www.pudn.com > cryptix-asn1-0.1.11.zip > Null.java

/* $Id: Null.java,v 1.1.1.1 2001/02/24 04:59:04 raif Exp $ 
 * 
 * Copyright (C) 1997-2001 The Cryptix Foundation Limited. All rights reserved. 
 * 
 * Use, modification, copying and distribution of this software is subject to 
 * the terms and conditions of the Cryptix General Licence. You should have 
 * received a copy of the Cryptix General Licence along with this library; if 
 * not, you can download a copy from http://www.cryptix.org/ 
 */ 
package cryptix.asn1.lang; 
 
import cryptix.asn1.io.ASNReader; 
import cryptix.asn1.io.ASNWriter; 
 
import org.apache.log4j.Category; 
 
import java.io.EOFException; 
import java.io.IOException; 
 
/** 
 * The basic implementation of an ASN.1 NULL type.
 
 * 
 * @version $Revision: 1.1.1.1 $ 
 * @author  Raif S. Naffah 
 */ 
public class Null extends Type implements IType { 
 
	// Constants and vars 
	// ....................................................................... 
 
	static Category cat = Category.getInstance(Null.class.getName()); 
 
	// Constructor(s) 
	// ....................................................................... 
 
	public Null() { 
		this("", new Tag(Tag.NULL), new Object()); 
	} 
 
	public Null(String name) { 
		this(name, new Tag(Tag.NULL), new Object()); 
	} 
 
	public Null(String name, Tag tag) { 
		this(name, tag, new Object()); 
	} 
 
	public Null(String name, Object value) { 
		this(name, new Tag(Tag.NULL), value); 
	} 
 
	public Null(String name, Tag tag, Object value) { 
		super(name, tag); 
 
		this.value = value; 
	} 
 
	// Redefinition of methods in superclass Type 
	// ....................................................................... 
 
	/** 
	 * Decodes a NULL from an input stream. 
	 * 
	 * @param is the ASN.1 stream to read from. 
	 * @exception IOException if an exception occurs during the operation. 
	 */ 
	public void decode(ASNReader is) throws IOException { 
		String cn = this.getClass().getName(); 
		cat.debug("==> "+cn+".decode()"); 
 
		is.mark(Integer.MAX_VALUE); 
		try { 
			is.decodeNull(this); 
		} catch (IOException x) { 
			cat.warn("Exception ("+String.valueOf(x)+") encountered while decoding a "+cn); 
			if (x instanceof ASNException || x instanceof EOFException) { 
				cat.warn("Resetting input stream..."); 
				is.reset(); 
			} 
			throw x; 
		} 
 
		cat.debug("<== "+cn+".decode()"); 
	} 
 
	/** 
	 * Encodes a NULL to an output stream. 
	 * 
	 * @param os the ASN.1 stream to write to. 
	 * @exception IOException if an exception occurs during the operation. 
	 */ 
	public void encode(ASNWriter os) throws IOException { 
		String cn = this.getClass().getName(); 
		cat.debug("==> "+cn+".encode()"); 
 
		os.encodeNull(this); 
 
		cat.debug("<== "+cn+".encode()"); 
	} 
 
   // java.lang.Object overloaded methods 
   // ....................................................................... 
 
	/** 
	 * Returns a string representation of this instance. 
	 * 
	 * @return a string representation of this instance. 
	 */ 
	public String toString() { 
		StringBuffer sb = new StringBuffer("-- "); 
		if (value != null) 
			sb.append("NULL"); 
		else 
			sb.append("N/A"); 
 
		return sb.toString(); 
	} 
}