Fix #33.

data/file/file.go

@@ -109,18 +109,25 @@ func (me data) WriteSectionTo(w io.Writer, off, n int64) (written int64, err err
 		if err != nil {
 			return
 		}
-		n1, err = io.Copy(w, io.NewSectionReader(f, off, n1))
+		var w1 int64
+		w1, err = io.Copy(w, io.NewSectionReader(f, off, n1))
 		f.Close()
-		if err != nil {
+		written += w1
+		if w1 != n1 {
+			if err == nil || err == io.EOF {
+				err = io.ErrUnexpectedEOF
+			}
 			return
+		} else {
+			err = nil
 		}
-		written += n1
 		off = 0
 		n -= n1
 		if n == 0 {
-			break
+			return
 		}
 	}
+	err = io.EOF
 	return
 }
 

torrent.go

@@ -673,7 +673,7 @@ func (t *torrent) hashPiece(piece pp.Integer) (ps pieceSum) {
 		return
 	}
 	if n != pl {
-		panic("lame")
+		panic(fmt.Sprintf("%T: %d != %d", t.data, n, pl))
 	}
 	missinggo.CopyExact(ps[:], hash.Sum(nil))
 	return