<?php

if (class_exists('ParagonIE_Sodium_Core_Salsa20', false)) {

    return;

}

/**

 * Class ParagonIE_Sodium_Core_Salsa20

 */

abstract class ParagonIE_Sodium_Core_Salsa20 extends ParagonIE_Sodium_Core_Util

{

    const ROUNDS = 20;

    /**

     * Calculate an salsa20 hash of a single block

     *

     * @internal You should not use this directly from another application

     *

     * @param string $in

     * @param string $k

     * @param string|null $c

     * @return string

     * @throws TypeError

     */

    public static function core_salsa20($in, $k, $c = null)

    {

        if (self::strlen($k) < 32) {

            throw new RangeException('Key must be 32 bytes long');

        }

        if ($c === null) {

            $j0  = $x0  = 0x61707865;

            $j5  = $x5  = 0x3320646e;

            $j10 = $x10 = 0x79622d32;

            $j15 = $x15 = 0x6b206574;

        } else {

            $j0  = $x0  = self::load_4(self::substr($c, 0, 4));

            $j5  = $x5  = self::load_4(self::substr($c, 4, 4));

            $j10 = $x10 = self::load_4(self::substr($c, 8, 4));

            $j15 = $x15 = self::load_4(self::substr($c, 12, 4));

        }

        $j1  = $x1  = self::load_4(self::substr($k, 0, 4));

        $j2  = $x2  = self::load_4(self::substr($k, 4, 4));

        $j3  = $x3  = self::load_4(self::substr($k, 8, 4));

        $j4  = $x4  = self::load_4(self::substr($k, 12, 4));

        $j6  = $x6  = self::load_4(self::substr($in, 0, 4));

        $j7  = $x7  = self::load_4(self::substr($in, 4, 4));

        $j8  = $x8  = self::load_4(self::substr($in, 8, 4));

        $j9  = $x9  = self::load_4(self::substr($in, 12, 4));

        $j11 = $x11 = self::load_4(self::substr($k, 16, 4));

        $j12 = $x12 = self::load_4(self::substr($k, 20, 4));

        $j13 = $x13 = self::load_4(self::substr($k, 24, 4));

        $j14 = $x14 = self::load_4(self::substr($k, 28, 4));

        for ($i = self::ROUNDS; $i > 0; $i -= 2) {

            $x4 ^= self::rotate($x0 + $x12, 7);

            $x8 ^= self::rotate($x4 + $x0, 9);

            $x12 ^= self::rotate($x8 + $x4, 13);

            $x0 ^= self::rotate($x12 + $x8, 18);

            $x9 ^= self::rotate($x5 + $x1, 7);

            $x13 ^= self::rotate($x9 + $x5, 9);

            $x1 ^= self::rotate($x13 + $x9, 13);

            $x5 ^= self::rotate($x1 + $x13, 18);

            $x14 ^= self::rotate($x10 + $x6, 7);

            $x2 ^= self::rotate($x14 + $x10, 9);

            $x6 ^= self::rotate($x2 + $x14, 13);

            $x10 ^= self::rotate($x6 + $x2, 18);

            $x3 ^= self::rotate($x15 + $x11, 7);

            $x7 ^= self::rotate($x3 + $x15, 9);

            $x11 ^= self::rotate($x7 + $x3, 13);

            $x15 ^= self::rotate($x11 + $x7, 18);

            $x1 ^= self::rotate($x0 + $x3, 7);

            $x2 ^= self::rotate($x1 + $x0, 9);

            $x3 ^= self::rotate($x2 + $x1, 13);

            $x0 ^= self::rotate($x3 + $x2, 18);

            $x6 ^= self::rotate($x5 + $x4, 7);

            $x7 ^= self::rotate($x6 + $x5, 9);

            $x4 ^= self::rotate($x7 + $x6, 13);

            $x5 ^= self::rotate($x4 + $x7, 18);

            $x11 ^= self::rotate($x10 + $x9, 7);

            $x8 ^= self::rotate($x11 + $x10, 9);

            $x9 ^= self::rotate($x8 + $x11, 13);

            $x10 ^= self::rotate($x9 + $x8, 18);

            $x12 ^= self::rotate($x15 + $x14, 7);

            $x13 ^= self::rotate($x12 + $x15, 9);

            $x14 ^= self::rotate($x13 + $x12, 13);

            $x15 ^= self::rotate($x14 + $x13, 18);

        }

        $x0  += $j0;

        $x1  += $j1;

