From: avlogue@home.com (Shifty)
Subject: First time Ada has let me down
Date: Wed, 25 Oct 2000 03:50:28 GMT
Date: 2000-10-25T03:50:28+00:00 [thread overview]
Message-ID: <8FD7DEBEEsynoptikdamudderfuck@news> (raw)
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.
This stumped me for awhile, but then I went home and picked up a C book.
Hmmm, chapter 15 - bit fiddling. I learned a bunch of stuff about masks
and bitwise operators and came up with a working solution. (which seems
much better than using record representation clauses and typecasting a 4
bit value into an 8 bit integer)
Next morning I tried to implement the solution and couldn't find the Ada
equivalent of C's bit-wise & operater. According to my "Ada as a 2nd
language" book, the Ada reserved word "AND" only works for boolean types,
not integer types. I got the impression that it was up to the programmer
to write his own bitwise ANDs/ORs/XORs, etc (it wouldn't be hard).
Luckily I found a vendor-supplied package which provided this
functionality, but I can't believe Ada (83) doesn't have native
language support for these!!! Please tell me that I am hopelessly
confused and dead wrong!
Cheers,
Andrew.
next reply other threads:[~2000-10-25 3:50 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-10-25 3:50 Shifty [this message]
2000-10-25 0:00 ` First time Ada has let me down 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 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 ` wv12
2000-10-25 0:00 ` Joel Seidman
2000-10-25 0:00 ` Gisle Sælensminde
2000-10-25 0:00 ` Gautier
2000-10-26 6:42 ` tmoran
2000-10-25 0:00 ` First time Ada has let me down (recipe) Guillaume
2000-10-26 2:45 ` Mats Weber
2000-10-25 4:44 ` First time Ada has let me down 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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