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///////////////////////////////////////////////////////////////////////////////
//
/// \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;
}
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