The R Project SVN R

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

#include "lz_decoder.h"
#include "lzma_common.h"
#include "lzma_decoder.h"
#include "range_decoder.h"


#ifdef HAVE_SMALL

// Macros for (somewhat) size-optimized code.
#define seq_4(seq) seq

#define seq_6(seq) seq

#define seq_8(seq) seq

#define seq_len(seq) \
    seq ## _CHOICE, \
    seq ## _CHOICE2, \
    seq ## _BITTREE

#define len_decode(target, ld, pos_state, seq) \
do { \
case seq ## _CHOICE: \
    rc_if_0(ld.choice, seq ## _CHOICE) { \
        rc_update_0(ld.choice); \
        probs = ld.low[pos_state];\
        limit = LEN_LOW_SYMBOLS; \
        target = MATCH_LEN_MIN; \
    } else { \
        rc_update_1(ld.choice); \
case seq ## _CHOICE2: \
        rc_if_0(ld.choice2, seq ## _CHOICE2) { \
            rc_update_0(ld.choice2); \
            probs = ld.mid[pos_state]; \
            limit = LEN_MID_SYMBOLS; \
            target = MATCH_LEN_MIN + LEN_LOW_SYMBOLS; \
        } else { \
            rc_update_1(ld.choice2); \
            probs = ld.high; \
            limit = LEN_HIGH_SYMBOLS; \
            target = MATCH_LEN_MIN + LEN_LOW_SYMBOLS \
                    + LEN_MID_SYMBOLS; \
        } \
    } \
    symbol = 1; \
case seq ## _BITTREE: \
    do { \
        rc_bit(probs[symbol], , , seq ## _BITTREE); \
    } while (symbol < limit); \
    target += symbol - limit; \
} while (0)

#else // HAVE_SMALL

// Unrolled versions
#define seq_4(seq) \
    seq ## 0, \
    seq ## 1, \
    seq ## 2, \
    seq ## 3

#define seq_6(seq) \
    seq ## 0, \
    seq ## 1, \
    seq ## 2, \
    seq ## 3, \
    seq ## 4, \
    seq ## 5

#define seq_8(seq) \
    seq ## 0, \
    seq ## 1, \
    seq ## 2, \
    seq ## 3, \
    seq ## 4, \
    seq ## 5, \
    seq ## 6, \
    seq ## 7

#define seq_len(seq) \
    seq ## _CHOICE, \
    seq ## _LOW0, \
    seq ## _LOW1, \
    seq ## _LOW2, \
    seq ## _CHOICE2, \
    seq ## _MID0, \
    seq ## _MID1, \
    seq ## _MID2, \
    seq ## _HIGH0, \
    seq ## _HIGH1, \
    seq ## _HIGH2, \
    seq ## _HIGH3, \
    seq ## _HIGH4, \
    seq ## _HIGH5, \
    seq ## _HIGH6, \
    seq ## _HIGH7

#define len_decode(target, ld, pos_state, seq) \
do { \
    symbol = 1; \
case seq ## _CHOICE: \
    rc_if_0(ld.choice, seq ## _CHOICE) { \
        rc_update_0(ld.choice); \
        rc_bit_case(ld.low[pos_state][symbol], , , seq ## _LOW0); \
        rc_bit_case(ld.low[pos_state][symbol], , , seq ## _LOW1); \
        rc_bit_case(ld.low[pos_state][symbol], , , seq ## _LOW2); \
        target = symbol - LEN_LOW_SYMBOLS + MATCH_LEN_MIN; \
    } else { \
        rc_update_1(ld.choice); \
case seq ## _CHOICE2: \
        rc_if_0(ld.choice2, seq ## _CHOICE2) { \
            rc_update_0(ld.choice2); \
            rc_bit_case(ld.mid[pos_state][symbol], , , \
                    seq ## _MID0); \
            rc_bit_case(ld.mid[pos_state][symbol], , , \
                    seq ## _MID1); \
            rc_bit_case(ld.mid[pos_state][symbol], , , \
                    seq ## _MID2); \
            target = symbol - LEN_MID_SYMBOLS \
                    + MATCH_LEN_MIN + LEN_LOW_SYMBOLS; \
        } else { \
            rc_update_1(ld.choice2); \
            rc_bit_case(ld.high[symbol], , , seq ## _HIGH0); \
            rc_bit_case(ld.high[symbol], , , seq ## _HIGH1); \
            rc_bit_case(ld.high[symbol], , , seq ## _HIGH2); \
            rc_bit_case(ld.high[symbol], , , seq ## _HIGH3); \
            rc_bit_case(ld.high[symbol], , , seq ## _HIGH4); \
            rc_bit_case(ld.high[symbol], , , seq ## _HIGH5); \
            rc_bit_case(ld.high[symbol], , , seq ## _HIGH6); \
            rc_bit_case(ld.high[symbol], , , seq ## _HIGH7); \
            target = symbol - LEN_HIGH_SYMBOLS \
                    + MATCH_LEN_MIN \
                    + LEN_LOW_SYMBOLS + LEN_MID_SYMBOLS; \
        } \
    } \
} while (0)

