How to save hex representation of binary file into a std::string?

Question

I have used this solution (c++) Read .dat file as hex using ifstream but instead of printing it to std::cout I would like to save binary file's hex representation to a std::string

#include <fstream>
#include <sstream>
#include <iostream>
#include <string>
#include <iomanip>

int main(int argc, char** argv)
{
  unsigned char x; 

  std::ifstream fin(argv[1], std::ios::binary);
  std::stringstream buffer;

  fin >> std::noskipws;
  while (!fin.eof()) {
    fin >> x ; 
    buffer << std::hex << std::setw(2) << std::setfill('0') << static_cast<int>(x);
  }
  std::cout << buffer;
}

Printing to cout works but saving those contents to buffer and then trying to print it to cout prints garbage.

What am I missing?

Unrelated to your problem, but in almost all cases (including this one) doing `while (!fin.feof())` will not work as you expect. Instead do `while (fin >> x)`. — Some programmer dude, Jan 04 '16 at 15:58
Note: [`eof` considered harmful](http://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong). — molbdnilo, Jan 04 '16 at 16:05

score 4 · Accepted Answer · answered Jan 04 '16 at 15:56

4

You don't have a std::string; you have an std::stringstream. And you can't "print" a stringstream, but you can obtain the std::string representation of its buffer, using the str() member function.

You probably meant, then:

std::cout << buffer.str();

There are cleaner ways to do this, but the above will get you started.

As an aside, your loop is wrong. You're checking for EOF too soon.

answered Jan 04 '16 at 15:56

Lightness Races in Orbit

378,754
76
643
1,055

Of course... Thanks for help. That worked. What do you mean by checking for EOF too soon? Will changing too `do, while` loop help? – Patryk Jan 04 '16 at 16:02
@Patryk: Actually it might. – Lightness Races in Orbit Jan 04 '16 at 18:55

How to save hex representation of binary file into a std::string?

1 Answers1