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<?php
/**
* webtrees: online genealogy
* Copyright (C) 2021 webtrees development team
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
declare(strict_types=1);
namespace Fisharebest\Webtrees\Elements;
use Fisharebest\Webtrees\Tree;
use Ramsey\Uuid\Exception\RandomSourceException;
use Ramsey\Uuid\Uuid;
use function dechex;
use function hexdec;
use function strtoupper;
use function strtr;
use function substr;
/**
* _UID fields, as created by PAF and other applications
*/
class PafUid extends AbstractElement
{
protected const MAXIMUM_LENGTH = 34;
/**
* Create a default value for this element.
*
* @param Tree $tree
*
* @return string
*/
public function default(Tree $tree): string
{
try {
$uid = strtr(Uuid::uuid4()->toString(), ['-' => '']);
} catch (RandomSourceException $ex) {
// uuid4() can fail if there is insufficient entropy in the system.
return '';
}
$checksum_a = 0; // a sum of the bytes
$checksum_b = 0; // a sum of the incremental values of $checksum_a
// Compute checksums
for ($i = 0; $i < 32; $i += 2) {
$checksum_a += hexdec(substr($uid, $i, 2));
$checksum_b += $checksum_a & 0xff;
}
$uid .= substr('0' . dechex($checksum_a), -2);
$uid .= substr('0' . dechex($checksum_b), -2);
return strtoupper($uid);
}
}
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