about summary refs log blame commit diff stats
path: root/wiki/inc/changelog.php
blob: d77b0180a8fd96b26d19e7d4e2372b3983634b04 (plain) (tree)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059


































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































                                                                                                                                
<?php
/**
 * Changelog handling functions
 *
 * @license    GPL 2 (http://www.gnu.org/licenses/gpl.html)
 * @author     Andreas Gohr <andi@splitbrain.org>
 */

// Constants for known core changelog line types.
// Use these in place of string literals for more readable code.
define('DOKU_CHANGE_TYPE_CREATE',       'C');
define('DOKU_CHANGE_TYPE_EDIT',         'E');
define('DOKU_CHANGE_TYPE_MINOR_EDIT',   'e');
define('DOKU_CHANGE_TYPE_DELETE',       'D');
define('DOKU_CHANGE_TYPE_REVERT',       'R');

/**
 * parses a changelog line into it's components
 *
 * @author Ben Coburn <btcoburn@silicodon.net>
 *
 * @param string $line changelog line
 * @return array|bool parsed line or false
 */
function parseChangelogLine($line) {
    $line = rtrim($line, "\n");
    $tmp = explode("\t", $line);
    if ($tmp!==false && count($tmp)>1) {
        $info = array();
        $info['date']  = (int)$tmp[0]; // unix timestamp
        $info['ip']    = $tmp[1]; // IPv4 address (127.0.0.1)
        $info['type']  = $tmp[2]; // log line type
        $info['id']    = $tmp[3]; // page id
        $info['user']  = $tmp[4]; // user name
        $info['sum']   = $tmp[5]; // edit summary (or action reason)
        $info['extra'] = $tmp[6]; // extra data (varies by line type)
        if(isset($tmp[7]) && $tmp[7] !== '') { //last item has line-end||
            $info['sizechange'] = (int) $tmp[7];
        } else {
            $info['sizechange'] = null;
        }
        return $info;
    } else {
        return false;
    }
}

/**
 * Add's an entry to the changelog and saves the metadata for the page
 *
 * @param int    $date      Timestamp of the change
 * @param String $id        Name of the affected page
 * @param String $type      Type of the change see DOKU_CHANGE_TYPE_*
 * @param String $summary   Summary of the change
 * @param mixed  $extra     In case of a revert the revision (timestmp) of the reverted page
 * @param array  $flags     Additional flags in a key value array.
 *                             Available flags:
 *                             - ExternalEdit - mark as an external edit.
 * @param null|int $sizechange Change of filesize
 *
 * @author Andreas Gohr <andi@splitbrain.org>
 * @author Esther Brunner <wikidesign@gmail.com>
 * @author Ben Coburn <btcoburn@silicodon.net>
 */
function addLogEntry($date, $id, $type=DOKU_CHANGE_TYPE_EDIT, $summary='', $extra='', $flags=null, $sizechange = null){
    global $conf, $INFO;
    /** @var Input $INPUT */
    global $INPUT;

    // check for special flags as keys
    if (!is_array($flags)) { $flags = array(); }
    $flagExternalEdit = isset($flags['ExternalEdit']);

    $id = cleanid($id);
    $file = wikiFN($id);
    $created = @filectime($file);
    $minor = ($type===DOKU_CHANGE_TYPE_MINOR_EDIT);
    $wasRemoved = ($type===DOKU_CHANGE_TYPE_DELETE);

    if(!$date) $date = time(); //use current time if none supplied
    $remote = (!$flagExternalEdit)?clientIP(true):'127.0.0.1';
    $user   = (!$flagExternalEdit)?$INPUT->server->str('REMOTE_USER'):'';
    if($sizechange === null) {
        $sizechange = '';
    } else {
        $sizechange = (int) $sizechange;
    }

    $strip = array("\t", "\n");
    $logline = array(
        'date'       => $date,
        'ip'         => $remote,
        'type'       => str_replace($strip, '', $type),
        'id'         => $id,
        'user'       => $user,
        'sum'        => utf8_substr(str_replace($strip, '', $summary), 0, 255),
        'extra'      => str_replace($strip, '', $extra),
        'sizechange' => $sizechange
    );

