Close #10: Added RecoverableError type and IsRecoverableError() method to assist recovery from malformed or unexpected packets.

Author: markus-noga

connection.go

@@ -120,7 +120,7 @@ func (c *Connection) Query(id Identifier) (dg *Datagram, err error) {
 		return nil, err
 	}
 	if dg.Cmd != Response || dg.Id != id {
-		return nil, fmt.Errorf("invalid response: %v", dg)
+		return nil, RecoverableError{fmt.Sprintf("invalid response to read of %08X: %v", id, dg)}
 	}
 	c.cache.Put(dg)
 

datagram.go

@@ -203,7 +203,7 @@ func (d *Datagram) String() string {
 // Returns datagram body value as a float32
 func (d *Datagram) Float32() (val float32, err error) {
 	if len(d.Data) != 4 {
-		return 0, fmt.Errorf("invalid data length %d", len(d.Data))
+		return 0, RecoverableError{fmt.Sprintf("invalid data length %d", len(d.Data))}
 	}
 
 	return math.Float32frombits(binary.BigEndian.Uint32(d.Data)), nil
@@ -212,7 +212,7 @@ func (d *Datagram) Float32() (val float32, err error) {
 // Returns datagram body value as a uint16
 func (d *Datagram) Uint16() (val uint16, err error) {
 	if len(d.Data) != 2 {
-		return 0, fmt.Errorf("invalid data length %d", len(d.Data))
+		return 0, RecoverableError{fmt.Sprintf("invalid data length %d", len(d.Data))}
 	}
 
 	return binary.BigEndian.Uint16(d.Data), nil
@@ -221,7 +221,7 @@ func (d *Datagram) Uint16() (val uint16, err error) {
 // Returns datagram body value as a uint8
 func (d *Datagram) Uint8() (val uint8, err error) {
 	if len(d.Data) != 1 {
-		return 0, fmt.Errorf("invalid data length %d", len(d.Data))
+		return 0, RecoverableError{fmt.Sprintf("invalid data length %d", len(d.Data))}
 	}
 
 	return uint8(d.Data[0]), nil

parse.go

@@ -148,7 +148,7 @@ func (p *DatagramParser) Parse() (dg *Datagram, err error) {
 	//fmt.Printf("(%v)\n", state)
 
 	if state != Done {
-		return dg, fmt.Errorf("parsing failed in state %d", state)
+		return dg, RecoverableError{fmt.Sprintf("parsing failed in state %d", state)}
 	}
 	return dg, nil
 }

recoverable.go

@@ -0,0 +1,17 @@
+package rct;
+
+// Errors caused by a malformed or unexpected packet, which can be potentially be recovered by retrying the transmission
+type RecoverableError struct {
+        Err     string
+}
+
+// Prints error to string
+func (e RecoverableError) Error() string {
+        return e.Err
+}
+
+// Returns true if the given error is potentially recoverable
+func IsRecoverableError(err error) bool {
+        _, ok:=err.(RecoverableError)
+        return ok
+}