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+{- More control over touching a file.
+ -
+ - Copyright 2011 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+{-# LANGUAGE ForeignFunctionInterface #-}
+
+module Touch (
+	TimeSpec(..),
+	now,
+	omit,
+	touchBoth,
+	touch
+) where
+
+import Foreign
+import Foreign.C
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#let alignment t = "%lu", (unsigned long)offsetof(struct {char x__; t (y__); }, y__)
+
+data TimeSpec = TimeSpec CTime CLong
+
+instance Storable TimeSpec where
+	alignment _ = #{alignment struct timespec}
+	sizeOf _ = #{size struct timespec}
+	peek ptr = do
+		sec <- #{peek struct timespec, tv_sec} ptr
+		nsec <- #{peek struct timespec, tv_nsec} ptr
+		return $ TimeSpec sec nsec
+	poke ptr (TimeSpec sec nsec) = do
+		#{poke struct timespec, tv_sec} ptr sec
+		#{poke struct timespec, tv_nsec} ptr nsec
+
+{- special timespecs -}
+omit :: TimeSpec
+omit = TimeSpec 0 #const UTIME_OMIT
+now :: TimeSpec
+now = TimeSpec 0 #const UTIME_NOW
+
+{- While its interface is beastly, utimensat is in recent
+   POSIX standards, unlike futimes. -}
+foreign import ccall "utimensat" 
+	c_utimensat :: CInt -> CString -> Ptr TimeSpec -> CInt -> IO CInt
+
+{- Changes the access and/or modification times of a file.
+   Can follow symlinks, or not. -}
+touchBoth :: FilePath -> TimeSpec -> TimeSpec -> Bool -> IO Bool
+touchBoth file atime mtime follow = 
+	allocaArray 2 $ \ptr ->
+	withCString file $ \f -> do
+		pokeArray ptr [atime, mtime]
+		r <- c_utimensat at_fdcwd f ptr flags
+		putStrLn $ "ret " ++ (show r)
+		return (r == 0)
+	where
+		at_fdcwd = #const AT_FDCWD
+		at_symlink_nofollow = #const AT_SYMLINK_NOFOLLOW
+
+		flags = if follow
+			then 0
+			else at_symlink_nofollow 
+
+touch :: FilePath -> TimeSpec -> Bool -> IO Bool
+touch file mtime follow = touchBoth file omit mtime follow