ParagonIE_Sodium_Core32_Poly1305_State::finish

    public function finish()
    {
        /* process the remaining block */
        if ($this->leftover) {
            $i = $this->leftover;
            $this->buffer[$i++] = 1;
            for (; $i < ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE; ++$i) {
                $this->buffer[$i] = 0;
            }
            $this->final = true;
            $this->blocks(
                self::substr(
                    self::intArrayToString($this->buffer),
                    0,
                    ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE
                ),
                $b = ParagonIE_Sodium_Core32_Poly1305::BLOCK_SIZE
            );
        }

        /**
         * @var ParagonIE_Sodium_Core32_Int32 $f
         * @var ParagonIE_Sodium_Core32_Int32 $g0
         * @var ParagonIE_Sodium_Core32_Int32 $g1
         * @var ParagonIE_Sodium_Core32_Int32 $g2
         * @var ParagonIE_Sodium_Core32_Int32 $g3
         * @var ParagonIE_Sodium_Core32_Int32 $g4
         * @var ParagonIE_Sodium_Core32_Int32 $h0
         * @var ParagonIE_Sodium_Core32_Int32 $h1
         * @var ParagonIE_Sodium_Core32_Int32 $h2
         * @var ParagonIE_Sodium_Core32_Int32 $h3
         * @var ParagonIE_Sodium_Core32_Int32 $h4
         */
        $h0 = $this->h[0];
        $h1 = $this->h[1];
        $h2 = $this->h[2];
        $h3 = $this->h[3];
        $h4 = $this->h[4];

        $c = $h1->shiftRight(26);           # $c = $h1 >> 26;
        $h1 = $h1->mask(0x3ffffff);         # $h1 &= 0x3ffffff;

        $h2 = $h2->addInt32($c);            # $h2 += $c;
        $c = $h2->shiftRight(26);           # $c = $h2 >> 26;
        $h2 = $h2->mask(0x3ffffff);         # $h2 &= 0x3ffffff;

        $h3 = $h3->addInt32($c);            # $h3 += $c;
        $c = $h3->shiftRight(26);           # $c = $h3 >> 26;
        $h3 = $h3->mask(0x3ffffff);         # $h3 &= 0x3ffffff;

        $h4 = $h4->addInt32($c);            # $h4 += $c;
        $c = $h4->shiftRight(26);           # $c = $h4 >> 26;
        $h4 = $h4->mask(0x3ffffff);         # $h4 &= 0x3ffffff;

        $h0 = $h0->addInt32($c->mulInt(5, 3)); # $h0 += self::mul($c, 5);
        $c = $h0->shiftRight(26);           # $c = $h0 >> 26;
        $h0 = $h0->mask(0x3ffffff);         # $h0 &= 0x3ffffff;
        $h1 = $h1->addInt32($c);            # $h1 += $c;

        /* compute h + -p */
        $g0 = $h0->addInt(5);
        $c  = $g0->shiftRight(26);
        $g0 = $g0->mask(0x3ffffff);
        $g1 = $h1->addInt32($c);
        $c  = $g1->shiftRight(26);
        $g1 = $g1->mask(0x3ffffff);
        $g2 = $h2->addInt32($c);
        $c  = $g2->shiftRight(26);
        $g2 = $g2->mask(0x3ffffff);
        $g3 = $h3->addInt32($c);
        $c  = $g3->shiftRight(26);
        $g3 = $g3->mask(0x3ffffff);
        $g4 = $h4->addInt32($c)->subInt(1 << 26);

        # $mask = ($g4 >> 31) - 1;
        /* select h if h < p, or h + -p if h >= p */
        $mask = (int) (($g4->toInt() >> 31) + 1);

        $g0 = $g0->mask($mask);
        $g1 = $g1->mask($mask);
        $g2 = $g2->mask($mask);
        $g3 = $g3->mask($mask);
        $g4 = $g4->mask($mask);

        /** @var int $mask */
        $mask = (~$mask) & 0xffffffff;

        $h0 = $h0->mask($mask)->orInt32($g0);
        $h1 = $h1->mask($mask)->orInt32($g1);
        $h2 = $h2->mask($mask)->orInt32($g2);
        $h3 = $h3->mask($mask)->orInt32($g3);
        $h4 = $h4->mask($mask)->orInt32($g4);

        /* h = h % (2^128) */
        $h0 = $h0->orInt32($h1->shiftLeft(26));
        $h1 = $h1->shiftRight(6)->orInt32($h2->shiftLeft(20));
        $h2 = $h2->shiftRight(12)->orInt32($h3->shiftLeft(14));
        $h3 = $h3->shiftRight(18)->orInt32($h4->shiftLeft(8));

        /* mac = (h + pad) % (2^128) */
        $f = $h0->toInt64()->addInt64($this->pad[0]);
        $h0 = $f->toInt32();
        $f = $h1->toInt64()->addInt64($this->pad[1])->addInt($h0->overflow);
        $h1 = $f->toInt32();
        $f = $h2->toInt64()->addInt64($this->pad[2])->addInt($h1->overflow);
        $h2 = $f->toInt32();
        $f = $h3->toInt64()->addInt64($this->pad[3])->addInt($h2->overflow);
        $h3 = $f->toInt32();

        return $h0->toReverseString() .
            $h1->toReverseString() .
            $h2->toReverseString() .
            $h3->toReverseString();
    }