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|
{- streaming directory traversal
-
- Copyright 2011-2018 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE LambdaCase #-}
{-# OPTIONS_GHC -fno-warn-tabs #-}
module Utility.Directory.Stream (
DirectoryHandle,
openDirectory,
closeDirectory,
readDirectory,
isDirectoryEmpty,
) where
import Control.Monad
import System.FilePath
import Control.Concurrent
import Data.Maybe
import Prelude
#ifdef mingw32_HOST_OS
import qualified System.Win32 as Win32
#else
import qualified System.Posix as Posix
#endif
import Utility.Directory
import Utility.Exception
#ifndef mingw32_HOST_OS
data DirectoryHandle = DirectoryHandle IsOpen Posix.DirStream
#else
data DirectoryHandle = DirectoryHandle IsOpen Win32.HANDLE Win32.FindData (MVar ())
#endif
type IsOpen = MVar () -- full when the handle is open
openDirectory :: FilePath -> IO DirectoryHandle
openDirectory path = do
#ifndef mingw32_HOST_OS
dirp <- Posix.openDirStream path
isopen <- newMVar ()
return (DirectoryHandle isopen dirp)
#else
(h, fdat) <- Win32.findFirstFile (path </> "*")
-- Indicate that the fdat contains a filename that readDirectory
-- has not yet returned, by making the MVar be full.
-- (There's always at least a "." entry.)
alreadyhave <- newMVar ()
isopen <- newMVar ()
return (DirectoryHandle isopen h fdat alreadyhave)
#endif
closeDirectory :: DirectoryHandle -> IO ()
#ifndef mingw32_HOST_OS
closeDirectory (DirectoryHandle isopen dirp) =
whenOpen isopen $
Posix.closeDirStream dirp
#else
closeDirectory (DirectoryHandle isopen h _ alreadyhave) =
whenOpen isopen $ do
_ <- tryTakeMVar alreadyhave
Win32.findClose h
#endif
where
whenOpen :: IsOpen -> IO () -> IO ()
whenOpen mv f = do
v <- tryTakeMVar mv
when (isJust v) f
-- | Reads the next entry from the handle. Once the end of the directory
-- is reached, returns Nothing and automatically closes the handle.
readDirectory :: DirectoryHandle -> IO (Maybe FilePath)
#ifndef mingw32_HOST_OS
readDirectory hdl@(DirectoryHandle _ dirp) = do
e <- Posix.readDirStream dirp
if null e
then do
closeDirectory hdl
return Nothing
else return (Just e)
#else
readDirectory hdl@(DirectoryHandle _ h fdat mv) = do
-- If the MVar is full, then the filename in fdat has
-- not yet been returned. Otherwise, need to find the next
-- file.
r <- tryTakeMVar mv
case r of
Just () -> getfn
Nothing -> do
more <- Win32.findNextFile h fdat
if more
then getfn
else do
closeDirectory hdl
return Nothing
where
getfn = do
filename <- Win32.getFindDataFileName fdat
return (Just filename)
#endif
-- | True only when directory exists and contains nothing.
-- Throws exception if directory does not exist.
isDirectoryEmpty :: FilePath -> IO Bool
isDirectoryEmpty d = bracket (openDirectory d) closeDirectory check
where
check h = do
v <- readDirectory h
case v of
Nothing -> return True
Just f
| not (dirCruft f) -> return False
| otherwise -> check h
|
