How to link a wrapper DLL to the target DLL

Question

I appreciate your help!
Question:
In my project, I need to deal with a hybrid programming of C++ and Labview. The C++ part has been encoded into a DLL, which aims to do a complex mathematics. The main function in the DLL has the following form:
                          float RateEqCalculate(class CLaserPulse *Pulse, class CMaterial *Material, class CThresh *ThreshPara, class CRateResults &r);
The four arguments are all of the class type. The first three arguments are used to input parameters to the function and the last one is used to record the process of computation. For example: class CLaserPulse is composed by several numerics and two functions as the following form:
class CLaserPulse
public:
 float fDuration;  
 float fWave;  
 float fNA;   
 float fRefrIndex;                                     // Refractive Index
 float fAbsCoeff;                                     // Absorption coefficient [1/m]
 CLaserPulse();
 virtual ~CLaserPulse();
 virtual double Shape(double dTime);       // gives Temporal Shape
 float SpotDiameter();                            // Calculate Spotdiameter
As in labview "class" cannot be accepted as an argument of the "Library Function Node" directly, a wrapper DLL is required to translate the "class" to the type labview can understand. The following link is a good illustration of this process. http://labviewwiki.org/DLL/shared_library Given the argument class CLaserPulse has been converted into the wrapper DLL by the method from the link, how can I later link this wrapper DLL to the target DLL. My understanding is like this:
                                                                                             Target DLL
                                                                                float RateEqCalculate(
  class CLaserPulse  ->   wrapper DLL       .........linking.........        class CLaserPulse,
  class CMaterial      ->   wrapper DLL       .........linking.........        class CMaterial,
  class CThresh        ->   wrapper DLL       .........linking.........        class CThresh ,
  class CRateResults  ->   wrapper DLL     .........linking.........        class CRateResults );
Am I right? Four wrapper DLL to four class type arguments?
Many thanks!!!

Answer 1

Hello Rolf and Christian: 
Thank you for your suggestions! I'm now working on it. I appreciate your continuous help!! 
I'll briefly summarize my question here:
In the original DLL, which is compiled by VC++ 6.0 and named RateEquation.dll, three class types (CLaserPulse, CMaterial& CThresh) are inclueded to do parameter exchanges; one class type is designed to save the calculation results(CRateResults);one main function to do the calculation and save the results as following form:  
 float RateEqCalculate(class CLaserPulse*, class CMaterial*, class CThresh*, class CRateResults &r); 
My question now is the initialization of the struct type and the communication between this type with labview. 
I'll take class CMaterial as an example to show how I made it into wrapper DLL.Original class CMaterial is defined as following:
class CMaterial
public:
 float AbsorberGap;
 float BandGap;
 float CollTime;
 float ElDensity; float RefractiveIndex; 
 float AbsorptionCoeff;  
 float MoleculeMass;  
 float Density;  
 float HeatCapacity;  
 float HeatConductivity;  float TAmbient;  
 CMaterial();
 virtual ~CMaterial();
  In a wrapper dll it's like this: 
WrapperDll.h
 extern "C" { /*using a C compiler*/            //Using a C compiler to write the wrapper DLL
#endif 
struct RATEEQUATION_API CMaterial{                  
  //Electronical properties
  float AbsorberGap;
  float BandGap;
  float CollTime;
  float ElDensity;
  //Optical properties
  float RefractiveIndex;
  float AbsorptionCoeff;
  //Other properties
  float MoleculeMass;
  float Density;
  float HeatCapacity;
  float HeatConductivity;
  float TAmbient;
  typedef struct CMaterial CMaterial;                                             /* make the class opaque to the wrapper*/
 RATEEQUATION_API CMaterial* creat_CMaterial(void);           
RATEEQUATION_API void destroy_CMaterial(CMaterial* LV_ref);
#ifdef __cplusplus
#endif  
WrapperDll.cpp
RATEEQUATION_API CMaterial* creat_CMaterial(void)
       return new CMaterial();                              
RATEEQUATION_API void destroy_CMaterial(CMaterial* LV_ref)
       delete LV_ref;
 In function creat_CMaterial(), one can see the constructor of class CMaterial is called. As struct type CMaterial has the same memory layout as class type CMaterial, so it’s safe and possible to return a class CMaterial* to struct CMaterial* and it’s initialized by the default values in the class constructor. Now I’m confused by how one communicates between labview and struct CMaterial. For example, if I would like to change the parameter _CMaterial-> BandGap=6.5eV to 8eV. How to make it? My feeling is I need a cluster type from Labview as an input in the function creat_CMaterial:
                          CMaterial* creat_CMaterial(cluster_LV*)
Many thanks!
Message Edited by Kuo on 09-15-2009 09:56 AM
Message Edited by Kuo on 09-15-2009 09:59 AM