From: wv12@my-deja.com
Subject: Re: First time Ada has let me down
Date: 2000/10/25
Date: 2000-10-25T00:00:00+00:00 [thread overview]
Message-ID: <8t60eo$m0m$1@nnrp1.deja.com> (raw)
In-Reply-To: 8FD7DEBEEsynoptikdamudderfuck@news
In article <8FD7DEBEEsynoptikdamudderfuck@news>,
avlogue@home.com (Shifty) wrote:
> OK, here's the story:
>
> I had a problem at work where I needed to calculate the offset of a
> "magic number" within a buffer containing an IP datagram.
>
> The magic number is 3 protocol headers deep within the datagram, and
> all three headers are variable length. I needed to find the HLEN
> fields of the IP and TCP headers in memory. Turns out both of these
> are stored in 4 bits. The data in the other 4 bits of the octet
> belong to another field in the header.
>
the IP header length occupies the 4 LSB. Assuming p pointing to the
byte offset,
the length is just len = (*p)&0xf;
the TCP header length occupies the 4 MSB. the length in this case
is then ((*p)&0xf0)>>4;
Things just have to be easy in C, don't they. No wonder 99.99% of the
IP stacks in the world are in C and not Ada.
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next prev parent reply other threads:[~2000-10-25 0:00 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-10-25 3:50 First time Ada has let me down Shifty
2000-10-25 0:00 ` First time Ada has let me down (recipe) Guillaume
2000-10-26 2:45 ` Mats Weber
2000-10-25 0:00 ` wv12 [this message]
2000-10-25 0:00 ` First time Ada has let me down Gisle Sælensminde
2000-10-25 0:00 ` Joel Seidman
2000-10-25 0:00 ` Gautier
2000-10-26 6:42 ` tmoran
2000-10-25 0:00 ` Larry Kilgallen
2000-10-25 0:00 ` Ted Dennison
2000-10-25 0:00 ` Larry Kilgallen
2000-10-25 0:00 ` Ted Dennison
2000-10-25 0:00 ` Ken Garlington
2000-10-25 0:00 ` Shifty
2000-10-26 4:00 ` Jeff Carter
2000-10-26 14:43 ` Ted Dennison
2000-10-26 17:55 ` tmoran
2000-10-26 17:12 ` Shifty
2000-10-27 1:00 ` Jeff Carter
2000-10-26 22:27 ` Guillaume
2000-10-26 21:49 ` Keith Thompson
2000-10-26 14:36 ` Ted Dennison
2000-10-26 17:55 ` tmoran
2000-10-26 23:08 ` Ted Dennison
2000-10-25 4:44 ` Julian Morrison
2000-10-25 4:50 ` Ted Dennison
2000-10-24 0:00 ` Keith Thompson
2000-10-26 0:00 ` Andreas Schulz
2000-10-26 18:05 ` Alejandro Villanueva
2000-10-26 21:46 ` Tucker Taft
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