Only update console, when content changes

Sharp7.Monitor/CustomStyles.cs

@@ -1,5 +1,7 @@
 using Spectre.Console;
 
+namespace Sharp7.Monitor;
+
 public static class CustomStyles
 {
     public static Style Error { get; } = new Style(foreground: Color.Red);

Sharp7.Monitor/ReadPlcCommand.cs

@@ -1,20 +1,20 @@
-using System.Collections;
+using System.ComponentModel;
-using System.ComponentModel;
 using System.Reactive.Linq;
 using System.Reactive.Threading.Tasks;
 using JetBrains.Annotations;
-using Sharp7.Read;
 using Sharp7.Rx;
 using Sharp7.Rx.Enums;
 using Spectre.Console;
 using Spectre.Console.Cli;
 using Spectre.Console.Rendering;
 
+namespace Sharp7.Monitor;
+
 internal sealed class ReadPlcCommand : AsyncCommand<ReadPlcCommand.Settings>
 {
     public override async Task<int> ExecuteAsync(CommandContext context, Settings settings)
     {
-        var token = (CancellationToken)(context.Data ?? CancellationToken.None);
+        var token = (CancellationToken) (context.Data ?? CancellationToken.None);
 
         try
         {
@@ -27,120 +27,121 @@ internal sealed class ReadPlcCommand : AsyncCommand<ReadPlcCommand.Settings>
         return 0;
     }
 
-    private static IRenderable FormatCellData(VariableRecord record)
+    private static IRenderable FormatCellData(object value)
     {
-        return record.Value switch
+        return value switch
         {
             IRenderable renderable => renderable,
             Exception ex => new Text(ex.Message, CustomStyles.Error),
             byte[] byteArray => new Text(string.Join(" ", byteArray.Select(b => $"0x{b:X2}")), CustomStyles.Hex),
             byte => FormatNo(),
-            short =>FormatNo(),
+            short => FormatNo(),
-            ushort =>FormatNo(),
+            ushort => FormatNo(),
-            int =>FormatNo(),
+            int => FormatNo(),
-            uint =>FormatNo(),
+            uint => FormatNo(),
-            long =>FormatNo(),
+            long => FormatNo(),
-            ulong =>FormatNo(),
+            ulong => FormatNo(),
 
-            _ => new Text(record.Value.ToString() ?? "")
+            _ => new Text(value.ToString() ?? "")
         };
 
-        Markup FormatNo() => new($"[blue]0x{record.Value:X2}[/]  {record.Value}");
+        Markup FormatNo() => new($"[blue]0x{value:X2}[/]  {value}");
     }
 
     private static async Task RunProgram(Settings settings, CancellationToken token)
-{
-    AnsiConsole.MarkupLine($"Connecting to plc [green]{settings.PlcIp}[/], CPU [green]{settings.CpuMpiAddress}[/], rack [green]{settings.RackNumber}[/]. ");
-    AnsiConsole.MarkupLine("[gray]Press Ctrl + C to cancel.[/]");
-
-    using var plc = new Sharp7Plc(settings.PlcIp, settings.RackNumber, settings.CpuMpiAddress);
-
-    await plc.TriggerConnection(token);
-
-    // Connect
-    await AnsiConsole.Status()
-        .Spinner(Spinner.Known.BouncingBar)
-        .StartAsync("Connecting...", async ctx =>
-        {
-            var lastState = ConnectionState.Initial;
-            ctx.Status(lastState.ToString());
-
-            while (!token.IsCancellationRequested)
-            {
-                var state = await plc.ConnectionState.FirstAsync(s => s != lastState).ToTask(token);
-                ctx.Status(state.ToString());
-
-                if (state == ConnectionState.Connected)
-                    return;
-            }
-        });
-
-    token.ThrowIfCancellationRequested();
-
-
-    using var variableContainer = VariableContainer.Initialize(plc, settings.Variables);
-
-    // Create a table
-    var table = new Table
     {
-        Border = TableBorder.Rounded,
+        AnsiConsole.MarkupLine($"Connecting to plc [green]{settings.PlcIp}[/], CPU [green]{settings.CpuMpiAddress}[/], rack [green]{settings.RackNumber}[/]. ");
-        BorderStyle = new Style(foreground: Color.DarkGreen)
+        AnsiConsole.MarkupLine("[gray]Press Ctrl + C to cancel.[/]");
-    };
 
