macaddr: add Compare routine

Add a routine to compare macaddr against a reference

Signed-off-by: Jagannathan Raman <[email protected]>

comid/macaddr.go

@@ -1,9 +1,10 @@
-// Copyright 2021-2024 Contributors to the Veraison project.
+// Copyright 2021-2025 Contributors to the Veraison project.
 // SPDX-License-Identifier: Apache-2.0
 
 package comid
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"net"
@@ -16,6 +17,24 @@ import (
 // we need to create an alias type with a custom decoder.
 type MACaddr net.HardwareAddr
 
+func (o *MACaddr) Compare(r *MACaddr) error {
+	claim, err := o.MarshalJSON()
+	if err != nil {
+		return err
+	}
+
+	ref, err := r.MarshalJSON()
+	if err != nil {
+		return err
+	}
+
+	if bytes.Equal(claim, ref) {
+		return nil
+	}
+
+	return fmt.Errorf("macaddr mismatch")
+}
+
 // UnmarshalJSON deserialize a MAC address in textual form into the MACaddr
 // target, e.g.:
 //