installed dokuwiki, added to navbar, updated news

1 files changed, 1059 insertions, 0 deletions

diff --git a/wiki/inc/changelog.php b/wiki/inc/changelog.php
new file mode 100644
index 0000000..d77b018
--- /dev/null
+++ b/wiki/inc/changelog.php
@@ -0,0 +1,1059 @@
+<?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);
+    }
+}