Write in Binary format in a binary file

[hogren]

Hello,

I begin by give my code :

#include <ostream>
#include <istream>
#include <fstream>

namespace std
{
extern istream cin;
extern ostream cout;
// this is explained below
static ios_base::Init __foo; // not its real name
}
using namespace std;
main()
{
ofstream f ("toto.xyz", ios::out | ios::binary);
int x[2] = {1,1};
int i;
if(!f.is_open())
cout << "Impossible d'ouvrir le fichier en écriture !\n";
else
{
for (i = 0; i < 2; i++)
f.write ((char *)&x[i], sizeof(int));
}
cout << "bonjour !!";
f.close();
return 0;
}

The result is a file whith binary value

00000001 00000001

I want to write directly in binary. I want that the file will have for value

00000011

Thank you for reponses and sorry for my english (I am french).

[Athar]

You can use bitshifting to do that:

int x[2] = {1,1};
int v=x[0]<<1 | x[1];
f.write (reinterpret_cast<const char*>(&v),sizeof(v));

By the way,

namespace std
{
extern istream cin;
extern ostream cout;
// this is explained below
static ios_base::Init __foo; // not its real name
}

is unnecessary. Instead, include <iostream> (instead of <ostream> and <istream>).

The definition of main is also incorrect. It needs to be int main().

[helios]

namespace std
{
extern istream cin;
extern ostream cout;
// this is explained below
static ios_base::Init __foo; // not its real name
}

Don't do that. Include <iostream>.

11b is just 3.

char a=3;
file.write(&a,1);

We can probably give better advice if you tell use what you want to do in more detail.

[hogren]

Thank you for reponses. I am not a C++ beginner but I was not practiced for a quiet long time.

For your solution, Athar, what should I change for that give me 00000111 ?

I want simply write directly in binary in a file.

Thank you for reponses.

[Athar]

Three bits:

int x[3] = {1,1,1};
int v=x[0]<<2 | x[1]<<1 | x[2];
f.write (reinterpret_cast<const char*>(&v),sizeof(v));

Just look up the bitshift operators (<< and >>) and the other bit-wise operators |, & and ~ (or, and, not) to understand what they do.

There is no bit stream class in C++. You can easily create your own, though.

[hogren]

Thank you very much !
I will study the bitshifting.
Bye Bye