#endif // HAVE_SMALL


/// Length decoder probabilities; see comments in lzma_common.h.
typedef struct {
    probability choice;
    probability choice2;
    probability low[POS_STATES_MAX][LEN_LOW_SYMBOLS];
    probability mid[POS_STATES_MAX][LEN_MID_SYMBOLS];
    probability high[LEN_HIGH_SYMBOLS];
} lzma_length_decoder;


struct lzma_coder_s {
    ///////////////////
    // Probabilities //
    ///////////////////

    /// Literals; see comments in lzma_common.h.
    probability literal[LITERAL_CODERS_MAX][LITERAL_CODER_SIZE];

    /// If 1, it's a match. Otherwise it's a single 8-bit literal.
    probability is_match[STATES][POS_STATES_MAX];

    /// If 1, it's a repeated match. The distance is one of rep0 .. rep3.
    probability is_rep[STATES];

    /// If 0, distance of a repeated match is rep0.
    /// Otherwise check is_rep1.
    probability is_rep0[STATES];

    /// If 0, distance of a repeated match is rep1.
    /// Otherwise check is_rep2.
    probability is_rep1[STATES];

    /// If 0, distance of a repeated match is rep2. Otherwise it is rep3.
    probability is_rep2[STATES];

    /// If 1, the repeated match has length of one byte. Otherwise
    /// the length is decoded from rep_len_decoder.
    probability is_rep0_long[STATES][POS_STATES_MAX];

    /// Probability tree for the highest two bits of the match distance.
    /// There is a separate probability tree for match lengths of
    /// 2 (i.e. MATCH_LEN_MIN), 3, 4, and [5, 273].
    probability pos_slot[LEN_TO_POS_STATES][POS_SLOTS];

    /// Probility trees for additional bits for match distance when the
    /// distance is in the range [4, 127].
    probability pos_special[FULL_DISTANCES - END_POS_MODEL_INDEX];

    /// Probability tree for the lowest four bits of a match distance
    /// that is equal to or greater than 128.
    probability pos_align[ALIGN_TABLE_SIZE];

    /// Length of a normal match
    lzma_length_decoder match_len_decoder;

    /// Length of a repeated match
    lzma_length_decoder rep_len_decoder;

    ///////////////////
    // Decoder state //
    ///////////////////

    // Range coder
    lzma_range_decoder rc;

    // Types of the most recently seen LZMA symbols
    lzma_lzma_state state;

    uint32_t rep0;      ///< Distance of the latest match
    uint32_t rep1;      ///< Distance of second latest match
    uint32_t rep2;      ///< Distance of third latest match
    uint32_t rep3;      ///< Distance of fourth latest match

    uint32_t pos_mask; // (1U << pb) - 1
    uint32_t literal_context_bits;
    uint32_t literal_pos_mask;

    /// Uncompressed size as bytes, or LZMA_VLI_UNKNOWN if end of
    /// payload marker is expected.
    lzma_vli uncompressed_size;

    ////////////////////////////////
    // State of incomplete symbol //
    ////////////////////////////////

