Calling DeviceIoControl from C# with IOCTL_DVD_* Control Codes

I am trying to call DeviceIoControl from C# for IOCTL_DVD_* control codes. Having read a lot of information and trying a number of examples I have not made much progress.

What I am trying to eventually do is get a DVD_LAYER_DESCRIPTOR structure about the media currently in the DVD drive. I can call CreateFile successfully on the DVD device, but when I try to call DeviceIoControl with the control code IOCTL_DVD_START_SESSION it returns a success code but I don't seem to get the sessionId value back successfully, always returns 0. (And any attempt I have then made to try getting the layer description with IOCTL_DVD_READ_STRUCTURE fails, i.e. function fails or returns success but gives a blank output structure.)

After finding some C code which makes similar calls I was able to compile this code (using Visual C++ 2008 Express Edition) and it successfully is able to start a session, read the DVD_LAYER_DESCRIPTOR, and close the session without problem so I know this works.

The C# issues appear to relate to how the external function is defined and the parameters marshalled. And how the various structures that are passed and returned are defined.

I have looked at www.pinvoke.net for how they define it, and have used some of the example code and definitions given but still have the same issues as outlined above. Part of the problem seems to be that for each IOCTL control code the parameters are different, mostly structs, but for IOCTL_DVD_START_SESSION the output value is a 32 bit integer. How can an extern method in C# be defined to handle these different cases? Also various structs, defined with the right sized member types, show they are different sizes between the C and C# code, but the individual members are the same sizes???

If I use a program like DeviceIOView and watch the calls made by both the C code and C# code for IOCTL_DVD_START_SESSION the C version returns a sessionid of 3 and DeviceIOView shows the data being sent back when running the C# code is also 3 so there seems to be some sort of Marshalling issue of the returned parameters as we only see 0 in the C# code

Does anyone have any ideas or working example code on how to call DeviceIoControl from C# to access DVD information? (Showing how the structures and function should be defined and used.) Any links to useful websites or other advice would be much appreciated.

(Being developed in Visual C# 2008 Express Edition, .NET 3.5.)

N Johns

Example Code (Added)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Win32.SafeHandles;
using System.Runtime.InteropServices;
using System.IO;
using System.Threading;

namespace Example
{
    class Program
    {
        static void Main(string[] args)
        {
            string driveLetter = args[0].Substring(0, 1).ToUpper() + ":";

            SafeFileHandle _hdev = CreateFileR(driveLetter);
            if (_hdev.IsClosed | _hdev.IsInvalid)
            {
                Console.WriteLine("Error opening device");
                return;
            }

            Console.WriteLine("DeviceIoControl - Version One");

            Console.WriteLine("IOCTL_DVD_START_SESSION");

            bool result = false;
            int bytesReturned = 0;
            int sessionId = 0;

            result = DeviceIoControl(_hdev, CTL_CODE(0x00000033, 0x0400, 0, 1), IntPtr.Zero, 0, (IntPtr)sessionId, Marshal.SizeOf(sessionId), out bytesReturned, IntPtr.Zero);

            if (result == false)
            {
                int error_code = Marshal.GetLastWin32Error();
                Console.WriteLine("Result: " + result);
                Console.WriteLine("error code: " + error_code);
            }
            else
            {
                Console.WriteLine("Result: " + result);
                Console.WriteLine("BytesReturned: " + bytesReturned);
                Console.WriteLine("SessionId: " + sessionId);
                Console.WriteLine("sizeof(SessionId): " + Marshal.SizeOf(sessionId));
            }

            Console.WriteLine("IOCTL_DVD_READ_STRUCTURE");
            Console.WriteLine("Skipping...");

            Console.WriteLine("IOCTL_DVD_END_SESSION");
            bytesReturned = 0;

            result = DeviceIoControl(_hdev, CTL_CODE(0x00000033, 0x0403, 0, 1), new IntPtr(sessionId), Marshal.SizeOf(sessionId), IntPtr.Zero, 0, out bytesReturned, IntPtr.Zero);

            if (result == false)
            {
                int error_code = Marshal.GetLastWin32Error();
                Console.WriteLine("error code: " + error_code);
                Console.WriteLine("Result: " + result);
            }
            else
            {
                Console.WriteLine("Result: " + result);
                Console.WriteLine("BytesReturned: " + bytesReturned);
            }

            Console.WriteLine("\nDeviceIoControl - Version Two");

            Console.WriteLine("IOCTL_DVD_START_SESSION");

            result = false;
            uint bytesReturned2 = 0;
            sessionId = -10;

            NativeOverlapped nativeOverlapped = new NativeOverlapped();

            result = DeviceIoControlAlt(_hdev, EIOControlCode.DvdStartSession, 0, 0, sessionId, (uint)Marshal.SizeOf(sessionId), ref bytesReturned2, ref nativeOverlapped);

            if (result == false)
            {
                int error_code = Marshal.GetLastWin32Error();
                Console.WriteLine("Result: " + result);
                Console.WriteLine("error code: " + error_code);
            }
            else
            {
                Console.WriteLine("Result: " + result);
                Console.WriteLine("BytesReturned: " + bytesReturned2);
                Console.WriteLine("SessionId: " + sessionId);
                Console.WriteLine("sizeof(SessionId): " + Marshal.SizeOf(sessionId));
            }

            Console.WriteLine("IOCTL_DVD_READ_STRUCTURE");
            Console.WriteLine("Skipping...");

