wp-database-backup / includes / admin / Destination / Google / google-api-php-client / src / cache / Google_ApcCache.php

Google_ApcCache.php in WP Database Backup – Unlimited Database & Files Backup by Backup for WP 6.11, at includes/admin/Destination/Google/google-api-php-client/src/cache/Google_ApcCache.php

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1	<?php
2	/*
3	* Copyright 2010 Google Inc.
4	*
5	* Licensed under the Apache License, Version 2.0 (the "License");
6	* you may not use this file except in compliance with the License.
7	* You may obtain a copy of the License at
8	*
9	* http://www.apache.org/licenses/LICENSE-2.0
10	*
11	* Unless required by applicable law or agreed to in writing, software
12	* distributed under the License is distributed on an "AS IS" BASIS,
13	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14	* See the License for the specific language governing permissions and
15	* limitations under the License.
16	*/
17
18	/**
19	* A persistent storage class based on the APC cache, which is not
20	* really very persistent, as soon as you restart your web server
21	* the storage will be wiped, however for debugging and/or speed
22	* it can be useful, kinda, and cache is a lot cheaper then storage.
23	*
24	* @author Chris Chabot <chabotc@google.com>
25	*/
26	class googleApcCache extends Google_Cache {
27
28	public function __construct() {
29	if (! function_exists('apc_add')) {
30	throw new Google_CacheException("Apc functions not available");
31	}
32	}
33
34	private function isLocked($key) {
35	if ((@apc_fetch($key . '.lock')) === false) {
36	return false;
37	}
38	return true;
39	}
40
41	private function createLock($key) {
42	// the interesting thing is that this could fail if the lock was created in the meantime..
43	// but we'll ignore that out of convenience
44	@apc_add($key . '.lock', '', 5);
45	}
46
47	private function removeLock($key) {
48	// suppress all warnings, if some other process removed it that's ok too
49	@apc_delete($key . '.lock');
50	}
51
52	private function waitForLock($key) {
53	// 20 x 250 = 5 seconds
54	$tries = 20;
55	$cnt = 0;
56	do {
57	// 250 ms is a long time to sleep, but it does stop the server from burning all resources on polling locks..
58	usleep(250);
59	$cnt ++;
60	} while ($cnt <= $tries && $this->isLocked($key));
61	if ($this->isLocked($key)) {
62	// 5 seconds passed, assume the owning process died off and remove it
63	$this->removeLock($key);
64	}
65	}
66
67	/**
68	* @inheritDoc
69	*/
70	public function get($key, $expiration = false) {
71
72	if (($ret = @apc_fetch($key)) === false) {
73	return false;
74	}
75	if (!$expiration \|\| (time() - $ret['time'] > $expiration)) {
76	$this->delete($key);
77	return false;
78	}
79	return unserialize($ret['data']);
80	}
81
82	/**
83	* @inheritDoc
84	*/
85	public function set($key, $value) {
86	if (@apc_store($key, array('time' => time(), 'data' => serialize($value))) == false) {
87	throw new Google_CacheException("Couldn't store data");
88	}
89	}
90
91	/**
92	* @inheritDoc
93	* @param String $key
94	*/
95	public function delete($key) {
96	@apc_delete($key);
97	}
98	}
99