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QUICHE teama6ef0a62019-03-07 20:34:33 -05001// Copyright (c) 2018 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 QUICHE_QUIC_CORE_QUIC_LRU_CACHE_H_
6#define QUICHE_QUIC_CORE_QUIC_LRU_CACHE_H_
7
8#include <memory>
9
10#include "net/third_party/quiche/src/quic/platform/api/quic_containers.h"
dschinazif25169a2019-10-23 08:12:18 -070011#include "net/third_party/quiche/src/quic/platform/api/quic_export.h"
QUICHE teama6ef0a62019-03-07 20:34:33 -050012#include "net/third_party/quiche/src/quic/platform/api/quic_flag_utils.h"
13#include "net/third_party/quiche/src/quic/platform/api/quic_flags.h"
14
15namespace quic {
16
17// A LRU cache that maps from type Key to Value* in QUIC.
18// This cache CANNOT be shared by multiple threads (even with locks) because
19// Value* returned by Lookup() can be invalid if the entry is evicted by other
20// threads.
21template <class K, class V>
dschinazie2116422019-10-29 11:54:26 -070022class QUIC_NO_EXPORT QuicLRUCache {
QUICHE teama6ef0a62019-03-07 20:34:33 -050023 public:
24 explicit QuicLRUCache(size_t capacity) : capacity_(capacity) {}
25 QuicLRUCache(const QuicLRUCache&) = delete;
26 QuicLRUCache& operator=(const QuicLRUCache&) = delete;
27
28 // Inserts one unit of |key|, |value| pair to the cache. Cache takes ownership
29 // of inserted |value|.
30 void Insert(const K& key, std::unique_ptr<V> value) {
31 auto it = cache_.find(key);
32 if (it != cache_.end()) {
33 cache_.erase(it);
34 }
35 cache_.emplace(key, std::move(value));
36
37 if (cache_.size() > capacity_) {
38 cache_.pop_front();
39 }
40 DCHECK_LE(cache_.size(), capacity_);
41 }
42
43 // If cache contains an entry for |key|, return a pointer to it. This returned
44 // value is guaranteed to be valid until Insert or Clear.
45 // Else return nullptr.
46 V* Lookup(const K& key) {
47 auto it = cache_.find(key);
48 if (it == cache_.end()) {
49 return nullptr;
50 }
51
52 std::unique_ptr<V> value = std::move(it->second);
53 cache_.erase(it);
54 auto result = cache_.emplace(key, std::move(value));
55 DCHECK(result.second);
56 return result.first->second.get();
57 }
58
59 // Removes all entries from the cache.
60 void Clear() { cache_.clear(); }
61
62 // Returns maximum size of the cache.
63 size_t MaxSize() const { return capacity_; }
64
65 // Returns current size of the cache.
66 size_t Size() const { return cache_.size(); }
67
68 private:
69 QuicLinkedHashMap<K, std::unique_ptr<V>> cache_;
70 const size_t capacity_;
71};
72
73} // namespace quic
74
75#endif // QUICHE_QUIC_CORE_QUIC_LRU_CACHE_H_