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

//

/// \file stream_flags_decoder.c

/// \brief Decodes Stream Header and Stream Footer from .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_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 != unaligned_read32le(in + sizeof(lzma_header_magic)

+ LZMA_STREAM_FLAGS_SIZE))

return LZMA_DATA_ERROR;

// 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 != unaligned_read32le(in))

return LZMA_DATA_ERROR;

// Stream Flags

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

return LZMA_OPTIONS_ERROR;

// Backward Size

options->backward_size = unaligned_read32le(in + sizeof(uint32_t));

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

return LZMA_OK;

}