        $x2  += $j2;

        $x3  += $j3;

        $x4  += $j4;

        $x5  += $j5;

        $x6  += $j6;

        $x7  += $j7;

        $x8  += $j8;

        $x9  += $j9;

        $x10 += $j10;

        $x11 += $j11;

        $x12 += $j12;

        $x13 += $j13;

        $x14 += $j14;

        $x15 += $j15;

        return self::store32_le($x0) .

            self::store32_le($x1) .

            self::store32_le($x2) .

            self::store32_le($x3) .

            self::store32_le($x4) .

            self::store32_le($x5) .

            self::store32_le($x6) .

            self::store32_le($x7) .

            self::store32_le($x8) .

            self::store32_le($x9) .

            self::store32_le($x10) .

            self::store32_le($x11) .

            self::store32_le($x12) .

            self::store32_le($x13) .

            self::store32_le($x14) .

            self::store32_le($x15);

    }

    /**

     * @internal You should not use this directly from another application

     *

     * @param int $len

     * @param string $nonce

     * @param string $key

     * @return string

     * @throws SodiumException

     * @throws TypeError

     */

    public static function salsa20($len, $nonce, $key)

    {

        if (self::strlen($key) !== 32) {

            throw new RangeException('Key must be 32 bytes long');

        }

        $kcopy = '' . $key;

        $in = self::substr($nonce, 0, 8) . str_repeat("\0", 8);

        $c = '';

        while ($len >= 64) {

            $c .= self::core_salsa20($in, $kcopy, null);

            $u = 1;

            // Internal counter.

            for ($i = 8; $i < 16; ++$i) {

                $u += self::chrToInt($in[$i]);

                $in[$i] = self::intToChr($u & 0xff);

                $u >>= 8;

            }

            $len -= 64;

        }

        if ($len > 0) {

            $c .= self::substr(

                self::core_salsa20($in, $kcopy, null),

                0,

                $len

            );

        }

        try {

            ParagonIE_Sodium_Compat::memzero($kcopy);

        } catch (SodiumException $ex) {

            $kcopy = null;

        }

        return $c;

    }

    /**

     * @internal You should not use this directly from another application

     *

     * @param string $m

     * @param string $n

     * @param int $ic

     * @param string $k

     * @return string

     * @throws SodiumException

     * @throws TypeError

     */

    public static function salsa20_xor_ic($m, $n, $ic, $k)

    {

        $mlen = self::strlen($m);

        if ($mlen < 1) {

            return '';

        }

        $kcopy = self::substr($k, 0, 32);

        $in = self::substr($n, 0, 8);

        // Initialize the counter

        $in .= ParagonIE_Sodium_Core_Util::store64_le($ic);

        $c = '';

        while ($mlen >= 64) {

            $block = self::core_salsa20($in, $kcopy, null);

            $c .= self::xorStrings(

                self::substr($m, 0, 64),

                self::substr($block, 0, 64)

            );

            $u = 1;

            for ($i = 8; $i < 16; ++$i) {

                $u += self::chrToInt($in[$i]);

                $in[$i] = self::intToChr($u & 0xff);

                $u >>= 8;

            }

            $mlen -= 64;

            $m = self::substr($m, 64);

        }

        if ($mlen) {

            $block = self::core_salsa20($in, $kcopy, null);

            $c .= self::xorStrings(

                self::substr($m, 0, $mlen),

                self::substr($block, 0, $mlen)

            );

        }

        try {

            ParagonIE_Sodium_Compat::memzero($block);

            ParagonIE_Sodium_Compat::memzero($kcopy);

        } catch (SodiumException $ex) {

            $block = null;

            $kcopy = null;

        }

        return $c;

    }

    /**

     * @internal You should not use this directly from another application

     *

     * @param string $message

     * @param string $nonce

     * @param string $key

     * @return string

     * @throws SodiumException

     * @throws TypeError

     */

    public static function salsa20_xor($message, $nonce, $key)

    {

        return self::xorStrings(

            $message,

            self::salsa20(

                self::strlen($message),

                $nonce,

                $key

            )

        );

    }

    /**

     * @internal You should not use this directly from another application

     *

     * @param int $u

     * @param int $c

     * @return int

     */

    public static function rotate($u, $c)

    {

        $u &= 0xffffffff;

        $c %= 32;

        return (int) (0xffffffff & (

                ($u << $c)

                    |

                ($u >> (32 - $c))

            )

        );

    }

}