error parsing character å

[mikelaltadi]

Hello!
Im having a trouble parsing a std::string that contains this character. å
I see it with decimal value of -27 in a array of chars.
And the nlohmann::json::accept
and
nlohmann::json::parse function
gives me an error
error_message = "invalid string: ill-formed UTF-8 byte";

But, if the character is in a std::string , should be valid isn´t it?

Environment: Windows 10 and Microsoft Visual Studio 2015

In this page, that validates UTF-8 , says that å is a correct UTF-8 character.
https://onlineutf8tools.com/validate-utf8

[nickaein]

This library does supports UTF-8, even with std::string. Are you sure your string encodes characters correctly? For starters, you might take a look at notes at characters encoding.

If that string is a string literal hardcoded in the source code file, you might want to make sure your source code file encoding is in UTF-8. If you are reading it from a file, check the encoding of that file and make sure it is UTF-8.

[mikelaltadi]

char mess[3000]="{"machine.serialnumber":"G4åd"}";

std::string s = mess;

bool validated = nlohmann::json::accept(s);

nlohmann::json::parse(s);

This is the code that produces exception.

[nickaein]

Shouldn't you skip the double-quotes (e.g. by putting \ before every " in string)? Can you print it out to console to see if it is correct?

Also, you should probably make sure your source file is being saved in UTF-8 encoding, not some others (e.g. ASCII, UTF-16).

To be able to easier to track down the issue, you can test the following code. Put the JSON in a separate file named input.json and make sure it is in UTF-8 encoding (Windows is not that UTF-8 friendly and usually defaults to ASCII or UTF-16).

#include <fstream>
#include <sstream>
#include <string>
#include <iostream>
#include "json.hpp"

using namespace std;

int main() 
{
    std::ifstream fin("input.json");
    if(!fin)
    {
        cout << "Failed to open file." << endl;
        return 1;
    }

    std::stringstream stream;
    stream << fin.rdbuf();   
    std::string json_string = stream.str();

    cout << "File contents:"  << endl;
    cout << json_string << endl << endl;

    bool validated = nlohmann::json::accept(json_string);
    cout << "Json validation result: " << validated << endl;

    auto json = nlohmann::json::parse(json_string);

    cout << "machine.serialnumber: " << json["machine.serialnumber"] << endl;
    
    return 0;
}

I have tested it and it outputs the following as expected:

File contents:
{"machine.serialnumber":"G4åd"}

Json validation result: 1
machine.serialnumber:"G4åd"

If this solved your issue, you should compare the string you had in your code to json_string in this code example to see where it differs. My guess is either you didn't skipped your string literal correctly or the encoding of the source code file is not UTF-8.

[nlohmann]

@mikelaltadi Do you need further assistance?

[mikelaltadi]

No. I replace this letter by ‘a’ when I find it before parsing. Its enough for me. Thanks.