Riccardo Manfrin wrote:
> Hi, I'm looking for the best way to handle byte order when switching
> from network (big-endian) to host (little-endian in my case), from an
> implementation point of view..
>
> I'd like to have a structure data type (e.g. bigendian_short_t that
> is capable of aligning bytes in the correct way when passing from
> memory to the value and viceversa).
>
> I know this is done in NesC compiler with specific data structures. Is
> there something for GNU GCC/G++
>
> Any material is appreciated.
>
Most applications directly use ntohl()/htonl() when moving data from/to
network structures. With g++ you can hide that under overloaded
operators, something like the code below. However trying to put a few of
those in a struct and then casting the struct directly over a network
packet will probably not work due to the extra data that C++ objects can
have. So you'd still have to assign them one-by-one, and then you might
as well directly use ntohl()/htonl() in the assignments.
-j
#include <stdio.h>
#include <string.h>
#include <arpa/inet.h>
class network_int {
public:
operator int() const { return ntohl(val); }
int operator= (int newval) { val=htonl(newval); return *this; }
operator void *() { return &val; }
private:
int val;
};
int main(int argc, char **argv) {
int x = 0x12345678;
network_int n;
n = x;
printf("%lx %lx\n", x, *(int*)(void*)n);
x = 0xabcdef12;
memcpy(n, &x, sizeof(x));
printf("%lx %lx\n", (int)n, *(int*)(void*)n);
return 0;
}
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