chore: bulk-write outgoing CRDT payload across the JS boundary

Explorer/Assets/DCL/Infrastructure/SceneRuntime/Apis/Modules/EngineApi/EngineApiWrapper.cs

@@ -13,15 +13,17 @@ namespace SceneRuntime.Apis.Modules.EngineApi
     public class EngineApiWrapper : JsApiWrapper<IEngineApi>
     {
         private readonly IInstancePoolsProvider instancePoolsProvider;
+        private readonly IJsOperations jsOperations;
         protected readonly ISceneExceptionsHandler exceptionsHandler;
         private readonly SceneRuntimeMetrics metrics;
         private readonly string threadName;
         private PoolableByteArray lastInput = PoolableByteArray.EMPTY;
 
-        public EngineApiWrapper(IEngineApi api, ISceneData sceneData, IInstancePoolsProvider instancePoolsProvider, ISceneExceptionsHandler exceptionsHandler, SceneRuntimeMetrics metrics, CancellationTokenSource disposeCts)
+        public EngineApiWrapper(IEngineApi api, ISceneData sceneData, IInstancePoolsProvider instancePoolsProvider, IJsOperations jsOperations, ISceneExceptionsHandler exceptionsHandler, SceneRuntimeMetrics metrics, CancellationTokenSource disposeCts)
             : base(api, disposeCts)
         {
             this.instancePoolsProvider = instancePoolsProvider;
+            this.jsOperations = jsOperations;
             this.exceptionsHandler = exceptionsHandler;
             this.metrics = metrics;
             threadName = $"CrdtSendToRenderer({sceneData.SceneShortInfo})";
@@ -34,10 +36,10 @@ protected override void DisposeInternal()
         }
 
         [UsedImplicitly]
-        public PoolableByteArray CrdtSendToRenderer(ITypedArray<byte> data)
+        public ITypedArray<byte>? CrdtSendToRenderer(ITypedArray<byte> data)
         {
             if (disposeCts.IsCancellationRequested)
-                return PoolableByteArray.EMPTY;
+                return null;
 
             try
             {
@@ -53,7 +55,7 @@ public PoolableByteArray CrdtSendToRenderer(ITypedArray<byte> data)
 
                 Profiler.EndThreadProfiling();
 
-                return result.IsEmpty ? PoolableByteArray.EMPTY : result;
+                return ToScriptArray(ref result);
             }
             catch (Exception e)
             {
@@ -62,30 +64,50 @@ public PoolableByteArray CrdtSendToRenderer(ITypedArray<byte> data)
                     // Report an uncategorized MANAGED exception (don't propagate it further)
                     exceptionsHandler.OnEngineException(e);
 
-                return PoolableByteArray.EMPTY;
+                return null;
             }
         }
 
         [UsedImplicitly]
-        public PoolableByteArray CrdtGetState()
+        public ITypedArray<byte>? CrdtGetState()
         {
             if (disposeCts.IsCancellationRequested)
-                return PoolableByteArray.EMPTY;
+                return null;
 
             try
             {
                 PoolableByteArray result = api.CrdtGetState();
                 metrics.BytesToScene.Add(result.Length);
-                return result.IsEmpty ? PoolableByteArray.EMPTY : result;
+                return ToScriptArray(ref result);
             }
             catch (Exception e)
             {
                 // Report an uncategorized MANAGED exception (don't propagate it further)
                 exceptionsHandler.OnEngineException(e);
-                return PoolableByteArray.EMPTY;
+                return null;
             }
         }
 
+        /// <summary>
+        ///     Copies the payload into a script-owned Uint8Array in a single bulk write and returns the pooled
+        ///     array deterministically. Previously the <see cref="PoolableByteArray" /> itself was returned to JS:
+        ///     it was consumed through the per-byte fast-proxy enumerator (one host transition per byte in
+        ///     <c>new Uint8Array(...)</c>) and never disposed, so the shared bytes pool never got its arrays back.
+        /// </summary>
+        private ITypedArray<byte>? ToScriptArray(ref PoolableByteArray result)
+        {
+            if (result.IsEmpty)
+            {
+                result.Dispose();
+                return null;
+            }
+
+            ITypedArray<byte> scriptArray = jsOperations.NewUint8Array(result.Length);
+            scriptArray.WriteBytes(result.Array, 0ul, (ulong)result.Length, 0ul);
+            result.Dispose();
+            return scriptArray;
+        }
+
         [UsedImplicitly]
         public virtual PoolableSDKObservableEventArray? SendBatch() => null;
     }

Explorer/Assets/DCL/Infrastructure/SceneRuntime/Apis/Modules/EngineApi/SDKObservableEvents/SDKObservableEventsEngineApiWrapper.cs

