modbus-connect/function-codes/report-slave-id.js

Modbus RTU over Web Serial and Node.js SerialPort

// function-codes/report-slave-id.js

const FUNCTION_CODE = 0x11;
const MIN_RESPONSE_LENGTH = 4;
const HEADER_SIZE = 2;
const SLAVE_ID_OFFSET = 2;
const RUN_STATUS_OFFSET = 3;
const DATA_OFFSET = 4;

/**
 * Строит PDU запроса Report Slave ID (0x11)
 * @returns {Uint8Array}
 */
function buildReportSlaveIdRequest() {
    // Используем ArrayBuffer + DataView для единообразия стиля
    const buffer = new ArrayBuffer(1);
    const view = new DataView(buffer);
    view.setUint8(0, FUNCTION_CODE);
    return new Uint8Array(buffer);
}

/**
 * Разбирает PDU ответа на Report Slave ID
 * @param {Uint8Array} pdu
 * @returns {{ slaveId: number, isRunning: boolean, data: Uint8Array }}
 */
function parseReportSlaveIdResponse(pdu) {
    if (!(pdu instanceof Uint8Array)) {
        throw new TypeError('PDU must be Uint8Array');
    }

    const pduLength = pdu.length;
    
    if (pduLength < MIN_RESPONSE_LENGTH) {
        throw new Error(`PDU too short for Report Slave ID response: expected at least ${MIN_RESPONSE_LENGTH}, got ${pduLength}`);
    }

    if (pdu[0] !== FUNCTION_CODE) {
        throw new Error(`Invalid function code: expected 0x${FUNCTION_CODE.toString(16)}, got 0x${pdu[0].toString(16)}`);
    }

    const byteCount = pdu[1];
    const expectedLength = byteCount + HEADER_SIZE;

    if (pduLength !== expectedLength) {
        throw new Error(`Invalid byte count: expected ${expectedLength}, got ${pduLength}`);
    }

    // Используем оригинальный буфер без копирования данных
    const buffer = pdu.buffer || pdu;
    const byteOffset = pdu.byteOffset || 0;
    
    return {
        slaveId: pdu[SLAVE_ID_OFFSET], // Прямой доступ к Uint8Array быстрее, чем DataView для 8-битных значений
        isRunning: pdu[RUN_STATUS_OFFSET] === 0xFF,
        data: byteCount > 2 
            ? new Uint8Array(buffer, byteOffset + DATA_OFFSET, byteCount - 2) 
            : new Uint8Array(0) // Возвращаем пустой массив если нет данных
    };
}

module.exports = {
    buildReportSlaveIdRequest: buildReportSlaveIdRequest,
    parseReportSlaveIdResponse: parseReportSlaveIdResponse
};