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| 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 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 | 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
| 4 | 4 |
| 5 #ifndef NET_BASE_EXPIRING_CACHE_H_ | 5 #ifndef NET_BASE_EXPIRING_CACHE_H_ |
| 6 #define NET_BASE_EXPIRING_CACHE_H_ | 6 #define NET_BASE_EXPIRING_CACHE_H_ |
| 7 | 7 |
| 8 #include <map> | 8 #include <map> |
| 9 #include <utility> | 9 #include <utility> |
| 10 | 10 |
| 11 #include "base/basictypes.h" | 11 #include "base/basictypes.h" |
| 12 #include "base/gtest_prod_util.h" | 12 #include "base/gtest_prod_util.h" |
| 13 #include "base/time/time.h" | 13 #include "base/time/time.h" |
| 14 | 14 |
| 15 namespace net { | 15 namespace net { |
| 16 | 16 |
| 17 template <typename KeyType, | 17 template <typename KeyType, typename ValueType, typename ExpirationType> |
| 18 typename ValueType, | |
| 19 typename ExpirationType> | |
| 20 class NoopEvictionHandler { | 18 class NoopEvictionHandler { |
| 21 public: | 19 public: |
| 22 void Handle(const KeyType& key, | 20 void Handle(const KeyType& key, |
| 23 const ValueType& value, | 21 const ValueType& value, |
| 24 const ExpirationType& expiration, | 22 const ExpirationType& expiration, |
| 25 const ExpirationType& now, | 23 const ExpirationType& now, |
| 26 bool onGet) const { | 24 bool onGet) const {} |
| 27 } | |
| 28 }; | 25 }; |
| 29 | 26 |
| 30 // Cache implementation where all entries have an explicit expiration policy. As | 27 // Cache implementation where all entries have an explicit expiration policy. As |
| 31 // new items are added, expired items will be removed first. | 28 // new items are added, expired items will be removed first. |
| 32 // The template types have the following requirements: | 29 // The template types have the following requirements: |
| 33 // KeyType must be LessThanComparable, Assignable, and CopyConstructible. | 30 // KeyType must be LessThanComparable, Assignable, and CopyConstructible. |
| 34 // ValueType must be CopyConstructible and Assignable. | 31 // ValueType must be CopyConstructible and Assignable. |
| 35 // ExpirationType must be CopyConstructible and Assignable. | 32 // ExpirationType must be CopyConstructible and Assignable. |
| 36 // ExpirationCompare is a function class that takes two arguments of the | 33 // ExpirationCompare is a function class that takes two arguments of the |
| 37 // type ExpirationType and returns a bool. If |comp| is an instance of | 34 // type ExpirationType and returns a bool. If |comp| is an instance of |
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| 61 // }; | 58 // }; |
| 62 // ExpiringCache<std::string, std::string, ComplexExpiration, | 59 // ExpiringCache<std::string, std::string, ComplexExpiration, |
| 63 // ComplexExpirationFunctor> cache(15); | 60 // ComplexExpirationFunctor> cache(15); |
| 64 // // Add a value that expires once the 'sprocket' has 'cog'-ified. | 61 // // Add a value that expires once the 'sprocket' has 'cog'-ified. |
| 65 // cache.Put("key1", "value1", ComplexExpiration("sprocket"), | 62 // cache.Put("key1", "value1", ComplexExpiration("sprocket"), |
| 66 // ComplexExpiration("cog")); | 63 // ComplexExpiration("cog")); |
| 67 template <typename KeyType, | 64 template <typename KeyType, |
| 68 typename ValueType, | 65 typename ValueType, |
| 69 typename ExpirationType, | 66 typename ExpirationType, |
| 70 typename ExpirationCompare, | 67 typename ExpirationCompare, |
| 71 typename EvictionHandler = NoopEvictionHandler<KeyType, | 68 typename EvictionHandler = |
| 72 ValueType, | 69 NoopEvictionHandler<KeyType, ValueType, ExpirationType> > |
| 73 ExpirationType> > | |
| 74 class ExpiringCache { | 70 class ExpiringCache { |
| 75 private: | 71 private: |
| 76 // Intentionally violate the C++ Style Guide so that EntryMap is known to be | 72 // Intentionally violate the C++ Style Guide so that EntryMap is known to be |
| 77 // a dependent type. Without this, Clang's two-phase lookup complains when | 73 // a dependent type. Without this, Clang's two-phase lookup complains when |
