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+{- File mode utilities.
+ -
+ - Copyright 2010-2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+{-# LANGUAGE CPP #-}
+
+module Utility.FileMode where
+
+import Common
+
+import Control.Exception (bracket)
+import System.PosixCompat.Types
+#ifndef mingw32_HOST_OS
+import System.Posix.Files
+#endif
+import Foreign (complement)
+
+{- Applies a conversion function to a file's mode. -}
+modifyFileMode :: FilePath -> (FileMode -> FileMode) -> IO ()
+modifyFileMode f convert = void $ modifyFileMode' f convert
+modifyFileMode' :: FilePath -> (FileMode -> FileMode) -> IO FileMode
+modifyFileMode' f convert = do
+ s <- getFileStatus f
+ let old = fileMode s
+ let new = convert old
+ when (new /= old) $
+ setFileMode f new
+ return old
+
+{- Adds the specified FileModes to the input mode, leaving the rest
+ - unchanged. -}
+addModes :: [FileMode] -> FileMode -> FileMode
+addModes ms m = combineModes (m:ms)
+
+{- Removes the specified FileModes from the input mode. -}
+removeModes :: [FileMode] -> FileMode -> FileMode
+removeModes ms m = m `intersectFileModes` complement (combineModes ms)
+
+{- Runs an action after changing a file's mode, then restores the old mode. -}
+withModifiedFileMode :: FilePath -> (FileMode -> FileMode) -> IO a -> IO a
+withModifiedFileMode file convert a = bracket setup cleanup go
+ where
+ setup = modifyFileMode' file convert
+ cleanup oldmode = modifyFileMode file (const oldmode)
+ go _ = a
+
+writeModes :: [FileMode]
+writeModes = [ownerWriteMode, groupWriteMode, otherWriteMode]
+
+readModes :: [FileMode]
+readModes = [ownerReadMode, groupReadMode, otherReadMode]
+
+executeModes :: [FileMode]
+executeModes = [ownerExecuteMode, groupExecuteMode, otherExecuteMode]
+
+{- Removes the write bits from a file. -}
+preventWrite :: FilePath -> IO ()
+preventWrite f = modifyFileMode f $ removeModes writeModes
+
+{- Turns a file's owner write bit back on. -}
+allowWrite :: FilePath -> IO ()
+allowWrite f = modifyFileMode f $ addModes [ownerWriteMode]
+
+{- Turns a file's owner read bit back on. -}
+allowRead :: FilePath -> IO ()
+allowRead f = modifyFileMode f $ addModes [ownerReadMode]
+
+{- Allows owner and group to read and write to a file. -}
+groupSharedModes :: [FileMode]
+groupSharedModes =
+ [ ownerWriteMode, groupWriteMode
+ , ownerReadMode, groupReadMode
+ ]
+
+groupWriteRead :: FilePath -> IO ()
+groupWriteRead f = modifyFileMode f $ addModes groupSharedModes
+
+checkMode :: FileMode -> FileMode -> Bool
+checkMode checkfor mode = checkfor `intersectFileModes` mode == checkfor
+
+{- Checks if a file mode indicates it's a symlink. -}
+isSymLink :: FileMode -> Bool
+#ifdef mingw32_HOST_OS
+isSymLink _ = False
+#else
+isSymLink = checkMode symbolicLinkMode
+#endif
+
+{- Checks if a file has any executable bits set. -}
+isExecutable :: FileMode -> Bool
+isExecutable mode = combineModes executeModes `intersectFileModes` mode /= 0
+
+{- Runs an action without that pesky umask influencing it, unless the
+ - passed FileMode is the standard one. -}
+noUmask :: FileMode -> IO a -> IO a
+#ifndef mingw32_HOST_OS
+noUmask mode a
+ | mode == stdFileMode = a
+ | otherwise = bracket setup cleanup go
+ where
+ setup = setFileCreationMask nullFileMode
+ cleanup = setFileCreationMask
+ go _ = a
+#else
+noUmask _ a = a
+#endif
+
+combineModes :: [FileMode] -> FileMode
+combineModes [] = undefined
+combineModes [m] = m
+combineModes (m:ms) = foldl unionFileModes m ms
+
+isSticky :: FileMode -> Bool
+#ifdef mingw32_HOST_OS
+isSticky _ = False
+#else
+isSticky = checkMode stickyMode
+
+stickyMode :: FileMode
+stickyMode = 512
+
+setSticky :: FilePath -> IO ()
+setSticky f = modifyFileMode f $ addModes [stickyMode]
+#endif
+
+{- Writes a file, ensuring that its modes do not allow it to be read
+ - by anyone other than the current user, before any content is written.
+ -
+ - On a filesystem that does not support file permissions, this is the same
+ - as writeFile.
+ -}
+writeFileProtected :: FilePath -> String -> IO ()
+writeFileProtected file content = do
+ h <- openFile file WriteMode
+ void $ tryIO $
+ modifyFileMode file $
+ removeModes [groupReadMode, otherReadMode]
+ hPutStr h content
+ hClose h