38 lines
1.2 KiB
Haskell
38 lines
1.2 KiB
Haskell
{- git-annex "WORM" backend -- Write Once, Read Many
|
|
- -}
|
|
|
|
module Backend.WORM (backend) where
|
|
|
|
import Control.Monad.State
|
|
import qualified Backend.File
|
|
import BackendTypes
|
|
import Utility
|
|
import System.FilePath
|
|
import System.Posix.Files
|
|
import Data.Digest.Pure.SHA -- slow, but we only checksum filenames
|
|
import qualified Data.ByteString.Lazy.Char8 as B
|
|
|
|
backend = Backend.File.backend {
|
|
name = "WORM",
|
|
getKey = keyValue
|
|
}
|
|
|
|
-- A SHA1 of the basename of the filename, plus the file size and
|
|
-- modification time, is used as the unique part of the key. That
|
|
-- allows multiple files with the same names to have different keys,
|
|
-- while also allowing a file to be moved around while retaining the
|
|
-- same key.
|
|
--
|
|
-- The basename of the filename is also included in the key, so it's clear
|
|
-- what the original filename was when a user sees the value.
|
|
keyValue :: FilePath -> Annex (Maybe Key)
|
|
keyValue file = do
|
|
stat <- liftIO $ getFileStatus file
|
|
return $ Just $ Key ((name backend), key stat)
|
|
where
|
|
key stat = (checksum $ uniqueid stat) ++ sep ++ base
|
|
checksum s = show $ sha1 $ B.pack s
|
|
uniqueid stat = (show $ fileSize stat) ++ sep ++
|
|
(show $ modificationTime stat)
|
|
base = takeFileName file
|
|
sep = ":"
|