Package org.yamcs.tctm.ccsds

Class PacketDecoder

java.lang.Object

org.yamcs.tctm.ccsds.PacketDecoder

public class PacketDecoder
extends Object

Receives data chunk by chunk and assembles it into packets. Two types of packets are supported:

Space Packet Protocol CCSDS 133.0-B-1 September 2003.

The first 3 bits of these packets are 000.

The header is 6 bytes and the last two bytes of the header represent the size of the packet (including the header) - 7.

The minimum packet length is 7 bytes.

Encapsulation Service. CCSDS 133.1-B-2. October 2009.

The first 3 bits of these packets are 111.

The minimum packet length is 1 byte.

Depending on the last 2 bits of the first byte, the size of the header can be 1,2,4 or 8 bytes with the length of the packet read from the last 0,1,2 or 4 header bytes respectively

The two types can be both present on the same stream.

The objects of this class can processes one "stream" at a time and they are not thread safe!

Constructor Summary

Constructors

Constructor	Description
PacketDecoder(int maxPacketLength, Consumer<byte[]> consumer)

Method Summary

Modifier and Type	Method	Description
boolean	hasIncompletePacket()
void	process(byte[] data, int offset, int length)
void	reset()	Removes a partial packet if any
boolean	skipIdlePackets()
void	skipIdlePackets(boolean skipIdlePackets)	Skip or not the idle packets.
boolean	stripEncapsulationHeader()
void	stripEncapsulationHeader(boolean stripEncapsulationHeader)	If set to true, the encapsulation header will be stripped out.

Methods inherited from class java.lang.Object

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

Constructor Detail

PacketDecoder

public PacketDecoder(int maxPacketLength,
                     Consumer<byte[]> consumer)

Method Detail

process

public void process(byte[] data,
                    int offset,
                    int length)
             throws TcTmException

Throws:

TcTmException

reset

public void reset()

Removes a partial packet if any

hasIncompletePacket

public boolean hasIncompletePacket()

Returns:

true of the decoder is in the middle of a packet decoding

skipIdlePackets

public boolean skipIdlePackets()

Returns:

true of the idle packets are skipped (i.e. not sent to the consumer)

skipIdlePackets

public void skipIdlePackets(boolean skipIdlePackets)

Skip or not the idle packets. If true (default), the idle packets are not sent to the consumer.

Parameters:

skipIdlePackets -

stripEncapsulationHeader

public boolean stripEncapsulationHeader()

Returns:

true if the header of the encapsulated packets will be stripped out.

stripEncapsulationHeader

public void stripEncapsulationHeader(boolean stripEncapsulationHeader)

If set to true, the encapsulation header will be stripped out. This means:

• the Protocol ID information will be lost.
• an empty array buffer will be delivered for the one byte packets (or any other packet of size 0)

Parameters:

stripEncapsulationHeader -