dis-codec

TypeScript encode/decode library for Distributed Interactive Simulation (DIS) with wire format aligned to IEEE 1278.1 (DIS application protocols).

This project focuses on a practical subset of DIS 7 PDUs (see list below). It is not an implementation of the full DIS specification.

Install

npm install @its-c10/dis-codec

Usage

Encode a PDU and get bytes for UDP:

import { BinaryWriter, dis7 } from "@its-c10/dis-codec";

const writer = new BinaryWriter();
dis7.encodeCreateEntityPdu(writer, {
  header: {
    protocolVersion: dis7.PROTOCOL_VERSION,
    exerciseId: 1,
    pduType: dis7.PDU_TYPE_CREATE_ENTITY,
    protocolFamily: dis7.PROTOCOL_FAMILY_SIMULATION_MANAGEMENT,
    timestamp: 0,
    pduStatus: 0,
    padding: 0,
  },
  originatingId: { simulationAddress: { site: 1, application: 2 }, entity: 10 },
  receivingId: { simulationAddress: { site: 0, application: 0 }, entity: 0 },
  requestId: 1,
});

const bytes = new Uint8Array(writer.toArrayBuffer());
// Send bytes over UDP

Decode a PDU from received bytes:

import { BinaryReader, dis7 } from "@its-c10/dis-codec";

const reader = new BinaryReader(udpPacketBuffer);
const pdu = dis7.decodeEntityStatePdu(reader);
// Use pdu.entityId, pdu.entityLocation, etc.

Switch on PDU type:

const reader = new BinaryReader(buffer);
const header = dis7.decodePduHeader(reader);
reader.setOffset(0); // rewind to decode full PDU

if (header.pduType === dis7.PDU_TYPE_ENTITY_STATE) {
  const pdu = dis7.decodeEntityStatePdu(reader);
  // ...
} else if (header.pduType === dis7.PDU_TYPE_ELECTROMAGNETIC_EMISSION) {
  const pdu = dis7.decodeElectromagneticEmissionPdu(reader);
  // ...
}

DIS 7 PDUs

| PDU | Encode / Decode | Notes | |-----|-----------------|-------| | Entity State | encodeEntityStatePdu / decodeEntityStatePdu | Variable length | | Create Entity | encodeCreateEntityPdu / decodeCreateEntityPdu | 28 bytes | | Remove Entity | encodeRemoveEntityPdu / decodeRemoveEntityPdu | 28 bytes | | Start/Resume | encodeStartResumePdu / decodeStartResumePdu | 44 bytes | | Stop/Freeze | encodeStopFreezePdu / decodeStopFreezePdu | 40 bytes | | Electromagnetic Emission | encodeElectromagneticEmissionPdu / decodeElectromagneticEmissionPdu | Variable length | | Transmitter | encodeTransmitterPdu / decodeTransmitterPdu | Variable length | | Point Object State | encodePointObjectStatePdu / decodePointObjectStatePdu | 88 bytes |

Constants for PDU types, protocol families, and fixed lengths are available on dis7 (for example dis7.PDU_TYPE_ENTITY_STATE and dis7.CREATE_ENTITY_PDU_LENGTH).

Data length fields

PDUs such as Electromagnetic Emission and Transmitter include length-in-octets fields (beamDataLength, systemDataLength, recordLength, lengthOfModulationParameters, etc.). The PDU header length field is also in this category. These are computed and written automatically during encode—you do not need to set them. The encoder writes a placeholder, encodes the payload, then patches the correct byte counts retroactively. When decoding, these fields are read from the wire and included in the returned object.

Requirements

• ES2020+ (Node or browser)
• TypeScript types included

License

MIT