MATLAB: How to access an exported variable in a DLL

dllexportedMATLABmembervariable

I have complied DLL that I am able to use in a C++, and I would like to use it in MATLAB.
The C++ code utilizes GetProcAddress to access a structure that is exported by the library:
structPointer = (ext_struct*)GetProcAddress(myDLL, "exportedStructure");
Which we must later write some data to:
fscanf(input_data, "%d", &structPointer->a);
In MATLAB I am able to successfully load the library and can see the functions in the library using
loadlibrary(myDLL)
libfunctions(myDLL)
I would like an equivalent to the GetProcAddress which would allow me to access the member variable.

Best Answer

You can use the 'calllib' function to access exported variables in a shared library.

For example, if I have the following structure and exported variable in my library header file:

struct c_struct {
    double a;
    int b;
};
EXPORTED_FUNCTION struct c_struct exportedStruct;

And the c_struct variable 'exportedStruct' is defined in my library as:

struct c_struct exportedStruct = {1, 2};

Then I can access this structure from MATLAB as follows:

>> loadlibrary('myLibrary')
>> lp = calllib('myLibrary', 'exportedStruct')
>> lp.Value
ans = 
  struct with fields:

      a: 1
      b: 2

This will return a 'lib.pointer' object pointing to the variable, which you can then use to interact with the variable:

>> lp.Value
ans =    
    struct with fields:     
        a: 1
        b: 2
>> lp.Value.p1 = 2;
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