C++ Call conversion

[bclegg]

Hi,
I am a VB.net programmer who has to make use of a 3rd party Borland C++ dll.

We have a successful VC++ wrapper that presents a number of functions
that can be declared and called in VB.net

I now want to translate the wrapper to C#.
I can find my around C# in a (pardon the pun) basic fashion.

I am looking to translate the Main routine below.
I am at the first stage of emulating getting the pointer from LoadLibrary.

I have successfully used:
[DllImport ("KERNEL32.DLL" )]
public static extern long LoadLibrary(str ing lpLibFileName);

This passed back a large number when I fed it the dll name and it
passed back a smaller number when I fed a nonexistent name.

But the C++ code below gets a null back when passed a nonexistent name
so I figured I had to use a HINSTANCE like the C++ .

This led me to use a module and marshal.getHins tance
But I can't see how to assign the module to the dll I am interested in.

public long bcLoadLibrary(s tring Library)
{

long lngResult;
Module m;
//m.Name=Library; /READONLY!!

IntPtr p = new IntPtr(0);
p=Marshal.GetHI NSTANCE(m);

lngResult=(long )p;
return lngResult;
}
Am I close or deep in the weeds?
Thanks
Bob
The C++ Code snippet is

HINSTANCE pScadaDll;
TfAttach dllAttach;
TsSimAPIFuncs *pMainDllRec = NULL;
BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_c all, LPVOID
lpReserved)
{
DWORD dwResult = 0;
switch (ul_reason_for_ call)
{
case DLL_PROCESS_ATT ACH:
pScadaDll = LoadLibrary("Th eDLL.dll");
if(pScadaDll != NULL)
{
char sMsg[500];
wsprintf(sMsg, "attached TheDLL.dll Result: ");
MessageBox(NULL , sMsg, "Success", MB_OK);
dllAttach = (TfAttach)GetPr ocAddress(pScad aDll, "_dll_Attac h");

[Mattias Sjögren]

Bob,

I have successfully used:
[DllImport ("KERNEL32.DLL" )]
public static extern long LoadLibrary(str ing lpLibFileName);

This passed back a large number when I fed it the dll name and it
passed back a smaller number when I fed a nonexistent name.
You should use IntPtr as the return type, not long.

BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_c all, LPVOID
lpReserved)
{
DWORD dwResult = 0;
switch (ul_reason_for_ call)
{
case DLL_PROCESS_ATT ACH:
pScadaDll = LoadLibrary("Th eDLL.dll");

The DllMain docs says explicitly that you must not call LoadLibrary
from within DllMain.

Mattias

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

[Jeffrey Tan[MSFT]]

Hi bclegg,

Thank you for posting in the community!

Based on my understanding, you meet the problem of P/invoke LoadLibrary in
C#.

=============== =============== ==
Actually, the return type of LoadLibrary is HMODULE, which in .Net you
should marshal it as IntPtr. So you should declare it as:
[DllImport ("KERNEL32.DLL" )]
public static extern IntPtr LoadLibrary(str ing lpLibFileName);

But, use long as the return value will not cause serious problem.(Becaus e
IntPtr is also a long type internally)

Use LoadLibrary with a nonexisted file name, the return value should be
null, which should be 0 in IntPtr.(I have tested this for you), so I can
not understand why your return value is only a "smaller number". Is the
"small number" 0?

Also, where is the main concern of you?

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

[bclegg]

Hello Mattias,
Thank you for your reply.
At the risk of continuing this discussion offthread,
Could you please advise where the pScadaDll = LoadLibrary("Th eDLL.dll");
should be placed.
ie Is acceptable to make a subroutine call at this point which does it
or should the C++ DLL present a 'Connect' function to the interface.
Regards
Bob

Mattias Sjögren wrote:

Bob,

I have successfully used:
[DllImport ("KERNEL32.DLL" )]
public static extern long LoadLibrary(str ing lpLibFileName);

This passed back a large number when I fed it the dll name and it
passed back a smaller number when I fed a nonexistent name.

You should use IntPtr as the return type, not long.

BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_c all, LPVOID
lpReserved)
{
DWORD dwResult = 0;
switch (ul_reason_for_ call)
{
case DLL_PROCESS_ATT ACH:
pScadaDll = LoadLibrary("Th eDLL.dll");

The DllMain docs says explicitly that you must not call LoadLibrary
from within DllMain.

Mattias

[bclegg]

Hello Jeffery,
Thanks for your reply.

Your declaration works!

