Boost deserialisation issue : Input Stream Error at runtime (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// How many records have been archived?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// How many records have been archived?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

@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

Answer 2

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.