WIP: removePathForcibly

OUTSTANDING ISSUES:
- No Windows support

System/Directory/Internal/C_utimensat.hsc

@@ -15,6 +15,7 @@ module System.Directory.Internal.C_utimensat where
 import Prelude ()
 import System.Directory.Internal.Prelude
 import Data.Time.Clock.POSIX (POSIXTime)
+import qualified System.Posix as Posix
 
 data CTimeSpec = CTimeSpec EpochTime CLong
 
@@ -29,9 +30,6 @@ instance Storable CTimeSpec where
       nsec <- #{peek struct timespec, tv_nsec} p
       return (CTimeSpec sec nsec)
 
-c_AT_FDCWD :: CInt
-c_AT_FDCWD = (#const AT_FDCWD)
-
 utimeOmit :: CTimeSpec
 utimeOmit = CTimeSpec (CTime 0) (#const UTIME_OMIT)
 
@@ -42,6 +40,6 @@ toCTimeSpec t = CTimeSpec (CTime sec) (truncate $ 10 ^ (9 :: Int) * frac)
     (sec', frac') = properFraction (toRational t)
 
 foreign import capi "sys/stat.h utimensat" c_utimensat
-  :: CInt -> CString -> Ptr CTimeSpec -> CInt -> IO CInt
+  :: Posix.Fd -> CString -> Ptr CTimeSpec -> CInt -> IO CInt
 
 #endif

System/Directory/Internal/Common.hs

@@ -126,6 +126,10 @@ ioeSetOsPath err =
     (mkUTF8 TransliterateCodingFailure)
     (mkUTF16le TransliterateCodingFailure)
 
+dropSpecialDotDirs :: [OsPath] -> [OsPath]
+dropSpecialDotDirs = filter f
+  where f filename = filename /= os "." && filename /= os ".."
+
 -- | Given a list of path segments, expand @.@ and @..@.  The path segments
 -- must not contain path separators.
 expandDots :: [OsPath] -> [OsPath]

System/Directory/Internal/Posix.hsc

@@ -1,9 +1,14 @@
+{-# LANGUAGE CApiFFI #-}
 module System.Directory.Internal.Posix where
 #include <HsDirectoryConfig.h>
 #if !defined(mingw32_HOST_OS)
+#include <fcntl.h>
 #ifdef HAVE_LIMITS_H
 # include <limits.h>
 #endif
+#ifdef HAVE_SYS_STAT_H
+# include <sys/stat.h>
+#endif
 import Prelude ()
 import System.Directory.Internal.Prelude
 #ifdef HAVE_UTIMENSAT
@@ -17,16 +22,36 @@ import System.OsPath ((</>), isRelative, splitSearchPath)
 import System.OsString.Internal.Types (OsString(OsString, getOsString))
 import qualified Data.Time.Clock.POSIX as POSIXTime
 import qualified System.OsPath.Internal as OsPath
+import qualified System.Posix.Directory.Fd as Posix
 import qualified System.Posix.Directory.PosixPath as Posix
 import qualified System.Posix.Env.PosixString as Posix
+import qualified System.Posix.Files as Posix (FileStatus(..))
 import qualified System.Posix.Files.PosixString as Posix
+import qualified System.Posix.Internals as Posix (CStat)
+import qualified System.Posix.IO.PosixString as Posix
 import qualified System.Posix.PosixPath.FilePath as Posix
 import qualified System.Posix.Types as Posix
 import qualified System.Posix.User.ByteString as Posix
 
 createDirectoryInternal :: OsPath -> IO ()
 createDirectoryInternal (OsString path) = Posix.createDirectory path 0o777
 
+c_AT_FDCWD :: Posix.Fd
+c_AT_FDCWD = Posix.Fd (#const AT_FDCWD)
+
+foreign import ccall "unistd.h unlinkat" c_unlinkat
+  :: Posix.Fd -> CString -> CInt -> IO CInt
+
+removePathAt :: FileType -> Maybe FileRef -> OsPath -> IO ()
+removePathAt fType dirRef (OsString path) =
+  Posix.withFilePath path $ \ pPath -> do
+    Posix.throwErrnoPathIfMinus1_ "unlinkat" path
+      (c_unlinkat (fromMaybe c_AT_FDCWD dirRef) pPath flag)
+    pure ()
+  where
+    flag | fileTypeIsDirectory fType = (#const AT_REMOVEDIR)
+         | otherwise                 = 0
+
 removePathInternal :: Bool -> OsPath -> IO ()
 removePathInternal True  = Posix.removeDirectory . getOsString
 removePathInternal False = Posix.removeLink . getOsString
@@ -101,9 +126,13 @@ exeExtensionInternal :: OsString
 exeExtensionInternal = exeExtension
 
