#!/bin/bash

set -ex

INPUT=$1
OUTPUT=$2
SIZE=$3
BUF=$4

COMMON_DIR=$(dirname $(readlink -f $0))
ROCKIMG_DIR=${COMMON_DIR}/../rockimg

if [ ! -e ${INPUT} ]; then
	echo "ERROR: No input file \"${INPUT}\""
	exit -1
fi

rm ${ROCKIMG_DIR}/${OUTPUT} || true

if [ ${SIZE} -gt 1024 ]; then
	echo "ERROR: SIZE bigger than 1K"
	exit -1
fi

BIG_END=$[SIZE / 256]
LIT_END=$[SIZE - (BIG_END * 256)]
BIG_END=$(echo "ibase=10;obase=16;${BIG_END}" | bc)
LIT_END=$(echo "ibase=10;obase=16;${LIT_END}" | bc)

dd if=${INPUT} of=${OUTPUT} bs=1k count=10
echo -en "\x${LIT_END}\x${BIG_END}" >> ${OUTPUT}
echo -n "$BUF" >> ${OUTPUT}
SKIP=$[10 * 1024 + SIZE + 2]
dd if=${INPUT} of=${OUTPUT} seek=${SKIP} skip=${SKIP} bs=1