    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Data.Digest.MD5
    -- Copyright   :  (c) Dominic Steinitz 2004
    -- License     :  BSD-style (see the file ReadMe.tex)
    --
    -- Maintainer  :  dominic.steinitz@blueyonder.co.uk
    -- Stability   :  experimental
    -- Portability :  portable
    --
    -- Takes the MD5 module supplied by Ian Lynagh and wraps it so it
    -- takes [Octet] and returns [Octet] where the length of the result
    -- is always 16.
    -- See <http://web.comlab.ox.ac.uk/oucl/work/ian.lynagh/>
    -- and <http://www.ietf.org/rfc/rfc1321.txt>.
    --
    -----------------------------------------------------------------------------

    module Data.Digest.MD5 (
       -- * Function Types
       hash) where

    import Data.Digest.MD5Aux
    import Codec.Utils
    import Data.Char(chr)
    import Data.List(unfoldr)
    import Numeric(readHex)

    -- | Take [Octet] and return [Octet] according to the standard.
    --   The length of the result is always 16 octets or 128 bits as required
    --   by the standard.

    hash :: [Octet] -> [Octet]
    hash xs =
       unfoldr f $ md5s $ Str $ map (chr . fromIntegral) xs
          where f :: String -> Maybe (Octet,String)
                f [] =
                   Nothing
                f (x:y:zs) =
                   Just (fromIntegral a,zs)
    	       where [(a,_)] = readHex (x:y:[])