[Haskell-beginners] Reading pcap file

[mukesh tiwari]

Hello everyone
I am writing  application which reads pcap file like wireshark in pure
haskell but there is some thing missing. I read this file
http://www.viste.com/Linux/Server/WireShark/libpcapformat.pdf<http://www.google.com/url?sa=D&q=http://www.viste.com/Linux/Server/WireShark/libpcapformat.pdf&usg=AFQjCNFGc3iahpvawk5KhrVxQzqC2grFJQ>
and
it say that first 24 bytes are global headers , after that every packet
 contains pcap local header and data. What i am trying to do is ,
first trying to get the bytes of data in  each packet by reading the third
 field incl_len in local header but my code is not behaving as it suppose .
I am not getting the list of parsed packets . My test libcap file is
http://wiki.wireshark.org/SampleCaptures?action=AttachFile&do=view&ta...<http://www.google.com/url?sa=D&q=http://wiki.wireshark.org/SampleCaptures%3Faction%3DAttachFile%26do%3Dview%26target%3Dudp_lite_normal_coverage_8-20.pcap&usg=AFQjCNHAd7QbbHa6l55Fwc4MrbbCraMLAQ>


--http://www.viste.com/Linux/Server/WireShark/libpcapformat.pdf<http://www.google.com/url?sa=D&q=http://www.viste.com/Linux/Server/WireShark/libpcapformat.pdf&usg=AFQjCNFGc3iahpvawk5KhrVxQzqC2grFJQ>

--http://hackage.haskell.org/packages/archive/bytestring/0.9.0.4/doc/<http://www.google.com/url?sa=D&q=http://hackage.haskell.org/packages/archive/bytestring/0.9.0.4/doc/&usg=AFQjCNFQJPNdbFIyyTOW8Bb7N9FLj9lsWw>

html/Data-ByteString-Lazy.html
import Data.List
import qualified Data.ByteString.Lazy as BS
import qualified Data.ByteString.Lazy.Char8 as B
import Control.Monad
import Text.Printf
import Data.Word
import Data.Char
import System.Time
import Numeric
import System.Environment

hexTodec :: BS.ByteString ->  Integer
hexTodec lst = read $   "0x" ++  (  concatMap ( \x -> showHex x "" )
$ BS.unpack lst  )

parseFile :: BS.ByteString -> Bool -> IO [ BS.ByteString ]
parseFile xs revflag
  | BS.null xs = return []
  | otherwise =   do
        let ind =if revflag then   hexTodec . BS.reverse . BS.take 4 .
BS.drop 8 $ xs
                  else hexTodec  . BS.take 4 . BS.drop 8 $ xs
        print ind
        let ( x , ys ) = BS.splitAt  ( fromIntegral ind  )  xs
        --BS.putStrLn $ x
        tmp <- parseFile ys revflag
        return $ x : tmp

main = do
        [ file ]  <- getArgs
        contents  <- BS.readFile file
        let ( a , rest ) =  BS.splitAt 24  contents  --strip global header

        let revflag = case BS.unpack $ BS.take 4  a of
                        [ 0xd4 , 0xc3 , 0xb2 , 0xa1 ] -> True
                        _ -> False
        p <-   parseFile  rest  revflag
        print $ p !! 0
        BS.putStr $  p !! 0

Regards
Mukesh Tiwari
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