git-annex/Backend/WORM.hs

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{- git-annex "WORM" backend -- Write Once, Read Many
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-
- Copyright 2010 Joey Hess <id@joeyh.name>
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-
- Licensed under the GNU GPL version 3 or higher.
-}
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module Backend.WORM (backends) where
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import Common.Annex
import Types.Backend
import Types.Key
import Types.KeySource
Better sanitization of problem characters when generating URL and WORM keys. FAT has a lot of characters it does not allow in filenames, like ? and * It's probably the worst offender, but other filesystems also have limitiations. In 2011, I made keyFile escape : to handle FAT, but missed the other characters. It also turns out that when I did that, I was also living dangerously; any existing keys that contained a : had their object location change. Oops. So, adding new characters to escape to keyFile is out. Well, it would be possible to make keyFile behave differently on a per-filesystem basis, but this would be a real nightmare to get right. Consider that a rsync special remote uses keyFile to determine the filenames to use, and we don't know the underlying filesystem on the rsync server.. Instead, I have gone for a solution that is backwards compatable and simple. Its only downside is that already generated URL and WORM keys might not be able to be stored on FAT or some other filesystem that dislikes a character used in the key. (In this case, the user can just migrate the problem keys to a checksumming backend. If this became a big problem, fsck could be made to detect these and suggest a migration.) Going forward, new keys that are created will escape all characters that are likely to cause problems. And if some filesystem comes along that's even worse than FAT (seems unlikely, but here it is 2013, and people are still using FAT!), additional characters can be added to the set that are escaped without difficulty. (Also, made WORM limit the part of the filename that is embedded in the key, to deal with filesystem filename length limits. This could have already been a problem, but is more likely now, since the escaping of the filename can make it longer.) This commit was sponsored by Ian Downes
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import Backend.Utilities
import Git.FilePath
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backends :: [Backend]
backends = [backend]
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backend :: Backend
backend = Backend
{ name = "WORM"
, getKey = keyValue
, verifyKeyContent = Nothing
, canUpgradeKey = Nothing
, fastMigrate = Nothing
, isStableKey = const True
}
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{- The key includes the file size, modification time, and the
- original filename relative to the top of the git repository.
-}
keyValue :: KeySource -> Annex (Maybe Key)
keyValue source = do
let f = contentLocation source
stat <- liftIO $ getFileStatus f
sz <- liftIO $ getFileSize' f stat
relf <- getTopFilePath <$> inRepo (toTopFilePath $ keyFilename source)
return $ Just $ stubKey
{ keyName = genKeyName relf
Better sanitization of problem characters when generating URL and WORM keys. FAT has a lot of characters it does not allow in filenames, like ? and * It's probably the worst offender, but other filesystems also have limitiations. In 2011, I made keyFile escape : to handle FAT, but missed the other characters. It also turns out that when I did that, I was also living dangerously; any existing keys that contained a : had their object location change. Oops. So, adding new characters to escape to keyFile is out. Well, it would be possible to make keyFile behave differently on a per-filesystem basis, but this would be a real nightmare to get right. Consider that a rsync special remote uses keyFile to determine the filenames to use, and we don't know the underlying filesystem on the rsync server.. Instead, I have gone for a solution that is backwards compatable and simple. Its only downside is that already generated URL and WORM keys might not be able to be stored on FAT or some other filesystem that dislikes a character used in the key. (In this case, the user can just migrate the problem keys to a checksumming backend. If this became a big problem, fsck could be made to detect these and suggest a migration.) Going forward, new keys that are created will escape all characters that are likely to cause problems. And if some filesystem comes along that's even worse than FAT (seems unlikely, but here it is 2013, and people are still using FAT!), additional characters can be added to the set that are escaped without difficulty. (Also, made WORM limit the part of the filename that is embedded in the key, to deal with filesystem filename length limits. This could have already been a problem, but is more likely now, since the escaping of the filename can make it longer.) This commit was sponsored by Ian Downes
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, keyBackendName = name backend
, keySize = Just sz
Better sanitization of problem characters when generating URL and WORM keys. FAT has a lot of characters it does not allow in filenames, like ? and * It's probably the worst offender, but other filesystems also have limitiations. In 2011, I made keyFile escape : to handle FAT, but missed the other characters. It also turns out that when I did that, I was also living dangerously; any existing keys that contained a : had their object location change. Oops. So, adding new characters to escape to keyFile is out. Well, it would be possible to make keyFile behave differently on a per-filesystem basis, but this would be a real nightmare to get right. Consider that a rsync special remote uses keyFile to determine the filenames to use, and we don't know the underlying filesystem on the rsync server.. Instead, I have gone for a solution that is backwards compatable and simple. Its only downside is that already generated URL and WORM keys might not be able to be stored on FAT or some other filesystem that dislikes a character used in the key. (In this case, the user can just migrate the problem keys to a checksumming backend. If this became a big problem, fsck could be made to detect these and suggest a migration.) Going forward, new keys that are created will escape all characters that are likely to cause problems. And if some filesystem comes along that's even worse than FAT (seems unlikely, but here it is 2013, and people are still using FAT!), additional characters can be added to the set that are escaped without difficulty. (Also, made WORM limit the part of the filename that is embedded in the key, to deal with filesystem filename length limits. This could have already been a problem, but is more likely now, since the escaping of the filename can make it longer.) This commit was sponsored by Ian Downes
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, keyMtime = Just $ modificationTime stat
}