Function placement_hash

nodedb-cluster/src/catalog/cluster_settings.rs:90–103

Dispatch a key through the configured placement hash, returning a deterministic 64-bit value. The caller is responsible for reducing the output into a vShard ID (e.g. `% vshard_count`).

(id: PlacementHashId, key: &[u8])

/// deterministic 64-bit value. The caller is responsible for reducing
/// the output into a vShard ID (e.g. `% vshard_count`).
pub fn placement_hash(id: PlacementHashId, key: &[u8]) -> u64 {
    match id {
        PlacementHashId::Fnv1a => {
            // FNV-1a 64-bit (offset basis 0xcbf29ce484222325, prime 0x100000001b3).
            let mut hash: u64 = 0xcbf29ce484222325;
            for byte in key {
                hash ^= *byte as u64;
                hash = hash.wrapping_mul(0x100000001b3);
            }
            hash
        }
        PlacementHashId::XxHash3 => xxhash_rust::xxh3::xxh3_64(key),
    }
}

// ── ClusterCatalog methods ───────────────────────────────────────────────────