[dart2js/ddc/dart2wasm/dart:js_interop] Support SharedArrayBuffers in JS typed data wrappers

#56455

The existing native typed data implementation in dart2js/ddc
and the JS typed data wrappers in dart2wasm do not support
SharedArrayBuffers.

In dart2js/ddc, this is because the native type for ByteBuffer
is simply ArrayBuffer, leading to type failures when using
SharedArrayBuffers. To handle this, this change makes NativeByteBuffer
an abstract parent class to NativeArrayBuffer and NativeSharedArrayBuffer.
This allows ByteBuffer to support both types. There is a preexisting
SharedArrayBuffer type in dart:html that we should avoid breaking, so
we add an interface that NativeSharedArrayBuffer implements and expose
that interface.

In dart2wasm, JSArrayBufferImpl only allows ArrayBuffers as its
extern ref. This change makes that wrapper support SharedArrayBuffers
as well.

In dart:js_interop, the existing toJS conversion on ByteBuffer
now throws if the underlying buffer was actually a SharedArrayBuffer.
This is to support the return type of JSArrayBuffer. This behavior
technically already existed due to type differences in the JS
compilers, but was never possible with dart2wasm.

CoreLibraryReviewExempt: Backend-specific libraries with no real functional changes to public APIs.
Change-Id: I4dac9fb808590bf0c274da815c152cd4637316b1
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/437526
Reviewed-by: Stephen Adams <[email protected]>
Commit-Queue: Srujan Gaddam <[email protected]>

Author: srujzs

pkg/compiler/lib/src/js_backend/native_data.dart

@@ -1064,7 +1064,9 @@ class NativeClassTag {
 
   factory NativeClassTag(String tagText) {
     List<String> tags = tagText.split(',');
-    List<String> names = tags.where((s) => !s.startsWith('!')).toList();
+    List<String> names = tags
+        .where((s) => s.isNotEmpty && !s.startsWith('!'))
+        .toList();
     bool isNonLeaf = tags.contains('!nonleaf');
     return NativeClassTag.internal(names, isNonLeaf);
   }

sdk/lib/_internal/js_dev_runtime/private/native_typed_data.dart

@@ -23,10 +23,9 @@ import 'dart:math' as Math;
 
 import 'dart:typed_data';
 
-@Native('ArrayBuffer')
-final class NativeByteBuffer extends JavaScriptObject implements ByteBuffer {
-  @JSName('byteLength')
-  external int get lengthInBytes;
+abstract final class NativeByteBuffer extends JavaScriptObject
+    implements ByteBuffer {
+  int get lengthInBytes => JS('', '#.byteLength', this);
 
   Type get runtimeType => ByteBuffer;
 
@@ -97,6 +96,45 @@ final class NativeByteBuffer extends JavaScriptObject implements ByteBuffer {
   }
 }
 
+@Native('ArrayBuffer')
+final class NativeArrayBuffer extends NativeByteBuffer {}
+
+// Interface class that's exposed through `dart:html` to replace the previous
+// `@Native` `SharedArrayBuffer` class that existed there. Marked as `interface`
+// so that classes that implemented it before from `dart:html` still work.
+abstract interface class SharedArrayBuffer extends JavaScriptObject {
+  factory SharedArrayBuffer([int? length]) {
+    if (length != null) {
+      return NativeSharedArrayBuffer._create1(length);
+    }
+    return NativeSharedArrayBuffer._create2();
+  }
+
+  int? get byteLength;
+
+  SharedArrayBuffer slice([int? begin, int? end]);
+}
+
+@Native('SharedArrayBuffer')
+final class NativeSharedArrayBuffer extends NativeByteBuffer
+    implements SharedArrayBuffer {
+  static NativeSharedArrayBuffer _create1(int length) => JS(
+    'returns:NativeSharedArrayBuffer;effects:none;depends:none;new:true',
+    'new SharedArrayBuffer(#)',
+    length,
+  );
+  static NativeSharedArrayBuffer _create2() => JS(
+    'returns:NativeSharedArrayBuffer;effects:none;depends:none;new:true',
+    'new SharedArrayBuffer()',
+  );
+
+  @override
+  int? get byteLength native;
+
+  @override
+  SharedArrayBuffer slice([int? begin, int? end]) native;
+}
+
 /// A fixed-length list of Float32x4 numbers that is viewable as a
 /// [TypedData]. For long lists, this implementation will be considerably more
 /// space- and time-efficient than the default [List] implementation.

sdk/lib/_internal/js_runtime/lib/native_typed_data.dart

@@ -30,11 +30,14 @@ import 'dart:math' as Math;
 
 import 'dart:typed_data';
 
