Accessing data from a .dll file

I am in need of reading/extracting some Initial values for the parameters from the DLL file.

Is there any possible ways to do that using m-script?

I am expecting something like extracting initial values of all Parameters and after getting that info,

I will be writing them down to a CSV file to get parsed at the startup.

Answer 1

[Rupesh]

Hi Shankar,

After going through your question, I assume that you need help with methods to read or extract initial parameter values from a DLL file using MATLAB scripts and then write those values to a CSV file.So basically, to extract initial parameter values from a DLL file using MATLAB (assuming you meant MATLAB by "m-script"), you would typically need to have a way to interface with the DLL. If the DLL provides functions to get these values, you can use MATLAB's "loadlibrary" and "calllib" functions to load the DLL and call its functions. Here's a general approach to the problem:

1. Define Paths: Specify the DLL (simpledll.dll) and header (simpledll.h) file paths using fullfile(pwd, 'filename'), ensuring they are in the current directory.
2. Load Library: Use "libisloade"d to check if the DLL is already loaded, and "loadlibrary" to load it with the header file for function signatures.
3. Retrieve Values: Call the "getInitialValue" function from the DLL using "calllib" within a loop to populate the initialValues array.
4. Write to CSV: Save the parameter indices and values to initial_parameters.csv using "writematrix" without headers and with comma delimiters.

Below is a sample example which shows how you can create a simple DLL and then how you would interact with it using MATLAB.

Step 1: Create a simple C DLL

% Here's an example of a simple C code that could be compiled into a DLL. 
% This example assumes you have a function that returns an initial value for a parameter based on its index.  

% // simpledll.c
#include <windows.h>

BOOL APIENTRY DllMain(HMODULE hModule,
                      DWORD  ul_reason_for_call,
                      LPVOID lpReserved) {
    switch (ul_reason_for_call) {
    case DLL_PROCESS_ATTACH:
    case DLL_THREAD_ATTACH:
    case DLL_THREAD_DETACH:
    case DLL_PROCESS_DETACH:
        break;
    }
    return TRUE;
}

__declspec(dllexport) double getInitialValue(int index) {
    double values[] = {1.0, 2.0, 3.0}; // Example initial values
    if (index < 0 || index >= sizeof(values) / sizeof(values[0])) {
        return 0; // Index out of range
    }
    return values[index];
} 

% To create a DLL from this code, you would compile it with a C compiler
% (like gcc or Visual Studio's compiler) with the appropriate flags to generate a DLL. 
% Here's an example using gcc (part of MinGW or Cygwin on Windows):

gcc -shared -o simpledll.dll simpledll.c -Wl,--add-stdcall-alias 

Step 2: Use the DLL in MATLAB

% Once you have the DLL, you would use [MATLAB's “loadlibrary”, “calllib”, and ' ...
%     'related functions to interact with it. Here's how you might do that:  


% main_script.m

% Define the path to the DLL and the header file
dllPath = fullfile(pwd, 'simpledll.dll'); % Replace with your actual DLL path
headerPath = fullfile(pwd, 'simpledll.h'); % Replace with your actual header file path

% Load the library
if not(libisloaded('simpledll'))
    [notfound, warnings] = loadlibrary(dllPath, headerPath, 'alias', 'simpledll');
    if ~isempty(notfound)
        error('The following functions were not found: %s', notfound);
    end
    if ~isempty(warnings)
        warning('There were warnings during the loading: %s', warnings);
    end
end

% Retrieve initial values
% The array 'values' in the C code has 3 elements, so we loop from 0 to 2
numParameters = 3;
initialValues = zeros(1, numParameters);

for index = 0:(numParameters - 1) % DLL is using 0-based indexing
    % Call the function from the DLL
    initialValues(index + 1) = calllib('simpledll', 'getInitialValue', index);
end

% Write the values to a CSV file
csvData = [(0:numParameters-1)', initialValues']; % Create a matrix with parameter indices and their initial values
csvFileName = 'initial_parameters.csv';
writematrix(csvData, csvFileName, 'Delimiter', ',', 'WriteVariableNames', false);

% Unload the DLL
unloadlibrary('simpledll');

Expected Code Ouput:

I have also attached my final excel output and sample c code which is used for execution, alongside you can refer to following documents for more information regarding cpp usage in MATLAB.

https://www.mathworks.com/help/matlab/call-cpp-library-functions.html

https://www.mathworks.com/help/matlab/ref/loadlibrary.html

https://www.mathworks.com/help/matlab/ref/calllib.html

Hope this helps!