MATLAB: How to write a MATLAB MEX-file that requires the name of an mxArray now that the mxGetName function is deprecated

cdeprecatedlibrarymathMATLABmexmex filemexgetvariablemxarraymxgetnamewrite

I am writing a MEX-file application that writes a MATLAB variable to a proprietary file and uses the original variable name (name of the mxArray in the MATLAB workspace) as an identifier in the file structure. Now that the mxGetName function is deprecated, I can no longer get the variable's name for writing to the file.

Best Answer

To work around this problem, you must pass the variable name as a string argument to the MEX function. This way there would not be any need to get the variable's name in the MATLAB workspace. And the data can be copied from the MATLAB workspace using the mexGetVariable function.

Therefore, if for instance you previously called the MEX function by passing a variable:

sampleMEX(A);

You can modify your MEX-file so that you now pass the variable name as a string:

sampleMEX('A')

Then to get the data into the MEX file, you can use the mexGetVariable function:

mxArray *data = mexGetVariable("caller", mxArrayToString(prhs[0]));

Related Solutions

MATLAB: Building Mex file with Fortan

Your main problem is that you need to create the output array PLHS(1) before you access it. Also your NLHS and NRHS types are wrong. Try this:

#include <fintrf.h>
C
C Gateway routine
C
    SUBROUTINE MEXFUNCTION(NLHS, PLHS, NRHS, PRHS)
    implicit none
C mexFunction arguments:
    MWPOINTER PLHS(*), PRHS(*)
    INTEGER NLHS, NRHS
    mwPointer, external :: mxGetPr, mxGetPi
    mwPointer, external :: mxCreateDoubleMatrix, mxCreateNumericArray
    mwSize, external :: mxGetM, mxGetN
    MWPOINTER YPP 
    mwSize M, N
    integer*4 ComplexFlag
    REAL *8 RYPP(1)
    RYPP(1) = 10
    M = 1
    N = 1
    ComplexFlag = 0
    PLHS(1) = mxCreateDoubleMatrix( M, N, ComplexFlag )
    YPP = MXGETPR(PLHS(1))
    CALL MXCOPYREAL8TOPTR(RYPP, YPP, M*N)
    RETURN
    END

MATLAB: What should I replace ‘mxGetName’ with

Variable name strings used to be a part of the mxArray itself. However, that hasn't been the case for several years now. There is no easy way to recover the name of the passed variable other than to use mexCallMATLAB with "whos" and do an exhaustive search for the variable mxArray address to discover its name in the caller's workspace. So, you can either do that, or just drop that part of the test completely out of your mex code.

EDIT

If you really think you need this functionality, you could use the following function. The difference for this function compared to the original is that this function returns a pointer to dynamically allocated memory, so you might want to mxFree( ) it (or allow MATLAB to garbage collect it).

char *mxGetName(const mxArray *mx)
{
    mxArray *lhs[1];
    mxArray *cell;
    size_t i, n;
    char *varname;
      varname =  (char *) mxMalloc(65);
      if( mx ) {
          mexCallMATLAB(1,lhs,0,NULL,"who");
          n = mxGetNumberOfElements(lhs[0]);
          for( i=0; i<n; i++ ) {
              cell = mxGetCell(lhs[0], i);
              mxGetString(cell, varname, 65);
              if( mx == mexGetVariablePtr("caller", varname) ) {
                  mxDestroyArray(lhs[0]);
                  return varname;
              }
          }
          mxDestroyArray(lhs[0]);
      }
      varname[0] = '\0';
      return varname;
  }

Best Answer

Related Solutions

MATLAB: Building Mex file with Fortan

MATLAB: What should I replace ‘mxGetName’ with

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