Tool: add monitor command.

docs/tool.md

@@ -5,14 +5,9 @@ The `Tmds.DBus.Tool` packages extends the dotnet cli to facilitate developing .N
 The tool supports:
 - [codegen](#codegen): generate C# code for consuming D-Bus services.
 - [list](#list): list the available objects, interfaces and services.
+- [monitor](#monitor): prints message bus messages.
 
-The tool can be added by using a `DotNetCliToolReference` in the project file.
-
-```xml
-  <ItemGroup>
-    <DotNetCliToolReference Include="Tmds.DBus.Tool" Version="0.5.0" />
-  </ItemGroup>
-```
+The tool can be installed using `dotnet tool install -g Tmds.DBus.Tool`
 
 Now it can be invoked from the command line:
 ```
@@ -77,4 +72,8 @@ The `list` command can also be used to list interfaces from XML files.
 
 ```
 $ dotnet dbus list interfaces /usr/share/dbus-1/interfaces/*.xml
-```
+```
+
+## monitor
+
+The `monitor` command registers the tool as a bus monitor and prints out the message bus messages.

src/Tmds.DBus.Protocol/Reader.cs

@@ -63,6 +63,12 @@ public bool HasNext(ArrayEnd iterator)
         }
         return true;
     }
+
+    public void SkipTo(ArrayEnd end)
+    {
+        int advance = end.EndOfArray - (int)_reader.Consumed;
+        _reader.Advance(advance);
+    }
 }
 
