1 files changed, 28 insertions, 4 deletions
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/util.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/util.go
index 229c7d41f..f35976865 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/util.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/util.go
@@ -12,7 +12,8 @@ import (
 )
 
 var (
-	ErrNotFound = errors.New("leveldb: not found")
+	ErrReleased    = errors.New("leveldb: resource already relesed")
+	ErrHasReleaser = errors.New("leveldb: releaser already defined")
 )
 
 // Releaser is the interface that wraps the basic Release method.
@@ -27,23 +28,46 @@ type ReleaseSetter interface {
 	// SetReleaser associates the given releaser to the resources. The
 	// releaser will be called once coresponding resources released.
 	// Calling SetReleaser with nil will clear the releaser.
+	//
+	// This will panic if a releaser already present or coresponding
+	// resource is already released. Releaser should be cleared first
+	// before assigned a new one.
 	SetReleaser(releaser Releaser)
 }
 
 // BasicReleaser provides basic implementation of Releaser and ReleaseSetter.
 type BasicReleaser struct {
 	releaser Releaser
+	released bool
+}
+
+// Released returns whether Release method already called.
+func (r *BasicReleaser) Released() bool {
+	return r.released
 }
 
 // Release implements Releaser.Release.
 func (r *BasicReleaser) Release() {
-	if r.releaser != nil {
-		r.releaser.Release()
-		r.releaser = nil
+	if !r.released {
+		if r.releaser != nil {
+			r.releaser.Release()
+			r.releaser = nil
+		}
+		r.released = true
 	}
 }
 
 // SetReleaser implements ReleaseSetter.SetReleaser.
 func (r *BasicReleaser) SetReleaser(releaser Releaser) {
+	if r.released {
+		panic(ErrReleased)
+	}
+	if r.releaser != nil && releaser != nil {
+		panic(ErrHasReleaser)
+	}
 	r.releaser = releaser
 }
+
+type NoopReleaser struct{}
+
+func (NoopReleaser) Release() {}