How to send UTF std::string back to Matlab?

class MexFunction : public matlab::mex::Function {

public:

void operator()(matlab::mex::ArgumentList outputs, matlab::mex::ArgumentList inputs)

{

ArrayFactory factory;

matlab::data::CharArray string1 = inputs[0];

plist_file = string1.toAscii();

std::string json_str = convertToJson(plist_file);// this function reads the file and returns the json string

matlab::data::CharArray str_json = factory.createCharArray(json_str);

outputs[0] = str_json;

}

};

This fails at Matlab execution , says only ascii characters allowed , which i understand why .

Answer 1

[Harsh Mahalwar]

Hi Rakesh,

From what I can gather, you are trying to send std::string (UTF-8) from C++ to MATLAB and getting an exception saying, “Input data can only contain ASCII characters”.

Here’s a workaround to send std::string (UTF-8) from C++ to MATLAB:

#include "mex.h" 
#include <string>

void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) { 
    // Sample UTF-8 string 
    std::string utf8String = u8"サンプル文字列"; // Translates to : "Sample String"
    // Convert std::string to C-style string 
    const char *cStr = utf8String.c_str(); 
    plhs[0] = mxCreateString(cStr); 
} 

(file name: sendingUTF8.cpp)

After saving sendingUTF8.cpp run the following command in the MATLAB terminal:

(output on successful compilation)

After successfully compiling sendingUTF8.cpp you can run the following command to display the UTF-8 string received from C++:

disp(sendingUTF8); 

(string successfully displayed in MATLAB, translates to "Sample String")

I hope this helps, thanks!