Andrew's git - gitweb.git/blob

   1# Support routines for hand-crafting weird or malicious packs.
   2#
   3# You can make a complete pack like:
   4#
   5#   pack_header 2 >foo.pack &&
   6#   pack_obj e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 >>foo.pack &&
   7#   pack_obj e68fe8129b546b101aee9510c5328e7f21ca1d18 >>foo.pack &&
   8#   pack_trailer foo.pack
   9
  10# Print the big-endian 4-byte octal representation of $1
  11uint32_octal () {
  12        n=$1
  13        printf '\\%o' $(($n / 16777216)); n=$((n % 16777216))
  14        printf '\\%o' $(($n /    65536)); n=$((n %    65536))
  15        printf '\\%o' $(($n /      256)); n=$((n %      256))
  16        printf '\\%o' $(($n           ));
  17}
  18
  19# Print the big-endian 4-byte binary representation of $1
  20uint32_binary () {
  21        printf "$(uint32_octal "$1")"
  22}
  23
  24# Print a pack header, version 2, for a pack with $1 objects
  25pack_header () {
  26        printf 'PACK' &&
  27        printf '\0\0\0\2' &&
  28        uint32_binary "$1"
  29}
  30
  31# Print the pack data for object $1, as a delta against object $2 (or as a full
  32# object if $2 is missing or empty). The output is suitable for including
  33# directly in the packfile, and represents the entirety of the object entry.
  34# Doing this on the fly (especially picking your deltas) is quite tricky, so we
  35# have hardcoded some well-known objects. See the case statements below for the
  36# complete list.
  37pack_obj () {
  38        case "$1" in
  39        # empty blob
  40        e69de29bb2d1d6434b8b29ae775ad8c2e48c5391)
  41                case "$2" in
  42                '')
  43                        printf '\060\170\234\003\0\0\0\0\1'
  44                        return
  45                        ;;
  46                esac
  47                ;;
  48
  49        # blob containing "\7\76"
  50        e68fe8129b546b101aee9510c5328e7f21ca1d18)
  51                case "$2" in
  52                '')
  53                        printf '\062\170\234\143\267\3\0\0\116\0\106'
  54                        return
  55                        ;;
  56                01d7713666f4de822776c7622c10f1b07de280dc)
  57                        printf '\165\1\327\161\66\146\364\336\202\47\166' &&
  58                        printf '\307\142\54\20\361\260\175\342\200\334\170' &&
  59                        printf '\234\143\142\142\142\267\003\0\0\151\0\114'
  60                        return
  61                        ;;
  62                esac
  63                ;;
  64
  65        # blob containing "\7\0"
  66        01d7713666f4de822776c7622c10f1b07de280dc)
  67                case "$2" in
  68                '')
  69                        printf '\062\170\234\143\147\0\0\0\20\0\10'
  70                        return
  71                        ;;
  72                e68fe8129b546b101aee9510c5328e7f21ca1d18)
  73                        printf '\165\346\217\350\22\233\124\153\20\32\356' &&
  74                        printf '\225\20\305\62\216\177\41\312\35\30\170\234' &&
  75                        printf '\143\142\142\142\147\0\0\0\53\0\16'
  76                        return
  77                        ;;
  78                esac
  79                ;;
  80        esac
  81
  82        # If it's not a delta, we can convince pack-objects to generate a pack
  83        # with just our entry, and then strip off the header (12 bytes) and
  84        # trailer (20 bytes).
  85        if test -z "$2"
  86        then
  87                echo "$1" | git pack-objects --stdout >pack_obj.tmp &&
  88                size=$(wc -c <pack_obj.tmp) &&
  89                dd if=pack_obj.tmp bs=1 count=$((size - 20 - 12)) skip=12 &&
  90                rm -f pack_obj.tmp
  91                return
  92        fi
  93
  94        echo >&2 "BUG: don't know how to print $1${2:+ (from $2)}"
  95        return 1
  96}
  97
  98# Compute and append pack trailer to "$1"
  99pack_trailer () {
 100        test-tool sha1 -b <"$1" >trailer.tmp &&
 101        cat trailer.tmp >>"$1" &&
 102        rm -f trailer.tmp
 103}
 104
 105# Remove any existing packs to make sure that
 106# whatever we index next will be the pack that we
 107# actually use.
 108clear_packs () {
 109        rm -f .git/objects/pack/*
 110}