can1357/oh-my-pi · error · ArchiveError

Unsupported RAR5 compression algorithm version ${version}

Error message

Unsupported RAR5 compression algorithm version ${version}

What it means

RAR5 archives store a per-file compression algorithm version; this decoder only implements versions 0 and 1. When a member header declares a newer algorithm version, the decoder refuses to guess and throws ArchiveError instead of producing corrupt output.

Source

Thrown at packages/utils/src/ar/rar/rar5-decoder.ts:168

		this.#history = new Uint8Array(0);
		this.#reps = [0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff];
		this.#lastLen = 0;
		this.#main = new Huffman(MAIN_SIZE);
		this.#dist = new Huffman(DIST_SIZE);
		this.#align = new Huffman(ALIGN_SIZE);
		this.#length = new Huffman(LEN_SIZE);
		this.#useAlign = false;
	}

	decode(
		packed: Uint8Array,
		unpackedSize: number,
		dictionarySize: number,
		solid: boolean,
		version: number,
	): Uint8Array {
		if (version !== 0 && version !== 1) {
			throw new ArchiveError(`Unsupported RAR5 compression algorithm version ${version}`);
		}
		if (!solid) this.reset();
		if (!Number.isSafeInteger(dictionarySize) || dictionarySize < 128 * 1024) fail("invalid dictionary size");
		const prior =
			this.#history.byteLength > dictionarySize
				? this.#history.subarray(this.#history.byteLength - dictionarySize)
				: this.#history;
		const data = new Uint8Array(prior.byteLength + unpackedSize + MAX_MATCH);
		data.set(prior);
		let outPos = prior.byteLength;
		const outStart = outPos;
		const outEnd = outStart + unpackedSize;
		const filters: Filter[] = [];
		const bits = new Bits(packed);
		const main = this.#main;
		const dist = this.#dist;
		const align = this.#align;
		const lenDecoder = this.#length;

View on GitHub (pinned to 9690622007)

Solutions

Re-create the archive with WinRAR/unrar using RAR5 compression (not the RAR7/new algorithm) or store with -m0
Upgrade to a decoder/library version that supports the newer RAR5 algorithm version
Extract the member with the official unrar/WinRAR tool and re-pack before feeding it to this library

Example fix

// before: archive made with WinRAR 7 defaults (RAR7 algorithm) fails to decode
// after: repack with RAR5-compatible compression
// $ rar a -ma5 -m3 output.rar files/

Defensive patterns

Strategy: try-catch

Validate before calling

// Pre-check RAR5 algorithm version from parsed metadata if available:
// records where format===5 and version>1 will fail
const risky = records.some(r => r.format === 5 && r.version > 1);
if (risky) console.warn('Archive uses unsupported RAR5 algorithm version; repack or use unrar');

Type guard

function isSupportedRar5Version(record: { format: number; version: number }): boolean {
  return record.format !== 5 || record.version === 0 || record.version === 1;
}

Try / catch

try {
  const bytes = await reader.read(memberPath);
} catch (err) {
  if (err instanceof ArchiveError && /algorithm version/.test(err.message)) {
    // fall back to external unrar tooling
  }
  throw err;
}

Prevention

Create archives with -ma5 (not -ma7) when they will be consumed by this library
Prefer standard compression methods (-m1..-m5) over newer algorithm variants
Test archives with `unrar t` in CI before processing them

When it happens

Trigger: Decoding a RAR5 member whose compression header field 'version' is >= 2 (or negative/garbage), typically via readRar/extracting an archive created by a newer RAR (RAR7+) using a newer compression algorithm.

Common situations: Opening archives produced by WinRAR 7.x with the new RAR7 compression format using a decoder that only supports RAR5 v0/v1; corrupted header bytes flipping the version field.

Related errors

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/c27e8ec5a6e7e84c. Report an issue: GitHub.