initial commit

packages/free-d/src/utils.ts

@@ -0,0 +1,37 @@
+export function checksum(bytes: Uint8Array): number {
+  let checksum = 0x40;
+
+  bytes.forEach((byte) => {
+    checksum -= byte;
+    if (checksum < 0) {
+      checksum += 256;
+    }
+  });
+  return checksum;
+}
+
+export function rotationToFreeDUnits(rotation: number): Uint8Array {
+  const view = new DataView(new ArrayBuffer(4));
+  const units = rotation * 32768 * 256;
+  view.setInt32(0, units);
+  return new Uint8Array(view.buffer, 0, 3);
+}
+
+export function positionToFreeDUnits(position: number): Uint8Array {
+  const view = new DataView(new ArrayBuffer(4));
+  const units = position * 64 * 256;
+  view.setInt32(0, units);
+  return new Uint8Array(view.buffer, 0, 3);
+}
+
+export function freeDUnitsToRotation(upper: number, middle: number, lower: number): number {
+  const padded = new Uint8Array([upper, middle, lower, 0]);
+  const view = new DataView(padded.buffer, padded.byteOffset, padded.byteLength);
+  return view.getInt32(0) / 256 / 32768;
+}
+
+export function freeDUnitsToPosition(upper: number, middle: number, lower: number): number {
+  const padded = new Uint8Array([upper, middle, lower, 0]);
+  const view = new DataView(padded.buffer, padded.byteOffset, padded.byteLength);
+  return view.getInt32(0) / 256 / 64;
+}