    /// Position where to continue the decoder loop
    enum {
        SEQ_NORMALIZE,
        SEQ_IS_MATCH,
        seq_8(SEQ_LITERAL),
        seq_8(SEQ_LITERAL_MATCHED),
        SEQ_LITERAL_WRITE,
        SEQ_IS_REP,
        seq_len(SEQ_MATCH_LEN),
        seq_6(SEQ_POS_SLOT),
        SEQ_POS_MODEL,
        SEQ_DIRECT,
        seq_4(SEQ_ALIGN),
        SEQ_EOPM,
        SEQ_IS_REP0,
        SEQ_SHORTREP,
        SEQ_IS_REP0_LONG,
        SEQ_IS_REP1,
        SEQ_IS_REP2,
        seq_len(SEQ_REP_LEN),
        SEQ_COPY,
    } sequence;

    /// Base of the current probability tree
    probability *probs;

    /// Symbol being decoded. This is also used as an index variable in
    /// bittree decoders: probs[symbol]
    uint32_t symbol;

    /// Used as a loop termination condition on bittree decoders and
    /// direct bits decoder.
    uint32_t limit;

    /// Matched literal decoder: 0x100 or 0 to help avoiding branches.
    /// Bittree reverse decoders: Offset of the next bit: 1 << offset
    uint32_t offset;

    /// If decoding a literal: match byte.
    /// If decoding a match: length of the match.
    uint32_t len;
};


static lzma_ret
lzma_decode(lzma_coder *restrict coder, lzma_dict *restrict dictptr,
        const uint8_t *restrict in,
        size_t *restrict in_pos, size_t in_size)
{
    ////////////////////
    // Initialization //
    ////////////////////

    if (!rc_read_init(&coder->rc, in, in_pos, in_size))
        return LZMA_OK;

    ///////////////
    // Variables //
    ///////////////

    // Making local copies of often-used variables improves both
    // speed and readability.

    lzma_dict dict = *dictptr;

    const size_t dict_start = dict.pos;

    // Range decoder
    rc_to_local(coder->rc, *in_pos);

    // State
    uint32_t state = coder->state;
    uint32_t rep0 = coder->rep0;
    uint32_t rep1 = coder->rep1;
    uint32_t rep2 = coder->rep2;
    uint32_t rep3 = coder->rep3;

    const uint32_t pos_mask = coder->pos_mask;

    // These variables are actually needed only if we last time ran
    // out of input in the middle of the decoder loop.
    probability *probs = coder->probs;
    uint32_t symbol = coder->symbol;
    uint32_t limit = coder->limit;
    uint32_t offset = coder->offset;
    uint32_t len = coder->len;

    const uint32_t literal_pos_mask = coder->literal_pos_mask;
    const uint32_t literal_context_bits = coder->literal_context_bits;

    // Temporary variables
    uint32_t pos_state = dict.pos & pos_mask;

    lzma_ret ret = LZMA_OK;

    // If uncompressed size is known, there must be no end of payload
    // marker.
    const bool no_eopm = coder->uncompressed_size
            != LZMA_VLI_UNKNOWN;
    if (no_eopm && coder->uncompressed_size < dict.limit - dict.pos)
        dict.limit = dict.pos + (size_t)(coder->uncompressed_size);

    // The main decoder loop. The "switch" is used to restart the decoder at
    // correct location. Once restarted, the "switch" is no longer used.
    switch (coder->sequence)
    while (true) {
        // Calculate new pos_state. This is skipped on the first loop
        // since we already calculated it when setting up the local
        // variables.
        pos_state = dict.pos & pos_mask;

    case SEQ_NORMALIZE:
    case SEQ_IS_MATCH:
        if (unlikely(no_eopm && dict.pos == dict.limit))
            break;

        rc_if_0(coder->is_match[state][pos_state], SEQ_IS_MATCH) {
            rc_update_0(coder->is_match[state][pos_state]);

            // It's a literal i.e. a single 8-bit byte.

            probs = literal_subcoder(coder->literal,
                    literal_context_bits, literal_pos_mask,
                    dict.pos, dict_get(&dict, 0));
            symbol = 1;

            if (is_literal_state(state)) {
                // Decode literal without match byte.
#ifdef HAVE_SMALL
    case SEQ_LITERAL:
                do {
                    rc_bit(probs[symbol], , , SEQ_LITERAL);
                } while (symbol < (1 << 8));
#else
                rc_bit_case(probs[symbol], , , SEQ_LITERAL0);
                rc_bit_case(probs[symbol], , , SEQ_LITERAL1);
                rc_bit_case(probs[symbol], , , SEQ_LITERAL2);
                rc_bit_case(probs[symbol], , , SEQ_LITERAL3);
                rc_bit_case(probs[symbol], , , SEQ_LITERAL4);
                rc_bit_case(probs[symbol], , , SEQ_LITERAL5);
                rc_bit_case(probs[symbol], , , SEQ_LITERAL6);
                rc_bit_case(probs[symbol], , , SEQ_LITERAL7);
#endif
            } else {
                // Decode literal with match byte.
                //
                // We store the byte we compare against
                // ("match byte") to "len" to minimize the
                // number of variables we need to store
                // between decoder calls.
                len = dict_get(&dict, rep0) << 1;

