319 lines
9.3 KiB
Haskell
319 lines
9.3 KiB
Haskell
-- |
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-- Module : HPath.IO.Errors
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-- Copyright : © 2016 Julian Ospald
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-- License : GPL-2
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--
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-- Maintainer : Julian Ospald <hasufell@posteo.de>
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-- Stability : experimental
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-- Portability : portable
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--
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-- Provides error handling.
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{-# LANGUAGE DeriveDataTypeable #-}
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{-# LANGUAGE ScopedTypeVariables #-}
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module HPath.IO.Errors where
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import Control.Applicative
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(
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(<$>)
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)
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import Control.Exception
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import Control.Monad
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(
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forM
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, when
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)
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import Data.ByteString
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(
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ByteString
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)
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import Data.Data
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(
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Data(..)
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)
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import Data.Typeable
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import Foreign.C.Error
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(
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getErrno
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, Errno
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)
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import GHC.IO.Exception
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(
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IOErrorType
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)
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import HPath
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import {-# SOURCE #-} HPath.IO
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(
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canonicalizePath
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)
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import HPath.IO.Utils
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import System.IO.Error
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(
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catchIOError
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, ioeGetErrorType
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)
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import qualified System.Posix.Directory.ByteString as PFD
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import System.Posix.Files.ByteString
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(
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fileAccess
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, getFileStatus
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)
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import qualified System.Posix.Files.ByteString as PF
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data HPathIOException = FileDoesNotExist ByteString
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| DirDoesNotExist ByteString
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| SameFile ByteString ByteString
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| DestinationInSource ByteString ByteString
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| FileDoesExist ByteString
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| DirDoesExist ByteString
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| InvalidOperation String
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| Can'tOpenDirectory ByteString
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| CopyFailed String
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deriving (Typeable, Eq, Data)
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instance Show HPathIOException where
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show (FileDoesNotExist fp) = "File does not exist:" ++ fpToString fp
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show (DirDoesNotExist fp) = "Directory does not exist: "
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++ fpToString fp
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show (SameFile fp1 fp2) = fpToString fp1
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++ " and " ++ fpToString fp2
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++ " are the same file!"
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show (DestinationInSource fp1 fp2) = fpToString fp1
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++ " is contained in "
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++ fpToString fp2
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show (FileDoesExist fp) = "File does exist: " ++ fpToString fp
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show (DirDoesExist fp) = "Directory does exist: " ++ fpToString fp
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show (InvalidOperation str) = "Invalid operation: " ++ str
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show (Can'tOpenDirectory fp) = "Can't open directory: "
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++ fpToString fp
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show (CopyFailed str) = "Copying failed: " ++ str
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instance Exception HPathIOException
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isDestinationInSource :: HPathIOException -> Bool
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isDestinationInSource (DestinationInSource _ _) = True
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isDestinationInSource _ = False
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isSameFile :: HPathIOException -> Bool
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isSameFile (SameFile _ _) = True
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isSameFile _ = False
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isFileDoesExist :: HPathIOException -> Bool
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isFileDoesExist (FileDoesExist _) = True
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isFileDoesExist _ = False
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isDirDoesExist :: HPathIOException -> Bool
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isDirDoesExist (DirDoesExist _) = True
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isDirDoesExist _ = False
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----------------------------
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--[ Path based functions ]--
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----------------------------
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throwFileDoesExist :: Path Abs -> IO ()
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throwFileDoesExist fp =
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whenM (doesFileExist fp) (throwIO . FileDoesExist
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. fromAbs $ fp)
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throwDirDoesExist :: Path Abs -> IO ()
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throwDirDoesExist fp =
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whenM (doesDirectoryExist fp) (throwIO . DirDoesExist
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. fromAbs $ fp)
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throwFileDoesNotExist :: Path Abs -> IO ()
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throwFileDoesNotExist fp =
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unlessM (doesFileExist fp) (throwIO . FileDoesNotExist
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. fromAbs $ fp)
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throwDirDoesNotExist :: Path Abs -> IO ()
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throwDirDoesNotExist fp =
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unlessM (doesDirectoryExist fp) (throwIO . DirDoesNotExist
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. fromAbs $ fp)
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-- |Uses `isSameFile` and throws `SameFile` if it returns True.
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throwSameFile :: Path Abs
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-> Path Abs
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-> IO ()
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throwSameFile fp1 fp2 =
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whenM (sameFile fp1 fp2)
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(throwIO $ SameFile (fromAbs fp1) (fromAbs fp2))
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-- |Check if the files are the same by examining device and file id.
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-- This follows symbolic links.
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sameFile :: Path Abs -> Path Abs -> IO Bool
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sameFile fp1 fp2 =
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withAbsPath fp1 $ \fp1' -> withAbsPath fp2 $ \fp2' ->
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handleIOError (\_ -> return False) $ do
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fs1 <- getFileStatus fp1'
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fs2 <- getFileStatus fp2'
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if ((PF.deviceID fs1, PF.fileID fs1) ==
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(PF.deviceID fs2, PF.fileID fs2))
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then return True
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else return False
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-- |Checks whether the destination directory is contained
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-- within the source directory by comparing the device+file ID of the
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-- source directory with all device+file IDs of the parent directories
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-- of the destination.
