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// Copyright (c) 2012 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 NET_DNS_HOST_CACHE_H_
#define NET_DNS_HOST_CACHE_H_
#include <stddef.h>
#include <functional>
#include <string>
#include <tuple>
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/memory/scoped_ptr.h"
#include "base/threading/non_thread_safe.h"
#include "base/time/time.h"
#include "net/base/address_family.h"
#include "net/base/address_list.h"
#include "net/base/expiring_cache.h"
#include "net/base/net_export.h"
namespace net {
// Cache used by HostResolver to map hostnames to their resolved result.
class NET_EXPORT HostCache : NON_EXPORTED_BASE(public base::NonThreadSafe) {
public:
// Stores the latest address list that was looked up for a hostname.
struct NET_EXPORT Entry {
Entry(int error, const AddressList& addrlist, base::TimeDelta ttl);
// Use when |ttl| is unknown.
Entry(int error, const AddressList& addrlist);
~Entry();
bool has_ttl() const { return ttl >= base::TimeDelta(); }
// The resolve results for this entry.
int error;
AddressList addrlist;
// TTL obtained from the nameserver. Negative if unknown.
base::TimeDelta ttl;
};
struct Key {
Key(const std::string& hostname, AddressFamily address_family,
HostResolverFlags host_resolver_flags)
: hostname(hostname),
address_family(address_family),
host_resolver_flags(host_resolver_flags) {}
bool operator<(const Key& other) const {
// The order of comparisons of |Key| fields is arbitrary, thus
// |address_family| and |host_resolver_flags| are compared before
// |hostname| under assumption that integer comparisons are faster than
// string comparisons.
return std::tie(address_family, host_resolver_flags, hostname) <
std::tie(other.address_family, other.host_resolver_flags,
other.hostname);
}
std::string hostname;
AddressFamily address_family;
HostResolverFlags host_resolver_flags;
};
struct EvictionHandler {
void Handle(const Key& key,
const Entry& entry,
const base::TimeTicks& expiration,
const base::TimeTicks& now,
bool onGet) const;
};
typedef ExpiringCache<Key, Entry, base::TimeTicks,
std::less<base::TimeTicks>,
EvictionHandler> EntryMap;
// Constructs a HostCache that stores up to |max_entries|.
explicit HostCache(size_t max_entries);
~HostCache();
// Returns a pointer to the entry for |key|, which is valid at time
// |now|. If there is no such entry, returns NULL.
const Entry* Lookup(const Key& key, base::TimeTicks now);
// Overwrites or creates an entry for |key|.
// |entry| is the value to set, |now| is the current time
// |ttl| is the "time to live".
void Set(const Key& key,
const Entry& entry,
base::TimeTicks now,
base::TimeDelta ttl);
// Empties the cache
void clear();
// Returns the number of entries in the cache.
size_t size() const;
// Following are used by net_internals UI.
size_t max_entries() const;
const EntryMap& entries() const;
// Creates a default cache.
static scoped_ptr<HostCache> CreateDefaultCache();
private:
FRIEND_TEST_ALL_PREFIXES(HostCacheTest, NoCache);
// Returns true if this HostCache can contain no entries.
bool caching_is_disabled() const {
return entries_.max_entries() == 0;
}
// Map from hostname (presumably in lowercase canonicalized format) to
// a resolved result entry.
EntryMap entries_;
DISALLOW_COPY_AND_ASSIGN(HostCache);
};
} // namespace net
#endif // NET_DNS_HOST_CACHE_H_
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