FuelLabs/fuels-ts · error · FuelError

DECODE_ERROR

DECODE_ERROR

Error message

Invalid string data size.

What it means

Thrown by StringCoder.decode() when the data buffer is shorter than the fixed length N declared by the coder. Unlike variable-length string coders, StringCoder expects exactly N bytes of data to decode a fixed-length Sway str[N].

Source

Thrown at packages/abi-coder/src/encoding/coders/StringCoder.ts:21

import { Coder } from './AbstractCoder';

export class StringCoder<TLength extends number = number> extends Coder<string, string> {
  constructor(length: TLength) {
    super('string', `str[${length}]`, length);
  }

  encode(value: string): Uint8Array {
    if (value.length !== this.encodedLength) {
      throw new FuelError(ErrorCode.ENCODE_ERROR, `Value length mismatch during encode.`);
    }

    return toUtf8Bytes(value);
  }

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

    const bytes = data.slice(offset, offset + this.encodedLength);

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

    return [toUtf8String(bytes), offset + this.encodedLength];
  }
}

View on GitHub (pinned to b3f37c91ac)

Solutions

1. Verify data.length >= coder.encodedLength (N) before calling decode().
2. Confirm the coder's N matches the ABI's str[N] declaration.
3. Ensure data is not truncated in transit.

Example fix

// before
new StringCoder(10).decode(new Uint8Array([65, 66]), 0); // throws DECODE_ERROR

// after
const coder = new StringCoder(10);
if (data.length < coder.encodedLength) {
  throw new Error(`Need ${coder.encodedLength} bytes, got ${data.length}`);
}
coder.decode(data, 0);

function canDecodeFixedString(data: Uint8Array, length: number): boolean {
  return data.length >= length;
}

When it happens

Trigger: Decoding a buffer of 2 bytes when the coder expects str[10] (10 bytes). Truncated ABI payload. Using the wrong coder for the data format.

Common situations: ABI mismatch between encoder and decoder. Truncated network data. Wrong coder type used (fixed-length vs variable-length string).

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/abf4c3ebe7a909bf. Report an issue: GitHub.