ubxsum.js

// Tool for adding checksum and header (if missing) to uBlox UBX message.
// by Martin Ždila <[email protected]>
// License: CC0

const arg = process.argv[2];
if (!arg) {
	console.error(`Usage: process.argv[0] process.argv[1] AABBCCDD...`);
	process.exit(1);
}

const res = /^(b562)?(([0-9a-f]{2}){4,})$/i.exec(arg);
if (!res) {
	console.error(`Invalid input. Use hexadecimal string, eg. 02010000`);
	process.exit(1);
}

console.log(
	// credits https://blog.tompawlak.org/split-string-tokens-defined-length-javascript
	'b562' + res[2] + res[2].match(/.{1,2}(?=(.{2})+(?!.))|.{1,2}$/g)
		.map(x => parseInt(x, 16))
		.reduce(([a, b], x) => ([a + x, b + a + x]), [0, 0]).map(n => (n % 256).toString(16).padStart(2, '0'))
		.join('')
)