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Side by Side Diff: components/copresence/timed_map.h

Issue 2130803002: Deleting the copresence API. (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: . Created 4 years, 5 months ago
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1 // Copyright 2014 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 COMPONENTS_COPRESENCE_TIMED_MAP_H_
6 #define COMPONENTS_COPRESENCE_TIMED_MAP_H_
7
8 #include <stddef.h>
9
10 #include <map>
11 #include <memory>
12 #include <queue>
13 #include <utility>
14 #include <vector>
15
16 #include "base/macros.h"
17 #include "base/time/default_tick_clock.h"
18 #include "base/time/tick_clock.h"
19 #include "base/time/time.h"
20 #include "base/timer/timer.h"
21
22 namespace copresence {
23
24 // TimedMap is a map with the added functionality of clearing any
25 // key/value pair after its specified lifetime is over.
26 // TODO(ckehoe): Why is this interface so different from std::map?
27 template <typename KeyType, typename ValueType>
28 class TimedMap {
29 public:
30 TimedMap(const base::TimeDelta& lifetime, size_t max_elements)
31 : kEmptyValue(ValueType()),
32 clock_(new base::DefaultTickClock()),
33 lifetime_(lifetime),
34 max_elements_(max_elements) {
35 timer_.Start(FROM_HERE, lifetime_, this, &TimedMap::ClearExpiredTokens);
36 }
37
38 ~TimedMap() {}
39
40 void Add(const KeyType& key, const ValueType& value) {
41 map_[key] = value;
42 expiry_queue_.push(KeyTimeTuple(key, clock_->NowTicks() + lifetime_));
43 while (map_.size() > max_elements_)
44 ClearOldestToken();
45 }
46
47 bool HasKey(const KeyType& key) {
48 ClearExpiredTokens();
49 return map_.find(key) != map_.end();
50 }
51
52 const ValueType& GetValue(const KeyType& key) {
53 ClearExpiredTokens();
54 auto elt = map_.find(key);
55 return elt == map_.end() ? kEmptyValue : elt->second;
56 }
57
58 ValueType* GetMutableValue(const KeyType& key) {
59 ClearExpiredTokens();
60 auto elt = map_.find(key);
61 return elt == map_.end() ? nullptr : &(elt->second);
62 }
63
64 // TODO(ckehoe): Add a unit test for this.
65 size_t Erase(const KeyType& key) {
66 return map_.erase(key);
67 }
68
69 void set_clock_for_testing(std::unique_ptr<base::TickClock> clock) {
70 clock_ = std::move(clock);
71 }
72
73 private:
74 void ClearExpiredTokens() {
75 while (!expiry_queue_.empty() &&
76 expiry_queue_.top().second <= clock_->NowTicks())
77 ClearOldestToken();
78 }
79
80 void ClearOldestToken() {
81 map_.erase(expiry_queue_.top().first);
82 expiry_queue_.pop();
83 }
84
85 using KeyTimeTuple = std::pair<KeyType, base::TimeTicks>;
86
87 class EarliestFirstComparator {
88 public:
89 // This will sort our queue with the 'earliest' time being the top.
90 bool operator()(const KeyTimeTuple& left, const KeyTimeTuple& right) const {
91 return left.second > right.second;
92 }
93 };
94
95 using ExpiryQueue = std::priority_queue<
96 KeyTimeTuple, std::vector<KeyTimeTuple>, EarliestFirstComparator>;
97
98 const ValueType kEmptyValue;
99
100 std::unique_ptr<base::TickClock> clock_;
101 base::RepeatingTimer timer_;
102 const base::TimeDelta lifetime_;
103 const size_t max_elements_;
104 std::map<KeyType, ValueType> map_;
105 // Priority queue with our element keys ordered by the earliest expiring keys
106 // first.
107 ExpiryQueue expiry_queue_;
108
109 DISALLOW_COPY_AND_ASSIGN(TimedMap);
110 };
111
112 } // namespace copresence
113
114 #endif // COMPONENTS_COPRESENCE_TIMED_MAP_H_
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