bacstack/lib/services/i-am-broadcast.js

A BACnet protocol stack written in pure JavaScript.

'use strict';

const baAsn1 = require('../asn1');
const baEnum = require('../enum');

module.exports.encode = (buffer, deviceId, maxApdu, segmentation, vendorId) => {
  baAsn1.encodeApplicationObjectId(buffer, baEnum.ObjectType.DEVICE, deviceId);
  baAsn1.encodeApplicationUnsigned(buffer, maxApdu);
  baAsn1.encodeApplicationEnumerated(buffer, segmentation);
  baAsn1.encodeApplicationUnsigned(buffer, vendorId);
};

module.exports.decode = (buffer, offset) => {
  let result;
  let apduLen = 0;
  const orgOffset = offset;
  result = baAsn1.decodeTagNumberAndValue(buffer, offset + apduLen);
  apduLen += result.len;
  if (result.tagNumber !== baEnum.ApplicationTags.OBJECTIDENTIFIER) return;
  result = baAsn1.decodeObjectId(buffer, offset + apduLen);
  apduLen += result.len;
  if (result.objectType !== baEnum.ObjectType.DEVICE) return;
  const deviceId = result.instance;
  result = baAsn1.decodeTagNumberAndValue(buffer, offset + apduLen);
  apduLen += result.len;
  if (result.tagNumber !== baEnum.ApplicationTags.UNSIGNED_INTEGER) return;
  result = baAsn1.decodeUnsigned(buffer, offset + apduLen, result.value);
  apduLen += result.len;
  const maxApdu = result.value;
  result = baAsn1.decodeTagNumberAndValue(buffer, offset + apduLen);
  apduLen += result.len;
  if (result.tagNumber !== baEnum.ApplicationTags.ENUMERATED) return;
  result = baAsn1.decodeEnumerated(buffer, offset + apduLen, result.value);
  apduLen += result.len;
  if (result.value > baEnum.Segmentation.NO_SEGMENTATION) return;
  const segmentation = result.value;
  result = baAsn1.decodeTagNumberAndValue(buffer, offset + apduLen);
  apduLen += result.len;
  if (result.tagNumber !== baEnum.ApplicationTags.UNSIGNED_INTEGER) return;
  result = baAsn1.decodeUnsigned(buffer, offset + apduLen, result.value);
  apduLen += result.len;
  if (result.value > 0xFFFF) return;
  const vendorId = result.value;
  return {
    len: offset - orgOffset,
    deviceId: deviceId,
    maxApdu: maxApdu,
    segmentation: segmentation,
    vendorId: vendorId
  };
};