-@Native('ArrayBuffer')
-final class NativeByteBuffer extends JavaScriptObject
+// An empty `@Native` annotation allows this type to be treated as a native type
+// but without a corresponding value. dart2js only treats classes as native if
+// they contain this annotation or a parent class is native. This works around
+// that limitation.
+@Native('')
+abstract final class NativeByteBuffer extends JavaScriptObject
     implements ByteBuffer, TrustedGetRuntimeType {
-  @JSName('byteLength')
-  int get lengthInBytes native;
+  int get lengthInBytes => JS('', '#.byteLength', this);
 
   Type get runtimeType => ByteBuffer;
 
@@ -108,6 +111,45 @@ final class NativeByteBuffer extends JavaScriptObject
   }
 }
 
+@Native('ArrayBuffer')
+final class NativeArrayBuffer extends NativeByteBuffer {}
+
+// Interface class that's exposed through `dart:html` to replace the previous
+// `@Native` `SharedArrayBuffer` class that existed there. Marked as `interface`
+// so that classes that implemented it before from `dart:html` still work.
+abstract interface class SharedArrayBuffer extends JavaScriptObject {
+  factory SharedArrayBuffer([int? length]) {
+    if (length != null) {
+      return NativeSharedArrayBuffer._create1(length);
+    }
+    return NativeSharedArrayBuffer._create2();
+  }
+
+  int? get byteLength;
+
+  SharedArrayBuffer slice([int? begin, int? end]);
+}
+
+@Native('SharedArrayBuffer')
+final class NativeSharedArrayBuffer extends NativeByteBuffer
+    implements SharedArrayBuffer {
+  static NativeSharedArrayBuffer _create1(int length) => JS(
+    'returns:NativeSharedArrayBuffer;effects:none;depends:none;new:true',
+    'new SharedArrayBuffer(#)',
+    length,
+  );
+  static NativeSharedArrayBuffer _create2() => JS(
+    'returns:NativeSharedArrayBuffer;effects:none;depends:none;new:true',
+    'new SharedArrayBuffer()',
+  );
+
+  @override
+  int? get byteLength native;
+
+  @override
+  SharedArrayBuffer slice([int? begin, int? end]) native;
+}
+
 /// A fixed-length list of Float32x4 numbers that is viewable as a
 /// [TypedData]. For long lists, this implementation will be considerably more
 /// space- and time-efficient than the default [List] implementation.

sdk/lib/_internal/js_shared/lib/js_types.dart

@@ -28,7 +28,7 @@ typedef JSArrayRepType = interceptors.JSArray<Object?>;
 
 typedef JSBoxedDartObjectRepType = interceptors.JSObject;
 
-typedef JSArrayBufferRepType = typed_data.NativeByteBuffer;
+typedef JSArrayBufferRepType = typed_data.NativeArrayBuffer;
 
 typedef JSDataViewRepType = typed_data.NativeByteData;
 

sdk/lib/_internal/wasm/lib/js_helper.dart

@@ -426,7 +426,7 @@ bool isWasmGCStruct(WasmExternRef? ref) => ref.internalize()?.isObject ?? false;
 /// The values within this class should correspond to the values returned by
 /// [externRefType] and should be updated if that function is updated. Constants
 /// are preferred over enums for performance.
-class ExternRefType {
+abstract final class ExternRefType {
   static const int null_ = 0;
   static const int undefined = 1;
   static const int boolean = 2;
@@ -444,7 +444,8 @@ class ExternRefType {
   static const int float64Array = 14;
   static const int dataView = 15;
   static const int arrayBuffer = 16;
-  static const int unknown = 17;
+  static const int sharedArrayBuffer = 17;
+  static const int unknown = 18;
 }
 
 /// Returns an integer representing the type of [ref] that corresponds to one of
@@ -475,7 +476,12 @@ int externRefType(WasmExternRef? ref) {
       if (o instanceof DataView) return 15;
     }
     if (o instanceof ArrayBuffer) return 16;
-    return 17;
+    // Feature check for `SharedArrayBuffer` before doing a type-check.
+    if (globalThis.SharedArrayBuffer !== undefined &&
+        o instanceof SharedArrayBuffer) {
+        return 17;
+    }
+    return 18;
   }
   ''', ref).toIntUnsigned();
   return val;
@@ -513,9 +519,8 @@ Object? dartifyRaw(WasmExternRef? ref, [int? refType]) {
     ExternRefType.float64Array => js_types.JSFloat64ArrayImpl.fromRefUnchecked(
       ref,
     ),
-    ExternRefType.arrayBuffer => js_types.JSArrayBufferImpl.fromRefUnchecked(
-      ref,
-    ),
+    ExternRefType.arrayBuffer || ExternRefType.sharedArrayBuffer =>
+      js_types.JSArrayBufferImpl.fromRefUnchecked(ref),
     ExternRefType.dataView => js_types.JSDataViewImpl.fromRefUnchecked(ref),
     ExternRefType.unknown =>
       isJSWrappedDartFunction(ref)

