function must_address() {
	if [[ ! "$1" =~ ^(0x)?[0-9a-fA-F]{40}$ ]]; then
		>&2 echo -e "\033[;31mvalue '$1' for $2 is not an address\033[;39m"
		exit 1	
	fi
}


function must_hash_256() {
	if [[ ! "$1" =~ ^(0x)?[0-9a-fA-F]{64}$ ]]; then
		>&2 echo -e "\033[;31mvalue '$1' for $2 is not a 256-bit digest\033[;39m"
		exit 1	
	fi
}


function must_eth_rpc() {
	if [ -z "${RPC_PROVIDER}" ]; then
		echo "\$RPC_PROVIDER not set!"
		exit 1
	fi
	# Wait for the backend to be up, if we know where it is.
	if [ ! -z "$DEV_USE_DOCKER_WAIT_SCRIPT" ]; then
		WAIT_FOR_TIMEOUT=${WAIT_FOR_TIMEOUT:-60}
		IFS=: read -a p <<< "$RPC_PROVIDER"
		read -i "/" rpc_provider_port <<< "${p[2]}"
		rpc_provider_host=${p[1]:2}
		echo "waiting for provider host $rpc_provider_host port $rpc_provider_port..."
		./wait-for-it.sh "$rpc_provider_host:$rpc_provider_port" -t $WAIT_FOR_TIMEOUT
	fi
}


function clear_pending_tx_hashes() {
	truncate -s 0 $DEV_DATA_DIR/hashes
}


function add_pending_tx_hash() {
	must_hash_256 $1
	echo $1 >> $DEV_DATA_DIR/hashes
}