+<?php
+/**
+ * StatusNet - the distributed open-source microblogging tool
+ * Copyright (C) 2011, StatusNet, Inc.
+ *
+ * A stream of notices
+ *
+ * PHP version 5
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @category Stream
+ * @package StatusNet
+ * @author Evan Prodromou <evan@status.net>
+ * @copyright 2011 StatusNet, Inc.
+ * @license http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
+ * @link http://status.net/
+ */
+
+if (!defined('STATUSNET')) {
+ // This check helps protect against security problems;
+ // your code file can't be executed directly from the web.
+ exit(1);
+}
+
+/**
+ * Class for notice streams
+ *
+ * @category Stream
+ * @package StatusNet
+ * @author Evan Prodromou <evan@status.net>
+ * @copyright 2011 StatusNet, Inc.
+ * @license http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
+ * @link http://status.net/
+ */
+
+class CachingNoticeStream extends NoticeStream
+{
+ const CACHE_WINDOW = 200;
+
+ public $stream = null;
+ public $cachekey = null;
+
+ function __construct($stream, $cachekey)
+ {
+ $this->stream = $stream;
+ $this->cachekey = $cachekey;
+ }
+
+ function getNoticeIds($offset=0, $limit=20, $sinceId=0, $maxId=0)
+ {
+ $cache = Cache::instance();
+
+ // We cache self::CACHE_WINDOW elements at the tip of the stream.
+ // If the cache won't be hit, just generate directly.
+
+ if (empty($cache) ||
+ $sinceId != 0 || $maxId != 0 ||
+ is_null($limit) ||
+ ($offset + $limit) > self::CACHE_WINDOW) {
+ return $this->stream->getNoticeIds($offset, $limit, $sinceId, $maxId);
+ }
+
+ // Check the cache to see if we have the stream.
+
+ $idkey = Cache::key($this->cachekey);
+
+ $idstr = $cache->get($idkey);
+
+ if ($idstr !== false) {
+ // Cache hit! Woohoo!
+ $window = explode(',', $idstr);
+ $ids = array_slice($window, $offset, $limit);
+ return $ids;
+ }
+
+ // Check the cache to see if we have a "last-known-good" version.
+ // The actual cache gets blown away when new notices are added, but
+ // the "last" value holds a lot of info. We might need to only generate
+ // a few at the "tip", which can bound our queries and save lots
+ // of time.
+
+ $laststr = $cache->get($idkey.';last');
+
+ if ($laststr !== false) {
+ $window = explode(',', $laststr);
+ $last_id = $window[0];
+ $new_ids = $this->stream->getNoticeIds(0, self::CACHE_WINDOW, $last_id, 0);
+
+ $new_window = array_merge($new_ids, $window);
+
+ $new_windowstr = implode(',', $new_window);
+
+ $result = $cache->set($idkey, $new_windowstr);
+ $result = $cache->set($idkey . ';last', $new_windowstr);
+
+ $ids = array_slice($new_window, $offset, $limit);
+
+ return $ids;
+ }
+
+ // No cache hits :( Generate directly and stick the results
+ // into the cache. Note we generate the full cache window.
+
+ $window = $this->stream->getNoticeIds(0, self::CACHE_WINDOW, 0, 0);
+
+ $windowstr = implode(',', $window);
+
+ $result = $cache->set($idkey, $windowstr);
+ $result = $cache->set($idkey . ';last', $windowstr);
+
+ // Return just the slice that was requested
+
+ $ids = array_slice($window, $offset, $limit);
+
+ return $ids;
+ }
+}