Is SP_DEVICE_INTERFACE_DETAIL_DATA_W usable?

[Slion]

I'm not sure how to use it with SetupDiGetDeviceInterfaceDetail. Then again I'm not sure I would know how to do it in C either. That any size array thing is so weird.

[AArnott]

That struct is incorrectly generated at the moment. You can track #387 for resolution of that.

[Slion]

As a workaround I'm using the following definition to just have a fixed size array that should be big enough and then cast it as I pass it to the function.

        public partial struct SP_DEVICE_INTERFACE_DETAIL_DATA
        {
            public uint cbSize;
            public __char_1 DevicePath;

            [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
            public unsafe partial struct __char_1
            {
                public fixed char _0[512];

                /// <summary>Always <c>1</c>.</summary>
                public readonly int Length => 512;

                /// <summary>
                /// Copies the fixed array to a new string up to the specified length regardless of whether there are null terminating characters.
                /// </summary>
                /// <exception cref="ArgumentOutOfRangeException">
                /// Thrown when <paramref name="length"/> is less than <c>0</c> or greater than <see cref="Length"/>.
                /// </exception>
                public unsafe readonly string ToString(int length)
                {
                    if (length < 0 || length > Length) throw new ArgumentOutOfRangeException(nameof(length), length, "Length must be between 0 and the fixed array length.");
                    fixed (char* p0 = _0)
                        return new string(p0, 0, length);
                }

                /// <summary>
                /// Copies the fixed array to a new string, stopping before the first null terminator character or at the end of the fixed array (whichever is shorter).
                /// </summary>
                public override readonly unsafe string ToString()
                {
                    int length;
                    fixed (char* p = _0)
                    {
                        char* pLastExclusive = p + Length;
                        char* pCh = p;
                        for (;
                        pCh < pLastExclusive && *pCh != '\0';
                        pCh++) ;
                        length = checked((int)(pCh - p));
                    }
                    return ToString(length);
                }
            }
        }

[virzak]

My workaround uses dynamic size with existing definition:

int DevicePathOffset = (int)(nint)Marshal.OffsetOf<SP_DEVICE_INTERFACE_DETAIL_DATA_W>(nameof(SP_DEVICE_INTERFACE_DETAIL_DATA_W.DevicePath));

var buffer = new byte[requiredSize];
fixed (byte* pBuffer = buffer)
{
    var deviceInterfaceDetailData = (SP_DEVICE_INTERFACE_DETAIL_DATA_W*)pBuffer;
    deviceInterfaceDetailData->cbSize = (uint)sizeof(SP_DEVICE_INTERFACE_DETAIL_DATA_W);

    if (!SetupDiGetDeviceInterfaceDetail(
        diskClassDevices,
        deviceInterfaceData,
        deviceInterfaceDetailData,
        requiredSize,
        null,
        null))
    {
        // Error
        return;
    }
}

var devicePath = System.Text.Encoding.Unicode.GetString(buffer[DevicePathOffset..]);