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throwDestinationInSource :: Path Abs -- ^ source dir
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-> Path Abs -- ^ full destination, `dirname dest`
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-- must exist
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-> IO ()
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throwDestinationInSource source dest = do
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dest' <- (\x -> maybe x (\y -> x </> y) $ basename dest)
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<$> (canonicalizePath $ dirname dest)
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dids <- forM (getAllParents dest') $ \p -> do
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fs <- PF.getSymbolicLinkStatus (fromAbs p)
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return (PF.deviceID fs, PF.fileID fs)
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sid <- fmap (\x -> (PF.deviceID x, PF.fileID x))
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$ PF.getFileStatus (fromAbs source)
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when (elem sid dids)
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(throwIO $ DestinationInSource (fromAbs dest)
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(fromAbs source))
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-- |Checks if the given file exists and is not a directory.
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-- Does not follow symlinks.
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doesFileExist :: Path Abs -> IO Bool
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doesFileExist fp =
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handleIOError (\_ -> return False) $ do
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fs <- PF.getSymbolicLinkStatus (fromAbs fp)
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return $ not . PF.isDirectory $ fs
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-- |Checks if the given file exists and is a directory.
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-- Does not follow symlinks.
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doesDirectoryExist :: Path Abs -> IO Bool
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doesDirectoryExist fp =
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handleIOError (\_ -> return False) $ do
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fs <- PF.getSymbolicLinkStatus (fromAbs fp)
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return $ PF.isDirectory fs
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-- |Checks whether a file or folder is writable.
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isWritable :: Path Abs -> IO Bool
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isWritable fp =
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handleIOError (\_ -> return False) $
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fileAccess (fromAbs fp) False True False
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-- |Checks whether the directory at the given path exists and can be
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-- opened. This invokes `openDirStream` which follows symlinks.
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canOpenDirectory :: Path Abs -> IO Bool
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canOpenDirectory fp =
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handleIOError (\_ -> return False) $ do
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bracket (PFD.openDirStream . fromAbs $ fp)
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PFD.closeDirStream
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(\_ -> return ())
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return True
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-- |Throws a `Can'tOpenDirectory` FmIOException if the directory at the given
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-- path cannot be opened.
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throwCantOpenDirectory :: Path Abs -> IO ()
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throwCantOpenDirectory fp =
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unlessM (canOpenDirectory fp)
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(throwIO . Can'tOpenDirectory . fromAbs $ fp)
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--------------------------------
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--[ Error handling functions ]--
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--------------------------------
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-- |Carries out an action, then checks if there is an IOException and
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-- a specific errno. If so, then it carries out another action, otherwise
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-- it rethrows the error.
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catchErrno :: [Errno] -- ^ errno to catch
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-> IO a -- ^ action to try, which can raise an IOException
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-> IO a -- ^ action to carry out in case of an IOException and
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-- if errno matches
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-> IO a
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catchErrno en a1 a2 =
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catchIOError a1 $ \e -> do
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errno <- getErrno
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if errno `elem` en
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then a2
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else ioError e
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-- |Execute the given action and retrow IO exceptions as a new Exception
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-- that have the given errno. If errno does not match the exception is rethrown
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-- as is.
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rethrowErrnoAs :: Exception e
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=> [Errno] -- ^ errno to catch
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-> e -- ^ rethrow as if errno matches
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-> IO a -- ^ action to try
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-> IO a
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rethrowErrnoAs en fmex action = catchErrno en action (throwIO fmex)
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-- |Like `catchIOError`, with arguments swapped.
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handleIOError :: (IOError -> IO a) -> IO a -> IO a
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handleIOError = flip catchIOError
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-- |Like `bracket`, but allows to have different clean-up
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-- actions depending on whether the in-between computation
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-- has raised an exception or not.
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bracketeer :: IO a -- ^ computation to run first
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-> (a -> IO b) -- ^ computation to run last, when
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-- no exception was raised
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-> (a -> IO b) -- ^ computation to run last,
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-- when an exception was raised
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-> (a -> IO c) -- ^ computation to run in-between
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-> IO c
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bracketeer before after afterEx thing =
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mask $ \restore -> do
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a <- before
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r <- restore (thing a) `onException` afterEx a
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_ <- after a
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return r
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reactOnError :: IO a
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-> [(IOErrorType, IO a)] -- ^ reaction on IO errors
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-> [(HPathIOException, IO a)] -- ^ reaction on FmIOException
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-> IO a
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reactOnError a ios fmios =
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a `catches` [iohandler, fmiohandler]
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where
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iohandler = Handler $
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\(ex :: IOException) ->
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foldr (\(t, a') y -> if ioeGetErrorType ex == t
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then a'
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else y)
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(throwIO ex)
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ios
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fmiohandler = Handler $
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\(ex :: HPathIOException) ->
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foldr (\(t, a') y -> if toConstr ex == toConstr t
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then a'
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else y)
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(throwIO ex)
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fmios
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