The uu-parsing library support every ata type that is an instance of
Data.Listlike
(http://hackage.haskell.org/packages/archive/ListLike/3.0.1/doc/html/Data-ListLike.html#t:ListLike)
and thus input from Data.Bytestring.Lazy.
A very small starting program can be found below. Note that here we ask for the
error correction during parsin at the end of the processing; that is probably
something you do not want to do, unless you only keep a very small part of the
input in the result. The parsers are online, do not hang on to the input and
thus you essentially only access and keep the part of the result you are
interested in.
We find it a great help to have the error correction at hand since it makes it
a lot easier to debug your parser. Here we just recognise any list of Word8's.
Doaitse
{-# LANGUAGE MultiParamTypeClasses #-}
module ReadLargeBinaryFile where
import Text.ParserCombinators.UU
import Text.ParserCombinators.UU.BasicInstances
import Data.Word
import Data.ByteString.Lazy (ByteString,readFile)
import Prelude hiding (readFile)
type BS_Parser a = P (Str Word8 ByteString Integer) a
instance IsLocationUpdatedBy Integer Word8 where
advance pos _ = pos + 1
p:: BS_Parser [Word8]
p = pList (pSatisfy (const True) (Insertion "" 0 0) )
main filename = do inp <- readFile filename
let r@(a, errors) = parse ( (,) <$> p <*> pEnd)
(createStr 0 inp)
putStrLn ("-- Result: " ++ show a)
if null errors then return ()
else do putStr ("-- Correcting steps:
\n")
show_errors errors
putStrLn "-- "
where show_errors :: (Show a) => [a] -> IO ()
show_errors = sequence_ . (map (putStrLn . show))
interface and that exists for Data.
On 10 mrt 2011, at 16:36, Skeptic . wrote:
>
>
> Hi,
> I finally have an opportunity to learn Haskell (I'm a day-to-day Java
> programmer, but I'm also at ease with Scheme), parsing a huge (i.e. up to 50
> go) binary file. The encoding is very stable, but it's not a flat struct
> array (i.e. it uses flags).
> Different outputs (i.e. text files) will be needed, some unknown at this
> time.
> Sounds to me a perfect "real-world" task to see what Haskell can offer.
>
> Any suggestions at how to structure the code or on which packages to look at
> is welcome.
>
> Thanks.
> _______________________________________________
> Haskell mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/haskell
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