146c36ca54
ghc 7.4 comaplains about use of System.IO.Error to catch exceptions. Ok, use Control.Exception, with variants specialized to only catch IO exceptions.
94 lines
3 KiB
Haskell
94 lines
3 KiB
Haskell
{- management of the git-annex journal and cache
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-
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- The journal is used to queue up changes before they are committed to the
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- git-annex branch. Amoung other things, it ensures that if git-annex is
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- interrupted, its recorded data is not lost.
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-
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- Copyright 2011 Joey Hess <joey@kitenet.net>
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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.Journal where
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import System.IO.Binary
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import Common.Annex
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import Annex.Exception
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import qualified Git
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{- Records content for a file in the branch to the journal.
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-
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- Using the journal, rather than immediatly staging content to the index
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- avoids git needing to rewrite the index after every change. -}
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setJournalFile :: FilePath -> String -> Annex ()
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setJournalFile file content = do
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g <- gitRepo
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liftIO $ doRedo (write g) $ do
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createDirectoryIfMissing True $ gitAnnexJournalDir g
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createDirectoryIfMissing True $ gitAnnexTmpDir g
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where
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-- journal file is written atomically
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write g = do
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let jfile = journalFile g file
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let tmpfile = gitAnnexTmpDir g </> takeFileName jfile
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writeBinaryFile tmpfile content
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moveFile tmpfile jfile
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{- Gets any journalled content for a file in the branch. -}
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getJournalFile :: FilePath -> Annex (Maybe String)
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getJournalFile file = inRepo $ \g -> catchMaybeIO $
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readFileStrict $ journalFile g file
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{- List of files that have updated content in the journal. -}
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getJournalledFiles :: Annex [FilePath]
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getJournalledFiles = map fileJournal <$> getJournalFiles
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{- List of existing journal files. -}
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getJournalFiles :: Annex [FilePath]
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getJournalFiles = do
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g <- gitRepo
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fs <- liftIO $
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catchDefaultIO (getDirectoryContents $ gitAnnexJournalDir g) []
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return $ filter (`notElem` [".", ".."]) fs
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{- Checks if there are changes in the journal. -}
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journalDirty :: Annex Bool
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journalDirty = not . null <$> getJournalFiles
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{- Produces a filename to use in the journal for a file on the branch.
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-
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- The journal typically won't have a lot of files in it, so the hashing
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- used in the branch is not necessary, and all the files are put directly
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- in the journal directory.
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-}
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journalFile :: Git.Repo -> FilePath -> FilePath
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journalFile repo file = gitAnnexJournalDir repo </> concatMap mangle file
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where
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mangle '/' = "_"
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mangle '_' = "__"
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mangle c = [c]
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{- Converts a journal file (relative to the journal dir) back to the
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- filename on the branch. -}
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fileJournal :: FilePath -> FilePath
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fileJournal = replace "//" "_" . replace "_" "/"
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{- Runs an action that modifies the journal, using locking to avoid
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- contention with other git-annex processes. -}
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lockJournal :: Annex a -> Annex a
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lockJournal a = do
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file <- fromRepo gitAnnexJournalLock
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bracketIO (lock file) unlock a
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where
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lock file = do
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l <- doRedo (createFile file stdFileMode) $
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createDirectoryIfMissing True $ takeDirectory file
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waitToSetLock l (WriteLock, AbsoluteSeek, 0, 0)
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return l
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unlock = closeFd
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{- Runs an action, catching failure and running something to fix it up, and
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- retrying if necessary. -}
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doRedo :: IO a -> IO b -> IO a
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doRedo a b = catchIO a $ const $ b >> a
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