knxultimate/src/protocol/KNXSecureSearchRequest.ts

KNX IP protocol implementation for Node. This is the ENGINE of Node-Red KNX-Ultimate node.

/**
 * Builds KNX Secure search request frames.
 *
 * Written in Italy with love, sun and passion, by Massimo Saccani.
 *
 * Released under the MIT License.
 * Use at your own risk; the author assumes no liability for damages.
 */

import { KNX_CONSTANTS } from './KNXConstants'
import KNXPacket from './KNXPacket'
import HPAI from './HPAI'

export default class KNXSecureSearchRequest extends KNXPacket {
	hpai: HPAI

	private _srp: Buffer

	constructor(
		hpai: HPAI,
		dibs: number[] = [
			KNX_CONSTANTS.DEVICE_INFO,
			KNX_CONSTANTS.SUPP_SVC_FAMILIES,
			KNX_CONSTANTS.SECURED_SERVICE_FAMILIES,
		],
	) {
		// Actually SEARCH_REQUEST_EXTENDED (0x020B)
		const srpDibs = KNXSecureSearchRequest.buildRequestDibsSRP(dibs)
		const srpSvc = KNXSecureSearchRequest.buildSelectByServiceSRP(
			0x09 /* SECURITY */,
			0x01,
		)
		const srp = Buffer.concat([srpSvc, srpDibs])
		super(KNX_CONSTANTS.SEARCH_REQUEST_EXTENDED, hpai.length + srp.length)
		this.hpai = hpai
		this._srp = srp
	}

	static buildRequestDibsSRP(dibs: number[]): Buffer {
		const payload = Buffer.from(dibs)
		const padded =
			payload.length % 2 === 1
				? Buffer.concat([payload, Buffer.from([0x00])])
				: payload
		const len = 2 + padded.length
		const buf = Buffer.alloc(len)
		let off = 0
		buf.writeUInt8(len, off++)
		// mandatory bit 0, type REQUEST_DIBS (0x04)
		buf.writeUInt8(0x04, off++)
		padded.copy(buf, off)
		return buf
	}

	static buildSelectByServiceSRP(family: number, minVersion: number): Buffer {
		// SRP SELECT_BY_SERVICE: length=4, byte1 flags+type with mandatory=1 and type=0x03
		// data payload: [family, minVersion]
		const len = 2 + 2
		const buf = Buffer.alloc(len)
		buf.writeUInt8(len, 0)
		buf.writeUInt8(0x80 | 0x03, 1) // mandatory bit set | type 0x03
		buf.writeUInt8(family & 0xff, 2)
		buf.writeUInt8(minVersion & 0xff, 3)
		return buf
	}

	static createFromBuffer(
		buffer: Buffer,
		offset: number = 0,
	): KNXSecureSearchRequest {
		if (offset >= buffer.length) {
			throw new Error('Buffer too short')
		}
		const hpai = HPAI.createFromBuffer(buffer, offset)
		return new KNXSecureSearchRequest(hpai)
	}

	toBuffer(): Buffer {
		return Buffer.concat([
			this.header.toBuffer(),
			this.hpai.toBuffer(),
			this._srp,
		])
	}
}