src/liblzma/common/stream_flags_encoder.c

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