StructLayoutAttribute.cs

using System.Reflection;
using System.Security;

namespace System.Runtime.InteropServices
{
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct, Inherited = false)]
    [ComVisible(true)]
    [__DynamicallyInvokable]
    public sealed class StructLayoutAttribute : Attribute
    {
        private const int DEFAULT_PACKING_SIZE = 8;

        internal LayoutKind _val;

        [__DynamicallyInvokable]
        public int Pack;

        [__DynamicallyInvokable]
        public int Size;

        [__DynamicallyInvokable]
        public CharSet CharSet;

        [__DynamicallyInvokable]
        public LayoutKind Value
        {
            [__DynamicallyInvokable]
            get
            {
                return _val;
            }
        }

        [SecurityCritical]
        internal static Attribute GetCustomAttribute(RuntimeType type)
        {
            if (!IsDefined(type))
            {
                return null;
            }
            int packSize = 0;
            int classSize = 0;
            LayoutKind layoutKind = LayoutKind.Auto;
            switch (type.Attributes & TypeAttributes.LayoutMask)
            {
            case TypeAttributes.ExplicitLayout:
                layoutKind = LayoutKind.Explicit;
                break;
            case TypeAttributes.NotPublic:
                layoutKind = LayoutKind.Auto;
                break;
            case TypeAttributes.SequentialLayout:
                layoutKind = LayoutKind.Sequential;
                break;
            }
            CharSet charSet = CharSet.None;
            switch (type.Attributes & TypeAttributes.StringFormatMask)
            {
            case TypeAttributes.NotPublic:
                charSet = CharSet.Ansi;
                break;
            case TypeAttributes.AutoClass:
                charSet = CharSet.Auto;
                break;
            case TypeAttributes.UnicodeClass:
                charSet = CharSet.Unicode;
                break;
            }
            type.GetRuntimeModule().MetadataImport.GetClassLayout(type.MetadataToken, out packSize, out classSize);
            if (packSize == 0)
            {
                packSize = 8;
            }
            return new StructLayoutAttribute(layoutKind, packSize, classSize, charSet);
        }

        internal static bool IsDefined(RuntimeType type)
        {
            if (type.IsInterface || type.HasElementType || type.IsGenericParameter)
            {
                return false;
            }
            return true;
        }

        internal StructLayoutAttribute(LayoutKind layoutKind, int pack, int size, CharSet charSet)
        {
            _val = layoutKind;
            Pack = pack;
            Size = size;
            CharSet = charSet;
        }

        [__DynamicallyInvokable]
        public StructLayoutAttribute(LayoutKind layoutKind)
        {
            _val = layoutKind;
        }

        public StructLayoutAttribute(short layoutKind)
        {
            _val = (LayoutKind)layoutKind;
        }
    }
}