ParagonIE_Sodium_Core_Ed25519::small_order

    public static function small_order($R)
    {
        /** @var array<int, array<int, int>> $blocklist */
        $blocklist = array(
            /* 0 (order 4) */
            array(
                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
            ),
            /* 1 (order 1) */
            array(
                0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
            ),
            /* 2707385501144840649318225287225658788936804267575313519463743609750303402022 (order 8) */
            array(
                0x26, 0xe8, 0x95, 0x8f, 0xc2, 0xb2, 0x27, 0xb0,
                0x45, 0xc3, 0xf4, 0x89, 0xf2, 0xef, 0x98, 0xf0,
                0xd5, 0xdf, 0xac, 0x05, 0xd3, 0xc6, 0x33, 0x39,
                0xb1, 0x38, 0x02, 0x88, 0x6d, 0x53, 0xfc, 0x05
            ),
            /* 55188659117513257062467267217118295137698188065244968500265048394206261417927 (order 8) */
            array(
                0xc7, 0x17, 0x6a, 0x70, 0x3d, 0x4d, 0xd8, 0x4f,
                0xba, 0x3c, 0x0b, 0x76, 0x0d, 0x10, 0x67, 0x0f,
                0x2a, 0x20, 0x53, 0xfa, 0x2c, 0x39, 0xcc, 0xc6,
                0x4e, 0xc7, 0xfd, 0x77, 0x92, 0xac, 0x03, 0x7a
            ),
            /* p-1 (order 2) */
            array(
                0x13, 0xe8, 0x95, 0x8f, 0xc2, 0xb2, 0x27, 0xb0,
                0x45, 0xc3, 0xf4, 0x89, 0xf2, 0xef, 0x98, 0xf0,
                0xd5, 0xdf, 0xac, 0x05, 0xd3, 0xc6, 0x33, 0x39,
                0xb1, 0x38, 0x02, 0x88, 0x6d, 0x53, 0xfc, 0x85
            ),
            /* p (order 4) */
            array(
                0xb4, 0x17, 0x6a, 0x70, 0x3d, 0x4d, 0xd8, 0x4f,
                0xba, 0x3c, 0x0b, 0x76, 0x0d, 0x10, 0x67, 0x0f,
                0x2a, 0x20, 0x53, 0xfa, 0x2c, 0x39, 0xcc, 0xc6,
                0x4e, 0xc7, 0xfd, 0x77, 0x92, 0xac, 0x03, 0xfa
            ),
            /* p+1 (order 1) */
            array(
                0xec, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f
            ),
            /* p+2707385501144840649318225287225658788936804267575313519463743609750303402022 (order 8) */
            array(
                0xed, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f
            ),
            /* p+55188659117513257062467267217118295137698188065244968500265048394206261417927 (order 8) */
            array(
                0xee, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f
            ),
            /* 2p-1 (order 2) */
            array(
                0xd9, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
            ),
            /* 2p (order 4) */
            array(
                0xda, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
            ),
            /* 2p+1 (order 1) */
            array(
                0xdb, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
            )
        );
        /** @var int $countBlocklist */
        $countBlocklist = count($blocklist);

        for ($i = 0; $i < $countBlocklist; ++$i) {
            $c = 0;
            for ($j = 0; $j < 32; ++$j) {
                $c |= self::chrToInt($R[$j]) ^ (int) $blocklist[$i][$j];
            }
            if ($c === 0) {
                return true;
            }
        }
        return false;
    }