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|
{- management of the git-annex journal
-
- The journal is used to queue up changes before they are committed to the
- git-annex branch. Among other things, it ensures that if git-annex is
- interrupted, its recorded data is not lost.
-
- Copyright 2011-2013 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
{-# LANGUAGE CPP #-}
module Annex.Journal where
import System.IO.Binary
import Common.Annex
import Annex.Exception
import qualified Git
import Annex.Perms
#ifdef mingw32_HOST_OS
import Utility.WinLock
#endif
{- Records content for a file in the branch to the journal.
-
- Using the journal, rather than immediatly staging content to the index
- avoids git needing to rewrite the index after every change.
-
- The file in the journal is updated atomically, which allows
- getJournalFileStale to always return a consistent journal file
- content, although possibly not the most current one.
-}
setJournalFile :: JournalLocked -> FilePath -> String -> Annex ()
setJournalFile _jl file content = do
createAnnexDirectory =<< fromRepo gitAnnexJournalDir
createAnnexDirectory =<< fromRepo gitAnnexTmpDir
-- journal file is written atomically
jfile <- fromRepo $ journalFile file
tmp <- fromRepo gitAnnexTmpDir
let tmpfile = tmp </> takeFileName jfile
liftIO $ do
writeBinaryFile tmpfile content
moveFile tmpfile jfile
{- Gets any journalled content for a file in the branch. -}
getJournalFile :: JournalLocked -> FilePath -> Annex (Maybe String)
getJournalFile _jl = getJournalFileStale
{- Without locking, this is not guaranteed to be the most recent
- version of the file in the journal, so should not be used as a basis for
- changes. -}
getJournalFileStale :: FilePath -> Annex (Maybe String)
getJournalFileStale file = inRepo $ \g -> catchMaybeIO $
readFileStrict $ journalFile file g
{- List of files that have updated content in the journal. -}
getJournalledFiles :: JournalLocked -> Annex [FilePath]
getJournalledFiles jl = map fileJournal <$> getJournalFiles jl
getJournalledFilesStale :: Annex [FilePath]
getJournalledFilesStale = map fileJournal <$> getJournalFilesStale
{- List of existing journal files. -}
getJournalFiles :: JournalLocked -> Annex [FilePath]
getJournalFiles _jl = getJournalFilesStale
{- List of existing journal files, but without locking, may miss new ones
- just being added, or may have false positives if the journal is staged
- as it is run. -}
getJournalFilesStale :: Annex [FilePath]
getJournalFilesStale = do
g <- gitRepo
fs <- liftIO $ catchDefaultIO [] $
getDirectoryContents $ gitAnnexJournalDir g
return $ filter (`notElem` [".", ".."]) fs
{- Checks if there are changes in the journal. -}
journalDirty :: Annex Bool
journalDirty = not . null <$> getJournalFilesStale
{- Produces a filename to use in the journal for a file on the branch.
-
- The journal typically won't have a lot of files in it, so the hashing
- used in the branch is not necessary, and all the files are put directly
- in the journal directory.
-}
journalFile :: FilePath -> Git.Repo -> FilePath
journalFile file repo = gitAnnexJournalDir repo </> concatMap mangle file
where
mangle c
| c == pathSeparator = "_"
| c == '_' = "__"
| otherwise = [c]
{- Converts a journal file (relative to the journal dir) back to the
- filename on the branch. -}
fileJournal :: FilePath -> FilePath
fileJournal = replace [pathSeparator, pathSeparator] "_" .
replace "_" [pathSeparator]
{- Sentinal value, only produced by lockJournal; required
- as a parameter by things that need to ensure the journal is
- locked. -}
data JournalLocked = ProduceJournalLocked
{- Runs an action that modifies the journal, using locking to avoid
- contention with other git-annex processes. -}
lockJournal :: (JournalLocked -> Annex a) -> Annex a
lockJournal a = do
lockfile <- fromRepo gitAnnexJournalLock
createAnnexDirectory $ takeDirectory lockfile
mode <- annexFileMode
bracketIO (lock lockfile mode) unlock (const $ a ProduceJournalLocked)
where
#ifndef mingw32_HOST_OS
lock lockfile mode = do
l <- noUmask mode $ createFile lockfile mode
waitToSetLock l (WriteLock, AbsoluteSeek, 0, 0)
return l
unlock = closeFd
#else
lock lockfile _mode = waitToLock $ lockExclusive lockfile
unlock = dropLock
#endif
|
