Feature: introduced IEventBus, removed high-overhead event generation

ImageMap was generating high-frequency events, which were slowing down Reko's GUI. By changing the event firing to only happen when Procedures are discovered, scanner execution time was reduced by 40%.

.ci/linux_arm64/Dockerfile

@@ -5,4 +5,4 @@ RUN apt-get update && \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/* \
     && dotnet nuget locals all --clear
-    # reserved for cache eviction: 0
+    # reserved for cache eviction: 1

src/Arch/X86/Analysis/FstswAnalysis.cs

@@ -81,10 +81,10 @@ namespace Reko.Arch.X86.Analysis
     public class FstswAnalysis : IAnalysis<SsaState>
     {
         private readonly IReadOnlyProgram program;
-        private readonly DecompilerEventListener listener;
+        private readonly IEventListener listener;
         private SsaState ssa;
 
-        public FstswAnalysis(IReadOnlyProgram program, DecompilerEventListener listener)
+        public FstswAnalysis(IReadOnlyProgram program, IEventListener listener)
         {
             this.program = program;
             this.ssa = default!;

src/Core/AddressContext.cs

@@ -30,19 +30,19 @@ public class AddressContext
     {
         private readonly Program program;
         private readonly Address addr;
-        private readonly DecompilerEventListener decompilerEventListener;
+        private readonly IEventListener eventListener;
 
-        public AddressContext(Program program, Address addr, DecompilerEventListener decompilerEventListener)
+        public AddressContext(Program program, Address addr, IEventListener eventListener)
         {
             this.program = program;
             this.addr = addr;
-            this.decompilerEventListener = decompilerEventListener;
+            this.eventListener = eventListener;
         }
 
         public void Warn(string format, params object [] args)
         {
-            decompilerEventListener.Warn(
-               decompilerEventListener.CreateAddressNavigator(program, addr),
+            eventListener.Warn(
+               eventListener.CreateAddressNavigator(program, addr),
                string.Format(format, args));
         }
     }

src/Core/Configuration/PlatformDefinition.cs

@@ -80,7 +80,7 @@ public void LoadSettingsFromConfiguration(IServiceProvider services, Platform pl
             {
                 var cfgSvc = services.RequireService<IConfigurationService>();
                 var fsSvc = services.RequireService<IFileSystemService>();
-                var listener = services.RequireService<DecompilerEventListener>();
+                var listener = services.RequireService<IEventListener>();
                 try
                 {
                     var filePath = cfgSvc.GetInstallationRelativePath(MemoryMapFile!);

src/Core/Configuration/RekoConfigurationService.cs

@@ -436,8 +436,8 @@ public virtual ICollection<RawFileDefinition> GetRawFiles()
             var options = new Dictionary<string, object>();
             if (model is null)
             {
-                var listener = services.GetService<DecompilerEventListener>() ??
-                    new NullDecompilerEventListener();
+                var listener = services.GetService<IEventListener>() ??
+                    new NullEventListener();
                 listener.Warn($"Model '{modelName}' is not defined for architecture '{archLabel}'.");
             }
             else if (model.Options != null)

src/Core/DynamicLinker.cs

@@ -50,10 +50,10 @@ public class DynamicLinker : IDynamicLinker
     {
         private readonly Project project;
         private readonly Program program;
-        private readonly DecompilerEventListener eventListener;
+        private readonly IEventListener eventListener;
         private readonly Dictionary<string, ImageSymbol> localProcs;
 
-        public DynamicLinker(Project project, Program program, DecompilerEventListener eventListener)
+        public DynamicLinker(Project project, Program program, IEventListener eventListener)
         {
             this.project = project ?? throw new ArgumentNullException(nameof(project));
             this.program = program;

src/Core/Hll/C/UserSignatureBuilder.cs

@@ -47,7 +47,7 @@ public UserSignatureBuilder(Program program)
         /// For each procedure, either use a user-supplied signature, 
         /// or the predefined one.
         /// </summary>
-        public void BuildSignatures(DecompilerEventListener listener)
+        public void BuildSignatures(IEventListener listener)
         {
             foreach (var de in program.Procedures)
             {

