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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | 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 | 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 // This file contains a template for a Most Recently Used cache that allows | 5 // This file contains a template for a Most Recently Used cache that allows |
6 // constant-time access to items using a key, but easy identification of the | 6 // constant-time access to items using a key, but easy identification of the |
7 // least-recently-used items for removal. Each key can only be associated with | 7 // least-recently-used items for removal. Each key can only be associated with |
8 // one payload item at a time. | 8 // one payload item at a time. |
9 // | 9 // |
10 // The key object will be stored twice, so it should support efficient copying. | 10 // The key object will be stored twice, so it should support efficient copying. |
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90 if (index_iter != index_.end()) { | 90 if (index_iter != index_.end()) { |
91 // Erase the reference to it. The index reference will be replaced in the | 91 // Erase the reference to it. The index reference will be replaced in the |
92 // code below. | 92 // code below. |
93 Erase(index_iter->second); | 93 Erase(index_iter->second); |
94 } else if (max_size_ != NO_AUTO_EVICT) { | 94 } else if (max_size_ != NO_AUTO_EVICT) { |
95 // New item is being inserted which might make it larger than the maximum | 95 // New item is being inserted which might make it larger than the maximum |
96 // size: kick the oldest thing out if necessary. | 96 // size: kick the oldest thing out if necessary. |
97 ShrinkToSize(max_size_ - 1); | 97 ShrinkToSize(max_size_ - 1); |
98 } | 98 } |
99 | 99 |
100 ordering_.push_front(value_type(key, std::forward<Payload>(payload))); | 100 ordering_.emplace_front(key, std::forward<Payload>(payload)); |
101 index_.insert(std::make_pair(key, ordering_.begin())); | 101 index_.emplace(key, ordering_.begin()); |
jdoerrie
2017/04/25 11:33:47
While |index_|'s type is a template parameter, it
| |
102 return ordering_.begin(); | 102 return ordering_.begin(); |
103 } | 103 } |
104 | 104 |
105 // Retrieves the contents of the given key, or end() if not found. This method | 105 // Retrieves the contents of the given key, or end() if not found. This method |
106 // has the side effect of moving the requested item to the front of the | 106 // has the side effect of moving the requested item to the front of the |
107 // recency list. | 107 // recency list. |
108 iterator Get(const KeyType& key) { | 108 iterator Get(const KeyType& key) { |
109 typename KeyIndex::iterator index_iter = index_.find(key); | 109 typename KeyIndex::iterator index_iter = index_.find(key); |
110 if (index_iter == index_.end()) | 110 if (index_iter == index_.end()) |
111 return end(); | 111 return end(); |
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247 : ParentType(max_size) {} | 247 : ParentType(max_size) {} |
248 virtual ~HashingMRUCache() {} | 248 virtual ~HashingMRUCache() {} |
249 | 249 |
250 private: | 250 private: |
251 DISALLOW_COPY_AND_ASSIGN(HashingMRUCache); | 251 DISALLOW_COPY_AND_ASSIGN(HashingMRUCache); |
252 }; | 252 }; |
253 | 253 |
254 } // namespace base | 254 } // namespace base |
255 | 255 |
256 #endif // BASE_CONTAINERS_MRU_CACHE_H_ | 256 #endif // BASE_CONTAINERS_MRU_CACHE_H_ |
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