Reading and writing a vector to a binary file [duplicate]

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• Why is iostream::eof inside a loop condition (i.e. `while (!stream.eof())`) considered wrong? 4 answers

I wrote a code to save stl::vector into a binary file. In the following example, I stored 4 floats and obviously the size of the file is 16 bytes. But when I read them it reads 5 floats! Why??!?

#include <vector>
#include <fstream>


int main( int argc, const char** argv )
{
  std::vector<float> fv1;
  std::vector<float> fv2;

  fv1.push_back(1.54);
  fv1.push_back(2.566);
  fv1.push_back(2.234522);
  fv1.push_back(2.2245);



  std::ofstream out2("test.bin",std::ios_base::binary);
  if(out2.good())
  {
    out2.write((char *)&fv1[0],sizeof(float)*fv1.size());
    out2.close();
  }


  std::ifstream in2("test.bin",std::ios_base::binary);
  while(!in2.eof())
  {
    float ftmp;
    in2.read((char *)&ftmp,sizeof(float));
    fv2.push_back(ftmp);
    std::cout << "Reading floating point number: " << std::fixed << ftmp << std::endl;
  }

  std::cout << "vector size: " << fv2.size() << std::endl;
  for(auto i:fv2)
    std::cout<<"fv2:"<<i<<std::endl;


  return 0;
}