codec.asn1
Class BERDecoder

java.lang.Object
  |
  +--java.io.InputStream
        |
        +--java.io.FilterInputStream
              |
              +--codec.asn1.DERDecoder
                    |
                    +--codec.asn1.BERDecoder

All Implemented Interfaces:

Decoder

public class BERDecoder

extends DERDecoder

Decodes ASN.1/DER encoded types according to the rules set forth in ITU-T Recommendation X.690.

Decoders can be operated in two modi. The first mode just reads any ASN.1 type encountered in a stream and returns the instantiated objects. This mode is used if for instance method readType() is called.

The second mode matches the decoded data against an application-specified ASN.1 structure. Violations of the structure definition causes an exception being thrown.

Version:

"$Id: BERDecoder.java,v 1.3 2001/01/08 18:47:37 vroth Exp $"

Author:

Volker Roth

Fields inherited from class codec.asn1.DERDecoder

debug_, indefinite_, length_, limit_, markpos_, oidbuf_, pos_, primitive_, skip_, tag_, tagclass_

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

BERDecoder(InputStream in)
Creates an instance that reads from the given input stream.

Method Summary

void	readBitString(ASN1BitString t)
void	readCollection(ASN1Collection t)
void	readCollectionOf(ASN1CollectionOf t)
void	readOctetString(ASN1OctetString t)
void	readString(ASN1String t)
void	readTaggedType(ASN1TaggedType t) This method also reads in ASN1Opaque types.
protected void	readTypes(ASN1Collection c) Reads in a sequence of ASN.1 types and stores them in the given collection.

Methods inherited from class codec.asn1.DERDecoder

available, close, getClass, getInputLimit, isDebug, mark, markSupported, match0, match1, match2, read, read, read, readBase128, readBase256, readBoolean, readChoice, readInteger, readNext, readNull, readObjectIdentifier, readReal, readTime, readType, readType, reset, setDebug, setInputLimit, skip, skipNext

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BERDecoder

public BERDecoder(InputStream in)

Creates an instance that reads from the given input stream.

Parameters:

in - The input stream to read from.

Method Detail

readTypes

protected void readTypes(ASN1Collection c)
                  throws ASN1Exception,
                         IOException

Reads in a sequence of ASN.1 types and stores them in the given collection. This method overrides a method in the parent class in order to handle indefinite length encodings as required by BER. Indefinite length encodings are detected by checking the indefinite_ field in this instance. This field is initialized by method readNext() when the identifier and length octets of the next ASN.1 type in the stream are parsed.

Overrides:

readTypes in class DERDecoder

Parameters:

c - The ASN.1 collection in which decoded types are stored.

Throws:

ASN1Exception - if a decoding error occurs.

IOException - if guess what...

readBitString

public void readBitString(ASN1BitString t)
                   throws ASN1Exception,
                          IOException

Overrides:

readBitString in class DERDecoder

readOctetString

public void readOctetString(ASN1OctetString t)
                     throws ASN1Exception,
                            IOException

Overrides:

readOctetString in class DERDecoder

readString

public void readString(ASN1String t)
                throws ASN1Exception,
                       IOException

Overrides:

readString in class DERDecoder

readCollection

public void readCollection(ASN1Collection t)
                    throws ASN1Exception,
                           IOException

Overrides:

readCollection in class DERDecoder

readCollectionOf

public void readCollectionOf(ASN1CollectionOf t)
                      throws ASN1Exception,
                             IOException

Overrides:

readCollectionOf in class DERDecoder

readTaggedType

public void readTaggedType(ASN1TaggedType t)
                    throws ASN1Exception,
                           IOException

Description copied from class: DERDecoder

This method also reads in ASN1Opaque types. Opaque types take on the tag and tag class of the decoded type and read in the contents octets into an OCTET STRING. The opaque type can seamlessly be encoded back into the original encoding. No traversal of the inner structure of the encoded type is required.

Overrides:

readTaggedType in class DERDecoder

Following copied from class: codec.asn1.DERDecoder

Parameters:

t - The ASN1TaggedType or ASN1Opaque to decode.