// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
#nullable disable
 
using System;
using System.Runtime.InteropServices;
 
namespace Microsoft.VisualStudio.LanguageServices.CSharp.ProjectSystemShim;
 
/// <summary>
/// This is a terrible, terrible hack around the C# project system in
/// CCscMSBuildHostObject::SetDelaySign. To indicate a value of "unset"
/// for boolean options, they create variant of type VT_BOOL with the boolean
/// field being a value of "4". The CLR, if it marshals this variant, marshals
/// it as a "true" which is indistinguishable from a real VARIANT_TRUE. So
/// instead we define this structure of the same layout, and marshal the variant
/// as this structure. We can then pick out this broken pattern, and convert
/// it to null instead of true.
/// </summary>
[StructLayout(LayoutKind.Sequential)]
internal readonly struct HACK_VariantStructure
{
    private readonly short _type;
 
    private readonly short _padding1;
    private readonly short _padding2;
    private readonly short _padding3;
 
    private readonly short _booleanValue;
    private readonly IntPtr _padding4; // this will be aligned to the IntPtr-sized address
 
    public unsafe object ConvertToObject()
    {
        if (_type == (short)VarEnum.VT_BOOL && _booleanValue == 4)
        {
            return null;
        }
 
        // Can't take an address of this since it might move, so....
        var localCopy = this;
        return Marshal.GetObjectForNativeVariant((IntPtr)(&localCopy));
    }
}