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cache.go
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cache.go
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// This package provide a simple memory k/v cache and LRU cache.
// It based on the k/v cache implementation in go-cache:
// https://github.com/pmylund/go-cache
// and LRU cache implementation in groupcache:
// https://github.com/golang/groupcache/tree/master/lru
package cache
import (
"container/list"
"errors"
"fmt"
"sync"
"time"
)
// Cache is a goroutine-safe K/V cache.
type Cache struct {
sync.RWMutex
items map[interface{}]*Item
defaultExpiration time.Duration
}
type Item struct {
Object interface{}
Expiration *time.Time
}
// Returns true if the item has expired.
func (item *Item) Expired() bool {
if item.Expiration == nil {
return false
}
return item.Expiration.Before(time.Now())
}
// New create a new cache with a given default expiration duration and cleanup
// interval. If the expiration duration is less than 1, the items in the cache
// never expire (by default), and must be deleted manually. If the cleanup
// interval is less than one, expired items are not deleted from the cache
// before calling DeleteExpired.
func New(defaultExpiration, cleanInterval time.Duration) *Cache {
c := &Cache{
items: map[interface{}]*Item{},
defaultExpiration: defaultExpiration,
}
if cleanInterval > 0 {
go func() {
for {
time.Sleep(cleanInterval)
c.DeleteExpired()
}
}()
}
return c
}
// Get return an item or nil, and a bool indicating whether
// the key was found.
func (c *Cache) Get(key interface{}) (interface{}, bool) {
c.RLock()
item, ok := c.items[key]
if !ok || item.Expired() {
c.RUnlock()
return nil, false
}
c.RUnlock()
return item.Object, true
}
// Set add a new key or replace an exist key. If the dur is 0, we will
// use the defaultExpiration.
func (c *Cache) Set(key interface{}, val interface{}, dur time.Duration) {
var t *time.Time
c.Lock()
if dur == 0 {
dur = c.defaultExpiration
}
if dur > 0 {
tmp := time.Now().Add(dur)
t = &tmp
}
c.items[key] = &Item{
Object: val,
Expiration: t,
}
c.Unlock()
}
// Delete a key-value pair if the key is existed.
func (c *Cache) Delete(key interface{}) {
c.Lock()
delete(c.items, key)
c.Unlock()
}
// Delete all cache.
func (c *Cache) Flush() {
c.Lock()
c.items = map[interface{}]*Item{}
c.Unlock()
}
// Add a number to a key-value pair.
func (c *Cache) Increment(key interface{}, x int64) error {
c.Lock()
val, ok := c.items[key]
if !ok || val.Expired() {
c.Unlock()
return fmt.Errorf("Item %s not found", key)
}
switch val.Object.(type) {
case int:
val.Object = val.Object.(int) + int(x)
case int8:
val.Object = val.Object.(int8) + int8(x)
case int16:
val.Object = val.Object.(int16) + int16(x)
case int32:
val.Object = val.Object.(int32) + int32(x)
case int64:
val.Object = val.Object.(int64) + x
case uint:
val.Object = val.Object.(uint) + uint(x)
case uint8:
val.Object = val.Object.(uint8) + uint8(x)
case uint16:
val.Object = val.Object.(uint16) + uint16(x)
case uint32:
val.Object = val.Object.(uint32) + uint32(x)
case uint64:
val.Object = val.Object.(uint64) + uint64(x)
case uintptr:
val.Object = val.Object.(uintptr) + uintptr(x)
default:
c.Unlock()
return fmt.Errorf("The value type error")
}
c.Unlock()
return nil
}
// Sub a number to a key-value pair.
