can1357/oh-my-pi · error · ArchiveError

Invalid CAB archive: unsupported LZX block type ${this.#bloc

Error message

Invalid CAB archive: unsupported LZX block type ${this.#blockType}

What it means

LZX block types are only 1 (verbatim), 2 (aligned offset), and 3 (uncompressed). #readBlockHeader encountered a block type outside that set, meaning the bitstream is misaligned or corrupt.

Source

Thrown at packages/utils/src/ar/codecs/lzx.ts:260

			this.#mainTable = new LzxHuffmanTable(this.#mainLengths);
			if (this.#mainLengths[0xe8] !== 0) this.#intelStarted = true;
			readCodeLengths(reader, this.#lengthLengths, 0, this.#lengthLengths.byteLength);
			this.#lengthTable = new LzxHuffmanTable(this.#lengthLengths, true);
			return;
		}
		if (this.#blockType === 3) {
			this.#intelStarted = true;
			reader.alignWord();
			this.#r0 = reader.readUInt32LE();
			this.#r1 = reader.readUInt32LE();
			this.#r2 = reader.readUInt32LE();
			if (this.#r0 === 0 || this.#r1 === 0 || this.#r2 === 0) {
				throw new ArchiveError("Invalid CAB archive: invalid LZX repeated offset");
			}
			this.#uncompressedPadding = (this.#blockLength & 1) !== 0;
			return;
		}
		throw new ArchiveError(`Invalid CAB archive: unsupported LZX block type ${this.#blockType}`);
	}

	#decodeRun(reader: LzxBitReader, output: Uint8Array, outputStart: number, count: number): number {
		if (this.#blockType === 3) {
			for (let index = 0; index < count; index++) this.#writeByte(reader.readByte(), output, outputStart + index);
			return count;
		}
		if (!this.#mainTable || !this.#lengthTable)
			throw new ArchiveError("Invalid CAB archive: missing LZX decode trees");

		let produced = 0;
		while (produced < count) {
			const element = this.#mainTable.decode(reader);
			if (element < 256) {
				this.#writeByte(element, output, outputStart + produced);
				produced++;
				continue;
			}

View on GitHub (pinned to 9690622007)

Solutions

Re-extract or re-download the CAB archive.
Check that decompression starts at the correct byte offset (bit alignment at frame start).
Fail fast on ArchiveError; do not attempt to resynchronize mid-frame.

Defensive patterns

Strategy: try-catch

Try / catch

try {
  decompressFrame(reader);
} catch (err) {
  if (err instanceof ArchiveError && /unsupported LZX block type/.test(err.message)) {
    throw new Error("CAB payload is corrupt or not LZX");
  }
  throw err;
}

Prevention

Start decoding at a byte-aligned frame boundary
Reject archives failing integrity checks early
Never resume decoding from a mid-stream offset

When it happens

Trigger: decompressFrame -> #readBlockHeader reads a block type byte that is not 1, 2, or 3.

Common situations: Bit-reader desync from earlier bad data in the same frame, corrupt CAB payload, or feeding non-LZX bytes into the LZX decoder.

Related errors

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/42d9e66579ce4812. Report an issue: GitHub.