initial commit

packages/acn/src/udp.ts

@@ -0,0 +1,38 @@
+import { ACNPacket, RootLayerPDU, UDPPreamble } from './models';
+import pdu from './pdu';
+
+// ANSI E1.17 - 2015 (R2020) EPI 17
+export function decode(bytes: Uint8Array): ACNPacket<UDPPreamble, RootLayerPDU, undefined> {
+  if (bytes.byteLength < 16) {
+    throw new Error('ACN UDP packet must be at least 16 bytes long');
+  }
+
+  const view = new DataView(bytes.buffer, bytes.byteOffset, bytes.byteLength);
+
+  const preambleSize = view.getUint16(0, false);
+  if (preambleSize != 16) {
+    throw new Error('ACN UDP preamble size should 16');
+  }
+  const postambleSize = view.getUint16(2, false);
+  if (postambleSize > 0) {
+    throw new Error('ACN UDP postamble size should be 0');
+  }
+
+  const packetIdentifier = new TextDecoder().decode(bytes.subarray(4, preambleSize));
+
+  if (packetIdentifier !== 'ASC-E1.17\0\0\0') {
+    throw new Error('ACN Packet Identifier is incorrect');
+  }
+
+  const pduBlock = pdu.rlp.decode(bytes.subarray(preambleSize));
+
+  return {
+    preamble: {
+      preambleSize,
+      postambleSize,
+      packetIdentifier,
+    },
+    pduBlock,
+    postamble: undefined,
+  };
+}