.
        const uint8_t cur_byte = mf->buffer[
                        mf->read_pos - mf->read_ahead];
        probability *subcoder = literal_subcoder(coder->literal,
                        coder->literal_context_bits, coder->literal_pos_mask,
                        position, mf->buffer[mf->read_pos - mf->read_ahead - 1]);

        if (is_literal_state(coder->state)) {
                // Previous LZMA-symbol was a literal. Encode a normal
                // literal without a match byte.
                rc_bittree(&coder->rc, subcoder, 8, cur_byte);
        } else {
                // Previous LZMA-symbol was a match. Use the last byte of
                // the match as a "match byte". That is, compare the bits
                // of the current literal and the match byte.
                const uint8_t match_byte = mf->buffer[
                                mf->read_pos - coder->reps[0] - 1
                                - mf->read_ahead];
                literal_matched(&coder->rc, subcoder, match_byte, cur_byte);
        }

        update_literal(coder->state);
}


//////////////////
// Match length //
//////////////////

static void
length_update_prices(lzma_length_encoder *lc, const uint32_t pos_state)
{
        const uint32_t table_size = lc->table_size;
        lc->counters[pos_state] = table_size;

        const uint32_t a0 = rc_bit_0_price(lc->choice);
        const uint32_t a1 = rc_bit_1_price(lc->choice);
        const uint32_t b0 = a1 + rc_bit_0_price(lc->choice2);
        const uint32_t b1 = a1 + rc_bit_1_price(lc->choice2);
        uint32_t *const prices = lc->prices[pos_state];

        uint32_t i;
        for (i = 0; i < table_size && i < LEN_LOW_SYMBOLS; ++i)
                prices[i] = a0 + rc_bittree_price(lc->low[pos_state],
                                LEN_LOW_BITS, i);

        for (; i < table_size && i < LEN_LOW_SYMBOLS + LEN_MID_SYMBOLS; ++i)
                prices[i] = b0 + rc_bittree_price(lc->mid[pos_state],
                                LEN_MID_BITS, i - LEN_LOW_SYMBOLS);

        for (; i < table_size; ++i)
                prices[i] = b1 + rc_bittree_price(lc->high, LEN_HIGH_BITS,
                                i - LEN_LOW_SYMBOLS - LEN_MID_SYMBOLS);

        return;
}


static inline void
length(lzma_range_encoder *rc, lzma_length_encoder *lc,
                const uint32_t pos_state, uint32_t len, const bool fast_mode)
{
        assert(len <= MATCH_LEN_MAX);
        len -= MATCH_LEN_MIN;

        if (len < LEN_LOW_SYMBOLS) {
                rc_bit(rc, &lc->choice, 0);
                rc_bittree(rc, lc->low[pos_state], LEN_LOW_BITS, len);
        } else {
                rc_bit(rc, &lc->choice, 1);
                len -= LEN_LOW_SYMBOLS;

                if (len < LEN_MID_SYMBOLS) {
                        rc_bit(rc, &lc->choice2, 0);
                        rc_bittree(rc, lc->mid[pos_state], LEN_MID_BITS, len);
                } else {
                        rc_bit(rc, &lc->choice2, 1);
                        len -= LEN_MID_SYMBOLS;
                        rc_bittree(rc, lc->high, LEN_HIGH_BITS, len);
                }
        }

        // Only getoptimum uses the prices so don't update the table when
        // in fast mode.
        if (!fast_mode)
                if (--lc->counters[pos_state] == 0)
                        length_update_prices(lc, pos_state);
}


///////////
// Match //
///////////

static inline void
match(lzma_lzma1_encoder *coder, const uint32_t pos_state,
                const uint32_t distance, const uint32_t len)
{
        update_match(coder->state);

        length(&coder->rc, &coder->match_len_encoder, pos_state, len,
                        coder->fast_mode);

        const uint32_t dist_slot = get_dist_slot(distance);
        const uint32_t dist_state = get_dist_state(len);
        rc_bittree(&coder->rc, coder->dist_slot[dist_state],
                        DIST_SLOT_BITS, dist_slot);

        if (dist_slot >= DIST_MODEL_START) {
                const uint32_t footer_bits = (dist_slot >> 1) - 1;
                const uint32_t base = (2 | (dist_slot & 1)) << footer_bits;
                const uint32_t dist_reduced = distance - base;

