P/Invoke definitions for PTOKEN_PRIVILEGES, for use in GetTokenInformation or AdjustTokenPrivileges

PTOKEN_PRIVILEGES.cs

[StructLayout(LayoutKind.Sequential)]
public struct LUID
{
    public int LowPart;
    public int HighPart;
}

[StructLayout(LayoutKind.Sequential)]
public struct LUID_AND_ATTRIBUTES
{
    public LUID Luid;
    public int Attr;
}

[StructLayout(LayoutKind.Sequential)]
public struct PTOKEN_PRIVILEGES : IDisposable, IEnumerable<LUID_AND_ATTRIBUTES>
{
    IntPtr value;

    public PTOKEN_PRIVILEGES(IntPtr value)
    {
        this.value = value;
    }

    public int Count
    {
        get => this.value == IntPtr.Zero ? 0 : Marshal.ReadInt32(this.value);
        private set => Marshal.WriteInt32(this.value, value);
    }

    private IntPtr GetIndexPtr(int index)
    {
        if (index < 0 || index >= this.Count) throw new IndexOutOfRangeException($"Index {index} out of range for Privileges with Count = {this.Count}!");
        return this.value + 4 + Marshal.SizeOf<LUID_AND_ATTRIBUTES>() * index;
    }

    public LUID_AND_ATTRIBUTES this[int index]
    {
        get => Marshal.PtrToStructure<LUID_AND_ATTRIBUTES>(this.GetIndexPtr(index));
        set => Marshal.StructureToPtr(value, this.GetIndexPtr(index), false);
    }

    public PTOKEN_PRIVILEGES(int count)
    {
        this.value = Marshal.AllocHGlobal(4 + count * Marshal.SizeOf<LUID_AND_ATTRIBUTES>());
        this.Count = count;
    }

    public PTOKEN_PRIVILEGES(LUID_AND_ATTRIBUTES[] data) : this(data.Length)
    {
        for (int i = 0; i < this.Count; ++i) this[i] = data[i];
    }

    private struct Enumerator : IEnumerator<LUID_AND_ATTRIBUTES>
    {
        public PTOKEN_PRIVILEGES privileges;
        public int index;

        public LUID_AND_ATTRIBUTES Current => privileges[index];

        object System.Collections.IEnumerator.Current => this.Current;

        public bool MoveNext()
        {
            if (this.index + 1 >= privileges.Count) { return false; }
            this.index += 1;
            return true;
        }

        public void Reset()
        {
            this.index = -1;
        }

        public void Dispose()
        {
            this.privileges = default;
        }
    }

    public IEnumerator<LUID_AND_ATTRIBUTES> GetEnumerator() => new Enumerator { privileges = this, index = -1 };

    IEnumerator IEnumerable.GetEnumerator() => this.GetEnumerator();

    public void Dispose()
    {
        Marshal.FreeHGlobal(this.value);
        this.value = IntPtr.Zero;
    }
}