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// Copyright (c) 2009 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_BASE_HOST_CACHE_H_
#define NET_BASE_HOST_CACHE_H_
#include <string>
#include "base/hash_tables.h"
#include "base/ref_counted.h"
#include "base/time.h"
#include "net/base/address_list.h"
#include "testing/gtest/include/gtest/gtest_prod.h"
namespace net {
// Cache used by HostResolver to map hostnames to their resolved result.
class HostCache {
public:
// Stores the latest address list that was looked up for a hostname.
struct Entry : public base::RefCounted<Entry> {
Entry(int error, const AddressList& addrlist, base::TimeTicks expiration);
~Entry();
// The resolve results for this entry.
int error;
AddressList addrlist;
// The time when this entry expires.
base::TimeTicks expiration;
};
typedef base::hash_map<std::string, scoped_refptr<Entry> > EntryMap;
// Constructs a HostCache whose entries are valid for |cache_duration_ms|
// milliseconds. The cache will store up to |max_entries|.
HostCache(size_t max_entries, size_t cache_duration_ms);
~HostCache();
// Returns a pointer to the entry for |hostname|, which is valid at time
// |now|. If there is no such entry, returns NULL.
const Entry* Lookup(const std::string& hostname, base::TimeTicks now) const;
// Overwrites or creates an entry for |hostname|. Returns the pointer to the
// entry, or NULL on failure (fails if caching is disabled).
// (|error|, |addrlist|) is the value to set, and |now| is the current
// timestamp.
Entry* Set(const std::string& hostname,
int error,
const AddressList addrlist,
base::TimeTicks now);
// Returns true if this HostCache can contain no entries.
bool caching_is_disabled() const {
return max_entries_ == 0;
}
// Returns the number of entries in the cache.
size_t size() const {
return entries_.size();
}
size_t max_entries() const {
return max_entries_;
}
size_t cache_duration_ms() const {
return cache_duration_ms_;
}
// Note that this map may contain expired entries.
const EntryMap& entries() const {
return entries_;
}
private:
FRIEND_TEST(HostCacheTest, Compact);
FRIEND_TEST(HostCacheTest, NoCache);
// Returns true if this cache entry's result is valid at time |now|.
static bool CanUseEntry(const Entry* entry, const base::TimeTicks now);
// Prunes entries from the cache to bring it below max entry bound. Entries
// matching |pinned_entry| will NOT be pruned.
void Compact(base::TimeTicks now, const Entry* pinned_entry);
// Bound on total size of the cache.
size_t max_entries_;
// Time to live for cache entries in milliseconds.
size_t cache_duration_ms_;
// Map from hostname (presumably in lowercase canonicalized format) to
// a resolved result entry.
EntryMap entries_;
DISALLOW_COPY_AND_ASSIGN(HostCache);
};
} // namespace net
#endif // NET_BASE_HOST_CACHE_H_
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