v2.0.6 - Seeded XXH3

This release adds optional seeded XXH3-64 / XXH3-128 support.

A seed is useful when an app needs reproducible non-cryptographic checksums
across a backend, CLI tooling, and React Native. For example, a backend can
publish both the expected XXH3 digest and the exact u64 seed used to compute
it; the mobile app can then hash the downloaded local file with the same seed
and compare the result.

Seeded XXH3 is also useful for app-owned cache or deduplication namespaces,
such as media-cache-v1 or upload-dedupe-v2, where the same bytes should
produce stable hashes within that namespace.

Seeds are not secrets and do not make XXH3 cryptographic. Use HMAC or keyed
BLAKE3 when authenticity matters.

Added

• Added hashOptions.seed for XXH3-64 and XXH3-128 in both fileHash and
  stringHash.
• hashOptions.seed accepts:
  • bigint
  • non-negative safe integer number
  • decimal string
  • 0x hex string
• Added xxh3SeedFromLabel(label) for deterministic UTF-8 label -> u64 seed
  derivation using FNV-1a 64-bit. It returns a canonical 0x hex seed that can
  be passed directly to hashOptions.seed.
• Added seeded XXH3 coverage to the example app, including label, string,
  number, and bigint seed inputs.
• Added seeded XXH3 validation and vector tests.

Usage

Pass large u64 seeds from a backend as strings so JavaScript does not round
them:

const manifest = {
  xxh3Seed: '12345678901234567890',
  xxh3: '4b5e0a417dfa7ed2fb965bc17c16bd34',
};

const actual = await fileHash(localFileUri, {
  algorithm: 'XXH3-128',
  hashOptions: {
    seed: manifest.xxh3Seed,
  },
});

if (actual !== manifest.xxh3) {
  throw new Error('Downloaded file failed checksum verification');
}

For app-owned namespaces, derive a stable seed from a readable label:

const seed = xxh3SeedFromLabel('media-cache-v1');

const cacheKey = await fileHash(fileUri, {
  algorithm: 'XXH3-128',
  hashOptions: { seed },
});

Compatibility

• hashOptions.seed is optional. Omit it for regular unseeded XXH3.
• hashOptions.seed is only valid for XXH3-64 and XXH3-128; other
  algorithms reject it.
• Large seeds above Number.MAX_SAFE_INTEGER should be passed as bigint,
  decimal string, or 0x hex string.
• With the optional zig engine, seeded XXH3 currently means XXH3-64;
  XXH3-128 remains native-only.