Store.php

<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * This code is partially based on the Rack-Cache library by Ryan Tomayko,
 * which is released under the MIT license.
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */
namespace Symfony\Component\HttpKernel\HttpCache;

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

/**
 * Store implements all the logic for storing cache metadata (Request and Response headers).
 *
 * @author Fabien Potencier <fabien@symfony.com>
 */
class Store implements StoreInterface {
  protected $root;
  private $keyCache;
  private $locks;

  /**
   * Constructor.
   *
   * @param string $root The path to the cache directory
   */
  public function __construct($root) {
    $this->root = $root;
    if (!is_dir($this->root)) {
      mkdir($this->root, 0777, true);
    }
    $this->keyCache = new \SplObjectStorage();
    $this->locks = array();
  }

  /**
   * Cleanups storage.
   */
  public function cleanup() {

    // unlock everything
    foreach ($this->locks as $lock) {
      @unlink($lock);
    }
    $error = error_get_last();
    if (1 === $error['type'] && false === headers_sent()) {

      // send a 503
      header('HTTP/1.0 503 Service Unavailable');
      header('Retry-After: 10');
      echo '503 Service Unavailable';
    }
  }

  /**
   * Locks the cache for a given Request.
   *
   * @param Request $request A Request instance
   *
   * @return Boolean|string true if the lock is acquired, the path to the current lock otherwise
   */
  public function lock(Request $request) {
    $path = $this
      ->getPath($this
      ->getCacheKey($request) . '.lck');
    if (!is_dir(dirname($path)) && false === @mkdir(dirname($path), 0777, true)) {
      return false;
    }
    $lock = @fopen($path, 'x');
    if (false !== $lock) {
      fclose($lock);
      $this->locks[] = $path;
      return true;
    }
    return !file_exists($path) ?: $path;
  }

  /**
   * Releases the lock for the given Request.
   *
   * @param Request $request A Request instance
   *
   * @return Boolean False if the lock file does not exist or cannot be unlocked, true otherwise
   */
  public function unlock(Request $request) {
    $file = $this
      ->getPath($this
      ->getCacheKey($request) . '.lck');
    return is_file($file) ? @unlink($file) : false;
  }
  public function isLocked(Request $request) {
    return is_file($this
      ->getPath($this
      ->getCacheKey($request) . '.lck'));
  }

  /**
   * Locates a cached Response for the Request provided.
   *
   * @param Request $request A Request instance
   *
   * @return Response|null A Response instance, or null if no cache entry was found
   */
  public function lookup(Request $request) {
    $key = $this
      ->getCacheKey($request);
    if (!($entries = $this
      ->getMetadata($key))) {
      return null;
    }

    // find a cached entry that matches the request.
    $match = null;
    foreach ($entries as $entry) {
      if ($this
        ->requestsMatch(isset($entry[1]['vary'][0]) ? $entry[1]['vary'][0] : '', $request->headers
        ->all(), $entry[0])) {
        $match = $entry;
        break;
      }
    }
    if (null === $match) {
      return null;
    }
    list($req, $headers) = $match;
    if (is_file($body = $this
      ->getPath($headers['x-content-digest'][0]))) {
      return $this
        ->restoreResponse($headers, $body);
    }

    // TODO the metaStore referenced an entity that doesn't exist in
    // the entityStore. We definitely want to return nil but we should
    // also purge the entry from the meta-store when this is detected.
    return null;
  }

  /**
   * Writes a cache entry to the store for the given Request and Response.
   *
   * Existing entries are read and any that match the response are removed. This
   * method calls write with the new list of cache entries.
   *
   * @param Request  $request  A Request instance
   * @param Response $response A Response instance
   *
   * @return string The key under which the response is stored
   *
   * @throws \RuntimeException
   */
  public function write(Request $request, Response $response) {
    $key = $this
      ->getCacheKey($request);
    $storedEnv = $this
      ->persistRequest($request);

    // write the response body to the entity store if this is the original response
    if (!$response->headers
      ->has('X-Content-Digest')) {
      $digest = $this
        ->generateContentDigest($response);
      if (false === $this
        ->save($digest, $response
        ->getContent())) {
        throw new \RuntimeException('Unable to store the entity.');
      }
      $response->headers
        ->set('X-Content-Digest', $digest);
      if (!$response->headers
        ->has('Transfer-Encoding')) {
        $response->headers
          ->set('Content-Length', strlen($response
          ->getContent()));
      }
    }

    // read existing cache entries, remove non-varying, and add this one to the list
    $entries = array();
    $vary = $response->headers
      ->get('vary');
    foreach ($this
      ->getMetadata($key) as $entry) {
      if (!isset($entry[1]['vary'][0])) {
        $entry[1]['vary'] = array(
          '',
        );
      }
      if ($vary != $entry[1]['vary'][0] || !$this
        ->requestsMatch($vary, $entry[0], $storedEnv)) {
        $entries[] = $entry;
      }
    }
    $headers = $this
      ->persistResponse($response);
    unset($headers['age']);
    array_unshift($entries, array(
      $storedEnv,
      $headers,
    ));
    if (false === $this
      ->save($key, serialize($entries))) {
      throw new \RuntimeException('Unable to store the metadata.');
    }
    return $key;
  }