    $wasCreated = ($type===DOKU_CHANGE_TYPE_CREATE);
    $wasReverted = ($type===DOKU_CHANGE_TYPE_REVERT);
    // update metadata
    if (!$wasRemoved) {
        $oldmeta = p_read_metadata($id);
        $meta    = array();
        if ($wasCreated && empty($oldmeta['persistent']['date']['created'])){ // newly created
            $meta['date']['created'] = $created;
            if ($user){
                $meta['creator'] = $INFO['userinfo']['name'];
                $meta['user']    = $user;
            }
        } elseif (($wasCreated || $wasReverted) && !empty($oldmeta['persistent']['date']['created'])) { // re-created / restored
            $meta['date']['created']  = $oldmeta['persistent']['date']['created'];
            $meta['date']['modified'] = $created; // use the files ctime here
            $meta['creator'] = $oldmeta['persistent']['creator'];
            if ($user) $meta['contributor'][$user] = $INFO['userinfo']['name'];
        } elseif (!$minor) {   // non-minor modification
            $meta['date']['modified'] = $date;
            if ($user) $meta['contributor'][$user] = $INFO['userinfo']['name'];
        }
        $meta['last_change'] = $logline;
        p_set_metadata($id, $meta);
    }

    // add changelog lines
    $logline = implode("\t", $logline)."\n";
    io_saveFile(metaFN($id,'.changes'),$logline,true); //page changelog
    io_saveFile($conf['changelog'],$logline,true); //global changelog cache
}

/**
 * Add's an entry to the media changelog
 *
 * @author Michael Hamann <michael@content-space.de>
 * @author Andreas Gohr <andi@splitbrain.org>
 * @author Esther Brunner <wikidesign@gmail.com>
 * @author Ben Coburn <btcoburn@silicodon.net>
 *
 * @param int    $date      Timestamp of the change
 * @param String $id        Name of the affected page
 * @param String $type      Type of the change see DOKU_CHANGE_TYPE_*
 * @param String $summary   Summary of the change
 * @param mixed  $extra     In case of a revert the revision (timestmp) of the reverted page
 * @param array  $flags     Additional flags in a key value array.
 *                             Available flags:
 *                             - (none, so far)
 * @param null|int $sizechange Change of filesize
 */
function addMediaLogEntry($date, $id, $type=DOKU_CHANGE_TYPE_EDIT, $summary='', $extra='', $flags=null, $sizechange = null){
    global $conf;
    /** @var Input $INPUT */
    global $INPUT;

    $id = cleanid($id);

    if(!$date) $date = time(); //use current time if none supplied
    $remote = clientIP(true);
    $user   = $INPUT->server->str('REMOTE_USER');
    if($sizechange === null) {
        $sizechange = '';
    } else {
        $sizechange = (int) $sizechange;
    }

    $strip = array("\t", "\n");
    $logline = array(
        'date'       => $date,
        'ip'         => $remote,
        'type'       => str_replace($strip, '', $type),
        'id'         => $id,
        'user'       => $user,
        'sum'        => utf8_substr(str_replace($strip, '', $summary), 0, 255),
        'extra'      => str_replace($strip, '', $extra),
        'sizechange' => $sizechange
    );

    // add changelog lines
    $logline = implode("\t", $logline)."\n";
    io_saveFile($conf['media_changelog'],$logline,true); //global media changelog cache
    io_saveFile(mediaMetaFN($id,'.changes'),$logline,true); //media file's changelog
}

/**
 * returns an array of recently changed files using the
 * changelog
 *
 * The following constants can be used to control which changes are
 * included. Add them together as needed.
 *
 * RECENTS_SKIP_DELETED   - don't include deleted pages
 * RECENTS_SKIP_MINORS    - don't include minor changes
 * RECENTS_SKIP_SUBSPACES - don't include subspaces
 * RECENTS_MEDIA_CHANGES  - return media changes instead of page changes
 * RECENTS_MEDIA_PAGES_MIXED  - return both media changes and page changes
 *
 * @param int    $first   number of first entry returned (for paginating
 * @param int    $num     return $num entries
 * @param string $ns      restrict to given namespace
 * @param int    $flags   see above
 * @return array recently changed files
 *
 * @author Ben Coburn <btcoburn@silicodon.net>
 * @author Kate Arzamastseva <pshns@ukr.net>
 */
function getRecents($first,$num,$ns='',$flags=0){
    global $conf;
    $recent = array();
    $count  = 0;

    if(!$num)
        return $recent;

