<?php /* * Copyright 2010 Google Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /** * A persistent storage class based on the APC cache, which is not * really very persistent, as soon as you restart your web server * the storage will be wiped, however for debugging and/or speed * it can be useful, kinda, and cache is a lot cheaper then storage. * * @author Chris Chabot <chabotc@google.com> */ class apiApcCache extends apiCache { public function __construct() { if (! function_exists('apc_add')) { throw new apiCacheException("Apc functions not available"); } } private function isLocked($key) { if ((@apc_fetch($key . '.lock')) === false) { return false; } return true; } private function createLock($key) { // the interesting thing is that this could fail if the lock was created in the meantime.. // but we'll ignore that out of convenience @apc_add($key . '.lock', '', 5); } private function removeLock($key) { // suppress all warnings, if some other process removed it that's ok too @apc_delete($key . '.lock'); } private function waitForLock($key) { // 20 x 250 = 5 seconds $tries = 20; $cnt = 0; do { // 250 ms is a long time to sleep, but it does stop the server from burning all resources on polling locks.. usleep(250); $cnt ++; } while ($cnt <= $tries && $this->isLocked($key)); if ($this->isLocked($key)) { // 5 seconds passed, assume the owning process died off and remove it $this->removeLock($key); } } /** * @inheritDoc */ public function get($key, $expiration = false) { if (($ret = @apc_fetch($key)) === false) { return false; } if (!$expiration || (time() - $ret['time'] > $expiration)) { $this->delete($key); return false; } return unserialize($ret['data']); } /** * @inheritDoc */ public function set($key, $value) { if (@apc_store($key, array('time' => time(), 'data' => serialize($value))) == false) { throw new apiCacheException("Couldn't store data"); } } /** * @inheritDoc */ public function delete($key) { @apc_delete($key); } }