Transmit a Structure from MATLAB to C

Hello everyone. I want to transmit a MATLAB structure to C. Like:

a.para1=1;

a.para2=2;

...

In my C code, I want to use these parameters to do my futher work. The current code I used is

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

double *pointerlhs, *pointerrhs[2]; /* pointer to real data in new array */

mwSize index;

/* Check for proper number of arguments. */

if (nrhs != 1) {

mexErrMsgTxt("This function takes one input arguments.");

}

/* Create an m-by-n mxArray; you will copy existing data into it */

plhs[0] = mxCreateNumericMatrix(1, 2, mxDOUBLE_CLASS, mxREAL);

//pointerrhs[1] = mxGetPr(prhs[0]);

pointerlhs = mxGetPr(plhs[0]);

/* Copy data into the mxArray */

for (index = 0; index < 2; index++) {

pointerrhs[index]= mxGetPr(prhs[index]);

pointerlhs[index] = *pointerrhs[index];

}

return;

}

which meed to tramsmit the value of the structure one by one like:

Transmit_Function(a.para1,a.para2...)

How can I get all parameters in a structure while just use one input in my MATLAB code. Like:

Transmic_Function(a)

Then I can get and use all the paramters in a.

Thanks.

Answer 1

[Ziyu Hua]

This can be realized by MATALB C API function "mxGetField"

#if !defined(_WIN32)

#define dgesv dgesv_

#endif

#include "mex.h"

#include"matrix.h"

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

{

if (mxIsStruct(prhs[0]))

{

double *pointer, *pointerrhs;

mxArray *StructValue = mxGetField(prhs[0], 0, "a");

plhs[0] = mxCreateNumericMatrix(1, 1, mxDOUBLE_CLASS, mxREAL);

pointer = mxGetPr(plhs[0]);

pointer[0] = *(mxGetPr(StructValue));

}

else

{

mexErrMsgTxt("The Input is Not a Struct");

}

}

[James Tursa]

This will not work. The variable name is "a", but the field names are "para1" and "para2". You need to use the field names in your mxGetField( ) call, not "a". Also your code is overly complicated and does not contain argument checking so it will crash with invalid inputs.