can1357/oh-my-pi · error · ArchiveError

Invalid XZ stream: decoded block size mismatch

Error message

Invalid XZ stream: decoded block size mismatch

What it means

After LZMA2 decompression the output length must equal the uncompressed size recorded in the stream index. A mismatch means the compressed payload, LZMA2 properties, or index record are inconsistent — the decoder refuses to return wrong-sized data.

Source

Thrown at packages/utils/src/ar/codecs/xz.ts:475

	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");
	return output;
}

/** Whether bytes begin with the XZ stream-header magic. */
export function isXz(bytes: Uint8Array): boolean {
	return bytes.byteLength >= XZ_MAGIC.byteLength && equalBytes(bytes.subarray(0, XZ_MAGIC.byteLength), XZ_MAGIC);
}

/** Decompress all concatenated streams in an XZ container within `maxOutput`. */
export async function xzDecompress(bytes: Uint8Array, maxOutput: number): Promise<Uint8Array> {

View on GitHub (pinned to 9690622007)

Solutions

1. Validate with `xz -t` and re-download the archive from a trusted source.
2. Re-compress with the standard xz tool if the producer was custom or non-standard.
3. Check that the compressed byte range was not altered (no manual slicing/splicing of the stream).
4. Report the archive as corrupt rather than attempting partial recovery.

const ok = await $`xz -t ${path}`.quiet().nothrow();
if (ok.exitCode !== 0) throw new Error(`XZ integrity check failed: ${path}`);

try {
	return await xzDecompress(bytes, maxOutput);
} catch (err) {
	if (err instanceof ArchiveError && /size mismatch/i.test(err.message)) {
		throw new Error('Decompressed data does not match the index — archive is corrupt');
	}
	throw err;
}

When it happens

Trigger: xzDecompress decompresses a block whose lzma2Decompress output byteLength differs from record.uncompressedSize — e.g. the index claims a different size than the payload actually produces, or LZMA2 properties (dict size byte) are wrong for the payload.

Common situations: Bit-corrupted compressed data, archives whose index was rewritten or spliced, or files produced by encoders that misreport uncompressed sizes.

Related errors

• Invalid XZ stream: non-canonical variable-length integer
• Unsupported XZ block flags
• Invalid XZ stream: truncated filter properties
• Invalid XZ stream: non-zero block header padding
• Invalid XZ stream: compressed block size is invalid

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/8a4a16e480199805. Report an issue: GitHub.