| 78 // using EntryMap::const_iterator, while GCC and MSVC happily resolve the | 74 // using EntryMap::const_iterator, while GCC and MSVC happily resolve the |
| 79 // typename. | 75 // typename. |
| 80 | 76 |
| 81 // Tuple to represent the value and when it expires. | 77 // Tuple to represent the value and when it expires. |
| 82 typedef std::pair<ValueType, ExpirationType> Entry; | 78 typedef std::pair<ValueType, ExpirationType> Entry; |
| 83 typedef std::map<KeyType, Entry> EntryMap; | 79 typedef std::map<KeyType, Entry> EntryMap; |
| 84 | 80 |
| 85 public: | 81 public: |
| 86 typedef KeyType key_type; | 82 typedef KeyType key_type; |
| 87 typedef ValueType value_type; | 83 typedef ValueType value_type; |
| 88 typedef ExpirationType expiration_type; | 84 typedef ExpirationType expiration_type; |
| 89 | 85 |
| 90 // This class provides a read-only iterator over items in the ExpiringCache | 86 // This class provides a read-only iterator over items in the ExpiringCache |
| 91 class Iterator { | 87 class Iterator { |
| 92 public: | 88 public: |
| 93 explicit Iterator(const ExpiringCache& cache) | 89 explicit Iterator(const ExpiringCache& cache) |
| 94 : cache_(cache), | 90 : cache_(cache), it_(cache_.entries_.begin()) {} |
| 95 it_(cache_.entries_.begin()) { | |
| 96 } | |
| 97 ~Iterator() {} | 91 ~Iterator() {} |
| 98 | 92 |
| 99 bool HasNext() const { return it_ != cache_.entries_.end(); } | 93 bool HasNext() const { return it_ != cache_.entries_.end(); } |
| 100 void Advance() { ++it_; } | 94 void Advance() { ++it_; } |
| 101 | 95 |
| 102 const KeyType& key() const { return it_->first; } | 96 const KeyType& key() const { return it_->first; } |
| 103 const ValueType& value() const { return it_->second.first; } | 97 const ValueType& value() const { return it_->second.first; } |
| 104 const ExpirationType& expiration() const { return it_->second.second; } | 98 const ExpirationType& expiration() const { return it_->second.second; } |
| 105 | 99 |
| 106 private: | 100 private: |
| 107 const ExpiringCache& cache_; | 101 const ExpiringCache& cache_; |
| 108 | 102 |
| 109 // Use a second layer of type indirection, as both EntryMap and | 103 // Use a second layer of type indirection, as both EntryMap and |
| 110 // EntryMap::const_iterator are dependent types. | 104 // EntryMap::const_iterator are dependent types. |
| 111 typedef typename ExpiringCache::EntryMap EntryMap; | 105 typedef typename ExpiringCache::EntryMap EntryMap; |
| 112 typename EntryMap::const_iterator it_; | 106 typename EntryMap::const_iterator it_; |
| 113 }; | 107 }; |
| 114 | 108 |
| 115 | |
| 116 // Constructs an ExpiringCache that stores up to |max_entries|. | 109 // Constructs an ExpiringCache that stores up to |max_entries|. |
| 117 explicit ExpiringCache(size_t max_entries) : max_entries_(max_entries) {} | 110 explicit ExpiringCache(size_t max_entries) : max_entries_(max_entries) {} |
| 118 ~ExpiringCache() {} | 111 ~ExpiringCache() {} |
| 119 | 112 |
| 120 // Returns the value matching |key|, which must be valid at the time |now|. | 113 // Returns the value matching |key|, which must be valid at the time |now|. |
| 121 // Returns NULL if the item is not found or has expired. If the item has | 114 // Returns NULL if the item is not found or has expired. If the item has |
| 122 // expired, it is immediately removed from the cache. | 115 // expired, it is immediately removed from the cache. |
| 123 // Note: The returned pointer remains owned by the ExpiringCache and is | 116 // Note: The returned pointer remains owned by the ExpiringCache and is |
| 124 // invalidated by a call to a non-const method. | 117 // invalidated by a call to a non-const method. |
| 125 const ValueType* Get(const KeyType& key, const ExpirationType& now) { | 118 const ValueType* Get(const KeyType& key, const ExpirationType& now) { |
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| 137 } | 130 } |
| 138 | 131 |
