Implement ArrayBuffer.transfer (#1709)

Jint.Tests.Test262/Test262Harness.settings.json

@@ -6,7 +6,6 @@
   "Parallel": true,
   "ExcludedFeatures": [
     "Array.fromAsync",
-    "arraybuffer-transfer",
     "async-iteration",
     "Atomics",
     "generators",

Jint/Native/ArrayBuffer/ArrayBufferPrototype.cs

@@ -36,7 +36,9 @@ internal sealed class ArrayBufferPrototype : Prototype
             ["maxByteLength"] = new GetSetPropertyDescriptor(new ClrFunctionInstance(_engine, "get maxByteLength", MaxByteLength, 0, lengthFlags), Undefined, PropertyFlag.Configurable),
             ["resizable"] = new GetSetPropertyDescriptor(new ClrFunctionInstance(_engine, "get resizable", Resizable, 0, lengthFlags), Undefined, PropertyFlag.Configurable),
             ["resize"] = new PropertyDescriptor(new ClrFunctionInstance(_engine, "resize", Resize, 1, lengthFlags), PropertyFlag.NonEnumerable),
-            ["slice"] = new PropertyDescriptor(new ClrFunctionInstance(_engine, "slice", Slice, 2, lengthFlags), PropertyFlag.NonEnumerable)
+            ["slice"] = new PropertyDescriptor(new ClrFunctionInstance(_engine, "slice", Slice, 2, lengthFlags), PropertyFlag.NonEnumerable),
+            ["transfer"] = new PropertyDescriptor(new ClrFunctionInstance(_engine, "transfer", Transfer, 0, lengthFlags), PropertyFlag.NonEnumerable),
+            ["transferToFixedLength"] = new PropertyDescriptor(new ClrFunctionInstance(_engine, "transferToFixedLength", TransferToFixedLength, 0, lengthFlags), PropertyFlag.NonEnumerable),
         };
         SetProperties(properties);
 
@@ -215,4 +217,71 @@ internal sealed class ArrayBufferPrototype : Prototype
         System.Array.Copy(fromBuf!, first, toBuf!, 0, newLen);
         return bufferInstance;
     }
+
+    /// <summary>
+    /// https://tc39.es/proposal-arraybuffer-transfer/#sec-arraybuffer.prototype.transfer
+    /// </summary>
+    private JsValue Transfer(JsValue thisObject, JsValue[] arguments)
+    {
+        return ArrayBufferCopyAndDetach(thisObject, arguments.At(0), PreserveResizability.PreserveResizability);
+    }
+
+    /// <summary>
+    /// https://tc39.es/proposal-arraybuffer-transfer/#sec-arraybuffer.prototype.transfertofixedlength
+    /// </summary>
+    private JsValue TransferToFixedLength(JsValue thisObject, JsValue[] arguments)
+    {
+        return ArrayBufferCopyAndDetach(thisObject, arguments.At(0), PreserveResizability.FixedLength);
+    }
+
+    private JsValue ArrayBufferCopyAndDetach(JsValue o, JsValue newLength, PreserveResizability preserveResizability)
+    {
+        if (o is not JsArrayBuffer arrayBuffer || arrayBuffer.IsSharedArrayBuffer)
+        {
+            ExceptionHelper.ThrowTypeError(_realm, "Method ArrayBuffer.prototype.ArrayBufferCopyAndDetach called on incompatible receiver " + o);
+            return Undefined;
+        }
+
+        uint newByteLength;
+        if (newLength.IsUndefined())
+        {
+            newByteLength = (uint) arrayBuffer.ArrayBufferByteLength;
+        }
+        else
+        {
+            newByteLength = TypeConverter.ToIndex(_realm, newLength);
+        }
+
+        arrayBuffer.AssertNotDetached();
+
+        uint? newMaxByteLength = null;
+        if (preserveResizability == PreserveResizability.PreserveResizability && arrayBuffer._arrayBufferMaxByteLength != null)
+        {
+            newMaxByteLength = (uint) arrayBuffer._arrayBufferMaxByteLength.Value;
+        }
+
+        if (!arrayBuffer._arrayBufferDetachKey.IsUndefined())
+        {
+            ExceptionHelper.ThrowTypeError(_realm);
+        }
+
+        var newBuffer = _engine.Realm.Intrinsics.ArrayBuffer.AllocateArrayBuffer(_engine.Realm.Intrinsics.ArrayBuffer, newByteLength, newMaxByteLength);
+        var copyLength = System.Math.Min(newByteLength, arrayBuffer.ArrayBufferByteLength);
+        var fromBlock = arrayBuffer.ArrayBufferData!;
+        var toBlock = newBuffer.ArrayBufferData!;
+
+        System.Array.Copy(fromBlock, 0, toBlock, 0, copyLength);
+
+        // NOTE: Neither creation of the new Data Block nor copying from the old Data Block are observable. Implementations may implement this method as a zero-copy move or a realloc.
+
+        arrayBuffer.DetachArrayBuffer();
+
+        return newBuffer;
+    }
+
+    private enum PreserveResizability
+    {
+        PreserveResizability,
+        FixedLength
+    }
 }

Jint/Native/ArrayBuffer/JsArrayBuffer.cs

@@ -15,7 +15,7 @@ public class JsArrayBuffer : ObjectInstance
     internal byte[]? _arrayBufferData;
     internal readonly int? _arrayBufferMaxByteLength;
 
-    private readonly JsValue _arrayBufferDetachKey = Undefined;
+    internal readonly JsValue _arrayBufferDetachKey = Undefined;
 
     internal JsArrayBuffer(
         Engine engine,

README.md

@@ -109,8 +109,9 @@ Following features are supported in version 3.x.
 
 #### ECMAScript Stage 3 (no version yet)
 
+- ✔ `ArrayBuffer.prototype.transfer`
 - ✔ Array Grouping - `Object.groupBy` and `Map.groupBy`
-- ✔ Promise.withResolvers
+- ✔ `Promise.withResolvers`
 - ✔ Resizable and growable ArrayBuffers
 - ✔ ShadowRealm