src/includes/classes/Core/Utils/Sha1Mod.php
public function shardId(string $string, bool $is_sha1 = false, int $total_shards = 65536): int
    {
        return $this->__invoke($string, $total_shards, $is_sha1);
    }
public function shardId(string $string, bool $is_sha1 = false, int $total_shards = 65536): int
    {
        return $this->__invoke($string, $total_shards, $is_sha1);
    }
SHA-1 modulus shard ID.

@since 150424 SHA-1 modulus.

@param string $string       String or a SHA-1 hash.
@param bool   $is_sha1      String is already a SHA-1 hash?
@param int    $total_shards Total shards; defaults to `65536`.

@return int SHA-1 modulus; i.e., a shard ID.

@internal Shard IDs are always zero-based, because a modulus will never be >= to the divisor.
If `$total_shards is `65536`, min shard ID is `0`, max shard ID is `65535`.