Thread: Binary File - Byte order / endian

ok there is a function in:
#include <winsock2.h>

called:
ntohs(DataPoint); <datapoint is a short... ntohs works for shorts

but when i try to use it I get this

Code:

Linking...
TestTile.obj : error LNK2001: unresolved external symbol __imp__ntohs@4
Debug/TestTile.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

TestTile.exe - 2 error(s), 0 warning(s)

here is the MSDN for it:
http://msdn.microsoft.com/library/de...e_ordering.asp

which means i am missing a library... does anyone know anything about this?

OR

does anyone know how that function i posted earlier does?

if anyone here has VS 2005.. can you look inside winsock2.h to see if there are any library includes.

Originally Posted by chico1st

if anyone here has VS 2005.. can you look inside winsock2.h to see if there are any library includes.

You need to link with wsock32.lib

wow you rock man.. thanks
that worked perfectly

is there any way to check the endian-ness of a variable?

Originally Posted by chico1st

is there any way to check the endian-ness of a variable?

Yes. Something like this will work:

Code:

#define BIG_ENDIAN 1
#define LITTLE_ENDIAN 2
int endian_ness()
{
   int x = 0x01000002;
   char *p = (char *)&x;

   if (x == 0x01) 
       return BIG_ENDIAN;
   else if (x == 0x02)
       return LITTLE_ENDIAN;
   else { 
       printf("Strange integer format or bad compiler\n");
       exit(1);
   }
}

--
Mats

It's worth noting that ALL variables on a particular system has the same endianness. [By the way, the word endian is related to the book "Gulliver's travels", where the two islands were at war because they wouldn't agree on which end of the egg one should start eating, the "thick" (big) end, or the "thin" (little) end - forming the warring factions of Big Endians and Little Endians - and of course, computer architects would discuss which is better at length!]

--
Mats

Originally Posted by KIBO

little/big endian is processor related, not OS

Don't Macs use Motorola processors and PC's use Intel processors? I never mentioned anything about OS's...

Originally Posted by Sebastiani

>> is there any way to check the endian-ness of a variable?

endian-ness is simply the storage convention used by a CPU (within it's registers) to manipulate numbers. it has no effect on the numbers themselves.

No, it's the EXTERNAL storage format in the memory that is defined by the endian-ness. The internal storage within the processor is completely invisible to an external observer - for all we know, the bits can be stored in any order in a register internally in the machine, as long as it "appears" that bit 31 is the most significant bit (and this doesn't matter if it's a BE or LE machine) and bit 0 is the least significant, and all bits in between come in the appropriate order. [That's for a 32-bit word - but it applies analogously to any size data that the processor will process as one unit].

When the data is stored in memory, however, the data will be stored in a particular order: Big endian stores the most significant byte first, Little Endian stores the least significant byte first.

--
Mats

Originally Posted by MacNilly

Don't Macs use Motorola processors and PC's use Intel processors? I never mentioned anything about OS's...

IIRC, Macs used to use PowerPCs, and they relatively recently switched to Intels.

Originally Posted by MacNilly

If I made a binary file on a PC writing the words 10, 20, 30, and 40, and you tried to read that on a Mac, you're telling me you would get 10, 20, 30 and 40?

Given that my Mac has an Intel chip, I would have to say... yes.

Properly written software takes endianness into account. Just because a file is "binary" doesn't mean it can't be manipulated on processors of differing endianness.