enable canonicalizePath for non-GHC platforms

[haskell-directory.git] / System / Directory.hs

diff --git a/System/Directory.hs b/System/Directory.hs
index 5ff3e77..17fc358 100644 (file)
--- a/System/Directory.hs
+++ b/System/Directory.hs
@@ -79,6 +79,11 @@ import NHC.FFI
 import Hugs.Directory
 #endif /* __HUGS__ */
 
+#if defined(__GLASGOW_HASKELL__) || defined(mingw32_HOST_OS)
+import Foreign
+import Foreign.C
+#endif
+
 #ifdef __GLASGOW_HASKELL__
 import Prelude
 
@@ -87,8 +92,6 @@ import System.Posix.Types
 import System.Posix.Internals
 import System.Time             ( ClockTime(..) )
 import System.IO
-import Foreign
-import Foreign.C
 
 import GHC.IOBase      ( IOException(..), IOErrorType(..), ioException )
 
@@ -504,7 +507,37 @@ renameFile opath npath =
 
 {- |@'copyFile' old new@ copies the existing file from /old/ to /new/.
 If the /new/ file already exists, it is atomically replaced by the /old/ file.
-Neither path may refer to an existing directory.
+Neither path may refer to an existing directory.  The permissions of /old/ are
+copied to /new/, if possible.
+-}
+
+{- NOTES:
+
+It's tempting to try to remove the target file before opening it for
+writing.  This could be useful: for example if the target file is an
+executable that is in use, writing will fail, but unlinking first
+would succeed.
+
+However, it certainly isn't always what you want.
+
+ * if the target file is hardlinked, removing it would break
+   the hard link, but just opening would preserve it.
+
+ * opening and truncating will preserve permissions and
+   ACLs on the target.
+
+ * If the destination file is read-only in a writable directory,
+   we might want copyFile to fail.  Removing the target first
+   would succeed, however.
+
+ * If the destination file is special (eg. /dev/null), removing
+   it is probably not the right thing.  Copying to /dev/null
+   should leave /dev/null intact, not replace it with a plain
+   file.
+
+ * There's a small race condition between removing the target and
+   opening it for writing during which time someone might
+   create it again.
 -}
 copyFile :: FilePath -> FilePath -> IO ()
 copyFile fromFPath toFPath =
@@ -531,7 +564,6 @@ copyFile fromFPath toFPath =
                                copyContents hFrom hTo buffer
 #endif
 
-#ifdef __GLASGOW_HASKELL__
 -- | Given path referring to a file or directory, returns a
 -- canonicalized path, with the intent that two paths referring
 -- to the same file\/directory will map to the same canonicalized
@@ -564,11 +596,6 @@ foreign import ccall unsafe "realpath"
                               -> CString
                               -> IO CString
 #endif
-#else /* !__GLASGOW_HASKELL__ */
--- dummy implementation
-canonicalizePath :: FilePath -> IO FilePath
-canonicalizePath fpath = return fpath
-#endif /* !__GLASGOW_HASKELL__ */
 
 -- | Given an executable file name, searches for such file
 -- in the directories listed in system PATH. The returned value 
@@ -576,7 +603,32 @@ canonicalizePath fpath = return fpath
 -- such executable. For example (findExecutable \"ghc\")
 -- gives you the path to GHC.
 findExecutable :: String -> IO (Maybe FilePath)
-findExecutable binary = do
+findExecutable binary =
+#if defined(mingw32_HOST_OS)
+  withCString binary $ \c_binary ->
+  withCString ('.':exeExtension) $ \c_ext ->
+  allocaBytes long_path_size $ \pOutPath ->
+  alloca $ \ppFilePart -> do
+    res <- c_SearchPath nullPtr c_binary c_ext (fromIntegral long_path_size) pOutPath ppFilePart
+    if res > 0 && res < fromIntegral long_path_size
+      then do fpath <- peekCString pOutPath
+              return (Just fpath)
+      else return Nothing
+
+foreign import stdcall unsafe "SearchPathA"
+            c_SearchPath :: CString
+                         -> CString
+                         -> CString
+                         -> CInt
+                         -> CString
+                         -> Ptr CString
+                         -> IO CInt
+# if !defined(__GLASGOW_HASKELL__)
+long_path_size :: Int
+long_path_size = 4096
+# endif
+#else
+ do
   path <- getEnv "PATH"
   search (parseSearchPath path)
   where
@@ -589,6 +641,8 @@ findExecutable binary = do
        b <- doesFileExist path
        if b then return (Just path)
              else search ds
+#endif
+
 
 #ifdef __GLASGOW_HASKELL__
 {- |@'getDirectoryContents' dir@ returns a list of /all/ entries