1// Copyright (c) 2012 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_DNS_HOST_CACHE_H_
6#define NET_DNS_HOST_CACHE_H_
7
8#include <functional>
9#include <string>
10
11#include "base/gtest_prod_util.h"
12#include "base/memory/scoped_ptr.h"
13#include "base/threading/non_thread_safe.h"
14#include "base/time/time.h"
15#include "net/base/address_family.h"
16#include "net/base/address_list.h"
17#include "net/base/expiring_cache.h"
18#include "net/base/net_export.h"
19
20namespace net {
21
22// Cache used by HostResolver to map hostnames to their resolved result.
23class NET_EXPORT HostCache : NON_EXPORTED_BASE(public base::NonThreadSafe) {
24 public:
25  // Stores the latest address list that was looked up for a hostname.
26  struct NET_EXPORT Entry {
27    Entry(int error, const AddressList& addrlist, base::TimeDelta ttl);
28    // Use when |ttl| is unknown.
29    Entry(int error, const AddressList& addrlist);
30    ~Entry();
31
32    bool has_ttl() const { return ttl >= base::TimeDelta(); }
33
34    // The resolve results for this entry.
35    int error;
36    AddressList addrlist;
37    // TTL obtained from the nameserver. Negative if unknown.
38    base::TimeDelta ttl;
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      if (address_family != other.address_family)
53        return address_family < other.address_family;
54      if (host_resolver_flags != other.host_resolver_flags)
55        return host_resolver_flags < other.host_resolver_flags;
56      return hostname < other.hostname;
57    }
58
59    std::string hostname;
60    AddressFamily address_family;
61    HostResolverFlags host_resolver_flags;
62  };
63
64  struct EvictionHandler {
65    void Handle(const Key& key,
66                const Entry& entry,
67                const base::TimeTicks& expiration,
68                const base::TimeTicks& now,
69                bool onGet) const;
70  };
71
72  typedef ExpiringCache<Key, Entry, base::TimeTicks,
73                        std::less<base::TimeTicks>,
74                        EvictionHandler> EntryMap;
75
76  // Constructs a HostCache that stores up to |max_entries|.
77  explicit HostCache(size_t max_entries);
78
79  ~HostCache();
80
81  // Returns a pointer to the entry for |key|, which is valid at time
82  // |now|. If there is no such entry, returns NULL.
83  const Entry* Lookup(const Key& key, base::TimeTicks now);
84
85  // Overwrites or creates an entry for |key|.
86  // |entry| is the value to set, |now| is the current time
87  // |ttl| is the "time to live".
88  void Set(const Key& key,
89           const Entry& entry,
90           base::TimeTicks now,
91           base::TimeDelta ttl);
92
93  // Empties the cache
94  void clear();
95
96  // Returns the number of entries in the cache.
97  size_t size() const;
98
99  // Following are used by net_internals UI.
100  size_t max_entries() const;
101
102  const EntryMap& entries() const;
103
104  // Creates a default cache.
105  static scoped_ptr<HostCache> CreateDefaultCache();
106
107 private:
108  FRIEND_TEST_ALL_PREFIXES(HostCacheTest, NoCache);
109
110  // Returns true if this HostCache can contain no entries.
111  bool caching_is_disabled() const {
112    return entries_.max_entries() == 0;
113  }
114
115  // Map from hostname (presumably in lowercase canonicalized format) to
116  // a resolved result entry.
117  EntryMap entries_;
118
119  DISALLOW_COPY_AND_ASSIGN(HostCache);
120};
121
122}  // namespace net
123
124#endif  // NET_DNS_HOST_CACHE_H_
125