ParagonIE_Sodium_Core32_BLAKE2b::increment_counter

    public static function increment_counter($ctx, $inc)
    {
        if ($inc < 0) {
            throw new SodiumException('Increasing by a negative number makes no sense.');
        }
        $t = self::to64($inc);
        # S->t is $ctx[1] in our implementation

        # S->t[0] = ( uint64_t )( t >> 0 );
        $ctx[1][0] = self::add64($ctx[1][0], $t);

        # S->t[1] += ( S->t[0] < inc );
        if (!($ctx[1][0] instanceof ParagonIE_Sodium_Core32_Int64)) {
            throw new TypeError('Not an int64');
        }
        /** @var ParagonIE_Sodium_Core32_Int64 $c*/
        $c = $ctx[1][0];
        if ($c->isLessThanInt($inc)) {
            $ctx[1][1] = self::add64($ctx[1][1], self::to64(1));
        }
    }