can1357/oh-my-pi · error · ArchiveError

Invalid CAB archive: LZX position slot is out of range

Error message

Invalid CAB archive: LZX position slot is out of range

What it means

The decoded match's position slot indexes beyond the precomputed positionBase/extraBits tables. Valid LZX position slots are bounded by the window size; an out-of-range slot means the Huffman-decoded symbol stream is corrupt.

Source

Thrown at packages/utils/src/ar/codecs/lzx.ts:302

			if (matchLength > count - produced || matchLength > this.#blockRemaining - produced) {
				throw new ArchiveError("Invalid CAB archive: LZX match crosses a frame or block boundary");
			}

			const slot = match >>> 3;
			let matchOffset: number;
			if (slot === 0) {
				matchOffset = this.#r0;
			} else if (slot === 1) {
				matchOffset = this.#r1;
				this.#r1 = this.#r0;
				this.#r0 = matchOffset;
			} else if (slot === 2) {
				matchOffset = this.#r2;
				this.#r2 = this.#r0;
				this.#r0 = matchOffset;
			} else {
				if (slot >= this.#positionBase.byteLength)
					throw new ArchiveError("Invalid CAB archive: LZX position slot is out of range");
				const extra = this.#extraBits[slot]!;
				matchOffset = this.#positionBase[slot]! - 2;
				if (this.#blockType === 2 && extra >= 3) {
					if (extra > 3) matchOffset += reader.readBits(extra - 3) * 8;
					if (!this.#alignedTable) throw new ArchiveError("Invalid CAB archive: missing LZX aligned tree");
					matchOffset += this.#alignedTable.decode(reader);
				} else if (extra !== 0) {
					matchOffset += reader.readBits(extra);
				}
				this.#r2 = this.#r1;
				this.#r1 = this.#r0;
				this.#r0 = matchOffset;
			}

			if (matchOffset <= 0 || matchOffset > Math.min(this.#decodedSize, this.#window.byteLength)) {
				throw new ArchiveError("Invalid CAB archive: LZX match offset exceeds available history");
			}
			for (let index = 0; index < matchLength; index++) {

View on GitHub (pinned to 9690622007)

Solutions

1. Re-validate/re-download the CAB archive.
2. Confirm the window size used to initialize the decoder matches the folder's LZX window bits.
3. Treat as unrecoverable corruption and surface ArchiveError.

// ensure decoder window matches folder params
function windowBitsValid(windowBits) { return windowBits >= 15 && windowBits <= 23; }

try {
  const out = decompressFrame(frame);
} catch (err) {
  if (err instanceof ArchiveError && err.message.includes("position slot")) {
    // bitstream desync or unsupported window — treat file as corrupt
  } else throw err;
}

When it happens

Trigger: decompressFrame -> #decodeRun computes slot = match >>> 3 and slot >= positionBase.byteLength for a non-repeated-offset match.

Common situations: Corrupt CAB payloads or bitstream desync causing garbage Huffman symbols; archives compressed with parameters the decoder doesn't expect.

Related errors

• Invalid CAB archive: misaligned LZX byte stream
• Invalid CAB archive: invalid LZX Huffman code length
• Invalid CAB archive: invalid LZX repeated offset
• Invalid CAB archive: unsupported LZX block type ${this.#bloc
• Invalid CAB archive: LZX match crosses a frame or block boun

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/6b4edaf6faae3515. Report an issue: GitHub.