[TS] Flexbuffers fails to decode root vector

[Stumblinbear]

This was noticed in version 23.1.21 however is still occurring in the latest version (23.3.3).

When decoding a flexbuffer where the root element is a vector, it fails to decode properly when there are 4 or more items. If the vector is nested within an object it decodes successfully.

RangeError: Offset is outside the bounds of the DataView
    at DataView.getUint8 (<anonymous>)
    at Reference.get (reference.js:102:45)
    at <snip>

Minimum reproducible example:

import * as flexbuffers from "flatbuffers/ts/flexbuffers";

flexbuffers.toObject(
    flexbuffers.encode(["1", "2", "3", "4"]).buffer
)

[dbaileychess]

@bjornharrtell

[bjornharrtell]

Unfortunately I have no experience with flexbuffers so this is far off my chart at the moment.

[lenaguerrero]

@Stumblinbear did you ever find a resolution for this? I'm running into the same issue.

[Stumblinbear]

@Stumblinbear did you ever find a resolution for this? I'm running into the same issue.

I've just nested it in an object with a single field for the time being

[dristic]

I believe I have a lead on this. In https://github.com/google/flatbuffers/blob/master/ts/flexbuffers/reference.ts#L109 it attempts to read the packed type from the end of the vector, even if the reference is a typed vector and has no type bytes at the end. This will intermittently fail if you don't have enough extra bytes at the end of your buffer which is probably why nesting it in an object "fixes" the problem.

The solution might be to only look for the packed type bytes in the else condition of the conditional on the next line:

let _packedType = -1;
if (isTypedVector(this.valueType)) {
  const _valueType = typedVectorElementType(this.valueType);
  _packedType = packedType(_valueType, BitWidth.WIDTH8);
} else if (isFixedTypedVector(this.valueType)) {
  const _valueType = fixedTypedVectorElementType(this.valueType);
  _packedType = packedType(_valueType, BitWidth.WIDTH8);
} else {
 _packedType = this.dataView.getUint8(_indirect + length * this.byteWidth + key);
}

[github-actions[bot]]

This issue is stale because it has been open 6 months with no activity. Please comment or label not-stale, or this will be closed in 14 days.

[Stumblinbear]

This is still an issue