velt/hash#

import { fnv1a64 } from "velt/hash". A stable, non-cryptographic hash for sharding, bucketing and consistent hashing.

import { fnv1a64 } from "velt/hash";

function shardOf(key: string, shards: u64): u64 {
  return fnv1a64(key) % shards;
}

console.log(fnv1a64("foobar")); // 9625390261332436968
console.log(shardOf("user:1", 16)); // 11

• fnv1a64(s: string): u64: the 64-bit FNV-1a hash of the UTF-8 bytes of s.
• fnv1a64Bytes(data: u8[]): u64: the same hash of a byte array, so fnv1a64(s) == fnv1a64Bytes(utf8Encode(s)).

Stable. The algorithm is fixed and not seeded, so a value is the same on every platform, in every run and in every Velt version. It is safe to store, or to share between processes that must agree on where a key lives.

Not DoS-resistant. Anyone can compute colliding keys. Don't use it for a hash table whose keys an attacker chooses, and never for security; use velt/crypto there. The prelude's Map hashes keys its own way, and that hash is not part of any contract.