d1->addInt64($c);

            $c = $d1->shiftRight(26);
            $h1 = $d1->toInt32()->mask(0x3ffffff);
            $d2 = $d2->addInt64($c);

            $c = $d2->shiftRight(26);
            $h2 = $d2->toInt32()->mask(0x3ffffff);
            $d3 = $d3->addInt64($c);

            $c = $d3->shiftRight(26);
            $h3 = $d3->toInt32()->mask(0x3ffffff);
            $d4 = $d4->addInt64($c);

            $c = $d4->shiftRight(26);
            $h4 = $d4->toInt32()->mask(0x3ffffff);
            $h0 = $h0->addInt32($c->toInt32()->mulInt(5, 3));

            $c = $h0->shiftRight(26);
            $h0 = $h0->mask(0x3ffffff);
            $h1 = $h1->addInt32($c);

            // Chop off the left 32 bytes.
            $message = self::substr(
                $message,
                ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE
            );
            $bytes -= ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE;
        }

        /** @var array<int, ParagonIE_Sodium_Core32_Int32> $h */
        $this->h = array($h0, $h1, $h2, $h3, $h4);
        return $this;
    }

    /**
     * @internal You should not use this directly from another application
     *
     * @return string
     * @throws Sodiu