Home | History | Annotate | Download | only in base 
      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef NET_BASE_HOST_CACHE_H_
      6 #define NET_BASE_HOST_CACHE_H_
      7 #pragma once
      8 
      9 #include <map>
     10 #include <string>
     11 
     12 #include "base/gtest_prod_util.h"
     13 #include "base/memory/ref_counted.h"
     14 #include "base/threading/non_thread_safe.h"
     15 #include "base/time.h"
     16 #include "net/base/address_family.h"
     17 #include "net/base/address_list.h"
     18 
     19 namespace net {
     20 
     21 // Cache used by HostResolver to map hostnames to their resolved result.
     22 class HostCache : public base::NonThreadSafe {
     23  public:
     24   // Stores the latest address list that was looked up for a hostname.
     25   struct Entry : public base::RefCounted<Entry> {
     26     Entry(int error, const AddressList& addrlist, base::TimeTicks expiration);
     27 
     28     // The resolve results for this entry.
     29     int error;
     30     AddressList addrlist;
     31 
     32     // The time when this entry expires.
     33     base::TimeTicks expiration;
     34 
     35    private:
     36     friend class base::RefCounted<Entry>;
     37 
     38     ~Entry();
     39   };
     40 
     41   struct Key {
     42     Key(const std::string& hostname, AddressFamily address_family,
     43         HostResolverFlags host_resolver_flags)
     44         : hostname(hostname),
     45           address_family(address_family),
     46           host_resolver_flags(host_resolver_flags) {}
     47 
     48     bool operator==(const Key& other) const {
     49       // |address_family| and |host_resolver_flags| are compared before
     50       // |hostname| under assumption that integer comparisons are faster than
     51       // string comparisons.
     52       return (other.address_family == address_family &&
     53               other.host_resolver_flags == host_resolver_flags &&
     54               other.hostname == hostname);
     55     }
     56 
     57     bool operator<(const Key& other) const {
     58       // |address_family| and |host_resolver_flags| are compared before
     59       // |hostname| under assumption that integer comparisons are faster than
     60       // string comparisons.
     61       if (address_family != other.address_family)
     62         return address_family < other.address_family;
     63       if (host_resolver_flags != other.host_resolver_flags)
     64         return host_resolver_flags < other.host_resolver_flags;
     65       return hostname < other.hostname;
     66     }
     67 
     68     std::string hostname;
     69     AddressFamily address_family;
     70     HostResolverFlags host_resolver_flags;
     71   };
     72 
     73   typedef std::map<Key, scoped_refptr<Entry> > EntryMap;
     74 
     75   // Constructs a HostCache that caches successful host resolves for
     76   // |success_entry_ttl| time, and failed host resolves for
     77   // |failure_entry_ttl|. The cache will store up to |max_entries|.
     78   HostCache(size_t max_entries,
     79             base::TimeDelta success_entry_ttl,
     80             base::TimeDelta failure_entry_ttl);
     81 
     82   ~HostCache();
     83 
     84   // Returns a pointer to the entry for |key|, which is valid at time
     85   // |now|. If there is no such entry, returns NULL.
     86   const Entry* Lookup(const Key& key, base::TimeTicks now) const;
     87 
     88   // Overwrites or creates an entry for |key|. Returns the pointer to the
     89   // entry, or NULL on failure (fails if caching is disabled).
     90   // (|error|, |addrlist|) is the value to set, and |now| is the current
     91   // timestamp.
     92   Entry* Set(const Key& key,
     93              int error,
     94              const AddressList& addrlist,
     95              base::TimeTicks now);
     96 
     97   // Empties the cache
     98   void clear();
     99 
    100   // Returns the number of entries in the cache.
    101   size_t size() const;
    102 
    103   // Following are used by net_internals UI.
    104   size_t max_entries() const;
    105 
    106   base::TimeDelta success_entry_ttl() const;
    107 
    108   base::TimeDelta failure_entry_ttl() const;
    109 
    110   // Note that this map may contain expired entries.
    111   const EntryMap& entries() const;
    112 
    113  private:
    114   FRIEND_TEST_ALL_PREFIXES(HostCacheTest, Compact);
    115   FRIEND_TEST_ALL_PREFIXES(HostCacheTest, NoCache);
    116 
    117   // Returns true if this cache entry's result is valid at time |now|.
    118   static bool CanUseEntry(const Entry* entry, const base::TimeTicks now);
    119 
    120   // Prunes entries from the cache to bring it below max entry bound. Entries
    121   // matching |pinned_entry| will NOT be pruned.
    122   void Compact(base::TimeTicks now, const Entry* pinned_entry);
    123 
    124   // Returns true if this HostCache can contain no entries.
    125   bool caching_is_disabled() const {
    126     return max_entries_ == 0;
    127   }
    128 
    129   // Bound on total size of the cache.
    130   size_t max_entries_;
    131 
    132   // Time to live for cache entries.
    133   base::TimeDelta success_entry_ttl_;
    134   base::TimeDelta failure_entry_ttl_;
    135 
    136   // Map from hostname (presumably in lowercase canonicalized format) to
    137   // a resolved result entry.
    138   EntryMap entries_;
    139 
    140   DISALLOW_COPY_AND_ASSIGN(HostCache);
    141 };
    142 
    143 }  // namespace net
    144 
    145 #endif  // NET_BASE_HOST_CACHE_H_
    146