CPP – Don’t append `\x00` to std::string

Record an experience of debugging.

Here are two ways to read string and store it in std::string.
One will have ‘\x00’ in std::string object, the other has not.

#include <iostream>
#include <vector>
#include <fstream>
#include <string.h>

using namespace std;

std::string filePath = "txt";

void WriteData()
{
    ofstream output;
    output.open( filePath.c_str(), ios::binary );
    if( output.is_open() == false )
    {
        cout << "open failed: " << filePath.c_str() << endl;
        return;
    }
    std::string str = "TX1";
    output.write( str.c_str(), str.size()+1);
    output.close();
    cout <<  "finished\n";
}

std::string cppStr;
void ReadData() {
    ifstream input;
    input.open(filePath.c_str(), ios::binary); // default way
    if (input.is_open() == false)
    {
        cout << "open failed: " << filePath << endl;
        return;
    }

//    std::string str;
//    str.resize(4);
//    str.reserve(4);
//    input.read( (char*)str.c_str(), 4 ); // append `\x00` for std::string

    char __str[10];
    input.read( __str, 4 );
    cppStr = __str; // std::string will remove `\x00`

    std::cout << "read str: " << cppStr << std::endl;
    input.close();
}

int main()
{
    WriteData();
    ReadData();
    std::cout << "cppStr: " << cppStr << std::endl;
    if( cppStr.back() == '\x00' )
    {
        std::cout << "this is a null binary string.\n";
    }

    return 0;
}