    // read all recent changes. (kept short)
    if ($flags & RECENTS_MEDIA_CHANGES) {
        $lines = @file($conf['media_changelog']);
    } else {
        $lines = @file($conf['changelog']);
    }
    $lines_position = count($lines)-1;
    $media_lines_position = 0;
    $media_lines = array();

    if ($flags & RECENTS_MEDIA_PAGES_MIXED) {
        $media_lines = @file($conf['media_changelog']);
        $media_lines_position = count($media_lines)-1;
    }

    $seen = array(); // caches seen lines, _handleRecent() skips them

    // handle lines
    while ($lines_position >= 0 || (($flags & RECENTS_MEDIA_PAGES_MIXED) && $media_lines_position >=0)) {
        if (empty($rec) && $lines_position >= 0) {
            $rec = _handleRecent(@$lines[$lines_position], $ns, $flags, $seen);
            if (!$rec) {
                $lines_position --;
                continue;
            }
        }
        if (($flags & RECENTS_MEDIA_PAGES_MIXED) && empty($media_rec) && $media_lines_position >= 0) {
            $media_rec = _handleRecent(@$media_lines[$media_lines_position], $ns, $flags | RECENTS_MEDIA_CHANGES, $seen);
            if (!$media_rec) {
                $media_lines_position --;
                continue;
            }
        }
        if (($flags & RECENTS_MEDIA_PAGES_MIXED) && @$media_rec['date'] >= @$rec['date']) {
            $media_lines_position--;
            $x = $media_rec;
            $x['media'] = true;
            $media_rec = false;
        } else {
            $lines_position--;
            $x = $rec;
            if ($flags & RECENTS_MEDIA_CHANGES) $x['media'] = true;
            $rec = false;
        }
        if(--$first >= 0) continue; // skip first entries
        $recent[] = $x;
        $count++;
        // break when we have enough entries
        if($count >= $num){ break; }
    }
    return $recent;
}

/**
 * returns an array of files changed since a given time using the
 * changelog
 *
 * The following constants can be used to control which changes are
 * included. Add them together as needed.
 *
 * RECENTS_SKIP_DELETED   - don't include deleted pages
 * RECENTS_SKIP_MINORS    - don't include minor changes
 * RECENTS_SKIP_SUBSPACES - don't include subspaces
 * RECENTS_MEDIA_CHANGES  - return media changes instead of page changes
 *
 * @param int    $from    date of the oldest entry to return
 * @param int    $to      date of the newest entry to return (for pagination, optional)
 * @param string $ns      restrict to given namespace (optional)
 * @param int    $flags   see above (optional)
 * @return array of files
 *
 * @author Michael Hamann <michael@content-space.de>
 * @author Ben Coburn <btcoburn@silicodon.net>
 */
function getRecentsSince($from,$to=null,$ns='',$flags=0){
    global $conf;
    $recent = array();

    if($to && $to < $from)
        return $recent;

    // read all recent changes. (kept short)
    if ($flags & RECENTS_MEDIA_CHANGES) {
        $lines = @file($conf['media_changelog']);
    } else {
        $lines = @file($conf['changelog']);
    }
    if(!$lines) return $recent;

    // we start searching at the end of the list
    $lines = array_reverse($lines);

    // handle lines
    $seen = array(); // caches seen lines, _handleRecent() skips them

    foreach($lines as $line){
        $rec = _handleRecent($line, $ns, $flags, $seen);
        if($rec !== false) {
            if ($rec['date'] >= $from) {
                if (!$to || $rec['date'] <= $to) {
                    $recent[] = $rec;
                }
            } else {
                break;
            }
        }
    }

    return array_reverse($recent);
}

/**
 * Internal function used by getRecents
 *
 * don't call directly
 *
 * @see getRecents()
 * @author Andreas Gohr <andi@splitbrain.org>
 * @author Ben Coburn <btcoburn@silicodon.net>
 *
 * @param string $line   changelog line
 * @param string $ns     restrict to given namespace
 * @param int    $flags  flags to control which changes are included
 * @param array  $seen   listing of seen pages
 * @return array|bool    false or array with info about a change
 */
function _handleRecent($line,$ns,$flags,&$seen){
    if(empty($line)) return false;   //skip empty lines

    // split the line into parts
    $recent = parseChangelogLine($line);
    if ($recent===false) { return false; }