-    table.AddColumn("Variable");
+        using var plc = new Sharp7Plc(settings.PlcIp, settings.RackNumber, settings.CpuMpiAddress);
-    table.AddColumn("Value");
 
-    foreach (var record in variableContainer.VariableRecords)
+        await plc.TriggerConnection(token);
-        table.AddRow(record.Address, "[gray]init[/]");
 
-    await AnsiConsole.Live(table)
+        // Connect
-        .StartAsync(async ctx =>
+        await AnsiConsole.Status()
-        {
+            .Spinner(Spinner.Known.BouncingBar)
-            while (!token.IsCancellationRequested)
+            .StartAsync("Connecting...", async ctx =>
             {
-                foreach (var record in variableContainer.VariableRecords)
+                var lastState = ConnectionState.Initial;
-                    table.Rows.Update(
+                ctx.Status(lastState.ToString());
-                        record.RowIdx, 1,
-                        FormatCellData(record)
-                    );
 
-                ctx.Refresh();
+                while (!token.IsCancellationRequested)
+                {
+                    var state = await plc.ConnectionState.FirstAsync(s => s != lastState).ToTask(token);
+                    ctx.Status(state.ToString());
 
-                await Task.Delay(100, token);
+                    if (state == ConnectionState.Connected)
-            }
+                        return;
-        });
+                }
-}
+            });
 
-[NoReorder]
+        token.ThrowIfCancellationRequested();
-public sealed class Settings : CommandSettings
-{
-    [Description("IP address of S7")]
-    [CommandArgument(0, "<IP address>")]
-    public required string PlcIp { get; init; }
 
-    [CommandArgument(1, "[variables]")]
-    [Description("Variables to read from S7, like Db200.Int4.\r\nFor format description see https://github.com/evopro-ag/Sharp7Reactive.")]
-    public required string[] Variables { get; init; }
 
-    [CommandOption("-c|--cpu")]
+        using var variableContainer = VariableContainer.Initialize(plc, settings.Variables);
-    [Description("CPU MPI address of S7 instance.\r\nSee https://github.com/fbarresi/Sharp7/wiki/Connection#rack-and-slot.\r\n")]
-    [DefaultValue(0)]
-    public int CpuMpiAddress { get; init; }
 
-    [CommandOption("-r|--rack")]
+        // Create a table
-    [Description("Rack number of S7 instance.\r\nSee https://github.com/fbarresi/Sharp7/wiki/Connection#rack-and-slot.\r\n")]
+        var table = new Table
-    [DefaultValue(0)]
+        {
-    public int RackNumber { get; init; }
+            Border = TableBorder.Rounded,
+            BorderStyle = new Style(foreground: Color.DarkGreen)
+        };
 
-    public override ValidationResult Validate()
+        table.AddColumn("Variable");
+        table.AddColumn("Value");
+
+        foreach (var record in variableContainer.VariableRecords)
+            table.AddRow(record.Address, "[gray]init[/]");
+
+        await AnsiConsole.Live(table)
+            .StartAsync(async ctx =>
+            {
+                while (!token.IsCancellationRequested)
+                {
+                    foreach (var record in variableContainer.VariableRecords)
+                        if (record.HasUpdate(out var value))
+                            table.Rows.Update(
+                                record.RowIdx, 1,
+                                FormatCellData(value)
+                            );
+
+                    ctx.Refresh();
+
+                    await Task.Delay(100, token);
+                }
+            });
+    }
+
+    [NoReorder]
+    public sealed class Settings : CommandSettings
     {
-        if (!StringHelper.IsValidIp4(PlcIp))
+        [Description("IP address of S7")]
-            return ValidationResult.Error($"\"{PlcIp}\" is not a valid IP V4 address");
+        [CommandArgument(0, "<IP address>")]
+        public required string PlcIp { get; init; }
 
