#!/bin/bash

read_u8() {
  dd if=$1 bs=1 skip=$(( $2 )) count=1 2>/dev/null | od -An -tu1 | grep -Eo '[0-9]+'
}
read_u32() {
  dd if=$1 bs=1 skip=$(( $2 )) count=4 2>/dev/null | od -An -tu4 | grep -Eo '[0-9]+'
}

set -x
setup_size=$(read_u8 $1 0x1f1)
payload_offset=$(read_u32 $1 0x248)
payload_length=$(read_u32 $1 0x24c)
inner_pos=$(( ($setup_size + 1) * 512 ))

tail -c+$(( $inner_pos + 1 )) $1 | tail -c+$(( $payload_offset + 1 )) | head -c $(( $payload_length )) | head -c $(($payload_length - 4)) | unlzma > $2