                // The usage of "offset" allows omitting some
                // branches, which should give tiny speed
                // improvement on some CPUs. "offset" gets
                // set to zero if match_bit didn't match.
                offset = 0x100;

#ifdef HAVE_SMALL
    case SEQ_LITERAL_MATCHED:
                do {
                    const uint32_t match_bit
                            = len & offset;
                    const uint32_t subcoder_index
                            = offset + match_bit
                            + symbol;

                    rc_bit(probs[subcoder_index],
                            offset &= ~match_bit,
                            offset &= match_bit,
                            SEQ_LITERAL_MATCHED);

                    // It seems to be faster to do this
                    // here instead of putting it to the
                    // beginning of the loop and then
                    // putting the "case" in the middle
                    // of the loop.
                    len <<= 1;

                } while (symbol < (1 << 8));
#else
                // Unroll the loop.
                uint32_t match_bit;
                uint32_t subcoder_index;

#   define d(seq) \
        case seq: \
            match_bit = len & offset; \
            subcoder_index = offset + match_bit + symbol; \
            rc_bit(probs[subcoder_index], \
                    offset &= ~match_bit, \
                    offset &= match_bit, \
                    seq)

                d(SEQ_LITERAL_MATCHED0);
                len <<= 1;
                d(SEQ_LITERAL_MATCHED1);
                len <<= 1;
                d(SEQ_LITERAL_MATCHED2);
                len <<= 1;
                d(SEQ_LITERAL_MATCHED3);
                len <<= 1;
                d(SEQ_LITERAL_MATCHED4);
                len <<= 1;
                d(SEQ_LITERAL_MATCHED5);
                len <<= 1;
                d(SEQ_LITERAL_MATCHED6);
                len <<= 1;
                d(SEQ_LITERAL_MATCHED7);
#   undef d
#endif
            }

            //update_literal(state);
            // Use a lookup table to update to literal state,
            // since compared to other state updates, this would
            // need two branches.
            static const lzma_lzma_state next_state[] = {
                STATE_LIT_LIT,
                STATE_LIT_LIT,
                STATE_LIT_LIT,
                STATE_LIT_LIT,
                STATE_MATCH_LIT_LIT,
                STATE_REP_LIT_LIT,
                STATE_SHORTREP_LIT_LIT,
                STATE_MATCH_LIT,
                STATE_REP_LIT,
                STATE_SHORTREP_LIT,
                STATE_MATCH_LIT,
                STATE_REP_LIT
            };
            state = next_state[state];

    case SEQ_LITERAL_WRITE:
            if (unlikely(dict_put(&dict, symbol))) {
                coder->sequence = SEQ_LITERAL_WRITE;
                goto out;
            }

            continue;
        }

        // Instead of a new byte we are going to get a byte range
        // (distance and length) which will be repeated from our
        // output history.

        rc_update_1(coder->is_match[state][pos_state]);

    case SEQ_IS_REP:
        rc_if_0(coder->is_rep[state], SEQ_IS_REP) {
            // Not a repeated match
            rc_update_0(coder->is_rep[state]);
            update_match(state);

            // The latest three match distances are kept in
            // memory in case there are repeated matches.
            rep3 = rep2;
            rep2 = rep1;
            rep1 = rep0;

            // Decode the length of the match.
            len_decode(len, coder->match_len_decoder,
                    pos_state, SEQ_MATCH_LEN);

            // Prepare to decode the highest two bits of the
            // match distance.
            probs = coder->pos_slot[get_len_to_pos_state(len)];
            symbol = 1;

