Length prefixed gzipped streams

gistfile1.hs

import Data.Binary.Get
import qualified Data.ByteString as B
import qualified Data.Enumerator as E
import qualified Data.Enumerator.Binary as EB
import qualified Codec.Zlib.Enum as Z

unzipStream :: E.Iteratee B.ByteString IO b
            -> E.Iteratee B.ByteString IO b
unzipStream sink = do
  -- read four bytes off the wire into a bytestring
  header <- EB.take 4
  -- convert the 4 byte bytestring to a 32 bit little endian integer
  -- then convert it again to an Integer (required for isolate)
  let streamLength = fromIntegral $ runGet getWord32le header
  -- create an Enumerator that is exactly 'streamLength' bytes long
  -- feed it into zlib's decompressor
  -- and stream the decompressed results into 'sink', an Iteratee
  val <- E.joinI (EB.isolate streamLength E.$$ E.joinI (Z.decompress Z.defaultWindowBits E.$$ sink))
  isDone <- E.isEOF
  if isDone
    -- if we're at the end of the input stream, return the last value.
    -- you could also build these up during the recursion or simply ignore
    -- the return value (if any) by returning ()
    then return val
    -- otherwise recurse, reading the next gzipped entry out of the stream
    else unzipStream sink

main :: IO () -- process ./source.file.bin
main = E.run_ $ EB.enumFile "source.file.bin"
           -- and print the decompressed stream to stdout
           E.$$ unzipStream (E.printChunks False)