Is there any way to force fwrite() to write in big-endian format no matter what? I am trying to write a MIDI file and they are always big-endian. Converting every value I write to big endian beforehand would be extremely tedious. Ideas?
death_oclock 103
Ancient Dragon 5,243
write a wrapper function such as mywrite() and call it instead of fwrite().
nucleon 114
How tedious it is depends on how many different types you need to reverse. If just ints:
typedef unsigned char uchar;
union IntBytes {
int i;
uchar b[sizeof(int)];
};
WriteInt( int n, FILE* fout ) {
union IntBytes uBytes;
int i;
uBytes.i = n;
for (i = sizeof(int) - 1; i >= 0; --i)
fputc( uBytes.b[i], fout );
}death_oclock 103
Would that solution be more or less efficient than calling a function like this on the data before writing:
void swapEndianL(unsigned int *x)
{
*x = (*x>>24) |
((*x << 8) & 0x00FF0000) |
((*x >> 8) & 0x0000FF00) |
(*x << 24);
}nucleon 114
You should profile them. Post your results.
death_oclock 103
Well this isn't a terribly performance-intensive part of my program, and I have to submit the whole bloody thing by friday, so maybe i'll get to it another time, and post the results if anyone is still intersted.
nucleon 114
Don't bother. Mine was "conceptually simple." Your bit-shifting solution is best. It's even a perfect candidate for coding in assembly if performance was an issue.
mcriscolo 47
If you don't mind including <arpa/inet.h>, you can use the htonl() function:
int newval = htonl(origval);The "h" on the front is for "host" and the "n" is for network, "l" on the end for "long" (there is also a version for 16-bit integers). Hence, "Host to network Long". Network format is big endian.
On platforms that are already big endian (like Solaris), it's defined as a NULL macro.
mcldev
Is there any way to force fwrite() to write in big-endian format no matter what? I am trying to write a MIDI file and they are always big-endian. Converting every value I write to big endian beforehand would be extremely tedious. Ideas?
It would be a better idea to keep you code more portable to hanlde big endian/little endian environments. In either case, create a small library or API of functions that you can call before you execute IO. For example, you might have some custom functions that wrap the socket htons/l or ntohs/l functions and opearate on the stream or array or pointer/length you pass. Use that approach and YOU guarantee the format of the data you write to the disk, network, or other file system. You can also add encryption in this manner as well. Good luck