My main concern is that we have to interact with a
3rd party dll which uses a pointer as the way in.
ie. result = pointer-> SomeFunction

One of our programmers wrote a C++ wrapper which presents the functions
at the interface in a declarable manner.
ie.
Declare Sub SomeFunction Lib "D:\thepath\The DLL.dll"

I would like to move this functionality into C# and present the
functions via a C# component that doesn't have to call the C++ wrapper.

Thanks
Bob
Jeffrey Tan[MSFT] wrote:

Hi bclegg,

Thank you for posting in the community!

Based on my understanding, you meet the problem of P/invoke LoadLibrary in
C#.

=============== =============== ==
Actually, the return type of LoadLibrary is HMODULE, which in .Net you
should marshal it as IntPtr. So you should declare it as:
[DllImport ("KERNEL32.DLL" )]
public static extern IntPtr LoadLibrary(str ing lpLibFileName);

But, use long as the return value will not cause serious problem.(Becaus e
IntPtr is also a long type internally)

Use LoadLibrary with a nonexisted file name, the return value should be
null, which should be 0 in IntPtr.(I have tested this for you), so I can
not understand why your return value is only a "smaller number". Is the
"small number" 0?

Also, where is the main concern of you?

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

[Jeffrey Tan[MSFT]]

Hi Bob,

Based on my understanding, your dll may use some functions that is inside
another dll, so you want to load that dll for use.

I think you should specify a variable for determine the loading of that
dll, when you want to use the functions, you can judge the variable, if the
dll is not loaded, then you can load that dll. Through this way, you have
delayed the loading of the dll until your dll is initialized probably.

Thanks.

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

[bclegg]

Thank you for your reply.
I have altered the C++ wrapper.
Regards
Bob
Mattias Sjögren wrote:

Bob,

I have successfully used:
[DllImport ("KERNEL32.DLL" )]
public static extern long LoadLibrary(str ing lpLibFileName);

This passed back a large number when I fed it the dll name and it
passed back a smaller number when I fed a nonexistent name.

You should use IntPtr as the return type, not long.

BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_c all, LPVOID
lpReserved)
{
DWORD dwResult = 0;
switch (ul_reason_for_ call)
{
case DLL_PROCESS_ATT ACH:
pScadaDll = LoadLibrary("Th eDLL.dll");

The DllMain docs says explicitly that you must not call LoadLibrary
from within DllMain.

Mattias

[Jeffrey Tan[MSFT]]

Hi bclegg,

Thanks very much for your feedback.

If you have any further concern, please feel free to feedback. We will help
you.

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

[Bob Clegg]

Hello Jeffery,
Thanks again,
I have just have one further question if I may.
The 3rd party dll comes with a C++ header file that has some type
definitions that I can't see how to convert to C#

eg typedef void (*Tfsa_SetCurDa tabase)(const char *prmDatabase);

Once it declares a number of these it then declares a struct containing
them.
One entry from which is
Tfsa_SetCurData base SetCurDatabase;

The struct is then exposed along with a function for version checking.
typedef bool __declspec(dlle xport) (*TfAttach)(TsS imAPIFuncs
**prmSimAPIFunc s, const char *prmVersion);

extern TsSimAPIFuncs simAPI;

The C++ wrapper's global variables and connecting call are :
HINSTANCE pDll;
TfAttach dllAttach;
TsSimAPIFuncs *pMainDllRec = NULL;

void WTS_API LoadDLL()
{
DWORD dwResult = 0;
pDll = LoadLibrary("Th eDLL.dll");
if(pDll != NULL)
{

dllAttach = (TfAttach)GetPr ocAddress(pDll, "_dll_Attac h");
if(dllAttach != NULL)
{
if(!dllAttach(& pMainDllRec, CONST_API_VERSI ON))
...
AND away we go, either error handling or successfully exiting. If a
successful exit then the wrapper
dereferences pMainDllRec to get to the various functions in the struct.
eg
void WTS_API SetCurDatabase( const char *prmDatabase)
{
pMainDllRec->SetCurDatabase (prmDatabase);
}

My questions are:
1) Can I emulate these parameterised typedefs in C#
2) If so would you be able to show me how to write the equivalent
GetProcAddress.
regards
Bob Clegg

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[Mattias Sjögren]

Jeffrey,

But, use long as the return value will not cause serious problem.
I think getting bogus return values is a pretty serious problem, and
that's usually the result if you incorrectly use long as the return
type.

(Because IntPtr is also a long type internally)

Not on Win32 it isn't.

Mattias

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