[ECOS] Re: Network programming for eCos under linux

["Grant Edwards" <grante at visi dot com>]

Trenton D. Adams writes:

>   > 
>   > > So, how would one go about making a buffer word aligned or DWORD
>   > aligned
>   > > just to be safe?
>   > 
>   > something along the lines of:
>   > 
>   > char buffer[1024];
>   > #define ALIGNMENT 8
>   > #define ALIGNUP(_x_) (((char *)(_x_) + ALIGN-1) & ~(ALIGN-1))
>   > int *foo = ALIGNUP(buffer);
>   > 
>   > You could also use __alignof(int) to give the alignment but that's
>   > obviously a GNU C-ism.
>   >  
> 
> First of all, I assume your ALIGN is actually supposed to be ALIGNMENT! 
> 
> I don't understand your macro.  Let's say _x_ happens to be memory
> address 0x201 the macro formula would go like this 
> 
> = (0x201 + 7) & ~(7)
> = 0x208 & 0xfffffff8
> = 0x208 
> 
> So, now foo is pointing to an integer that is not at the beginning of
> the buffer.  This would mean that I couldn't put anything at the
> beginning of the buffer, correct?

Not by dereferenceing a short or int pointer.  You've got to use memcpy(). 

-- 
Grant Edwards
grante@visi.com