                if (dist_slot < DIST_MODEL_END) {
                        // Careful here: base - dist_slot - 1 can be -1, but
                        // rc_bittree_reverse starts at probs[1], not probs[0].
                        rc_bittree_reverse(&coder->rc,
                                coder->dist_special + base - dist_slot - 1,
                                footer_bits, dist_reduced);
                } else {
                        rc_direct(&coder->rc, dist_reduced >> ALIGN_BITS,
                                        footer_bits - ALIGN_BITS);
                        rc_bittree_reverse(
                                        &coder->rc, coder->dist_align,
                                        ALIGN_BITS, dist_reduced & ALIGN_MASK);
                        ++coder->align_price_count;
                }
        }

        coder->reps[3] = coder->reps[2];
        coder->reps[2] = coder->reps[1];
        coder->reps[1] = coder->reps[0];
        coder->reps[0] = distance;
        ++coder->match_price_count;
}


////////////////////
// Repeated match //
////////////////////

static inline void
rep_match(lzma_lzma1_encoder *coder, const uint32_t pos_state,
                const uint32_t rep, const uint32_t len)
{
        if (rep == 0) {
                rc_bit(&coder->rc, &coder->is_rep0[coder->state], 0);
                rc_bit(&coder->rc,
                                &coder->is_rep0_long[coder->state][pos_state],
                                len != 1);
        } else {
                const uint32_t distance = coder->reps[rep];
                rc_bit(&coder->rc, &coder->is_rep0[coder->state], 1);

                if (rep == 1) {
                        rc_bit(&coder->rc, &coder->is_rep1[coder->state], 0);
                } else {
                        rc_bit(&coder->rc, &coder->is_rep1[coder->state], 1);
                        rc_bit(&coder->rc, &coder->is_rep2[coder->state],
                                        rep - 2);

                        if (rep == 3)
                                coder->reps[3] = coder->reps[2];

                        coder->reps[2] = coder->reps[1];
                }

                coder->reps[1] = coder->reps[0];
                coder->reps[0] = distance;
        }

        if (len == 1) {
                update_short_rep(coder->state);
        } else {
                length(&coder->rc, &coder->rep_len_encoder, pos_state, len,
                                coder->fast_mode);
                update_long_rep(coder->state);
        }
}


//////////
// Main //
//////////

static void
encode_symbol(lzma_lzma1_encoder *coder, lzma_mf *mf,
                uint32_t back, uint32_t len, uint32_t position)
{
        const uint32_t pos_state = position & coder->pos_mask;

        if (back == UINT32_MAX) {
                // Literal i.e. eight-bit byte
                assert(len == 1);
                rc_bit(&coder->rc,
                                &coder->is_match[coder->state][pos_state], 0);
                literal(coder, mf, position);
        } else {
                // Some type of match
                rc_bit(&coder->rc,
                        &coder->is_match[coder->state][pos_state], 1);

                if (back < REPS) {
                        // It's a repeated match i.e. the same distance
                        // has been used earlier.
                        rc_bit(&coder->rc, &coder->is_rep[coder->state], 1);
                        rep_match(coder, pos_state, back, len);
                } else {
                        // Normal match
                        rc_bit(&coder->rc, &coder->is_rep[coder->state], 0);
                        match(coder, pos_state, back - REPS, len);
                }
        }

        assert(mf->read_ahead >= len);
        mf->read_ahead -= len;
}


static bool
encode_init(lzma_lzma1_encoder *coder, lzma_mf *mf)
{
        assert(mf_position(mf) == 0);

        if (mf->read_pos == mf->read_limit) {
                if (mf->action == LZMA_RUN)
                        return false; // We cannot do anything.

