text: // Copyright 2013 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef CHROME_BROWSER_NET_TIMED_CACHE_H_
  #define CHROME_BROWSER_NET_TIMED_CACHE_H_
  
  #include "base/containers/mru_cache.h"
  #include "base/macros.h"
  #include "base/time/time.h"
  
  class GURL;
  
  namespace chrome_browser_net {
  
  // Define a LRU cache that recalls all navigations within the last N seconds.
  // When we learn about subresources to possibly preconnect to, it would be a
  // waste to preconnect when the original navigation was too long ago.  Any
  // connected, but unused TCP/IP connection, will generally be reset by the
  // server if it is not used quickly (i.e., GET or POST is sent).
  class TimedCache {
   public:
    explicit TimedCache(const base::TimeDelta& max_duration);
    ~TimedCache();
  
    // Evicts any entries that have been in the FIFO "too long," and then checks
    // to see if the given url is (still) in the FIFO cache.
    bool WasRecentlySeen(const GURL& url);
  
    // Adds the given url to the cache, where it will remain for max_duration_.
    void SetRecentlySeen(const GURL& url);
  
   private:
    // Our cache will be keyed on a URL (actually, just a scheme/host/port).
    // We will always track the time it was last added to the FIFO cache by
    // remembering a TimeTicks value.
    typedef base::MRUCache<GURL, base::TimeTicks> UrlMruTimedCache;
    UrlMruTimedCache mru_cache_;
  
    // The longest time an entry can persist in the cache, and still be found.
    const base::TimeDelta max_duration_;
  
    DISALLOW_COPY_AND_ASSIGN(TimedCache);
  };
  
  }  // namespace chrome_browser_net
  
  #endif  // CHROME_BROWSER_NET_TIMED_CACHE_H_
  