codec.asn1
Class AbstractEncoder

java.lang.Object
  |
  +--java.io.OutputStream
        |
        +--java.io.FilterOutputStream
              |
              +--codec.asn1.AbstractEncoder

All Implemented Interfaces:

Encoder

Direct Known Subclasses:

DEREncoder

public abstract class AbstractEncoder

extends FilterOutputStream

implements Encoder

Version:

"$Id: AbstractEncoder.java,v 1.3 2005/03/22 15:55:36 flautens Exp $"

Author:

Volker Roth

Fields inherited from class java.io.FilterOutputStream

out

Constructor Summary

AbstractEncoder(OutputStream out)
Creates an encoder that writes its output to the given output stream.

Method Summary

protected int	getHeaderLength(int tag, int len) This method computes the number of octets needed to encode the identifier and length octets of the ASN.1 type with the given tag and contents length.
protected int	significantBits(int n) Counts the number of significant bits in the given integer.
protected void	writeBase128(int n) Writes the given integer to the output in base 128 representation with bit 7 of all octets except the last one being set to "1".
protected void	writeBase256(int n) Writes the given integer to the output in base 256 with the minimal number of octets.
protected void	writeHeader(int tag, int cls, boolean prim, int len) This method encodes identifier and length octets.
void	writeType(ASN1Type t)

Methods inherited from class java.io.FilterOutputStream

close, flush, write, write, write

Methods inherited from class java.lang.Object

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

Methods inherited from interface codec.asn1.Encoder

writeBitString, writeBoolean, writeCollection, writeInteger, writeNull, writeObjectIdentifier, writeOctetString, writeReal, writeString, writeTaggedType, writeTime, writeTypeIdentifier

Constructor Detail

AbstractEncoder

public AbstractEncoder(OutputStream out)

Creates an encoder that writes its output to the given output stream.

Parameters:

out - The output stream to which the encoded ASN.1 objects are written.

Method Detail

writeType

public void writeType(ASN1Type t)
               throws ASN1Exception,
                      IOException

Specified by:

writeType in interface Encoder

writeHeader

protected void writeHeader(int tag,
                           int cls,
                           boolean prim,
                           int len)
                    throws IOException

This method encodes identifier and length octets. The given length can be negative in which case 0x80 is written to indicate INDEFINITE LENGTH encoding. Please note that this is appropriate only for a BER encoding or CER encoding (ITU-T Recommenation X.690). Encoders are responsible for writing the end of code octets 0x00 0x00 after encoding the content octets.

Parameters:

tag - The ASN.1 tag

cls - The ASN.1 tag class.

prim - true if the encoding is PRIMITIVE and false if it is CONSTRUCTED.

len - The number of content octets or -1 to indicate INDEFINITE LENGTH encoding.

getHeaderLength

protected int getHeaderLength(int tag,
                              int len)

This method computes the number of octets needed to encode the identifier and length octets of the ASN.1 type with the given tag and contents length. The given length can be negative in which case INDEFINITE LENGTH encoding is assumed.

Parameters:

tag - The ASN.1 tag.

len - The number of contents octets of the ASN.1 type with the given tag and length.

Returns:

The number of octets required for encoding the identifier and length octets.

writeBase128

protected void writeBase128(int n)
                     throws IOException

Writes the given integer to the output in base 128 representation with bit 7 of all octets except the last one being set to "1". The minimum number of octets necessary is used.

Parameters:

n - The integer to be written to the output.

Throws:

IOException - Thrown by the underlying output stream.

writeBase256

protected void writeBase256(int n)
                     throws IOException

Writes the given integer to the output in base 256 with the minimal number of octets.

Parameters:

n - The integer to be written to the output.

Throws:

IOException - Thrown by the underlying output stream.

significantBits

protected int significantBits(int n)

Counts the number of significant bits in the given integer. There is always at least one significant bit.

Parameters:

n - The integer.

Returns:

The number of significant bits in the given integer.