<?php
  /*
   *  $Id$
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   * This software consists of voluntary contributions made by many individuals
   * and is licensed under the MIT license. For more information, see
   * <http://www.doctrine-project.org>.
   */
  
  namespace Doctrine\Common\Cache;
  
  /**
   * Interface for cache drivers.
   *
   * @license http://www.opensource.org/licenses/lgpl-license.php LGPL
   * @link    www.doctrine-project.org
   * @since   2.0
   * @author  Benjamin Eberlei <kontakt@beberlei.de>
   * @author  Guilherme Blanco <guilhermeblanco@hotmail.com>
   * @author  Jonathan Wage <jonwage@gmail.com>
   * @author  Roman Borschel <roman@code-factory.org>
   * @author  Fabio B. Silva <fabio.bat.silva@gmail.com>
   */
  interface Cache
  {
      const STATS_HITS    = 'hits';
      const STATS_MISSES  = 'misses';
      const STATS_UPTIME  = 'uptime';
      const STATS_MEMORY_USAGE        = 'memory_usage';
      const STATS_MEMORY_AVAILIABLE   = 'memory_available';
  
      /**
       * Fetches an entry from the cache.
       *
       * @param string $id cache id The id of the cache entry to fetch.
       * @return mixed The cached data or FALSE, if no cache entry exists for the given id.
       */
      function fetch($id);
  
      /**
       * Test if an entry exists in the cache.
       *
       * @param string $id cache id The cache id of the entry to check for.
       * @return boolean TRUE if a cache entry exists for the given cache id, FALSE otherwise.
       */
      function contains($id);
  
      /**
       * Puts data into the cache.
       *
       * @param string $id The cache id.
       * @param mixed $data The cache entry/data.
       * @param int $lifeTime The lifetime. If != 0, sets a specific lifetime for this cache entry (0 => infinite lifeTime).
       * @return boolean TRUE if the entry was successfully stored in the cache, FALSE otherwise.
       */
      function save($id, $data, $lifeTime = 0);
  
      /**
       * Deletes a cache entry.
       *
       * @param string $id cache id
       * @return boolean TRUE if the cache entry was successfully deleted, FALSE otherwise.
       */
      function delete($id);
  
      /**
       * Retrieves cached information from data store
       *
       * The server's statistics array has the following values:
       *
       * - <b>hits</b>
       * Number of keys that have been requested and found present.
       *
       * - <b>misses</b>
       * Number of items that have been requested and not found.
       *
       * - <b>uptime</b>
       * Time that the server is running.
       *
       * - <b>memory_usage</b>
       * Memory used by this server to store items.
       *
       * - <b>memory_available</b>
       * Memory allowed to use for storage.
       *
       * @since   2.2
       * @var     array Associative array with server's statistics if available, NULL otherwise.
       */
      function getStats();
  }