/// <summary>
/// Implements the add or remove accessor of the event.
/// </summary>
/// <param name="isAdd">true to create an 'add' method; false to create a 'remove' method.</param>
/// <param name="evnt">Event to implement.</param>
/// <param name="backingField">Multicast delegate field backing the event.</param>
private static void ImplementAccessor(bool isAdd, GeneratedEvent evnt, IGeneratedField backingField)
{
Type backingFieldType = backingField.FieldBuilder.FieldType;
// get the Delegate.Combine() method when adding a handler and Delegate.Remove() when removing a handler
MethodInfo delegateMethod = typeof(Delegate).GetMethod(isAdd ? "Combine" : "Remove", new[] { typeof(Delegate), typeof(Delegate) });
// get the System.Threading.Interlocked.CompareExchange(ref object, object, object) method
MethodInfo interlockedCompareExchangeGenericMethod = typeof(Interlocked)
.GetMethods()
.Single(m => m.Name == "CompareExchange" && m.GetGenericArguments().Length == 1);
MethodInfo interlockedCompareExchangeMethod = interlockedCompareExchangeGenericMethod.MakeGenericMethod(backingFieldType);
// emit code to combine the handler with the multicast delegate in the backing field respectively remove the handler from it
ILGenerator msil = isAdd ? evnt.AddAccessor.MethodBuilder.GetILGenerator() : evnt.RemoveAccessor.MethodBuilder.GetILGenerator();
LocalBuilder local0 = msil.DeclareLocal(backingFieldType);
LocalBuilder local1 = msil.DeclareLocal(backingFieldType);
LocalBuilder local2 = msil.DeclareLocal(backingFieldType);
Label retryLabel = msil.DefineLabel();
if (evnt.Kind == EventKind.Static)
{
msil.Emit(OpCodes.Ldsfld, backingField.FieldBuilder);
msil.Emit(OpCodes.Stloc_0);
msil.MarkLabel(retryLabel);
msil.Emit(OpCodes.Ldloc_0);
msil.Emit(OpCodes.Stloc_1);
msil.Emit(OpCodes.Ldloc_1);
msil.Emit(OpCodes.Ldarg_0);
msil.EmitCall(OpCodes.Call, delegateMethod, null);
msil.Emit(OpCodes.Castclass, backingFieldType);
msil.Emit(OpCodes.Stloc_2);
msil.Emit(OpCodes.Ldsflda, backingField.FieldBuilder);
msil.Emit(OpCodes.Ldloc_2);
msil.Emit(OpCodes.Ldloc_1);
msil.Emit(OpCodes.Call, interlockedCompareExchangeMethod);
msil.Emit(OpCodes.Stloc_0);
msil.Emit(OpCodes.Ldloc_0);
msil.Emit(OpCodes.Ldloc_1);
msil.Emit(OpCodes.Bne_Un_S, retryLabel);
msil.Emit(OpCodes.Ret);
}
else
{
msil.Emit(OpCodes.Ldarg_0);
msil.Emit(OpCodes.Ldfld, backingField.FieldBuilder);
msil.Emit(OpCodes.Stloc_0);
msil.MarkLabel(retryLabel);
msil.Emit(OpCodes.Ldloc_0);
msil.Emit(OpCodes.Stloc_1);
msil.Emit(OpCodes.Ldloc_1);
msil.Emit(OpCodes.Ldarg_1);
msil.EmitCall(OpCodes.Call, delegateMethod, null);
msil.Emit(OpCodes.Castclass, backingFieldType);
msil.Emit(OpCodes.Stloc_2);
msil.Emit(OpCodes.Ldarg_0);
msil.Emit(OpCodes.Ldflda, backingField.FieldBuilder);
msil.Emit(OpCodes.Ldloc_2);
msil.Emit(OpCodes.Ldloc_1);
msil.Emit(OpCodes.Call, interlockedCompareExchangeMethod);
msil.Emit(OpCodes.Stloc_0);
msil.Emit(OpCodes.Ldloc_0);
msil.Emit(OpCodes.Ldloc_1);
msil.Emit(OpCodes.Bne_Un_S, retryLabel);
msil.Emit(OpCodes.Ret);
}
}
/// <summary>
/// Reviews the default declaration of the event and adds additional type declarations, if necessary.
/// </summary>
/// <param name="engine">The <see cref="CodeGenEngine"/> assembling the type in creation.</param>
/// <param name="evnt">The event to review.</param>
public void Declare(CodeGenEngine engine, GeneratedEvent evnt)
{
// declare the backing field storing event handlers
mBackingField = engine.AddField(evnt.Type, null, evnt.Kind == EventKind.Static, evnt.Visibility, null);
}
/// <summary>
/// Implements the event.
/// </summary>
/// <param name="engine">The <see cref="CodeGenEngine"/> assembling the type in creation.</param>
/// <param name="evnt">The event to implement.</param>
public void Implement(CodeGenEngine engine, GeneratedEvent evnt)
{
ImplementAccessor(true, evnt, mBackingField);
ImplementAccessor(false, evnt, mBackingField);
ImplementEventRaiser(evnt, mBackingField);
}
/// <summary>
/// Adds the event raiser method.
