What is the best way to read an entire file into a std::string in C++?

This is an simple way to read an entire file into std::string in C++

Algorithm

Begin
   Take the filename as inputstream.
   Declare a string variable str.
   Read the file till the end by using rdbuf().
   Put the data into st.
   Print the data.
End.

Example Code

#include<iostream>
#include<fstream>
#include<sstream>
#include<string>
using namespace std;
int main() {
   ifstream f("a.txt");
   string str;
   if(f) {
      ostringstream ss;
      ss << f.rdbuf();
      str = ss.str();
   }
   cout<<str;
}

Input

a.txt data file contains the string “hi”

Output

hi