ParagonIE_Sodium_Core32_Poly1305_State::__construct

    public function __construct($key = '')
    {
        if (self::strlen($key) < 32) {
            throw new InvalidArgumentException(
                'Poly1305 requires a 32-byte key'
            );
        }
        /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
        $this->r = array(
            // st->r[0] = ...
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 0, 4))
                ->setUnsignedInt(true)
                ->mask(0x3ffffff),
            // st->r[1] = ...
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 3, 4))
                ->setUnsignedInt(true)
                ->shiftRight(2)
                ->mask(0x3ffff03),
            // st->r[2] = ...
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 6, 4))
                ->setUnsignedInt(true)
                ->shiftRight(4)
                ->mask(0x3ffc0ff),
            // st->r[3] = ...
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 9, 4))
                ->setUnsignedInt(true)
                ->shiftRight(6)
                ->mask(0x3f03fff),
            // st->r[4] = ...
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 12, 4))
                ->setUnsignedInt(true)
                ->shiftRight(8)
                ->mask(0x00fffff)
        );

        /* h = 0 */
        $this->h = array(
            new ParagonIE_Sodium_Core32_Int32(array(0, 0), true),
            new ParagonIE_Sodium_Core32_Int32(array(0, 0), true),
            new ParagonIE_Sodium_Core32_Int32(array(0, 0), true),
            new ParagonIE_Sodium_Core32_Int32(array(0, 0), true),
            new ParagonIE_Sodium_Core32_Int32(array(0, 0), true)
        );

        /* save pad for later */
        $this->pad = array(
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 16, 4))
                ->setUnsignedInt(true)->toInt64(),
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 20, 4))
                ->setUnsignedInt(true)->toInt64(),
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 24, 4))
                ->setUnsignedInt(true)->toInt64(),
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 28, 4))
                ->setUnsignedInt(true)->toInt64(),
        );

        $this->leftover = 0;
        $this->final = false;
    }