#ifdef HAVE_SMALL
    case SEQ_POS_SLOT:
            do {
                rc_bit(probs[symbol], , , SEQ_POS_SLOT);
            } while (symbol < POS_SLOTS);
#else
            rc_bit_case(probs[symbol], , , SEQ_POS_SLOT0);
            rc_bit_case(probs[symbol], , , SEQ_POS_SLOT1);
            rc_bit_case(probs[symbol], , , SEQ_POS_SLOT2);
            rc_bit_case(probs[symbol], , , SEQ_POS_SLOT3);
            rc_bit_case(probs[symbol], , , SEQ_POS_SLOT4);
            rc_bit_case(probs[symbol], , , SEQ_POS_SLOT5);
#endif
            // Get rid of the highest bit that was needed for
            // indexing of the probability array.
            symbol -= POS_SLOTS;
            assert(symbol <= 63);

            if (symbol < START_POS_MODEL_INDEX) {
                // Match distances [0, 3] have only two bits.
                rep0 = symbol;
            } else {
                // Decode the lowest [1, 29] bits of
                // the match distance.
                limit = (symbol >> 1) - 1;
                assert(limit >= 1 && limit <= 30);
                rep0 = 2 + (symbol & 1);

                if (symbol < END_POS_MODEL_INDEX) {
                    // Prepare to decode the low bits for
                    // a distance of [4, 127].
                    assert(limit <= 5);
                    rep0 <<= limit;
                    assert(rep0 <= 96);
                    // -1 is fine, because we start
                    // decoding at probs[1], not probs[0].
                    // NOTE: This violates the C standard,
                    // since we are doing pointer
                    // arithmetic past the beginning of
                    // the array.
                    assert((int32_t)(rep0 - symbol - 1)
                            >= -1);
                    assert((int32_t)(rep0 - symbol - 1)
                            <= 82);
                    probs = coder->pos_special + rep0
                            - symbol - 1;
                    symbol = 1;
                    offset = 0;
    case SEQ_POS_MODEL:
#ifdef HAVE_SMALL
                    do {
                        rc_bit(probs[symbol], ,
                            rep0 += 1 << offset,
                            SEQ_POS_MODEL);
                    } while (++offset < limit);
#else
                    switch (limit) {
                    case 5:
                        assert(offset == 0);
                        rc_bit(probs[symbol], ,
                            rep0 += 1,
                            SEQ_POS_MODEL);
                        ++offset;
                        --limit;
                    case 4:
                        rc_bit(probs[symbol], ,
                            rep0 += 1 << offset,
                            SEQ_POS_MODEL);
                        ++offset;
                        --limit;
                    case 3:
                        rc_bit(probs[symbol], ,
                            rep0 += 1 << offset,
                            SEQ_POS_MODEL);
                        ++offset;
                        --limit;
                    case 2:
                        rc_bit(probs[symbol], ,
                            rep0 += 1 << offset,
                            SEQ_POS_MODEL);
                        ++offset;
                        --limit;
                    case 1:
                        // We need "symbol" only for
                        // indexing the probability
                        // array, thus we can use
                        // rc_bit_last() here to omit
                        // the unneeded updating of
                        // "symbol".
                        rc_bit_last(probs[symbol], ,
                            rep0 += 1 << offset,
                            SEQ_POS_MODEL);
                    }
#endif
                } else {
                    // The distace is >= 128. Decode the
                    // lower bits without probabilities
                    // except the lowest four bits.
                    assert(symbol >= 14);
                    assert(limit >= 6);
                    limit -= ALIGN_BITS;
                    assert(limit >= 2);
    case SEQ_DIRECT:
                    // Not worth manual unrolling
                    do {
                        rc_direct(rep0, SEQ_DIRECT);
                    } while (--limit > 0);

