dnp3/src/Datagram/index.js

A DNP 3.0 library for Node.js

let crc = require('dnp3-crc')

let Datagram = module.exports = function (options) {
  this.len = 0x05
  this.linkControl = 0x00
  this._dlcDir = 0
  this._dlcPrm = 0
  this._dlcFcb = 0
  this._dlcFcvDfc = 0
  this._dlcFc = 0
  this.dstAddr = options.dstAddr || 0x00
  this.srcAddr = options.srcAddr || 0x00
}

Datagram.prototype.setDlcDir = function (dir) {
  this._dlcDir = dir ? 1 : 0
  return this
}
Datagram.prototype.setDlcPrm = function (prm) {
  this._dlcPrm = prm ? 1 : 0
  return this
}
Datagram.prototype.setDlcFcb = function (fcb) {
  this._dlcFcb = fcb ? 1 : 0
  return this
}
Datagram.prototype.setDlcFcvDfc = function (fcvDfc) {
  this._dlcFcvDfc = fcvDfc ? 1 : 0
  return this
}
Datagram.prototype.setDlcFc = function (fc) {
  this._dlcFc = fc & 0x0F
  return this
}

Datagram.prototype.updateDlc = function () {
  let dlc = 0x00
  dlc = this._dlcDir << 7 | this._dlcPrm << 6 |
           this._dlcFcb << 5 | this._dlcFcvDfc << 4 |
           this._dlcFc
  this.linkControl = dlc
  return this
}

Datagram.prototype.build = function () {
  let blocks = this._blocks = []
  let _crc

  // BLOCK 0
  let block0 = []
  // start
  block0.push(0x05)
  block0.push(0x64)
  // len
  block0.push(this.len)
  // lc
  this.updateDlc()
  block0.push(this.linkControl)
  // dst
  block0.push(this.dstAddr & 0xFF)
  block0.push((this.dstAddr & 0xFF00) >> 8)
  // src
  block0.push(this.srcAddr & 0xFF)
  block0.push((this.srcAddr & 0xFF00) >> 8)

  // crc
  _crc = crc.calculate(block0)
  block0.push(_crc & 0xFF)
  block0.push((_crc & 0xFF00) >> 8)
  // Add it to the block list
  blocks.push(block0)

  // BLOCK N
  // TODO: Packet UserData

  let bytes = []
  // Merge blocks into a single array
  blocks.forEach(function (block) {
    Array.prototype.push.apply(bytes, block)
  })

  return Buffer.alloc(bytes, 0)
}