114 lines
2.7 KiB
Go
114 lines
2.7 KiB
Go
// This package provides a simple LRU cache. It is based on the
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// LRU implementation in groupcache:
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// https://github.com/golang/groupcache/tree/master/lru
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package lru
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import (
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"sync"
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"github.com/hashicorp/golang-lru/simplelru"
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)
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// Cache is a thread-safe fixed size LRU cache.
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type Cache struct {
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lru *simplelru.LRU
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lock sync.RWMutex
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}
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// New creates an LRU of the given size
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func New(size int) (*Cache, error) {
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return NewWithEvict(size, nil)
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}
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// NewWithEvict constructs a fixed size cache with the given eviction
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// callback.
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func NewWithEvict(size int, onEvicted func(key interface{}, value interface{})) (*Cache, error) {
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lru, err := simplelru.NewLRU(size, simplelru.EvictCallback(onEvicted))
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if err != nil {
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return nil, err
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}
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c := &Cache{
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lru: lru,
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}
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return c, nil
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}
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// Purge is used to completely clear the cache
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func (c *Cache) Purge() {
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c.lock.Lock()
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c.lru.Purge()
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c.lock.Unlock()
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}
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// Add adds a value to the cache. Returns true if an eviction occurred.
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func (c *Cache) Add(key, value interface{}) bool {
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c.lock.Lock()
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defer c.lock.Unlock()
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return c.lru.Add(key, value)
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}
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// Get looks up a key's value from the cache.
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func (c *Cache) Get(key interface{}) (interface{}, bool) {
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c.lock.Lock()
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defer c.lock.Unlock()
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return c.lru.Get(key)
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}
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// Check if a key is in the cache, without updating the recent-ness
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// or deleting it for being stale.
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func (c *Cache) Contains(key interface{}) bool {
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c.lock.RLock()
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defer c.lock.RUnlock()
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return c.lru.Contains(key)
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}
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// Returns the key value (or undefined if not found) without updating
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// the "recently used"-ness of the key.
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func (c *Cache) Peek(key interface{}) (interface{}, bool) {
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c.lock.RLock()
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defer c.lock.RUnlock()
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return c.lru.Peek(key)
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}
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// ContainsOrAdd checks if a key is in the cache without updating the
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// recent-ness or deleting it for being stale, and if not, adds the value.
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// Returns whether found and whether an eviction occurred.
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func (c *Cache) ContainsOrAdd(key, value interface{}) (ok, evict bool) {
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c.lock.Lock()
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defer c.lock.Unlock()
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if c.lru.Contains(key) {
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return true, false
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} else {
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evict := c.lru.Add(key, value)
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return false, evict
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}
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}
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// Remove removes the provided key from the cache.
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func (c *Cache) Remove(key interface{}) {
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c.lock.Lock()
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c.lru.Remove(key)
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c.lock.Unlock()
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}
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// RemoveOldest removes the oldest item from the cache.
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func (c *Cache) RemoveOldest() {
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c.lock.Lock()
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c.lru.RemoveOldest()
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c.lock.Unlock()
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}
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// Keys returns a slice of the keys in the cache, from oldest to newest.
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func (c *Cache) Keys() []interface{} {
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c.lock.RLock()
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defer c.lock.RUnlock()
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return c.lru.Keys()
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}
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// Len returns the number of items in the cache.
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func (c *Cache) Len() int {
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c.lock.RLock()
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defer c.lock.RUnlock()
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return c.lru.Len()
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}
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