ParagonIE_Sodium_Core32_Int32::mulInt

    public function mulInt($int = 0, $size = 0)
    {
        ParagonIE_Sodium_Core32_Util::declareScalarType($int, 'int', 1);
        ParagonIE_Sodium_Core32_Util::declareScalarType($size, 'int', 2);
        if (ParagonIE_Sodium_Compat::$fastMult) {
            return $this->mulIntFast((int) $int);
        }
        /** @var int $int */
        $int = (int) $int;
        /** @var int $size */
        $size = (int) $size;

        if (!$size) {
            $size = 31;
        }
        /** @var int $size */

        $a = clone $this;
        $return = new ParagonIE_Sodium_Core32_Int32();
        $return->unsignedInt = $this->unsignedInt;

        // Initialize:
        $ret0 = 0;
        $ret1 = 0;
        $a0 = $a->limbs[0];
        $a1 = $a->limbs[1];

        /** @var int $size */
        /** @var int $i */
        for ($i = $size; $i >= 0; --$i) {
            $m = (int) (-($int & 1));
            $x0 = $a0 & $m;
            $x1 = $a1 & $m;

            $ret1 += $x1;
            $c = $ret1 >> 16;

            $ret0 += $x0 + $c;

            $ret0 &= 0xffff;
            $ret1 &= 0xffff;

            $a1 = ($a1 << 1);
            $x1 = $a1 >> 16;
            $a0 = ($a0 << 1) | $x1;
            $a0 &= 0xffff;
            $a1 &= 0xffff;
            $int >>= 1;
        }
        $return->limbs[0] = $ret0;
        $return->limbs[1] = $ret1;
        return $return;
    }