How to Save and Read Binary Data?

Question

I need your help again for the save and read data in binary. I have, a vector<<complex> > xy(256) which is read from the hardware in 10 times:

vector<<complex> > xy(256);
ofstream outfile2 (outfilename2.c_str() , ofstream::binary);
....
....
for(unsigned t = 0; t < 10; t++)
{
     ....
     ....
     for(unsigned i = 0; i < 256; i++)
     {
           xy[i] = f[i] * conj(g[i]);
     }
     for(unsigned i = 0; i < 256; i++)
     {
           outfile2 << boost::format("%20.8e") % xy[i]<< endl;  // write in text
     }
}  // the text data will be 2560 lines of complex data, for example:
   // (6.69635350e+06,7.34146150e+06)

Now, I am trying to save into binary file, using this command:

for(unsigned i = 0; i < 256; i++)
     {
        outfile2.write((const char*)& xy[i], 1 * sizeof(complex<short>));
        outfile2.flush();
     }

Although, it still give me a data, but when i compare to the original text data, they were different. I do not understand why?

I would like to read complex 16 with floating point data.

I hope you guys can help.

Thank you very much.

Answer 1

I have written a demo, which works on my computer.

#include <cassert>

#include <complex>
#include <fstream>
#include <iostream>
#include <type_traits>
#include <vector>

int main() {
  assert( std::is_trivially_copy_assignable<std::complex<short> >::value );

  std::vector<std::complex<short> > vtr(256);
  for (int i=0; i<256; ++i)
    vtr[i] = std::complex<short>(i*2,i*2+1);

  {
    std::ofstream output("data.bin", std::ofstream::binary);
    for (int i=0; i<256; ++i)
      output.write((char *)&vtr[i],sizeof(vtr[i]));
  }
  vtr.clear();

  std::cout << vtr.size() << std::endl;

  vtr.resize(256);
  {
    std::ifstream input("data.bin", std::ifstream::binary);
    for (int i=0; i<256; ++i)
      input.read((char *)&vtr[i],sizeof(vtr[i]));
  }

  for (size_t i=0; i<vtr.size(); ++i)
    std::cout << vtr[i] << " ";
  std::cout << std::endl;

  return 0;
}

You could run this demo on your computer. If this demo works, it's likely that you made some mistakes in your code. Please provide a complete, and verifiable example.