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// This files was copied/modified from https://github.com/hashicorp/golang-lru
// which was (see below)
// 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 utils
import (
"container/list"
"errors"
"sync"
"time"
)
// 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{}
expireAtSecs int64
}
// New creates an LRU of the given size
func NewLru(size int) *Cache {
cache, _ := NewLruWithEvict(size, nil)
return cache
}
func NewLruWithEvict(size int, onEvicted func(key interface{}, value interface{})) (*Cache, error) {
if size <= 0 {
return nil, errors.New(T("utils.iru.with_evict"))
}
c := &Cache{
size: size,
evictList: list.New(),
items: make(map[interface{}]*list.Element, size),
onEvicted: onEvicted,
}
return c, nil
}
// Purge is used to completely clear the cache
func (c *Cache) Purge() {
c.lock.Lock()
defer c.lock.Unlock()
if c.onEvicted != nil {
for k, v := range c.items {
c.onEvicted(k, v.Value)
}
}
c.evictList = list.New()
c.items = make(map[interface{}]*list.Element, c.size)
}
func (c *Cache) Add(key, value interface{}) bool {
return c.AddWithExpiresInSecs(key, value, 0)
}
// Add adds a value to the cache. Returns true if an eviction occurred.
func (c *Cache) AddWithExpiresInSecs(key, value interface{}, expireAtSecs int64) bool {
c.lock.Lock()
defer c.lock.Unlock()
if expireAtSecs > 0 {
expireAtSecs = (time.Now().UnixNano() / int64(time.Second)) + expireAtSecs
}
// Check for existing item
if ent, ok := c.items[key]; ok {
c.evictList.MoveToFront(ent)
ent.Value.(*entry).value = value
ent.Value.(*entry).expireAtSecs = expireAtSecs
return false
}
// Add new item
ent := &entry{key, value, expireAtSecs}
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 {
if ent.Value.(*entry).expireAtSecs > 0 {
if (time.Now().UnixNano() / int64(time.Second)) > ent.Value.(*entry).expireAtSecs {
c.removeElement(ent)
return nil, false
}
}
c.evictList.MoveToFront(ent)
return ent.Value.(*entry).value, true
}
return
}
// 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)
}
}
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