mirror of
https://github.com/rclone/rclone.git
synced 2024-11-08 09:35:26 +01:00
135 lines
3.3 KiB
Go
135 lines
3.3 KiB
Go
// Package cache implements a simple cache where the entries are
|
|
// expired after a given time (5 minutes of disuse by default).
|
|
package cache
|
|
|
|
import (
|
|
"sync"
|
|
"time"
|
|
)
|
|
|
|
// Cache holds values indexed by string, but expired after a given (5
|
|
// minutes by default).
|
|
type Cache struct {
|
|
mu sync.Mutex
|
|
cache map[string]*cacheEntry
|
|
expireRunning bool
|
|
expireDuration time.Duration // expire the cache entry when it is older than this
|
|
expireInterval time.Duration // interval to run the cache expire
|
|
}
|
|
|
|
// New creates a new cache with the default expire duration and interval
|
|
func New() *Cache {
|
|
return &Cache{
|
|
cache: map[string]*cacheEntry{},
|
|
expireRunning: false,
|
|
expireDuration: 300 * time.Second,
|
|
expireInterval: 60 * time.Second,
|
|
}
|
|
}
|
|
|
|
// cacheEntry is stored in the cache
|
|
type cacheEntry struct {
|
|
value interface{} // cached item
|
|
err error // creation error
|
|
key string // key
|
|
lastUsed time.Time // time used for expiry
|
|
}
|
|
|
|
// CreateFunc is called to create new values. If the create function
|
|
// returns an error it will be cached if ok is true, otherwise the
|
|
// error will just be returned, allowing negative caching if required.
|
|
type CreateFunc func(key string) (value interface{}, ok bool, error error)
|
|
|
|
// used marks an entry as accessed now and kicks the expire timer off
|
|
// should be called with the lock held
|
|
func (c *Cache) used(entry *cacheEntry) {
|
|
entry.lastUsed = time.Now()
|
|
if !c.expireRunning {
|
|
time.AfterFunc(c.expireInterval, c.cacheExpire)
|
|
c.expireRunning = true
|
|
}
|
|
}
|
|
|
|
// Get gets a value named key either from the cache or creates it
|
|
// afresh with the create function.
|
|
func (c *Cache) Get(key string, create CreateFunc) (value interface{}, err error) {
|
|
c.mu.Lock()
|
|
entry, ok := c.cache[key]
|
|
if !ok {
|
|
c.mu.Unlock() // Unlock in case Get is called recursively
|
|
value, ok, err = create(key)
|
|
if err != nil && !ok {
|
|
return value, err
|
|
}
|
|
entry = &cacheEntry{
|
|
value: value,
|
|
key: key,
|
|
err: err,
|
|
}
|
|
c.mu.Lock()
|
|
c.cache[key] = entry
|
|
}
|
|
defer c.mu.Unlock()
|
|
c.used(entry)
|
|
return entry.value, entry.err
|
|
}
|
|
|
|
// Put puts an value named key into the cache
|
|
func (c *Cache) Put(key string, value interface{}) {
|
|
c.mu.Lock()
|
|
defer c.mu.Unlock()
|
|
entry := &cacheEntry{
|
|
value: value,
|
|
key: key,
|
|
}
|
|
c.used(entry)
|
|
c.cache[key] = entry
|
|
}
|
|
|
|
// GetMaybe returns the key and true if found, nil and false if not
|
|
func (c *Cache) GetMaybe(key string) (value interface{}, found bool) {
|
|
c.mu.Lock()
|
|
defer c.mu.Unlock()
|
|
entry, found := c.cache[key]
|
|
if !found {
|
|
return nil, found
|
|
}
|
|
c.used(entry)
|
|
return entry.value, found
|
|
}
|
|
|
|
// cacheExpire expires any entries that haven't been used recently
|
|
func (c *Cache) cacheExpire() {
|
|
c.mu.Lock()
|
|
defer c.mu.Unlock()
|
|
now := time.Now()
|
|
for key, entry := range c.cache {
|
|
if now.Sub(entry.lastUsed) > c.expireDuration {
|
|
delete(c.cache, key)
|
|
}
|
|
}
|
|
if len(c.cache) != 0 {
|
|
time.AfterFunc(c.expireInterval, c.cacheExpire)
|
|
c.expireRunning = true
|
|
} else {
|
|
c.expireRunning = false
|
|
}
|
|
}
|
|
|
|
// Clear removes everything from the cahce
|
|
func (c *Cache) Clear() {
|
|
c.mu.Lock()
|
|
for k := range c.cache {
|
|
delete(c.cache, k)
|
|
}
|
|
c.mu.Unlock()
|
|
}
|
|
|
|
// Entries returns the number of entries in the cache
|
|
func (c *Cache) Entries() int {
|
|
c.mu.Lock()
|
|
entries := len(c.cache)
|
|
c.mu.Unlock()
|
|
return entries
|
|
}
|