#!/bin/sh

read32()
{
	dd if=kernel bs=1 skip=$((0x$1)) count=4 2> /dev/null | \
		hexdump -e '"" 1/4 "%d" "\n"'
}

case "$1" in
extract)
	dd bs=512 count=2 > kernel 2> /dev/null
	setupsz=$(($(read32 1F1) & 255))
	dd bs=512 count=$(($setupsz - 1)) >> kernel 2> /dev/null
	[ $(read32 228) -ne 0 ] &&
	dd bs=512 count=1 2> /dev/null | strings > cmdline
	syssz=$(read32 1F4)
	syssz=$(( ($syssz + 31) / 32 ))
	dd bs=512 count=$syssz >> kernel 2> /dev/null
	ramsz=$(read32 21C)
	dd bs=512 count=$((($ramsz + 511) / 512)) of=rootfs 2> /dev/null
	dd bs=1 seek=$ramsz count=0 of=rootfs 2> /dev/null
	;;
*)	cat <<EOT
usage: 
# cat fd0*.img | $0 extract
	creates kernel, rootfs and cmdline files
# cat fd1*.img | unlzma | cpio -i
# cat fd2*.img | unlzma | cpio -i
...
EOT
esac