@@ -19,10 +19,11 @@ public SDKObservableEventsEngineApiWrapper(ISDKObservableEventsEngineApi api,
             ISceneData sceneData,
             ISDKMessageBusCommsControllerAPI commsApi,
             IInstancePoolsProvider instancePoolsProvider,
+            IJsOperations jsOperations,
             ISceneExceptionsHandler exceptionsHandler,
             SceneRuntimeMetrics metrics,
             CancellationTokenSource disposeCts)
-            : base(api, sceneData, instancePoolsProvider, exceptionsHandler, metrics, disposeCts)
+            : base(api, sceneData, instancePoolsProvider, jsOperations, exceptionsHandler, metrics, disposeCts)
         {
             engineApi = api;
             this.commsApi = commsApi;

Explorer/Assets/DCL/Infrastructure/SceneRuntime/ISceneRuntime.cs

@@ -61,6 +61,12 @@ public interface ISceneRuntime : IDisposable
         void RegisterEngineAPIWrapper(EngineApiWrapper newWrapper);
 
         V8RuntimeHeapInfo RuntimeHeapInfo { get; }
+
+        /// <summary>
+        ///     Script-bound array operations of the underlying engine,
+        ///     required by the API wrappers that marshal binary data back to the scene
+        /// </summary>
+        IJsOperations JsOperations { get; }
     }
 
     public static class SceneRuntimeExtensions
@@ -148,14 +154,14 @@ SceneRuntimeMetrics runtimeMetrics
 
         internal static void RegisterEngineAPI(this ISceneRuntime sceneRuntime, ISceneData sceneData, IEngineApi engineApi, IInstancePoolsProvider instancePoolsProvider, ISceneExceptionsHandler sceneExceptionsHandler, SceneRuntimeMetrics runtimeMetrics)
         {
-            var newWrapper = new EngineApiWrapper(engineApi, sceneData, instancePoolsProvider, sceneExceptionsHandler, runtimeMetrics, sceneRuntime.isDisposingTokenSource);
+            var newWrapper = new EngineApiWrapper(engineApi, sceneData, instancePoolsProvider, sceneRuntime.JsOperations, sceneExceptionsHandler, runtimeMetrics, sceneRuntime.isDisposingTokenSource);
             sceneRuntime.Register("UnityEngineApi", newWrapper);
             sceneRuntime.RegisterEngineAPIWrapper(newWrapper);
         }
 
         internal static void RegisterEngineAPI(this ISceneRuntime sceneRuntime, ISceneData sceneData,  ISDKObservableEventsEngineApi engineApi, ISDKMessageBusCommsControllerAPI commsApiImplementation, IInstancePoolsProvider instancePoolsProvider, ISceneExceptionsHandler sceneExceptionsHandler, SceneRuntimeMetrics runtimeMetrics)
         {
-            var newWrapper = new SDKObservableEventsEngineApiWrapper(engineApi, sceneData, commsApiImplementation, instancePoolsProvider, sceneExceptionsHandler, runtimeMetrics, sceneRuntime.isDisposingTokenSource);
+            var newWrapper = new SDKObservableEventsEngineApiWrapper(engineApi, sceneData, commsApiImplementation, instancePoolsProvider, sceneRuntime.JsOperations, sceneExceptionsHandler, runtimeMetrics, sceneRuntime.isDisposingTokenSource);
             sceneRuntime.Register("UnityEngineApi", newWrapper);
             sceneRuntime.RegisterEngineAPIWrapper(newWrapper);
         }

Explorer/Assets/DCL/Infrastructure/SceneRuntime/SceneRuntimeImpl.cs

@@ -37,6 +37,8 @@ public sealed class SceneRuntimeImpl : ISceneRuntime, IJsOperations
 
         public V8RuntimeHeapInfo RuntimeHeapInfo { get; private set; }
 
+        public IJsOperations JsOperations => this;
+
         CancellationTokenSource ISceneRuntime.isDisposingTokenSource => isDisposingTokenSource;
 
         public SceneRuntimeImpl(

Explorer/Assets/StreamingAssets/Js/Modules/EngineApi.js

@@ -2,9 +2,11 @@
 // https://github.com/decentraland/protocol/blob/main/proto/decentraland/kernel/apis/engine_api.proto
 
 module.exports.crdtSendToRenderer = async function(messages) {
-    const data = new Uint8Array(UnityEngineApi.CrdtSendToRenderer(messages.data))
+    // The returned value is already a Uint8Array created and bulk-filled on the C# side:
+    // wrapping it in `new Uint8Array(...)` would copy it byte by byte through the interop boundary
+    const data = UnityEngineApi.CrdtSendToRenderer(messages.data)
     return {
-        data: [data]
+        data: data ? [data] : []
     };
 }
 
@@ -22,9 +24,9 @@ module.exports.sendBatch = async function() {
 }
 
 module.exports.crdtGetState = async function() {
-    const data = new Uint8Array(UnityEngineApi.CrdtGetState())
+    const data = UnityEngineApi.CrdtGetState()
     return {
-        data: [data],
+        data: data ? [data] : [],
         hasEntities: true //TODO replace with actual value
     };
 }