1 files changed, 43 insertions, 0 deletions
diff --git a/internal/nametransform/diriv_cache.go b/internal/nametransform/diriv_cache.go
new file mode 100644
index 0000000..c6f2ca9
--- /dev/null
+++ b/internal/nametransform/diriv_cache.go
@@ -0,0 +1,43 @@
+package nametransform
+
+import "sync"
+
+// A simple one-entry DirIV cache
+type dirIVCache struct {
+	// Invalidated?
+	cleared bool
+	// The DirIV
+	iv []byte
+	// Directory the DirIV belongs to
+	dir string
+	// Ecrypted version of "dir"
+	translatedDir string
+	// Synchronisation
+	lock sync.RWMutex
+}
+
+// lookup - fetch entry for "dir" from the cache
+func (c *dirIVCache) lookup(dir string) (bool, []byte, string) {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	if !c.cleared && c.dir == dir {
+		return true, c.iv, c.translatedDir
+	}
+	return false, nil, ""
+}
+
+// store - write entry for "dir" into the caches
+func (c *dirIVCache) store(dir string, iv []byte, translatedDir string) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.cleared = false
+	c.iv = iv
+	c.dir = dir
+	c.translatedDir = translatedDir
+}
+
+func (c *dirIVCache) Clear() {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.cleared = true
+}