ParagonIE_Sodium_Core_ChaCha20_Ctx

10class ParagonIE_Sodium_Core_ChaCha20_Ctx extends ParagonIE_Sodium_Core_Util implements ArrayAccess11{12    /**13     * @var SplFixedArray internally, <int, int>14     */15    protected $container;16 17    /**18     * ParagonIE_Sodium_Core_ChaCha20_Ctx constructor.19     *20     * @internal You should not use this directly from another application21     *22     * @param string $key     ChaCha20 key.23     * @param string $iv      Initialization Vector (a.k.a. nonce).24     * @param string $counter The initial counter value.25     *                        Defaults to 8 0x00 bytes.26     * @throws InvalidArgumentException27     * @throws TypeError28     */29    public function __construct($key = '', $iv = '', $counter = '')30    {31        if (self::strlen($key) !== 32) {32            throw new InvalidArgumentException('ChaCha20 expects a 256-bit key.');33        }34        if (self::strlen($iv) !== 8) {35            throw new InvalidArgumentException('ChaCha20 expects a 64-bit nonce.');36        }37        $this->container = new SplFixedArray(16);38 39        /* "expand 32-byte k" as per ChaCha20 spec */40        $this->container[0]  = 0x61707865;41        $this->container[1]  = 0x3320646e;42        $this->container[2]  = 0x79622d32;43        $this->container[3]  = 0x6b206574;44        $this->container[4]  = self::load_4(self::substr($key, 0, 4));45        $this->container[5]  = self::load_4(self::substr($key, 4, 4));46        $this->container[6]  = self::load_4(self::substr($key, 8, 4));47        $this->container[7]  = self::load_4(self::substr($key, 12, 4));48        $this->container[8]  = self::load_4(self::substr($key, 16, 4));49        $this->container[9]  = self::load_4(self::substr($key, 20, 4));50        $this->container[10] = self::load_4(self::substr($key, 24, 4));51        $this->container[11] = self::load_4(self::substr($key, 28, 4));52 53        $counter = $this->initCounter($counter);54        $this->container[12] = self::load_4(self::substr($counter, 0, 4));55        $this->container[13] = self::load_4(self::substr($counter, 4, 4));56        $this->container[14] = self::load_4(self::substr($iv, 0, 4));57        $this->container[15] = self::load_4(self::substr($iv, 4, 4));58    }59 60    /**61     * @internal You should not use this directly from another application62     *63     * @param int $offset64     * @param int $value65     * @return void66     * @psalm-suppress MixedArrayOffset67     */68    #[ReturnTypeWillChange]69    public function offsetSet($offset, $value)70    {71        if (!is_int($offset)) {72            throw new InvalidArgumentException('Expected an integer');73        }74        if (!is_int($value)) {75            throw new InvalidArgumentException('Expected an integer');76        }77        $this->container[$offset] = $value;78    }79 80    /**81     * @internal You should not use this directly from another application82     *83     * @param int $offset84     * @return bool85     */86    #[ReturnTypeWillChange]87    public function offsetExists($offset)88    {89        return isset($this->container[$offset]);