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

/* $Id: BitString.java,v 1.4 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.math.BigInteger; 
 
/** 
 * The basic implementation of the ASN.1 BIT STRING type.
 
 * 
 * @version $Revision: 1.4 $ 
 * @author  Raif S. Naffah 
 */ 
public class BitString extends Type implements IType { 
 
	// Constants and vars 
	// ....................................................................... 
 
	static Category cat = Category.getInstance(BitString.class.getName()); 
 
	// Constructor(s) 
	//........................................................................ 
 
	public BitString() { 
		super("", new Tag(Tag.BIT_STRING)); 
	} 
 
	public BitString(String name) { 
		super(name, new Tag(Tag.BIT_STRING)); 
	} 
 
	public BitString(String name, Tag tag) { 
		super(name, tag); 
	} 
 
	public BitString(String name, Object value) { 
		this(name, new Tag(Tag.BIT_STRING), value); 
	} 
 
	/** 
	 * Constructs a new instance of a BIT_STRING type, given a designated Tag 
	 * and a designated initial 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 a byte array. 
	 */ 
	public BitString(String name, Tag tag, Object value) { 
		super(name, tag); 
 
		if (value != null) 
			this.value = (byte[]) ((byte[]) value).clone(); 
 
		if (this.value != null) 
			defaultValue(this.value); 
	} 
 
	// Class methods 
	// ....................................................................... 
 
	/** 
	 * Returns a new instance of this type with a trivial name and the 
	 * designated value. 
	 * 
	 * @param value a designated initial value for the new instance. 
	 * @return a new instance with the designated value. 
	 */ 
	public static BitString getInstance(byte[] value) { 
		return new BitString("", value); 
	} 
 
	// Redefinition of methods in superclass Type 
	// ....................................................................... 
 
	/** 
	 * Decodes a BIT_STRING 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 { 
			byte[] result = is.decodeBitString(this); 
			if (result == null) 
				throw new ElementNotFoundException(cn); 
			else 
				this.value(result); 
		} 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; 
		} 
 
		cat.debug("<== "+cn+".decode()"); 
	} 
 
	/** 
	 * Encodes a BIT_STRING 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()"); 
 
		Object val = this.value(); 
		if (val != null) 
			os.encodeBitString(this, (byte[]) val); 
		else { 
			val = this.defaultValue(); 
			if (val != null) { 
				cat.info("Encoding default value for "+cn); 
				os.encodeBitString(this, (byte[]) val); 
			} else if (!this.isOptional()) 
				throw new BlankElementException(cn); 
//			else { 
//				cat.warn("Encoding a NULL for "+cn); 
//				new Null(this.name()).encode(os); 
//			} 
		} 
 
		cat.debug("<== "+cn+".encode()"); 
	} 
 
	// other instance methods 
	// ....................................................................... 
 
	/** 
	 * Convenience method to facilitate type casting. 
	 * 
	 * @return the current value as a byte array. 
	 */ 
	public byte[] byteArrayValue() { 
		return (byte[]) this.value; 
	} 
 
   /** 
    * Returns true if the designated value is equal to the value of 
    * this instance.
 
    * 
    * @param obj a value to compare with the value of this instance. 
    * @return true if this instance has an equal, non-null value to 
    * the designated one; false otherwise. 
    */ 
   protected boolean sameValue(Object obj) { 
      if (obj == null) 
         return false; 
 
      byte[] other; 
      try { 
         other = (byte[]) obj; 
      } catch (ClassCastException x) { 
         return false; 
      } 
 
      byte[] val = this.byteArrayValue(); 
      if (val == null) 
         return false; 
 
      if (val.length != other.length) 
         return false; 
 
      for (int i = 0; i < val.length; i++) 
         if (val[i] != other[i]) 
            return false; 
 
      return true; 
   } 
 
   // java.lang.Object overloaded methods 
   // ....................................................................... 
 
	/** 
	 * Returns a string representation of this instance in the binary system. 
	 * 
	 * @return a string representation of this instance. 
	 */ 
	public String toString() { 
		StringBuffer sb = new StringBuffer("-- "); 
		if (value != null) 
			sb.append(new BigInteger(1, byteArrayValue()).toString(2)); 
		else 
			sb.append("N/A"); 
 
		return sb.toString(); 
	} 
}