Add ASN1TaggedObject getOptional methods

Author: peterdettman

core/src/main/java/org/bouncycastle/asn1/ASN1TaggedObject.java

@@ -75,6 +75,41 @@ public static ASN1TaggedObject getInstance(ASN1TaggedObject taggedObject, int ta
         return ASN1Util.getExplicitBaseTagged(checkInstance(taggedObject, declaredExplicit), tagClass, tagNo);
     }
 
+    public static ASN1TaggedObject getOptional(ASN1Object element)
+    {
+        if (element == null)
+        {
+            throw new NullPointerException("'element' cannot be null");
+        }
+
+        if (element instanceof ASN1TaggedObject)
+        {
+            return (ASN1TaggedObject)element;
+        }
+
+        return null;
+    }
+
+    public static ASN1TaggedObject getOptional(ASN1Object element, int tagClass)
+    {
+        ASN1TaggedObject taggedObject = getOptional(element);
+        if (taggedObject != null && taggedObject.hasTagClass(tagClass))
+        {
+            return taggedObject;
+        }
+        return null;
+    }
+
+    public static ASN1TaggedObject getOptional(ASN1Object element, int tagClass, int tagNo)
+    {
+        ASN1TaggedObject taggedObject = getOptional(element);
+        if (taggedObject != null && taggedObject.hasTag(tagClass, tagNo))
+        {
+            return taggedObject;
+        }
+        return null;
+    }
+
     private static ASN1TaggedObject checkInstance(Object obj)
     {
         if (obj == null)