 getDirectoryContentsInternal :: OsPath -> IO [OsPath]
-getDirectoryContentsInternal (OsString path) =
+getDirectoryContentsInternal path =
+  withFileRef Nothing path getDirectoryRefContents
+
+getDirectoryRefContents :: FileRef -> IO [OsPath]
+getDirectoryRefContents fileRef =
   bracket
-    (Posix.openDirStream path)
+    (Posix.unsafeOpenDirStreamFd =<< Posix.dup fileRef)
     Posix.closeDirStream
     start
   where
@@ -151,8 +180,63 @@ createSymbolicLink _ (OsString p1) (OsString p2) =
 readSymbolicLink :: OsPath -> IO OsPath
 readSymbolicLink = (OsString <$>) . Posix.readSymbolicLink . getOsString
 
+defaultFlags :: Posix.OpenFileFlags
+defaultFlags =
+  Posix.defaultFileFlags
+  { Posix.noctty = True
+  , Posix.nonBlock = True
+  , Posix.cloexec = True
+  }
+
+type FileRef = Posix.Fd
+
+withFileRef :: Maybe FileRef -> OsPath -> (FileRef -> IO r) -> IO r
+withFileRef dirRef (OsString name) =
+  bracket
+    (Posix.openFdAt dirRef name Posix.ReadOnly defaultFlags)
+    Posix.closeFd
+
+data Subref = NotSubdir -- ^ Not a directory (perhaps regular file or symlink).
+            | SubdirRef FileRef -- ^ Is a subdirectory.
+            deriving (Show)
+
+openSubref :: Maybe FileRef -> OsPath -> IO Subref
+openSubref dirRef (OsString name) = do
+  let flags = defaultFlags { Posix.nofollow = True, Posix.directory = True }
+  result <- tryIOError (Posix.openFdAt dirRef name Posix.ReadOnly flags)
+  case result of
+    Left err -> do
+      errno <- getErrno
+      if errno == eLOOP || errno == eNOTDIR
+        then pure NotSubdir
+        else throwIO err
+    Right ref -> pure (SubdirRef ref)
+
+closeSubref :: Subref -> IO ()
+closeSubref  NotSubdir      = pure ()
+closeSubref (SubdirRef ref) = Posix.closeFd ref
+
+withSubref :: Maybe FileRef -> OsPath -> (Subref -> IO r) -> IO r
+withSubref dirRef name action =
+  bracket (openSubref dirRef name) closeSubref action
+
 type Metadata = Posix.FileStatus
 
+foreign import capi "sys/stat.h fstatat" c_fstatat
+  :: Posix.Fd -> CString -> Ptr Posix.CStat -> CInt -> IO CInt
+
+c_AT_SYMLINK_NOFOLLOW :: CInt
+c_AT_SYMLINK_NOFOLLOW = (#const AT_SYMLINK_NOFOLLOW)
+
+getSymbolicLinkMetadataAt :: Maybe FileRef -> OsPath -> IO Metadata
+getSymbolicLinkMetadataAt dirRef (OsString path) =
+  Posix.withFilePath path $ \ pPath -> do
+    stat <- mallocForeignPtrBytes (#const sizeof(struct stat))
+    withForeignPtr stat $ \ pStat -> do
+      Posix.throwErrnoPathIfMinus1_ "fstatat" path $ do
+        c_fstatat (fromMaybe c_AT_FDCWD dirRef) pPath pStat c_AT_SYMLINK_NOFOLLOW
+    pure (Posix.FileStatus stat)
+
 getSymbolicLinkMetadata :: OsPath -> IO Metadata
 getSymbolicLinkMetadata = Posix.getSymbolicLinkStatus . getOsString
 
@@ -197,6 +281,20 @@ setWriteMode :: Bool -> Mode -> Mode
 setWriteMode False m = m .&. complement allWriteMode
 setWriteMode True  m = m .|. allWriteMode
 
+foreign import capi "sys/stat.h fchmodat" c_fchmodat
+  :: Posix.Fd -> CString -> Posix.FileMode -> CInt -> IO CInt
+
+setSymbolicLinkModeAt :: Maybe FileRef -> OsPath -> Posix.FileMode -> IO ()
+setSymbolicLinkModeAt dirRef (OsString path) mode = do
+  Posix.withFilePath path $ \ pPath ->
+    Posix.throwErrnoPathIfMinus1_ "fchmodat" path
+      (c_fchmodat (fromMaybe c_AT_FDCWD dirRef) pPath mode c_AT_SYMLINK_NOFOLLOW)
+
+forceRemovable :: Maybe FileRef -> OsPath -> Metadata -> IO ()
+forceRemovable dirRef path metadata = do
+  let mode = modeFromMetadata metadata .|. Posix.ownerModes
+  setSymbolicLinkModeAt dirRef path mode
+
 setFileMode :: OsPath -> Mode -> IO ()
 setFileMode = Posix.setFileMode . getOsString
 

