fixup! lib: refactor internal webidl converters

Author: panva

lib/internal/webidl.js

@@ -2,7 +2,6 @@
 
 const {
   ArrayBufferIsView,
-  ArrayBufferPrototypeGetByteLength,
   ArrayBufferPrototypeGetResizable,
   ArrayPrototypePush,
   ArrayPrototypeToSorted,
@@ -812,35 +811,20 @@ function getViewedArrayBuffer(V) {
     TypedArrayPrototypeGetBuffer(V) : DataViewPrototypeGetBuffer(V);
 }
 
-/**
- * Returns whether buffer is a SharedArrayBuffer.
- *
- * Web IDL specifies this as IsSharedArrayBuffer(buffer). Use the
- * ArrayBuffer.prototype.byteLength getter as an equivalent brand check:
- * it succeeds only for ArrayBuffers and throws for SharedArrayBuffers.
- * This keeps the common ArrayBuffer-backed view path in JS without calling
- * the C++ isSharedArrayBuffer binding, while preserving the prototype-chain
- * independent behavior required by the spec.
- * @param {ArrayBuffer|SharedArrayBuffer} buffer Backing buffer.
- * @returns {boolean}
- */
-function isSharedArrayBufferBacking(buffer) {
-  try {
-    ArrayBufferPrototypeGetByteLength(buffer);
-    return false;
-  } catch {
-    return true;
-  }
-}
-
 /**
  * Validates [AllowShared] and [AllowResizable] backing-store constraints.
  * @param {ArrayBuffer|SharedArrayBuffer} buffer Backing buffer.
  * @param {ConversionOptions} options Conversion options.
  * @returns {void}
  */
 function validateBufferSourceBacking(buffer, options) {
-  if (isSharedArrayBufferBacking(buffer)) {
+  let resizable;
+  try {
+    // ArrayBuffer.prototype.resizable is an ArrayBuffer brand check and the
+    // [AllowResizable] value we need. For SharedArrayBuffer-backed views it
+    // throws, which lets this path avoid a separate IsSharedArrayBuffer check.
+    resizable = ArrayBufferPrototypeGetResizable(buffer);
+  } catch {
     // ArrayBufferView conversion step 2: reject SharedArrayBuffer
     // backing stores unless [AllowShared] is present.
     if (!options.allowShared) {
@@ -853,10 +837,11 @@ function validateBufferSourceBacking(buffer, options) {
     validateAllowGrowableSharedArrayBuffer(buffer, options);
     return;
   }
+
   // ArrayBuffer conversion step 3 and ArrayBufferView conversion step 3:
   // reject non-fixed ArrayBuffer backing stores unless [AllowResizable]
   // is present.
-  validateAllowResizableArrayBuffer(buffer, options);
+  validateAllowResizableArrayBuffer(resizable, options);
 }
 
 /**
@@ -882,16 +867,16 @@ function validateAllowGrowableSharedArrayBuffer(buffer, options) {
 
 /**
  * Validates the [AllowResizable] constraint for resizable ArrayBuffer.
- * @param {ArrayBuffer} buffer ArrayBuffer backing buffer.
+ * @param {boolean} resizable ArrayBuffer [[ArrayBufferResizable]] value.
  * @param {ConversionOptions} options Conversion options.
  * @returns {void}
  */
-function validateAllowResizableArrayBuffer(buffer, options) {
+function validateAllowResizableArrayBuffer(resizable, options) {
   // ArrayBuffer and ArrayBufferView conversion step 3:
   // IsFixedLengthArrayBuffer(buffer) must be true without [AllowResizable].
   // Read [[ArrayBufferResizable]] first so fixed buffers skip the options
   // property lookup on this hot path.
-  if (ArrayBufferPrototypeGetResizable(buffer) && !options.allowResizable) {
+  if (resizable && !options.allowResizable) {
     throw makeException(
       'is backed by a resizable ArrayBuffer, which is not allowed.',
       options);
@@ -935,9 +920,13 @@ converters.BufferSource = (V, options = kEmptyObject) => {
     // and return a reference to the same view.
     // Keep this logic inline instead of calling validateBufferSourceBacking().
     // BufferSource conversion is hot, and this avoids a helper call while still
-    // using primordial getters for the backing-buffer internal-slot checks.
+    // using a primordial getter for the backing-buffer internal-slot check.
+    let resizable;
     try {
-      ArrayBufferPrototypeGetByteLength(buffer);
+      // ArrayBuffer.prototype.resizable is both the ArrayBuffer brand check
+      // and the step 3 value. It throws for SharedArrayBuffer, which gives us
+      // the step 2 branch without an extra byteLength getter call.
+      resizable = ArrayBufferPrototypeGetResizable(buffer);
     } catch {
       if (!options.allowShared) {
         throw makeException(
@@ -947,7 +936,7 @@ converters.BufferSource = (V, options = kEmptyObject) => {
       validateAllowGrowableSharedArrayBuffer(buffer, options);
       return V;
     }
-    if (ArrayBufferPrototypeGetResizable(buffer) && !options.allowResizable) {
+    if (resizable && !options.allowResizable) {
       throw makeException(
         'is backed by a resizable ArrayBuffer, which is not allowed.',
         options);