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org.yamcs.simulation.simulator.CCSDSPacket Maven / Gradle / Ivy
package org.yamcs.simulation.simulator;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.BufferOverflowException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.HashMap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.yamcs.utils.TimeEncoding;
public class CCSDSPacket {
/*
primary header (6 bytes):
3 bit = version
1 bit = type (0 = system packet, 1 = payload packet)
1 bit = 2nd header present
11 bit = apid
2 bit = grouping, 01 = first, 00 = cont, 10 = last packet of group
14 bit = seq
16 bit = packet length (excluding primary header) minus 1
secondary header (10 bytes):
32 bit = coarse time (seconds since 1970)
8 bit = fine time
2 bits = time id (see constants)
1 bit = checksum present (2 bytes after user data)
5 bits = packet type (see constants)
32 bit = packet id
*/
final byte SH_TIME_ID_NO_TIME_FIELD = 0;
final byte SH_TIME_ID_TIME_OF_PACKET_GENERATION = 1;
final byte SH_TIME_ID_TIME_TAG = 2;
final byte SH_TIME_ID_UNDEFINED = 3;
// Packet types
final static byte SH_PKT_TYPE_CCSDS_CCSDS_PAYLOAD_HK_PACKET = 5;
final static byte SH_PKT_TYPE_CCSDS_PAYLOAD_COMMAND_PACKET = 10;
final static byte SH_PKT_TYPE_CCSDS_MEMORY_LOAD_PACKET = 11;
final static byte SH_PKT_TYPE_CCSDS_RESPONSE_PACKET = 12;
protected static HashMap seqMap = new HashMap<>(2); // apid -> seq
protected ByteBuffer buffer;
// Header Attributes
private int apid, packetid, packetType, seq;
private long timeMillis; //yamcs time
private short w;
private Logger log = LoggerFactory.getLogger(this.getClass().getName());
private boolean checksumPresent;
public CCSDSPacket(ByteBuffer buffer) {
this.buffer = buffer;
apid = buffer.getShort(0) & 0x07ff;
seq = buffer.getShort(2) & 0x3fff;
packetType = (byte) (buffer.get(11) & 0x0F); // get the packet type
packetid = buffer.getInt(12);
timeMillis = TimeEncoding.fromGpsCcsdsTime(buffer.getInt(6), buffer.get(10));
}
public CCSDSPacket(int userDataLength, int packetid) {
this(userDataLength, packetid, true);
}
public CCSDSPacket(int userDataLength, int packetid, boolean checksumPresent) {
this(userDataLength, SH_PKT_TYPE_CCSDS_CCSDS_PAYLOAD_HK_PACKET, packetid, checksumPresent);
}
public CCSDSPacket(int userDataLength, int packetType, int packetid) {
this(userDataLength, packetType, packetid, true);
}
public CCSDSPacket(int userDataLength, int packetType, int packetid, boolean checksumPresent) {
apid = 1;
seq = 0;
timeMillis = TimeEncoding.getWallclockTime(); // gps time as of 2017
int dl = userDataLength + 16;
if (checksumPresent) {
dl += 2;
if ((dl & 1) == 1) { // need an even number of bytes to compute a checksum
dl += 1;
}
}
buffer = ByteBuffer.allocate(dl);
buffer.order(ByteOrder.BIG_ENDIAN);
this.packetType = packetType;
this.packetid = packetid;
this.checksumPresent = checksumPresent;
putHeader();
}
public void setTime(long instant) {
timeMillis = instant;
putHeader();
}
public void setApid(int apid) {
this.apid = apid;
putHeader();
}
public ByteBuffer getUserDataBuffer() {
buffer.position(16);
return buffer.slice();
}
public void appendUserDataBuffer(byte[] userData) {
this.buffer = ByteBuffer.allocate(this.buffer.capacity() + userData.length).put(this.buffer.array())
.put(userData);
updatePacketSize();
}
public void setUserDataBuffer(ByteBuffer buffer) {
this.buffer = ByteBuffer.allocate(this.buffer.capacity())
.put(this.buffer).put(buffer);
updatePacketSize();
}
public int getPacketId() {
return packetid;
}
public void setPacketId(int packetId) {
this.packetid = packetId;
}
public int getPacketType() {
return packetType;
}
public int getSeq() {
return seq;
}
public void writeTo(OutputStream os) throws IOException {
try {
if (buffer.hasArray()) {
os.write(buffer.array());
// System.out.println(HexDump.dumpHexString(buffer.array()));
// System.out.println("sent " + this + " " + payload);
}
} catch (BufferOverflowException e) {
log.error("overflow while sending " + this, e);
}
}
@Override
public String toString() {
StringBuffer sb = new StringBuffer();
sb.append("apid: " + apid + "\n");
sb.append("seq: " + seq + "\n");
sb.append("packetId: " + packetid + "\n");
sb.append("packetType: " + packetType + "\n");
sb.append("time: " + timeMillis);
sb.append("\n");
return sb.toString();
}
private void updatePacketSize() {
// update the packet size information in the secondary header
this.buffer.putShort(4, (short) (this.buffer.capacity() - 7));
}
private void putHeader() {
// primary
w = (short) ((1 << 11) | apid); // 2nd header present
buffer.putShort(0, w);
seq = getSeq(apid);
buffer.putShort(2, (short) (seq & 0x3fff));
buffer.putShort(4, (short) (buffer.capacity() - 7)); // secondary
long gpsMillis = TimeEncoding.toGpsTimeMillisec(timeMillis);
buffer.putInt(6, (int) (gpsMillis / 1000));
buffer.put(10, (byte) ((gpsMillis % 1000) * 256 / 1000));
// original version with checksum;
int checksum = checksumPresent ? 1 : 0;
buffer.put(11, (byte) ((SH_TIME_ID_TIME_OF_PACKET_GENERATION << 6) | (checksum << 5) | packetType)); // checksum
buffer.putInt(12, packetid);
// describePacketHeader();
}
private static int getSeq(int apid) {
int seq = seqMap.containsKey(apid) ? seqMap.get(apid) : 0;
seqMap.put(apid, (seq + 1) & 0x3FFF);
return seq;
}
public void fillChecksum() {
if (checksumPresent) {
int checksum = 0;
for (int i = 0; i < buffer.limit() - 2; i += 2) {
checksum += buffer.getShort(i);
}
buffer.putShort(buffer.limit() - 2, (short) checksum);
}
}
public byte[] toByteArray() {
return buffer.array();
}
}