                    // Decode the lowest four bits using
                    // probabilities.
                    rep0 <<= ALIGN_BITS;
                    symbol = 1;
#ifdef HAVE_SMALL
                    offset = 0;
    case SEQ_ALIGN:
                    do {
                        rc_bit(coder->pos_align[
                                symbol], ,
                            rep0 += 1 << offset,
                            SEQ_ALIGN);
                    } while (++offset < ALIGN_BITS);
#else
    case SEQ_ALIGN0:
                    rc_bit(coder->pos_align[symbol], ,
                            rep0 += 1, SEQ_ALIGN0);
    case SEQ_ALIGN1:
                    rc_bit(coder->pos_align[symbol], ,
                            rep0 += 2, SEQ_ALIGN1);
    case SEQ_ALIGN2:
                    rc_bit(coder->pos_align[symbol], ,
                            rep0 += 4, SEQ_ALIGN2);
    case SEQ_ALIGN3:
                    // Like in SEQ_POS_MODEL, we don't
                    // need "symbol" for anything else
                    // than indexing the probability array.
                    rc_bit_last(coder->pos_align[symbol], ,
                            rep0 += 8, SEQ_ALIGN3);
#endif

                    if (rep0 == UINT32_MAX) {
                        // End of payload marker was
                        // found. It must not be
                        // present if uncompressed
                        // size is known.
                        if (coder->uncompressed_size
                        != LZMA_VLI_UNKNOWN) {
                            ret = LZMA_DATA_ERROR;
                            goto out;
                        }

    case SEQ_EOPM:
                        // TODO Comment
                        rc_normalize(SEQ_EOPM);
                        ret = LZMA_STREAM_END;
                        goto out;
                    }
                }
            }

            // Validate the distance we just decoded.
            if (unlikely(!dict_is_distance_valid(&dict, rep0))) {
                ret = LZMA_DATA_ERROR;
                goto out;
            }

        } else {
            rc_update_1(coder->is_rep[state]);

            // Repeated match
            //
            // The match distance is a value that we have had
            // earlier. The latest four match distances are
            // available as rep0, rep1, rep2 and rep3. We will
            // now decode which of them is the new distance.
            //
            // There cannot be a match if we haven't produced
            // any output, so check that first.
            if (unlikely(!dict_is_distance_valid(&dict, 0))) {
                ret = LZMA_DATA_ERROR;
                goto out;
            }

    case SEQ_IS_REP0:
            rc_if_0(coder->is_rep0[state], SEQ_IS_REP0) {
                rc_update_0(coder->is_rep0[state]);
                // The distance is rep0.

    case SEQ_IS_REP0_LONG:
                rc_if_0(coder->is_rep0_long[state][pos_state],
                        SEQ_IS_REP0_LONG) {
                    rc_update_0(coder->is_rep0_long[
                            state][pos_state]);

                    update_short_rep(state);

    case SEQ_SHORTREP:
                    if (unlikely(dict_put(&dict, dict_get(
                            &dict, rep0)))) {
                        coder->sequence = SEQ_SHORTREP;
                        goto out;
                    }

                    continue;
                }

                // Repeating more than one byte at
                // distance of rep0.
                rc_update_1(coder->is_rep0_long[
                        state][pos_state]);

            } else {
                rc_update_1(coder->is_rep0[state]);

    case SEQ_IS_REP1:
                // The distance is rep1, rep2 or rep3. Once
                // we find out which one of these three, it
                // is stored to rep0 and rep1, rep2 and rep3
                // are updated accordingly.
                rc_if_0(coder->is_rep1[state], SEQ_IS_REP1) {
                    rc_update_0(coder->is_rep1[state]);

                    const uint32_t distance = rep1;
                    rep1 = rep0;
                    rep0 = distance;

                } else {
                    rc_update_1(coder->is_rep1[state]);
    case SEQ_IS_REP2:
                    rc_if_0(coder->is_rep2[state],
                            SEQ_IS_REP2) {
                        rc_update_0(coder->is_rep2[
                                state]);

                        const uint32_t distance = rep2;
                        rep2 = rep1;
                        rep1 = rep0;
                        rep0 = distance;

                    } else {
                        rc_update_1(coder->is_rep2[
                                state]);

                        const uint32_t distance = rep3;
                        rep3 = rep2;
                        rep2 = rep1;
                        rep1 = rep0;
                        rep0 = distance;
                    }
                }
            }

            update_long_rep(state);

            // Decode the length of the repeated match.
            len_decode(len, coder->rep_len_decoder,
                    pos_state, SEQ_REP_LEN);
        }

        /////////////////////////////////
        // Repeat from history buffer. //
        /////////////////////////////////

