From: Luke Diamand <ldiamand@virata.com>
To: jens.ohlund@secrc.abb.se
Cc: crossgcc@sourceware.cygnus.com
Subject: Re: ARM and padding
Date: Tue, 18 Jul 2000 02:38:00 -0000 [thread overview]
Message-ID: <39742586.345DFC32@virata.com> (raw)
In-Reply-To: <OF8C34C8B1.FD7B6B3C-ONC1256920.002B9939@secrc.abb.se>
Looking at your structure, and noting that the data is not word aligned
in the first place, I suspect you may struggle to get this approach to
work - won't the ARM end up totally garbling the word access to the int
field three quarters of the time?
You might prefer to use direct byte reads and manipulations - e.g.
inline int getRemainingBytes( unsigned char *bytes ) {
unsigned char *ptr = bytes+251;
return ptr[0]+(ptr[1]<<8)+(ptr[2]<<16)+(ptr[3]<<24); // or
something like that
}
This also has the virtue that you can cope better if you get endian
blues.
Just my 2c.
jens.ohlund@secrc.abb.se wrote:
>
> Hi !
>
> My problem is the following:
> I have an ARM Evaluation Board-1. Rev B. I receive data from a serial line.
> this data is placed in a linear buffer, and then i typecast to a struct of some kind.
>
> This data which i receive I cannot control, and have therefore to work with it as is.
>
> The structs contains other structs and so on and in the end it's only 16 or 8 bits values a extract.
> BUT these values are not aligned, and when I typecast I get the wrong values, since the buffer is "packed".
>
> How do I tell the compiler that the structs are to be packed ?
>
> I'm developing on NT4, using cygwin and gcc-2.95.2 (arm-elf-gcc).
>
> yours
> Jens Ohlund
>
> ------
> Want more information? See the CrossGCC FAQ, http://www.objsw.com/CrossGCC/
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next prev parent reply other threads:[~2000-07-18 2:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-07-18 1:01 jens.ohlund
2000-07-18 1:36 ` Philip Blundell
2000-07-18 2:38 ` Luke Diamand [this message]
2000-07-18 2:14 jens.ohlund
2000-07-18 2:28 ` Ola Liljedahl
2000-07-19 2:12 Ilya Vershkov
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