src/Core/ImageMap.cs

@@ -36,8 +36,6 @@ namespace Reko.Core
 	/// </summary>
 	public class ImageMap
 	{
-        public event EventHandler? MapChanged;
-
         public ImageMap(Address addrBase)
         {
             this.BaseAddress = addrBase ?? throw new ArgumentNullException(nameof(addrBase));
@@ -67,7 +65,6 @@ public ImageMapItem AddItem(Address addr, ImageMapItem itemNew)
             {
                 // Outside of range.
                 Items.Add(itemNew.Address, itemNew);
-                FireMapChanged();
                 return itemNew;
             }
             else
@@ -83,13 +80,11 @@ public ImageMapItem AddItem(Address addr, ImageMapItem itemNew)
                         itemNew.Size = (uint)(item.Size - delta);
                         item.Size = (uint)delta;
                         Items.Add(itemNew.Address, itemNew);
-                        FireMapChanged();
                         return itemNew;
                     }
                     else
                     {
                         Items.Add(itemNew.Address, itemNew);
-                        FireMapChanged();
                         return itemNew;
                     }
                 }
@@ -102,15 +97,13 @@ public ImageMapItem AddItem(Address addr, ImageMapItem itemNew)
                         item.Address += itemNew.Size;
                         Items[itemNew.Address] = itemNew;
                         Items[item.Address] = item;
-                        FireMapChanged();
                         return itemNew;
                     }
                     if (item.GetType() != itemNew.GetType())    //$BUGBUG: replaces the type.
                     {
                         Items[itemNew.Address] = itemNew;
                         itemNew.Size = item.Size;
                     }
-                    FireMapChanged();
                     return item;
                 }
             }
@@ -180,7 +173,6 @@ public void AddItemWithSize(Address addr, ImageMapItem itemNew)
                     Items.Add(addr, itemNew);
                 }
             }
-            FireMapChanged();
         }
 
         public ImageMap Clone()
@@ -256,8 +248,6 @@ nextItem.DataType is UnknownType &&
                 mergedItem.Size = (uint)(nextItem.EndAddress - mergedItem.Address);
                 Items.Remove(nextItem.Address);
             }
-
-            FireMapChanged();
         }
 
         /// <summary>
@@ -282,33 +272,6 @@ public bool TryFindItemExact(Address addr, out ImageMapItem item)
             return Items.TryGetValue(addr, out item);
 		}
 
-        //$TODO: the following code is a stopgap to prevent unnecessary reloading
-        // of the user interface during background operations. In the future,
-        // Reko will need to handle this in a better way, but the changes required
-        // are rather large. See GitHub [issue #567](https://github.com/uxmal/reko/issues/567)
-        // for the gory details.
-        private bool mapChangedEventHandlerPaused;
-        private bool mapChangedPendingEvents;
-
-        private void FireMapChanged()
-        {
-            if (!mapChangedEventHandlerPaused) MapChanged?.Invoke(this, EventArgs.Empty);
-            else mapChangedPendingEvents = true;
-        }
-
-        public void PauseEventHandler()
-        {
-            mapChangedEventHandlerPaused = true;
-        }
-
-        public void UnpauseEventHandler()
-        {
-            mapChangedEventHandlerPaused = false;
-            if (mapChangedPendingEvents) MapChanged?.Invoke(this, EventArgs.Empty);
-            mapChangedPendingEvents = false;
-        }
-
-
         // class ItemComparer //////////////////////////////////////////////////
 
         private class ItemComparer : IComparer<Address>

src/Core/Output/GlobalDataWriter.cs

@@ -116,7 +116,7 @@ private void WriteGlobalVariable(StructureField field)
             }
             catch (Exception ex)
             {
-                var dc = services.RequireService<DecompilerEventListener>();
+                var dc = services.RequireService<IEventListener>();
                 dc.Error(
                     dc.CreateAddressNavigator(program, addr),
                     ex,
@@ -156,7 +156,7 @@ public void WriteGlobalVariable(Address address, DataType dataType, string name)
             }
             catch (Exception ex)
             {
-                var dc = services.RequireService<DecompilerEventListener>();
+                var dc = services.RequireService<IEventListener>();
                 dc.Error(
                     dc.CreateAddressNavigator(program, address),
                     ex,
@@ -198,7 +198,7 @@ public CodeFormatter VisitArray(ArrayType at)
         {
             if (at.Length == 0)
             {
-                var dc = services.RequireService<DecompilerEventListener>();
+                var dc = services.RequireService<IEventListener>();
                 dc.Warn(
                     dc.CreateAddressNavigator(program, rdr.Address),
                     "Expected sizes of arrays to have been determined by now");

