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File: example/GoogleClient/cache/Google_FileCache.php

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  Classes of Vivek Muthal  >  Viv OAuth IMAP  >  example/GoogleClient/cache/Google_FileCache.php  >  Download  
File: example/GoogleClient/cache/Google_FileCache.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:
Date: 1 year ago
Size: 4,920 bytes
 

Contents

Class file image Download
<?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.
 */

/*
 * This class implements a basic on disk storage. While that does
 * work quite well it's not the most elegant and scalable solution.
 * It will also get you into a heap of trouble when you try to run
 * this in a clustered environment. In those cases please use the
 * MySql back-end
 *
 * @author Chris Chabot <chabotc@google.com>
 */
class Google_FileCache extends Google_Cache {
  private
$path;

  public function
__construct() {
    global
$apiConfig;
   
$this->path = $apiConfig['ioFileCache_directory'];
  }

  private function
isLocked($storageFile) {
   
// our lock file convention is simple: /the/file/path.lock
   
return file_exists($storageFile . '.lock');
  }

  private function
createLock($storageFile) {
   
$storageDir = dirname($storageFile);
    if (!
is_dir($storageDir)) {
     
// @codeCoverageIgnoreStart
     
if (! @mkdir($storageDir, 0755, true)) {
       
// make sure the failure isn't because of a concurrency issue
       
if (! is_dir($storageDir)) {
          throw new
Google_CacheException("Could not create storage directory: $storageDir");
        }
      }
     
// @codeCoverageIgnoreEnd
   
}
    @
touch($storageFile . '.lock');
  }

  private function
removeLock($storageFile) {
   
// suppress all warnings, if some other process removed it that's ok too
   
@unlink($storageFile . '.lock');
  }

  private function
waitForLock($storageFile) {
   
// 20 x 250 = 5 seconds
   
$tries = 20;
   
$cnt = 0;
    do {
     
// make sure PHP picks up on file changes. This is an expensive action but really can't be avoided
     
clearstatcache();
     
// 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 && $this->isLocked($storageFile));
    if (
$this->isLocked($storageFile)) {
     
// 5 seconds passed, assume the owning process died off and remove it
     
$this->removeLock($storageFile);
    }
  }

  private function
getCacheDir($hash) {
   
// use the first 2 characters of the hash as a directory prefix
    // this should prevent slowdowns due to huge directory listings
    // and thus give some basic amount of scalability
   
return $this->path . '/' . substr($hash, 0, 2);
  }

  private function
getCacheFile($hash) {
    return
$this->getCacheDir($hash) . '/' . $hash;
  }

  public function
get($key, $expiration = false) {
   
$storageFile = $this->getCacheFile(md5($key));
   
// See if this storage file is locked, if so we wait up to 5 seconds for the lock owning process to
    // complete it's work. If the lock is not released within that time frame, it's cleaned up.
    // This should give us a fair amount of 'Cache Stampeding' protection
   
if ($this->isLocked($storageFile)) {
     
$this->waitForLock($storageFile);
    }
    if (
file_exists($storageFile) && is_readable($storageFile)) {
     
$now = time();
      if (!
$expiration || (($mtime = @filemtime($storageFile)) !== false && ($now - $mtime) < $expiration)) {
        if ((
$data = @file_get_contents($storageFile)) !== false) {
         
$data = unserialize($data);
          return
$data;
        }
      }
    }
    return
false;
  }

  public function
set($key, $value) {
   
$storageDir = $this->getCacheDir(md5($key));
   
$storageFile = $this->getCacheFile(md5($key));
    if (
$this->isLocked($storageFile)) {
     
// some other process is writing to this file too, wait until it's done to prevent hiccups
     
$this->waitForLock($storageFile);
    }
    if (!
is_dir($storageDir)) {
      if (! @
mkdir($storageDir, 0755, true)) {
        throw new
Google_CacheException("Could not create storage directory: $storageDir");
      }
    }
   
// we serialize the whole request object, since we don't only want the
    // responseContent but also the postBody used, headers, size, etc
   
$data = serialize($value);
   
$this->createLock($storageFile);
    if (! @
file_put_contents($storageFile, $data)) {
     
$this->removeLock($storageFile);
      throw new
Google_CacheException("Could not store data in the file");
    }
   
$this->removeLock($storageFile);
  }

  public function
delete($key) {
   
$file = $this->getCacheFile(md5($key));
    if (! @
unlink($file)) {
      throw new
Google_CacheException("Cache file could not be deleted");
    }
  }
}