    // skip seen ones
    if(isset($seen[$recent['id']])) return false;

    // skip minors
    if($recent['type']===DOKU_CHANGE_TYPE_MINOR_EDIT && ($flags & RECENTS_SKIP_MINORS)) return false;

    // remember in seen to skip additional sights
    $seen[$recent['id']] = 1;

    // check if it's a hidden page
    if(isHiddenPage($recent['id'])) return false;

    // filter namespace
    if (($ns) && (strpos($recent['id'],$ns.':') !== 0)) return false;

    // exclude subnamespaces
    if (($flags & RECENTS_SKIP_SUBSPACES) && (getNS($recent['id']) != $ns)) return false;

    // check ACL
    if ($flags & RECENTS_MEDIA_CHANGES) {
        $recent['perms'] = auth_quickaclcheck(getNS($recent['id']).':*');
    } else {
        $recent['perms'] = auth_quickaclcheck($recent['id']);
    }
    if ($recent['perms'] < AUTH_READ) return false;

    // check existance
    if($flags & RECENTS_SKIP_DELETED){
        $fn = (($flags & RECENTS_MEDIA_CHANGES) ? mediaFN($recent['id']) : wikiFN($recent['id']));
        if(!file_exists($fn)) return false;
    }

    return $recent;
}

/**
 * Class ChangeLog
 * methods for handling of changelog of pages or media files
 */
abstract class ChangeLog {

    /** @var string */
    protected $id;
    /** @var int */
    protected $chunk_size;
    /** @var array */
    protected $cache;

    /**
     * Constructor
     *
     * @param string $id         page id
     * @param int $chunk_size maximum block size read from file
     */
    public function __construct($id, $chunk_size = 8192) {
        global $cache_revinfo;

        $this->cache =& $cache_revinfo;
        if(!isset($this->cache[$id])) {
            $this->cache[$id] = array();
        }

        $this->id = $id;
        $this->setChunkSize($chunk_size);

    }

    /**
     * Set chunk size for file reading
     * Chunk size zero let read whole file at once
     *
     * @param int $chunk_size maximum block size read from file
     */
    public function setChunkSize($chunk_size) {
        if(!is_numeric($chunk_size)) $chunk_size = 0;

        $this->chunk_size = (int) max($chunk_size, 0);
    }

    /**
     * Returns path to changelog
     *
     * @return string path to file
     */
    abstract protected function getChangelogFilename();

    /**
     * Returns path to current page/media
     *
     * @return string path to file
     */
    abstract protected function getFilename();

    /**
     * Get the changelog information for a specific page id and revision (timestamp)
     *
     * Adjacent changelog lines are optimistically parsed and cached to speed up
     * consecutive calls to getRevisionInfo. For large changelog files, only the chunk
     * containing the requested changelog line is read.
     *
     * @param int $rev        revision timestamp
     * @return bool|array false or array with entries:
     *      - date:  unix timestamp
     *      - ip:    IPv4 address (127.0.0.1)
     *      - type:  log line type
     *      - id:    page id
     *      - user:  user name
     *      - sum:   edit summary (or action reason)
     *      - extra: extra data (varies by line type)
     *
     * @author Ben Coburn <btcoburn@silicodon.net>
     * @author Kate Arzamastseva <pshns@ukr.net>
     */
    public function getRevisionInfo($rev) {
        $rev = max($rev, 0);

        // check if it's already in the memory cache
        if(isset($this->cache[$this->id]) && isset($this->cache[$this->id][$rev])) {
            return $this->cache[$this->id][$rev];
        }

        //read lines from changelog
        list($fp, $lines) = $this->readloglines($rev);
        if($fp) {
            fclose($fp);
        }
        if(empty($lines)) return false;

        // parse and cache changelog lines
        foreach($lines as $value) {
            $tmp = parseChangelogLine($value);
            if($tmp !== false) {
                $this->cache[$this->id][$tmp['date']] = $tmp;
            }
        }
        if(!isset($this->cache[$this->id][$rev])) {
            return false;
        }
        return $this->cache[$this->id][$rev];
    }

