#!/bin/sh

pkg=$1
if [ "$pkg" = "" -o ! -e "$pkg" ]; then
    echo "no package supplied" 1>&2
   exit 1
fi

leadsize=96
o=`expr $leadsize + 8`
set `od -j $o -N 8 -t u1 $pkg`
il=`expr 256 \* \( 256 \* \( 256 \* $2 + $3 \) + $4 \) + $5`
dl=`expr 256 \* \( 256 \* \( 256 \* $6 + $7 \) + $8 \) + $9`
# echo "sig il: $il dl: $dl"

sigsize=`expr 8 + 16 \* $il + $dl`
o=`expr $o + $sigsize + \( 8 - \( $sigsize \% 8 \) \) \% 8 + 8`
set `od -j $o -N 8 -t u1 $pkg`
il=`expr 256 \* \( 256 \* \( 256 \* $2 + $3 \) + $4 \) + $5`
dl=`expr 256 \* \( 256 \* \( 256 \* $6 + $7 \) + $8 \) + $9`
# echo "hdr il: $il dl: $dl"

hdrsize=`expr 8 + 16 \* $il + $dl`
o=`expr $o + $hdrsize`

comp=$(dd if="$pkg" ibs=$o skip=1 count=1 2>/dev/null \
      | dd bs=3 count=1 2> /dev/null)

gz="$(echo -en '\037\0213')"
case "$comp" in
    BZh)      dd if="$pkg" ibs=$o skip=1 2>/dev/null | bunzip2 ;;
    "$gz"*)   dd if="$pkg" ibs=$o skip=1 2>/dev/null | gunzip ;;
    # no magic in old lzma format, if unknown we assume that's lzma for now
    *)        dd if="$pkg" ibs=$o skip=1 2>/dev/null | lzma -dc - ;;
    #*)        echo "Unrecognized rpm file: $pkg"; return 1 ;;
esac
