The R Project SVN R

///////////////////////////////////////////////////////////////////////////////
//
/// \file       lzma2_decoder.c
/// \brief      LZMA2 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 "lzma2_decoder.h"
#include "lz_decoder.h"
#include "lzma_decoder.h"


struct lzma_coder_s {
    enum sequence {
        SEQ_CONTROL,
        SEQ_UNCOMPRESSED_1,
        SEQ_UNCOMPRESSED_2,
        SEQ_COMPRESSED_0,
        SEQ_COMPRESSED_1,
        SEQ_PROPERTIES,
        SEQ_LZMA,
        SEQ_COPY,
    } sequence;

    /// Sequence after the size fields have been decoded.
    enum sequence next_sequence;

    /// LZMA decoder
    lzma_lz_decoder lzma;

    /// Uncompressed size of LZMA chunk
    size_t uncompressed_size;

    /// Compressed size of the chunk (naturally equals to uncompressed
    /// size of uncompressed chunk)
    size_t compressed_size;

    /// True if properties are needed. This is false before the
    /// first LZMA chunk.
    bool need_properties;

    /// True if dictionary reset is needed. This is false before the
    /// first chunk (LZMA or uncompressed).
    bool need_dictionary_reset;

    lzma_options_lzma options;
};


static lzma_ret
lzma2_decode(lzma_coder *restrict coder, lzma_dict *restrict dict,
        const uint8_t *restrict in, size_t *restrict in_pos,
        size_t in_size)
{
    // With SEQ_LZMA it is possible that no new input is needed to do
    // some progress. The rest of the sequences assume that there is
    // at least one byte of input.
    while (*in_pos < in_size || coder->sequence == SEQ_LZMA)
    switch (coder->sequence) {
    case SEQ_CONTROL: {
        const uint32_t control = in[*in_pos];
        ++*in_pos;

        if (control >= 0xE0 || control == 1) {
            // Dictionary reset implies that next LZMA chunk has
            // to set new properties.
            coder->need_properties = true;
            coder->need_dictionary_reset = true;
        } else if (coder->need_dictionary_reset) {
            return LZMA_DATA_ERROR;
        }

        if (control >= 0x80) {
            // LZMA chunk. The highest five bits of the
            // uncompressed size are taken from the control byte.
            coder->uncompressed_size = (control & 0x1F) << 16;
            coder->sequence = SEQ_UNCOMPRESSED_1;

            // See if there are new properties or if we need to
            // reset the state.
            if (control >= 0xC0) {
                // When there are new properties, state reset
                // is done at SEQ_PROPERTIES.
                coder->need_properties = false;
                coder->next_sequence = SEQ_PROPERTIES;

            } else if (coder->need_properties) {
                return LZMA_DATA_ERROR;

            } else {
                coder->next_sequence = SEQ_LZMA;

                // If only state reset is wanted with old
                // properties, do the resetting here for
                // simplicity.
                if (control >= 0xA0)
                    coder->lzma.reset(coder->lzma.coder,
                            &coder->options);
            }
        } else {
            // End marker
            if (control == 0x00)
                return LZMA_STREAM_END;

            // Invalid control values
            if (control > 2)
                return LZMA_DATA_ERROR;

            // It's uncompressed chunk
            coder->sequence = SEQ_COMPRESSED_0;
            coder->next_sequence = SEQ_COPY;
        }

        if (coder->need_dictionary_reset) {
            // Finish the dictionary reset and let the caller
            // flush the dictionary to the actual output buffer.
            coder->need_dictionary_reset = false;
            dict_reset(dict);
            return LZMA_OK;
        }

        break;
    }

    case SEQ_UNCOMPRESSED_1:
        coder->uncompressed_size += (uint32_t)(in[(*in_pos)++]) << 8;
        coder->sequence = SEQ_UNCOMPRESSED_2;
        break;

    case SEQ_UNCOMPRESSED_2:
        coder->uncompressed_size += in[(*in_pos)++] + 1;
        coder->sequence = SEQ_COMPRESSED_0;
        coder->lzma.set_uncompressed(coder->lzma.coder,
                coder->uncompressed_size);
        break;

