43 lines
1.3 KiB
Haskell
43 lines
1.3 KiB
Haskell
{- git-annex file replacing
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-
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- Copyright 2013-2015 Joey Hess <id@joeyh.name>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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module Annex.ReplaceFile where
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import Annex.Common
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import Annex.Perms
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import Utility.Tmp
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{- Replaces a possibly already existing file with a new version,
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- atomically, by running an action.
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-
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- The action is passed the name of temp file, in a temp directory,
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- which it can write to, and once done the temp file is moved into place
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- and anything else in the temp directory is deleted.
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-
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- The action can throw an exception, in which case the temp directory
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- will be deleted, and the existing file will be preserved.
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-
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- Throws an IO exception when it was unable to replace the file.
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-}
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replaceFile :: FilePath -> (FilePath -> Annex ()) -> Annex ()
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replaceFile file action = do
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misctmpdir <- fromRepo gitAnnexTmpMiscDir
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void $ createAnnexDirectory misctmpdir
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filemax <- liftIO $ fileNameLengthLimit misctmpdir
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let basetmp = take (filemax `div` 2) (takeFileName file)
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withTmpDirIn misctmpdir basetmp $ \tmpdir -> do
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let tmpfile = tmpdir </> basetmp
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action tmpfile
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liftIO $ replaceFileFrom tmpfile file
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replaceFileFrom :: FilePath -> FilePath -> IO ()
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replaceFileFrom src dest = go `catchIO` fallback
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where
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go = moveFile src dest
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fallback _ = do
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createDirectoryIfMissing True $ parentDir dest
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go
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