C++: Use Boost Serialization to write/read files [closed] - c++

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I need to write/read a file that contains a std::map. The file must be read at the program start up (if it exists). Im using boost's fstream, but im getting this:
"terminate called after throwing an instance of 'boost::archive::archive_exception'
what(): input stream error"
Well, i really dont know what is happening.. these are my lines:
map<int64_t, int64_t> foo;
filesystem::path myFile = GetWorkingDirectory() / "myfile.dat";
[...............] // some code
filesystem::ifstream ifs(myFile);
archive::text_archive ta(ifs);
if (filesystem::exists(myFile)
{
ta >> foo; // foo is empty until now, it's fed by myFile
ifs.close();
}
What im doing wrong? Any idea?
Thanks.
P.S. Note that some lines after, i need to do the reverse action: write into myfile.dat the std::map foo.
EDIT: all works if i use std::ifstream, saving the file in the same dir where im running the Application. But using boost and his path, something goes wrong.

Answer 1

I'm a bit miffed. You're clearly using Boost Serialization (the archive/ headers are part of this library) but somehow you're not saying anything about that. Because it's so easy to demonstrate:
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#include <boost/archive/text_iarchive.hpp>
#include <boost/archive/text_oarchive.hpp>
#include <boost/serialization/map.hpp>
#include <boost/filesystem.hpp>
#include <boost/filesystem/fstream.hpp>
using namespace boost;
int main() {
std::map<int64_t, int64_t> foo;
filesystem::path myFile = filesystem::current_path() / "myfile.dat";
if (filesystem::exists(myFile))
{
filesystem::ifstream ifs(myFile/*.native()*/);
archive::text_iarchive ta(ifs);
ta >> foo; // foo is empty until now, it's fed by myFile
std::cout << "Read " << foo.size() << " entries from " << myFile << "\n";
} else {
for (int i=0; i<100; ++i) foo.emplace(rand(), rand());
filesystem::ofstream ofs(myFile/*.native()*/);
archive::text_oarchive ta(ofs);
ta << foo; // foo is empty until now, it's fed by myFile
std::cout << "Wrote " << foo.size() << " random entries to " << myFile << "\n";
}
}
Prints
Wrote 100 random entries to "/tmp/myfile.dat"
And on second run:
Read 100 entries from "/tmp/myfile.dat"