sdk/lib/_internal/wasm/lib/js_interop_patch.dart

@@ -241,13 +241,19 @@ extension ByteBufferToJSArrayBuffer on ByteBuffer {
   @patch
   JSArrayBuffer get toJS {
     final t = this;
-    return JSArrayBuffer._(
-      JSValue(
-        t is js_types.JSArrayBufferImpl
-            ? t.toExternRef
-            : jsArrayBufferFromDartByteBuffer(t),
-      ),
-    );
+    if (t is js_types.JSArrayBufferImpl) {
+      if (!t.isArrayBuffer) {
+        assert(t.isSharedArrayBuffer);
+        throw StateError(
+          "ByteBuffer is a wrapped 'SharedArrayBuffer'. Convert the typed list "
+          "that wrapped this buffer to a JS typed array instead to access the "
+          "`SharedArrayBuffer` from that JS typed array.",
+        );
+      }
+      return JSArrayBuffer._(JSValue(t.toExternRef));
+    } else {
+      return JSArrayBuffer._(JSValue(jsArrayBufferFromDartByteBuffer(t)));
+    }
   }
 }
 

sdk/lib/_internal/wasm/lib/js_typed_array.dart

@@ -4,24 +4,50 @@
 
 part of dart._js_types;
 
-/// A JS `ArrayBuffer`.
+/// Container class for constants that represent the possible types of a
+/// [WasmExternRef] that can be passed to [JSArrayBufferImpl].
+///
+/// Constants are preferred over enums for performance.
+abstract final class _ArrayBufferType {
+  static const int arrayBuffer = 0;
+  static const int sharedArrayBuffer = 1;
+  static const int unknown = 2;
+}
+
+/// A JS `ArrayBuffer` or `SharedArrayBuffer`.
 final class JSArrayBufferImpl implements ByteBuffer {
-  /// `externref` of a JS `ArrayBuffer`.
+  /// `externref` of a JS `ArrayBuffer` or `SharedArrayBuffer`.
   final WasmExternRef? _ref;
 
   final bool _immutable;
 
-  static bool _checkRefType(WasmExternRef? ref) =>
-      js.JS<bool>('o => o instanceof ArrayBuffer', ref);
+  late int _refType = _getRefType(_ref);
+
+  static int _getRefType(WasmExternRef? _ref) =>
+      // Feature check for `SharedArrayBuffer` before doing a type-check.
+      js.JS<WasmI32>('''o => {
+          if (o instanceof ArrayBuffer) return 0;
+          if (globalThis.SharedArrayBuffer !== undefined &&
+              o instanceof SharedArrayBuffer) {
+            return 1;
+          }
+          return 2;
+        }''', _ref).toIntUnsigned();
+
+  bool get isArrayBuffer => _refType == _ArrayBufferType.arrayBuffer;
+
+  bool get isSharedArrayBuffer =>
+      _refType == _ArrayBufferType.sharedArrayBuffer;
 
   JSArrayBufferImpl.fromRefUnchecked(this._ref) : _immutable = false {
-    assert(_checkRefType(_ref));
+    assert(isArrayBuffer || isSharedArrayBuffer);
   }
 
   JSArrayBufferImpl.fromRefImmutableUnchecked(this._ref) : _immutable = true;
 
   factory JSArrayBufferImpl.fromRef(WasmExternRef? ref) {
-    if (!_checkRefType(ref)) {
+    final refType = _getRefType(ref);
+    if (refType == _ArrayBufferType.unknown) {
       return _throwConversionFailureError("ByteBuffer");
     }
     return JSArrayBufferImpl.fromRefUnchecked(ref);
@@ -30,9 +56,13 @@ final class JSArrayBufferImpl implements ByteBuffer {
   @pragma("wasm:prefer-inline")
   WasmExternRef? get toExternRef => _ref;
 
-  /// Get a JS `DataView` of this `ArrayBuffer`.
+  /// Get a JS `DataView` of this `ArrayBuffer` or `SharedArrayBuffer`.
   WasmExternRef? view(int offsetInBytes, int? length) =>
-      _newDataViewFromArrayBuffer(toExternRef, offsetInBytes, length);
+      _newDataViewFromArrayBufferOrSharedArrayBuffer(
+        toExternRef,
+        offsetInBytes,
+        length,
+      );
 
