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Published: Jan 25, 2016 License: GPL-3.0, MPL-2.0 Imports: 3 Imported by: 6



This provides the lru package which implements a fixed-size thread safe LRU cache. It is based on the cache in Groupcache.


Full docs are available on Godoc


Using the LRU is very simple:

l, _ := New(128)
for i := 0; i < 256; i++ {
    l.Add(i, nil)
if l.Len() != 128 {
    panic(fmt.Sprintf("bad len: %v", l.Len()))



This package provides a simple LRU cache. It is based on the LRU implementation in groupcache:



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type Cache

type Cache struct {
	// contains filtered or unexported fields

Cache is a thread-safe fixed size LRU cache.

func New

func New(size int) (*Cache, error)

New creates an LRU of the given size

func NewWithEvict

func NewWithEvict(size int, onEvicted func(key interface{}, value interface{})) (*Cache, error)

func (*Cache) Add

func (c *Cache) Add(key, value interface{}) bool

Add adds a value to the cache. Returns true if an eviction occured.

func (*Cache) Contains

func (c *Cache) Contains(key interface{}) (ok bool)

Check if a key is in the cache, without updating the recent-ness or deleting it for being stale.

func (*Cache) ContainsOrAdd

func (c *Cache) ContainsOrAdd(key, value interface{}) (ok, evict bool)

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 (*Cache) Get

func (c *Cache) Get(key interface{}) (value interface{}, ok bool)

Get looks up a key's value from the cache.

func (*Cache) Keys

func (c *Cache) Keys() []interface{}

Keys returns a slice of the keys in the cache, from oldest to newest.

func (*Cache) Len

func (c *Cache) Len() int

Len returns the number of items in the cache.

func (*Cache) Peek

func (c *Cache) Peek(key interface{}) (value interface{}, ok bool)

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 (*Cache) Purge

func (c *Cache) Purge()

Purge is used to completely clear the cache

func (*Cache) Remove

func (c *Cache) Remove(key interface{})

Remove removes the provided key from the cache.

func (*Cache) RemoveOldest

func (c *Cache) RemoveOldest()

RemoveOldest removes the oldest item from the cache.

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