Hi Dominic, First, thanks to everyone for their help. RIght now, I'm leaning toward Dominic's solution of a collection of helper functions, but I have the feeling that we should be generating them automatically. After all, given a buffer that consists of packed, fixed width fields, if we specify a name and width of the field, making the helper functions should be straightforward. (I understand the network byte order issues. Since I won't always have to examine each field, I wasn't going to convert all fields to host byte order, rather only convert the ones I needed to examine.) It's a little strange that we seem to have to use template haskell or some other preprocessor to do this. Rather like using a sledgehammer to crack a walnut. I'll try to come up with something of general use. I'm very interested to see Tom's (de)serialization framework. As long as this problem is going to require TH, we may as well solve more than one problem. And now I let you return to your discussion of the tab character ;-) Best Wishes, Greg On Jan 26, 2004, at 11:13 AM, Dominic Steinitz wrote:
Gregory,
I don't know if this helps but I ended creating functions like the ones below (I didn't need to use the C structures because the IP definition is language independent). I'm sure there are better ways and I didn't test the throughput but I was able to develop a Haskell version of ping and traceroute (both multi-threaded). It would be nice if there were a library so that we didn't end up re-inventing the wheel.
Dominic.
ipHeaderLength :: String -> Int ipHeaderLength s = (fromIntegral (ord (s !! 0)) .&. 0x0f) * 4
ipTTL :: String -> Int ipTTL s = fromIntegral (ord (s !! 8))
ipProtocol :: String -> IPProto ipProtocol s = toEnum (ord (s !! 9))
ipDestAddr :: String -> HostAddress ipDestAddr s = fromIntegral (ord (s !! 16)) `shiftL` 24 + fromIntegral (ord (s !! 17)) `shiftL` 16 + fromIntegral (ord (s !! 18)) `shiftL` 8 + fromIntegral (ord (s !! 19))