<?php

if (class_exists('ParagonIE_Sodium_Core_ChaCha20_IetfCtx', false)) {
    return;
}




class ParagonIE_Sodium_Core_ChaCha20_IetfCtx extends ParagonIE_Sodium_Core_ChaCha20_Ctx
{
    











    public function __construct($key = '', $iv = '', $counter = '')
    {
        if (self::strlen($iv) !== 12) {
            throw new InvalidArgumentException('ChaCha20 expects a 96-bit nonce in IETF mode.');
        }
        $counter = $this->initCounter($counter);
        parent::__construct($key, self::substr($iv, 0, 8), $counter);
        $this->container[12] = self::load_4(self::substr($counter, 0, 4));
        $this->container[13] = self::load_4(self::substr($iv, 0, 4));
        $this->container[14] = self::load_4(self::substr($iv, 4, 4));
        $this->container[15] = self::load_4(self::substr($iv, 8, 4));
    }
}
