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// The .NET Foundation licenses this file to you under the MIT license.
#nullable enable
using System.Diagnostics;
using System.Runtime.InteropServices;
using ComTypes = System.Runtime.InteropServices.ComTypes;
namespace System.Management.Automation.InteropServices
{
/// <summary>
/// Part of ComEventHelpers APIs which allow binding
/// managed delegates to COM's connection point based events.
/// </summary>
internal partial class ComEventsSink : IDispatch, ICustomQueryInterface
{
private Guid _iidSourceItf;
private ComTypes.IConnectionPoint? _connectionPoint;
private int _cookie;
private ComEventsMethod? _methods;
private ComEventsSink? _next;
public ComEventsSink(object rcw, Guid iid)
{
_iidSourceItf = iid;
this.Advise(rcw);
}
public static ComEventsSink? Find(ComEventsSink? sinks, ref Guid iid)
{
ComEventsSink? sink = sinks;
while (sink != null && sink._iidSourceItf != iid)
{
sink = sink._next;
}
return sink;
}
public static ComEventsSink Add(ComEventsSink? sinks, ComEventsSink sink)
{
sink._next = sinks;
return sink;
}
public static ComEventsSink? RemoveAll(ComEventsSink? sinks)
{
while (sinks != null)
{
sinks.Unadvise();
sinks = sinks._next;
}
return null;
}
public static ComEventsSink? Remove(ComEventsSink sinks, ComEventsSink sink)
{
Debug.Assert(sinks != null, "removing event sink from empty sinks collection");
Debug.Assert(sink != null, "specify event sink is null");
ComEventsSink? toReturn = sinks;
if (sink == sinks)
{
toReturn = sinks._next;
}
else
{
ComEventsSink? current = sinks;
while (current != null && current._next != sink)
{
current = current._next;
}
if (current != null)
{
current._next = sink._next;
}
}
sink.Unadvise();
return toReturn;
}
public ComEventsMethod? RemoveMethod(ComEventsMethod method)
{
_methods = ComEventsMethod.Remove(_methods!, method);
return _methods;
}
public ComEventsMethod? FindMethod(int dispid)
{
return ComEventsMethod.Find(_methods, dispid);
}
public ComEventsMethod AddMethod(int dispid)
{
ComEventsMethod method = new ComEventsMethod(dispid);
_methods = ComEventsMethod.Add(_methods, method);
return method;
}
int IDispatch.GetTypeInfoCount()
{
return 0;
}
ComTypes.ITypeInfo IDispatch.GetTypeInfo(int iTInfo, int lcid)
{
throw new NotImplementedException();
}
void IDispatch.GetIDsOfNames(ref Guid iid, string[] names, int cNames, int lcid, int[] rgDispId)
{
throw new NotImplementedException();
}
private const VarEnum VT_BYREF_VARIANT = VarEnum.VT_BYREF | VarEnum.VT_VARIANT;
private const VarEnum VT_TYPEMASK = (VarEnum)0x0fff;
private const VarEnum VT_BYREF_TYPEMASK = VT_TYPEMASK | VarEnum.VT_BYREF;
private static unsafe ref Variant GetVariant(ref Variant pSrc)
{
if (pSrc.VariantType == VT_BYREF_VARIANT)
{
// For VB6 compatibility reasons, if the VARIANT is a VT_BYREF | VT_VARIANT that
// contains another VARIANT with VT_BYREF | VT_VARIANT, then we need to extract the
// inner VARIANT and use it instead of the outer one. Note that if the inner VARIANT
// is VT_BYREF | VT_VARIANT | VT_ARRAY, it will pass the below test too.
