scripts/functions.sh

   1 #!/bin/sh
   2
   3
   4 get_magic_word() {
   5         dd if=$1 bs=4 count=1 2>/dev/null | od -A n -N 4 -t x1 | tr -d ' '
   6 }
   7
   8 get_post_padding_word() {
   9         local rootfs_length="$(stat -c%s "$1")"
  10         [ "$rootfs_length" -ge 4 ] || return
  11         rootfs_length=$((rootfs_length-4))
  12
  13         # the JFFS2 end marker must be on a 4K boundary (often 64K or 256K)
  14         local unaligned_bytes=$((rootfs_length%4096))
  15         [ "$unaligned_bytes" = 0 ] || return
  16
  17         # skip rootfs data except the potential EOF marker
  18         dd if="$1" bs=1 skip="$rootfs_length" 2>/dev/null | od -A n -N 4 -t x1 | tr -d ' '
  19 }
  20
  21 get_fs_type() {
  22         local magic_word="$(get_magic_word "$1")"
  23
  24         case "$magic_word" in
  25         "3118"*)
  26                 echo "ubifs"
  27                 ;;
  28         "68737173")
  29                 local post_padding_word="$(get_post_padding_word "$1")"
  30
  31                 case "$post_padding_word" in
  32                 "deadc0de")
  33                         echo "squashfs-jffs2"
  34                         ;;
  35                 *)
  36                         echo "squashfs"
  37                         ;;
  38                 esac
  39                 ;;
  40         *)
  41                 echo "unknown"
  42                 ;;
  43         esac
  44 }
  45
  46 round_up() {
  47         echo "$(((($1 + ($2 - 1))/ $2) * $2))"
  48 }