Add all BENNC message types with unit tests

src/messages/packet.ts

@@ -0,0 +1,55 @@
+import { MAX_DATA_LENGTH } from '../common'
+import { numberToUint16BE } from '../utilities/number'
+import { SmartBuffer } from '../utilities/smart-buffer'
+
+export interface IncomingPacket {
+  messageType: number
+  senderId: number
+  data: Buffer
+}
+
+export interface OutgoingPacket {
+  messageType: Buffer
+  data: Buffer
+}
+
+/**
+ * Create an outgoing packet ready-to-send over a WebSocket in line with the BENNC basic message strucure specification.
+ * @param outgoingPacket The message type and data to send.
+ * @returns A buffer containing the ready-to-send packet.
+ */
+export function packOutgoingPacket (outgoingPacket: OutgoingPacket): Buffer {
+  // Verify that the data does not exceed the maximum data length.
+  if (outgoingPacket.data.length > MAX_DATA_LENGTH) {
+    throw RangeError(`Specified data of length ${outgoingPacket.data.length} exceeds max data length ${MAX_DATA_LENGTH}.`)
+  }
+
+  // Prepare the outgoing packet.
+  const buffer = Buffer.concat([
+    outgoingPacket.messageType,
+    numberToUint16BE(outgoingPacket.data.length),
+    outgoingPacket.data
+  ])
+
+  return buffer
+}
+
+/**
+ * Unpack an incoming packet coming from a WebSocket in line with the BENNC basic message strucure specification.
+ * @param incomingPacket The incoming buffer from a WebSocket to unpack.
+ * @returns The unpacked data.
+ */
+export function unpackIncomingPacket (incomingPacket: ArrayBuffer): IncomingPacket {
+  const buffer = SmartBuffer.from(incomingPacket)
+
+  const messageType = buffer.readUInt16()
+  const senderId = buffer.readUInt32()
+  const length = buffer.readUInt16()
+  const data = buffer.readBytes(length)
+
+  return {
+    messageType: messageType,
+    senderId: senderId,
+    data: data
+  }
+}