t/lib-pack.sh

   1 #!/bin/sh
   2 #
   3 # Support routines for hand-crafting weird or malicious packs.
   4 #
   5 # You can make a complete pack like:
   6 #
   7 #   pack_header 2 >foo.pack &&
   8 #   pack_obj e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 >>foo.pack &&
   9 #   pack_obj e68fe8129b546b101aee9510c5328e7f21ca1d18 >>foo.pack &&
  10 #   pack_trailer foo.pack
  11
  12 # Print the big-endian 4-byte octal representation of $1
  13 uint32_octal () {
  14         n=$1
  15         printf '\\%o' $(($n / 16777216)); n=$((n % 16777216))
  16         printf '\\%o' $(($n /    65536)); n=$((n %    65536))
  17         printf '\\%o' $(($n /      256)); n=$((n %      256))
  18         printf '\\%o' $(($n           ));
  19 }
  20
  21 # Print the big-endian 4-byte binary representation of $1
  22 uint32_binary () {
  23         printf "$(uint32_octal "$1")"
  24 }
  25
  26 # Print a pack header, version 2, for a pack with $1 objects
  27 pack_header () {
  28         printf 'PACK' &&
  29         printf '\0\0\0\2' &&
  30         uint32_binary "$1"
  31 }
  32
  33 # Print the pack data for object $1, as a delta against object $2 (or as a full
  34 # object if $2 is missing or empty). The output is suitable for including
  35 # directly in the packfile, and represents the entirety of the object entry.
  36 # Doing this on the fly (especially picking your deltas) is quite tricky, so we
  37 # have hardcoded some well-known objects. See the case statements below for the
  38 # complete list.
  39 pack_obj () {
  40         case "$1" in
  41         # empty blob
  42         e69de29bb2d1d6434b8b29ae775ad8c2e48c5391)
  43                 case "$2" in
  44                 '')
  45                         printf '\060\170\234\003\0\0\0\0\1'
  46                         return
  47                         ;;
  48                 esac
  49                 ;;
  50
  51         # blob containing "\7\76"
  52         e68fe8129b546b101aee9510c5328e7f21ca1d18)
  53                 case "$2" in
  54                 '')
  55                         printf '\062\170\234\143\267\3\0\0\116\0\106'
  56                         return
  57                         ;;
  58                 01d7713666f4de822776c7622c10f1b07de280dc)
  59                         printf '\165\1\327\161\66\146\364\336\202\47\166' &&
  60                         printf '\307\142\54\20\361\260\175\342\200\334\170' &&
  61                         printf '\234\143\142\142\142\267\003\0\0\151\0\114'
  62                         return
  63                         ;;
  64                 esac
  65                 ;;
  66
  67         # blob containing "\7\0"
  68         01d7713666f4de822776c7622c10f1b07de280dc)
  69                 case "$2" in
  70                 '')
  71                         printf '\062\170\234\143\147\0\0\0\20\0\10'
  72                         return
  73                         ;;
  74                 e68fe8129b546b101aee9510c5328e7f21ca1d18)
  75                         printf '\165\346\217\350\22\233\124\153\20\32\356' &&
  76                         printf '\225\20\305\62\216\177\41\312\35\30\170\234' &&
  77                         printf '\143\142\142\142\147\0\0\0\53\0\16'
  78                         return
  79                         ;;
  80                 esac
  81                 ;;
  82         esac
  83
  84         echo >&2 "BUG: don't know how to print $1${2:+ (from $2)}"
  85         return 1
  86 }
  87
  88 # Compute and append pack trailer to "$1"
  89 pack_trailer () {
  90         test-sha1 -b <"$1" >trailer.tmp &&
  91         cat trailer.tmp >>"$1" &&
  92         rm -f trailer.tmp
  93 }
  94
  95 # Remove any existing packs to make sure that
  96 # whatever we index next will be the pack that we
  97 # actually use.
  98 clear_packs () {
  99         rm -f .git/objects/pack/*
 100 }