<bullshark@gmail.com> wrote in message
news:1154028193.896588.256280@m79g2000cwm.googlegroups.com...
> We have:
> [StructLayout(LayoutKind.Sequential, CharSet= CharSet.Ansi)]
> public unsafe struct SP_DEVICE_INTERFACE_DETAIL_DATA {
> public int cbSize;
> [MarshalAs(UnmanagedType.ByValArray, SizeConst=84)]
> public char[] DevicePath;
> }
>
> The setupapi.dll method SetupDiGetDeviceInterfaceDetail requires us to
> call it once to find the size of the output buffer "DevicePath", and
> then to call it again, after allocating the char[] to fetch the
> details.
>
> The code above is kludged to marshal a fixed size. It works fine. What
> I can't seem to figure is how to accomplish this without the kludging
> to a pre-determined size.
>
> Is there no way to do this without a C library as a go-between?
>
> This idiom occurs so often in Win32 that I find it hard to believe that
> theres not a simple solution. I tried manual marshalling with
> Marshal.AllocHGlobal, which was successfully used to retrieve the
> details, but then extracting "DevicePath" from an IntPtr was
> problematic. Marshal.PtrToStructure doesn't work on valueTypes and I
> couldn't figure a way to get from (coerce) the IntPtr into a char[] for
> Marshal.copy.
>
> Thanks in advance for any ideas,
>
> bullshark
>