Const char into mex files

Hello,

I'd like to know how can I export my Matlab strings to use them whitin a MEX file, as it follows. I'm quite new using MEX files and I'd really appreciate any help

I have in matlab this variable

folder = 'C:\Users\Jorgue Guerra\Desktop\Sample_1'

then I want to export that value to use in C, I've tried something like this.

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

   const char *folder= (const char)mxGetData(prhs[0])
   //.....other code using folder var
  }

I know it can't be as simple as that, but I have no clue where to begin

[Walter Roberson]

At the very least it would have to be

     const char *folder= (const char *)mxGetData(prhs[0]);

because mxGetData returns a pointer, not a character.

[James Tursa]

Even this won't work, because MATLAB char data is 2-bytes per character, whereas C char data is 1-byte per character. So you need something like the mxArrayToString API function to do an actual allocation + copy. Or one could use this to access the MATLAB char data manually:

     const unsigned short *folder= (const unsigned short *)mxGetData(prhs[0]);

Answer 1

[Jorge Mario Guerra González]

I solved it by myself.

If anyone is in trouble with this the answer is given in this page

http://www.mathworks.com/help/matlab/matlab_external/passing-strings_btgcjh1-2.html

[James Tursa]

FYI, that link is a bit misleading. The memory for output_buf does not become part of the plhs[0] output as a result of the mxCreateString call, so it should in fact be released just like the memory for input_buf is released. I.e., this line should appear at the end of the code:

mxFree(output_buf);