src/Core/Output/GlobalObjectTracer.cs

@@ -35,11 +35,11 @@ public class GlobalObjectTracer : IDataTypeVisitor<int>
         private readonly HashSet<Address> visited;
         private readonly DataTypeComparer cmp;
         private readonly StructureFieldCollection globalFields;
-        private readonly DecompilerEventListener eventListener;
+        private readonly IEventListener eventListener;
         private int recursionGuard;
         private EndianImageReader rdr; 
 
-        public GlobalObjectTracer(Program program, WorkList<(StructureField, Address)> wl, DecompilerEventListener eventListener)
+        public GlobalObjectTracer(Program program, WorkList<(StructureField, Address)> wl, IEventListener eventListener)
         {
             this.program = program;
             this.wl = wl;

src/Core/Output/OutputFilePolicy.cs

@@ -74,7 +74,7 @@ public OutputFilePolicy(Program program)
         /// <returns></returns>
         public abstract Dictionary<string, IDictionary<Address, IAddressable>> GetObjectPlacements(
             string fileExtension,
-            DecompilerEventListener listener);
+            IEventListener listener);
 
         /// <summary>
         /// Returns a placement mapping for rendering low-level items.

src/Core/Output/SegmentFilePolicy.cs

@@ -50,7 +50,7 @@ public SegmentFilePolicy(Program program) : base(program)
 
         public override Dictionary<string, IDictionary<Address, IAddressable>> GetObjectPlacements(
             string fileExtension,
-            DecompilerEventListener listener)
+            IEventListener listener)
         {
             Debug.Assert(fileExtension.Length > 0 && fileExtension[0] == '.');
 

src/Core/Output/SingleFilePolicy.cs

@@ -41,7 +41,7 @@ public SingleFilePolicy(Program program) : base(program)
             this.defaultDataFile = "";
         }
 
-        public override Dictionary<string, IDictionary<Address, IAddressable>> GetObjectPlacements(string fileExtension, DecompilerEventListener listener)
+        public override Dictionary<string, IDictionary<Address, IAddressable>> GetObjectPlacements(string fileExtension, IEventListener listener)
         {
             this.defaultFile = Path.ChangeExtension(program.Name, fileExtension);
             this.defaultDataFile = Path.ChangeExtension(program.Name, "globals" + fileExtension);

src/Core/Platform.cs

@@ -462,7 +462,7 @@ public TypeLibrary CreateMetadata()
         {
             if (this.MemoryMap == null || this.MemoryMap.Segments == null)
                 return null;
-            var listener = Services.RequireService<DecompilerEventListener>();
+            var listener = Services.RequireService<IEventListener>();
             var segs = MemoryMap.Segments.Select(s => MemoryMap_v1.LoadSegment(s, this, listener))
                 .Where(s => s != null)
                 .ToSortedList(s => s!.Address, s => s!);

src/Core/Serialization/MemoryMap_v1.cs

@@ -60,7 +60,7 @@ public class MemoryMap_v1
             return mmap;
         }
 
-        public static ImageSegment? LoadSegment(MemorySegment_v1 segment, IPlatform platform, DecompilerEventListener listener)
+        public static ImageSegment? LoadSegment(MemorySegment_v1 segment, IPlatform platform, IEventListener listener)
         {
             if (segment.Name is null)
             {

src/Core/Serialization/ProjectLoader.cs

@@ -47,15 +47,15 @@ public class ProjectLoader : ProjectPersister
 
         private readonly ILoader loader;
         private readonly Project project;
-        private readonly DecompilerEventListener listener;
+        private readonly IEventListener listener;
         private IPlatform? platform;
         private IProcessorArchitecture? arch;
 
         public ProjectLoader(
             IServiceProvider services,
             ILoader loader,
             ImageLocation location,
-            DecompilerEventListener listener)
+            IEventListener listener)
             : this(services, loader, new Project(location), listener)
         {
         }
@@ -64,7 +64,7 @@ public ProjectLoader(
             IServiceProvider services,
             ILoader loader,
             Project project,
-            DecompilerEventListener listener)
+            IEventListener listener)
             : base(services)
         {
             this.loader = loader;

src/Core/Services/DecompilerEventListener.cs → src/Core/Services/IEventListener.cs

