Replace zlib use by compression.

cabal-install/TODO

@@ -7,5 +7,3 @@
 - Overhaul verbosity
 
 - Figure out command-line interface
-
-- Get rid of zlib dependency

cabal-install/cabal-install.cabal

@@ -15,7 +15,7 @@ Build-depends: base, mtl, network, regex-compat,
                filepath >= 1.0,
                Cabal>=1.3,
                HTTP >= 3000.0 && < 3000.1, 
-               zlib >= 0.3
+               compression >= 0.1
 Extra-Source-Files: copyright README
 
 Executable: cabal-install

cabal-install/src/Network/Hackage/CabalInstall/Tar.hs

 -- | Simplistic TAR archive reading. Only gets the file names and file contents.
 module Network.Hackage.CabalInstall.Tar (TarHeader(..), TarFileType(..),
                                          readTarArchive, extractTarArchive, 
-                                         extractTarGzFile) where
+                                         extractTarGzFile, gunzip) where
 
 import qualified Data.ByteString.Lazy.Char8 as BS
 import Data.ByteString.Lazy.Char8 (ByteString)
@@ -15,7 +15,8 @@ import System.Directory (Permissions(..), setPermissions, createDirectoryIfMissi
 import System.FilePath ((</>), isValid, isAbsolute)
 import System.Posix.Types (FileMode)
 
-import Codec.Compression.GZip (decompress)
+--import Codec.Compression.GZip (decompress)
+import Codec.Compression.GZip.GUnZip (gunzip)
 
 data TarHeader = TarHeader {
                             tarFileName   :: FilePath,
@@ -43,7 +44,7 @@ extractTarGzFile :: Maybe FilePath -- ^ Destination directory
                -> FilePath -- ^ Tarball
                -> IO ()
 extractTarGzFile mdir file = 
-    BS.readFile file >>= extractTarArchive mdir . readTarArchive . decompress
+    BS.readFile file >>= extractTarArchive mdir . readTarArchive . gunzip
 
 --
 -- * Extracting

cabal-install/src/Network/Hackage/CabalInstall/Update.hs

@@ -17,13 +17,13 @@ module Network.Hackage.CabalInstall.Update
 import Network.Hackage.CabalInstall.Types (ConfigFlags (..), PkgInfo(..), Repo(..))
 import Network.Hackage.CabalInstall.Utils (isVerbose)
 import Network.Hackage.CabalInstall.Fetch (downloadIndex, packagesDirectory)
+import Network.Hackage.CabalInstall.Tar (gunzip)
 
 import Distribution.Package (PackageIdentifier(..), pkgName, showPackageId)
 import Distribution.PackageDescription (PackageDescription(..), readPackageDescription, GenericPackageDescription(..))
 import Distribution.Verbosity
 import System.FilePath ((</>), joinPath, addExtension, takeExtension, dropExtension)
 
-import Codec.Compression.GZip(decompress)
 import Control.Monad (liftM, when)
 import qualified Data.ByteString.Lazy.Char8 as BS
 import Data.ByteString.Lazy.Char8 (ByteString)
@@ -41,4 +41,4 @@ updateRepo :: ConfigFlags
 updateRepo cfg repo =
     do printf "Downloading package list from server '%s'\n" (repoURL repo)
        indexPath <- downloadIndex cfg repo
-       BS.readFile indexPath >>= BS.writeFile (dropExtension indexPath) . decompress
+       BS.readFile indexPath >>= BS.writeFile (dropExtension indexPath) . gunzip