System/Directory/Internal/Prelude.hs

@@ -80,11 +80,13 @@ import Foreign
   , allocaArray
   , allocaBytes
   , allocaBytesAligned
+  , mallocForeignPtrBytes
   , maybeWith
   , nullPtr
   , plusPtr
   , with
   , withArray
+  , withForeignPtr
   )
 import Foreign.C
   ( CInt(..)
@@ -96,6 +98,9 @@ import Foreign.C
   , CUShort(..)
   , CWString
   , CWchar(..)
+  , eLOOP
+  , eNOTDIR
+  , getErrno
   , throwErrnoIfMinus1Retry_
   , throwErrnoIfMinus1_
   , throwErrnoIfNull

System/Directory/OsPath.hs

@@ -441,6 +441,23 @@ removeContentsRecursive path =
     for_ [path </> x | x <- cont] removePathRecursive
     removeDirectory path
 
+type Preremover = Maybe FileRef -> OsPath -> IO ()
+
+removeRecursiveAt :: Preremover -> Maybe FileRef -> OsPath -> IO ()
+removeRecursiveAt preremover dirRef name = do
+  preremover dirRef name
+  withSubref dirRef name $ \ subref -> do
+    case subref of
+      NotSubdir -> do
+        removePathAt File dirRef name -- TODO: What about windows dir links?
+      SubdirRef subdirRef -> do
+        -- dropSpecialDotDirs is very crucial! Otherwise it will recurse
+        -- into the parent directory and do terrible things.
+        names <- dropSpecialDotDirs <$> getDirectoryRefContents subdirRef
+        sequenceWithIOErrors_ $
+          (removeRecursiveAt preremover (Just subdirRef) <$> names) <>
+          [removePathAt Directory dirRef name]
+
 -- | Removes a file or directory at /path/ together with its contents and
 -- subdirectories. Symbolic links are removed without affecting their
 -- targets. If the path does not exist, nothing happens.
@@ -461,32 +478,21 @@ removePathForcibly :: OsPath -> IO ()
 removePathForcibly path =
   (`ioeAddLocation` "removePathForcibly") `modifyIOError` do
     ignoreDoesNotExistError $ do
-      m <- getSymbolicLinkMetadata path
-      case fileTypeFromMetadata m of
-        DirectoryLink -> do
-          makeRemovable path
-          removeDirectory path
-        Directory -> do
-          makeRemovable path
-          names <- listDirectory path
-          sequenceWithIOErrors_ $
-            [ removePathForcibly (path </> name) | name <- names ] ++
-            [ removeDirectory path ]
-        _ -> do
-          unless filesAlwaysRemovable (makeRemovable path)
-          removeFile path
+      removeRecursiveAt makeRemovable Nothing path
+
   where
 
     ignoreDoesNotExistError :: IO () -> IO ()
     ignoreDoesNotExistError action =
       () <$ tryIOErrorType isDoesNotExistError action
 
-    makeRemovable :: OsPath -> IO ()
-    makeRemovable p = (`catchIOError` \ _ -> pure ()) $ do
-      perms <- getPermissions p
-      setPermissions path perms{ readable = True
-                               , searchable = True
-                               , writable = True }
+    makeRemovable :: Maybe FileRef -> OsPath -> IO ()
+    makeRemovable dirRef name = do
+      metadata <- getSymbolicLinkMetadataAt dirRef name
+      when (fileTypeIsDirectory (fileTypeFromMetadata metadata)
+            || not filesAlwaysRemovable) $ do
+        forceRemovable dirRef name metadata
+          `catchIOError` \ _ -> pure ()
 
 {- |'removeFile' /file/ removes the directory entry for an existing file
 /file/, where /file/ is not itself a directory. The
@@ -1140,8 +1146,7 @@ getDirectoryContents path =
 --   @[ENOTDIR]@
 --
 listDirectory :: OsPath -> IO [OsPath]
-listDirectory path = filter f <$> getDirectoryContents path
-  where f filename = filename /= os "." && filename /= os ".."
+listDirectory path = dropSpecialDotDirs <$> getDirectoryContents path
 
 -- | Obtain the current working directory as an absolute path.
 --