initial commit

packages/acn/src/index.ts

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+export * from './models';
+export * from './udp';

packages/acn/src/models.ts

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+export type Protocols = {
+  SDT: 1;
+};
+
+export type UDPPreamble = {
+  preambleSize: number;
+  postambleSize: number;
+  packetIdentifier: string;
+};
+
+export type ACNPacket<PreambleType, PDUBlockType, PostambleType> = {
+  preamble: PreambleType;
+  pduBlock: PDUBlockType;
+  postamble: PostambleType;
+};
+
+export type RootLayerPDU = {
+  vector: number;
+  header: Uint8Array;
+  data: Uint8Array;
+};

packages/acn/src/pdu/index.ts

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+import rlp from './rlp';
+export default {
+  rlp,
+};

packages/acn/src/pdu/rlp.ts

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+import { RootLayerPDU } from '../models';
+
+function decode(bytes: Uint8Array): RootLayerPDU {
+  const view = new DataView(bytes.buffer, bytes.byteOffset, bytes.byteLength);
+  const flags = view.getUint8(0) >> 4;
+  const lengthFlag = ((flags >> 3) & 0x1) === 1;
+  const vectorFlag = ((flags >> 2) & 0x1) === 1;
+
+  if (!vectorFlag) {
+    throw new Error('Root Layer PDU must have a vector');
+  }
+
+  const headerFlag = ((flags >> 1) & 0x1) === 1;
+
+  if (!headerFlag) {
+    throw new Error('Root Layer PDU must have a header');
+  }
+
+  const dataFlag = (flags & 0x1) === 1;
+
+  if (!dataFlag) {
+    // TODO(jwetzell): idk know if this is true
+    throw new Error('Root Layer PDU must have data');
+  }
+
+  const lengthH = view.getUint8(0) & 0x0f;
+  let lengthOffset = 1;
+  const lengthL = view.getUint8(lengthOffset);
+
+  let length = (lengthH << 8) + lengthL;
+
+  if (lengthFlag) {
+    lengthOffset += 1;
+    const lengthX = view.getUint8(lengthOffset);
+    length = (lengthH << 16) + (lengthL << 8) + lengthX;
+  }
+  let vectorOffset = lengthOffset + 1;
+
+  if (lengthFlag) {
+    vectorOffset += 1;
+  }
+
+  const vector = view.getUint32(vectorOffset);
+  const headerOffset = vectorOffset + 4;
+
+  const header = bytes.subarray(headerOffset, headerOffset + 16);
+  const dataOffset = headerOffset + 16;
+  // NOTE(jwetzell): flags/lengthH + lengthL + lengthX + vector + header
+  const dataLength = length - (1 + 1 + (lengthFlag ? 1 : 0) + 4 + 16);
+  const data = bytes.subarray(dataOffset, dataOffset + dataLength);
+
+  return {
+    vector,
+    header,
+    data,
+  };
+}
+
+export default {
+  decode,
+};

packages/acn/src/udp.ts

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+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,
+  };
+}