Boost deserialisation issue : Input Stream Error at runtime (c++) - c++

Question

I've serialised a map fine
std::map<std::string, std::string> userandPass;
saveData< std::map<std::string, std::string> >("userandPassBackup.txt", userandPass); // have removed &. why is this needed. i want to pass by reference
using the function
template <typename SaveClass>
void saveData(const std::string filename, SaveClass& c)
{
// File to be written to
boost::filesystem::remove(boost::filesystem::current_path() /
filename);
boost::filesystem::path myFile = boost::filesystem::current_path() /
filename;
// Declare an output file stream ofs that writes serialises to our
//backup file.
boost::filesystem::ofstream ofs(myFile.native());
// Declare archive ta that will use our output file stream
boost::archive::text_oarchive ta(ofs);
// Write to file
ta << c;
// How many records have been archived?
std::cout << c.size() << " records from have been successfully backed
up to " << myFile << "\n";
}
Deserialising (loading) however, fails, using:
loadData< std::map<std::string, std::string> >("userandPassBackup.txt", userandPass);
where the function is:
template <typename LoadClass>
void loadData(const std::string filename, LoadClass& c)
{
// File to be written to
boost::filesystem::remove(boost::filesystem::current_path() /
filename);
boost::filesystem::path myFile = boost::filesystem::current_path() /
filename;
// Declare an output file stream ofs that writes serialises to our
//backup file.
boost::filesystem::ifstream ifs(myFile.native());
// Declare archive ta that will use our output file stream
boost::archive::text_iarchive ta(ifs);
// Write to file
ta >> c;
// How many records have been archived?
std::cout << c.size() << " records from have been successfully backed
up to " << myFile << "\n";
}
My project compiles, but when I run it, I get the following error concerning the input stream:
libc++abi.dylib: terminating with uncaught exception of type boost::archive::archive_exception: input stream error
Abort trap: 6
I don't see why this is happening. Would anyone be so kind as to point me in the right direction?
Thanks

Answer 1

It seems like you copypasted loadData body from saveData. You delete file that you are trying to load as a first step by calling boost::filesystem::remove.

Answer 2

#VTT got the biggest bug.
Here's my free code review:
you don't need boost::filesystem to std::remove(filename)
instead of currentdir / filename you should do boost::filesystem::make_absolute
that is already default behaviour
you should not use native() since you can pass the path
the argument to saveData can be const&
Do not explicitly pass template arguments: function calls do template argument deduction.
Never mind that your comments are very redundant.
Live On Coliru
#include <boost/serialization/serialization.hpp>
#include <boost/serialization/map.hpp>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <cstdio>
#include <iostream>
#include <fstream>
template <typename SaveClass>
void saveData(const std::string filename, SaveClass const& c)
{
std::remove(filename.c_str());
std::ofstream ofs(filename);
boost::archive::text_oarchive ta(ofs);
ta << c;
}
template <typename LoadClass>
void loadData(const std::string filename, LoadClass& c)
{
std::ifstream ifs(filename);
boost::archive::text_iarchive ta(ifs);
ta >> c;
}
int main() {
std::string filename = "userandPassBackup.txt";
{
std::map<std::string, std::string> userandPass {
{ "John", "pa$$w0rd" },
{ "Jane", "welcome01" } };
saveData(filename, userandPass);
std::cout << userandPass.size() << " records from have been successfully backed up to " << filename << "\n";
}
{
std::map<std::string, std::string> userandPass;
loadData(filename, userandPass);
std::cout << userandPass.size() << " records from have been successfully restored from " << filename << "\n";
}
}
Prints
2 records from have been successfully backed up to userandPassBackup.txt
2 records from have been successfully restored from userandPassBackup.txt