MegaBites-AI/Windows-powershell

1// Licensed to the .NET Foundation under one or more agreements.2// The .NET Foundation licenses this file to you under the MIT license.3 4using System;5using System.Collections.Generic;6using System.Diagnostics;7using System.Globalization;8using System.Linq.Expressions;9using System.Reflection;10using System.Reflection.Emit;11using System.Management.Automation.InteropServices;12using System.Runtime.InteropServices;13 14namespace System.Management.Automation.ComInterop15{16    [StructLayout(LayoutKind.Sequential)]17    internal struct VariantArray118    {19        public Variant Element0;20    }21 22    [StructLayout(LayoutKind.Sequential)]23    internal struct VariantArray224    {25        public Variant Element0, Element1;26    }27 28    [StructLayout(LayoutKind.Sequential)]29    internal struct VariantArray430    {31        public Variant Element0, Element1, Element2, Element3;32    }33 34    [StructLayout(LayoutKind.Sequential)]35    internal struct VariantArray836    {37        public Variant Element0, Element1, Element2, Element3, Element4, Element5, Element6, Element7;38    }39 40    //41    // Helper for getting the right VariantArray struct for a given number of42    // arguments. Will generate a struct if needed.43    //44    // We use this because we don't have stackalloc or pinning in Expression45    // Trees, so we can't create an array of Variants directly.46    //47    internal static class VariantArray48    {49        // Don't need a dictionary for this, it will have very few elements50        // (guaranteed less than 28, in practice 0-2)51        private static readonly List<Type> s_generatedTypes = new List<Type>(0);52 53        internal static MemberExpression GetStructField(ParameterExpression variantArray, int field)54        {55            return Expression.Field(variantArray, "Element" + field);56        }57 58        internal static Type GetStructType(int args)59        {60            Debug.Assert(args >= 0);61            if (args <= 1)62            {63                return typeof(VariantArray1);64            }65 66            if (args <= 2)67            {68                return typeof(VariantArray2);69            }70 71            if (args <= 4)72            {73                return typeof(VariantArray4);74            }75 76            if (args <= 8)77            {78                return typeof(VariantArray8);79            }80 81            int size = 1;82            while (args > size)83            {84                size *= 2;85            }86 87            lock (s_generatedTypes)88            {89                // See if we can find an existing type90                foreach (Type t in s_generatedTypes)91                {92                    int arity = int.Parse(t.Name.AsSpan("VariantArray".Length), NumberStyles.Integer, CultureInfo.InvariantCulture);93                    if (size == arity)94                    {95                        return t;96                    }97                }98 99                // Else generate a new type100                Type type = CreateCustomType(size).MakeGenericType(new Type[] { typeof(Variant) });101                s_generatedTypes.Add(type);102                return type;103            }104        }105 106        private static Type CreateCustomType(int size)107        {108            TypeAttributes attrs = TypeAttributes.NotPublic | TypeAttributes.SequentialLayout;109            TypeBuilder type = UnsafeMethods.DynamicModule.DefineType("VariantArray" + size, attrs, typeof(ValueType));110            GenericTypeParameterBuilder T = type.DefineGenericParameters(new string[] { "T" })[0];111            for (int i = 0; i < size; i++)112            {113                type.DefineField("Element" + i, T, FieldAttributes.Public);114            }115            return type.CreateType();116        }117    }118}119