Improve compatibility checking

- added CompatibilityError to api package to represent error with
  list of incompatible messages
- added UnknownMsgError to adapter package to represent error for
  unknown message
- added list of registered message types

Change-Id: I2623b45135521d52612ba91e4605fc064a7fc76e
Signed-off-by: Ondrej Fabry <ofabry@cisco.com>

3 files changed, 14 insertions, 2 deletions

diff --git a/adapter/socketclient/socketclient.go b/adapter/socketclient/socketclient.go
index 043d253..366163f 100644
--- a/adapter/socketclient/socketclient.go
+++ b/adapter/socketclient/socketclient.go
@@ -419,7 +419,7 @@ func (c *vppClient) GetMsgID(msgName string, msgCrc string) (uint16, error) {
 	msg := msgName + "_" + msgCrc
 	msgID, ok := c.msgTable[msg]
 	if !ok {
-		return 0, fmt.Errorf("unknown message: %q", msg)
+		return 0, &adapter.UnknownMsgError{msgName, msgCrc}
 	}
 	return msgID, nil
 }
diff --git a/adapter/vpp_api.go b/adapter/vpp_api.go
index 71bf7c2..b32f975 100644
--- a/adapter/vpp_api.go
+++ b/adapter/vpp_api.go
@@ -16,6 +16,7 @@ package adapter
 
 import (
 	"errors"
+	"fmt"
 )
 
 const (
@@ -52,3 +53,14 @@ type VppAPI interface {
 	// WaitReady waits until adapter is ready.
 	WaitReady() error
 }
+
+// UnknownMsgError is the error type usually returned by GetMsgID
+// method of VppAPI. It describes the name and CRC for the unknown message.
+type UnknownMsgError struct {
+	MsgName string
+	MsgCrc  string
+}
+
+func (u *UnknownMsgError) Error() string {
+	return fmt.Sprintf("unknown message: %s_%s", u.MsgName, u.MsgCrc)
+}
diff --git a/adapter/vppapiclient/vppapiclient.go b/adapter/vppapiclient/vppapiclient.go
index fcd3f3f..977f32d 100644
--- a/adapter/vppapiclient/vppapiclient.go
+++ b/adapter/vppapiclient/vppapiclient.go
@@ -116,7 +116,7 @@ func (a *vppClient) GetMsgID(msgName string, msgCrc string) (uint16, error) {
 	msgID := uint16(C.govpp_get_msg_index(nameAndCrc))
 	if msgID == ^uint16(0) {
 		// VPP does not know this message
-		return msgID, fmt.Errorf("unknown message: %v (crc: %v)", msgName, msgCrc)
+		return msgID, &adapter.UnknownMsgError{msgName, msgCrc}
 	}
 
 	return msgID, nil