extract the redundant code into method

credentials/generate-revocation-set.py

@@ -64,6 +64,17 @@ def extract_single_integer_attribute(subject, oid):
  return None
 
 
+def extract_single_attribute_from_cn(cn, marker):
+ val_len = 4
+ start_idx = cn.find(marker)
+
+ if start_idx != -1:
+ val_start_idx = start_idx + len(marker)
+ return int(cn[val_start_idx:val_start_idx + val_len], 16)
+
+ return None
+
+
 def parse_vid_pid_from_distinguished_name(distinguished_name):
  # VID/PID encoded using Matter specific RDNs
  vid = extract_single_integer_attribute(distinguished_name, OID_VENDOR_ID)
@@ -72,14 +83,8 @@ def parse_vid_pid_from_distinguished_name(distinguished_name):
  # Fallback method to get the VID/PID, encoded in CN as "Mvid:FFFF Mpid:1234"
  if vid is None and pid is None:
  cn = distinguished_name.get_attributes_for_oid(x509.ObjectIdentifier("2.5.4.3"))[0].value
-
- vid_start = cn.find('Mvid:')
- if vid_start != -1:
- vid = int(cn[vid_start + 5:vid_start + 9], 16)
-
- pid_start = cn.find('Mpid:')
- if pid_start != -1:
- pid = int(cn[pid_start + 5:pid_start + 9], 16)
+ vid = extract_single_attribute_from_cn(cn, 'Mvid:')
+ pid = extract_single_attribute_from_cn(cn, 'Mpid:')
 
  return vid, pid