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module Storage.Internal where
import Codec.Compression.Zlib
import Control.Concurrent
import Control.Exception
import Control.Monad
import Control.Monad.Identity
import Crypto.Hash
import Data.ByteArray (ByteArrayAccess, ScrubbedBytes)
import qualified Data.ByteArray as BA
import Data.ByteString (ByteString)
import qualified Data.ByteString as B
import qualified Data.ByteString.Char8 as BC
import qualified Data.ByteString.Lazy as BL
import Data.List
import Data.Map (Map)
import qualified Data.Map as M
import System.Directory
import System.FilePath
import System.IO
import System.IO.Error
import System.Posix.Files
import System.Posix.IO
import System.Posix.Types
data Storage' c = Storage
{ stBacking :: StorageBacking c
, stParent :: Maybe (Storage' Identity)
}
deriving (Eq)
instance Show (Storage' c) where
show st@(Storage { stBacking = StorageDir path }) = "dir" ++ showParentStorage st ++ ":" ++ path
show st@(Storage { stBacking = StorageMemory {} }) = "mem" ++ showParentStorage st
showParentStorage :: Storage' c -> String
showParentStorage Storage { stParent = Nothing } = ""
showParentStorage Storage { stParent = Just st } = "@" ++ show st
data StorageBacking c
= StorageDir FilePath
| StorageMemory { memHeads :: MVar [Head' c]
, memObjs :: MVar (Map RefDigest BL.ByteString)
, memKeys :: MVar (Map RefDigest ScrubbedBytes)
}
deriving (Eq)
type RefDigest = Digest Blake2b_256
data Ref' c = Ref (Storage' c) RefDigest
deriving (Eq)
instance Show (Ref' c) where
show ref@(Ref st _) = show st ++ ":" ++ BC.unpack (showRef ref)
instance ByteArrayAccess (Ref' c) where
length (Ref _ dgst) = BA.length dgst
withByteArray (Ref _ dgst) = BA.withByteArray dgst
refDigest :: Ref' c -> RefDigest
refDigest (Ref _ dgst) = dgst
showRef :: Ref' c -> ByteString
showRef = showRefDigest . refDigest
showRefDigest :: RefDigest -> ByteString
showRefDigest = B.concat . map showHexByte . BA.unpack
where showHex x | x < 10 = x + 48
| otherwise = x + 87
showHexByte x = B.pack [ showHex (x `div` 16), showHex (x `mod` 16) ]
data Head' c = Head String (Ref' c)
deriving (Show)
class (Traversable compl, Monad compl) => StorageCompleteness compl where
type LoadResult compl a :: *
returnLoadResult :: compl a -> LoadResult compl a
ioLoadBytes :: Ref' compl -> IO (compl BL.ByteString)
instance StorageCompleteness Identity where
type LoadResult Identity a = a
returnLoadResult = runIdentity
ioLoadBytes ref@(Ref st dgst) = maybe (error $ "Ref not found in complete storage: "++show ref) Identity
<$> ioLoadBytesFromStorage st dgst
instance StorageCompleteness Maybe where
type LoadResult Maybe a = Maybe a
returnLoadResult = id
ioLoadBytes (Ref st dgst) = ioLoadBytesFromStorage st dgst
ioLoadBytesFromStorage :: Storage' c -> RefDigest -> IO (Maybe BL.ByteString)
ioLoadBytesFromStorage st dgst = loadCurrent st >>=
\case Just bytes -> return $ Just bytes
Nothing | Just parent <- stParent st -> ioLoadBytesFromStorage parent dgst
| otherwise -> return Nothing
where loadCurrent Storage { stBacking = StorageDir spath } = handleJust (guard . isDoesNotExistError) (const $ return Nothing) $
Just . decompress <$> (BL.readFile $ refPath spath dgst)
loadCurrent Storage { stBacking = StorageMemory { memObjs = tobjs } } = M.lookup dgst <$> readMVar tobjs
refPath :: FilePath -> RefDigest -> FilePath
refPath spath dgst = intercalate "/" [spath, "objects", pref, rest]
where (pref, rest) = splitAt 2 $ BC.unpack $ showRefDigest dgst
openFdParents :: FilePath -> OpenMode -> Maybe FileMode -> OpenFileFlags -> IO Fd
openFdParents path omode fmode flags = do
createDirectoryIfMissing True (takeDirectory path)
openFd path omode fmode flags
writeFileOnce :: FilePath -> BL.ByteString -> IO ()
writeFileOnce file content = bracket
(fdToHandle =<< openFdParents locked WriteOnly (Just $ unionFileModes ownerReadMode ownerWriteMode) (defaultFileFlags { exclusive = True }))
hClose $ \h -> do
fileExist file >>= \case
True -> removeLink locked
False -> do BL.hPut h content
rename locked file
where locked = file ++ ".lock"
writeFileChecked :: FilePath -> Maybe ByteString -> ByteString -> IO (Either (Maybe ByteString) ())
writeFileChecked file prev content = bracket
(fdToHandle =<< openFdParents locked WriteOnly (Just $ unionFileModes ownerReadMode ownerWriteMode) (defaultFileFlags { exclusive = True }))
hClose $ \h -> do
(prev,) <$> fileExist file >>= \case
(Nothing, True) -> do
current <- B.readFile file
removeLink locked
return $ Left $ Just current
(Nothing, False) -> do B.hPut h content
rename locked file
return $ Right ()
(Just expected, True) -> do
current <- B.readFile file
if current == expected then do B.hPut h content
rename locked file
return $ return ()
else do removeLink locked
return $ Left $ Just current
(Just _, False) -> do
removeLink locked
return $ Left Nothing
where locked = file ++ ".lock"
|