#!/bin/bash
#Copyright 2002, William Stearns <wstearns@pobox.com>
#Released under the GPL.
Version=0.1

askYN () {
	TESTYN=""
	while [ "$TESTYN" != 'Y' ] && [ "$TESTYN" != 'N' ] ; do
		echo -n '?' >/dev/stderr
		read TESTYN || :
		case $TESTYN in
		T*|t*|Y*|y*)            TESTYN='Y'      ;;
		F*|f*|N*|n*)            TESTYN='N'      ;;
		esac
	done

	if [ "$TESTYN" = 'Y' ]; then
		return 0 #True
	else
		return 1 #False
	fi
} #End of askYN
																						
usage () {
	echo "$0 Version $Version: Enlarges a filesystem that is stored in a file, as opposed" >>/dev/stderr
	echo 'to a partition.' >>/dev/stderr
	echo 'Usage:' >>/dev/stderr
	echo "	$0 filesystemfile newsize" >>/dev/stderr
	echo 'Example:' >>/dev/stderr
	echo "	$0 root_fs 750" >>/dev/stderr
	echo '' >>/dev/stderr
	echo 'The new size must be in megabytes and must be at least 2.' >>/dev/stderr
	exit 1
}

fail () {
	echo "$* Exiting." >>/dev/stderr
	exit 1
}

for OneUtil in awk cp dd e2fsck file ls mktemp resize2fs rm ; do
	type -path "$OneUtil" >/dev/null 2>/dev/null || fail Missing utility "$OneUtil"
done

#FIXME - check to see if file is in use before starting
#FIXME - remind user to run cow first, if needed.
#FIXME - check free space against size of root_fs + requested space

FsFile="${1}"
[ -n "$FsFile" ] || usage
[ -f "$FsFile" ] || fail No file named \""$FsFile"\".
NewMegs=${2}
[ -n "$NewMegs" ] || usage
case "$NewMegs" in
#  2         10             100             1000         2000     2040
#  9         99             999             1999         2039     2047
[2-9]|[1-9][0-9]|[1-9][0-9][0-9]|1[0-9][0-9][0-9]|20[0-3][0-9]|204[0-7])
	:
	;;
# 2048         2050             2100                 3000
# 2049         2099             2999                 9999
204[89]|20[5-9][0-9]|2[1-9][0-9][0-9]|[3-9][0-9][0-9][0-9])
	#Bash ints overflow at 2047 * 1M.
	fail New sizes larger than 2047 are not supported at the moment.
	;;
*)
	fail The new size you specify must be a number of megabytes between 2 and 2047.
	;;
esac

case `file "$FsFile"` in
*:\ Linux\ rev\ 1.0\ ext2\ filesystem\ data|*:\ Linux\ rev\ 1.0\ ext3\ filesystem\ data)
	:
	;;
*:\ ASCII\ text,\ with\ no\ line\ terminators)
	fail Reiserfs not supported in this version.
	;;
*)
	fail Unrecognized filesystem type `file "$FsFile"`
	;;
esac

TMPFILE=`mktemp "$FsFile.XXXXXX"` || fail Unable to create temporary file.

CurFileSize=`ls -al "$FsFile" | awk '{print $5}'`
NewFileSize=$[ $NewMegs * 1048576 ]
echo Requested: $NewFileSize , Currently: $CurFileSize

if [ $NewFileSize -eq $CurFileSize ]; then
	echo Requested size equals current size.
	cp -p --sparse=always $FsFile $TMPFILE
	resize2fs -p $TMPFILE || fail Resize2fs failed.
elif [ $NewFileSize -lt $CurFileSize ]; then
	echo Requested size is less than current size.
	TMPFILE2=`mktemp "$FsFile.XXXXXX"` || fail Unable to create temporary file.
	cp -p --sparse=always $FsFile $TMPFILE2
	resize2fs -p $TMPFILE2 $[ $NewMegs * 256 ] || fail Resize2fs failed.
	#FIXME - "perl -e open/truncate/close" if perl is available.
	cp -p --sparse=always <( dd bs=1048576 if=$TMPFILE2 count=$NewMegs ) $TMPFILE
	rm -f $TMPFILE2
elif [ $NewFileSize -gt $CurFileSize ]; then
	echo Requested size is larger than current size.
	#if new-cur > mem, the following dd fails with memory exhausted.
	# dd bs=$[ $NewFileSize - $CurFileSize ] count=1 if=/dev/zero
	#I've broken up the above dd if=/dev/zero into:
	#copy megabyte sized chunks of 0x0 bytes.
	#copy the remaining (<1M) bytes as a single block.
	cp -p --sparse=always <( \
	 dd bs=1048576 if=$FsFile ; \
	 if [ $[ $NewFileSize - $CurFileSize ] -ge 1048576 ]; then \
		 dd bs=1048576 count=$[ ( $NewFileSize - $CurFileSize ) / 1048576 ] if=/dev/zero ; \
	 fi ; \
	 if [ $[ $NewFileSize - $CurFileSize - ( ( ($NewFileSize - $CurFileSize) / 1048576 ) * 1048576 ) ] -gt 0 ]; then \
		 dd bs=$[ $NewFileSize - $CurFileSize - ( ( ($NewFileSize - $CurFileSize) / 1048576 )  * 1048576 ) ] count=1 if=/dev/zero ; \
	 fi \
	 ) $TMPFILE
	resize2fs -p $TMPFILE $[ $NewMegs * 256 ] || fail Resize2fs failed.
fi

[ $NewFileSize -eq `ls -al "$TMPFILE" | awk '{print $5}'` ] || fail $TMPFILE is not $NewFileSize bytes long.

#Copy back if e2fsck says OK.
if e2fsck -f $TMPFILE ; then
	echo Filesystem check of $TMPFILE passed.
	if echo -n "Would you like to replace the $FsFile" ; askYN ; then
		echo Resize OK, moving file back to $FsFile
		rm -f $FsFile
		cp -p --sparse=always $TMPFILE $FsFile
		rm -f $TMPFILE
	else
		echo Not replacing $FsFile.  You may wish to delete $TMPFILE.
	fi
else
	echo Filesystem check of $TMPFILE failed - not replacing $FsFile .
	if echo -n "Would you like to delete the $TMPFILE" ; askYN ; then
		rm -f $TMPFILE
	else
		echo Not removing $TMPFILE
	fi
fi