MATLAB: How to extract string data from an input cell matrix in a MEX file

Question

I have created the following cell in MATLAB:

x = {'alpha' 'bravo' 'charlie';'Xray' 'yankee' 'Zulu'}

I would like to see a sample code for a MEX file to extract the contents of the cell in C or C++ environment.

Answer 1

The following C program shows one way to extract the cell contents:

 #include "mex.h"
 #include "string.h"
 void printArray(char charArray[])
 {
 int itr;
 int len = strlen(charArray);
 mexPrintf("The length of C array is %d \n", len);
 mexPrintf("The value of C array is %s", charArray);
 mexPrintf("\n--------------\n");
 }
 void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
 {
     const mxArray *cell_element_ptr;
     char* c_array;
     mwIndex i;
     mwSize total_num_of_cells, buflen;
     int status;
     /*Extract the cotents of MATLAB cell into the C array*/
    total_num_of_cells = mxGetNumberOfElements(prhs[0]);
    for(i=0;i<total_num_of_cells;i++){
    cell_element_ptr = mxGetCell(prhs[0],i);
    buflen = mxGetN(cell_element_ptr)*sizeof(mxChar)+1;
    c_array = mxMalloc(buflen);
    status = mxGetString(cell_element_ptr,c_array,buflen);
    mexPrintf("The length of cell element %d is: %d \n", i, strlen(c_array));
    printArray(c_array);
    mxFree(c_array);
 }
 mexPrintf("Success\n");
 }

To use the above MEX file, execute the following commands in MATLAB:

mex -v extractCellMatrix.c       % Compiles the MEX file
x = {'alpha' 'bravo' 'charlie';'Xray' 'yankee' 'Zulu'}    % Creates the cell matrix
extractCellMatrix(x)                 % Pass the cell array to the MEX function