The R Project SVN R

///////////////////////////////////////////////////////////////////////////////
//
/// \file       lzma2_encoder.c
/// \brief      LZMA2 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 "lz_encoder.h"
#include "lzma_encoder.h"
#include "fastpos.h"
#include "lzma2_encoder.h"


struct lzma_coder_s {
    enum {
        SEQ_INIT,
        SEQ_LZMA_ENCODE,
        SEQ_LZMA_COPY,
        SEQ_UNCOMPRESSED_HEADER,
        SEQ_UNCOMPRESSED_COPY,
    } sequence;

    /// LZMA encoder
    lzma_coder *lzma;

    /// If this is not NULL, we will check new options from this
    /// structure when starting a new chunk.
    const lzma_options_lzma *opt_new;

    /// LZMA options currently in use.
    lzma_options_lzma opt_cur;

    bool need_properties;
    bool need_state_reset;
    bool need_dictionary_reset;

    /// Uncompressed size of a chunk
    size_t uncompressed_size;

    /// Compressed size of a chunk (excluding headers); this is also used
    /// to indicate the end of buf[] in SEQ_LZMA_COPY.
    size_t compressed_size;

    /// Read position in buf[]
    size_t buf_pos;

    /// Buffer to hold the chunk header and LZMA compressed data
    uint8_t buf[LZMA2_HEADER_MAX + LZMA2_CHUNK_MAX];
};


static void
lzma2_header_lzma(lzma_coder *coder)
{
    assert(coder->uncompressed_size > 0);
    assert(coder->uncompressed_size <= LZMA2_UNCOMPRESSED_MAX);
    assert(coder->compressed_size > 0);
    assert(coder->compressed_size <= LZMA2_CHUNK_MAX);

    size_t pos;

    if (coder->need_properties) {
        pos = 0;

        if (coder->need_dictionary_reset)
            coder->buf[pos] = 0x80 + (3 << 5);
        else
            coder->buf[pos] = 0x80 + (2 << 5);
    } else {
        pos = 1;

        if (coder->need_state_reset)
            coder->buf[pos] = 0x80 + (1 << 5);
        else
            coder->buf[pos] = 0x80;
    }

    // Set the start position for copying.
    coder->buf_pos = pos;

    // Uncompressed size
    size_t size = coder->uncompressed_size - 1;
    coder->buf[pos++] += size >> 16;
    coder->buf[pos++] = (size >> 8) & 0xFF;
    coder->buf[pos++] = size & 0xFF;

    // Compressed size
    size = coder->compressed_size - 1;
    coder->buf[pos++] = size >> 8;
    coder->buf[pos++] = size & 0xFF;

    // Properties, if needed
    if (coder->need_properties)
        lzma_lzma_lclppb_encode(&coder->opt_cur, coder->buf + pos);

    coder->need_properties = false;
    coder->need_state_reset = false;
    coder->need_dictionary_reset = false;

    // The copying code uses coder->compressed_size to indicate the end
    // of coder->buf[], so we need add the maximum size of the header here.
    coder->compressed_size += LZMA2_HEADER_MAX;

    return;
}


static void
lzma2_header_uncompressed(lzma_coder *coder)
{
    assert(coder->uncompressed_size > 0);
    assert(coder->uncompressed_size <= LZMA2_CHUNK_MAX);

    // If this is the first chunk, we need to include dictionary
    // reset indicator.
    if (coder->need_dictionary_reset)
        coder->buf[0] = 1;
    else
        coder->buf[0] = 2;

    coder->need_dictionary_reset = false;

    // "Compressed" size
    coder->buf[1] = (coder->uncompressed_size - 1) >> 8;
    coder->buf[2] = (coder->uncompressed_size - 1) & 0xFF;

