/usr/share/gocode/src/github.com/hashicorp/golang-lru/lru.go is in golang-github-hashicorp-golang-lru-dev 0.0~git20151028.0.a6091bb-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 | // This package provides a simple LRU cache. It is based on the
// LRU implementation in groupcache:
// https://github.com/golang/groupcache/tree/master/lru
package lru
import (
"container/list"
"errors"
"sync"
)
// Cache is a thread-safe fixed size LRU cache.
type Cache struct {
size int
evictList *list.List
items map[interface{}]*list.Element
lock sync.RWMutex
onEvicted func(key interface{}, value interface{})
}
// entry is used to hold a value in the evictList
type entry struct {
key interface{}
value interface{}
}
// New creates an LRU of the given size
func New(size int) (*Cache, error) {
return NewWithEvict(size, nil)
}
func NewWithEvict(size int, onEvicted func(key interface{}, value interface{})) (*Cache, error) {
if size <= 0 {
return nil, errors.New("Must provide a positive size")
}
c := &Cache{
size: size,
evictList: list.New(),
items: make(map[interface{}]*list.Element),
onEvicted: onEvicted,
}
return c, nil
}
// Purge is used to completely clear the cache
func (c *Cache) Purge() {
c.lock.Lock()
defer c.lock.Unlock()
for k, v := range c.items {
if c.onEvicted != nil {
c.onEvicted(k, v.Value.(*entry).value)
}
delete(c.items, k)
}
c.evictList.Init()
}
// Add adds a value to the cache. Returns true if an eviction occured.
func (c *Cache) Add(key, value interface{}) bool {
c.lock.Lock()
defer c.lock.Unlock()
// Check for existing item
if ent, ok := c.items[key]; ok {
c.evictList.MoveToFront(ent)
ent.Value.(*entry).value = value
return false
}
// Add new item
ent := &entry{key, value}
entry := c.evictList.PushFront(ent)
c.items[key] = entry
evict := c.evictList.Len() > c.size
// Verify size not exceeded
if evict {
c.removeOldest()
}
return evict
}
// Get looks up a key's value from the cache.
func (c *Cache) Get(key interface{}) (value interface{}, ok bool) {
c.lock.Lock()
defer c.lock.Unlock()
if ent, ok := c.items[key]; ok {
c.evictList.MoveToFront(ent)
return ent.Value.(*entry).value, true
}
return
}
// Check if a key is in the cache, without updating the recent-ness or deleting it for being stale.
func (c *Cache) Contains(key interface{}) (ok bool) {
c.lock.RLock()
defer c.lock.RUnlock()
_, ok = c.items[key]
return ok
}
// Returns the key value (or undefined if not found) without updating the "recently used"-ness of the key.
// (If you find yourself using this a lot, you might be using the wrong sort of data structure, but there are some use cases where it's handy.)
func (c *Cache) Peek(key interface{}) (value interface{}, ok bool) {
c.lock.RLock()
defer c.lock.RUnlock()
if ent, ok := c.items[key]; ok {
return ent.Value.(*entry).value, true
}
return nil, ok
}
// ContainsOrAdd checks if a key is in the cache (without updating the recent-ness or deleting it for being stale),
// if not, adds the value. Returns whether found and whether an eviction occurred.
func (c *Cache) ContainsOrAdd(key, value interface{}) (ok, evict bool) {
c.lock.Lock()
defer c.lock.Unlock()
_, ok = c.items[key]
if ok {
return true, false
}
ent := &entry{key, value}
entry := c.evictList.PushFront(ent)
c.items[key] = entry
evict = c.evictList.Len() > c.size
// Verify size not exceeded
if evict {
c.removeOldest()
}
return false, evict
}
// Remove removes the provided key from the cache.
func (c *Cache) Remove(key interface{}) {
c.lock.Lock()
defer c.lock.Unlock()
if ent, ok := c.items[key]; ok {
c.removeElement(ent)
}
}
// RemoveOldest removes the oldest item from the cache.
func (c *Cache) RemoveOldest() {
c.lock.Lock()
defer c.lock.Unlock()
c.removeOldest()
}
// Keys returns a slice of the keys in the cache, from oldest to newest.
func (c *Cache) Keys() []interface{} {
c.lock.RLock()
defer c.lock.RUnlock()
keys := make([]interface{}, len(c.items))
ent := c.evictList.Back()
i := 0
for ent != nil {
keys[i] = ent.Value.(*entry).key
ent = ent.Prev()
i++
}
return keys
}
// Len returns the number of items in the cache.
func (c *Cache) Len() int {
c.lock.RLock()
defer c.lock.RUnlock()
return c.evictList.Len()
}
// removeOldest removes the oldest item from the cache.
func (c *Cache) removeOldest() {
ent := c.evictList.Back()
if ent != nil {
c.removeElement(ent)
}
}
// removeElement is used to remove a given list element from the cache
func (c *Cache) removeElement(e *list.Element) {
c.evictList.Remove(e)
kv := e.Value.(*entry)
delete(c.items, kv.key)
if c.onEvicted != nil {
c.onEvicted(kv.key, kv.value)
}
}
|