nodejs · nodejs-github-bot · Apr 22, 2026 · Apr 19, 2026
diff --git a/benchmark/misc/webidl-buffer-source.js b/benchmark/misc/webidl-buffer-source.js
@@ -0,0 +1,54 @@
+'use strict';
+
+const common = require('../common.js');
+
+const bench = common.createBenchmark(main, {
+  input: [
+    'arraybuffer',
+    'buffer',
+    'dataview',
+    'uint8array',
+    'uint8clampedarray',
+    'int8array',
+    'uint16array',
+    'int16array',
+    'uint32array',
+    'int32array',
+    'float16array',
+    'float32array',
+    'float64array',
+    'bigint64array',
+    'biguint64array',
+  ],
+  n: [1e6],
+}, { flags: ['--expose-internals'] });
+
+function main({ n, input }) {
+  const { converters } = require('internal/webidl');
+
+  let value;
+  switch (input) {
+    case 'arraybuffer': value = new ArrayBuffer(32); break;
+    case 'buffer': value = Buffer.alloc(32); break;
+    case 'dataview': value = new DataView(new ArrayBuffer(32)); break;
+    case 'uint8array': value = new Uint8Array(32); break;
+    case 'uint8clampedarray': value = new Uint8ClampedArray(32); break;
+    case 'int8array': value = new Int8Array(32); break;
+    case 'uint16array': value = new Uint16Array(16); break;
+    case 'int16array': value = new Int16Array(16); break;
+    case 'uint32array': value = new Uint32Array(8); break;
+    case 'int32array': value = new Int32Array(8); break;
+    case 'float16array': value = new Float16Array(16); break;
+    case 'float32array': value = new Float32Array(8); break;
+    case 'float64array': value = new Float64Array(4); break;
+    case 'bigint64array': value = new BigInt64Array(4); break;
+    case 'biguint64array': value = new BigUint64Array(4); break;
+  }
+
+  const opts = { prefix: 'test', context: 'test' };
+
+  bench.start();
+  for (let i = 0; i < n; i++)
+    converters.BufferSource(value, opts);
+  bench.end(n);
+}
diff --git a/lib/internal/webidl.js b/lib/internal/webidl.js
@@ -2,6 +2,7 @@
 
 const {
   ArrayBufferIsView,
+  ArrayBufferPrototypeGetByteLength,
   ArrayPrototypePush,
   ArrayPrototypeToSorted,
   DataViewPrototypeGetBuffer,
@@ -33,8 +34,7 @@ const {
 const { kEmptyObject } = require('internal/util');
 const {
   isArrayBuffer,
-  isDataView,
-  isSharedArrayBuffer,
+  isTypedArray,
 } = require('internal/util/types');
 
 const converters = { __proto__: null };
@@ -390,9 +390,23 @@ function createInterfaceConverter(name, I) {
   };
 }
 
-function getDataViewOrTypedArrayBuffer(V) {
-  return isDataView(V) ?
-    DataViewPrototypeGetBuffer(V) : TypedArrayPrototypeGetBuffer(V);
+// Returns the [[ViewedArrayBuffer]] of an ArrayBufferView without leaving JS.
+function getViewedArrayBuffer(V) {
+  return isTypedArray(V) ?
+    TypedArrayPrototypeGetBuffer(V) : DataViewPrototypeGetBuffer(V);
+}
+
+// Returns `true` if `buffer` is a `SharedArrayBuffer`. Uses a brand check via
+// the `ArrayBuffer.prototype.byteLength` getter, which succeeds only on real
+// (non-shared) ArrayBuffers and throws on SharedArrayBuffers — independent
+// of the receiver's prototype chain.
+function isSharedArrayBufferBacking(buffer) {
+  try {
+    ArrayBufferPrototypeGetByteLength(buffer);
+    return false;
+  } catch {
+    return true;
+  }
 }
 
