1<?php 2 3/** 4 * webtrees: online genealogy 5 * Copyright (C) 2021 webtrees development team 6 * This program is free software: you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation, either version 3 of the License, or 9 * (at your option) any later version. 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * You should have received a copy of the GNU General Public License 15 * along with this program. If not, see <https://www.gnu.org/licenses/>. 16 */ 17 18declare(strict_types=1); 19 20namespace Fisharebest\Webtrees\Elements; 21 22use Fisharebest\Webtrees\Tree; 23use Ramsey\Uuid\Exception\RandomSourceException; 24use Ramsey\Uuid\Uuid; 25 26use function dechex; 27use function hexdec; 28use function strtoupper; 29use function strtr; 30use function substr; 31 32/** 33 * _UID fields, as created by PAF and other applications 34 */ 35class PafUid extends AbstractElement 36{ 37 protected const MAXIMUM_LENGTH = 34; 38 39 /** 40 * Create a default value for this element. 41 * 42 * @param Tree $tree 43 * 44 * @return string 45 */ 46 public function default(Tree $tree): string 47 { 48 try { 49 $uid = strtr(Uuid::uuid4()->toString(), ['-' => '']); 50 } catch (RandomSourceException $ex) { 51 // uuid4() can fail if there is insufficient entropy in the system. 52 return ''; 53 } 54 55 $checksum_a = 0; // a sum of the bytes 56 $checksum_b = 0; // a sum of the incremental values of $checksum_a 57 58 // Compute checksums 59 for ($i = 0; $i < 32; $i += 2) { 60 $checksum_a += hexdec(substr($uid, $i, 2)); 61 $checksum_b += $checksum_a & 0xff; 62 } 63 64 $uid .= substr('0' . dechex($checksum_a), -2); 65 $uid .= substr('0' . dechex($checksum_b), -2); 66 67 return strtoupper($uid); 68 } 69} 70