FuelLabs/fuels-ts · error · FuelError

DECODE_ERROR

DECODE_ERROR

Error message

Invalid string slice data size.

What it means

Thrown by StrSliceCoder.decode() when the data buffer is shorter than WORD_SIZE (8 bytes). A Sway str slice is encoded as a u64 length prefix followed by UTF-8 bytes, requiring at least 8 bytes for the length prefix.

Source

Thrown at packages/abi-coder/src/encoding/coders/StrSliceCoder.ts:25

import { Coder } from './AbstractCoder';
import { BigNumberCoder } from './BigNumberCoder';

export class StrSliceCoder extends Coder<string, string> {
  static memorySize = 1;
  constructor() {
    super('strSlice', 'str', WORD_SIZE);
  }

  encode(value: string): Uint8Array {
    const bytes = toUtf8Bytes(value);
    const lengthBytes = new BigNumberCoder('u64').encode(value.length);

    return new Uint8Array([...lengthBytes, ...bytes]);
  }

  decode(data: Uint8Array, offset: number): [string, number] {
    if (data.length < this.encodedLength) {
      throw new FuelError(ErrorCode.DECODE_ERROR, `Invalid string slice data size.`);
    }

    const offsetAndLength = offset + WORD_SIZE;
    const lengthBytes = data.slice(offset, offsetAndLength);
    const length = bn(new BigNumberCoder('u64').decode(lengthBytes, 0)[0]).toNumber();
    const bytes = data.slice(offsetAndLength, offsetAndLength + length);

    if (bytes.length !== length) {
      throw new FuelError(ErrorCode.DECODE_ERROR, `Invalid string slice byte data size.`);
    }

    return [toUtf8String(bytes), offsetAndLength + length];
  }
}

View on GitHub (pinned to b3f37c91ac)

Solutions

1. Verify data.length >= 8 before calling decode().
2. Confirm the data is a str slice encoding, not a std String or fixed-length str[N].
3. Re-fetch data if truncation is suspected.

Example fix

// before
strSliceCoder.decode(new Uint8Array([0]), 0); // throws DECODE_ERROR

// after
if (data.length < 8) {
  throw new Error('Data too short for str slice decode');
}
strSliceCoder.decode(data, 0);

function canDecodeStrSlice(data: Uint8Array): boolean {
  return data.length >= 8; // WORD_SIZE
}

When it happens

Trigger: Passing fewer than 8 bytes to decode(). Decoding data not produced by StrSliceCoder. Receiving a truncated ABI payload from an RPC response.

Common situations: Confusing str slice (str) with std String (StdStringCoder) or fixed str[N] (StringCoder). Malformed RPC data. Buffer truncation in transit.

Related errors

• DECODE_ERROR
• DECODE_ERROR
• DECODE_ERROR
• DECODE_ERROR
• DECODE_ERROR

AI-assisted analysis of FuelLabs/fuels-ts@b3f37c91ac (2026-08-12). Data as JSON: /api/errors/94d15ab40ef1828a. Report an issue: GitHub.