How to get file names in a folder, when using C/C++ Code Generation

Hi! My code needs to get all bmp image file names in a folder , and convert it to C++ dll by Matlab Coder. Unfortunately, Matlab Coder is not support the dir function . I want to find a replacement method to get all bmp file names in a folder and also can be used in Matlab Coder.

Thanks a lot!

Answer 1

[Jinal]

Hello Guan,

As per my understanding, you want to generate C/C++ code from your MATLAB code that lists the names of all BMP files present in a folder.

At present, functions such as “dir” and “ls” are not supported by MATLAB Coder for C/C++ code generation.

Any of the following workarounds can be used to include functions not supported by MATLAB Coder:

1) Use “coder.extrinsic” to call the unsupported functions. “coder.extrinsic” declares function as an extrinsic function. The code generator uses the MATLAB® engine to execute the call.

Please find below a sample workflow to list BMP files present in a folder:

• Create a local function called “bmplist” as follows.

Create a local function called “bmplist” as follows.
function fn = bmplist(folderpath)
    coder.extrinsic("dir");
    coder.extrinsic("cd");
    cd(folderpath);
    fn = dir('**/*.bmp');
end

• Generate MEX code for “bmplist” by typing the following command.

codegen bmplist -args {"hi"}

• Call the generated MEX code.

bmplist(folderpath); 
%folderpath is the path to the folder in which BMP files are to be searched for

To know more about “coder.extrinsic”, please refer this link:

https://www.mathworks.com/help/coder/ref/coder.extrinsic.html

2) Write custom code for the unsupported functions.

3) Use “coder.ceval” to call custom C functions that replace the unsupported functions.

To know more about “coder.ceval”, please refer the following link:

https://www.mathworks.com/help/coder/ref/coder.ceval.html

Please refer the following link to know more about workarounds for using functions not supported for Code Generation:

https://www.mathworks.com/help/coder/ug/function-is-not-supported-for-code-generation.html

I hope this resolves the issue you were facing.