org.apache.directory.api.asn1.ber

Class Asn1Decoder

java.lang.Object

org.apache.directory.api.asn1.ber.Asn1Decoder

All Implemented Interfaces:

TLVBerDecoderMBean

public final class Asn1Decoder
extends Object
implements TLVBerDecoderMBean

A BER TLV Tag component decoder. This decoder instantiate a Tag. The tag won't be implementations should not copy the handle to the Tag object delivered but should copy the data if they need it over the long term.

Author:

Apache Directory Project

Field Summary

Fields

Modifier and Type	Field and Description
private static boolean	END This flag is used to indicate that there are no more bytes in the stream
private boolean	indefiniteLengthAllowed Flag that is used to allow/disallow the indefinite form of Length
private static org.slf4j.Logger	LOG The logger
private int	maxLengthLength The maximum number of bytes that could be used to encode the Length
private int	maxTagLength The maximum number of bytes that could be used to encode the Tag
private static boolean	MORE This flag is used to indicate that there are more bytes in the stream

Constructor Summary

Constructors

Modifier	Constructor and Description
private	Asn1Decoder() A public constructor of an Asn1 Decoder.

Method Summary

Modifier and Type	Method and Description
static void	decode(ByteBuffer stream, Asn1Container container) The decoder main function.
private static void	dumpTLVTree(Asn1Container container) Dump the current TLV tree
int	getMaxLengthLength() Get the actual maximum number of bytes that can be used to encode the Length
int	getMaxTagLength() Get the actual maximum number of bytes that can be used to encode the Tag
private static String	getParentLength(TLV tlv) A debug function used to dump the expected length stack.
boolean	isIndefiniteLengthAllowed() Tell if indefinite length form could be used for Length
private static boolean	isTLVDecoded(Asn1Container container) Check if the TLV tree is fully decoded
private static void	treatLengthEndState(Asn1Container container) The Length is fully decoded.
private static boolean	treatLengthPendingState(ByteBuffer stream, Asn1Container container) This function is called when a Length is in the process of being decoded, but the lack of bytes in the buffer stopped the process.
private static boolean	treatLengthStartState(ByteBuffer stream, Asn1Container container) Treat the Length start.
private static boolean	treatTagStartState(ByteBuffer stream, Asn1Container container) Treat the start of a TLV.
private static boolean	treatTLVDoneState(ByteBuffer stream, Asn1Container container) When the TLV has been fully decoded, we have to execute the associated action and switch to the next TLV, which will start with a Tag.
private static boolean	treatValuePendingState(ByteBuffer stream, Asn1Container container) Treat a pending Value when we get more bytes in the buffer.
private static boolean	treatValueStartState(ByteBuffer stream, Asn1Container container) Treat the Value part.

Methods inherited from class java.lang.Object

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

Field Detail

LOG

private static final org.slf4j.Logger LOG

The logger

MORE

private static final boolean MORE

This flag is used to indicate that there are more bytes in the stream

See Also:

Constant Field Values

END

private static final boolean END

This flag is used to indicate that there are no more bytes in the stream

See Also:

Constant Field Values

indefiniteLengthAllowed

private boolean indefiniteLengthAllowed

Flag that is used to allow/disallow the indefinite form of Length

maxLengthLength

private int maxLengthLength

The maximum number of bytes that could be used to encode the Length

maxTagLength

private int maxTagLength

The maximum number of bytes that could be used to encode the Tag

Constructor Detail

Asn1Decoder

private Asn1Decoder()

A public constructor of an Asn1 Decoder.

Method Detail

treatTagStartState

private static boolean treatTagStartState(ByteBuffer stream,
                                          Asn1Container container)

Treat the start of a TLV. It reads the tag and get its value.

Parameters:

stream - The ByteBuffer containing the PDU to decode

container - The container that stores the current state, the result and other informations.

Returns:

true if there are more bytes to read, false otherwise

dumpTLVTree

private static void dumpTLVTree(Asn1Container container)

Dump the current TLV tree

Parameters:

container - The container

isTLVDecoded

private static boolean isTLVDecoded(Asn1Container container)

Check if the TLV tree is fully decoded

Parameters:

container - The container

Returns:

true if the TLV has been decoded

treatLengthStartState

private static boolean treatLengthStartState(ByteBuffer stream,
                                             Asn1Container container)
                                      throws org.apache.directory.api.asn1.DecoderException

Treat the Length start. The tag has been decoded, so we have to deal with the LENGTH, which can be multi-bytes.