func (c *Cache) Decrement(key interface{}, x int64) error {
c.Lock()
val, ok := c.items[key]
if !ok || val.Expired() {
c.Unlock()
return fmt.Errorf("Item %s not found", key)
}
switch val.Object.(type) {
case int:
val.Object = val.Object.(int) - int(x)
case int8:
val.Object = val.Object.(int8) - int8(x)
case int16:
val.Object = val.Object.(int16) - int16(x)
case int32:
val.Object = val.Object.(int32) - int32(x)
case int64:
val.Object = val.Object.(int64) - x
case uint:
val.Object = val.Object.(uint) - uint(x)
case uint8:
val.Object = val.Object.(uint8) - uint8(x)
case uint16:
val.Object = val.Object.(uint16) - uint16(x)
case uint32:
val.Object = val.Object.(uint32) - uint32(x)
case uint64:
val.Object = val.Object.(uint64) - uint64(x)
case uintptr:
val.Object = val.Object.(uintptr) - uintptr(x)
default:
c.Unlock()
return fmt.Errorf("The value type error")
}
c.Unlock()
return nil
}
// Return the number of item in cache.
func (c *Cache) ItemCount() int {
c.RLock()
counts := len(c.items)
c.RUnlock()
return counts
}
// Delete all expired items.
func (c *Cache) DeleteExpired() {
c.Lock()
for k, v := range c.items {
if v.Expired() {
delete(c.items, k)
}
}
c.Unlock()
}
// The LRUCache is a goroutine-safe cache.
type LRUCache struct {
sync.RWMutex
maxEntries int
items map[interface{}]*list.Element
cacheList *list.List
}
type entry struct {
key interface{}
value interface{}
}
// NewLRU create a LRUCache with max size. The size is 0 means no limit.
func NewLRU(size int) (*LRUCache, error) {
if size < 0 {
return nil, errors.New("The size of LRU Cache must no less than 0")
}
lru := &LRUCache{
maxEntries: size,
items: make(map[interface{}]*list.Element, size),
cacheList: list.New(),
}
return lru, nil
}
// Add a new key-value pair to the LRUCache.
func (c *LRUCache) Add(key interface{}, value interface{}) {
c.Lock()
defer c.Unlock()
if ent, hit := c.items[key]; hit {
c.cacheList.MoveToFront(ent)
ent.Value.(*entry).value = value
return
}
ent := &entry{
key: key,
value: value,
}
entry := c.cacheList.PushFront(ent)
c.items[key] = entry
if c.maxEntries > 0 && c.cacheList.Len() > c.maxEntries {
c.removeOldestElement()
}
}
// Get a value from the LRUCache. And a bool indicating
// whether found or not.
func (c *LRUCache) Get(key interface{}) (interface{}, bool) {
c.RLock()
defer c.RUnlock()
if ent, hit := c.items[key]; hit {
c.cacheList.MoveToFront(ent)
return ent.Value.(*entry).value, true
}
return nil, false
}
// Remove a key-value pair in LRUCache. If the key is not existed,
// nothing will happen.
func (c *LRUCache) Remove(key interface{}) {
c.Lock()
defer c.Unlock()
if ent, hit := c.items[key]; hit {
c.removeElement(ent)
}
}
// Return the number of key-value pair in LRUCache.
func (c *LRUCache) Len() int {
c.RLock()
length := c.cacheList.Len()
c.RUnlock()
return length
}
// Delete all entry in the LRUCache. But the max size will hold.
func (c *LRUCache) Clear() {
c.Lock()
c.cacheList = list.New()
c.items = make(map[interface{}]*list.Element, c.maxEntries)
c.Unlock()
}
// Resize the max limit.
func (c *LRUCache) SetMaxEntries(max int) error {
if max < 0 {
return errors.New("The max limit of entryies must no less than 0")
}
c.Lock()
c.maxEntries = max
c.Unlock()
return nil
}
func (c *LRUCache) removeElement(e *list.Element) {
c.cacheList.Remove(e)
ent := e.Value.(*entry)
delete(c.items, ent.key)
}
func (c *LRUCache) removeOldestElement() {
ent := c.cacheList.Back()
if ent != nil {
c.removeElement(ent)
}
}