 public ref struct ArrayEnd

src/Tmds.DBus.Tool/MonitorCommand.cs

@@ -0,0 +1,316 @@
+using System;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.Extensions.CommandLineUtils;
+using Tmds.DBus.Protocol;
+
+namespace Tmds.DBus.Tool;
+
+class MonitorCommand : Command
+{
+    CommandOption _busOption;
+
+    public MonitorCommand(CommandLineApplication parent) :
+        base("monitor", parent)
+    { }
+
+    public override void Configure()
+    {
+        _busOption = AddBusOption();
+    }
+
+    public override void Execute()
+    {
+        var address = ParseBusAddress(_busOption);
+        MonitorBusAsync(address).Wait();
+    }
+
+    private async Task MonitorBusAsync(string address)
+    {
+        StringBuilder sb = new StringBuilder();
+
+        await foreach (DisposableMessage dmsg in Tmds.DBus.Protocol.Connection.MonitorBusAsync(address))
+        {
+            using var _ = dmsg;
+            Message msg = dmsg.Message;
+
+            FormatMessage(sb, msg);
+
+            Print(sb);
+
+            sb.Clear();
+        }
+    }
+
+    static void Print(StringBuilder sb)
+    {
+        foreach (var chunk in sb.GetChunks())
+        {
+            Console.Write(chunk);
+        }
+    }
+
+    private const string ItemPrefix = "- ";
+
+    static void FormatMessage(StringBuilder sb, Message msg)
+    {
+        switch (msg.MessageType)
+        {
+            case MessageType.MethodCall:
+                sb.Append("CAL ");
+                break;
+            case MessageType.MethodReturn:
+                sb.Append("RET ");
+                break;
+            case MessageType.Error:
+                sb.Append("ERR ");
+                break;
+            case MessageType.Signal:
+                sb.Append("SIG ");
+                break;
+            default:
+                throw new ArgumentOutOfRangeException(msg.MessageType.ToString());
+        }
+
+        sb.Append(msg.SenderAsString);
+        sb.Append($"({msg.Serial})");
+        sb.Append("->");
+        if (msg.DestinationIsSet)
+        {
+            sb.Append(msg.DestinationAsString);
+        }
+        if (msg.ReplySerial.HasValue)
+        {
+            sb.Append($"({msg.ReplySerial.Value})");
+        }
+        sb.Append(' ');
+
+        if (msg.PathIsSet)
+        {
+            sb.Append(msg.PathAsString);
+            sb.Append(' ');
+        }
+
+        if (msg.InterfaceIsSet)
+        {
+            sb.Append(msg.InterfaceAsString);
+            sb.Append('.');
+        }
+        if (msg.MemberIsSet)
+        {
+            sb.Append(msg.MemberAsString);
+            sb.Append(' ');
+        }
+
+        if (msg.ErrorNameIsSet)
+        {
+            sb.Append(msg.ErrorNameAsString);
+            sb.Append(' ');
+        }
+
+        if (msg.SignatureIsSet)
+        {
+            sb.Append(msg.SignatureAsString);
+        }
+        sb.AppendLine();
+
+        SignatureReader sigReader = new(msg.Signature);
+        Reader reader = msg.GetBodyReader();
+        while (sigReader.TryRead(out DBusType type, out ReadOnlySpan<byte> innerSignature))
+        {
+            sb.Append("  ");
+            sb.Append(ItemPrefix);
+            AppendValue(sb, indent: 4, ref reader, type, innerSignature);
+        }
+    }
+
+    static void AppendValue(StringBuilder sb, int indent, ref Reader reader, DBusType type, ReadOnlySpan<byte> innerSignature, bool addNewLine = true, bool isDictEntryValue = false)
+    {
+        SignatureReader sigReader;
+        switch (type)
+        {
+            case DBusType.Byte:
+                sb.Append(reader.ReadByte());
+                break;
+            case DBusType.Bool:
+                sb.Append(reader.ReadBool());
+                break;
+            case DBusType.Int16:
+                sb.Append(reader.ReadInt16());
+                break;
+            case DBusType.UInt16:
+                sb.Append(reader.ReadUInt16());
+                break;
+            case DBusType.Int32:
+                sb.Append(reader.ReadInt32());
+                break;
+            case DBusType.UInt32:
+                sb.Append(reader.ReadUInt32());
+                break;
+            case DBusType.Int64:
+                sb.Append(reader.ReadInt64());
+                break;
+            case DBusType.UInt64:
+                sb.Append(reader.ReadUInt64());
+                break;
+            case DBusType.Double:
+                sb.Append(reader.ReadDouble());
+                break;
+            case DBusType.String:
+                sb.Append(reader.ReadString());
+                break;
+            case DBusType.ObjectPath:
+                sb.Append(reader.ReadObjectPath());
+                break;
+            case DBusType.Signature:
+                sb.Append(reader.ReadSignatureAsString());
+                break;
+            case DBusType.UnixFd:
+                sb.Append(reader.ReadHandleRaw());
+                break;
+            case DBusType.Array:
+                sigReader = new(innerSignature);
+                sigReader.TryRead(out type, out innerSignature);
+                bool isDictionary = type == DBusType.DictEntry;
+
+                // Print these types on a single line.
+                bool printSingleLine = type is DBusType.Byte or
+                                                DBusType.Bool or
+                                                DBusType.Int16 or
+                                                DBusType.UInt16 or
+                                                DBusType.Int32 or
+                                                DBusType.UInt32 or
+                                                DBusType.Int64 or
+                                                DBusType.UInt64 or
+                                                DBusType.Double or
+                                                DBusType.UnixFd;
+
+                // Only print first 16 elements of an array.
+                int remaining = isDictionary ? int.MaxValue : 16;
+
+                ArrayEnd arrayEnd = reader.ReadArrayStart(type);
+                bool isEmpty = true;
+                while (reader.HasNext(arrayEnd))
+                {
+                    if (printSingleLine)
+                    {
+                        if (isEmpty) // first
+                        {
+                            sb.Append("[");
+                        }
+                        else
+                        {
+                            sb.Append(", ");
+                        }
+                    }
+                    else
+                    {
+                        if (isEmpty) // first
+                        {
+                            if (isDictEntryValue)
+                            {
+                                sb.AppendLine();
+                                Indent(sb, indent);
+                            }
+                        }
+                        else
+                        {
+                            Indent(sb, indent);
+                        }
+
+                        if (!isDictionary)
+                        {
+                            sb.Append(ItemPrefix);
+                        }
+                    }
+                    isEmpty = false;
+
+                    if (remaining-- == 0)
+                    {
+                        if (printSingleLine)
+                        {
+                            sb.Append("...");
+                        }
+                        else
+                        {
+                            sb.AppendLine("...");
+                        }
+                        reader.SkipTo(arrayEnd);
+                        break;
+                    }
+
+                    AppendValue(sb, isDictionary ? indent : indent + ItemPrefix.Length, ref reader, type, innerSignature, addNewLine: !printSingleLine);
+                }
+                if (isEmpty)
+                {
+                    sb.AppendLine(isDictionary ? "{}" : "[]");
+                }
+                else if (printSingleLine)
+                {
+                    sb.AppendLine("]");
+                }
+
+                addNewLine = false;
+                break;
+            case DBusType.Struct:
+                if (isDictEntryValue)
+                {
+                    sb.AppendLine();
+                    Indent(sb, indent);
+                }
+
+                reader.AlignStruct();
+                sigReader = new(innerSignature);
+
+                bool isFirst = true;
+                while (sigReader.TryRead(out type, out innerSignature))
+                {
+                    if (!isFirst)
+                    {
+                        Indent(sb, indent);
+                    }
+                    isFirst = false;
+
+                    sb.Append(ItemPrefix);
+                    AppendValue(sb, indent + ItemPrefix.Length, ref reader, type, innerSignature);
+                }
+
+                addNewLine = false;
+                break;
+            case DBusType.Variant:
+                innerSignature = reader.ReadSignature().Span;
+                sigReader = new(innerSignature);
+                sigReader.TryRead(out type, out innerSignature);
+                AppendValue(sb, indent, ref reader, type, innerSignature, isDictEntryValue: isDictEntryValue);
+
+                addNewLine = false;
+                break;
+            case DBusType.DictEntry:
+                reader.AlignStruct();
+                sigReader = new(innerSignature);
+
+                sigReader.TryRead(out type, out innerSignature);
+                AppendValue(sb, indent, ref reader, type, innerSignature, addNewLine: false);
+
+                sb.Append(": ");
+
+                sigReader.TryRead(out type, out innerSignature);
+                AppendValue(sb, indent + 2, ref reader, type, innerSignature, isDictEntryValue: true);
+
+                addNewLine = false;
+                break;
+            default:
+                throw new InvalidOperationException();
+        }
+
+        if (addNewLine)
+        {
+            sb.AppendLine();
+        }
+
+        static void Indent(StringBuilder sb, int indent)
+        {
+            sb.Append(' ', indent);
+        }
+    }
+}