From: Jonathan Larmour <jlarmour@redhat.com>
To: "Trenton D. Adams" <tadams@theone.dnsalias.com>
Cc: 'Grant Edwards' <grante@visi.com>,
'Andrew Lunn' <andrew.lunn@ascom.ch>,
'eCos discussion' <ecos-discuss@sources.redhat.com>
Subject: Re: [ECOS] Network programming for eCos under linux
Date: Wed, 08 Aug 2001 09:06:00 -0000 [thread overview]
Message-ID: <3B716392.17D4E08D@redhat.com> (raw)
In-Reply-To: <000001c12022$dfa2f460$090110ac@TRENT>
"Trenton D. Adams" wrote:
>
> >
> > > 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!
Oops yes.
> 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?
If 8 byte alignment was the requirement then you certainly wouldn't want
to. I suppose in that case you would make the buffer be 1031 bytes to
ensure it could fit 1024 bytes post alignment.
Jifl
--
Red Hat, Rustat House, Clifton Road, Cambridge, UK. Tel: +44 (1223) 271062
Maybe this world is another planet's Hell -Aldous Huxley || Opinions==mine
next prev parent reply other threads:[~2001-08-08 9:06 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-08-07 15:41 Trenton D. Adams
2001-08-08 0:35 ` Andrew Lunn
2001-08-08 6:27 ` Jonathan Larmour
2001-08-08 6:51 ` Andrew Lunn
2001-08-08 7:13 ` Grant Edwards
2001-08-08 7:52 ` Jonathan Larmour
2001-08-08 8:02 ` Andrew Lunn
2001-08-08 8:06 ` Trenton D. Adams
2001-08-08 8:14 ` Jonathan Larmour
2001-08-08 8:47 ` Trenton D. Adams
2001-08-08 8:58 ` Trenton D. Adams
2001-08-08 9:04 ` Mark Salter
2001-08-08 9:06 ` Jonathan Larmour [this message]
2001-08-08 9:19 ` [ECOS] " Grant Edwards
2001-08-08 9:07 ` Grant Edwards
2001-08-08 8:32 ` [ECOS] " Grant Edwards
2001-08-08 8:43 ` Trenton D. Adams
2001-08-08 8:57 ` [ECOS] " Grant Edwards
2001-08-08 7:57 ` [ECOS] " Trenton D. Adams
2001-08-08 8:09 ` Grant Edwards
2001-08-08 8:14 ` Trenton D. Adams
2001-08-08 8:42 ` Grant Edwards
2001-08-08 8:21 ` Andrew Lunn
2001-08-08 8:27 ` Trenton D. Adams
2001-08-08 9:00 ` [ECOS] " Grant Edwards
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