Span<Variant> pByRefVariant = new Span<Variant>(pSrc.AsByRefVariant.ToPointer(), 1);
if ((pByRefVariant[0].VariantType & VT_BYREF_TYPEMASK) == VT_BYREF_VARIANT)
{
return ref pByRefVariant[0];
}
}
return ref pSrc;
}
unsafe void IDispatch.Invoke(
int dispid,
ref Guid riid,
int lcid,
InvokeFlags wFlags,
ref ComTypes.DISPPARAMS pDispParams,
IntPtr pVarResult,
IntPtr pExcepInfo,
IntPtr puArgErr)
{
ComEventsMethod? method = FindMethod(dispid);
if (method == null)
{
return;
}
// notice the unsafe pointers we are using. This is to avoid unnecessary
// arguments marshalling. see code:ComEventsHelper#ComEventsArgsMarshalling
const int InvalidIdx = -1;
object[] args = new object[pDispParams.cArgs];
int[] byrefsMap = new int[pDispParams.cArgs];
bool[] usedArgs = new bool[pDispParams.cArgs];
int totalCount = pDispParams.cNamedArgs + pDispParams.cArgs;
var vars = new Span<Variant>(pDispParams.rgvarg.ToPointer(), totalCount);
var namedArgs = new Span<int>(pDispParams.rgdispidNamedArgs.ToPointer(), totalCount);
// copy the named args (positional) as specified
int i;
int pos;
for (i = 0; i < pDispParams.cNamedArgs; i++)
{
pos = namedArgs[i];
ref Variant pvar = ref GetVariant(ref vars[i]);
args[pos] = pvar.ToObject()!;
usedArgs[pos] = true;
int byrefIdx = InvalidIdx;
if (pvar.IsByRef)
{
byrefIdx = i;
}
byrefsMap[pos] = byrefIdx;
}
// copy the rest of the arguments in the reverse order
pos = 0;
for (; i < pDispParams.cArgs; i++)
{
// find the next unassigned argument
while (usedArgs[pos])
{
pos++;
}
ref Variant pvar = ref GetVariant(ref vars[pDispParams.cArgs - 1 - i]);
args[pos] = pvar.ToObject()!;
int byrefIdx = InvalidIdx;
if (pvar.IsByRef)
{
byrefIdx = pDispParams.cArgs - 1 - i;
}
byrefsMap[pos] = byrefIdx;
pos++;
}
// Do the actual delegate invocation
object? result = method.Invoke(args);
// convert result to VARIANT
if (pVarResult != IntPtr.Zero)
{
Marshal.GetNativeVariantForObject(result, pVarResult);
}
// Now we need to marshal all the byrefs back
for (i = 0; i < pDispParams.cArgs; i++)
{
int idxToPos = byrefsMap[i];
if (idxToPos == InvalidIdx)
{
continue;
}
ref Variant pvar = ref GetVariant(ref vars[idxToPos]);
pvar.CopyFromIndirect(args[i]);
}
}
CustomQueryInterfaceResult ICustomQueryInterface.GetInterface(ref Guid iid, out IntPtr ppv)
{
ppv = IntPtr.Zero;
if (iid == _iidSourceItf || iid == typeof(IDispatch).GUID)
{
ppv = Marshal.GetComInterfaceForObject(this, typeof(IDispatch), CustomQueryInterfaceMode.Ignore);
return CustomQueryInterfaceResult.Handled;
}
return CustomQueryInterfaceResult.NotHandled;
}
private void Advise(object rcw)
{
Debug.Assert(_connectionPoint == null, "COM event sink is already advised");
ComTypes.IConnectionPointContainer cpc = (ComTypes.IConnectionPointContainer)rcw;
ComTypes.IConnectionPoint cp;
cpc.FindConnectionPoint(ref _iidSourceItf, out cp!);
object sinkObject = this;
cp.Advise(sinkObject, out _cookie);
_connectionPoint = cp;
}
private void Unadvise()
{
Debug.Assert(_connectionPoint != null, "Can not unadvise from empty connection point");
if (_connectionPoint == null)
return;
try
{
_connectionPoint.Unadvise(_cookie);
Marshal.ReleaseComObject(_connectionPoint);
}
catch
{
// swallow all exceptions on unadvise
// the host may not be available at this point
}
finally
{
_connectionPoint = null;
}
}
}
}
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