/// </summary>
/// <param name="evnt">Event to implement.</param>
/// <param name="backingField">Multicast delegate field backing the event.</param>
private static void ImplementEventRaiser(GeneratedEvent evnt, IGeneratedField backingField)
{
ILGenerator msil = evnt.Raiser.MethodBuilder.GetILGenerator();
if (evnt.Type == typeof(EventHandler) || evnt.Type == typeof(EventHandler <EventArgs>))
{
// System.EventHandler
// System.EventHandler<EventArgs>
FieldInfo EventArgsEmpty = typeof(EventArgs).GetField("Empty");
LocalBuilder handlerLocalBuilder = msil.DeclareLocal(backingField.FieldBuilder.FieldType);
Label label = msil.DefineLabel();
if (evnt.Kind == EventKind.Static)
{
msil.Emit(OpCodes.Ldsfld, backingField.FieldBuilder);
msil.Emit(OpCodes.Stloc, handlerLocalBuilder);
msil.Emit(OpCodes.Ldloc, handlerLocalBuilder);
msil.Emit(OpCodes.Brfalse_S, label);
msil.Emit(OpCodes.Ldloc, handlerLocalBuilder);
msil.Emit(OpCodes.Ldnull); // load sender (null)
msil.Emit(OpCodes.Ldsfld, EventArgsEmpty); // load event arguments
}
else
{
msil.Emit(OpCodes.Ldarg_0);
msil.Emit(OpCodes.Ldfld, backingField.FieldBuilder);
msil.Emit(OpCodes.Stloc, handlerLocalBuilder);
msil.Emit(OpCodes.Ldloc, handlerLocalBuilder);
msil.Emit(OpCodes.Brfalse_S, label);
msil.Emit(OpCodes.Ldloc, handlerLocalBuilder);
msil.Emit(OpCodes.Ldarg_0); // load sender (this)
msil.Emit(OpCodes.Ldsfld, EventArgsEmpty); // load event arguments
}
MethodInfo invokeMethod = backingField.FieldBuilder.FieldType.GetMethod("Invoke");
msil.Emit(OpCodes.Callvirt, invokeMethod);
msil.MarkLabel(label);
msil.Emit(OpCodes.Ret);
return;
}
else if (evnt.Type.IsGenericType && evnt.Type.GetGenericTypeDefinition() == typeof(EventHandler <>))
{
// EventHandler<T> with T derived from System.EventArgs
LocalBuilder handlerLocalBuilder = msil.DeclareLocal(backingField.FieldBuilder.FieldType);
Label label = msil.DefineLabel();
if (evnt.Kind == EventKind.Static)
{
msil.Emit(OpCodes.Ldsfld, backingField.FieldBuilder);
msil.Emit(OpCodes.Stloc, handlerLocalBuilder);
msil.Emit(OpCodes.Ldloc, handlerLocalBuilder);
msil.Emit(OpCodes.Brfalse_S, label);
msil.Emit(OpCodes.Ldloc, handlerLocalBuilder);
msil.Emit(OpCodes.Ldnull); // load sender (null)
msil.Emit(OpCodes.Ldarg_0); // load event arguments
}
else
{
msil.Emit(OpCodes.Ldarg_0);
msil.Emit(OpCodes.Ldfld, backingField.FieldBuilder);
msil.Emit(OpCodes.Stloc, handlerLocalBuilder);
msil.Emit(OpCodes.Ldloc, handlerLocalBuilder);
msil.Emit(OpCodes.Brfalse_S, label);
msil.Emit(OpCodes.Ldloc, handlerLocalBuilder);
msil.Emit(OpCodes.Ldarg_0); // load sender (this)
msil.Emit(OpCodes.Ldarg_1); // load event arguments
}
MethodInfo invokeMethod = backingField.FieldBuilder.FieldType.GetMethod("Invoke");
msil.Emit(OpCodes.Callvirt, invokeMethod);
msil.MarkLabel(label);
msil.Emit(OpCodes.Ret);
return;
}
else if (typeof(Delegate).IsAssignableFrom(evnt.Type))
{
MethodInfo invokeMethod = backingField.FieldBuilder.FieldType.GetMethod("Invoke");
LocalBuilder handlerLocalBuilder = msil.DeclareLocal(backingField.FieldBuilder.FieldType);
Label label = msil.DefineLabel();
if (evnt.Kind == EventKind.Static)
{
msil.Emit(OpCodes.Ldsfld, backingField.FieldBuilder);
}
else
{
msil.Emit(OpCodes.Ldarg_0);
msil.Emit(OpCodes.Ldfld, backingField.FieldBuilder);
}
msil.Emit(OpCodes.Stloc, handlerLocalBuilder);
msil.Emit(OpCodes.Ldloc, handlerLocalBuilder);
msil.Emit(OpCodes.Brfalse_S, label);
msil.Emit(OpCodes.Ldloc, handlerLocalBuilder);
int argumentOffset = evnt.Kind == EventKind.Static ? 0 : 1;
for (int i = 0; i < evnt.Raiser.ParameterTypes.Length; i++)
{
CodeGenHelpers.EmitLoadArgument(msil, argumentOffset + i);
}
msil.Emit(OpCodes.Callvirt, invokeMethod);
msil.MarkLabel(label);
msil.Emit(OpCodes.Ret);
return;
}
throw new NotSupportedException("The event type is not supported.");
}