 // https://webidl.spec.whatwg.org/#ArrayBufferView
@@ -402,7 +416,7 @@ converters.ArrayBufferView = (V, opts = kEmptyObject) => {
       'is not an ArrayBufferView.',
       opts);
   }
-  if (isSharedArrayBuffer(getDataViewOrTypedArrayBuffer(V))) {
+  if (isSharedArrayBufferBacking(getViewedArrayBuffer(V))) {
     throw makeException(
       'is a view on a SharedArrayBuffer, which is not allowed.',
       opts);
@@ -414,7 +428,7 @@ converters.ArrayBufferView = (V, opts = kEmptyObject) => {
 // https://webidl.spec.whatwg.org/#BufferSource
 converters.BufferSource = (V, opts = kEmptyObject) => {
   if (ArrayBufferIsView(V)) {
-    if (isSharedArrayBuffer(getDataViewOrTypedArrayBuffer(V))) {
+    if (isSharedArrayBufferBacking(getViewedArrayBuffer(V))) {
       throw makeException(
         'is a view on a SharedArrayBuffer, which is not allowed.',
         opts);

diff --git a/test/parallel/test-internal-webidl-buffer-source.js b/test/parallel/test-internal-webidl-buffer-source.js
@@ -0,0 +1,208 @@
+// Flags: --expose-internals
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const { test } = require('node:test');
+
+const { converters } = require('internal/webidl');
+
+const TYPED_ARRAY_CTORS = [
+  Uint8Array, Int8Array, Uint8ClampedArray,
+  Uint16Array, Int16Array,
+  Uint32Array, Int32Array,
+  Float16Array, Float32Array, Float64Array,
+  BigInt64Array, BigUint64Array,
+];
+
+test('BufferSource accepts ArrayBuffer', () => {
+  const ab = new ArrayBuffer(8);
+  assert.strictEqual(converters.BufferSource(ab), ab);
+});
+
+test('BufferSource accepts all TypedArray kinds', () => {
+  for (const Ctor of TYPED_ARRAY_CTORS) {
+    const ta = new Ctor(4);
+    assert.strictEqual(converters.BufferSource(ta), ta);
+  }
+});
+
+test('BufferSource accepts Buffer', () => {
+  const buf = Buffer.alloc(8);
+  assert.strictEqual(converters.BufferSource(buf), buf);
+});
+
+test('BufferSource accepts DataView', () => {
+  const dv = new DataView(new ArrayBuffer(8));
+  assert.strictEqual(converters.BufferSource(dv), dv);
+});
+
+test('BufferSource accepts ArrayBuffer subclass instance', () => {
+  class MyAB extends ArrayBuffer {}
+  const sub = new MyAB(8);
+  assert.strictEqual(converters.BufferSource(sub), sub);
+});
+
+test('BufferSource accepts TypedArray with null prototype', () => {
+  const ta = new Uint8Array(4);
+  Object.setPrototypeOf(ta, null);
+  assert.strictEqual(converters.BufferSource(ta), ta);
+});
+
+test('BufferSource accepts DataView with null prototype', () => {
+  const dv = new DataView(new ArrayBuffer(4));
+  Object.setPrototypeOf(dv, null);
+  assert.strictEqual(converters.BufferSource(dv), dv);
+});
+
+test('BufferSource accepts ArrayBuffer with null prototype', () => {
+  const ab = new ArrayBuffer(4);
+  Object.setPrototypeOf(ab, null);
+  assert.strictEqual(converters.BufferSource(ab), ab);
+});
+
+test('BufferSource rejects SharedArrayBuffer', () => {
+  assert.throws(
+    () => converters.BufferSource(new SharedArrayBuffer(4)),
+    { code: 'ERR_INVALID_ARG_TYPE' },
+  );
+});
+
+test('BufferSource rejects SAB-backed TypedArray', () => {
+  const view = new Uint8Array(new SharedArrayBuffer(4));
+  assert.throws(
+    () => converters.BufferSource(view),
+    { code: 'ERR_INVALID_ARG_TYPE' },
+  );
+});
+
+test('BufferSource rejects SAB-backed DataView', () => {
+  const dv = new DataView(new SharedArrayBuffer(4));
+  assert.throws(
+    () => converters.BufferSource(dv),
+    { code: 'ERR_INVALID_ARG_TYPE' },
+  );
+});
+
+test('BufferSource rejects SAB view whose buffer prototype was reassigned', () => {
+  const sab = new SharedArrayBuffer(4);
+  Object.setPrototypeOf(sab, ArrayBuffer.prototype);