            Console.WriteLine("IOCTL_DVD_END_SESSION");
            bytesReturned2 = 0;

            result = DeviceIoControlAlt(_hdev, EIOControlCode.DvdEndSession, sessionId, (uint)Marshal.SizeOf(sessionId), 0, 0, ref bytesReturned2, ref nativeOverlapped);

            if (result == false)
            {
                int error_code = Marshal.GetLastWin32Error();
                Console.WriteLine("Result: " + result);
                Console.WriteLine("error code: " + error_code);
            }
            else
            {
                Console.WriteLine("Result: " + result);
                Console.WriteLine("BytesReturned: " + bytesReturned2);
            }

            _hdev.Close();
        }

        public static int CTL_CODE(int DeviceType, int Function, int Method, int Access)
        {
            return (((DeviceType) << 16) | ((Access) << 14) | ((Function) << 2)
              | (Method));
        } 

        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr CreateFile(string lpFileName, uint dwDesiredAccess, uint dwShareMode, IntPtr lpSecurityAttributes, uint dwCreationDisposition, uint dwFlagsAndAttributes, IntPtr hTemplateFile);
        public static SafeFileHandle CreateFileR(string device)
        {
            string str = device.EndsWith(@"\") ? device.Substring(0, device.Length - 1) : device;
            return new SafeFileHandle(CreateFile(@"\\.\" + str, WinntConst.GENERIC_READ, WinntConst.FILE_SHARE_READ, IntPtr.Zero, WinntConst.OPEN_EXISTING, WinntConst.FILE_ATTRIBUTE_NORMAL, IntPtr.Zero), true);
        }

        [return: MarshalAs(UnmanagedType.Bool)]
        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern bool DeviceIoControl([In] SafeFileHandle hDevice,
            [In] int dwIoControlCode, [In] IntPtr lpInBuffer,
            [In] int nInBufferSize, [Out] IntPtr lpOutBuffer,
            [In] int nOutBufferSize, out int lpBytesReturned,
            [In] IntPtr lpOverlapped);

        internal class WinntConst
        {
            // Fields
            internal static uint FILE_ATTRIBUTE_NORMAL = 0x80;
            internal static uint FILE_SHARE_READ = 1;
            internal static uint GENERIC_READ = 0x80000000;
            internal static uint OPEN_EXISTING = 3;
        }

        // Other code for DeviceIoControl from pinvoke.net
        [Flags]
        public enum EIOControlCode : uint
        {
            // DVD
            DvdReadStructure = (EFileDevice.Dvd << 16) | (0x0450 << 2) | EMethod.Buffered | (FileAccess.Read << 14),
            DvdStartSession = (EFileDevice.Dvd << 16) | (0x0400 << 2) | EMethod.Buffered | (FileAccess.Read << 14),
            DvdEndSession = (EFileDevice.Dvd << 16) | (0x0403 << 2) | EMethod.Buffered | (FileAccess.Read << 14)
        };

        [Flags]
        public enum EFileDevice : uint
        {
            Dvd = 0x00000033,
        }

        [Flags]
        public enum EMethod : uint
        {
            Buffered = 0,
            InDirect = 1,
            OutDirect = 2,
            Neither = 3
        }

        [DllImport("Kernel32.dll", EntryPoint="DeviceIoControl", SetLastError = true, CharSet = CharSet.Auto)]
        public static extern bool DeviceIoControlAlt(
            Microsoft.Win32.SafeHandles.SafeFileHandle hDevice,
            EIOControlCode IoControlCode,
            [MarshalAs(UnmanagedType.AsAny)][In] object InBuffer,
            uint nInBufferSize,
            [MarshalAs(UnmanagedType.AsAny)][Out] object OutBuffer,
            uint nOutBufferSize,
            ref uint pBytesReturned,
            [In] ref System.Threading.NativeOverlapped Overlapped
        );
    }
}

To run this code you need to specify the drive letter of a DVD drive on the command line.

Output

DeviceIoControl - Version One
IOCTL_DVD_START_SESSION
Result: False
error code: 122
IOCTL_DVD_READ_STRUCTURE
Skipping...
IOCTL_DVD_END_SESSION
error code: 87
Result: False

DeviceIoControl - Version Two
IOCTL_DVD_START_SESSION
Result: True
BytesReturned: 4
SessionId: -10
sizeof(SessionId): 4
IOCTL_DVD_READ_STRUCTURE
Skipping...
IOCTL_DVD_END_SESSION
Result: True
BytesReturned: 0 

The first version fails on both calls with the given error codes:

122 - ERROR_INSUFFICIENT_BUFFER

87 - ERROR_INVALID_PARAMETER

The second version seems to succeed but the value of SessionId is -10, the initialised value. (From MSDN this value should be between -1 and 3?) The end session also succeeds.

[ Note: the second version start session only seems to succeed on every other invocation, not sure why but this also appears to be an issue in the C code I have as it's error handling is to retry again. ]

The problem lies here:

result = DeviceIoControl(_hdev, CTL_CODE(0x00000033, 0x0400, 0, 1),
   IntPtr.Zero, 0, (IntPtr)sessionId, Marshal.SizeOf(sessionId),
   out bytesReturned, IntPtr.Zero);

Driver expects pointer to buffer in lpOutBuffer, but you instead provide sessionId itself (which is zero). Of course this will not work.

Here what you need to do:

IntPtr buffer = Marshal.AllocHGlobal(sizeof(int));
result = DeviceIoControl(_hdev, CTL_CODE(0x00000033, 0x0400, 0, 1),
    IntPtr.Zero, 0, buffer, sizeof(int), out bytesReturned, IntPtr.Zero);
int sessionId = Marshal.ReadInt32(buffer);
Marshal.FreeHGlobal(buffer);

BTW, the same applies to all following DeviceIoControl calls, you again provide value, when you need provide pointer to value. And you also need to check if your CTL_CODE function builds valid io code.

Again, DeviceIoControl expects pointers to buffers for in and out structures.