   WasmExternRef? cloneAsDataView(int offsetInBytes, int? lengthInBytes) {
     lengthInBytes ??= this.lengthInBytes;
@@ -279,7 +309,11 @@ final class JSDataViewImpl implements ByteData {
     int offsetInBytes,
     int? length,
   ) => JSDataViewImpl.fromRefUnchecked(
-    _newDataViewFromArrayBuffer(buffer.toExternRef, offsetInBytes, length),
+    _newDataViewFromArrayBufferOrSharedArrayBuffer(
+      buffer.toExternRef,
+      offsetInBytes,
+      length,
+    ),
   );
 
   @pragma("wasm:prefer-inline")
@@ -2601,7 +2635,7 @@ int _dataViewByteLength(WasmExternRef? ref) => js
     .toInt();
 
 @pragma("wasm:prefer-inline")
-WasmExternRef? _newDataViewFromArrayBuffer(
+WasmExternRef? _newDataViewFromArrayBufferOrSharedArrayBuffer(
   WasmExternRef? bufferRef,
   int offsetInBytes,
   int? length,

sdk/lib/html/dart2js/html_dart2js.dart

@@ -46,6 +46,7 @@ import 'dart:web_gl' show RenderingContext, RenderingContext2;
 import 'dart:_foreign_helper' show JS, JS_INTERCEPTOR_CONSTANT;
 import 'dart:js_util' as js_util;
 
+export 'dart:_native_typed_data' show SharedArrayBuffer;
 // Not actually used, but imported since dart:html can generate these objects.
 import 'dart:_js_helper'
     show
@@ -28879,32 +28880,6 @@ Please remove them from your code.
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-@Native("SharedArrayBuffer")
-class SharedArrayBuffer extends JavaScriptObject {
-  // To suppress missing implicit constructor warnings.
-  factory SharedArrayBuffer._() {
-    throw new UnsupportedError("Not supported");
-  }
-
-  factory SharedArrayBuffer([int? length]) {
-    if (length != null) {
-      return SharedArrayBuffer._create_1(length);
-    }
-    return SharedArrayBuffer._create_2();
-  }
-  static SharedArrayBuffer _create_1(length) =>
-      JS('SharedArrayBuffer', 'new SharedArrayBuffer(#)', length);
-  static SharedArrayBuffer _create_2() =>
-      JS('SharedArrayBuffer', 'new SharedArrayBuffer()');
-
-  int? get byteLength native;
-
-  SharedArrayBuffer slice([int? begin, int? end]) native;
-}
-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
 @Native("SharedWorker")
 class SharedWorker extends EventTarget implements AbstractWorker {
   // To suppress missing implicit constructor warnings.

sdk/lib/js_interop/js_interop.dart

@@ -870,16 +870,19 @@ extension ByteBufferToJSArrayBuffer on ByteBuffer {
   /// Converts this [ByteBuffer] to a [JSArrayBuffer] by either casting,
   /// unwrapping, or cloning the [ByteBuffer].
   ///
+  /// Throws if the [ByteBuffer] wraps a JS `SharedArrayBuffer`.
+  ///
   /// > [!NOTE]
   /// > Depending on whether code is compiled to JavaScript or Wasm, this
   /// > conversion will have different semantics.
-  /// > When compiling to JavaScript, all typed lists are the equivalent
-  /// > JavaScript typed arrays, and therefore this method simply casts.
+  /// > When compiling to JavaScript, [ByteBuffer]s are either `ArrayBuffer`s or
+  /// > `SharedArrayBuffer`s so this will just check the type and cast.
   /// > When compiling to Wasm, this [ByteBuffer] may or may not be a wrapper
   /// > depending on if it was converted from JavaScript or instantiated in
-  /// > Dart. If it's a wrapper, this method unwraps it. If it's instantiated in
-  /// > Dart, this method clones this [ByteBuffer]'s values into a new
-  /// > [JSArrayBuffer].
+  /// > Dart. If it's a wrapper, this method unwraps it and either returns the
+  /// > `ArrayBuffer` or throws if the unwrapped buffer was a
+  /// > `SharedArrayBuffer`. If it's instantiated in Dart, this method clones
+  /// > this [ByteBuffer]'s values into a new [JSArrayBuffer].
   /// > Avoid assuming that modifications to this [ByteBuffer] will affect the
   /// > [JSArrayBuffer] and vice versa unless it was instantiated in JavaScript.
   external JSArrayBuffer get toJS;