    /**
     * Return a list of page revisions numbers
     *
     * Does not guarantee that the revision exists in the attic,
     * only that a line with the date exists in the changelog.
     * By default the current revision is skipped.
     *
     * The current revision is automatically skipped when the page exists.
     * See $INFO['meta']['last_change'] for the current revision.
     * A negative $first let read the current revision too.
     *
     * For efficiency, the log lines are parsed and cached for later
     * calls to getRevisionInfo. Large changelog files are read
     * backwards in chunks until the requested number of changelog
     * lines are recieved.
     *
     * @param int $first      skip the first n changelog lines
     * @param int $num        number of revisions to return
     * @return array with the revision timestamps
     *
     * @author Ben Coburn <btcoburn@silicodon.net>
     * @author Kate Arzamastseva <pshns@ukr.net>
     */
    public function getRevisions($first, $num) {
        $revs = array();
        $lines = array();
        $count = 0;

        $num = max($num, 0);
        if($num == 0) {
            return $revs;
        }

        if($first < 0) {
            $first = 0;
        } else if(file_exists($this->getFilename())) {
            // skip current revision if the page exists
            $first = max($first + 1, 0);
        }

        $file = $this->getChangelogFilename();

        if(!file_exists($file)) {
            return $revs;
        }
        if(filesize($file) < $this->chunk_size || $this->chunk_size == 0) {
            // read whole file
            $lines = file($file);
            if($lines === false) {
                return $revs;
            }
        } else {
            // read chunks backwards
            $fp = fopen($file, 'rb'); // "file pointer"
            if($fp === false) {
                return $revs;
            }
            fseek($fp, 0, SEEK_END);
            $tail = ftell($fp);

            // chunk backwards
            $finger = max($tail - $this->chunk_size, 0);
            while($count < $num + $first) {
                $nl = $this->getNewlinepointer($fp, $finger);

                // was the chunk big enough? if not, take another bite
                if($nl > 0 && $tail <= $nl) {
                    $finger = max($finger - $this->chunk_size, 0);
                    continue;
                } else {
                    $finger = $nl;
                }

                // read chunk
                $chunk = '';
                $read_size = max($tail - $finger, 0); // found chunk size
                $got = 0;
                while($got < $read_size && !feof($fp)) {
                    $tmp = @fread($fp, max(min($this->chunk_size, $read_size - $got), 0));
                    if($tmp === false) {
                        break;
                    } //error state
                    $got += strlen($tmp);
                    $chunk .= $tmp;
                }
                $tmp = explode("\n", $chunk);
                array_pop($tmp); // remove trailing newline

                // combine with previous chunk
                $count += count($tmp);
                $lines = array_merge($tmp, $lines);

                // next chunk
                if($finger == 0) {
                    break;
                } // already read all the lines
                else {
                    $tail = $finger;
                    $finger = max($tail - $this->chunk_size, 0);
                }
            }
            fclose($fp);
        }

        // skip parsing extra lines
        $num = max(min(count($lines) - $first, $num), 0);
        if     ($first > 0 && $num > 0)  { $lines = array_slice($lines, max(count($lines) - $first - $num, 0), $num); }
        else if($first > 0 && $num == 0) { $lines = array_slice($lines, 0, max(count($lines) - $first, 0)); }
        else if($first == 0 && $num > 0) { $lines = array_slice($lines, max(count($lines) - $num, 0)); }

        // handle lines in reverse order
        for($i = count($lines) - 1; $i >= 0; $i--) {
            $tmp = parseChangelogLine($lines[$i]);
            if($tmp !== false) {
                $this->cache[$this->id][$tmp['date']] = $tmp;
                $revs[] = $tmp['date'];
            }
        }

        return $revs;
    }

    /**
     * Get the nth revision left or right handside  for a specific page id and revision (timestamp)
     *
     * For large changelog files, only the chunk containing the
     * reference revision $rev is read and sometimes a next chunck.
     *
     * Adjacent changelog lines are optimistically parsed and cached to speed up
     * consecutive calls to getRevisionInfo.
     *
     * @param int $rev        revision timestamp used as startdate (doesn't need to be revisionnumber)
     * @param int $direction  give position of returned revision with respect to $rev; positive=next, negative=prev
     * @return bool|int
     *      timestamp of the requested revision
     *      otherwise false
     */
    public function getRelativeRevision($rev, $direction) {
        $rev = max($rev, 0);
        $direction = (int) $direction;

        //no direction given or last rev, so no follow-up
        if(!$direction || ($direction > 0 && $this->isCurrentRevision($rev))) {
            return false;
        }

