Info Catalog octave: Working with Matrices and Arrays in Mex-Files octave: Mex-Files octave: Cell Arrays with Mex-Files

octave: Character Strings in Mex-Files

 
 A.2.3 Character Strings in Mex-Files
 ------------------------------------
 
 As mex-files do not make the distinction between single and double
 quoted strings that Octave does, there is perhaps less complexity in the
 use of strings and character matrices.  An example of their use that
 parallels the demo in ‘stringdemo.cc’ is given in the file ‘mystring.c’,
 as shown below.
 
      #include <string.h>
      #include "mex.h"
      
      void
      mexFunction (int nlhs, mxArray *plhs[],
                   int nrhs, const mxArray *prhs[])
      {
        mwSize m, n;
        mwIndex i, j;
        mxChar *pi, *po;
      
        if (nrhs != 1 || ! mxIsChar (prhs[0])
            || mxGetNumberOfDimensions (prhs[0]) > 2)
          mexErrMsgTxt ("ARG1 must be a char matrix");
      
        m = mxGetM (prhs[0]);
        n = mxGetN (prhs[0]);
        pi = mxGetChars (prhs[0]);
        plhs[0] = mxCreateNumericMatrix (m, n, mxCHAR_CLASS, mxREAL);
        po = mxGetChars (plhs[0]);
      
        for (j = 0; j < n; j++)
          for (i = 0; i < m; i++)
            po[j*m + m - 1 - i] = pi[j*m + i];
      }
 
 An example of its expected output is
 
      mystring (["First String"; "Second String"])
      ⇒ Second String
         First String
 
    Other functions in the mex interface for handling character strings
 are ‘mxCreateString’, ‘mxArrayToString’, and
 ‘mxCreateCharMatrixFromStrings’.  In a mex-file, a character string is
 considered to be a vector rather than a matrix.  This is perhaps an
 arbitrary distinction as the data in the ‘mxArray’ for the matrix is
 consecutive in any case.
 

Info Catalog octave: Working with Matrices and Arrays in Mex-Files octave: Mex-Files octave: Cell Arrays with Mex-Files