    // Set the start position for copying.
    coder->buf_pos = 0;
    return;
}


static lzma_ret
lzma2_encode(lzma_coder *restrict coder, lzma_mf *restrict mf,
        uint8_t *restrict out, size_t *restrict out_pos,
        size_t out_size)
{
    while (*out_pos < out_size)
    switch (coder->sequence) {
    case SEQ_INIT:
        // If there's no input left and we are flushing or finishing,
        // don't start a new chunk.
        if (mf_unencoded(mf) == 0) {
            // Write end of payload marker if finishing.
            if (mf->action == LZMA_FINISH)
                out[(*out_pos)++] = 0;

            return mf->action == LZMA_RUN
                    ? LZMA_OK : LZMA_STREAM_END;
        }

        // Look if there are new options. At least for now,
        // only lc/lp/pb can be changed.
        if (coder->opt_new != NULL
                && (coder->opt_cur.lc != coder->opt_new->lc
                || coder->opt_cur.lp != coder->opt_new->lp
                || coder->opt_cur.pb != coder->opt_new->pb)) {
            // Options have been changed, copy them to opt_cur.
            // These get validated as part of
            // lzma_lzma_encoder_reset() below.
            coder->opt_cur.lc = coder->opt_new->lc;
            coder->opt_cur.lp = coder->opt_new->lp;
            coder->opt_cur.pb = coder->opt_new->pb;

            // We need to write the new options and reset
            // the encoder state.
            coder->need_properties = true;
            coder->need_state_reset = true;
        }

        if (coder->need_state_reset)
            return_if_error(lzma_lzma_encoder_reset(
                    coder->lzma, &coder->opt_cur));

        coder->uncompressed_size = 0;
        coder->compressed_size = 0;
        coder->sequence = SEQ_LZMA_ENCODE;

    // Fall through

    case SEQ_LZMA_ENCODE: {
        // Calculate how much more uncompressed data this chunk
        // could accept.
        const uint32_t left = LZMA2_UNCOMPRESSED_MAX
                - coder->uncompressed_size;
        uint32_t limit;

        if (left < mf->match_len_max) {
            // Must flush immediatelly since the next LZMA symbol
            // could make the uncompressed size of the chunk too
            // big.
            limit = 0;
        } else {
            // Calculate maximum read_limit that is OK from point
            // of view of LZMA2 chunk size.
            limit = mf->read_pos - mf->read_ahead
                    + left - mf->match_len_max;
        }

        // Save the start position so that we can update
        // coder->uncompressed_size.
        const uint32_t read_start = mf->read_pos - mf->read_ahead;

        // Call the LZMA encoder until the chunk is finished.
        const lzma_ret ret = lzma_lzma_encode(coder->lzma, mf,
                coder->buf + LZMA2_HEADER_MAX,
                &coder->compressed_size,
                LZMA2_CHUNK_MAX, limit);

        coder->uncompressed_size += mf->read_pos - mf->read_ahead
                - read_start;

        assert(coder->compressed_size <= LZMA2_CHUNK_MAX);
        assert(coder->uncompressed_size <= LZMA2_UNCOMPRESSED_MAX);

        if (ret != LZMA_STREAM_END)
            return LZMA_OK;

        // See if the chunk compressed. If it didn't, we encode it
        // as uncompressed chunk. This saves a few bytes of space
        // and makes decoding faster.
        if (coder->compressed_size >= coder->uncompressed_size) {
            coder->uncompressed_size += mf->read_ahead;
            assert(coder->uncompressed_size
                    <= LZMA2_UNCOMPRESSED_MAX);
            mf->read_ahead = 0;
            lzma2_header_uncompressed(coder);
            coder->need_state_reset = true;
            coder->sequence = SEQ_UNCOMPRESSED_HEADER;
            break;
        }

        // The chunk did compress at least by one byte, so we store
        // the chunk as LZMA.
        lzma2_header_lzma(coder);

        coder->sequence = SEQ_LZMA_COPY;
    }

    // Fall through

    case SEQ_LZMA_COPY:
        // Copy the compressed chunk along its headers to the
        // output buffer.
        lzma_bufcpy(coder->buf, &coder->buf_pos,
                coder->compressed_size,
                out, out_pos, out_size);
        if (coder->buf_pos != coder->compressed_size)
            return LZMA_OK;

        coder->sequence = SEQ_INIT;
        break;

    case SEQ_UNCOMPRESSED_HEADER:
        // Copy the three-byte header to indicate uncompressed chunk.
        lzma_bufcpy(coder->buf, &coder->buf_pos,
                LZMA2_HEADER_UNCOMPRESSED,
                out, out_pos, out_size);
        if (coder->buf_pos != LZMA2_HEADER_UNCOMPRESSED)
            return LZMA_OK;

        coder->sequence = SEQ_UNCOMPRESSED_COPY;

