handle nil onData

common/buf/io.go

@@ -53,6 +53,22 @@ type copyHandler struct {
 	onWriteError func(error) error
 }
 
+func (h *copyHandler) readFrom(reader Reader) (MultiBuffer, error) {
+	mb, err := reader.Read()
+	if err != nil && h.onReadError != nil {
+		err = h.onReadError(err)
+	}
+	return mb, err
+}
+
+func (h *copyHandler) writeTo(writer Writer, mb MultiBuffer) error {
+	err := writer.Write(mb)
+	if err != nil && h.onWriteError != nil {
+		err = h.onWriteError(err)
+	}
+	return err
+}
+
 type CopyOption func(*copyHandler)
 
 func IgnoreReaderError() CopyOption {
@@ -79,37 +95,35 @@ func UpdateActivity(timer signal.ActivityTimer) CopyOption {
 	}
 }
 
-func copyInternal(reader Reader, writer Writer, handler copyHandler) error {
+func copyInternal(reader Reader, writer Writer, handler *copyHandler) error {
 	for {
-		buffer, err := reader.Read()
+		buffer, err := handler.readFrom(reader)
 		if err != nil {
-			if err = handler.onReadError(err); err != nil {
 			return err
 		}
-		}
-
-		handler.onData()
 
 		if buffer.IsEmpty() {
 			buffer.Release()
 			continue
 		}
 
-		if err := writer.Write(buffer); err != nil {
-			if err = handler.onWriteError(err); err != nil {
+		if handler.onData != nil {
+			handler.onData()
+		}
+
+		if err := handler.writeTo(writer, buffer); err != nil {
 			buffer.Release()
 			return err
 		}
 	}
 }
-}
 
 // Copy dumps all payload from reader to writer or stops when an error occurs.
 // ActivityTimer gets updated as soon as there is a payload.
 func Copy(reader Reader, writer Writer, options ...CopyOption) error {
-	handler := copyHandler{}
+	handler := new(copyHandler)
 	for _, option := range options {
-		option(&handler)
+		option(handler)
 	}
 	err := copyInternal(reader, writer, handler)
 	if err != nil && errors.Cause(err) != io.EOF {