Re: [ECOS] Network programming for eCos under linux

[Mark Salter <msalter at redhat 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?

How about this (assuming you need integer alignment):

  int aligned_buffer[1024/sizeof(int)];
  char *buffer = (char *)&aligned_buffer;

--Mark