use unix nanoseconds for encoding Cbortime

utils.go

@@ -696,43 +696,22 @@ func (ci *CborInt) UnmarshalCBOR(r io.Reader) error {
 type CborTime time.Time
 
 func (ct *CborTime) MarshalCBOR(w io.Writer) error {
-	b, err := (*time.Time)(ct).MarshalBinary()
-	if err != nil {
-		return err
-	}
+	nsecs := ct.Time().UnixNano()
 
-	if err := CborWriteHeader(w, MajByteString, uint64(len(b))); err != nil {
-		return err
-	}
+	cbi := CborInt(nsecs)
 
-	if _, err := w.Write(b); err != nil {
-		return err
-	}
-
-	return nil
+	return cbi.MarshalCBOR(w)
 }
 
 func (ct *CborTime) UnmarshalCBOR(r io.Reader) error {
-	t, l, err := CborReadHeader(r)
-	if err != nil {
+	var cbi CborInt
+	if err := cbi.UnmarshalCBOR(r); err != nil {
 		return err
 	}
 
-	if t != MajByteString {
-		return fmt.Errorf("CborTime expects to find a byte array (got %d)", t)
-	}
-
-	buf := make([]byte, l)
-	if _, err := io.ReadFull(r, buf); err != nil {
-		return err
-	}
-
-	tm := time.Time{}
-	if err := tm.UnmarshalBinary(buf); err != nil {
-		return err
-	}
+	t := time.Unix(0, int64(cbi))
 
-	*ct = (CborTime)(tm)
+	*ct = (CborTime)(t)
 	return nil
 }