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// The .NET Foundation licenses this file to you under the MIT license.
#nullable enable
using System.Collections.Generic;
using System.Diagnostics;
using System.Reflection;
namespace System.Management.Automation.InteropServices
{
/// <summary>
/// Part of ComEventHelpers APIs which allow binding
/// managed delegates to COM's connection point based events.
/// </summary>
internal class ComEventsMethod
{
/// <summary>
/// This delegate wrapper class handles dynamic invocation of delegates. The reason for the wrapper's
/// existence is that under certain circumstances we need to coerce arguments to types expected by the
/// delegates signature. Normally, reflection (Delegate.DynamicInvoke) handles type coercion
/// correctly but one known case is when the expected signature is 'ref Enum' - in this case
/// reflection by design does not do the coercion. Since we need to be compatible with COM interop
/// handling of this scenario - we are pre-processing delegate's signature by looking for 'ref enums'
/// and cache the types required for such coercion.
/// </summary>
public class DelegateWrapper
{
private bool _once;
private int _expectedParamsCount;
private Type?[]? _cachedTargetTypes;
public DelegateWrapper(Delegate d, bool wrapArgs)
{
Delegate = d;
WrapArgs = wrapArgs;
}
public Delegate Delegate { get; set; }
public bool WrapArgs { get; }
public object? Invoke(object[] args)
{
if (Delegate == null)
{
return null;
}
if (!_once)
{
PreProcessSignature();
_once = true;
}
if (_cachedTargetTypes != null && _expectedParamsCount == args.Length)
{
for (int i = 0; i < _expectedParamsCount; i++)
{
if (_cachedTargetTypes[i] != null)
{
args[i] = Enum.ToObject(_cachedTargetTypes[i]!, args[i]); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
}
}
}
return Delegate.DynamicInvoke(WrapArgs ? new object[] { args } : args);
}
private void PreProcessSignature()
{
ParameterInfo[] parameters = Delegate.Method.GetParameters();
_expectedParamsCount = parameters.Length;
Type?[]? targetTypes = null;
for (int i = 0; i < _expectedParamsCount; i++)
{
ParameterInfo pi = parameters[i];
// recognize only 'ref Enum' signatures and cache
// both enum type and the underlying type.
if (pi.ParameterType.IsByRef
&& pi.ParameterType.HasElementType
&& pi.ParameterType.GetElementType()!.IsEnum)
{
targetTypes ??= new Type?[_expectedParamsCount];
targetTypes[i] = pi.ParameterType.GetElementType();
}
}
if (targetTypes != null)
{
_cachedTargetTypes = targetTypes;
}
}
}
/// <summary>
/// Invoking ComEventsMethod means invoking a multi-cast delegate attached to it.
/// Since multicast delegate's built-in chaining supports only chaining instances of the same type,
/// we need to complement this design by using an explicit linked list data structure.
/// </summary>
private readonly List<DelegateWrapper> _delegateWrappers = new List<DelegateWrapper>();
private readonly int _dispid;
private ComEventsMethod? _next;
public ComEventsMethod(int dispid)
{
_dispid = dispid;
}
public static ComEventsMethod? Find(ComEventsMethod? methods, int dispid)
{
while (methods != null && methods._dispid != dispid)
{
methods = methods._next;
}
return methods;
}
public static ComEventsMethod Add(ComEventsMethod? methods, ComEventsMethod method)
{
method._next = methods;
return method;
}
public static ComEventsMethod? Remove(ComEventsMethod methods, ComEventsMethod method)
{
Debug.Assert(methods != null, "removing method from empty methods collection");
Debug.Assert(method != null, "specify method is null");
if (methods == method)
{
return methods._next;
}
else
{
ComEventsMethod? current = methods;
while (current != null && current._next != method)
{
current = current._next;
}
if (current != null)
{
current._next = method._next;
}
return methods;
}
}
public bool Empty
{
get
{
lock (_delegateWrappers)
{
return _delegateWrappers.Count == 0;
}
}
}
public void AddDelegate(Delegate d, bool wrapArgs = false)
{
lock (_delegateWrappers)
{
// Update an existing delegate wrapper
foreach (DelegateWrapper wrapper in _delegateWrappers)
{
if (wrapper.Delegate.GetType() == d.GetType() && wrapper.WrapArgs == wrapArgs)
{
wrapper.Delegate = Delegate.Combine(wrapper.Delegate, d);
return;
}
}
var newWrapper = new DelegateWrapper(d, wrapArgs);
_delegateWrappers.Add(newWrapper);
}
}
public void RemoveDelegate(Delegate d, bool wrapArgs = false)
{
lock (_delegateWrappers)
{
// Find delegate wrapper index
int removeIdx = -1;
DelegateWrapper? wrapper = null;
for (int i = 0; i < _delegateWrappers.Count; i++)
{
DelegateWrapper wrapperMaybe = _delegateWrappers[i];
if (wrapperMaybe.Delegate.GetType() == d.GetType() && wrapperMaybe.WrapArgs == wrapArgs)
{
removeIdx = i;
wrapper = wrapperMaybe;
break;
}
}
if (removeIdx < 0)
{
// Not present in collection
return;
}
// Update wrapper or remove from collection
Delegate? newDelegate = Delegate.Remove(wrapper!.Delegate, d);
if (newDelegate != null)
{
wrapper.Delegate = newDelegate;
}
else
{
_delegateWrappers.RemoveAt(removeIdx);
}
}
}
public void RemoveDelegates(Func<Delegate, bool> condition)
{
lock (_delegateWrappers)
{
// Find delegate wrapper indexes. Iterate in reverse such that the list to remove is sorted by high to low index.
List<int> toRemove = new List<int>();
for (int i = _delegateWrappers.Count - 1; i >= 0; i--)
{
DelegateWrapper wrapper = _delegateWrappers[i];
Delegate[] invocationList = wrapper.Delegate.GetInvocationList();
foreach (Delegate delegateMaybe in invocationList)
{
if (condition(delegateMaybe))
{
Delegate? newDelegate = Delegate.Remove(wrapper!.Delegate, delegateMaybe);
if (newDelegate != null)
{
wrapper.Delegate = newDelegate;
}
else
{
toRemove.Add(i);
}
}
}
}
foreach (int idx in toRemove)
{
_delegateWrappers.RemoveAt(idx);
}
}
}
public object? Invoke(object[] args)
{
Debug.Assert(!Empty);
object? result = null;
lock (_delegateWrappers)
{
foreach (DelegateWrapper wrapper in _delegateWrappers)
{
result = wrapper.Invoke(args);
}
}
return result;
}
}
}
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