-        if (Variables == null || Variables.Length == 0)
+        [CommandArgument(1, "[variables]")]
-            return ValidationResult.Error("Please supply at least one variable to read");
+        [Description("Variables to read from S7, like Db200.Int4.\r\nFor format description see https://github.com/evopro-ag/Sharp7Reactive.")]
+        public required string[] Variables { get; init; }
 
-        return ValidationResult.Success();
+        [CommandOption("-c|--cpu")]
+        [Description("CPU MPI address of S7 instance.\r\nSee https://github.com/fbarresi/Sharp7/wiki/Connection#rack-and-slot.\r\n")]
+        [DefaultValue(0)]
+        public int CpuMpiAddress { get; init; }
+
+        [CommandOption("-r|--rack")]
+        [Description("Rack number of S7 instance.\r\nSee https://github.com/fbarresi/Sharp7/wiki/Connection#rack-and-slot.\r\n")]
+        [DefaultValue(0)]
+        public int RackNumber { get; init; }
+
+        public override ValidationResult Validate()
+        {
+            if (!StringHelper.IsValidIp4(PlcIp))
+                return ValidationResult.Error($"\"{PlcIp}\" is not a valid IP V4 address");
+
+            if (Variables == null || Variables.Length == 0)
+                return ValidationResult.Error("Please supply at least one variable to read");
+
+            return ValidationResult.Success();
+        }
     }
 }
-}

Sharp7.Monitor/StringHelper.cs

@@ -1,4 +1,4 @@
-namespace Sharp7.Read;
+namespace Sharp7.Monitor;
 
 public static class StringHelper
 {

Sharp7.Monitor/VariableContainer.cs

@@ -3,6 +3,8 @@ using Sharp7.Rx.Enums;
 using Sharp7.Rx.Interfaces;
 using Spectre.Console;
 
+namespace Sharp7.Monitor;
+
 public class VariableContainer : IDisposable
 {
     private readonly IDisposable subscriptions;

Sharp7.Monitor/VariableRecord.cs

@@ -1,6 +1,55 @@
-public class VariableRecord
+using System.Diagnostics.CodeAnalysis;
+
+namespace Sharp7.Monitor;
+
+public class VariableRecord
 {
+    private object value = new();
+    private int valueUpdated;
     public required string Address { get; init; }
     public required int RowIdx { get; init; }
-    public object Value { get; set; }
+
+    public object Value
+    {
+        get => value;
+        set
+        {
+            if (!IsEquivalent(this.value, value))
+            {
+                this.value = value;
+                valueUpdated = 1;
+            }
+        }
+    }
+
+    private bool IsEquivalent(object oldValue, object newValue)
+    {
+        // Special treatmant for byte arrays
+        if (oldValue is byte[] oldArray && newValue is byte[] newArray)
+        {
+            if (oldArray.Length != newArray.Length) return false;
+
+            for (var i = 0; i < oldArray.Length; i++)
+                if (oldArray[i] != newArray[i]) return false;
+
+            return true;
+        }
+
+        // all other types read from PLC have value compare semantics. 
+        return oldValue == newValue;
+    }
+
+    public bool HasUpdate([NotNullWhen(true)] out object? newValue)
+    {
+        if (Interlocked.Exchange(ref valueUpdated, 0) == 1)
+        {
+            newValue = value;
+            return true;
+        }
+        else
+        {
+            newValue = null;
+            return false;
+        }
+    }
 }