<?php

if (class_exists('ParagonIE_Sodium_Core_HChaCha20', false)) {

    return;

}

/**

 * Class ParagonIE_Sodium_Core_HChaCha20

 */

class ParagonIE_Sodium_Core_HChaCha20 extends ParagonIE_Sodium_Core_ChaCha20

{

    /**

     * @param string $in

     * @param string $key

     * @param string|null $c

     * @return string

     * @throws TypeError

     */

    public static function hChaCha20($in = '', $key = '', $c = null)

    {

        $ctx = array();

        if ($c === null) {

            $ctx[0] = 0x61707865;

            $ctx[1] = 0x3320646e;

            $ctx[2] = 0x79622d32;

            $ctx[3] = 0x6b206574;

        } else {

            $ctx[0] = self::load_4(self::substr($c,  0, 4));

            $ctx[1] = self::load_4(self::substr($c,  4, 4));

            $ctx[2] = self::load_4(self::substr($c,  8, 4));

            $ctx[3] = self::load_4(self::substr($c, 12, 4));

        }

        $ctx[4]  = self::load_4(self::substr($key,  0, 4));

        $ctx[5]  = self::load_4(self::substr($key,  4, 4));

        $ctx[6]  = self::load_4(self::substr($key,  8, 4));

        $ctx[7]  = self::load_4(self::substr($key, 12, 4));

        $ctx[8]  = self::load_4(self::substr($key, 16, 4));

        $ctx[9]  = self::load_4(self::substr($key, 20, 4));

        $ctx[10] = self::load_4(self::substr($key, 24, 4));

        $ctx[11] = self::load_4(self::substr($key, 28, 4));

        $ctx[12] = self::load_4(self::substr($in,   0, 4));

        $ctx[13] = self::load_4(self::substr($in,   4, 4));

        $ctx[14] = self::load_4(self::substr($in,   8, 4));

        $ctx[15] = self::load_4(self::substr($in,  12, 4));

        return self::hChaCha20Bytes($ctx);

    }

    /**

     * @param array $ctx

     * @return string

     * @throws TypeError

     */

    protected static function hChaCha20Bytes(array $ctx)

    {

        $x0  = (int) $ctx[0];

        $x1  = (int) $ctx[1];

        $x2  = (int) $ctx[2];

        $x3  = (int) $ctx[3];

        $x4  = (int) $ctx[4];

        $x5  = (int) $ctx[5];

        $x6  = (int) $ctx[6];

        $x7  = (int) $ctx[7];

        $x8  = (int) $ctx[8];

        $x9  = (int) $ctx[9];

        $x10 = (int) $ctx[10];

        $x11 = (int) $ctx[11];

        $x12 = (int) $ctx[12];

        $x13 = (int) $ctx[13];

        $x14 = (int) $ctx[14];

        $x15 = (int) $ctx[15];

        for ($i = 0; $i < 10; ++$i) {

            # QUARTERROUND( x0,  x4,  x8,  x12)

            list($x0, $x4, $x8, $x12) = self::quarterRound($x0, $x4, $x8, $x12);

            # QUARTERROUND( x1,  x5,  x9,  x13)

            list($x1, $x5, $x9, $x13) = self::quarterRound($x1, $x5, $x9, $x13);

            # QUARTERROUND( x2,  x6,  x10,  x14)

            list($x2, $x6, $x10, $x14) = self::quarterRound($x2, $x6, $x10, $x14);

            # QUARTERROUND( x3,  x7,  x11,  x15)

            list($x3, $x7, $x11, $x15) = self::quarterRound($x3, $x7, $x11, $x15);

            # QUARTERROUND( x0,  x5,  x10,  x15)

            list($x0, $x5, $x10, $x15) = self::quarterRound($x0, $x5, $x10, $x15);

            # QUARTERROUND( x1,  x6,  x11,  x12)

            list($x1, $x6, $x11, $x12) = self::quarterRound($x1, $x6, $x11, $x12);

            # QUARTERROUND( x2,  x7,  x8,  x13)

            list($x2, $x7, $x8, $x13) = self::quarterRound($x2, $x7, $x8, $x13);

            # QUARTERROUND( x3,  x4,  x9,  x14)

            list($x3, $x4, $x9, $x14) = self::quarterRound($x3, $x4, $x9, $x14);

        }

        return self::store32_le((int) ($x0  & 0xffffffff)) .

            self::store32_le((int) ($x1  & 0xffffffff)) .

            self::store32_le((int) ($x2  & 0xffffffff)) .

            self::store32_le((int) ($x3  & 0xffffffff)) .

            self::store32_le((int) ($x12 & 0xffffffff)) .

            self::store32_le((int) ($x13 & 0xffffffff)) .

            self::store32_le((int) ($x14 & 0xffffffff)) .

            self::store32_le((int) ($x15 & 0xffffffff));

    }

}