        //get lines from changelog
        list($fp, $lines, $head, $tail, $eof) = $this->readloglines($rev);
        if(empty($lines)) return false;

        // look for revisions later/earlier then $rev, when founded count till the wanted revision is reached
        // also parse and cache changelog lines for getRevisionInfo().
        $revcounter = 0;
        $relativerev = false;
        $checkotherchunck = true; //always runs once
        while(!$relativerev && $checkotherchunck) {
            $tmp = array();
            //parse in normal or reverse order
            $count = count($lines);
            if($direction > 0) {
                $start = 0;
                $step = 1;
            } else {
                $start = $count - 1;
                $step = -1;
            }
            for($i = $start; $i >= 0 && $i < $count; $i = $i + $step) {
                $tmp = parseChangelogLine($lines[$i]);
                if($tmp !== false) {
                    $this->cache[$this->id][$tmp['date']] = $tmp;
                    //look for revs older/earlier then reference $rev and select $direction-th one
                    if(($direction > 0 && $tmp['date'] > $rev) || ($direction < 0 && $tmp['date'] < $rev)) {
                        $revcounter++;
                        if($revcounter == abs($direction)) {
                            $relativerev = $tmp['date'];
                        }
                    }
                }
            }

            //true when $rev is found, but not the wanted follow-up.
            $checkotherchunck = $fp
                && ($tmp['date'] == $rev || ($revcounter > 0 && !$relativerev))
                && !(($tail == $eof && $direction > 0) || ($head == 0 && $direction < 0));

            if($checkotherchunck) {
                list($lines, $head, $tail) = $this->readAdjacentChunk($fp, $head, $tail, $direction);

                if(empty($lines)) break;
            }
        }
        if($fp) {
            fclose($fp);
        }

        return $relativerev;
    }

    /**
     * Returns revisions around rev1 and rev2
     * When available it returns $max entries for each revision
     *
     * @param int $rev1 oldest revision timestamp
     * @param int $rev2 newest revision timestamp (0 looks up last revision)
     * @param int $max maximum number of revisions returned
     * @return array with two arrays with revisions surrounding rev1 respectively rev2
     */
    public function getRevisionsAround($rev1, $rev2, $max = 50) {
        $max = floor(abs($max) / 2)*2 + 1;
        $rev1 = max($rev1, 0);
        $rev2 = max($rev2, 0);

        if($rev2) {
            if($rev2 < $rev1) {
                $rev = $rev2;
                $rev2 = $rev1;
                $rev1 = $rev;
            }
        } else {
            //empty right side means a removed page. Look up last revision.
            $revs = $this->getRevisions(-1, 1);
            $rev2 = $revs[0];
        }
        //collect revisions around rev2
        list($revs2, $allrevs, $fp, $lines, $head, $tail) = $this->retrieveRevisionsAround($rev2, $max);

        if(empty($revs2)) return array(array(), array());

        //collect revisions around rev1
        $index = array_search($rev1, $allrevs);
        if($index === false) {
            //no overlapping revisions
            list($revs1,,,,,) = $this->retrieveRevisionsAround($rev1, $max);
            if(empty($revs1)) $revs1 = array();
        } else {
            //revisions overlaps, reuse revisions around rev2
            $revs1 = $allrevs;
            while($head > 0) {
                for($i = count($lines) - 1; $i >= 0; $i--) {
                    $tmp = parseChangelogLine($lines[$i]);
                    if($tmp !== false) {
                        $this->cache[$this->id][$tmp['date']] = $tmp;
                        $revs1[] = $tmp['date'];
                        $index++;

                        if($index > floor($max / 2)) break 2;
                    }
                }

                list($lines, $head, $tail) = $this->readAdjacentChunk($fp, $head, $tail, -1);
            }
            sort($revs1);
            //return wanted selection
            $revs1 = array_slice($revs1, max($index - floor($max/2), 0), $max);
        }

        return array(array_reverse($revs1), array_reverse($revs2));
    }

    /**
     * Returns lines from changelog.
     * If file larger than $chuncksize, only chunck is read that could contain $rev.
     *
     * @param int $rev   revision timestamp
     * @return array|false
     *     if success returns array(fp, array(changeloglines), $head, $tail, $eof)
     *     where fp only defined for chuck reading, needs closing.
     *     otherwise false
     */
    protected function readloglines($rev) {
        $file = $this->getChangelogFilename();

