nametransform: move diriv cache into it's own package

Needs some space to grow.

renamed:    internal/nametransform/diriv_cache.go -> internal/nametransform/dirivcache/dirivcache.go

1 files changed, 63 insertions, 0 deletions

diff --git a/internal/nametransform/dirivcache/dirivcache.go b/internal/nametransform/dirivcache/dirivcache.go
new file mode 100644
index 0000000..890ebac
--- /dev/null
+++ b/internal/nametransform/dirivcache/dirivcache.go
@@ -0,0 +1,63 @@
+package dirivcache
+
+import (
+	"sync"
+	"time"
+)
+
+// Single-entry DirIV cache. Stores the directory IV and the encrypted
+// path.
+type DirIVCache struct {
+	// Directory the DirIV belongs to
+	dir string
+	// Time the entry expires.
+	// The cached entry my become out-of-date if the ciphertext directory is
+	// modifed behind the back of gocryptfs. Having an expiry time limits the
+	// inconstency to one second, like attr_timeout does for the kernel
+	// getattr cache.
+	expiry time.Time
+
+	// The DirIV
+	iv []byte
+	// Ecrypted version of "dir"
+	cDir string
+
+	// Invalidated?
+	cleared bool
+	sync.RWMutex
+}
+
+// lookup - fetch entry for "dir" from the cache
+func (c *DirIVCache) Lookup(dir string) ([]byte, string) {
+	c.RLock()
+	defer c.RUnlock()
+	if c.cleared || c.dir != dir {
+		return nil, ""
+	}
+	if time.Since(c.expiry) > 0 {
+		c.cleared = true
+		return nil, ""
+	}
+	return c.iv, c.cDir
+}
+
+// store - write entry for "dir" into the cache
+func (c *DirIVCache) Store(dir string, iv []byte, cDir string) {
+	c.Lock()
+	defer c.Unlock()
+	c.cleared = false
+	c.iv = iv
+	c.dir = dir
+	c.cDir = cDir
+	// Set expiry time one second into the future
+	c.expiry = time.Now().Add(1 * time.Second)
+}
+
+// Clear ... clear the cache.
+// Exported because it is called from fusefrontend when directories are
+// renamed or deleted.
+func (c *DirIVCache) Clear() {
+	c.Lock()
+	defer c.Unlock()
+	c.cleared = true
+}