// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////

//

/// \file       stream_flags_decoder.c

/// \brief      Decodes Stream Header and Stream Footer from .xz files

//

//  Author:     Lasse Collin

//

///////////////////////////////////////////////////////////////////////////////

#include "stream_flags_common.h"

static bool

stream_flags_decode(lzma_stream_flags *options, const uint8_t *in)

{

  // Reserved bits must be unset.

  if (in[0] != 0x00 || (in[1] & 0xF0))

    return true;

  options->version = 0;

  options->check = in[1] & 0x0F;

  return false;

}

extern LZMA_API(lzma_ret)

lzma_stream_header_decode(lzma_stream_flags *options, const uint8_t *in)

{

  // Magic

  if (memcmp(in, lzma_header_magic, sizeof(lzma_header_magic)) != 0)

    return LZMA_FORMAT_ERROR;

  // Verify the CRC32 so we can distinguish between corrupt

  // and unsupported files.

  const uint32_t crc = lzma_crc32(in + sizeof(lzma_header_magic),

      LZMA_STREAM_FLAGS_SIZE, 0);

  if (crc != read32le(in + sizeof(lzma_header_magic)

      + LZMA_STREAM_FLAGS_SIZE)) {

#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION

    return LZMA_DATA_ERROR;

#endif

  }

  // Stream Flags

  if (stream_flags_decode(options, in + sizeof(lzma_header_magic)))

    return LZMA_OPTIONS_ERROR;

  // Set Backward Size to indicate unknown value. That way

  // lzma_stream_flags_compare() can be used to compare Stream Header

  // and Stream Footer while keeping it useful also for comparing

  // two Stream Footers.

  options->backward_size = LZMA_VLI_UNKNOWN;

  return LZMA_OK;

}

extern LZMA_API(lzma_ret)

lzma_stream_footer_decode(lzma_stream_flags *options, const uint8_t *in)

{

  // Magic

  if (memcmp(in + sizeof(uint32_t) * 2 + LZMA_STREAM_FLAGS_SIZE,

      lzma_footer_magic, sizeof(lzma_footer_magic)) != 0)

    return LZMA_FORMAT_ERROR;

  // CRC32

  const uint32_t crc = lzma_crc32(in + sizeof(uint32_t),

      sizeof(uint32_t) + LZMA_STREAM_FLAGS_SIZE, 0);

  if (crc != read32le(in)) {

#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION

    return LZMA_DATA_ERROR;

#endif

  }

  // Stream Flags

  if (stream_flags_decode(options, in + sizeof(uint32_t) * 2))

    return LZMA_OPTIONS_ERROR;

  // Backward Size

  options->backward_size = read32le(in + sizeof(uint32_t));

  options->backward_size = (options->backward_size + 1) * 4;

  return LZMA_OK;

}