    // Fall through

    case SEQ_UNCOMPRESSED_COPY:
        // Copy the uncompressed data as is from the dictionary
        // to the output buffer.
        mf_read(mf, out, out_pos, out_size, &coder->uncompressed_size);
        if (coder->uncompressed_size != 0)
            return LZMA_OK;

        coder->sequence = SEQ_INIT;
        break;
    }

    return LZMA_OK;
}


static void
lzma2_encoder_end(lzma_coder *coder, lzma_allocator *allocator)
{
    lzma_free(coder->lzma, allocator);
    lzma_free(coder, allocator);
    return;
}


static lzma_ret
lzma2_encoder_init(lzma_lz_encoder *lz, lzma_allocator *allocator,
        const void *options, lzma_lz_options *lz_options)
{
    if (options == NULL)
        return LZMA_PROG_ERROR;

    if (lz->coder == NULL) {
        lz->coder = lzma_alloc(sizeof(lzma_coder), allocator);
        if (lz->coder == NULL)
            return LZMA_MEM_ERROR;

        lz->code = &lzma2_encode;
        lz->end = &lzma2_encoder_end;

        lz->coder->lzma = NULL;
    }

    lz->coder->opt_cur = *(const lzma_options_lzma *)(options);
    lz->coder->opt_new = lz->coder->opt_cur.persistent
                ? options : NULL;

    lz->coder->sequence = SEQ_INIT;
    lz->coder->need_properties = true;
    lz->coder->need_state_reset = false;
    lz->coder->need_dictionary_reset
            = lz->coder->opt_cur.preset_dict == NULL
            || lz->coder->opt_cur.preset_dict_size == 0;

    // Initialize LZMA encoder
    return_if_error(lzma_lzma_encoder_create(&lz->coder->lzma, allocator,
            &lz->coder->opt_cur, lz_options));

    // Make sure that we will always have enough history available in
    // case we need to use uncompressed chunks. They are used when the
    // compressed size of a chunk is not smaller than the uncompressed
    // size, so we need to have at least LZMA2_COMPRESSED_MAX bytes
    // history available.
    if (lz_options->before_size + lz_options->dict_size < LZMA2_CHUNK_MAX)
        lz_options->before_size
                = LZMA2_CHUNK_MAX - lz_options->dict_size;

    return LZMA_OK;
}


extern lzma_ret
lzma_lzma2_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
        const lzma_filter_info *filters)
{
    return lzma_lz_encoder_init(
            next, allocator, filters, &lzma2_encoder_init);
}


extern uint64_t
lzma_lzma2_encoder_memusage(const void *options)
{
    const uint64_t lzma_mem = lzma_lzma_encoder_memusage(options);
    if (lzma_mem == UINT64_MAX)
        return UINT64_MAX;

    return sizeof(lzma_coder) + lzma_mem;
}


extern lzma_ret
lzma_lzma2_props_encode(const void *options, uint8_t *out)
{
    const lzma_options_lzma *const opt = options;
    uint32_t d = MAX(opt->dict_size, LZMA_DICT_SIZE_MIN);

    // Round up to to the next 2^n - 1 or 2^n + 2^(n - 1) - 1 depending
    // on which one is the next:
    --d;
    d |= d >> 2;
    d |= d >> 3;
    d |= d >> 4;
    d |= d >> 8;
    d |= d >> 16;

    // Get the highest two bits using the proper encoding:
    if (d == UINT32_MAX)
        out[0] = 40;
    else
        out[0] = get_pos_slot(d + 1) - 24;

    return LZMA_OK;
}