lzma_encoder.c

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//
//  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);
}
 
 
#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;
 
    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;
}