metainfo/metainfo.go | 5 +++++

diff --git a/metainfo/metainfo.go b/metainfo/metainfo.go
index 872407b4972697c78dd3d0497bfb563366a55cc4..a9a6e00971f77c1d0bdf9f7d4aed08b0e6d2e29b 100644
--- a/metainfo/metainfo.go
+++ b/metainfo/metainfo.go
@@ -64,6 +64,7 @@
 type Piece interface {
 	Hash() []byte
 	Length() int64
+	Offset() int64
 }
 
 type piece struct {
@@ -76,6 +77,10 @@ 	if me.i == me.Info.NumPieces()-1 {
 		return me.Info.TotalLength() - int64(me.i)*me.Info.PieceLength
 	}
 	return me.Info.PieceLength
+}
+
+func (me piece) Offset() int64 {
+	return int64(me.i) * me.Info.PieceLength
 }
 
 func (me piece) Hash() []byte {