(C++) Write and read a std::vector to/from a std::stream: example 2

This write and read a std::vector to/from a std::stream example demonstrates a safe way. The program its setup is fine: a std::vector is created, written to file, a new std::vector is written from that same file and the program tests if the two std::vectors are identical.

The assumptions for this approach to work are:

• Text may not contain a bell ('\b') character

Note that the program will issue a failed assert when the assumption is violated. Wonder, how often have you given a bell character as input?

#include <iostream>
#include <iterator>
#include <cassert>
#include <algorithm>
#include <fstream>
#include <string>
#include <vector>

std::ostream& operator<<(std::ostream& os, const std::vector<std::string>& w)
{
  //Copy the original std::vector
  std::vector<std::string> v = w;
  //Preformat data
  std::for_each(v.begin(),v.end(),
    [&os](std::string& s)
    {
      //The only assertion done on the input
      //Note that users nearly every use bell characters in their text inputs
      assert(std::count(s.begin(),s.end(),'\b') == 0 && "Text must not contain a bell character");
      std::replace(s.begin(),s.end(),' ','\b');
      if (s == "</>") s = "<\b/>";
    }
  );
  //Check data
  #ifndef NDEBUG
  std::for_each(v.begin(),v.end(),
    [&os](const std::string& s)
    {
      assert(s != "</>" && "Text shoule not be '</>' anymore");
      assert(std::count(s.begin(),s.end(),' ') == 0 && "Text should not contain spaces anymore");
    }
  );
  #endif
  //Write start tag
  os << "<>\n";
  //Write data
  std::for_each(v.begin(),v.end(),
    [&os](const std::string& s)
    {
      os << s << '\n';
    }
  );
  //Write end tag
  os << "</>";
  return os;
}

std::istream& operator>>(std::istream& is, std::vector<std::string>& v)
{
  //Read start tag
  {
    std::string s; is >> s; assert(s == std::string("<>"));
  }
  //Read data until end tag
  while (1)
  {
    std::string s;
    is >> s;
    if (s == std::string("</>")) return is;
    if (s == "<\b/>") s = "</>";
    std::replace(s.begin(),s.end(),'\b',' ');
    v.push_back(s);
  }
}

int main()
{
  //Go ahead, create an entry that breaks the code!
  const std::vector<std::string> v(
    {
      "aahs",
      "aals",
      "abac",
      "abas",
      "</>",
      " </>",
      " </> ",
      "_</>",
      "</>_",
      "</></>",
      "</> </>",
      "</>_</>",
      "abba",
      "abbe",
      "abbs",
      "abed",
      "abet",
      "abid"
    }
  );
  const std::string filename = "tmp.txt";
  //Write to file
  {
    std::ofstream f(filename.c_str());
    f << v;
  }
  //Read from file
  {
    std::vector<std::string> w;
    std::ifstream f(filename.c_str());
    f >> w;
    if (v != w)
    {
      std::copy(w.begin(),w.end(),std::ostream_iterator<std::string>(std::cout,"\n"));
    }
    assert(v == w && "Because the algorithm is excellent, this will never happen B-)");
  }
}