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<?php
/**
* StatusNet, the distributed open-source microblogging tool
*
* Cache interface plus default in-memory cache implementation
*
* PHP version 5
*
* LICENCE: 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 Cache
* @package StatusNet
* @author Evan Prodromou <evan@status.net>
* @copyright 2009 StatusNet, Inc.
* @license http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
* @link http://status.net/
*/
/**
* Interface for caching
*
* An abstract interface for caching. Because we originally used the
* Memcache plugin directly, the interface uses a small subset of the
* Memcache interface.
*
* @category Cache
* @package StatusNet
* @author Evan Prodromou <evan@status.net>
* @copyright 2009 StatusNet, Inc.
* @license http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
* @link http://status.net/
*/
class Cache
{
var $_items = array();
static $_inst = null;
const COMPRESSED = 1;
/**
* Singleton constructor
*
* Use this to get the singleton instance of Cache.
*
* @return Cache cache object
*/
static function instance()
{
if (is_null(self::$_inst)) {
self::$_inst = new Cache();
}
return self::$_inst;
}
/**
* Create a cache key from input text
*
* Builds a cache key from input text. Helps to namespace
* the cache area (if shared with other applications or sites)
* and prevent conflicts.
*
* @param string $extra the real part of the key
*
* @return string full key
*/
static function key($extra)
{
$base_key = common_config('cache', 'base');
if (empty($base_key)) {
$base_key = common_keyize(common_config('site', 'name'));
}
return 'statusnet:' . $base_key . ':' . $extra;
}
/**
* Make a string suitable for use as a key
*
* Useful for turning primary keys of tables into cache keys.
*
* @param string $str string to turn into a key
*
* @return string keyized string
*/
static function keyize($str)
{
$str = strtolower($str);
$str = preg_replace('/\s/', '_', $str);
return $str;
}
/**
* Get a value associated with a key
*
* The value should have been set previously.
*
* @param string $key Lookup key
*
* @return string retrieved value or null if unfound
*/
function get($key)
{
$value = false;
if (Event::handle('StartCacheGet', array(&$key, &$value))) {
if (array_key_exists($key, $this->_items)) {
$value = unserialize($this->_items[$key]);
}
Event::handle('EndCacheGet', array($key, &$value));
}
return $value;
}
/**
* Set the value associated with a key
*
* @param string $key The key to use for lookups
* @param string $value The value to store
* @param integer $flag Flags to use, may include Cache::COMPRESSED
* @param integer $expiry Expiry value, mostly ignored
*
* @return boolean success flag
*/
function set($key, $value, $flag=null, $expiry=null)
{
$success = false;
if (Event::handle('StartCacheSet', array(&$key, &$value, &$flag,
&$expiry, &$success))) {
$this->_items[$key] = serialize($value);
$success = true;
Event::handle('EndCacheSet', array($key, $value, $flag,
$expiry));
}
return $success;
}
/**
* Atomically increment an existing numeric value.
* Existing expiration time should remain unchanged, if any.
*
* @param string $key The key to use for lookups
* @param int $step Amount to increment (default 1)
*
* @return mixed incremented value, or false if not set.
*/
function increment($key, $step=1)
{
$value = false;
if (Event::handle('StartCacheIncrement', array(&$key, &$step, &$value))) {
// Fallback is not guaranteed to be atomic,
// and may original expiry value.
$value = $this->get($key);
if ($value !== false) {
$value += $step;
$ok = $this->set($key, $value);
$got = $this->get($key);
}
Event::handle('EndCacheIncrement', array($key, $step, $value));
}
return $value;
}
/**
* Delete the value associated with a key
*
* @param string $key Key to delete
*
* @return boolean success flag
*/
function delete($key)
{
$success = false;
if (Event::handle('StartCacheDelete', array(&$key, &$success))) {
if (array_key_exists($key, $this->_items)) {
unset($this->_items[$key]);
}
$success = true;
Event::handle('EndCacheDelete', array($key));
}
return $success;
}
/**
* Close or reconnect any remote connections, such as to give
* daemon processes a chance to reconnect on a fresh socket.
*
* @return boolean success flag
*/
function reconnect()
{
$success = false;
if (Event::handle('StartCacheReconnect', array(&$success))) {
$success = true;
Event::handle('EndCacheReconnect', array());
}
return $success;
}
}
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