ParagonIE_Sodium_Core_BLAKE2b::compress

    protected static function compress(SplFixedArray $ctx, SplFixedArray $buf)
    {
        $m = new SplFixedArray(16);
        $v = new SplFixedArray(16);

        for ($i = 16; $i--;) {
            $m[$i] = self::load64($buf, $i << 3);
        }

        for ($i = 8; $i--;) {
            $v[$i] = $ctx[0][$i];
        }

        $v[ 8] = self::$iv[0];
        $v[ 9] = self::$iv[1];
        $v[10] = self::$iv[2];
        $v[11] = self::$iv[3];

        $v[12] = self::xor64($ctx[1][0], self::$iv[4]);
        $v[13] = self::xor64($ctx[1][1], self::$iv[5]);
        $v[14] = self::xor64($ctx[2][0], self::$iv[6]);
        $v[15] = self::xor64($ctx[2][1], self::$iv[7]);

        for ($r = 0; $r < 12; ++$r) {
            $v = self::G($r, 0, 0, 4, 8, 12, $v, $m);
            $v = self::G($r, 1, 1, 5, 9, 13, $v, $m);
            $v = self::G($r, 2, 2, 6, 10, 14, $v, $m);
            $v = self::G($r, 3, 3, 7, 11, 15, $v, $m);
            $v = self::G($r, 4, 0, 5, 10, 15, $v, $m);
            $v = self::G($r, 5, 1, 6, 11, 12, $v, $m);
            $v = self::G($r, 6, 2, 7, 8, 13, $v, $m);
            $v = self::G($r, 7, 3, 4, 9, 14, $v, $m);
        }

        for ($i = 8; $i--;) {
            $ctx[0][$i] = self::xor64(
                $ctx[0][$i], self::xor64($v[$i], $v[$i+8])
            );
        }
    }