/
lru.go
169 lines (140 loc) · 3.28 KB
/
lru.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
package utils
import (
"container/list"
"sync"
)
// LRU implements a simple and thread-safe LRU cache
type LRU struct {
lock *sync.RWMutex
elements map[interface{}]*list.Element
entries *list.List
async AsyncRunner
maxlen int
onDelete DeleteCallback
onCheck CheckCallback
}
type entry struct {
key interface{}
value interface{}
}
// CheckCallback is used to check if a key can be deleted
// the key won't be deleted if it returns true
type CheckCallback func(key, value interface{}) (ok bool)
// DeleteCallback is called when a key is deleting
type DeleteCallback func(key, value interface{})
// NewLRU init a new lru
func NewLRU(maxlen int, onCheck CheckCallback, onDelete DeleteCallback) *LRU {
lru := &LRU{
lock: &sync.RWMutex{},
elements: make(map[interface{}]*list.Element),
entries: list.New(),
maxlen: 0,
onDelete: onDelete,
onCheck: onCheck,
}
if maxlen > 0 {
lru.maxlen = maxlen
}
return lru
}
// Add inserts new key and value into the lru
func (lru *LRU) Add(key, value interface{}) {
lru.lock.Lock()
defer lru.lock.Unlock()
ele, ok := lru.elements[key]
if ok {
lru.entries.MoveToFront(ele)
ele.Value.(*entry).value = value
return
}
ent := &entry{key: key, value: value}
ele = lru.entries.PushFront(ent)
lru.elements[key] = ele
if lru.entries.Len() > lru.maxlen {
lru.tryDeleteOldest()
}
return
}
// Load get the value from lru cache with given key, ok returns false if
// key is not in the lru
func (lru *LRU) Load(key interface{}) (value interface{}, ok bool) {
lru.lock.RLock()
defer lru.lock.RUnlock()
ele, ok := lru.elements[key]
if ok {
value = ele.Value.(*entry).value
lru.async.Run(func() {
lru.lock.Lock()
defer lru.lock.Unlock()
lru.entries.MoveToFront(ele)
})
}
return
}
// Has test if the key is in the lru cache, and don't update the lru
func (lru *LRU) Has(key interface{}) (ok bool) {
lru.lock.RLock()
defer lru.lock.RUnlock()
_, ok = lru.elements[key]
return
}
// Delete deletes the key from cache, returns its value and if cache has the key
func (lru *LRU) Delete(key interface{}) (value interface{}, ok bool) {
lru.lock.Lock()
defer lru.lock.Unlock()
ele, ok := lru.elements[key]
if ok {
value = ele.Value.(*entry).value
lru.deleteElement(ele)
}
return
}
// DeleteOldest deletes the oldest entry from cache
// returns its key, value and if delete is successful
func (lru *LRU) DeleteOldest() (key, value interface{}, ok bool) {
lru.lock.Lock()
defer lru.lock.Unlock()
ele := lru.entries.Back()
if ele == nil {
return
}
ent := ele.Value.(*entry)
key = ent.key
value = ent.value
lru.deleteElement(ele)
return
}
// Length returns the number of entries
func (lru *LRU) Length() int {
lru.lock.RLock()
defer lru.lock.RUnlock()
return lru.entries.Len()
}
func (lru *LRU) tryDeleteOldest() {
ele := lru.entries.Back()
if ele == nil {
return
}
if lru.onCheck != nil {
ent := ele.Value.(*entry)
ok := lru.onCheck(ent.key, ent.value)
if ok {
lru.entries.MoveToFront(ele)
return
}
}
lru.deleteElement(ele)
}
func (lru *LRU) deleteElement(ele *list.Element) {
if ele == nil {
return
}
lru.entries.Remove(ele)
ent := ele.Value.(*entry)
delete(lru.elements, ent.key)
if lru.onDelete != nil {
lru.async.Run(func() {
lru.onDelete(ent.key, ent.value)
})
}
}