The R Project SVN R

///////////////////////////////////////////////////////////////////////////////
//
/// \file       stream_flags_encoder.c
/// \brief      Encodes Stream Header and Stream Footer for .xz files
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "stream_flags_common.h"


static bool
stream_flags_encode(const lzma_stream_flags *options, uint8_t *out)
{
    if ((unsigned int)(options->check) > LZMA_CHECK_ID_MAX)
        return true;

    out[0] = 0x00;
    out[1] = options->check;

    return false;
}


extern LZMA_API(lzma_ret)
lzma_stream_header_encode(const lzma_stream_flags *options, uint8_t *out)
{
    assert(sizeof(lzma_header_magic) + LZMA_STREAM_FLAGS_SIZE
            + 4 == LZMA_STREAM_HEADER_SIZE);

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

    // Magic
    memcpy(out, lzma_header_magic, sizeof(lzma_header_magic));

    // Stream Flags
    if (stream_flags_encode(options, out + sizeof(lzma_header_magic)))
        return LZMA_PROG_ERROR;

    // CRC32 of the Stream Header
    const uint32_t crc = lzma_crc32(out + sizeof(lzma_header_magic),
            LZMA_STREAM_FLAGS_SIZE, 0);

    unaligned_write32le(out + sizeof(lzma_header_magic)
            + LZMA_STREAM_FLAGS_SIZE, crc);

    return LZMA_OK;
}


extern LZMA_API(lzma_ret)
lzma_stream_footer_encode(const lzma_stream_flags *options, uint8_t *out)
{
    assert(2 * 4 + LZMA_STREAM_FLAGS_SIZE + sizeof(lzma_footer_magic)
            == LZMA_STREAM_HEADER_SIZE);

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

    // Backward Size
    if (!is_backward_size_valid(options))
        return LZMA_PROG_ERROR;

    unaligned_write32le(out + 4, options->backward_size / 4 - 1);

    // Stream Flags
    if (stream_flags_encode(options, out + 2 * 4))
        return LZMA_PROG_ERROR;

    // CRC32
    const uint32_t crc = lzma_crc32(
            out + 4, 4 + LZMA_STREAM_FLAGS_SIZE, 0);

    unaligned_write32le(out, crc);

    // Magic
    memcpy(out + 2 * 4 + LZMA_STREAM_FLAGS_SIZE,
            lzma_footer_magic, sizeof(lzma_footer_magic));

    return LZMA_OK;
}