golang LRU Cache

快来打我* 2022-04-01 02:09 130阅读 0赞

github地址：[https://github.com/hackssssss/lruCache][https_github.com_hackssssss_lruCache]

用golang中的map与list双向链表实现了lru（最久未使用）算法，map value中存放数据以及key在list中的地址，list中存放map的key，当set或者get时，从map中获取key在list中的地址，将其删除（list是双向链表，删除复杂度O1），并在list尾部添加新的key并更新map（复杂度也是O1）。这样list中第一个就是最久未使用的key，list末尾就是最近使用的key，list中就是按照使用时间排序的key。

package lru_cache
    
    import (
    	"container/list"
    	"fmt"
    	"sync"
    )
    
    type value struct {
    	data   []byte
    	lruPos *list.Element
    }
    
    type lruCache struct {
    	maxSize int
    	data    map[interface{}]*value
    	lck     *sync.Mutex
    	lru     *list.List
    }
    
    func NewLruCache(maxLength int) *lruCache {
    	if maxLength <= 0 {
    		return nil
    	}
    	return &lruCache{
    		maxSize: maxLength,
    		data:    make(map[interface{}]*value),
    		lck:     new(sync.Mutex),
    		lru:     list.New(),
    	}
    }
    
    func (c *lruCache) Set(key interface{}, data []byte) {
    	c.lck.Lock()
    	defer c.lck.Unlock()
    	if val, found := c.data[key]; found {
    		c.deleteLruItem(val.lruPos)       //删除原先在list中的位置
    		val.lruPos = c.updateNewItem(key) // 追加到list末尾，更新位置标示
    		c.data[key] = val
    	} else {
    		var pos *list.Element
    		if len(c.data) < c.maxSize {
    			pos = c.updateNewItem(key) //直接追加到list末尾
    		} else {
    			c.deleteLruItem(c.lru.Front()) //删除最久未使用的
    			pos = c.updateNewItem(key)     //将本次key更新到list的末尾
    		}
    		val := &value{
    			data:   data,
    			lruPos: pos,
    		}
    		c.data[key] = val
    	}
    }
    
    func (c *lruCache) Get(key interface{}) (exist bool, data []byte) {
    	c.lck.Lock()
    	defer c.lck.Unlock()
    	if val, found := c.data[key]; found {
    		data = val.data
    		c.deleteLruItem(val.lruPos)       //删除原先在list中的位置
    		val.lruPos = c.updateNewItem(key) // 追加到list末尾，更新位置标示
    		c.data[key] = val
    		exist = true
    	}
    	return
    }
    
    func (c *lruCache) deleteLruItem(pos *list.Element) (item *list.Element) {
    	c.lru.Remove(pos)
    	delete(c.data, pos.Value)
    	return
    }
    
    func (c *lruCache) updateNewItem(key interface{}) (item *list.Element) {
    	item = c.lru.PushBack(key)
    	return
    }
    
    func (c *lruCache) Length() int {
    	c.lck.Lock()
    	defer c.lck.Unlock()
    	return len(c.data)
    }
    
    func (c *lruCache) DebugShowMapData() {
    	c.lck.Lock()
    	defer c.lck.Unlock()
    	fmt.Println("=== map ===")
    	for k, v := range c.data {
    		fmt.Println(k, v)
    	}
    	fmt.Println("=== map over ===")
    }
    func (c *lruCache) DebugShowLruList() {
    	c.lck.Lock()
    	defer c.lck.Unlock()
    	fmt.Println("=== list ===")
    	for v := c.lru.Front(); v != nil; v = v.Next() {
    		fmt.Print(v.Value, " ")
    	}
    	fmt.Println("\n=== list over ===")
    }
    
    func (c *lruCache) Delete(key interface{}) {
    	c.lck.Lock()
    	defer c.lck.Unlock()
    	if val, found := c.data[key]; found {
    		c.deleteLruItem(val.lruPos)
    	}
    }

[https_github.com_hackssssss_lruCache]: https://github.com/hackssssss/lruCache