    case SEQ_COMPRESSED_0:
        coder->compressed_size = (uint32_t)(in[(*in_pos)++]) << 8;
        coder->sequence = SEQ_COMPRESSED_1;
        break;

    case SEQ_COMPRESSED_1:
        coder->compressed_size += in[(*in_pos)++] + 1;
        coder->sequence = coder->next_sequence;
        break;

    case SEQ_PROPERTIES:
        if (lzma_lzma_lclppb_decode(&coder->options, in[(*in_pos)++]))
            return LZMA_DATA_ERROR;

        coder->lzma.reset(coder->lzma.coder, &coder->options);

        coder->sequence = SEQ_LZMA;
        break;

    case SEQ_LZMA: {
        // Store the start offset so that we can update
        // coder->compressed_size later.
        const size_t in_start = *in_pos;

        // Decode from in[] to *dict.
        const lzma_ret ret = coder->lzma.code(coder->lzma.coder,
                dict, in, in_pos, in_size);

        // Validate and update coder->compressed_size.
        const size_t in_used = *in_pos - in_start;
        if (in_used > coder->compressed_size)
            return LZMA_DATA_ERROR;

        coder->compressed_size -= in_used;

        // Return if we didn't finish the chunk, or an error occurred.
        if (ret != LZMA_STREAM_END)
            return ret;

        // The LZMA decoder must have consumed the whole chunk now.
        // We don't need to worry about uncompressed size since it
        // is checked by the LZMA decoder.
        if (coder->compressed_size != 0)
            return LZMA_DATA_ERROR;

        coder->sequence = SEQ_CONTROL;
        break;
    }

    case SEQ_COPY: {
        // Copy from input to the dictionary as is.
        // FIXME Can copy too much?
        dict_write(dict, in, in_pos, in_size, &coder->compressed_size);
        if (coder->compressed_size != 0)
            return LZMA_OK;

        coder->sequence = SEQ_CONTROL;
        break;
    }

    default:
        assert(0);
        return LZMA_PROG_ERROR;
    }

    return LZMA_OK;
}


static void
lzma2_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
{
    assert(coder->lzma.end == NULL);
    lzma_free(coder->lzma.coder, allocator);

    lzma_free(coder, allocator);

    return;
}


static lzma_ret
lzma2_decoder_init(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 = &lzma2_decode;
        lz->end = &lzma2_decoder_end;

        lz->coder->lzma = LZMA_LZ_DECODER_INIT;
    }

    const lzma_options_lzma *options = opt;

    lz->coder->sequence = SEQ_CONTROL;
    lz->coder->need_properties = true;
    lz->coder->need_dictionary_reset = options->preset_dict == NULL
            || options->preset_dict_size == 0;

    return lzma_lzma_decoder_create(&lz->coder->lzma,
            allocator, options, lz_options);
}


extern lzma_ret
lzma_lzma2_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
        const lzma_filter_info *filters)
{
    // LZMA2 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,
            &lzma2_decoder_init);
}


extern uint64_t
lzma_lzma2_decoder_memusage(const void *options)
{
    return sizeof(lzma_coder)
            + lzma_lzma_decoder_memusage_nocheck(options);
}


extern lzma_ret
lzma_lzma2_props_decode(void **options, lzma_allocator *allocator,
        const uint8_t *props, size_t props_size)
{
    if (props_size != 1)
        return LZMA_OPTIONS_ERROR;

    // Check that reserved bits are unset.
    if (props[0] & 0xC0)
        return LZMA_OPTIONS_ERROR;

    // Decode the dictionary size.
    if (props[0] > 40)
        return LZMA_OPTIONS_ERROR;

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

    if (props[0] == 40) {
        opt->dict_size = UINT32_MAX;
    } else {
        opt->dict_size = 2 | (props[0] & 1);
        opt->dict_size <<= props[0] / 2 + 11;
    }

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

    *options = opt;

    return LZMA_OK;
}