I'm trying to figure out a dead-simple task using LibZip in Haskell: how do I open an archive foo.zip, decompress it, recompress it, and save it to a new archive bar.zip? With the Zip library, this is easy:
{-# LANGUAGE OverloadedStrings #-}
import Codec.Archive.Zip (toArchive, fromArchive)
import qualified Data.ByteString.Lazy as B
import System.Environment
saveZipAs :: FilePath -> FilePath -> IO ()
saveZipAs source dest = do
arch <- fmap toArchive $ B.readFile source
putStrLn "Archive info: " >> print arch
B.writeFile dest $ fromArchive arch
LibZip, on the other hand, provides no clear way to do this (that I can see). It only seems to be able to instantiate a zip file with withArchive (which is an issue in and of itself, because a file you want to open might not be on disk), and I don't see a way to do any kind of "save as" operation, nor to extract the compressed bytes as a ByteString or otherwise (as in Zip). LibZip is supposedly faster than Zip, so I want to at least give it a try, but it seems much more obscure (and also impure, carrying around an IO everywhere it goes, where it is really only needed at the beginning and the end, if ever). Can anyone give me some tips?
Side note: it really boggles the mind how people can spend such huge amounts of time writing a library, only to document it so poorly that no one can use it. Library writers, please don't do this!
Your link is somehow to an old version of the library, and the very last version of the library seems to have haddock compilation bugs.
Here are file reading functions in a newer version:
http://hackage.haskell.org/package/LibZip-0.10.2/docs/Codec-Archive-LibZip.html#g:3
The reverse process seems to be addFile/sourceBuffer and related functions.
Here is full source code of zip repacking:
import Codec.Archive.LibZip
import Codec.Archive.LibZip.Types
main = readZip "foo.zip" >>= writeZip "bar.zip"
readZip :: FilePath -> IO [(FilePath, ZipSource)]
readZip zipName = withArchive [] zipName $ do
nn <- fileNames []
ss <- mapM (\n -> sourceFile n 0 (-1)) nn
return $ zip nn ss
writeZip :: FilePath -> [(FilePath, ZipSource)] -> IO ()
writeZip zipName zipContent = withArchive [CreateFlag] zipName $ do
mapM_ (uncurry addFile) zipContent
Few refactorings still can be done: liftM2 zip can be used in readZip, and function composition . in writeZip.
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