file.go | 2 ++

diff --git a/file.go b/file.go
index 6925101c637f79b9587ce3add782bbcb6641e6d8..5c6d8ebea27e6cb5ff8b0f4d4fcbf0731a204ea4 100644
--- a/file.go
+++ b/file.go
@@ -169,6 +169,7 @@ 	defer f.t.cl.unlock()
 	return f.prio
 }
 
+// Returns the index of the first piece containing data for the file.
 func (f *File) firstPieceIndex() pieceIndex {
 	if f.t.usualPieceSize() == 0 {
 		return 0
@@ -176,6 +177,7 @@ 	}
 	return pieceIndex(f.offset / int64(f.t.usualPieceSize()))
 }
 
+// Returns the index of the piece after the last one containing data for the file.
 func (f *File) endPieceIndex() pieceIndex {
 	if f.t.usualPieceSize() == 0 {
 		return 0