can1357/oh-my-pi · error · ArchiveError

Invalid ARJ archive: truncated data

Error message

Invalid ARJ archive: truncated data

What it means

This ArchiveError is thrown when the number of bytes actually read from the ByteSource is less than the source's declared size — the archive data is truncated relative to what was promised. The library compares bytes.byteLength against source.size after fully reading.

Source

Thrown at packages/utils/src/ar/arj.ts:238

	if (size < 30 || size > ARJ_MAX_BASIC_HEADER || bytes.byteLength < size + 8) return false;
	const body = bytes.subarray(4, 4 + size);
	return body[0]! >= 30 && body[0]! <= size && body[6] === 2 && crc32(body) === u32(bytes, 4 + size);
}

/** Index an ARJ archive and lazily decode stored, static-Huffman, and fast-LZSS members. */
export const readArj: FormatReader = async (
	source: ByteSource,
	options: FormatReadOptions,
): Promise<ArchiveIndexEntry[]> => {
	assertInMemorySize(source.size, options.limits);
	let bytes: Uint8Array;
	try {
		bytes = await readAllBytes(source);
	} catch (error) {
		if (error instanceof ArchiveError) throw error;
		throw new ArchiveError(`Unable to read ARJ archive: ${error instanceof Error ? error.message : String(error)}`);
	}
	if (bytes.byteLength !== source.size) throw new ArchiveError("Invalid ARJ archive: truncated data");
	if (!sniffArj(bytes)) throw new ArchiveError("Invalid ARJ archive header");

	const main = parseArjBlock(bytes, 0, options);
	if (main.isEnd) throw new ArchiveError("Invalid ARJ archive: missing main header");
	const mainFirstHeaderSize = bytes[main.bodyStart]!;
	if (mainFirstHeaderSize < 30 || mainFirstHeaderSize > main.bodySize || bytes[main.bodyStart + 6] !== 2) {
		throw new ArchiveError("Invalid ARJ main header");
	}
	const mainFlags = bytes[main.bodyStart + 4]!;
	if ((mainFlags & 0x01) !== 0) throw new ArchiveError("Encrypted ARJ archives are unsupported");
	if ((mainFlags & 0x04) !== 0) throw new ArchiveError("Multi-volume ARJ archives are unsupported");

	const entries: ArchiveIndexEntry[] = [];
	let offset = main.nextOffset;
	let metadataSize = main.metadataSize;
	let parsedCount = 0;
	for (;;) {
		const block = parseArjBlock(bytes, offset, options);

View on GitHub (pinned to 9690622007)

Solutions

  1. Re-download or re-copy the archive; the file is incomplete.
  2. Re-stat the file and pass a fresh, correct size to the ByteSource.
  3. Compare the on-disk file size to the expected size from the archive provider.
  4. If reading a stream, ensure the stream is fully drained and not closed early.

Example fix

// before
const stat = await fs.stat(path);
const entries = await readArj({ path, size: stat.size }, options);
// after
const stat = await fs.stat(path);
if (stat.size < expectedMinSize) throw new Error(`${path} looks truncated (${stat.size} bytes)`);
const entries = await readArj({ path, size: stat.size }, options);
Defensive patterns

Strategy: validation

Validate before calling

const stat = await fs.stat(path);
if (stat.size === 0) throw new Error(`${path} is empty`);
// pass stat.size as the ByteSource size so the truncation check can fire accurately
const entries = await readArj({ path, size: stat.size }, options);

Try / catch

try {
  const entries = await readArj(source, options);
} catch (e) {
  if (e instanceof ArchiveError && e.message.includes('truncated data')) {
    throw new Error('archive is incomplete; re-download it');
  }
  throw e;
}

Prevention

When it happens

Trigger: Calling readArj(source, options) where the underlying file/stream yields fewer bytes than source.size reported (file shrank between stat and read, partial download, reader stream ended early).

Common situations: Interrupted downloads, files still being written, rsync/copy interrupted, cloud-sync placeholders not fully materialized.

Related errors

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/1e4ec7d162db44e6. Report an issue: GitHub.