fs/cache: factor Fs caching from fs/rc into its own package

fs/rc/cache.go

@@ -1,86 +1,12 @@
-// This implements the Fs cache
+// Utilities for accessing the Fs cache
 
 package rc
 
 import (
-	"sync"
-	"time"
-
 	"github.com/ncw/rclone/fs"
+	"github.com/ncw/rclone/fs/cache"
 )
 
-var (
-	fsCacheMu           sync.Mutex
-	fsCache             = map[string]*cacheEntry{}
-	fsNewFs             = fs.NewFs // for tests
-	expireRunning       = false
-	cacheExpireDuration = 300 * time.Second // expire the cache entry when it is older than this
-	cacheExpireInterval = 60 * time.Second  // interval to run the cache expire
-)
-
-type cacheEntry struct {
-	f        fs.Fs
-	fsString string
-	lastUsed time.Time
-}
-
-// GetCachedFs gets a fs.Fs named fsString either from the cache or creates it afresh
-func GetCachedFs(fsString string) (f fs.Fs, err error) {
-	fsCacheMu.Lock()
-	defer fsCacheMu.Unlock()
-	entry, ok := fsCache[fsString]
-	if !ok {
-		f, err = fsNewFs(fsString)
-		if err != nil {
-			return nil, err
-		}
-		entry = &cacheEntry{
-			f:        f,
-			fsString: fsString,
-		}
-		fsCache[fsString] = entry
-	}
-	entry.lastUsed = time.Now()
-	if !expireRunning {
-		time.AfterFunc(cacheExpireInterval, cacheExpire)
-		expireRunning = true
-	}
-	return entry.f, err
-}
-
-// PutCachedFs puts an fs.Fs named fsString into the cache
-func PutCachedFs(fsString string, f fs.Fs) {
-	fsCacheMu.Lock()
-	defer fsCacheMu.Unlock()
-	fsCache[fsString] = &cacheEntry{
-		f:        f,
-		fsString: fsString,
-		lastUsed: time.Now(),
-	}
-	if !expireRunning {
-		time.AfterFunc(cacheExpireInterval, cacheExpire)
-		expireRunning = true
-	}
-}
-
-// cacheExpire expires any entries that haven't been used recently
-func cacheExpire() {
-	fsCacheMu.Lock()
-	defer fsCacheMu.Unlock()
-	now := time.Now()
-	for fsString, entry := range fsCache {
-		if now.Sub(entry.lastUsed) > cacheExpireDuration {
-			delete(fsCache, fsString)
-		}
-	}
-	if len(fsCache) != 0 {
-		time.AfterFunc(cacheExpireInterval, cacheExpire)
-		expireRunning = true
-	} else {
-		expireRunning = false
-	}
-}
-
 // GetFsNamed gets a fs.Fs named fsName either from the cache or creates it afresh
 func GetFsNamed(in Params, fsName string) (f fs.Fs, err error) {
 	fsString, err := in.GetString(fsName)
@@ -88,7 +14,7 @@ func GetFsNamed(in Params, fsName string) (f fs.Fs, err error) {
 		return nil, err
 	}
 
-	return GetCachedFs(fsString)
+	return cache.Get(fsString)
 }
 
 // GetFs gets a fs.Fs named "fs" either from the cache or creates it afresh