Parameters:

stream - The ByteBuffer containing the PDU to decode

container - The container that stores the current state, the result and other informations.

Returns:

true if there are more bytes to read, false otherwise

Throws:

org.apache.directory.api.asn1.DecoderException - Thrown if anything went wrong

treatLengthPendingState

private static boolean treatLengthPendingState(ByteBuffer stream,
                                               Asn1Container container)

This function is called when a Length is in the process of being decoded, but the lack of bytes in the buffer stopped the process.

Parameters:

stream - The ByteBuffer containing the PDU to decode

container - The container that stores the current state, the result and other informations.

Returns:

true if there are more bytes to read, false otherwise

getParentLength

private static String getParentLength(TLV tlv)

A debug function used to dump the expected length stack.

Parameters:

tlv - The current TLV.

Returns:

A string which represent the expected length stack.

treatLengthEndState

private static void treatLengthEndState(Asn1Container container)
                                 throws org.apache.directory.api.asn1.DecoderException

The Length is fully decoded. We have to call an action to check the size.

Parameters:

container - The container that stores the current state, the result and other informations.

Throws:

org.apache.directory.api.asn1.DecoderException - Thrown if anything went wrong

treatValueStartState

private static boolean treatValueStartState(ByteBuffer stream,
                                            Asn1Container container)

Treat the Value part. We will distinguish two cases : - if the Tag is a Primitive one, we will get the value. - if the Tag is a Constructed one, nothing will be done.

Parameters:

stream - The ByteBuffer containing the PDU to decode

container - The container that stores the current state, the result and other informations.

Returns:

true if there are more bytes to read, false otherwise

treatValuePendingState

private static boolean treatValuePendingState(ByteBuffer stream,
                                              Asn1Container container)

Treat a pending Value when we get more bytes in the buffer.

Parameters:

stream - The ByteBuffer containing the PDU to decode

container - The container that stores the current state, the result and other informations.

Returns:

MORE if some bytes remain in the buffer when the value has been decoded, END if whe still need to get some more bytes.

treatTLVDoneState

private static boolean treatTLVDoneState(ByteBuffer stream,
                                         Asn1Container container)
                                  throws org.apache.directory.api.asn1.DecoderException

When the TLV has been fully decoded, we have to execute the associated action and switch to the next TLV, which will start with a Tag.

Parameters:

stream - The ByteBuffer containing the PDU to decode

container - The container that stores the current state, the result and other informations.

Returns:

true if there are more bytes to read, false otherwise

Throws:

org.apache.directory.api.asn1.DecoderException - Thrown if anything went wrong

decode

public static void decode(ByteBuffer stream,
                          Asn1Container container)
                   throws org.apache.directory.api.asn1.DecoderException

The decoder main function. This is where we read bytes from the stream and go through the automaton. It's an inifnite loop which stop when no more bytes are to be read. It can occurs if the ByteBuffer is exhausted or if the PDU has been fully decoded.

Parameters:

stream - The ByteBuffer containing the PDU to decode

container - The container that store the state, the result and other elements.

Throws:

org.apache.directory.api.asn1.DecoderException - Thrown if anything went wrong!

getMaxLengthLength

public int getMaxLengthLength()

Get the actual maximum number of bytes that can be used to encode the Length

Specified by:

getMaxLengthLength in interface TLVBerDecoderMBean

Returns:

The maximum bytes of the Length

getMaxTagLength

public int getMaxTagLength()

Get the actual maximum number of bytes that can be used to encode the Tag

Specified by:

getMaxTagLength in interface TLVBerDecoderMBean

Returns:

The maximum length of the Tag

isIndefiniteLengthAllowed

public boolean isIndefiniteLengthAllowed()

Tell if indefinite length form could be used for Length

Specified by:

isIndefiniteLengthAllowed in interface TLVBerDecoderMBean

Returns:

true if the Indefinite form is allowed