Method constructor

modules/crypt/etc/hmac.js:41–45

(h, key, bitlen = 0)

export default class HMAC {
	constructor(h, key, bitlen = 0) {
		this.h = h;
		this.init(key);
		this.hashLen = bitlen >> 3;	// in byte
	};
	init(key) {
		const h = this.h;
		if (key.byteLength > h.blockSize) {