add encoder for trackable sub module

src/encoders/index.ts

@@ -1,7 +1,9 @@
 import RTTrPM from './motion/rttrpm';
+import Trackable from './motion/trackable';
 import RTTrPHeader from './rttrp-header';
 
 export const Encoders = {
   RTTrPHeader,
   RTTrPM,
+  Trackable,
 };

src/encoders/motion/trackable.ts

@@ -0,0 +1,47 @@
+const textEncoder = new TextEncoder();
+
+export default (
+  name: string,
+  subModules: Uint8Array[],
+  timestamp?: number,
+  isLittleEndian: boolean = false
+): Uint8Array => {
+  let totalTrackableSize = 1 + 2 + 1 + name.length + 1;
+  let type = 0x01;
+  if (timestamp !== undefined) {
+    totalTrackableSize += 4;
+    type = 0x51;
+  }
+  subModules.forEach((subModule) => {
+    totalTrackableSize += subModule.length;
+  });
+  const bytes = new Uint8Array(totalTrackableSize);
+  const view = new DataView(bytes.buffer, bytes.byteOffset, bytes.byteLength);
+
+  let dataOffset = 0;
+  view.setUint8(dataOffset, type);
+  dataOffset += 1;
+  view.setUint16(dataOffset, totalTrackableSize, isLittleEndian);
+  dataOffset += 2;
+  const nameBytes = textEncoder.encode(name);
+  view.setUint8(dataOffset, nameBytes.length);
+  dataOffset += 1;
+
+  nameBytes.forEach((byte) => {
+    view.setUint8(dataOffset, byte);
+    dataOffset += 1;
+  });
+
+  if (timestamp !== undefined) {
+    view.setUint32(dataOffset, timestamp, isLittleEndian);
+    dataOffset += 4;
+  }
+
+  view.setUint8(dataOffset, subModules.length);
+  dataOffset += 1;
+  subModules.forEach((subModule) => {
+    bytes.set(subModule, dataOffset);
+    dataOffset += subModule.length;
+  });
+  return new Uint8Array(view.buffer, view.byteOffset, view.byteLength);
+};