        if(!file_exists($file)) {
            return false;
        }

        $fp = null;
        $head = 0;
        $tail = 0;
        $eof = 0;

        if(filesize($file) < $this->chunk_size || $this->chunk_size == 0) {
            // read whole file
            $lines = file($file);
            if($lines === false) {
                return false;
            }
        } else {
            // read by chunk
            $fp = fopen($file, 'rb'); // "file pointer"
            if($fp === false) {
                return false;
            }
            $head = 0;
            fseek($fp, 0, SEEK_END);
            $eof = ftell($fp);
            $tail = $eof;

            // find chunk
            while($tail - $head > $this->chunk_size) {
                $finger = $head + floor(($tail - $head) / 2.0);
                $finger = $this->getNewlinepointer($fp, $finger);
                $tmp = fgets($fp);
                if($finger == $head || $finger == $tail) {
                    break;
                }
                $tmp = parseChangelogLine($tmp);
                $finger_rev = $tmp['date'];

                if($finger_rev > $rev) {
                    $tail = $finger;
                } else {
                    $head = $finger;
                }
            }

            if($tail - $head < 1) {
                // cound not find chunk, assume requested rev is missing
                fclose($fp);
                return false;
            }

            $lines = $this->readChunk($fp, $head, $tail);
        }
        return array(
            $fp,
            $lines,
            $head,
            $tail,
            $eof
        );
    }

    /**
     * Read chunk and return array with lines of given chunck.
     * Has no check if $head and $tail are really at a new line
     *
     * @param resource $fp    resource filepointer
     * @param int      $head  start point chunck
     * @param int      $tail  end point chunck
     * @return array lines read from chunck
     */
    protected function readChunk($fp, $head, $tail) {
        $chunk = '';
        $chunk_size = max($tail - $head, 0); // found chunk size
        $got = 0;
        fseek($fp, $head);
        while($got < $chunk_size && !feof($fp)) {
            $tmp = @fread($fp, max(min($this->chunk_size, $chunk_size - $got), 0));
            if($tmp === false) { //error state
                break;
            }
            $got += strlen($tmp);
            $chunk .= $tmp;
        }
        $lines = explode("\n", $chunk);
        array_pop($lines); // remove trailing newline
        return $lines;
    }

    /**
     * Set pointer to first new line after $finger and return its position
     *
     * @param resource $fp      filepointer
     * @param int      $finger  a pointer
     * @return int pointer
     */
    protected function getNewlinepointer($fp, $finger) {
        fseek($fp, $finger);
        $nl = $finger;
        if($finger > 0) {
            fgets($fp); // slip the finger forward to a new line
            $nl = ftell($fp);
        }
        return $nl;
    }

    /**
     * Check whether given revision is the current page
     *
     * @param int $rev   timestamp of current page
     * @return bool true if $rev is current revision, otherwise false
     */
    public function isCurrentRevision($rev) {
        return $rev == @filemtime($this->getFilename());
    }

    /**
    * Return an existing revision for a specific date which is
    * the current one or younger or equal then the date
    *
    * @param number $date_at timestamp
    * @return string revision ('' for current)
    */
    function getLastRevisionAt($date_at){
        //requested date_at(timestamp) younger or equal then modified_time($this->id) => load current
        if(file_exists($this->getFilename()) && $date_at >= @filemtime($this->getFilename())) {
            return '';
        } else if ($rev = $this->getRelativeRevision($date_at+1, -1)) { //+1 to get also the requested date revision
            return $rev;
        } else {
            return false;
        }
    }

    /**
     * Returns the next lines of the changelog  of the chunck before head or after tail
     *
     * @param resource $fp filepointer
     * @param int $head position head of last chunk
     * @param int $tail position tail of last chunk
     * @param int $direction positive forward, negative backward
     * @return array with entries:
     *    - $lines: changelog lines of readed chunk
     *    - $head: head of chunk
     *    - $tail: tail of chunk
     */
    protected function readAdjacentChunk($fp, $head, $tail, $direction) {
        if(!$fp) return array(array(), $head, $tail);

        if($direction > 0) {
            //read forward
            $head = $tail;
            $tail = $head + floor($this->chunk_size * (2 / 3));
            $tail = $this->getNewlinepointer($fp, $tail);
        } else {
            //read backward
            $tail = $head;
            $head = max($tail - $this->chunk_size, 0);
            while(true) {
                $nl = $this->getNewlinepointer($fp, $head);
                // was the chunk big enough? if not, take another bite
                if($nl > 0 && $tail <= $nl) {
                    $head = max($head - $this->chunk_size, 0);
                } else {
                    $head = $nl;
                    break;
                }
            }
        }