| 139 // Updates or replaces the value associated with |key|. | 132 // Updates or replaces the value associated with |key|. |
| 140 void Put(const KeyType& key, | 133 void Put(const KeyType& key, |
| 141 const ValueType& value, | 134 const ValueType& value, |
| 142 const ExpirationType& now, | 135 const ExpirationType& now, |
| 143 const ExpirationType& expiration) { | 136 const ExpirationType& expiration) { |
| 144 typename EntryMap::iterator it = entries_.find(key); | 137 typename EntryMap::iterator it = entries_.find(key); |
| 145 if (it == entries_.end()) { | 138 if (it == entries_.end()) { |
| 146 // Compact the cache if it grew beyond the limit. | 139 // Compact the cache if it grew beyond the limit. |
| 147 if (entries_.size() == max_entries_ ) | 140 if (entries_.size() == max_entries_) |
| 148 Compact(now); | 141 Compact(now); |
| 149 | 142 |
| 150 // No existing entry. Creating a new one. | 143 // No existing entry. Creating a new one. |
| 151 entries_.insert(std::make_pair(key, Entry(value, expiration))); | 144 entries_.insert(std::make_pair(key, Entry(value, expiration))); |
| 152 } else { | 145 } else { |
| 153 // Update an existing cache entry. | 146 // Update an existing cache entry. |
| 154 it->second.first = value; | 147 it->second.first = value; |
| 155 it->second.second = expiration; | 148 it->second.second = expiration; |
| 156 } | 149 } |
| 157 } | 150 } |
| 158 | 151 |
| 159 // Empties the cache. | 152 // Empties the cache. |
| 160 void Clear() { | 153 void Clear() { entries_.clear(); } |
| 161 entries_.clear(); | |
| 162 } | |
| 163 | 154 |
| 164 // Returns the number of entries in the cache. | 155 // Returns the number of entries in the cache. |
| 165 size_t size() const { return entries_.size(); } | 156 size_t size() const { return entries_.size(); } |
| 166 | 157 |
| 167 // Returns the maximum number of entries in the cache. | 158 // Returns the maximum number of entries in the cache. |
| 168 size_t max_entries() const { return max_entries_; } | 159 size_t max_entries() const { return max_entries_; } |
| 169 | 160 |
| 170 bool empty() const { return entries_.empty(); } | 161 bool empty() const { return entries_.empty(); } |
| 171 | 162 |
| 172 private: | 163 private: |
| 173 FRIEND_TEST_ALL_PREFIXES(ExpiringCacheTest, Compact); | 164 FRIEND_TEST_ALL_PREFIXES(ExpiringCacheTest, Compact); |
| 174 FRIEND_TEST_ALL_PREFIXES(ExpiringCacheTest, CustomFunctor); | 165 FRIEND_TEST_ALL_PREFIXES(ExpiringCacheTest, CustomFunctor); |
| 175 | 166 |
| 176 // Prunes entries from the cache to bring it below |max_entries()|. | 167 // Prunes entries from the cache to bring it below |max_entries()|. |
| 177 void Compact(const ExpirationType& now) { | 168 void Compact(const ExpirationType& now) { |
| 178 // Clear out expired entries. | 169 // Clear out expired entries. |
| 179 typename EntryMap::iterator it; | 170 typename EntryMap::iterator it; |
| 180 for (it = entries_.begin(); it != entries_.end(); ) { | 171 for (it = entries_.begin(); it != entries_.end();) { |
| 181 if (!expiration_comp_(now, it->second.second)) { | 172 if (!expiration_comp_(now, it->second.second)) { |
| 182 Evict(it++, now, false); | 173 Evict(it++, now, false); |
| 183 } else { | 174 } else { |
| 184 ++it; | 175 ++it; |
| 185 } | 176 } |
| 186 } | 177 } |
| 187 | 178 |
| 188 if (entries_.size() < max_entries_) | 179 if (entries_.size() < max_entries_) |
| 189 return; | 180 return; |
| 190 | 181 |
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| 209 EntryMap entries_; | 200 EntryMap entries_; |
| 210 ExpirationCompare expiration_comp_; | 201 ExpirationCompare expiration_comp_; |
| 211 EvictionHandler eviction_handler_; | 202 EvictionHandler eviction_handler_; |
| 212 | 203 |
| 213 DISALLOW_COPY_AND_ASSIGN(ExpiringCache); | 204 DISALLOW_COPY_AND_ASSIGN(ExpiringCache); |
| 214 }; | 205 }; |
| 215 | 206 |
| 216 } // namespace net | 207 } // namespace net |
| 217 | 208 |
| 218 #endif // NET_BASE_EXPIRING_CACHE_H_ | 209 #endif // NET_BASE_EXPIRING_CACHE_H_ |
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