How to create a MEX file from a C++ function

Hello, I am currently working on a program that integrates C++, MATLAB, and a geochemical program. I am using the C++ code that they provided to act as a pipe between my main code, written in MATLAB and the geochemical program.

As of now, I have not been able to figure out how to compile the pipe, which I want to solely be a standalone function without a main(). I want it to act like any other MATLAB function. It takes in a few variables and then updates their values as it gets more information from the geochemical program.

So far, I have included:

#include "mex.h" #define printf mexPrintf

and

int main() { cout << "hello world" << endl; return 0; }

void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])

{

if( main() ) mexErrMsgTxt("main returned non-zero value");

}

in my code. Obviously the int main doesn't make too much sense, but without it's presence I don't know what I should include within the void mexFunction.

Any and all suggestions will be greatly appreciated. Thank you in advance!

Answer 1

[James Tursa]

Please post the interface to the C++ function you wish to include in the mex function. i.e., specify what the inputs and outputs are.

Answer 2

[Ilya]

[EDIT: 20110722 22:08 CDT - reformat - WDR]

Sorry for the delayed response. Here is the code in C++

/* 
   INPUT: mass_W, mass_S, density, activity, time_step, temp
   OUTPUT: mass_W, mass_S, density, activity
*/

#include "mex.h"
#define printf mexPrintf
#include "RC_helper.h"
#include <iostream>
#include <string>
#include "RC_helper.cpp"

using namespace std;

void pipe(double &mass_W, double &mass_S, double &density, double &activity, string time_step, string temp)
{

/**************************************************************/
/************************ Code for GWB ************************/
/**************************************************************/

char* script1[] = 
{
    "reset",
    "temperature = 7",
    "swap e- for O2(aq)",
    "swap CO2(g) for HCO3-",
    "1 free kg H2O",
    "13.05 pe",
    ".006 fugacity CO2(g)",
    "balance on H+",
    ".1 mg/kg H+",
    "230 mg/kg Cl-",
    "200 mg/kg Ca++",
    "243 mg/kg Mg++",
    "27 mg/kg K+",
    "447 mg/kg Fe++",
    "2000 mg/kg SO4--",
    "184 mg/kg Na+",
    "react -999.999 gram of H2O",
    "fix Eh",
    "fix fugacity of CO2(g)",
    "delxi = .0001 linear",
    "step_increase = 1",
    "go",
    ""
};

/**************************************************************/
/************************ Main Program ************************/
/**************************************************************/

     char line1[200];
     char discard[20];
     char** command1;
     Pipe pipe1("pipe1");

/* Interation Variable(s) */

     int i;

/* Two copies of react are opened */

     cout << "Open two copies of React." << endl;
     OpenGwbApplic(pipe1, "\\Program Files (x86)\\Gwb\\react.exe");

/* This for loops sets one dimension of the two dimensional array that is formed from the 
char pointers equal to the two pre-defined structures */

     for (command1 = script1, i = 0; **command1; **command1 ? command1++ : 0, i++) 
     {
      if (**command1){
          SendCommand(pipe1, *command1);
    }
     }

/**************************************************************/
/********************** Remaining Masses **********************/
/**************************************************************/

/* The remaining mass of water is reported */

     SendCommand(pipe1, "report Wmass H2O", line1, sizeof(line1));
     ReceiveLine(pipe1, line1, sizeof(line1));
     sscanf(line1, "%lg", &mass_W);

/* The density of the solution is reported */

     SendCommand(pipe1, "report soln_density", line1, sizeof(line1));
     ReceiveLine(pipe1, line1, sizeof(line1));
     sscanf(line1, "%lg", &density);

/* The activity of the water is reported */

     SendCommand(pipe1, "report Watact", line1, sizeof(line1));
     ReceiveLine(pipe1, line1, sizeof(line1));
     sscanf(line1, "%lg", &activity);

/* The mass of the solution is reported */

     SendCommand(pipe1, "report soln_mass", line1, sizeof(line1));
     ReceiveLine(pipe1, line1, sizeof(line1));
     sscanf(line1, "%lg", mass_S);

/* The react programs are closed */

     SendCommand(pipe1, "quit");

     printf("press return to exit> ");
     gets(discard);

/* The pertinent variables are returned */

return;
}

/* This is useless, but I don't know what to replace with it so and still account for the check done by the following function */

int main()
{
cout << "hello world" << endl;
return 0;
}

void mexFunction(int nlhs, mxArray *plhs[], int nrhs,
                 const mxArray *prhs[])
{
    if( main() )
        mexErrMsgTxt("main returned non-zero value");
}

Answer 3

[Ilya]

Anyone have any ideas?