Marshal struct with embeded array of struct

[Daniel Brown]

I am coding a managed C# wrapper for an unmanaged C DLL and I am unable to
marshal a structure that contains an array of structures. When executed, the
following code throws an ArgumentExcepti on with a description “Type
ErrorInjectionB uffer can not be marshaled as an unmanaged structure; no
meaningful size or offset can be computed.� I have also included snippets
from the .H file. Any assistance would be greatly appreciated.

[busapi.h] (partial)
#if defined(__WIN32 __)
#include <windows.h>
#define CCONV _stdcall
#define NOMANGLE
#endif

#define BT_U16BIT unsigned short
#define BT_U8BIT unsigned char
#define BT_UINT unsigned int
#define BT_INT int

#define EI_COUNT 33 /* Number of error injection words supported by SW */
/* The HW supports one more, for the 33rd data word*/

typedef struct api_eibuf
{
BT_U16BIT buftype; // error injection buffer type
struct
{
BT_U8BIT etype; // error code (e.g. EI_NONE, EI_TWOBUS, etc)
BT_U8BIT edata; // error data (if req'd)
}
error[EI_COUNT];
}
API_EIBUF;

NOMANGLE BT_INT CCONV BusTools_EI_Ebu fRead(
BT_UINT cardnum, // (i) card number (0 - based)
BT_UINT errorid, // (i) number of error injection buffer to read
API_EIBUF * ebuf); // (o) pointer to resulting buffer values

NOMANGLE BT_INT CCONV BusTools_EI_Ebu fWrite(
BT_UINT cardnum, // (i) card number (0 - based)
BT_UINT errorid, // (i) number of error injection buffer to write
API_EIBUF * ebuf); // (i) pointer to buffer values to be written to
HW

[C#]
using System;
using System.Runtime. InteropServices ;

namespace ConsoleApplicat ion1
{
class Class1
{
[DllImport(@"bus api32.dll", EntryPoint = "BusTools_EI_Eb ufRead")]
public static extern int BusTools_EI_Ebu fRead(
uint cardnum,
uint errorid,
[MarshalAs(Unman agedType.LPStru ct)]
ref ErrorInjectionB uffer ebuf
);

[DllImport(@"bus api32.dll", EntryPoint = "BusTools_EI_Eb ufWrite")]
public static extern int BusTools_EI_Ebu fWrite(
uint cardnum,
uint errorid,
[MarshalAs(Unman agedType.LPStru ct)]
ref ErrorInjectionB uffer ebuf
);

[STAThread]
static void Main(string[] args)
{
Console.WriteLi ne("SizeOf(stru ct ErrorInjectionB uffer) = " +
Marshal.SizeOf( typeof(ErrorInj ectionBuffer)). ToString()); // Throws
ArgumentExcepti on
}
}

[Serializable]
[StructLayout(La youtKind.Sequen tial)]
public struct ErrorInjectionB uffer
{
private const int ErrorInjectionC ount = 33;

private ushort bufferType;
[MarshalAs(Unman agedType.ByValA rray, SizeConst = ErrorInjectionC ount)]
private ErrorInjectionD ata[] errors;
}

[Serializable]
[StructLayout(La youtKind.Sequen tial)]
public struct ErrorInjectionD ata
{
private byte eType;
private byte eData;
}
}

[Mattias Sjögren]

Daniel,

See if this helps

http://www.dotnetinterop.com/faq/?q=...ithStructArray

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Daniel Brown]

There are 33 elements in the array. Other than flattening the array, is
there another way?

"Mattias Sjögren" wrote:

Daniel,

See if this helps

http://www.dotnetinterop.com/faq/?q=...ithStructArray

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Mattias Sjögren]

Daniel,

There are 33 elements in the array. Other than flattening the array, is
there another way?

Since the nested struct in this case is just two bytes, you could
replace the array with a ushort[], and then manually extract the high
and low bytes (eData and eType respectively) from each ushort value.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
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[Daniel Brown]

Do you know if this functionality will be addressed in .NET 2.0?

"Mattias Sjögren" wrote:

Daniel,

There are 33 elements in the array. Other than flattening the array, is
there another way?

Since the nested struct in this case is just two bytes, you could
replace the array with a ushort[], and then manually extract the high
and low bytes (eData and eType respectively) from each ushort value.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Willy Denoyette [MVP]]

No it won't. Simply because a generic marshaller cannot handle all possible
mappings between unmanaged data structures and managed object lay-outs.
Note also that the CLR and the managed languages weren't designed for this
kind of operability with legacy C style data and code. If you need this
level of interop you should use managed C++ (or the upcomming CLI/C++) a
language that was designed for this.

Willy.

"Daniel Brown" <Da*********@di scussions.micro soft.com> wrote in message
news:AD******** *************** ***********@mic rosoft.com...

Do you know if this functionality will be addressed in .NET 2.0?

"Mattias Sjögren" wrote:

Daniel,

>There are 33 elements in the array. Other than flattening the array, is
>there another way?

Since the nested struct in this case is just two bytes, you could
replace the array with a ushort[], and then manually extract the high
and low bytes (eData and eType respectively) from each ushort value.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.