#/bin/sh
#
# Extract the files from MTD partition UserDef (/dev/mtdblock1) that were
# assembled with collect.
#
# Each file consists of
#
#   4 bytes:    file size S (little endian)
#   S bytes:    file data
#   1 byte:     length L of the file name
#   1 byte:     '=' (ignored)
#   L bytes:    file name
#   0..3 bytes: padding (with 0) to get a 32-bit alignment for the next size
#
# The sequence ends if a file size of 0 is found.
#
# Remark:
# If the size is 0xFFFFFFFF, then the script stops, too. This is typically an
# empty UserDef.

TEMP=/tmp/spread.tmp

# Convert binary data (1-4 bytes) coming in on stdin to eight hex digits
tohex()
{
    hexdump -e \"%08x\"
}

# Copy part of file $TEMP to stdout
# $1: Offset
# $2: Length
extract()
{
    tail -c +$(($1 + 1)) $TEMP | head -c $2
}

# Go to target directory
cd /root
echo "Restore configuration files to $(pwd)"

# Copy UserDef into a file so that we can access it easier
cp /dev/mtdblock1 $TEMP
offset=0
count=0

# Extract the files
while
    size=$(extract $offset 4 | tohex)
    [ $size != FFFFFFFF ] && [ $size != 00000000 ]
do
    size=$((0x$size))
    len=$((0x$(extract $(($offset + 4 + $size)) 1 | tohex)))
    fname=$(extract $(($offset + 4 + $size + 2)) $len)
    echo "Found '$fname' with size $size"
    extract $(($offset + 4)) $size > $fname
    offset=$(($offset + 4 + $size + 2 + $len))
    offset=$((($offset + 3) & ~3))
    count=$(($count + 1))
done

# Remove the temporary file again
rm $TEMP

# Rename this script so that it is not executed again on next start.
# Attention: This is only possible if the rootfs is mounted read/write.
mv /etc/init.d/S01restoreconfig /etc/init.d/done-S01restoreconfig

echo "Restoring configuration done, found $count file(s)"