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{- GHC File system encoding handling.
- Copyright 2012 Joey Hess <>
- Licensed under the GNU GPL version 3 or higher.
module Utility.FileSystemEncoding where
import qualified GHC.Foreign as GHC
import qualified GHC.IO.Encoding as Encoding
import Foreign.C
import System.IO
import System.IO.Unsafe
import qualified Data.Hash.MD5 as MD5
{- Sets a Handle to use the filesystem encoding. This causes data
- written or read from it to be encoded/decoded the same
- as ghc 7.4 does to filenames etc. This special encoding
- allows "arbitrary undecodable bytes to be round-tripped through it". -}
fileEncoding :: Handle -> IO ()
fileEncoding h = hSetEncoding h =<< Encoding.getFileSystemEncoding
{- Marshal a Haskell FilePath into a NUL terminated C string using temporary
- storage. The FilePath is encoded using the filesystem encoding,
- reversing the decoding that should have been done when the FilePath
- was obtained. -}
withFilePath :: FilePath -> (CString -> IO a) -> IO a
withFilePath fp f = Encoding.getFileSystemEncoding
>>= \enc -> GHC.withCString enc fp f
{- Encodes a FilePath into a Str, applying the filesystem encoding.
- This use of unsafePerformIO is belived to be safe; GHC's interface
- only allows doing this conversion with CStrings, and the CString buffer
- is allocated, used, and deallocated within the call, with no side
- effects.
{-# NOINLINE encodeFilePath #-}
encodeFilePath :: FilePath -> MD5.Str
encodeFilePath fp = MD5.Str $ unsafePerformIO $ do
enc <- Encoding.getFileSystemEncoding
GHC.withCString enc fp $ GHC.peekCString Encoding.char8
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