can1357/oh-my-pi · error · ArchiveError

Invalid ARJ main header

Error message

Invalid ARJ main header

What it means

This ArchiveError is thrown when the ARJ main header's first-header-size byte is out of range (< 30 or larger than the basic header body) or its archiver-version byte (offset 6) is not 2. The signature and header CRC passed, but the main header content is structurally invalid for this reader.

Source

Thrown at packages/utils/src/ar/arj.ts:245

	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);
		metadataSize += block.metadataSize;
		assertIndexSize(metadataSize, options.limits, "index");
		if (block.isEnd) break;
		assertEntryCount(++parsedCount, options.limits);
		const firstHeaderSize = bytes[block.bodyStart]!;
		if (firstHeaderSize < 30 || firstHeaderSize > block.bodySize) throw new ArchiveError("Invalid ARJ local header");
		const hostOs = bytes[block.bodyStart + 3]!;

View on GitHub (pinned to 9690622007)

Solutions

  1. Verify the archive with the official arj tool to confirm whether it is standard-compliant.
  2. Recreate the archive with standard ARJ or a well-known compatible tool.
  3. Check the producing tool's version; security-enhanced ARJ variants may need their own reader.
  4. If corruption is suspected, re-download and compare checksums.

Example fix

// before
const entries = await readArj(source, options);
// after
try {
  const entries = await readArj(source, options);
} catch (e) {
  if (e instanceof ArchiveError && e.message === 'Invalid ARJ main header') {
    throw new Error('archive main header is malformed or from an unsupported ARJ variant; re-pack with standard ARJ');
  }
  throw e;
}
Defensive patterns

Strategy: try-catch

Validate before calling

// main header body byte 6 must be the archiver version (2)
// and byte 0 the first-header size (>= 30) — verify after sniff
if (bytes[4] < 30 || bytes[4 + u16(bytes, 2)] === undefined || bytes[4 + 6] !== 2) {
  throw new Error('non-standard ARJ main header; re-pack with standard ARJ');
}

Try / catch

try {
  const entries = await readArj(source, options);
} catch (e) {
  if (e instanceof ArchiveError && e.message === 'Invalid ARJ main header') {
    throw new Error('unsupported or malformed ARJ main header; use a standard-compliant archive');
  }
  throw e;
}

Prevention

When it happens

Trigger: Calling readArj on an archive whose main header was crafted by a non-standard writer, whose version field is not 2, or whose header size bytes were corrupted after the CRC passed (unlikely) — detected via bytes[bodyStart] and bytes[bodyStart+6].

Common situations: Archives from obscure/buggy ARJ clones, files hand-patched, corruption within the header body, or format variants (e.g. some security-enhanced ARJ versions) not matching the expected layout.

Related errors

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/6cf67f503c36c6ac. Report an issue: GitHub.