The R Project SVN R

///////////////////////////////////////////////////////////////////////////////
//
/// \file       block_encoder.c
/// \brief      Encodes .xz Blocks
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "block_encoder.h"
#include "filter_encoder.h"
#include "check.h"


struct lzma_coder_s {
    /// The filters in the chain; initialized with lzma_raw_decoder_init().
    lzma_next_coder next;

    /// Encoding options; we also write Unpadded Size, Compressed Size,
    /// and Uncompressed Size back to this structure when the encoding
    /// has been finished.
    lzma_block *block;

    enum {
        SEQ_CODE,
        SEQ_PADDING,
        SEQ_CHECK,
    } sequence;

    /// Compressed Size calculated while encoding
    lzma_vli compressed_size;

    /// Uncompressed Size calculated while encoding
    lzma_vli uncompressed_size;

    /// Position in the Check field
    size_t pos;

    /// Check of the uncompressed data
    lzma_check_state check;
};


static lzma_ret
block_encode(lzma_coder *coder, lzma_allocator *allocator,
        const uint8_t *restrict in, size_t *restrict in_pos,
        size_t in_size, uint8_t *restrict out,
        size_t *restrict out_pos, size_t out_size, lzma_action action)
{
    // Check that our amount of input stays in proper limits.
    if (LZMA_VLI_MAX - coder->uncompressed_size < in_size - *in_pos)
        return LZMA_DATA_ERROR;

    switch (coder->sequence) {
    case SEQ_CODE: {
        const size_t in_start = *in_pos;
        const size_t out_start = *out_pos;

        const lzma_ret ret = coder->next.code(coder->next.coder,
                allocator, in, in_pos, in_size,
                out, out_pos, out_size, action);

        const size_t in_used = *in_pos - in_start;
        const size_t out_used = *out_pos - out_start;

        if (COMPRESSED_SIZE_MAX - coder->compressed_size < out_used)
            return LZMA_DATA_ERROR;

        coder->compressed_size += out_used;

        // No need to check for overflow because we have already
        // checked it at the beginning of this function.
        coder->uncompressed_size += in_used;

        lzma_check_update(&coder->check, coder->block->check,
                in + in_start, in_used);

        if (ret != LZMA_STREAM_END || action == LZMA_SYNC_FLUSH)
            return ret;

        assert(*in_pos == in_size);
        assert(action == LZMA_FINISH);

        // Copy the values into coder->block. The caller
        // may use this information to construct Index.
        coder->block->compressed_size = coder->compressed_size;
        coder->block->uncompressed_size = coder->uncompressed_size;

        coder->sequence = SEQ_PADDING;
    }

    // Fall through

    case SEQ_PADDING:
        // Pad Compressed Data to a multiple of four bytes. We can
        // use coder->compressed_size for this since we don't need
        // it for anything else anymore.
        while (coder->compressed_size & 3) {
            if (*out_pos >= out_size)
                return LZMA_OK;

            out[*out_pos] = 0x00;
            ++*out_pos;
            ++coder->compressed_size;
        }

        if (coder->block->check == LZMA_CHECK_NONE)
            return LZMA_STREAM_END;

        lzma_check_finish(&coder->check, coder->block->check);

        coder->sequence = SEQ_CHECK;

    // Fall through

    case SEQ_CHECK: {
        const size_t check_size = lzma_check_size(coder->block->check);
        lzma_bufcpy(coder->check.buffer.u8, &coder->pos, check_size,
                out, out_pos, out_size);
        if (coder->pos < check_size)
            return LZMA_OK;

        memcpy(coder->block->raw_check, coder->check.buffer.u8,
                check_size);
        return LZMA_STREAM_END;
    }
    }

    return LZMA_PROG_ERROR;
}


static void
block_encoder_end(lzma_coder *coder, lzma_allocator *allocator)
{
    lzma_next_end(&coder->next, allocator);
    lzma_free(coder, allocator);
    return;
}


static lzma_ret
block_encoder_update(lzma_coder *coder, lzma_allocator *allocator,
        const lzma_filter *filters lzma_attribute((unused)),
        const lzma_filter *reversed_filters)
{
    if (coder->sequence != SEQ_CODE)
        return LZMA_PROG_ERROR;

    return lzma_next_filter_update(
            &coder->next, allocator, reversed_filters);
}


extern lzma_ret
lzma_block_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
        lzma_block *block)
{
    lzma_next_coder_init(&lzma_block_encoder_init, next, allocator);

    if (block->version != 0)
        return LZMA_OPTIONS_ERROR;

    // If the Check ID is not supported, we cannot calculate the check and
    // thus not create a proper Block.
    if ((unsigned int)(block->check) > LZMA_CHECK_ID_MAX)
        return LZMA_PROG_ERROR;

    if (!lzma_check_is_supported(block->check))
        return LZMA_UNSUPPORTED_CHECK;

    // Allocate and initialize *next->coder if needed.
    if (next->coder == NULL) {
        next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
        if (next->coder == NULL)
            return LZMA_MEM_ERROR;

        next->code = &block_encode;
        next->end = &block_encoder_end;
        next->update = &block_encoder_update;
        next->coder->next = LZMA_NEXT_CODER_INIT;
    }

    // Basic initializations
    next->coder->sequence = SEQ_CODE;
    next->coder->block = block;
    next->coder->compressed_size = 0;
    next->coder->uncompressed_size = 0;
    next->coder->pos = 0;

    // Initialize the check
    lzma_check_init(&next->coder->check, block->check);

    // Initialize the requested filters.
    return lzma_raw_encoder_init(&next->coder->next, allocator,
            block->filters);
}


extern LZMA_API(lzma_ret)
lzma_block_encoder(lzma_stream *strm, lzma_block *block)
{
    lzma_next_strm_init(lzma_block_encoder_init, strm, block);

    strm->internal->supported_actions[LZMA_RUN] = true;
    strm->internal->supported_actions[LZMA_FINISH] = true;

    return LZMA_OK;
}