92d5d81c2c
However, directory still uses its optimzed chunked file writer, as it uses less memory than the generic one in the helper.
121 lines
4.1 KiB
Haskell
121 lines
4.1 KiB
Haskell
{- git-annex chunked remotes
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-
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- Copyright 2012 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 Remote.Helper.Chunked where
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import Common.Annex
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import Utility.DataUnits
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import Types.Remote
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import qualified Data.Map as M
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import qualified Data.ByteString.Lazy as L
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import Data.Int
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import qualified Control.Exception as E
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type ChunkSize = Maybe Int64
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{- Gets a remote's configured chunk size. -}
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chunkSize :: Maybe RemoteConfig -> ChunkSize
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chunkSize Nothing = Nothing
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chunkSize (Just m) =
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case M.lookup "chunksize" m of
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Nothing -> Nothing
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Just v -> case readSize dataUnits v of
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Nothing -> error "bad chunksize"
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Just size
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| size <= 0 -> error "bad chunksize"
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| otherwise -> Just $ fromInteger size
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{- This is an extension that's added to the usual file (or whatever)
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- where the remote stores a key. -}
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type ChunkExt = String
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{- A record of the number of chunks used.
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-
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- While this can be guessed at based on the size of the key, encryption
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- makes that larger. Also, using this helps deal with changes to chunksize
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- over the life of a remote.
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-}
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chunkCount :: ChunkExt
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chunkCount = ".chunkcount"
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{- Parses the String from the chunkCount file, and returns the files that
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- are used to store the chunks. -}
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getChunks :: FilePath -> String -> [FilePath]
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getChunks basedest chunkcount = take count $ map (basedest ++) chunkStream
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where
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count = fromMaybe 0 $ readish chunkcount
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{- An infinite stream of extensions to use for chunks. -}
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chunkStream :: [ChunkExt]
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chunkStream = map (\n -> ".chunk" ++ show n) [1 :: Integer ..]
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{- Given the base destination to use to store a value,
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- generates a stream of temporary destinations (just one when not chunking)
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- and passes it to an action, which should chunk and store the data,
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- and return the destinations it stored to, or [] on error.
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-
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- Then calles the finalizer to rename the temporary destinations into
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- their final places (and do any other cleanup), and writes the chunk count
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- (if chunking)
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-}
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storeChunks :: FilePath -> ChunkSize -> ([FilePath] -> IO [FilePath]) -> (FilePath -> String -> IO ()) -> (FilePath -> FilePath -> IO ()) -> IO Bool
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storeChunks basedest chunksize storer recorder finalizer =
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either (const $ return False) return
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=<< (E.try go :: IO (Either E.SomeException Bool))
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where
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go = do
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stored <- storer tmpdests
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forM_ stored $ \d -> do
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let dest = detmpprefix d
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finalizer d dest
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when (chunksize /= Nothing) $ do
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let chunkcount = basedest ++ chunkCount
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recorder chunkcount (show $ length stored)
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return (not $ null stored)
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tmpprefix = ".tmp"
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detmpprefix f = take (length f - tmpprefixlen) f
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tmpprefixlen = length tmpprefix
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tmpdests
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| chunksize == Nothing = [basedest ++ tmpprefix]
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| otherwise = map (++ tmpprefix) $ map (basedest ++) chunkStream
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{- Given a list of destinations to use, chunks the data according to the
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- ChunkSize, and runs the storer action to store each chunk. Returns
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- the destinations where data was stored, or [] on error.
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-
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- This buffers each chunk in memory.
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- More optimal versions of this can be written, that rely
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- on L.toChunks to split the lazy bytestring into chunks (typically
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- smaller than the ChunkSize), and eg, write those chunks to a Handle.
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- But this is the best that can be done with the storer interface that
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- writes a whole L.ByteString at a time.
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-}
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storeChunked :: ChunkSize -> [FilePath] -> (FilePath -> L.ByteString -> IO ()) -> L.ByteString -> IO [FilePath]
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storeChunked chunksize dests storer content =
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either (const $ return []) return
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=<< (E.try (go chunksize dests) :: IO (Either E.SomeException [FilePath]))
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where
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go _ [] = return [] -- no dests!?
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go Nothing (d:_) = do
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storer d content
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return [d]
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go (Just sz) _
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-- always write a chunk, even if the data is 0 bytes
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| L.null content = go Nothing dests
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| otherwise = storechunks sz [] dests content
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storechunks _ _ [] _ = return [] -- ran out of dests
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storechunks sz useddests (d:ds) b
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| L.null b = return $ reverse useddests
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| otherwise = do
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let (chunk, b') = L.splitAt sz b
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storer d chunk
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storechunks sz (d:useddests) ds b'
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