Question

I have my struct:

struct a
{
  int    x;
  float  f;
  double d;
  char   c;
  char   s[50];
};

and I wish append each time into my timer schedule into a binary file.

// declaration
std::ofstream outFile;

// constructor:
outFile.open( "save.dat", ios::app );

// tick:
outFile << a << endl;

but inside the save.dat appears only this:

0C3A0000..0C3A0000..0C3A0000..0C3A0000..0C3A0000..0C3A0000..0C3A0000..0C3A0000..0C3A0000..

thanks in advance

Answer 1

What you’re currently doing is writing the address of the struct definition.
What you want to do is use ostream::write

outfile.write(reinterpret_cast<char*>(&myStruct), sizeof(a));

This will work as long as your struct is a POD (Plain Old Data) type (which your example is). POD type means that all members are of fixed size.

If you on the other hand have variable sized members then you would need to write out each member one by one.