choice.java

JAVA的加密库之一

/* $Id: Choice.java,v 1.7 2001/05/26 07:10:24 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 cryptix.asn1.io.BlankElementException;
import cryptix.asn1.io.ElementNotFoundException;

import org.apache.log4j.Category;

import java.io.EOFException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.ListIterator;

/**
 * The basic implementation of the ASN.1 CHOICE type.<p>
 *
 * The CHOICE alternatives are grouped in a <tt>java.util.ArrayList</tt>, with
 * a provided implementation of the <tt>cryptix.asn1.lang.IIterativeType</tt>
 * interface to iterate over them. The value of a CHOICE is the first non-blank
 * type among those contained in its components.<p>
 *
 * @version $Revision: 1.7 $
 * @author  Raif S. Naffah
 */
public abstract class Choice extends Set {

	// Constants and vars
	// .......................................................................

	static Category cat = Category.getInstance(Choice.class.getName());

	// Constructor(s)
	// .......................................................................

	public Choice(Tag tag) {
		super("", tag);
	}

	public Choice(String name, Tag tag) {
		super(name, tag);
	}

	/**
	 * Constructs a new instance of a CHOICE type, given a designated Tag and a
	 * designated default value.
	 *
	 * @param name the name of this instance.
	 * @param tag the designated Tag value.
	 * @param value the designated initial value.
	 * @exception ClassCastException if the designated value is not an IType.
	 */
	public Choice(String name, Tag tag, Object value) {
		super(name, tag);

		if (value != null)
			if (value instanceof ArrayList) {
				value(value);
			} else
				throw new ClassCastException();
	}

	// Redefinition of methods in superclass Type
	// .......................................................................

	/**
	 * Decodes a CHOICE 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()");

		this.reset();

		is.mark(Integer.MAX_VALUE);
		IType t;
		boolean found = false;
		cat.info("Looking for a valid ASN.1 alternative for a CHOICE.");
		try {
			IType e = is.decodeAny("choice");
			Iterator it = this.iterator();
			while (it.hasNext()) {
				t = (Type) it.next();
				found = t.tag().equals(e.tag());
				if (found) {
					cat.info("Found a "+t.getClass().getName());
					t.value(e.value());
					break;
				}
			}
		} catch (IOException x) {
			cat.warn("Exception ("+String.valueOf(x)+") encountered while decoding a "+cn);
			if (x instanceof ASNException || x instanceof EOFException) {
				cat.warn("Resetting stream...");
				is.reset();
			}

			throw x;
		}

		if (!found && !isOptional())
			throw new ASNException("No valid alternative for "+cn+" (CHOICE) was found...");

		cat.debug("<== "+cn+".decode()");
	}

	/**
	 * Encodes a CHOICE to an output stream.
	 *
	 * @param os the ASN.1 stream to write to.
	 * @exception RuntimeException always.
	 */
	public void encode(ASNWriter os) throws IOException {
		String cn = this.getClass().getName();
		cat.debug("==> "+cn+".encode()");

		boolean found = false;
		for (Iterator it = this.iterator(); it.hasNext(); ) {
			IType t = (Type) it.next();
			found = !t.isBlank();
			if (found) {
				cat.info("Encoding "+t.getClass().getName()+"...");
				t.encode(os);
				break;
			}
		}

		if (!found && !isOptional())
			throw new BlankElementException(cn);

		cat.debug("<== "+cn+".encode()");
	}

	/**
	 * Sets the current value of this instance to the designated one. For a
	 * CHOICE, this operation consists of iterating through the elements of
	 * the designated value, and assigning the first non-blank element (with
	 * the same tag) in this instance's corresponding component, the value of
	 * the element from value.
	 *
	 * @param value the new value to assign to this instance.
	 */
	public void value(Object value) {
		String cn = this.getClass().getName();
		cat.debug("==> "+cn+".value("+String.valueOf(value)+")");
      cat.debug("value is a "+String.valueOf(value.getClass().getName()));
      if (value instanceof IType)
         cat.debug("Tag="+String.valueOf( ((IType) value).tag() ));

		this.reset();

      if (value instanceof Any) {
         Any src = (Any) value;
   		for (Iterator dst = this.iterator(); dst.hasNext(); ) {
   			IType td = (IType) dst.next();
   		   if (td.tag().equals(src.tag())) {
   		      td.value(src.value());
      			cat.info("Assigned value to "+td.getClass().getName());
   		      break;
   		   }
   		}
      } else {
         if (value instanceof IType)
            value = ((IType) value).value();

   		Iterator src;
   		if (value instanceof ArrayList)
   		   src = ((ArrayList) value).iterator();
   		else
   		   src = ((ArrayList) ((Any) value).value()).iterator();

   		Iterator dst = this.iterator();
   		while (src.hasNext() && dst.hasNext()) {
   			IType ts = (IType) src.next();
   			IType td = (IType) dst.next();
   			// what checks should we make? remember that any term may be an ANY
   			// (with a null tag)?
   			cat.info("Assigning value from "+ts.getClass().getName()+" to "+td.getClass().getName());
   			td.value(ts.value());
   		}
		}

		cat.debug("<== "+cn+".value()");
	}

   // java.lang.Object overloaded methods
   // .......................................................................

	/**
	 * Returns a string representation of this instance.
	 *
	 * @return a string representation of this instance.
	 */
	public String toString() {
		String cn = this.getClass().getName();
		String ls = System.getProperty("line.separator");
		StringBuffer sb = new StringBuffer(ls);
		sb.append("-- Begin ").append(cn).append(" (CHOICE)").append(ls);
		int i = 1;
		boolean found = false;
		for (Iterator it = this.iterator(); it.hasNext(); i++) {
			IType t = (Type) it.next();
			found = !t.isBlank();
			if (found) {
				sb.append("--   alternative #").append(i)
					.append(" (").append(t.getClass().getName()).append("): ")
					.append(String.valueOf(t)).append(ls);
				break;
			}
		}

		if (!found)
			sb.append("--   N/A").append(ls);

		sb.append("-- End ").append(cn).append(" (CHOICE)");
		return sb.toString();
	}
}