111 lines
2.4 KiB
Go
111 lines
2.4 KiB
Go
// Copyright 2016 the Go-FUSE Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package unionfs
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import (
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"sync"
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"time"
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)
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type cacheEntry struct {
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data interface{}
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// expiry is the absolute timestamp of the expiry.
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expiry time.Time
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}
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// TimedIntCache caches the result of fetch() for some time. It is
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// thread-safe. Calls of fetch() do no happen inside a critical
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// section, so when multiple concurrent Get()s happen for the same
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// key, multiple fetch() calls may be issued for the same key.
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type TimedCacheFetcher func(name string) (value interface{}, cacheable bool)
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type TimedCache struct {
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fetch TimedCacheFetcher
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// ttl is the duration of the cache.
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ttl time.Duration
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cacheMapMutex sync.RWMutex
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cacheMap map[string]*cacheEntry
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PurgeTimer *time.Timer
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}
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// Creates a new cache with the given TTL. If TTL <= 0, the caching is
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// indefinite.
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func NewTimedCache(fetcher TimedCacheFetcher, ttl time.Duration) *TimedCache {
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l := new(TimedCache)
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l.ttl = ttl
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l.fetch = fetcher
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l.cacheMap = make(map[string]*cacheEntry)
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return l
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}
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func (c *TimedCache) Get(name string) interface{} {
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c.cacheMapMutex.RLock()
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info, ok := c.cacheMap[name]
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c.cacheMapMutex.RUnlock()
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valid := ok && (c.ttl <= 0 || info.expiry.After(time.Now()))
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if valid {
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return info.data
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}
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return c.GetFresh(name)
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}
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func (c *TimedCache) Set(name string, val interface{}) {
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c.cacheMapMutex.Lock()
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defer c.cacheMapMutex.Unlock()
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c.cacheMap[name] = &cacheEntry{
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data: val,
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expiry: time.Now().Add(c.ttl),
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}
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}
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func (c *TimedCache) DropEntry(name string) {
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c.cacheMapMutex.Lock()
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defer c.cacheMapMutex.Unlock()
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delete(c.cacheMap, name)
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}
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func (c *TimedCache) GetFresh(name string) interface{} {
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data, ok := c.fetch(name)
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if ok {
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c.Set(name, data)
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}
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return data
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}
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// Drop all expired entries.
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func (c *TimedCache) Purge() {
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keys := make([]string, 0, len(c.cacheMap))
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now := time.Now()
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c.cacheMapMutex.Lock()
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defer c.cacheMapMutex.Unlock()
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for k, v := range c.cacheMap {
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if now.After(v.expiry) {
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keys = append(keys, k)
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}
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}
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for _, k := range keys {
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delete(c.cacheMap, k)
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}
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}
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func (c *TimedCache) DropAll(names []string) {
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c.cacheMapMutex.Lock()
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defer c.cacheMapMutex.Unlock()
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if names == nil {
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c.cacheMap = make(map[string]*cacheEntry, len(c.cacheMap))
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} else {
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for _, nm := range names {
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delete(c.cacheMap, nm)
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}
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}
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}
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