        // The length is always between these limits. There is no way
        // to trigger the algorithm to set len outside this range.
        assert(len >= MATCH_LEN_MIN);
        assert(len <= MATCH_LEN_MAX);

    case SEQ_COPY:
        // Repeat len bytes from distance of rep0.
        if (unlikely(dict_repeat(&dict, rep0, &len))) {
            coder->sequence = SEQ_COPY;
            goto out;
        }
    }

    rc_normalize(SEQ_NORMALIZE);
    coder->sequence = SEQ_IS_MATCH;

out:
    // Save state

    // NOTE: Must not copy dict.limit.
    dictptr->pos = dict.pos;
    dictptr->full = dict.full;

    rc_from_local(coder->rc, *in_pos);

    coder->state = state;
    coder->rep0 = rep0;
    coder->rep1 = rep1;
    coder->rep2 = rep2;
    coder->rep3 = rep3;

    coder->probs = probs;
    coder->symbol = symbol;
    coder->limit = limit;
    coder->offset = offset;
    coder->len = len;

    // Update the remaining amount of uncompressed data if uncompressed
    // size was known.
    if (coder->uncompressed_size != LZMA_VLI_UNKNOWN) {
        coder->uncompressed_size -= dict.pos - dict_start;

        // Since there cannot be end of payload marker if the
        // uncompressed size was known, we check here if we
        // finished decoding.
        if (coder->uncompressed_size == 0 && ret == LZMA_OK
                && coder->sequence != SEQ_NORMALIZE)
            ret = coder->sequence == SEQ_IS_MATCH
                    ? LZMA_STREAM_END : LZMA_DATA_ERROR;
    }

    // We can do an additional check in the range decoder to catch some
    // corrupted files.
    if (ret == LZMA_STREAM_END) {
        if (!rc_is_finished(coder->rc))
            ret = LZMA_DATA_ERROR;

        // Reset the range decoder so that it is ready to reinitialize
        // for a new LZMA2 chunk.
        rc_reset(coder->rc);
    }

    return ret;
}



static void
lzma_decoder_uncompressed(lzma_coder *coder, lzma_vli uncompressed_size)
{
    coder->uncompressed_size = uncompressed_size;
}

/*
extern void
lzma_lzma_decoder_uncompressed(void *coder_ptr, lzma_vli uncompressed_size)
{
    // This is hack.
    (*(lzma_coder **)(coder))->uncompressed_size = uncompressed_size;
}
*/

static void
lzma_decoder_reset(lzma_coder *coder, const void *opt)
{
    const lzma_options_lzma *options = opt;

    // NOTE: We assume that lc/lp/pb are valid since they were
    // successfully decoded with lzma_lzma_decode_properties().
    // FIXME?

    // Calculate pos_mask. We don't need pos_bits as is for anything.
    coder->pos_mask = (1U << options->pb) - 1;

    // Initialize the literal decoder.
    literal_init(coder->literal, options->lc, options->lp);

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

    // State
    coder->state = STATE_LIT_LIT;
    coder->rep0 = 0;
    coder->rep1 = 0;
    coder->rep2 = 0;
    coder->rep3 = 0;
    coder->pos_mask = (1U << options->pb) - 1;

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

    // Bit and bittree decoders
    for (uint32_t i = 0; i < STATES; ++i) {
        for (uint32_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 (uint32_t i = 0; i < LEN_TO_POS_STATES; ++i)
        bittree_reset(coder->pos_slot[i], POS_SLOT_BITS);

    for (uint32_t i = 0; i < FULL_DISTANCES - END_POS_MODEL_INDEX; ++i)
        bit_reset(coder->pos_special[i]);

    bittree_reset(coder->pos_align, ALIGN_BITS);

    // Len decoders (also bit/bittree)
    const uint32_t num_pos_states = 1U << options->pb;
    bit_reset(coder->match_len_decoder.choice);
    bit_reset(coder->match_len_decoder.choice2);
    bit_reset(coder->rep_len_decoder.choice);
    bit_reset(coder->rep_len_decoder.choice2);

    for (uint32_t pos_state = 0; pos_state < num_pos_states; ++pos_state) {
        bittree_reset(coder->match_len_decoder.low[pos_state],
                LEN_LOW_BITS);
        bittree_reset(coder->match_len_decoder.mid[pos_state],
                LEN_MID_BITS);

        bittree_reset(coder->rep_len_decoder.low[pos_state],
                LEN_LOW_BITS);
        bittree_reset(coder->rep_len_decoder.mid[pos_state],
                LEN_MID_BITS);
    }

