#! /bin/sh
#

chksum=cksum
quiet=0

while [ $# -gt 0 ]
do
  case "$1" in
  -q )  quiet=1 ; shift ;;
  -c )	case "$2" in
	MD5|md5 ) chksum=md5sum ;;
	CRC|crc|CRC32|crc32 ) chksum=cksum ;;
	SHA1|sha1) chksum=sha1sum ;;
	MD2|md2) chksum=md2sum ;;
	* )	echo "Digest algorithm $2 not supported" >&2 ; exit 1 ;;
	esac
	shift 2
	;;
  -h | --help )
	echo "Usage: $0 [-q] [-c MD5|SHA1|CRC] path ..."
	echo "  -q    do not echo pathname on each line"
	echo "  -c    select digest algorithm (CRC is fastest, SHA1 slowest)"
	echo ""
	echo "  path  root of the tree to digest (mmm, now that's tasty)"
	echo ""
	if [ "$1" = "--help" ]; then
	  echo "  Typical performance numbers, on 2 GHz Pentium 4 for 2.8 GByte"
	  echo "  worth of data in 70 000 files, disk throughput of 30 MByte/s:"
	  echo "    CRC32      2 minutes"
	  echo "    MD5        2'45 minutes"
	  echo "    SHA1       3'15 minutes"
	  echo ""
	fi
	exit 0
	;;
  -- ) 	shift ; break ;;
  -* )	echo "Unknown option $1, exiting" >&2 ; exit 1 ;;
  * )	break ;;
  esac
done

case "$#" in
0 )	echo "Usage: $0 pathname [pathname]" >&2 ;;
* )	;;
esac

die() {
  rc=$1
  shift
  echo "Fatal error: $@" >&2
  exit $rc
}

execexists() {
  path=$1
  which which > /dev/null 2>&1
  if [ $? -ne 0 ]; then 
    echo "Internal error, programme -which- not found" >&2
    exit 1
  fi
  which $path > /dev/null 2>&1
  if [ $? -ne 0 ]; then 
    echo "Selected programme, $path, not found. Sorry." >&2
    exit 1
  fi
}

execexists $chksum

for path in "$@"
do
  showpath=" $path"
  [ $quiet -ne 0 ] && showpath=""
  [ -d $path ] || die 2 "Directory $path not found"
  ( cd $path
    find . -type f | xargs $chksum | $chksum | awk -v p="$showpath" '{printf "%s%s\n",$1,p}'
  )
done