From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Grant Edwards" <grante@visi.com>
To: "Trenton D. Adams" <tadams@theone.dnsalias.com>
Cc: "'Jonathan Larmour'" <jlarmour@redhat.com>, "'Andrew Lunn'" <andrew.lunn@ascom.ch>, "'eCos discussion'" <ecos-discuss@sources.redhat.com>
Subject: [ECOS] Re: Network programming for eCos under linux
Date: Wed, 08 Aug 2001 09:07:00 -0000
Message-id: <20010808160751.B73547A926@visi.com>
References: <000001c12022$dfa2f460$090110ac@TRENT>
X-SW-Source: 2001-08/msg00247.html

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