                // We are finishing (we cannot get here when flushing).
                assert(mf->write_pos == mf->read_pos);
                assert(mf->action == LZMA_FINISH);
        } else {
                // Do the actual initialization. The first LZMA symbol must
                // always be a literal.
                mf_skip(mf, 1);
                mf->read_ahead = 0;
                rc_bit(&coder->rc, &coder->is_match[0][0], 0);
                rc_bittree(&coder->rc, coder->literal[0], 8, mf->buffer[0]);
        }

        // Initialization is done (except if empty file).
        coder->is_initialized = true;

        return true;
}


static void
encode_eopm(lzma_lzma1_encoder *coder, uint32_t position)
{
        const uint32_t pos_state = position & coder->pos_mask;
        rc_bit(&coder->rc, &coder->is_match[coder->state][pos_state], 1);
        rc_bit(&coder->rc, &coder->is_rep[coder->state], 0);
        match(coder, pos_state, UINT32_MAX, MATCH_LEN_MIN);
}


/// Number of bytes that a single encoding loop in lzma_lzma_encode() can
/// consume from the dictionary. This limit comes from lzma_lzma_optimum()
/// and may need to be updated if that function is significantly modified.
#define LOOP_INPUT_MAX (OPTS + 1)


extern lzma_ret
lzma_lzma_encode(lzma_lzma1_encoder *restrict coder, lzma_mf *restrict mf,
                uint8_t *restrict out, size_t *restrict out_pos,
                size_t out_size, uint32_t limit)
{
        // Initialize the stream if no data has been encoded yet.
        if (!coder->is_initialized && !encode_init(coder, mf))
                return LZMA_OK;

        // Get the lowest bits of the uncompressed offset from the LZ layer.
        uint32_t position = mf_position(mf);

        while (true) {
                // Encode pending bits, if any. Calling this before encoding
                // the next symbol is needed only with plain LZMA, since
                // LZMA2 always provides big enough buffer to flush
                // everything out from the range encoder. For the same reason,
                // rc_encode() never returns true when this function is used
                // as part of LZMA2 encoder.
                if (rc_encode(&coder->rc, out, out_pos, out_size)) {
                        assert(limit == UINT32_MAX);
                        return LZMA_OK;
                }

                // With LZMA2 we need to take care that compressed size of
                // a chunk doesn't get too big.
                // FIXME? Check if this could be improved.
                if (limit != UINT32_MAX
                                && (mf->read_pos - mf->read_ahead >= limit
                                        || *out_pos + rc_pending(&coder->rc)
                                                >= LZMA2_CHUNK_MAX
                                                        - LOOP_INPUT_MAX))
                        break;

                // Check that there is some input to process.
                if (mf->read_pos >= mf->read_limit) {
                        if (mf->action == LZMA_RUN)
                                return LZMA_OK;

                        if (mf->read_ahead == 0)
                                break;
                }

                // Get optimal match (repeat position and length).
                // Value ranges for pos:
                //   - [0, REPS): repeated match
                //   - [REPS, UINT32_MAX):
                //     match at (pos - REPS)
                //   - UINT32_MAX: not a match but a literal
                // Value ranges for len:
                //   - [MATCH_LEN_MIN, MATCH_LEN_MAX]
                uint32_t len;
                uint32_t back;

                if (coder->fast_mode)
                        lzma_lzma_optimum_fast(coder, mf, &back, &len);
                else
                        lzma_lzma_optimum_normal(
                                        coder, mf, &back, &len, position);

                encode_symbol(coder, mf, back, len, position);

                position += len;
        }

        if (!coder->is_flushed) {
                coder->is_flushed = true;

                // We don't support encoding plain LZMA streams without EOPM,
                // and LZMA2 doesn't use EOPM at LZMA level.
                if (limit == UINT32_MAX)
                        encode_eopm(coder, position);

                // Flush the remaining bytes from the range encoder.
                rc_flush(&coder->rc);

                // Copy the remaining bytes to the output buffer. If there
                // isn't enough output space, we will copy out the remaining
                // bytes on the next call to this function by using
                // the rc_encode() call in the encoding loop above.
                if (rc_encode(&coder->rc, out, out_pos, out_size)) {
                        assert(limit == UINT32_MAX);
                        return LZMA_OK;
                }
        }