    bittree_reset(coder->match_len_decoder.high, LEN_HIGH_BITS);
    bittree_reset(coder->rep_len_decoder.high, LEN_HIGH_BITS);

    coder->sequence = SEQ_IS_MATCH;
    coder->probs = NULL;
    coder->symbol = 0;
    coder->limit = 0;
    coder->offset = 0;
    coder->len = 0;

    return;
}


extern lzma_ret
lzma_lzma_decoder_create(lzma_lz_decoder *lz, lzma_allocator *allocator,
        const void *opt, lzma_lz_options *lz_options)
{
    if (lz->coder == NULL) {
        lz->coder = lzma_alloc(sizeof(lzma_coder), allocator);
        if (lz->coder == NULL)
            return LZMA_MEM_ERROR;

        lz->code = &lzma_decode;
        lz->reset = &lzma_decoder_reset;
        lz->set_uncompressed = &lzma_decoder_uncompressed;
    }

    // All dictionary sizes are OK here. LZ decoder will take care of
    // the special cases.
    const lzma_options_lzma *options = opt;
    lz_options->dict_size = options->dict_size;
    lz_options->preset_dict = options->preset_dict;
    lz_options->preset_dict_size = options->preset_dict_size;

    return LZMA_OK;
}


/// Allocate and initialize LZMA decoder. This is used only via LZ
/// initialization (lzma_lzma_decoder_init() passes function pointer to
/// the LZ initialization).
static lzma_ret
lzma_decoder_init(lzma_lz_decoder *lz, lzma_allocator *allocator,
        const void *options, lzma_lz_options *lz_options)
{
    if (!is_lclppb_valid(options))
        return LZMA_PROG_ERROR;

    return_if_error(lzma_lzma_decoder_create(
            lz, allocator, options, lz_options));

    lzma_decoder_reset(lz->coder, options);
    lzma_decoder_uncompressed(lz->coder, LZMA_VLI_UNKNOWN);

    return LZMA_OK;
}


extern lzma_ret
lzma_lzma_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
        const lzma_filter_info *filters)
{
    // LZMA can only be the last filter in the chain. This is enforced
    // by the raw_decoder initialization.
    assert(filters[1].init == NULL);

    return lzma_lz_decoder_init(next, allocator, filters,
            &lzma_decoder_init);
}


extern bool
lzma_lzma_lclppb_decode(lzma_options_lzma *options, uint8_t byte)
{
    if (byte > (4 * 5 + 4) * 9 + 8)
        return true;

    // See the file format specification to understand this.
    options->pb = byte / (9 * 5);
    byte -= options->pb * 9 * 5;
    options->lp = byte / 9;
    options->lc = byte - options->lp * 9;

    return options->lc + options->lp > LZMA_LCLP_MAX;
}


extern uint64_t
lzma_lzma_decoder_memusage_nocheck(const void *options)
{
    const lzma_options_lzma *const opt = options;
    return sizeof(lzma_coder) + lzma_lz_decoder_memusage(opt->dict_size);
}


extern uint64_t
lzma_lzma_decoder_memusage(const void *options)
{
    if (!is_lclppb_valid(options))
        return UINT64_MAX;

    return lzma_lzma_decoder_memusage_nocheck(options);
}


extern lzma_ret
lzma_lzma_props_decode(void **options, lzma_allocator *allocator,
        const uint8_t *props, size_t props_size)
{
    if (props_size != 5)
        return LZMA_OPTIONS_ERROR;

    lzma_options_lzma *opt
            = lzma_alloc(sizeof(lzma_options_lzma), allocator);
    if (opt == NULL)
        return LZMA_MEM_ERROR;

    if (lzma_lzma_lclppb_decode(opt, props[0]))
        goto error;

    // All dictionary sizes are accepted, including zero. LZ decoder
    // will automatically use a dictionary at least a few KiB even if
    // a smaller dictionary is requested.
    opt->dict_size = integer_read_32(props + 1);

    opt->preset_dict = NULL;
    opt->preset_dict_size = 0;

    *options = opt;

    return LZMA_OK;

error:
    lzma_free(opt, allocator);
    return LZMA_OPTIONS_ERROR;
}