propellor spin

2 files changed, 223 insertions, 0 deletions

diff --git a/Utility/FileMode.hs b/Utility/FileMode.hs
new file mode 100644
index 00000000..26692b3b
--- /dev/null
+++ b/Utility/FileMode.hs
@@ -0,0 +1,155 @@
+{- 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 System.IO
+import Control.Monad
+import Control.Exception (bracket)
+import System.PosixCompat.Types
+#ifndef mingw32_HOST_OS
+import System.Posix.Files
+#endif
+import Foreign (complement)
+
+import Utility.Exception
+
+{- 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 = withUmask nullFileMode a
+#else
+noUmask _ a = a
+#endif
+
+withUmask :: FileMode -> IO a -> IO a
+#ifndef mingw32_HOST_OS
+withUmask umask a = bracket setup cleanup go
+  where
+	setup = setFileCreationMask umask
+	cleanup = setFileCreationMask
+	go _ = a
+#else
+withUmask _ 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
+ - or written by anyone other than the current user,
+ - before any content is written.
+ -
+ - When possible, this is done using the umask.
+ -
+ - On a filesystem that does not support file permissions, this is the same
+ - as writeFile.
+ -}
+writeFileProtected :: FilePath -> String -> IO ()
+writeFileProtected file content = withUmask 0o0077 $
+	withFile file WriteMode $ \h -> do
+		void $ tryIO $ modifyFileMode file $
+			removeModes
+				[ groupReadMode, otherReadMode
+				, groupWriteMode, otherWriteMode
+				]
+		hPutStr h content
diff --git a/Utility/PartialPrelude.hs b/Utility/PartialPrelude.hs
new file mode 100644
index 00000000..6efa093f
--- /dev/null
+++ b/Utility/PartialPrelude.hs
@@ -0,0 +1,68 @@
+{- Parts of the Prelude are partial functions, which are a common source of
+ - bugs.
+ -
+ - This exports functions that conflict with the prelude, which avoids
+ - them being accidentially used.
+ -}
+
+module Utility.PartialPrelude where
+
+import qualified Data.Maybe
+
+{- read should be avoided, as it throws an error
+ - Instead, use: readish -}
+read :: Read a => String -> a
+read = Prelude.read
+
+{- head is a partial function; head [] is an error
+ - Instead, use: take 1 or headMaybe -}
+head :: [a] -> a
+head = Prelude.head
+
+{- tail is also partial
+ - Instead, use: drop 1 -}
+tail :: [a] -> [a]
+tail = Prelude.tail
+
+{- init too
+ - Instead, use: beginning -}
+init :: [a] -> [a]
+init = Prelude.init
+
+{- last too
+ - Instead, use: end or lastMaybe -}
+last :: [a] -> a
+last = Prelude.last
+
+{- Attempts to read a value from a String.
+ -
+ - Ignores leading/trailing whitespace, and throws away any trailing
+ - text after the part that can be read.
+ -
+ - readMaybe is available in Text.Read in new versions of GHC,
+ - but that one requires the entire string to be consumed.
+ -}
+readish :: Read a => String -> Maybe a
+readish s = case reads s of
+	((x,_):_) -> Just x
+	_ -> Nothing
+
+{- Like head but Nothing on empty list. -}
+headMaybe :: [a] -> Maybe a
+headMaybe = Data.Maybe.listToMaybe
+
+{- Like last but Nothing on empty list. -}
+lastMaybe :: [a] -> Maybe a
+lastMaybe [] = Nothing
+lastMaybe v = Just $ Prelude.last v
+
+{- All but the last element of a list.
+ - (Like init, but no error on an empty list.) -}
+beginning :: [a] -> [a]
+beginning [] = []
+beginning l = Prelude.init l
+
+{- Like last, but no error on an empty list. -}
+end :: [a] -> [a]
+end [] = []
+end l = [Prelude.last l]