Bug 310373 – TextDecoder fails occasionally, not each time.

• Status: NEW
• Component: New Bugs

[Andrew Hodel]

Created attachment 478734 [details]
error in console that shows value aaaa of ArrayBuffer and occasional failure

The first parameter to `TextDecoder.decode` is as specified at https://developer.mozilla.org/en-US/docs/Web/API/TextDecoder/decode

Parameters
buffer Optional
An ArrayBuffer, a TypedArray, or a DataView object containing the encoded text to decode.

It is a `ArrayBuffer` with the utf8 value `aaaa` as shown in the screenshot.

```
 9052         unicode_string_from_ab_decode(ab) {
 9053
 9054                 var r = Math.random(100);
 9055
 9056                 console.log(r, ab instanceof Uint8Array, ab, new Uint8Array(ab));
 9057
 9058                 let decoder = new TextDecoder('utf-8');
 9059                 let decoded_value = decoder.decode(ab);
 9060
 9061                 console.log(r, ab instanceof Uint8Array, typeof(decoded_value));
 9062
 9063                 return decoded_value;
 9064
 9065         }
```

[Andrew Hodel]

It works if you create another non resizable ArrayBuffer, thereby doubling the memory usage.

From MDN Web Docs via Google Gemini:

TextDecoder.decode() generally expects a fixed-length ArrayBuffer or a TypedArray. While newer JavaScript standards allow resizable ArrayBuffers, they can cause issues in older APIs. To fix this, create a new, non-resizable Uint8Array view or copy of the buffer content before passing it to TextDecoder.

[Radar WebKit Bug Importer]

<rdar://problem/173518775>

[fantasai]

Thanks for the simplified testcase. Is there a live site also associated with this error?

[Andrew Hodel]

Yes, but it is on an RFC1918 network plus requires authentication.

[Anne van Kesteren]

This API doesn't support resizable buffers. Are you sure it's really non-determinism you're seeing and not just the result of you occasionally passing in a resizable buffer?

[Anne van Kesteren]

(Bug 310341 was recently filed for considering adding resizable buffer support to this API.)