nodejs / nodejs/node

TextDecoder: ERR_ENCODING_INVALID_ENCODED_DATA on very long array buffer

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util
Dominant language
JavaScript
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Description

Version

v18.14.1

Platform

Linux 5.19.0-38-generic #39~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Mar 17 21:16:15 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

When I try to decode a long utf-16le encoded buffer, ERR_ENCODING_INVALID_ENCODED_DATA is thrown instead of ERR_STRING_TOO_LONG.

new TextDecoder("utf-16le").decode(new Uint16Array(2**27).fill(48))
// Uncaught TypeError: The encoded data was not valid for encoding utf-16le
//     at TextDecoder.decode (node:internal/encoding:448:14) {
//   code: 'ERR_ENCODING_INVALID_ENCODED_DATA'
// }

The default encoding version seems to work correctly, and throws an appropriate error

new TextDecoder().decode(new Uint8Array(2**29).fill(48))
// Uncaught Error: Cannot create a string longer than 0x1fffffe8 characters
//     at TextDecoder.decode (node:internal/encoding:433:16) {
//   code: 'ERR_STRING_TOO_LONG'
// }

Another thing that I realized is that TextDecoder() seems to be capable of consuming an array buffer twice as long as TextDecoder("utf-16le") without throwing error, and produce a string that's 4 times as long.

How often does it reproduce? Is there a required condition?

Confirmed this bug in both normal file execution and node.js repl

What is the expected behavior? Why is that the expected behavior?

new TextDecoder("utf-16le") should be able to create a string up to 0x1fffffe8 characters.
It should throw ERR_STRING_TOO_LONG when this length is exceeded.

What do you see instead?

ERR_ENCODING_INVALID_ENCODED_DATA is thrown when the input Uint16Array length is 2**27

Uncaught TypeError: The encoded data was not valid for encoding utf-16le
    at TextDecoder.decode (node:internal/encoding:448:14) {
  code: 'ERR_ENCODING_INVALID_ENCODED_DATA'
}
Additional information

No response

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the TextDecoder.decode path shown at node:internal/encoding:448 and compare it with the default decoder path at node:internal/encoding:433. Reproduce the utf-16le case using the provided Uint16Array input, then verify that oversized decoded output reports ERR_STRING_TOO_LONG rather than ERR_ENCODING_INVALID_ENCODED_DATA.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript, node.js
Domain
backend
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Active
Clarity
Mostly clear
Newbie friendliness
55/100

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