Wrap fsync(2) and fdatasync(2)

This adds two new functions in `System.Posix.Unistd`

 - `fileSynchronise` (aka `fsync(2)`), and
 - `fileSynchroniseDataOnly` (aka `fdatasync(2)`)

This is based on part of #7 and has been heavily refactored from its
original patch submission by Ricardo Catalinas Jiménez.

This also bumps version to 2.7.1.0 as a minor version bump is now needed.

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>

1 files changed, 52 insertions, 0 deletions

diff --git a/System/Posix/Unistd.hsc b/System/Posix/Unistd.hsc
index 0a13d6d..afb8c08 100644
--- a/System/Posix/Unistd.hsc
+++ b/System/Posix/Unistd.hsc
@@ -1,3 +1,4 @@
+{-# LANGUAGE CApiFFI #-}
 {-# LANGUAGE NondecreasingIndentation #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
@@ -27,6 +28,10 @@ module System.Posix.Unistd (
     -- * Sleeping
     sleep, usleep, nanosleep,
 
+    -- * File synchronisation
+    fileSynchronise,
+    fileSynchroniseDataOnly,
+
   {-
     ToDo from unistd.h:
       confstr,
@@ -55,8 +60,14 @@ import Foreign.C.Error
 import Foreign.C.String ( peekCString )
 import Foreign.C.Types
 import Foreign
+import System.Posix.Types
 import System.Posix.Internals
 
+#if !(HAVE_FSYNC && HAVE_FDATASYNC)
+import System.IO.Error ( ioeSetLocation )
+import GHC.IO.Exception ( unsupportedOperation )
+#endif
+
 -- -----------------------------------------------------------------------------
 -- System environment (uname())
 
@@ -206,3 +217,44 @@ sysconf n = do
 
 foreign import ccall unsafe "sysconf"
   c_sysconf :: CInt -> IO CLong
+
+-- -----------------------------------------------------------------------------
+-- File synchronization
+
+-- | Performs @fsync(2)@ operation on file-descriptor.
+--
+-- Throws 'IOError' (\"unsupported operation\") if platform does not
+-- provide @fsync(2)@ (use @#if HAVE_FSYNC@ CPP guard to
+-- detect availability).
+fileSynchronise :: Fd -> IO ()
+#if HAVE_FSYNC
+fileSynchronise fd = do
+  throwErrnoIfMinus1_ "fileSynchronise" (c_fsync fd)
+
+foreign import capi safe "unistd.h fsync"
+  c_fsync :: Fd -> IO CInt
+#else
+{-# WARNING fileSynchronise
+    "operation will throw exception (CPP guard: @#if HAVE_FSYNC@)" #-}
+fileSynchronise _ = ioError (ioeSetLocation unsupportedOperation
+                             "fileSynchronise")
+#endif
+
+-- | Performs @fdatasync(2)@ operation on file-descriptor.
+--
+-- Throws 'IOError' (\"unsupported operation\") if platform does not
+-- provide @fdatasync(2)@ (use @#if HAVE_FDATASYNC@ CPP guard to
+-- detect availability).
+fileSynchroniseDataOnly :: Fd -> IO ()
+#if HAVE_FDATASYNC
+fileSynchroniseDataOnly fd = do
+  throwErrnoIfMinus1_ "fileSynchroniseDataOnly" (c_fdatasync fd)
+
+foreign import capi safe "unistd.h fdatasync"
+  c_fdatasync :: Fd -> IO CInt
+#else
+{-# WARNING fileSynchroniseDataOnly
+    "operation will throw exception (CPP guard: @#if HAVE_FDATASYNC@)" #-}
+fileSynchroniseDataOnly _ = ioError (ioeSetLocation unsupportedOperation
+                                     "fileSynchroniseDataOnly")
+#endif