  /**
   * Returns content digest for $response.
   *
   * @param Response $response
   *
   * @return string
   */
  protected function generateContentDigest(Response $response) {
    return 'en' . sha1($response
      ->getContent());
  }

  /**
   * Invalidates all cache entries that match the request.
   *
   * @param Request $request A Request instance
   *
   * @throws \RuntimeException
   */
  public function invalidate(Request $request) {
    $modified = false;
    $key = $this
      ->getCacheKey($request);
    $entries = array();
    foreach ($this
      ->getMetadata($key) as $entry) {
      $response = $this
        ->restoreResponse($entry[1]);
      if ($response
        ->isFresh()) {
        $response
          ->expire();
        $modified = true;
        $entries[] = array(
          $entry[0],
          $this
            ->persistResponse($response),
        );
      }
      else {
        $entries[] = $entry;
      }
    }
    if ($modified) {
      if (false === $this
        ->save($key, serialize($entries))) {
        throw new \RuntimeException('Unable to store the metadata.');
      }
    }
  }

  /**
   * Determines whether two Request HTTP header sets are non-varying based on
   * the vary response header value provided.
   *
   * @param string $vary A Response vary header
   * @param array  $env1 A Request HTTP header array
   * @param array  $env2 A Request HTTP header array
   *
   * @return Boolean true if the two environments match, false otherwise
   */
  private function requestsMatch($vary, $env1, $env2) {
    if (empty($vary)) {
      return true;
    }
    foreach (preg_split('/[\\s,]+/', $vary) as $header) {
      $key = strtr(strtolower($header), '_', '-');
      $v1 = isset($env1[$key]) ? $env1[$key] : null;
      $v2 = isset($env2[$key]) ? $env2[$key] : null;
      if ($v1 !== $v2) {
        return false;
      }
    }
    return true;
  }

  /**
   * Gets all data associated with the given key.
   *
   * Use this method only if you know what you are doing.
   *
   * @param string $key The store key
   *
   * @return array An array of data associated with the key
   */
  private function getMetadata($key) {
    if (false === ($entries = $this
      ->load($key))) {
      return array();
    }
    return unserialize($entries);
  }

  /**
   * Purges data for the given URL.
   *
   * @param string $url A URL
   *
   * @return Boolean true if the URL exists and has been purged, false otherwise
   */
  public function purge($url) {
    if (is_file($path = $this
      ->getPath($this
      ->getCacheKey(Request::create($url))))) {
      unlink($path);
      return true;
    }
    return false;
  }

  /**
   * Loads data for the given key.
   *
   * @param string $key The store key
   *
   * @return string The data associated with the key
   */
  private function load($key) {
    $path = $this
      ->getPath($key);
    return is_file($path) ? file_get_contents($path) : false;
  }

  /**
   * Save data for the given key.
   *
   * @param string $key  The store key
   * @param string $data The data to store
   *
   * @return Boolean
   */
  private function save($key, $data) {
    $path = $this
      ->getPath($key);
    if (!is_dir(dirname($path)) && false === @mkdir(dirname($path), 0777, true)) {
      return false;
    }
    $tmpFile = tempnam(dirname($path), basename($path));
    if (false === ($fp = @fopen($tmpFile, 'wb'))) {
      return false;
    }
    @fwrite($fp, $data);
    @fclose($fp);
    if ($data != file_get_contents($tmpFile)) {
      return false;
    }
    if (false === @rename($tmpFile, $path)) {
      return false;
    }
    @chmod($path, 0666 & ~umask());
  }
  public function getPath($key) {
    return $this->root . DIRECTORY_SEPARATOR . substr($key, 0, 2) . DIRECTORY_SEPARATOR . substr($key, 2, 2) . DIRECTORY_SEPARATOR . substr($key, 4, 2) . DIRECTORY_SEPARATOR . substr($key, 6);
  }

  /**
   * Returns a cache key for the given Request.
   *
   * @param Request $request A Request instance
   *
   * @return string A key for the given Request
   */
  private function getCacheKey(Request $request) {
    if (isset($this->keyCache[$request])) {
      return $this->keyCache[$request];
    }
    return $this->keyCache[$request] = 'md' . sha1($request
      ->getUri());
  }

  /**
   * Persists the Request HTTP headers.
   *
   * @param Request $request A Request instance
   *
   * @return array An array of HTTP headers
   */
  private function persistRequest(Request $request) {
    return $request->headers
      ->all();
  }

  /**
   * Persists the Response HTTP headers.
   *
   * @param Response $response A Response instance
   *
   * @return array An array of HTTP headers
   */
  private function persistResponse(Response $response) {
    $headers = $response->headers
      ->all();
    $headers['X-Status'] = array(
      $response
        ->getStatusCode(),
    );
    return $headers;
  }

  /**
   * Restores a Response from the HTTP headers and body.
   *
   * @param array  $headers An array of HTTP headers for the Response
   * @param string $body    The Response body
   *
   * @return Response
   */
  private function restoreResponse($headers, $body = null) {
    $status = $headers['X-Status'][0];
    unset($headers['X-Status']);
    if (null !== $body) {
      $headers['X-Body-File'] = array(
        $body,
      );
    }
    return new Response($body, $status, $headers);
  }

}