PHP Classes

File: example/GoogleClient/cache/Google_MemcacheCache.php

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  Classes of Vivek Muthal   Viv OAuth IMAP   example/GoogleClient/cache/Google_MemcacheCache.php   Download  
File: example/GoogleClient/cache/Google_MemcacheCache.php
Role: Example script
Content type: text/plain
Description: Example script
Class: Viv OAuth IMAP
Access messages in IMAP server using OAuth token
Author: By
Last change: Update of example/GoogleClient/cache/Google_MemcacheCache.php
Date: 9 months ago
Size: 3,994 bytes
 

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<?php
/*
 * Copyright 2008 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 memcache, which is not
 * really very persistent, as soon as you restart your memcache daemon
 * 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 Google_MemcacheCache extends Google_Cache {
  private
$connection = false;

  public function
__construct() {
    global
$apiConfig;
    if (!
function_exists('memcache_connect')) {
      throw new
Google_CacheException("Memcache functions not available");
    }
   
$this->host = $apiConfig['ioMemCacheCache_host'];
   
$this->port = $apiConfig['ioMemCacheCache_port'];
    if (empty(
$this->host) || empty($this->port)) {
      throw new
Google_CacheException("You need to supply a valid memcache host and port");
    }
  }

  private function
isLocked($key) {
   
$this->check();
    if ((@
memcache_get($this->connection, $key . '.lock')) === false) {
      return
false;
    }
    return
true;
  }

  private function
createLock($key) {
   
$this->check();
   
// the interesting thing is that this could fail if the lock was created in the meantime..
    // but we'll ignore that out of convenience
   
@memcache_add($this->connection, $key . '.lock', '', 0, 5);
  }

  private function
removeLock($key) {
   
$this->check();
   
// suppress all warnings, if some other process removed it that's ok too
   
@memcache_delete($this->connection, $key . '.lock');
  }

  private function
waitForLock($key) {
   
$this->check();
   
// 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);
    }
  }

 
// I prefer lazy initialization since the cache isn't used every request
  // so this potentially saves a lot of overhead
 
private function connect() {
    if (!
$this->connection = @memcache_pconnect($this->host, $this->port)) {
      throw new
Google_CacheException("Couldn't connect to memcache server");
    }
  }

  private function
check() {
    if (!
$this->connection) {
     
$this->connect();
    }
  }

 
/**
   * @inheritDoc
   */
 
public function get($key, $expiration = false) {
   
$this->check();
    if ((
$ret = @memcache_get($this->connection, $key)) === false) {
      return
false;
    }
    if (
is_numeric($expiration) && (time() - $ret['time'] > $expiration)) {
     
$this->delete($key);
      return
false;
    }
    return
$ret['data'];
  }

 
/**
   * @inheritDoc
   * @param string $key
   * @param string $value
   * @throws Google_CacheException
   */
 
public function set($key, $value) {
   
$this->check();
   
// we store it with the cache_time default expiration so objects will at least get cleaned eventually.
   
if (@memcache_set($this->connection, $key, array('time' => time(),
       
'data' => $value), false) == false) {
      throw new
Google_CacheException("Couldn't store data in cache");
    }
  }

 
/**
   * @inheritDoc
   * @param String $key
   */
 
public function delete($key) {
   
$this->check();
    @
memcache_delete($this->connection, $key);
  }
}