Serialise and deserialise vector in binary

Question

I am having problems trying to serialise a vector (std::vector) into a binary format and then correctly deserialise it and be able to read the data. This is my first time us

Answer 1

I would write in network byte order to ensure file can be written&read on any platform. So:

#include 
#include 
#include 
#include 

#include 

int main(void) {

  std::vector v = std::vector();
  v.push_back(111);
  v.push_back(222);
  v.push_back(333);


  {
    std::ofstream ofs;
    ofs.open("vecdmp.bin", std::ios::out | std::ios::binary);

    uint32_t sz = htonl(v.size());
    ofs.write((const char*)&sz, sizeof(uint32_t));
    for (uint32_t i = 0, end_i = v.size(); i < end_i; ++i) {
      int32_t val = htonl(v[i]);
      ofs.write((const char*)&val, sizeof(int32_t));
    }

    ofs.close();
  }

  {
    std::ifstream ifs;
    ifs.open("vecdmp.bin", std::ios::in | std::ios::binary);

    uint32_t sz = 0;
    ifs.read((char*)&sz, sizeof(uint32_t));
    sz = ntohl(sz);

    for (uint32_t i = 0; i < sz; ++i) {
      int32_t val = 0;
      ifs.read((char*)&val, sizeof(int32_t));
      val = ntohl(val);
      std::cout << i << '=' << val << '\n';
    }
  }

  return 0;
}