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|
{- Temporary files.
-
- Copyright 2010-2020 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
{-# LANGUAGE CPP #-}
{-# OPTIONS_GHC -fno-warn-tabs #-}
module Utility.Tmp (
Template,
viaTmp,
withTmpFile,
withTmpFileIn,
relatedTemplate,
openTmpFileIn,
) where
import System.IO
import System.FilePath
import System.Directory
import Control.Monad.IO.Class
import System.IO.Error
import Utility.Exception
import Utility.FileSystemEncoding
import Utility.FileMode
import qualified Utility.RawFilePath as R
type Template = String
{- This is the same as openTempFile, except when there is an
- error, it displays the template as well as the directory,
- to help identify what call was responsible.
-}
openTmpFileIn :: FilePath -> String -> IO (FilePath, Handle)
openTmpFileIn dir template = openTempFile dir template
`catchIO` decoraterrror
where
decoraterrror e = throwM $
let loc = ioeGetLocation e ++ " template " ++ template
in annotateIOError e loc Nothing Nothing
{- Runs an action like writeFile, writing to a temp file first and
- then moving it into place. The temp file is stored in the same
- directory as the final file to avoid cross-device renames.
-
- While this uses a temp file, the file will end up with the same
- mode as it would when using writeFile, unless the writer action changes
- it.
-}
viaTmp :: (MonadMask m, MonadIO m) => (FilePath -> v -> m ()) -> FilePath -> v -> m ()
viaTmp a file content = bracketIO setup cleanup use
where
(dir, base) = splitFileName file
template = relatedTemplate (base ++ ".tmp")
setup = do
createDirectoryIfMissing True dir
openTmpFileIn dir template
cleanup (tmpfile, h) = do
_ <- tryIO $ hClose h
tryIO $ removeFile tmpfile
use (tmpfile, h) = do
let tmpfile' = toRawFilePath tmpfile
-- Make mode the same as if the file were created usually,
-- not as a temp file. (This may fail on some filesystems
-- that don't support file modes well, so ignore
-- exceptions.)
_ <- liftIO $ tryIO $ R.setFileMode tmpfile' =<< defaultFileMode
liftIO $ hClose h
a tmpfile content
liftIO $ R.rename tmpfile' (toRawFilePath file)
{- Runs an action with a tmp file located in the system's tmp directory
- (or in "." if there is none) then removes the file. -}
withTmpFile :: (MonadIO m, MonadMask m) => Template -> (FilePath -> Handle -> m a) -> m a
withTmpFile template a = do
tmpdir <- liftIO $ catchDefaultIO "." getTemporaryDirectory
withTmpFileIn tmpdir template a
{- Runs an action with a tmp file located in the specified directory,
- then removes the file.
-
- Note that the tmp file will have a file mode that only allows the
- current user to access it.
-}
withTmpFileIn :: (MonadIO m, MonadMask m) => FilePath -> Template -> (FilePath -> Handle -> m a) -> m a
withTmpFileIn tmpdir template a = bracket create remove use
where
create = liftIO $ openTmpFileIn tmpdir template
remove (name, h) = liftIO $ do
hClose h
catchBoolIO (removeFile name >> return True)
use (name, h) = a name h
{- It's not safe to use a FilePath of an existing file as the template
- for openTempFile, because if the FilePath is really long, the tmpfile
- will be longer, and may exceed the maximum filename length.
-
- This generates a template that is never too long.
- (Well, it allocates 20 characters for use in making a unique temp file,
- anyway, which is enough for the current implementation and any
- likely implementation.)
-}
relatedTemplate :: FilePath -> FilePath
relatedTemplate f
| len > 20 = truncateFilePath (len - 20) f
| otherwise = f
where
len = length f
|