        // Make it ready for the next LZMA2 chunk.
        coder->is_flushed = false;

        return LZMA_STREAM_END;
}


static lzma_ret
lzma_encode(void *coder, lzma_mf *restrict mf,
                uint8_t *restrict out, size_t *restrict out_pos,
                size_t out_size)
{
        // Plain LZMA has no support for sync-flushing.
        if (unlikely(mf->action == LZMA_SYNC_FLUSH))
                return LZMA_OPTIONS_ERROR;

        return lzma_lzma_encode(coder, mf, out, out_pos, out_size, UINT32_MAX);
}


////////////////////
// Initialization //
////////////////////

static bool
is_options_valid(const lzma_options_lzma *options)
{
        // Validate some of the options. LZ encoder validates nice_len too
        // but we need a valid value here earlier.
        return is_lclppb_valid(options)
                        && options->nice_len >= MATCH_LEN_MIN
                        && options->nice_len <= MATCH_LEN_MAX
                        && (options->mode == LZMA_MODE_FAST
                                || options->mode == LZMA_MODE_NORMAL);
}


static void
set_lz_options(lzma_lz_options *lz_options, const lzma_options_lzma *options)
{
        // LZ encoder initialization does the validation for these so we
        // don't need to validate here.
        lz_options->before_size = OPTS;
        lz_options->dict_size = options->dict_size;
        lz_options->after_size = LOOP_INPUT_MAX;
        lz_options->match_len_max = MATCH_LEN_MAX;
        lz_options->nice_len = options->nice_len;
        lz_options->match_finder = options->mf;
        lz_options->depth = options->depth;
        lz_options->preset_dict = options->preset_dict;
        lz_options->preset_dict_size = options->preset_dict_size;
        return;
}


static void
length_encoder_reset(lzma_length_encoder *lencoder,
                const uint32_t num_pos_states, const bool fast_mode)
{
        bit_reset(lencoder->choice);
        bit_reset(lencoder->choice2);

        for (size_t pos_state = 0; pos_state < num_pos_states; ++pos_state) {
                bittree_reset(lencoder->low[pos_state], LEN_LOW_BITS);
                bittree_reset(lencoder->mid[pos_state], LEN_MID_BITS);
        }

        bittree_reset(lencoder->high, LEN_HIGH_BITS);

        if (!fast_mode)
                for (uint32_t pos_state = 0; pos_state < num_pos_states;
                                ++pos_state)
                        length_update_prices(lencoder, pos_state);

        return;
}


extern lzma_ret
lzma_lzma_encoder_reset(lzma_lzma1_encoder *coder,
                const lzma_options_lzma *options)
{
        if (!is_options_valid(options))
                return LZMA_OPTIONS_ERROR;

        coder->pos_mask = (1U << options->pb) - 1;
        coder->literal_context_bits = options->lc;
        coder->literal_pos_mask = (1U << options->lp) - 1;

        // Range coder
        rc_reset(&coder->rc);

        // State
        coder->state = STATE_LIT_LIT;
        for (size_t i = 0; i < REPS; ++i)
                coder->reps[i] = 0;

        literal_init(coder->literal, options->lc, options->lp);

        // Bit encoders
        for (size_t i = 0; i < STATES; ++i) {
                for (size_t j = 0; j <= coder->pos_mask; ++j) {
                        bit_reset(coder->is_match[i][j]);
                        bit_reset(coder->is_rep0_long[i][j]);
                }

                bit_reset(coder->is_rep[i]);
                bit_reset(coder->is_rep0[i]);
                bit_reset(coder->is_rep1[i]);
                bit_reset(coder->is_rep2[i]);
        }

        for (size_t i = 0; i < FULL_DISTANCES - DIST_MODEL_END; ++i)
                bit_reset(coder->dist_special[i]);

        // Bit tree encoders
        for (size_t i = 0; i < DIST_STATES; ++i)
                bittree_reset(coder->dist_slot[i], DIST_SLOT_BITS);

        bittree_reset(coder->dist_align, ALIGN_BITS);

        // Length encoders
        length_encoder_reset(&coder->match_len_encoder,
                        1U << options->pb, coder->fast_mode);

        length_encoder_reset(&coder->rep_len_encoder,
                        1U << options->pb, coder->fast_mode);