        //load next chunck
        $lines = $this->readChunk($fp, $head, $tail);
        return array($lines, $head, $tail);
    }

    /**
     * Collect the $max revisions near to the timestamp $rev
     *
     * @param int $rev revision timestamp
     * @param int $max maximum number of revisions to be returned
     * @return bool|array
     *     return array with entries:
     *       - $requestedrevs: array of with $max revision timestamps
     *       - $revs: all parsed revision timestamps
     *       - $fp: filepointer only defined for chuck reading, needs closing.
     *       - $lines: non-parsed changelog lines before the parsed revisions
     *       - $head: position of first readed changelogline
     *       - $lasttail: position of end of last readed changelogline
     *     otherwise false
     */
    protected function retrieveRevisionsAround($rev, $max) {
        //get lines from changelog
        list($fp, $lines, $starthead, $starttail, /* $eof */) = $this->readloglines($rev);
        if(empty($lines)) return false;

        //parse chunk containing $rev, and read forward more chunks until $max/2 is reached
        $head = $starthead;
        $tail = $starttail;
        $revs = array();
        $aftercount = $beforecount = 0;
        while(count($lines) > 0) {
            foreach($lines as $line) {
                $tmp = parseChangelogLine($line);
                if($tmp !== false) {
                    $this->cache[$this->id][$tmp['date']] = $tmp;
                    $revs[] = $tmp['date'];
                    if($tmp['date'] >= $rev) {
                        //count revs after reference $rev
                        $aftercount++;
                        if($aftercount == 1) $beforecount = count($revs);
                    }
                    //enough revs after reference $rev?
                    if($aftercount > floor($max / 2)) break 2;
                }
            }
            //retrieve next chunk
            list($lines, $head, $tail) = $this->readAdjacentChunk($fp, $head, $tail, 1);
        }
        if($aftercount == 0) return false;

        $lasttail = $tail;

        //read additional chuncks backward until $max/2 is reached and total number of revs is equal to $max
        $lines = array();
        $i = 0;
        if($aftercount > 0) {
            $head = $starthead;
            $tail = $starttail;
            while($head > 0) {
                list($lines, $head, $tail) = $this->readAdjacentChunk($fp, $head, $tail, -1);

                for($i = count($lines) - 1; $i >= 0; $i--) {
                    $tmp = parseChangelogLine($lines[$i]);
                    if($tmp !== false) {
                        $this->cache[$this->id][$tmp['date']] = $tmp;
                        $revs[] = $tmp['date'];
                        $beforecount++;
                        //enough revs before reference $rev?
                        if($beforecount > max(floor($max / 2), $max - $aftercount)) break 2;
                    }
                }
            }
        }
        sort($revs);

        //keep only non-parsed lines
        $lines = array_slice($lines, 0, $i);
        //trunk desired selection
        $requestedrevs = array_slice($revs, -$max, $max);

        return array($requestedrevs, $revs, $fp, $lines, $head, $lasttail);
    }
}

/**
 * Class PageChangelog handles changelog of a wiki page
 */
class PageChangelog extends ChangeLog {

    /**
     * Returns path to changelog
     *
     * @return string path to file
     */
    protected function getChangelogFilename() {
        return metaFN($this->id, '.changes');
    }

    /**
     * Returns path to current page/media
     *
     * @return string path to file
     */
    protected function getFilename() {
        return wikiFN($this->id);
    }
}

/**
 * Class MediaChangelog handles changelog of a media file
 */
class MediaChangelog extends ChangeLog {

    /**
     * Returns path to changelog
     *
     * @return string path to file
     */
    protected function getChangelogFilename() {
        return mediaMetaFN($this->id, '.changes');
    }

    /**
     * Returns path to current page/media
     *
     * @return string path to file
     */
    protected function getFilename() {
        return mediaFN($this->id);
    }
}