/**
* Return an ASN1 sequence from a tagged object. There is a special case here, if an object
* appears to have been explicitly tagged on reading but we were expecting it to be implictly
* tagged in the normal course of events it indicates that we lost the surrounding sequence - so
* we need to add it back (this will happen if the tagged object is a sequence that contains other
* sequences). If you are dealing with implicitly tagged sequences you really <b>should</b> be
* using this method.
*
* @param obj the tagged object.
* @param explicit true if the object is meant to be explicitly tagged, false otherwise.
* @exception IllegalArgumentException if the tagged object cannot be converted.
*/
public static ASN1Sequence getInstance(ASN1TaggedObject obj, boolean explicit) {
if (explicit) {
if (!obj.isExplicit()) {
throw new IllegalArgumentException("object implicit - explicit expected.");
}
return (ASN1Sequence) obj.getObject();
} else {
//
// constructed object which appears to be explicitly tagged
// when it should be implicit means we have to add the
// surrounding sequence.
//
if (obj.isExplicit()) {
ASN1Sequence seq;
if (obj instanceof BERTaggedObject) {
seq = new BERConstructedSequence();
} else {
seq = new DERConstructedSequence();
}
seq.addObject(obj.getObject());
return seq;
} else {
ASN1Sequence seq;
if (obj.getObject() instanceof ASN1Sequence) {
return (ASN1Sequence) obj.getObject();
}
}
}
throw new IllegalArgumentException("unknown object in getInstanceFromTagged");
}