From 20f58fa0a43da9725e5455501d8e452e3c7dd970 Mon Sep 17 00:00:00 2001
From: scamiv <6170744+scamiv@users.noreply.github.com>
Date: Wed, 25 Feb 2026 22:12:33 +0100
Subject: [PATCH] perf(core): avoid double allocation in packMotionPlans

Rewrite MotionPlans.packMotionPlans to precompute total word count and fill a
single pre-sized Uint32Array with an index pointer (no intermediate number[]).
---
 src/core/game/MotionPlans.ts | 97 +++++++++++++++++++++---------------
 1 file changed, 56 insertions(+), 41 deletions(-)

diff --git a/src/core/game/MotionPlans.ts b/src/core/game/MotionPlans.ts
index ae0e3c292..fbcf0858f 100644
--- a/src/core/game/MotionPlans.ts
+++ b/src/core/game/MotionPlans.ts
@@ -41,68 +41,83 @@ export type MotionPlanRecord = GridPathPlan | TrainRailPathPlan;
 export function packMotionPlans(
   records: readonly MotionPlanRecord[],
 ): Uint32Array {
-  const out: number[] = [MOTION_PLANS_SCHEMA_VERSION, records.length];
-
+  let totalWords = 2;
   for (const record of records) {
     switch (record.kind) {
       case "grid": {
-        const path =
-          record.path instanceof Uint32Array
-            ? record.path
-            : Uint32Array.from(record.path);
+        const pathLen = (record.path.length >>> 0) as number;
+        totalWords += 2 + 5 + pathLen;
+        break;
+      }
+      case "train": {
+        const carCount = (record.carUnitIds.length >>> 0) as number;
+        const pathLen = (record.path.length >>> 0) as number;
+        totalWords += 2 + 7 + carCount + pathLen;
+        break;
+      }
+    }
+  }
+
+  const out = new Uint32Array(totalWords);
+  out[0] = MOTION_PLANS_SCHEMA_VERSION >>> 0;
+  out[1] = records.length >>> 0;
+
+  let offset = 2;
+  for (const record of records) {
+    switch (record.kind) {
+      case "grid": {
+        const path = record.path as ArrayLike<number>;
         const pathLen = path.length >>> 0;
         const wordCount = 2 + 5 + pathLen;
-        out.push(
-          PackedMotionPlanKind.GridPathSet,
-          wordCount,
-          record.unitId >>> 0,
-          record.planId >>> 0,
-          record.startTick >>> 0,
-          record.ticksPerStep >>> 0,
-          pathLen,
-        );
-        for (let i = 0; i < path.length; i++) {
-          out.push(path[i] >>> 0);
+
+        out[offset++] = PackedMotionPlanKind.GridPathSet;
+        out[offset++] = wordCount >>> 0;
+        out[offset++] = record.unitId >>> 0;
+        out[offset++] = record.planId >>> 0;
+        out[offset++] = record.startTick >>> 0;
+        out[offset++] = record.ticksPerStep >>> 0;
+        out[offset++] = pathLen >>> 0;
+
+        for (let i = 0; i < pathLen; i++) {
+          out[offset++] = path[i] >>> 0;
         }
         break;
       }
       case "train": {
-        const carUnitIds =
-          record.carUnitIds instanceof Uint32Array
-            ? record.carUnitIds
-            : Uint32Array.from(record.carUnitIds);
+        const carUnitIds = record.carUnitIds as ArrayLike<number>;
         const carCount = carUnitIds.length >>> 0;
 
-        const path =
-          record.path instanceof Uint32Array
-            ? record.path
-            : Uint32Array.from(record.path);
+        const path = record.path as ArrayLike<number>;
         const pathLen = path.length >>> 0;
 
         const wordCount = 2 + 7 + carCount + pathLen;
-        out.push(
-          PackedMotionPlanKind.TrainRailPathSet,
-          wordCount,
-          record.engineUnitId >>> 0,
-          record.planId >>> 0,
-          record.startTick >>> 0,
-          record.speed >>> 0,
-          record.spacing >>> 0,
-          carCount,
-          pathLen,
-        );
-        for (let i = 0; i < carUnitIds.length; i++) {
-          out.push(carUnitIds[i] >>> 0);
+        out[offset++] = PackedMotionPlanKind.TrainRailPathSet;
+        out[offset++] = wordCount >>> 0;
+        out[offset++] = record.engineUnitId >>> 0;
+        out[offset++] = record.planId >>> 0;
+        out[offset++] = record.startTick >>> 0;
+        out[offset++] = record.speed >>> 0;
+        out[offset++] = record.spacing >>> 0;
+        out[offset++] = carCount >>> 0;
+        out[offset++] = pathLen >>> 0;
+
+        for (let i = 0; i < carCount; i++) {
+          out[offset++] = carUnitIds[i] >>> 0;
         }
-        for (let i = 0; i < path.length; i++) {
-          out.push(path[i] >>> 0);
+        for (let i = 0; i < pathLen; i++) {
+          out[offset++] = path[i] >>> 0;
         }
         break;
       }
     }
   }
 
-  return new Uint32Array(out);
+  if (offset !== out.length) {
+    throw new Error(
+      `packMotionPlans size mismatch: wrote ${offset}, expected ${out.length}`,
+    );
+  }
+  return out;
 }
 
 export function unpackMotionPlans(packed: Uint32Array): {