Types.hs

{-# LANGUAGE CPP, GeneralizedNewtypeDeriving, BangPatterns, DeriveTraversable #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  Codec.Archive.Tar.Types
-- Copyright   :  (c) 2007 Bjorn Bringert,
--                    2008 Andrea Vezzosi,
--                    2008-2009 Duncan Coutts
--                    2011 Max Bolingbroke
-- License     :  BSD3
--
-- Maintainer  :  duncan@community.haskell.org
-- Portability :  portable
--
-- Types to represent the content of @.tar@ archives.
--
-----------------------------------------------------------------------------
module Codec.Archive.Tar.Types (

  Entry(..),
  entryPath,
  EntryContent(..),
  FileSize,
  Permissions,
  Ownership(..),
  EpochTime,
  TypeCode,
  DevMajor,
  DevMinor,
  Format(..),

  simpleEntry,
  fileEntry,
  directoryEntry,

  ordinaryFilePermissions,
  executableFilePermissions,
  directoryPermissions,

  TarPath(..),
  toTarPath,
  fromTarPath,
  fromTarPathToPosixPath,
  fromTarPathToWindowsPath,

  LinkTarget(..),
  toLinkTarget,
  fromLinkTarget,
  fromLinkTargetToPosixPath,
  fromLinkTargetToWindowsPath,

  Entries(..),
  mapEntries,
  mapEntriesNoFail,
  foldEntries,
  foldlEntries,
  unfoldEntries,
  ) where

import Data.Int      (Int64)
import Data.Monoid   (Monoid(..))
import Data.Semigroup as Sem
import qualified Data.ByteString       as BS
import qualified Data.ByteString.Char8 as BS.Char8
import qualified Data.ByteString.Lazy  as LBS
import Control.DeepSeq

import qualified System.FilePath as FilePath.Native
         ( joinPath, splitDirectories, addTrailingPathSeparator )
import qualified System.FilePath.Posix as FilePath.Posix
         ( joinPath, splitPath, splitDirectories, hasTrailingPathSeparator
         , addTrailingPathSeparator )
import qualified System.FilePath.Windows as FilePath.Windows
         ( joinPath, addTrailingPathSeparator )
import System.Posix.Types
         ( FileMode )

type FileSize  = Int64
-- | The number of seconds since the UNIX epoch
type EpochTime = Int64
type DevMajor  = Int
type DevMinor  = Int
type TypeCode  = Char
type Permissions = FileMode

-- | Tar archive entry.
--
data Entry = Entry {

    -- | The path of the file or directory within the archive. This is in a
    -- tar-specific form. Use 'entryPath' to get a native 'FilePath'.
    entryTarPath :: {-# UNPACK #-} !TarPath,

    -- | The real content of the entry. For 'NormalFile' this includes the
    -- file data. An entry usually contains a 'NormalFile' or a 'Directory'.
    entryContent :: !EntryContent,

    -- | File permissions (Unix style file mode).
    entryPermissions :: {-# UNPACK #-} !Permissions,

    -- | The user and group to which this file belongs.
    entryOwnership :: {-# UNPACK #-} !Ownership,

    -- | The time the file was last modified.
    entryTime :: {-# UNPACK #-} !EpochTime,

    -- | The tar format the archive is using.
    entryFormat :: !Format
  }
  deriving (Eq, Show)

-- | Native 'FilePath' of the file or directory within the archive.
--
entryPath :: Entry -> FilePath
entryPath = fromTarPath . entryTarPath

-- | The content of a tar archive entry, which depends on the type of entry.
--
-- Portable archives should contain only 'NormalFile' and 'Directory'.
--
data EntryContent = NormalFile      LBS.ByteString {-# UNPACK #-} !FileSize
                  | Directory
                  | SymbolicLink    !LinkTarget
                  | HardLink        !LinkTarget
                  | CharacterDevice {-# UNPACK #-} !DevMajor
                                    {-# UNPACK #-} !DevMinor
                  | BlockDevice     {-# UNPACK #-} !DevMajor
                                    {-# UNPACK #-} !DevMinor
                  | NamedPipe
                  | OtherEntryType  {-# UNPACK #-} !TypeCode LBS.ByteString
                                    {-# UNPACK #-} !FileSize
    deriving (Eq, Ord, Show)

data Ownership = Ownership {
    -- | The owner user name. Should be set to @\"\"@ if unknown.
    ownerName :: String,

    -- | The owner group name. Should be set to @\"\"@ if unknown.
    groupName :: String,

    -- | Numeric owner user id. Should be set to @0@ if unknown.
    ownerId :: {-# UNPACK #-} !Int,

    -- | Numeric owner group id. Should be set to @0@ if unknown.
    groupId :: {-# UNPACK #-} !Int
  }
    deriving (Eq, Ord, Show)

-- | There have been a number of extensions to the tar file format over the
-- years. They all share the basic entry fields and put more meta-data in
-- different extended headers.
--
data Format =

     -- | This is the classic Unix V7 tar format. It does not support owner and
     -- group names, just numeric Ids. It also does not support device numbers.
     V7Format

     -- | The \"USTAR\" format is an extension of the classic V7 format. It was
     -- later standardised by POSIX. It has some restrictions but is the most
     -- portable format.
     --
   | UstarFormat

