com.sun.management.snmp
Class BerDecoder

java.lang.Object
  com.sun.management.snmp.BerDecoder

public class BerDecoder
extends Object

The BerDecoder class is used for decoding BER-encoded data. A BerDecoder needs to be set up with the byte string containing the encoding. It maintains a current position in the byte string. Methods allows to fetch integer, string, OID, etc., from the current position. After a fetch the current position is moved forward. A fetch throws a BerException if the encoding is not of the expected type.

Since:

Java DMK 5.1

Field Summary

static int	BooleanTag
static int	IntegerTag
static int	NullTag
static int	OctetStringTag
static int	OidTag
static int	SequenceTag

Constructor Summary

BerDecoder(byte[] b)
Constructs a new decoder and attaches it to the specified byte string.

Method Summary

boolean	cannotCloseSequence() Return true if the end of the current sequence is not reached.
void	closeSequence() Close a sequence.
byte[]	fetchAny() Fetch an ANY value.
byte[]	fetchAny(int tag) Fetch an ANY value with a specific tag.
int	fetchInteger() Fetch an integer.
int	fetchInteger(int tag) Fetch an integer with the specified tag.
long	fetchIntegerAsLong() Fetch an integer and return a long value.
long	fetchIntegerAsLong(int tag) Fetch an integer with the specified tag and return a long value.
void	fetchNull() Fetch a NULL value.
void	fetchNull(int tag) Fetch a NULL value with a specified tag.
byte[]	fetchOctetString() Fetch an octet string.
byte[]	fetchOctetString(int tag) Fetch an octet string with a specified tag.
long[]	fetchOid() Fetch an object identifier.
long[]	fetchOid(int tag) Fetch an object identifier with a specified tag.
int	getTag() Get the tag of the data at the current position.
void	openSequence() Fetch a sequence header.
void	openSequence(int tag) Fetch a sequence header with a specific tag.
void	reset()
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

BooleanTag

public static final int BooleanTag

See Also:

Constant Field Values

IntegerTag

public static final int IntegerTag

See Also:

Constant Field Values

OctetStringTag

public static final int OctetStringTag

See Also:

Constant Field Values

NullTag

public static final int NullTag

See Also:

Constant Field Values

OidTag

public static final int OidTag

See Also:

Constant Field Values

SequenceTag

public static final int SequenceTag

See Also:

Constant Field Values

Constructor Detail

BerDecoder

public BerDecoder(byte[] b)

Constructs a new decoder and attaches it to the specified byte string.

Parameters:

b - The byte string containing the encoded data.

Method Detail

reset

public void reset()

fetchInteger

public int fetchInteger()
                 throws BerException

Fetch an integer.

Returns:

The decoded integer.

Throws:

BerException - Current position does not point to an integer.

fetchInteger

public int fetchInteger(int tag)
                 throws BerException

Fetch an integer with the specified tag.

Parameters:

tag - The expected tag.

Returns:

The decoded integer.

Throws:

BerException - Current position does not point to an integer or the tag is not the expected one.

fetchIntegerAsLong

public long fetchIntegerAsLong()
                        throws BerException

Fetch an integer and return a long value.

Returns:

The decoded integer.

Throws:

BerException - Current position does not point to an integer.

fetchIntegerAsLong

public long fetchIntegerAsLong(int tag)
                        throws BerException

Fetch an integer with the specified tag and return a long value.

Parameters:

tag - The expected tag.

Returns:

The decoded integer.

Throws:

BerException - Current position does not point to an integer or the tag is not the expected one.

fetchOctetString

public byte[] fetchOctetString()
                        throws BerException

Fetch an octet string.

Returns:

The decoded string.

Throws:

BerException - Current position does not point to an octet string.

fetchOctetString

public byte[] fetchOctetString(int tag)
                        throws BerException

Fetch an octet string with a specified tag.

Parameters:

tag - The expected tag.

Returns:

The decoded string.

Throws:

BerException - Current position does not point to an octet string or the tag is not the expected one.

fetchOid

public long[] fetchOid()
                throws BerException

Fetch an object identifier.

Returns:

The decoded object identifier as an array of long.

Throws:

BerException

fetchOid

public long[] fetchOid(int tag)
                throws BerException

Fetch an object identifier with a specified tag.

Parameters:

tag - The expected tag.

Returns:

The decoded object identifier as an array of long.

Throws:

BerException - Current position does not point to an oid or the tag is not the expected one.

fetchNull

public void fetchNull()
               throws BerException

Fetch a NULL value.

Throws:

BerException - Current position does not point to NULL value.

fetchNull

public void fetchNull(int tag)
               throws BerException

Fetch a NULL value with a specified tag.

Parameters:

tag - The expected tag.

Throws:

BerException - Current position does not point to NULL value or the tag is not the expected one.

fetchAny

public byte[] fetchAny()
                throws BerException

Fetch an ANY value. In fact, this method does not decode anything it simply returns the next TLV as an array of bytes.

Returns:

The TLV as a byte array.

Throws:

BerException - The next TLV is really badly encoded...

fetchAny

public byte[] fetchAny(int tag)
                throws BerException

Fetch an ANY value with a specific tag.

Parameters:

tag - The expected tag.

Returns:

The TLV as a byte array.

Throws:

BerException - The next TLV is really badly encoded...

openSequence

public void openSequence()
                  throws BerException

Fetch a sequence header. The decoder computes the end position of the sequence and push it on its stack.

Throws:

BerException - Current position does not point to a sequence header.

openSequence

public void openSequence(int tag)
                  throws BerException

Fetch a sequence header with a specific tag.

Parameters:

tag - The expected tag.

Throws:

BerException - Current position does not point to a sequence header or the tag is not the expected one.

closeSequence

public void closeSequence()
                   throws BerException

Close a sequence. The decode pull the stack and verifies that the current position matches with the calculated end of the sequence. If not it throws an exception.

Throws:

BerException - The sequence is not expected to finish here.

cannotCloseSequence

public boolean cannotCloseSequence()

Return true if the end of the current sequence is not reached. When this method returns false, closeSequence can (and must) be invoked.

Returns:

true if there is still some data in the sequence.

getTag

public int getTag()
           throws BerException

Get the tag of the data at the current position. Current position is unchanged.

Returns:

The next tag.

Throws:

BerException

toString

public String toString()

Overrides:

toString in class Object