FreeTDS Development Group

[ZIGLIO Frediano <Frediano.Ziglio AT vodafoneomnitel.it>]

> 
> > This line 
> >  memcpy (&(any.u), src, sizeof(TDS_UNIQUE));
> > 
> > Do not work for bigendian machine
> > 
> > freddy77
> 
> Hi Freddy,
> 
> Nice to have someone else in the European Time Zone!
> That's my line of code...can you explain further what's wrong ?
> 
> Thanks,
> 
> Bill
> 
src is a TDS_CHAR* (a raw pointer) and you copy it in a structure. If
structure is byte to byte the same you copy correctly data but on different
architectures this fail.
Consider this structure:

typedef struct Test
{
        TDS_INT num;
} Test;

and following octets (assuming TDS_INT 32bit):
*src = 01 02 03 04 (not C code...)
doing 
Test tst;
memcpy(&tst, src, sizeof(tst));
Will produce tst.num == 0x4030201 on little endian machine (such as intel)
and tst.num == 0x1020304 on big endian machine (such as sparc).
Also in some architecture you can have TDS_INT 64bit (alpha) having garbage
and other problems...

Best solution is to build structure, such as

tst.num = src[0] | (src[1] << 8) | (src[2] << 16) | (src[3] << 24);

(a macro/inline function and some optimization for every platform is
preferred)
This should work on every architecture (even quantic, where machine do not
handle bit very simply)

freddy77

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