+  const view = new Uint8Array(sab);
+  assert.throws(
+    () => converters.BufferSource(view),
+    { code: 'ERR_INVALID_ARG_TYPE' },
+  );
+});
+
+test('BufferSource accepts a detached ArrayBuffer', () => {
+  const ab = new ArrayBuffer(8);
+  structuredClone(ab, { transfer: [ab] });
+  assert.strictEqual(ab.byteLength, 0);
+  assert.strictEqual(converters.BufferSource(ab), ab);
+});
+
+test('BufferSource rejects objects with a forged @@toStringTag', () => {
+  const fake = { [Symbol.toStringTag]: 'Uint8Array' };
+  assert.throws(
+    () => converters.BufferSource(fake),
+    { code: 'ERR_INVALID_ARG_TYPE' },
+  );
+});
+
+for (const value of [null, undefined, 0, 1, 1n, '', 'x', true, Symbol('s'), [],
+                     {}, () => {}]) {
+  test(`BufferSource rejects ${typeof value} ${String(value)}`, () => {
+    assert.throws(
+      () => converters.BufferSource(value),
+      { code: 'ERR_INVALID_ARG_TYPE' },
+    );
+  });
+}
+
+test('ArrayBufferView accepts all TypedArray kinds', () => {
+  for (const Ctor of TYPED_ARRAY_CTORS) {
+    const ta = new Ctor(4);
+    assert.strictEqual(converters.ArrayBufferView(ta), ta);
+  }
+});
+
+test('ArrayBufferView accepts DataView', () => {
+  const dv = new DataView(new ArrayBuffer(8));
+  assert.strictEqual(converters.ArrayBufferView(dv), dv);
+});
+
+test('ArrayBufferView accepts TypedArray subclass instance', () => {
+  class MyU8 extends Uint8Array {}
+  const sub = new MyU8(4);
+  assert.strictEqual(converters.ArrayBufferView(sub), sub);
+});
+
+test('ArrayBufferView accepts TypedArray with null prototype', () => {
+  const ta = new Uint8Array(4);
+  Object.setPrototypeOf(ta, null);
+  assert.strictEqual(converters.ArrayBufferView(ta), ta);
+});
+
+test('ArrayBufferView accepts DataView with null prototype', () => {
+  const dv = new DataView(new ArrayBuffer(4));
+  Object.setPrototypeOf(dv, null);
+  assert.strictEqual(converters.ArrayBufferView(dv), dv);
+});
+
+test('ArrayBufferView rejects raw ArrayBuffer', () => {
+  assert.throws(
+    () => converters.ArrayBufferView(new ArrayBuffer(4)),
+    { code: 'ERR_INVALID_ARG_TYPE' },
+  );
+});
+
+test('ArrayBufferView rejects raw SharedArrayBuffer', () => {
+  assert.throws(
+    () => converters.ArrayBufferView(new SharedArrayBuffer(4)),
+    { code: 'ERR_INVALID_ARG_TYPE' },
+  );
+});
+
+test('ArrayBufferView rejects SAB-backed TypedArray', () => {
+  const view = new Uint8Array(new SharedArrayBuffer(4));
+  assert.throws(
+    () => converters.ArrayBufferView(view),
+    { code: 'ERR_INVALID_ARG_TYPE' },
+  );
+});
+
+test('ArrayBufferView rejects SAB-backed DataView', () => {
+  const dv = new DataView(new SharedArrayBuffer(4));
+  assert.throws(
+    () => converters.ArrayBufferView(dv),
+    { code: 'ERR_INVALID_ARG_TYPE' },
+  );
+});
+
+test('ArrayBufferView rejects SAB view whose buffer prototype was reassigned', () => {
+  const sab = new SharedArrayBuffer(4);
+  Object.setPrototypeOf(sab, ArrayBuffer.prototype);
+  const view = new Uint8Array(sab);
+  assert.throws(
+    () => converters.ArrayBufferView(view),
+    { code: 'ERR_INVALID_ARG_TYPE' },
+  );
+});
+
+test('ArrayBufferView rejects objects with a forged @@toStringTag', () => {
+  const fake = { [Symbol.toStringTag]: 'Uint8Array' };
+  assert.throws(
+    () => converters.ArrayBufferView(fake),
+    { code: 'ERR_INVALID_ARG_TYPE' },
+  );
+});
+
+for (const value of [null, undefined, 0, 1, 1n, '', 'x', true, Symbol('s'), [],
+                     {}, () => {}]) {
+  test(`ArrayBufferView rejects ${typeof value} ${String(value)}`, () => {
+    assert.throws(
+      () => converters.ArrayBufferView(value),
+      { code: 'ERR_INVALID_ARG_TYPE' },
+    );
+  });
+}