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Differences Between: [Versions 310 and 402] [Versions 311 and 402] [Versions 39 and 402] [Versions 400 and 402] [Versions 401 and 402]

   1  <?php
   2  /*
   3   * Copyright 2012 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  if (!class_exists('Google_Client')) {
  19    require_once dirname(__FILE__) . '/../autoload.php';
  20  }
  21  
  22  /**
  23   * Implement the caching directives specified in rfc2616. This
  24   * implementation is guided by the guidance offered in rfc2616-sec13.
  25   */
  26  #[AllowDynamicProperties]
  27  class Google_Http_CacheParser
  28  {
  29    public static $CACHEABLE_HTTP_METHODS = array('GET', 'HEAD');
  30    public static $CACHEABLE_STATUS_CODES = array('200', '203', '300', '301');
  31  
  32    /**
  33     * Check if an HTTP request can be cached by a private local cache.
  34     *
  35     * @static
  36     * @param Google_Http_Request $resp
  37     * @return bool True if the request is cacheable.
  38     * False if the request is uncacheable.
  39     */
  40    public static function isRequestCacheable(Google_Http_Request $resp)
  41    {
  42      $method = $resp->getRequestMethod();
  43      if (! in_array($method, self::$CACHEABLE_HTTP_METHODS)) {
  44        return false;
  45      }
  46  
  47      // Don't cache authorized requests/responses.
  48      // [rfc2616-14.8] When a shared cache receives a request containing an
  49      // Authorization field, it MUST NOT return the corresponding response
  50      // as a reply to any other request...
  51      if ($resp->getRequestHeader("authorization")) {
  52        return false;
  53      }
  54  
  55      return true;
  56    }
  57  
  58    /**
  59     * Check if an HTTP response can be cached by a private local cache.
  60     *
  61     * @static
  62     * @param Google_Http_Request $resp
  63     * @return bool True if the response is cacheable.
  64     * False if the response is un-cacheable.
  65     */
  66    public static function isResponseCacheable(Google_Http_Request $resp)
  67    {
  68      // First, check if the HTTP request was cacheable before inspecting the
  69      // HTTP response.
  70      if (false == self::isRequestCacheable($resp)) {
  71        return false;
  72      }
  73  
  74      $code = $resp->getResponseHttpCode();
  75      if (! in_array($code, self::$CACHEABLE_STATUS_CODES)) {
  76        return false;
  77      }
  78  
  79      // The resource is uncacheable if the resource is already expired and
  80      // the resource doesn't have an ETag for revalidation.
  81      $etag = $resp->getResponseHeader("etag");
  82      if (self::isExpired($resp) && $etag == false) {
  83        return false;
  84      }
  85  
  86      // [rfc2616-14.9.2]  If [no-store is] sent in a response, a cache MUST NOT
  87      // store any part of either this response or the request that elicited it.
  88      $cacheControl = $resp->getParsedCacheControl();
  89      if (isset($cacheControl['no-store'])) {
  90        return false;
  91      }
  92  
  93      // Pragma: no-cache is an http request directive, but is occasionally
  94      // used as a response header incorrectly.
  95      $pragma = $resp->getResponseHeader('pragma');
  96      if ($pragma == 'no-cache' || strpos($pragma, 'no-cache') !== false) {
  97        return false;
  98      }
  99  
 100      // [rfc2616-14.44] Vary: * is extremely difficult to cache. "It implies that
 101      // a cache cannot determine from the request headers of a subsequent request
 102      // whether this response is the appropriate representation."
 103      // Given this, we deem responses with the Vary header as uncacheable.
 104      $vary = $resp->getResponseHeader('vary');
 105      if ($vary) {
 106        return false;
 107      }
 108  
 109      return true;
 110    }
 111  
 112    /**
 113     * @static
 114     * @param Google_Http_Request $resp
 115     * @return bool True if the HTTP response is considered to be expired.
 116     * False if it is considered to be fresh.
 117     */
 118    public static function isExpired(Google_Http_Request $resp)
 119    {
 120      // HTTP/1.1 clients and caches MUST treat other invalid date formats,
 121      // especially including the value “0”, as in the past.
 122      $parsedExpires = false;
 123      $responseHeaders = $resp->getResponseHeaders();
 124  
 125      if (isset($responseHeaders['expires'])) {
 126        $rawExpires = $responseHeaders['expires'];
 127        // Check for a malformed expires header first.
 128        if (empty($rawExpires) || (is_numeric($rawExpires) && $rawExpires <= 0)) {
 129          return true;
 130        }
 131  
 132        // See if we can parse the expires header.
 133        $parsedExpires = strtotime($rawExpires);
 134        if (false == $parsedExpires || $parsedExpires <= 0) {
 135          return true;
 136        }
 137      }
 138  
 139      // Calculate the freshness of an http response.
 140      $freshnessLifetime = false;
 141      $cacheControl = $resp->getParsedCacheControl();
 142      if (isset($cacheControl['max-age'])) {
 143        $freshnessLifetime = $cacheControl['max-age'];
 144      }
 145  
 146      $rawDate = $resp->getResponseHeader('date');
 147      $parsedDate = strtotime($rawDate);
 148  
 149      if (empty($rawDate) || false == $parsedDate) {
 150        // We can't default this to now, as that means future cache reads
 151        // will always pass with the logic below, so we will require a
 152        // date be injected if not supplied.
 153        throw new Google_Exception("All cacheable requests must have creation dates.");
 154      }
 155  
 156      if (false == $freshnessLifetime && isset($responseHeaders['expires'])) {
 157        $freshnessLifetime = $parsedExpires - $parsedDate;
 158      }
 159  
 160      if (false == $freshnessLifetime) {
 161        return true;
 162      }
 163  
 164      // Calculate the age of an http response.
 165      $age = max(0, time() - $parsedDate);
 166      if (isset($responseHeaders['age'])) {
 167        $age = max($age, strtotime($responseHeaders['age']));
 168      }
 169  
 170      return $freshnessLifetime <= $age;
 171    }
 172  
 173    /**
 174     * Determine if a cache entry should be revalidated with by the origin.
 175     *
 176     * @param Google_Http_Request $response
 177     * @return bool True if the entry is expired, else return false.
 178     */
 179    public static function mustRevalidate(Google_Http_Request $response)
 180    {
 181      // [13.3] When a cache has a stale entry that it would like to use as a
 182      // response to a client's request, it first has to check with the origin
 183      // server to see if its cached entry is still usable.
 184      return self::isExpired($response);
 185    }
 186  }