Create DLL wrapper in C code for Matlab/LabView interfacing

Question

I want to build with Matlab Compiler SDK a DLL that can be called from LabView. As you may know, the library generated by the Matlab Compiler SDK (lets call it 'my_dll.dll'/'my_dll.lib') is not directly callable by LabView, as it uses non-standard data types ( mxArrays ).

Thus, my plan is to generate in C a wrapper code. This wrapper code, whenever it is called, will execute the needed routines of the Matlab Runtime Engine and call the functions generated in 'my_dll.dll'. This wrapper code would be basically extremely similar to any other executable or application using the previously generated DLL, following the guidelines of this.

Code example:

int main(double *input){

    /* Call the mclInitializeApplication routine. Make sure that the application
 * was initialized properly by checking the return status. This initialization
 * has to be done before calling any MATLAB API's or MATLAB Compiler SDK generated
 * shared library functions. */

   mclmcrInitialize();

   if( !mclInitializeApplication(NULL,0) )
   {
       fprintf(stderr, "Could not initialize the application.\n");
       return -1;
   }

return mclRunMain((mclMainFcnType)wrapper_main,0,NULL);

}


double wrapper_main(int argc, char **argv) {

//declare variables
double *out; // Here my output will be stored
double number = 16; // This is the input number

// Initialise library
dll_layer1Initialize();

//Create two pointers of mxArray type to store inputs and outputs
mxArray *in1_ptr;
mxArray *out1_ptr = NULL;

//Allocate input pointer to a 1 by 1 double, real matrix
in1_ptr = mxCreateDoubleMatrix(1, 1, mxREAL);

//Move the data from the input to the pointer
memcpy(mxGetPr(in1_ptr), &number, 1 * sizeof(double));

//Pass values to mlfFoo and receive in mxArray type variable
//mlfFoo is my matlab function. In this case it only performs
//the square root of the input number.
mlfFoo(1, &out1_ptr, in1_ptr);

out = mxGetPr(out1_ptr);

printf("\n Result is: %f", *out);

//Terminate foo implementation
dll_layer1Terminate();
mclTerminateApplication();

return 0;
}

However, in order to call this C wrapper code from LabView, I would have to generate a new DLL, and here comes the problem, since I do not find the way to do this. The following picture summarizes what I want to do.

Things that I have tried:

1 - Compile the C wrapper code and my_dll.lib to generate a wrapper.dll with the Matlab Compiler SDK 'mbuild' command. This only creates an executable, but not a dll. Maybe I am missing something.

2 - Use Visual Studio to create the DLL. The problem I am facing here is that when I am going to build the project it gives me plenty of errors, like:

Error LNK2019 unresolved external symbol _mclRunMain_proxy referenced in function "public: static double __cdecl Wrapper::Functions::wrapper_sqrt(double)" (?wrapper_sqrt@Functions@Wrapper@@SANN@Z) Win32Project1 ...\visual studio 2015\Projects\Win32Project1\Win32Project1\wrapper.obj 1

Maybe my error here is that I am not properly linking the Matlab libraries, in which case I do not know how to fix it.

Other possibilities to run Matlab code in LabView is the use of MathScript node, Matlab Script node or Matlab Coder(for creating also a DLL) however, I am discarding those options for several other reasons.

Thank you beforehand for your help.

It is better to generate C code from Matlab and than link & compile your wrapper code together with the Matlab-generated C code into a single DLL, which you than call from LabVIEW. You may need to link some Matlab-specific header functions to make this run (but the compiler will complain;) ) — max

slacker slacker · Accepted Answer · 2017-11-01T13:48:27

0

votes

For attempt #2 did you add the reference to the matlab dll in your project?

Create DLL wrapper in C code for Matlab/LabView interfacing

1 Answers