add decoder for centroid position submodule

src/decoders/index.ts

@@ -1,5 +1,7 @@
+import CentroidPosition from './motion/centroid-position';
 import RTTrPHeader from './rttrp';
 
 export const Decoders = {
   RTTrPHeader,
+  CentroidPosition,
 };

src/decoders/motion/centroid-position.ts

@@ -0,0 +1,31 @@
+import { CentroidPosition } from '../../models';
+
+export default (bytes: Uint8Array, isLittleEndian: boolean = false): CentroidPosition => {
+  if (bytes.length !== 29) {
+    throw new Error('Centroid Position module must be 29 bytes');
+  }
+
+  const view = new DataView(bytes.buffer, bytes.byteOffset, bytes.byteLength);
+
+  const type = view.getUint8(0);
+  if (type !== 0x02) {
+    throw new Error('Centroid Position module must have a type of 0x02');
+  }
+
+  const size = view.getUint16(1, isLittleEndian);
+  if (size !== 29) {
+    throw new Error('Centroid Position module must be 29 bytes');
+  }
+  const latency = view.getUint16(3, isLittleEndian);
+  const x = view.getFloat64(5, isLittleEndian);
+  const y = view.getFloat64(13, isLittleEndian);
+  const z = view.getFloat64(21, isLittleEndian);
+  return {
+    type,
+    size,
+    latency,
+    x,
+    y,
+    z,
+  };
+};

src/models.ts

@@ -8,4 +8,14 @@ export type RTTrPHeader = {
   context: number;
   subModuleCount: number;
 };
+
+export type CentroidPosition = {
+  type: number;
+  size: number;
+  latency: number;
+  x: number;
+  y: number;
+  z: number;
+};
+
 };