70 lines
1.8 KiB
Haskell
70 lines
1.8 KiB
Haskell
{- git-annex "WORM" backend -- Write Once, Read Many
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-
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- Copyright 2010 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 Backend.WORM (backend) where
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import Control.Monad.State
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import System.FilePath
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import System.Posix.Files
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import System.Posix.Types
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import System.Directory
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import Data.String.Utils
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import qualified Backend.File
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import TypeInternals
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import Locations
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import qualified Annex
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import Core
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import Messages
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backend :: Backend
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backend = Backend.File.backend {
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name = "WORM",
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getKey = keyValue,
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fsckKey = Backend.File.checkKey checkKeySize
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}
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-- The key is formed from the file size, modification time, and the
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-- basename of the filename.
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--
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-- That allows multiple files with the same names to have different keys,
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-- while also allowing a file to be moved around while retaining the
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-- same key.
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keyValue :: FilePath -> Annex (Maybe Key)
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keyValue file = do
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stat <- liftIO $ getFileStatus file
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return $ Just $ Key (name backend, key stat)
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where
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key stat = uniqueid stat ++ sep ++ base
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uniqueid stat = show (modificationTime stat) ++ sep ++
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show (fileSize stat)
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base = takeFileName file
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sep = ":"
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{- Extracts the file size from a key. -}
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keySize :: Key -> FileOffset
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keySize key = read $ section !! 1
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where
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section = split ":" (keyName key)
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{- The size of the data for a key is checked against the size encoded in
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- the key. Note that the modification time is not checked. -}
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checkKeySize :: Key -> Annex Bool
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checkKeySize key = do
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g <- Annex.gitRepo
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let file = annexLocation g key
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present <- liftIO $ doesFileExist file
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if not present
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then return True
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else do
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s <- liftIO $ getFileStatus file
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if fileSize s == keySize key
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then return True
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else do
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dest <- moveBad key
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warning $ "Bad file size; moved to "++dest
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return False
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