Normative: throw when trying to write to a detached buffer (#43)

Author: bakkot

package-lock.json

@@ -10,7 +10,7 @@
     "test": "node --test"
   },
   "dependencies": {
-    "@tc39/ecma262-biblio": "^2.1.2663",
+    "@tc39/ecma262-biblio": "2.1.2672",
     "ecmarkup": "^18.0.0",
     "jsdom": "^21.1.1",
     "prismjs": "^1.29.0"

package.json

@@ -224,6 +224,9 @@ export function base64ToUint8Array(string, options, into) {
   if (!['loose', 'strict', 'stop-before-partial'].includes(lastChunkHandling)) {
     throw new TypeError('expected lastChunkHandling to be either "loose", "strict", or "stop-before-partial"');
   }
+  if (into && 'detached' in into.buffer && into.buffer.detached) {
+    throw new TypeError('toBase64Into called on array backed by detached buffer');
+  }
 
   let maxLength = into ? into.length : 2 ** 53 - 1;
 
@@ -260,6 +263,9 @@ export function hexToUint8Array(string, into) {
   if (/[^0-9a-fA-F]/.test(string)) {
     throw new SyntaxError('string should only contain hex characters');
   }
+  if (into && 'detached' in into.buffer && into.buffer.detached) {
+    throw new TypeError('fromHexInto called on array backed by detached buffer');
+  }
 
   let maxLength = into ? into.length : 2 ** 53 - 1;
 

playground/polyfill-core.mjs

@@ -83,6 +83,7 @@ <h1>Uint8Array.fromBase64Into ( _string_, _into_ [ , _options_ ] )</h1>
     1. If _lastChunkHandling_ is *undefined*, set _lastChunkHandling_ to *"loose"*.
     1. If _lastChunkHandling_ is not one of *"loose"*, *"strict"*, or *"stop-before-partial"*, throw a *TypeError* exception.
     1. Let _taRecord_ be MakeTypedArrayWithBufferWitnessRecord(_into_, ~seq-cst~).
+    1. If IsTypedArrayOutOfBounds(_taRecord_) is *true*, throw a *TypeError* exception.
     1. Let _byteLength_ be TypedArrayByteLength(_taRecord_).
     1. Let _maxLength_ be _byteLength_.
     1. Let _result_ be ? FromBase64(_string_, _alphabet_, _lastChunkHandling_, _maxLength_).
@@ -121,6 +122,7 @@ <h1>Uint8Array.fromHexInto ( _string_, _into_ )</h1>
     1. If _string_ is not a String, throw a *TypeError* exception.
     1. Perform ? ValidateUint8Array(_into_).
     1. Let _taRecord_ be MakeTypedArrayWithBufferWitnessRecord(_into_, ~seq-cst~).
+    1. If IsTypedArrayOutOfBounds(_taRecord_) is *true*, throw a *TypeError* exception.
     1. Let _byteLength_ be TypedArrayByteLength(_taRecord_).
     1. Let _maxLength_ be _byteLength_.
     1. Let _result_ be ? FromHex(_string_, _maxLength_).