Is there a way to get values out of a map in a MATLAB mex file?

Question

I have a function that I'm writing as a MATLAB mex file. This function has to use MEX because it is interfacing with a piece of hardware in C++. There are a lot of options that can be set, and I would like to use a containers.Map to pass them. (Otherwise, I'd need a huge number of function parameters.)

I don't see any way of accessing the Map's operator that retrieves values using keys. I tried using mexCallMATLAB, but my various approaches failed. Is there a way to do this?

I thought maybe Map implemented this operator using subsref, but this fails in MATLAB, so I'm guessing the equivalent in a mex file would fail, too:

dict = containers.Map('foo', 3)
subsref(dict, struct('type', '.', 'subs', 'foo'))

Answer 1

Upvote for @nirvana-msu for getting me on the right track. Also, thanks to @horchler for suggesting that using a struct instead is a better idea. Here's how to access a containers.Map in C++ after making one in MATLAB with a field named foo:

#include <mex.h>

void mexFunction(int nlhs, mxArray *plhs[],
                 int nrhs, const mxArray *prhs[]) {
    mxArray *args[2];
    args[0] = const_cast<mxArray*>(prhs[0]);

    const char **fields = (const char **) mxCalloc(2, sizeof(*fields));
    fields[0] = "type";
    fields[1] = "subs";

    args[1] = mxCreateStructMatrix(1, 1, 2, fields);
    auto typeStr = mxCreateString("()");
    mxSetField(args[1], 0, "type", typeStr);
    auto mapKey = mxCreateString("foo");
    mxSetField(args[1], 0, "subs", mapKey);

    mxArray *output;
    mexCallMATLAB(1, &output, 2, args, "subsref");
    mexPrintf("%f\n", mxGetScalar(output));
    mxDestroyArray(args[1]);
    mxFree(fields);
}