The R Project SVN R

///////////////////////////////////////////////////////////////////////////////
//
/// \file       stream_buffer_encoder.c
/// \brief      Single-call .xz Stream encoder
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "index.h"


/// Maximum size of Index that has exactly one Record.
/// Index Indicator + Number of Records + Record + CRC32 rounded up to
/// the next multiple of four.
#define INDEX_BOUND ((1 + 1 + 2 * LZMA_VLI_BYTES_MAX + 4 + 3) & ~3)

/// Stream Header, Stream Footer, and Index
#define HEADERS_BOUND (2 * LZMA_STREAM_HEADER_SIZE + INDEX_BOUND)


extern LZMA_API(size_t)
lzma_stream_buffer_bound(size_t uncompressed_size)
{
    // Get the maximum possible size of a Block.
    const size_t block_bound = lzma_block_buffer_bound(uncompressed_size);
    if (block_bound == 0)
        return 0;

    // Catch the possible integer overflow and also prevent the size of
    // the Stream exceeding LZMA_VLI_MAX (theoretically possible on
    // 64-bit systems).
    if (my_min(SIZE_MAX, LZMA_VLI_MAX) - block_bound < HEADERS_BOUND)
        return 0;

    return block_bound + HEADERS_BOUND;
}


extern LZMA_API(lzma_ret)
lzma_stream_buffer_encode(lzma_filter *filters, lzma_check check,
        lzma_allocator *allocator, const uint8_t *in, size_t in_size,
        uint8_t *out, size_t *out_pos_ptr, size_t out_size)
{
    // Sanity checks
    if (filters == NULL || (unsigned int)(check) > LZMA_CHECK_ID_MAX
            || (in == NULL && in_size != 0) || out == NULL
            || out_pos_ptr == NULL || *out_pos_ptr > out_size)
        return LZMA_PROG_ERROR;

    // Note for the paranoids: Index encoder prevents the Stream from
    // getting too big and still being accepted with LZMA_OK, and Block
    // encoder catches if the input is too big. So we don't need to
    // separately check if the buffers are too big.

    // Use a local copy. We update *out_pos_ptr only if everything
    // succeeds.
    size_t out_pos = *out_pos_ptr;

    // Check that there's enough space for both Stream Header and
    // Stream Footer.
    if (out_size - out_pos <= 2 * LZMA_STREAM_HEADER_SIZE)
        return LZMA_BUF_ERROR;

    // Reserve space for Stream Footer so we don't need to check for
    // available space again before encoding Stream Footer.
    out_size -= LZMA_STREAM_HEADER_SIZE;

    // Encode the Stream Header.
    lzma_stream_flags stream_flags = {
        .version = 0,
        .check = check,
    };

    if (lzma_stream_header_encode(&stream_flags, out + out_pos)
            != LZMA_OK)
        return LZMA_PROG_ERROR;

    out_pos += LZMA_STREAM_HEADER_SIZE;

    // Block
    lzma_block block = {
        .version = 0,
        .check = check,
        .filters = filters,
    };

    return_if_error(lzma_block_buffer_encode(&block, allocator,
            in, in_size, out, &out_pos, out_size));

    // Index
    {
        // Create an Index with one Record.
        lzma_index *i = lzma_index_init(allocator);
        if (i == NULL)
            return LZMA_MEM_ERROR;

        lzma_ret ret = lzma_index_append(i, allocator,
                lzma_block_unpadded_size(&block),
                block.uncompressed_size);

        // If adding the Record was successful, encode the Index
        // and get its size which will be stored into Stream Footer.
        if (ret == LZMA_OK) {
            ret = lzma_index_buffer_encode(
                    i, out, &out_pos, out_size);

            stream_flags.backward_size = lzma_index_size(i);
        }

        lzma_index_end(i, allocator);

        if (ret != LZMA_OK)
            return ret;
    }

    // Stream Footer. We have already reserved space for this.
    if (lzma_stream_footer_encode(&stream_flags, out + out_pos)
            != LZMA_OK)
        return LZMA_PROG_ERROR;

    out_pos += LZMA_STREAM_HEADER_SIZE;

    // Everything went fine, make the new output position available
    // to the application.
    *out_pos_ptr = out_pos;
    return LZMA_OK;
}