@thelarinel/rcon/src/packet.js

A modern NodeJS library for the Source RCON Protocol

/**
 * @typedef {Object} DecodedPacket
 * @property {number} size
 * @property {number} id
 * @property {number} type
 * @property {string} body
 */

/**
 * Encode data to packet buffer
 * @param {number} type
 * @param {number} id
 * @param {string} body
 * @param {('ascii'|'utf8')} [encoding='ascii']
 * @returns {Buffer} Encoded packet buffer
 */
function encode(type, id, body, encoding = 'ascii') {
  const size = Buffer.byteLength(body) + 14, // body size + 10 + 4 (Null)
    buffer = Buffer.alloc(size); // Create a new allocated buffer

  buffer.writeInt32LE(size - 4, 0); // (4 bytes) Size,  All packet size but 'packet size'(4 bytes) field
  buffer.writeInt32LE(id, 4); // (4 bytes) Id,    Unique packet ID
  buffer.writeInt32LE(type, 8); // (4 bytes) Type,  Packet Type (0x03, 0x02 or 0x00)
  buffer.write(body, 12, size - 2, encoding);  // (>= 1 bytes) Body,   Encoded body
  buffer.writeInt16LE(0, size - 2);   // (1 bytes) Null,  Null terminated string

  return buffer;
}

/**
 * Decode packet buffer to data
 * @param {Buffer} buf
 * @param {('ascii'|'utf8')} [encoding='ascii']
 * @returns {DecodedPacket} Decoded packet object
 */
function decode(buf, encoding = 'ascii') {
  return {
    size: buf.readInt32LE(0),
    id: buf.readInt32LE(4),
    type: buf.readInt32LE(8),
    body: buf.toString(encoding, 12, buf.byteLength - 2)
  };
}

module.exports = { encode, decode };