C++ equivalent of 'pack' in Perl

Question

How do I write C++ code that does what the pack -N option does in Perl?

I want to convert an integer variable to some binary form such that the unpack -

Answer 1

It takes 4 bytes and forms a 32-bit int as follows:

uint32_t n;
n = buf[0] << 24
  | buf[1] << 16
  | buf[2] <<  8
  | buf[3] <<  0;

For example,

uint32_t n;
unsigned char buf[4];
size_t bytes_read = fread(buf, 1, 4, stream);
if (bytes_read < 4) {
   if (ferror(stream)) {
      // Error
      // ...
   }
   else if (feof(stream)) {
      // Premature EOF
      // ...
   }
}
else {
   n = buf[0] << 24
     | buf[1] << 16
     | buf[2] <<  8
     | buf[3] <<  0;
}