@@ -31,10 +31,10 @@
 namespace Reko.Core.Services
 {
     /// <summary>
-    /// This interface is used by the worker thread to communicate with the 
+    /// This interface is used by low-level code to communicate with the 
     /// driver, be it a command line or a GUI.
     /// </summary>
-    public interface DecompilerEventListener
+    public interface IEventListener
     {
         IProgressIndicator Progress { get; }
 
@@ -63,14 +63,20 @@ public interface DecompilerEventListener
         void Error(ICodeLocation location, Exception ex, string message, params object[] args);
         void Error(ScriptError scriptError);
 
+        /// <summary>
+        /// This method is called to determine whether the caller should quit
+        /// gracefully.
+        /// </summary>
+        /// <returns>True if cancellation has been requested, false if not.
+        /// </returns>
         bool IsCanceled();
     }
 
-    public class NullDecompilerEventListener : DecompilerEventListener
+    public class NullEventListener : IEventListener
     {
-        public static DecompilerEventListener Instance { get; } = new NullDecompilerEventListener();
+        public static IEventListener Instance { get; } = new NullEventListener();
 
-        #region DecompilerEventListener Members
+        #region IEventListener Members
 
         public IProgressIndicator Progress => NullProgressIndicator.Instance;
 

src/Core/Services/ITypeLibraryLoaderService.cs

@@ -55,7 +55,7 @@ public TypeLibrary LoadMetadataIntoLibrary(IPlatform platform, TypeLibraryDefini
         {
             var cfgSvc = services.RequireService<IConfigurationService>();
             var fsSvc = services.RequireService<IFileSystemService>();
-            var listener = services.RequireService<DecompilerEventListener>();
+            var listener = services.RequireService<IEventListener>();
             try
             {
                 if (tlElement.Name == null)
@@ -90,7 +90,7 @@ public TypeLibrary LoadMetadataIntoLibrary(IPlatform platform, TypeLibraryDefini
             else
             {
                 var cfgSvc = services.RequireService<IConfigurationService>();
-                var listener = services.RequireService<DecompilerEventListener>();
+                var listener = services.RequireService<IEventListener>();
                 var ldrElement = cfgSvc.GetImageLoader(tlElement.Loader!);
                 if (ldrElement != null && !string.IsNullOrEmpty(ldrElement.TypeName)) 
                 {

src/Decompiler/Analysis/AdjacentBranchCollector.cs

@@ -24,6 +24,7 @@
 using Reko.Core.Diagnostics;
 using Reko.Core.Expressions;
 using Reko.Core.Services;
+using Reko.Services;
 using System.Diagnostics;
 using System.Linq;
 
@@ -68,10 +69,10 @@ public class AdjacentBranchCollector
         private static readonly TraceSwitch trace = new (nameof(AdjacentBranchCollector), nameof(AdjacentBranchCollector)) { Level = TraceLevel.Error };
 
         private readonly Procedure proc;
-        private readonly DecompilerEventListener listener;
+        private readonly IDecompilerEventListener listener;
         private readonly ExpressionValueComparer cmp;
 
-        public static void Transform(Program program, DecompilerEventListener eventListener)
+        public static void Transform(Program program, IDecompilerEventListener eventListener)
         {
             foreach (var proc in program.Procedures.Values)
             {
@@ -82,7 +83,7 @@ public static void Transform(Program program, DecompilerEventListener eventListe
             }
         }
 
-        public AdjacentBranchCollector(Procedure proc, DecompilerEventListener listener)
+        public AdjacentBranchCollector(Procedure proc, IDecompilerEventListener listener)
         {
             this.proc = proc;
             this.listener = listener;