dir_entry_cache.go

package adbfs

import (
	"time"

	cache "github.com/pmylund/go-cache"
	"golang.org/x/net/trace"
)

const CachePurgeInterval = 5 * time.Minute

type DirEntryLoader func(path string) (*CachedDirEntries, error)

// DirEntryCache is a key-value cache of normalized directory paths to
// slices of *adb.FileEntries.
type DirEntryCache interface {
	GetOrLoad(path string, loader DirEntryLoader) (entries *CachedDirEntries, err error, hit bool)
	Get(path string) (entries *CachedDirEntries, found bool)
	// Removes the entry for path from the cache without blocking on other cache operations.
	RemoveEventually(path string)
}

type realDirEntryCache struct {
	cache    *cache.Cache
	eventLog trace.EventLog
}

func NewDirEntryCache(ttl time.Duration) DirEntryCache {
	return &realDirEntryCache{
		cache:    cache.New(ttl, CachePurgeInterval),
		eventLog: trace.NewEventLog("DirEntryCache", ""),
	}
}

func (c *realDirEntryCache) GetOrLoad(path string, loader DirEntryLoader) (*CachedDirEntries, error, bool) {
	if entries, found := c.Get(path); found {
		return entries, nil, true
	}

	entries, err := loader(path)
	if err != nil {
		return nil, err, false
	}

	c.cache.Set(path, entries, cache.DefaultExpiration)
	return entries, nil, false
}

func (c *realDirEntryCache) Get(path string) (*CachedDirEntries, bool) {
	if entries, found := c.cache.Get(path); found {
		c.eventLog.Printf("Get(%s) = hit", path)
		return entries.(*CachedDirEntries), true
	}
	c.eventLog.Errorf("Get(%s) = miss", path)
	return nil, false
}

func (c *realDirEntryCache) RemoveEventually(path string) {
	go c.cache.Delete(path)
}