src/liblzma/common/stream_flags_encoder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       stream_flags_encoder.c
   4 /// \brief      Encodes Stream Header and Stream Footer for .xz files
   5 //
   6 //  Author:     Lasse Collin
   7 //
   8 //  This file has been put into the public domain.
   9 //  You can do whatever you want with this file.
  10 //
  11 ///////////////////////////////////////////////////////////////////////////////
  12
  13 #include "stream_flags_common.h"
  14
  15
  16 static bool
  17 stream_flags_encode(const lzma_stream_flags *options, uint8_t *out)
  18 {
  19         if ((unsigned int)(options->check) > LZMA_CHECK_ID_MAX)
  20                 return true;
  21
  22         out[0] = 0x00;
  23         out[1] = options->check;
  24
  25         return false;
  26 }
  27
  28
  29 extern LZMA_API(lzma_ret)
  30 lzma_stream_header_encode(const lzma_stream_flags *options, uint8_t *out)
  31 {
  32         assert(sizeof(lzma_header_magic) + LZMA_STREAM_FLAGS_SIZE
  33                         + 4 == LZMA_STREAM_HEADER_SIZE);
  34
  35         if (options->version != 0)
  36                 return LZMA_OPTIONS_ERROR;
  37
  38         // Magic
  39         memcpy(out, lzma_header_magic, sizeof(lzma_header_magic));
  40
  41         // Stream Flags
  42         if (stream_flags_encode(options, out + sizeof(lzma_header_magic)))
  43                 return LZMA_PROG_ERROR;
  44
  45         // CRC32 of the Stream Header
  46         const uint32_t crc = lzma_crc32(out + sizeof(lzma_header_magic),
  47                         LZMA_STREAM_FLAGS_SIZE, 0);
  48
  49         write32le(out + sizeof(lzma_header_magic) + LZMA_STREAM_FLAGS_SIZE,
  50                         crc);
  51
  52         return LZMA_OK;
  53 }
  54
  55
  56 extern LZMA_API(lzma_ret)
  57 lzma_stream_footer_encode(const lzma_stream_flags *options, uint8_t *out)
  58 {
  59         assert(2 * 4 + LZMA_STREAM_FLAGS_SIZE + sizeof(lzma_footer_magic)
  60                         == LZMA_STREAM_HEADER_SIZE);
  61
  62         if (options->version != 0)
  63                 return LZMA_OPTIONS_ERROR;
  64
  65         // Backward Size
  66         if (!is_backward_size_valid(options))
  67                 return LZMA_PROG_ERROR;
  68
  69         write32le(out + 4, options->backward_size / 4 - 1);
  70
  71         // Stream Flags
  72         if (stream_flags_encode(options, out + 2 * 4))
  73                 return LZMA_PROG_ERROR;
  74
  75         // CRC32
  76         const uint32_t crc = lzma_crc32(
  77                         out + 4, 4 + LZMA_STREAM_FLAGS_SIZE, 0);
  78
  79         write32le(out, crc);
  80
  81         // Magic
  82         memcpy(out + 2 * 4 + LZMA_STREAM_FLAGS_SIZE,
  83                         lzma_footer_magic, sizeof(lzma_footer_magic));
  84
  85         return LZMA_OK;
  86 }