can1357/oh-my-pi · error · ArchiveError

Invalid XZ stream: truncated block data

Error message

Invalid XZ stream: truncated block data

What it means

The decoder computed where the block's integrity check should live (compressedEnd + 4-byte alignment padding) and it extends past the end of the input buffer. The stream is physically truncated — the bytes the index promised are not there.

Source

Thrown at packages/utils/src/ar/codecs/xz.ts:465

			throw new ArchiveError("Invalid XZ stream: truncated filter properties");
		filters.push({ id, properties: bytes.slice(cursor.pos, cursor.pos + propertySize) });
		cursor.pos += propertySize;
	}
	while (cursor.pos < cursor.limit)
		if (bytes[cursor.pos++] !== 0) throw new ArchiveError("Invalid XZ stream: non-zero block header padding");
	const integritySize = checkSize(checkId);
	const compressedSize = record.unpaddedSize - headerSize - integritySize;
	if (!Number.isSafeInteger(compressedSize) || compressedSize <= 0)
		throw new ArchiveError("Invalid XZ stream: compressed block size is invalid");
	if (declaredCompressed !== undefined && declaredCompressed !== compressedSize)
		throw new ArchiveError("Invalid XZ stream: block compressed size mismatch");
	if (declaredUncompressed !== undefined && declaredUncompressed !== record.uncompressedSize)
		throw new ArchiveError("Invalid XZ stream: block uncompressed size mismatch");
	const compressedStart = offset + headerSize;
	const compressedEnd = compressedStart + compressedSize;
	const paddingSize = (4 - ((headerSize + compressedSize) & 3)) & 3;
	const checkStart = compressedEnd + paddingSize;
	if (checkStart + integritySize > bytes.byteLength) throw new ArchiveError("Invalid XZ stream: truncated block data");
	const last = filters[filters.length - 1]!;
	if (last.id !== 0x21 || last.properties.byteLength !== 1)
		throw new ArchiveError(`Unsupported XZ terminal filter ID 0x${last.id.toString(16)} (LZMA2 required)`);
	let output = await lzma2Decompress(
		last.properties[0]!,
		bytes.subarray(compressedStart, compressedEnd),
		record.uncompressedSize,
	);
	if (output.byteLength !== record.uncompressedSize)
		throw new ArchiveError("Invalid XZ stream: decoded block size mismatch");
	output = output.slice();
	for (let index = filters.length - 2; index >= 0; index--) applyFilter(output, filters[index]!);
	for (let index = compressedEnd; index < checkStart; index++)
		if (bytes[index] !== 0) throw new ArchiveError("Invalid XZ stream: non-zero block padding");
	verifyCheck(checkId, output, bytes.subarray(checkStart, checkStart + integritySize));
	const paddedEnd = offset + Math.ceil(record.unpaddedSize / 4) * 4;
	if (checkStart + integritySize !== paddedEnd)
		throw new ArchiveError("Invalid XZ stream: block size does not match its index record");

View on GitHub (pinned to 9690622007)

Solutions

  1. Re-download the complete file and compare its size/checksum against the source.
  2. Check the code path that reads the file — ensure you read the whole file (Bun.file().bytes()/arrayBuffer()) without a byte cap.
  3. If the archive is being written concurrently, wait for the writer to finish before decompressing.
  4. Catch ArchiveError and surface a 'file truncated/incomplete' message to users.

Example fix

// before
const buf = new Uint8Array(await file.arrayBuffer(), 0, 1_000_000); // capped slice
await xzDecompress(buf, maxOutput);
// after
const buf = await file.bytes(); // full contents
await xzDecompress(buf, maxOutput);
Defensive patterns

Strategy: validation

Validate before calling

const stat = await fs.stat(path);
if (expectedSize !== undefined && stat.size < expectedSize) {
	throw new Error(`Archive incomplete: ${stat.size}/${expectedSize} bytes`);
}
const bytes = await Bun.file(path).bytes();
if (!isXz(bytes)) throw new Error('Not an XZ stream');

Try / catch

try {
	return await xzDecompress(bytes, maxOutput);
} catch (err) {
	if (err instanceof ArchiveError && /truncated/i.test(err.message)) {
		throw new Error(`Download incomplete — re-fetch ${path}`);
	}
	throw err;
}

Prevention

When it happens

Trigger: xzDecompress is given a buffer where checkStart + integritySize exceeds bytes.byteLength for some block — typically a partially downloaded or prematurely truncated .xz file.

Common situations: Interrupted downloads, files copied with size limits (e.g. partial rsync/scp), reading a growing log archive mid-write, or a truncated upload.

Related errors

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/0010c36718e4ccd6. Report an issue: GitHub.