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

/* $Id: ASNReader.java,v 1.1.1.1 2001/02/24 04:59:02 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.io; 
 
import cryptix.asn1.lang.IIterativeType; 
import cryptix.asn1.lang.IType; 
import java.io.InputStream; 
import java.io.IOException; 
import java.math.BigInteger; 
import java.util.Date; 
 
/** 
 * An abstract class that offers the minimal operations to decode a 
 * concrete ASN.1 stream.
 
 * 
 * @version $Revision: 1.1.1.1 $ 
 * @author  Raif S. Naffah 
 */ 
public abstract class ASNReader extends InputStream { 
 
	/** 
	 * Initialises this instance to decode from the designated input stream. 
	 * 
	 * @param is the designated input stream to decode. 
	 * @exception IllegalStateException if this instance is already initialised 
	 * with an input stream. Caller should close the previous stream before 
	 * invoking this method again on a new input stream. 
	 */ 
	public abstract void open(InputStream is); 
 
	/** 
	 * Decodes an ANY from the input stream. 
	 * 
	 * @param name the optional user-defined ASN.1 type name. 
	 * @return the concrete object decoded from the underlying input stream. 
	 * @exception IOException if an I/O related exception has occured. 
	 */ 
	public abstract IType decodeAny(String name) throws IOException; 
 
	/** 
	 * Decodes an OBJECT IDENTIFIER from the input stream. 
	 * 
	 * @param obj the element to decode. 
	 * @return a String representation of the OID decoded from the stream. 
	 * @exception EOFException if the end-of-stream was encountered while 
	 * decoding the element. 
	 * @exception IOException if any other I/O related exception has occured. 
	 */ 
	public abstract String decodeObjectIdentifier(IType obj) throws IOException; 
 
	/** 
	 * Decodes a NULL from the input stream. 
	 * 
	 * @param obj the element to decode. 
	 * @exception EOFException if the end-of-stream was encountered while 
	 * decoding the element. 
	 * @exception IOException if any other I/O related exception has occured. 
	 */ 
	public abstract void decodeNull(IType obj) throws IOException; 
 
	/** 
	 * Decodes a BOOLEAN from the input stream. 
	 * 
	 * @param obj the element to decode. 
	 * @return the concrete value of this ASN.1 type. 
	 * @exception EOFException if the end-of-stream was encountered while 
	 * decoding the element. 
	 * @exception IOException if any other I/O related exception has occured. 
	 */ 
	public abstract Boolean decodeBoolean(IType obj) throws IOException; 
 
	/** 
	 * Decodes an INTEGER from the input stream. 
	 * 
	 * @param obj the element to decode. 
	 * @return the concrete value of this ASN.1 type. 
	 * @exception EOFException if the end-of-stream was encountered while 
	 * decoding the element. 
	 * @exception IOException if any other I/O related exception has occured. 
	 */ 
	public abstract BigInteger decodeInteger(IType obj) throws IOException; 
 
	/** 
	 * Decodes a PrintableString from the input stream. 
	 * 
	 * @param tagValue the value of a Tag constant to differentiate between 
	 * the different types of strings. 
	 * @param obj the element to decode. 
	 * @return the concrete value of this ASN.1 type. 
	 * @exception EOFException if the end-of-stream was encountered while 
	 * decoding the element. 
	 * @exception IOException if any other I/O related exception has occured. 
	 */ 
	public abstract String decodeString(int tagValue, IType obj) throws IOException; 
 
	/** 
	 * Decodes a BIT STRING from the input stream. 
	 * 
	 * @param obj the element to decode. 
	 * @return the concrete value of this ASN.1 type. 
	 * @exception EOFException if the end-of-stream was encountered while 
	 * decoding the element. 
	 * @exception IOException if any other I/O related exception has occured. 
	 */ 
	public abstract byte[] decodeBitString(IType obj) throws IOException; 
 
	/** 
	 * Decodes an OCTET STRING from the input stream. 
	 * 
	 * @param obj the element to decode. 
	 * @return the concrete value of this ASN.1 type. 
	 * @exception EOFException if the end-of-stream was encountered while 
	 * decoding the element. 
	 * @exception IOException if any other I/O related exception has occured. 
	 */ 
	public abstract byte[] decodeOctetString(IType obj) throws IOException; 
 
	/** 
	 * Decodes a UTCTime from the input stream. 
	 * 
	 * @param obj the element to decode. 
	 * @return the concrete value of this ASN.1 type. 
	 * @exception EOFException if the end-of-stream was encountered while 
	 * decoding the element. 
	 * @exception IOException if any other I/O related exception has occured. 
	 */ 
	public abstract Date decodeUTCTime(IType obj) throws IOException; 
 
	/** 
	 * Decodes a GeneralizedTime from the input stream. 
	 * 
	 * @param obj the element to decode. 
	 * @return the concrete value of this ASN.1 type. 
	 * @exception EOFException if the end-of-stream was encountered while 
	 * decoding the element. 
	 * @exception IOException if any other I/O related exception has occured. 
	 */ 
	public abstract Date decodeGeneralizedTime(IType obj) throws IOException; 
 
   /** 
    * Decodes a compund type (SEQUENCE/SET [OF]) from the input stream. 
    * 
    * @param obj the compound element to decode. 
    * @return a Decoder that parses the input stream according to the same 
    * encoding rules as this one. 
    * @exception EOFException if the end-of-stream was encountered while 
    * decoding the element. 
    * @exception IOException if any other I/O related exception has occured. 
    */ 
   public abstract ASNReader decodeStructure(IType obj) throws IOException; 
}