        // Price counts are incremented every time appropriate probabilities
        // are changed. price counts are set to zero when the price tables
        // are updated, which is done when the appropriate price counts have
        // big enough value, and lzma_mf.read_ahead == 0 which happens at
        // least every OPTS (a few thousand) possible price count increments.
        //
        // By resetting price counts to UINT32_MAX / 2, we make sure that the
        // price tables will be initialized before they will be used (since
        // the value is definitely big enough), and that it is OK to increment
        // price counts without risk of integer overflow (since UINT32_MAX / 2
        // is small enough). The current code doesn't increment price counts
        // before initializing price tables, but it maybe done in future if
        // we add support for saving the state between LZMA2 chunks.
        coder->match_price_count = UINT32_MAX / 2;
        coder->align_price_count = UINT32_MAX / 2;

        coder->opts_end_index = 0;
        coder->opts_current_index = 0;

        return LZMA_OK;
}


extern lzma_ret
lzma_lzma_encoder_create(void **coder_ptr,
                const lzma_allocator *allocator,
                const lzma_options_lzma *options, lzma_lz_options *lz_options)
{
        // Allocate lzma_lzma1_encoder if it wasn't already allocated.
        if (*coder_ptr == NULL) {
                *coder_ptr = lzma_alloc(sizeof(lzma_lzma1_encoder), allocator);
                if (*coder_ptr == NULL)
                        return LZMA_MEM_ERROR;
        }

        lzma_lzma1_encoder *coder = *coder_ptr;

        // Set compression mode. We haven't validates the options yet,
        // but it's OK here, since nothing bad happens with invalid
        // options in the code below, and they will get rejected by
        // lzma_lzma_encoder_reset() call at the end of this function.
        switch (options->mode) {
                case LZMA_MODE_FAST:
                        coder->fast_mode = true;
                        break;

                case LZMA_MODE_NORMAL: {
                        coder->fast_mode = false;

                        // Set dist_table_size.
                        // Round the dictionary size up to next 2^n.
                        uint32_t log_size = 0;
                        while ((UINT32_C(1) << log_size) < options->dict_size)
                                ++log_size;

                        coder->dist_table_size = log_size * 2;

                        // Length encoders' price table size
                        coder->match_len_encoder.table_size
                                = options->nice_len + 1 - MATCH_LEN_MIN;
                        coder->rep_len_encoder.table_size
                                = options->nice_len + 1 - MATCH_LEN_MIN;
                        break;
                }

                default:
                        return LZMA_OPTIONS_ERROR;
        }

        // We don't need to write the first byte as literal if there is
        // a non-empty preset dictionary. encode_init() wouldn't even work
        // if there is a non-empty preset dictionary, because encode_init()
        // assumes that position is zero and previous byte is also zero.
        coder->is_initialized = options->preset_dict != NULL
                        && options->preset_dict_size > 0;
        coder->is_flushed = false;

        set_lz_options(lz_options, options);

        return lzma_lzma_encoder_reset(coder, options);
}


static lzma_ret
lzma_encoder_init(lzma_lz_encoder *lz, const lzma_allocator *allocator,
                const void *options, lzma_lz_options *lz_options)
{
        lz->code = &lzma_encode;
        return lzma_lzma_encoder_create(
                        &lz->coder, allocator, options, lz_options);
}


extern lzma_ret
lzma_lzma_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
                const lzma_filter_info *filters)
{
        return lzma_lz_encoder_init(
                        next, allocator, filters, &lzma_encoder_init);
}


extern uint64_t
lzma_lzma_encoder_memusage(const void *options)
{
        if (!is_options_valid(options))
                return UINT64_MAX;

        lzma_lz_options lz_options;
        set_lz_options(&lz_options, options);

        const uint64_t lz_memusage = lzma_lz_encoder_memusage(&lz_options);
        if (lz_memusage == UINT64_MAX)
                return UINT64_MAX;

        return (uint64_t)(sizeof(lzma_lzma1_encoder)) + lz_memusage;
}


extern bool
lzma_lzma_lclppb_encode(const lzma_options_lzma *options, uint8_t *byte)
{
        if (!is_lclppb_valid(options))
                return true;

        *byte = (options->pb * 5 + options->lp) * 9 + options->lc;
        assert(*byte <= (4 * 5 + 4) * 9 + 8);

        return false;
}


#ifdef HAVE_ENCODER_LZMA1
extern lzma_ret
lzma_lzma_props_encode(const void *options, uint8_t *out)
{
        const lzma_options_lzma *const opt = options;

        if (lzma_lzma_lclppb_encode(opt, out))
                return LZMA_PROG_ERROR;

        unaligned_write32le(out + 1, opt->dict_size);

        return LZMA_OK;
}
#endif


extern LZMA_API(lzma_bool)
lzma_mode_is_supported(lzma_mode mode)
{
        return mode == LZMA_MODE_FAST || mode == LZMA_MODE_NORMAL;
}