OnlineMonitorSystem/NModbus/Message/ReadCoilsInputsRequest.cs

using System;
using System.IO;
using System.Net;

namespace NModbus.Message
{
    public class ReadCoilsInputsRequest : AbstractModbusMessage, IModbusRequest
    {
        public ReadCoilsInputsRequest()
        {
        }

        public ReadCoilsInputsRequest(byte functionCode, byte slaveAddress, ushort startAddress, ushort numberOfPoints)
            : base(slaveAddress, functionCode)
        {
            StartAddress = startAddress;
            NumberOfPoints = numberOfPoints;
        }

        public ushort StartAddress
        {
            get => MessageImpl.StartAddress.Value;
            set => MessageImpl.StartAddress = value;
        }

        public override int MinimumFrameSize => 6;

        public ushort NumberOfPoints
        {
            get => MessageImpl.NumberOfPoints.Value;

            set
            {
                if (value > Modbus.MaximumDiscreteRequestResponseSize)
                {
                    string msg = $"Maximum amount of data {Modbus.MaximumDiscreteRequestResponseSize} coils.";
                    throw new ArgumentOutOfRangeException(nameof(NumberOfPoints), msg);
                }

                MessageImpl.NumberOfPoints = value;
            }
        }

        public override string ToString()
        {
            string msg = $"Read {NumberOfPoints} {(FunctionCode == ModbusFunctionCodes.ReadCoils ? "coils" : "inputs")} starting at address {StartAddress}.";
            return msg;
        }

        public void ValidateResponse(IModbusMessage response)
        {
            var typedResponse = (ReadCoilsInputsResponse)response;

            // best effort validation - the same response for a request for 1 vs 6 coils (same byte count) will pass validation.
            var expectedByteCount = (NumberOfPoints + 7) / 8;

            if (expectedByteCount != typedResponse.ByteCount)
            {
                string msg = $"Unexpected byte count. Expected {expectedByteCount}, received {typedResponse.ByteCount}.";
                throw new IOException(msg);
            }
        }

        protected override void InitializeUnique(byte[] frame)
        {
            StartAddress = (ushort)IPAddress.NetworkToHostOrder(BitConverter.ToInt16(frame, 2));
            NumberOfPoints = (ushort)IPAddress.NetworkToHostOrder(BitConverter.ToInt16(frame, 4));
        }
    }
}