     -- | The GNU tar implementation also extends the classic V7 format, though
     -- in a slightly different way from the USTAR format. In general for new
     -- archives the standard USTAR/POSIX should be used.
     --
   | GnuFormat
  deriving (Eq, Ord, Show)

instance NFData Entry where
  rnf (Entry _ c _ _ _ _) = rnf c

instance NFData EntryContent where
  rnf x = case x of
      NormalFile       c _  -> rnf c
      OtherEntryType _ c _  -> rnf c
      _                     -> seq x ()

instance NFData Ownership where
  rnf (Ownership o g _ _) = rnf o `seq` rnf g

-- | @rw-r--r--@ for normal files
ordinaryFilePermissions :: Permissions
ordinaryFilePermissions   = 0o0644

-- | @rwxr-xr-x@ for executable files
executableFilePermissions :: Permissions
executableFilePermissions = 0o0755

-- | @rwxr-xr-x@ for directories
directoryPermissions :: Permissions
directoryPermissions  = 0o0755

-- | An 'Entry' with all default values except for the file name and type. It
-- uses the portable USTAR/POSIX format (see 'UstarHeader').
--
-- You can use this as a basis and override specific fields, eg:
--
-- > (emptyEntry name HardLink) { linkTarget = target }
--
simpleEntry :: TarPath -> EntryContent -> Entry
simpleEntry tarpath content = Entry {
    entryTarPath     = tarpath,
    entryContent     = content,
    entryPermissions = case content of
                         Directory -> directoryPermissions
                         _         -> ordinaryFilePermissions,
    entryOwnership   = Ownership "" "" 0 0,
    entryTime        = 0,
    entryFormat      = UstarFormat
  }

-- | A tar 'Entry' for a file.
--
-- Entry  fields such as file permissions and ownership have default values.
--
-- You can use this as a basis and override specific fields. For example if you
-- need an executable file you could use:
--
-- > (fileEntry name content) { fileMode = executableFileMode }
--
fileEntry :: TarPath -> LBS.ByteString -> Entry
fileEntry name fileContent =
  simpleEntry name (NormalFile fileContent (LBS.length fileContent))

-- | A tar 'Entry' for a directory.
--
-- Entry fields such as file permissions and ownership have default values.
--
directoryEntry :: TarPath -> Entry
directoryEntry name = simpleEntry name Directory

--
-- * Tar paths
--

-- | The classic tar format allowed just 100 characters for the file name. The
-- USTAR format extended this with an extra 155 characters, however it uses a
-- complex method of splitting the name between the two sections.
--
-- Instead of just putting any overflow into the extended area, it uses the
-- extended area as a prefix. The aggravating insane bit however is that the
-- prefix (if any) must only contain a directory prefix. That is the split
-- between the two areas must be on a directory separator boundary. So there is
-- no simple calculation to work out if a file name is too long. Instead we
-- have to try to find a valid split that makes the name fit in the two areas.
--
-- The rationale presumably was to make it a bit more compatible with old tar
-- programs that only understand the classic format. A classic tar would be
-- able to extract the file name and possibly some dir prefix, but not the
-- full dir prefix. So the files would end up in the wrong place, but that's
-- probably better than ending up with the wrong names too.
--
-- So it's understandable but rather annoying.
--
-- * Tar paths use Posix format (ie @\'/\'@ directory separators), irrespective
--   of the local path conventions.
--
-- * The directory separator between the prefix and name is /not/ stored.
--
data TarPath = TarPath {-# UNPACK #-} !BS.ByteString -- path name, 100 characters max.
                       {-# UNPACK #-} !BS.ByteString -- path prefix, 155 characters max.
  deriving (Eq, Ord)

instance NFData TarPath where
  rnf (TarPath _ _) = () -- fully strict by construction

instance Show TarPath where
  show = show . fromTarPath

-- | Convert a 'TarPath' to a native 'FilePath'.
--
-- The native 'FilePath' will use the native directory separator but it is not
-- otherwise checked for validity or sanity. In particular:
--
-- * The tar path may be invalid as a native path, eg the file name @\"nul\"@
--   is not valid on Windows.
--
-- * The tar path may be an absolute path or may contain @\"..\"@ components.
--   For security reasons this should not usually be allowed, but it is your
--   responsibility to check for these conditions (eg using 'checkSecurity').
--
fromTarPath :: TarPath -> FilePath
fromTarPath (TarPath namebs prefixbs) = adjustDirectory $
  FilePath.Native.joinPath $ FilePath.Posix.splitDirectories prefix
                          ++ FilePath.Posix.splitDirectories name
  where
    name   = BS.Char8.unpack namebs
    prefix = BS.Char8.unpack prefixbs
    adjustDirectory | FilePath.Posix.hasTrailingPathSeparator name
                    = FilePath.Native.addTrailingPathSeparator
                    | otherwise = id

-- | Convert a 'TarPath' to a Unix\/Posix 'FilePath'.
--
-- The difference compared to 'fromTarPath' is that it always returns a Unix
-- style path irrespective of the current operating system.
--
-- This is useful to check how a 'TarPath' would be interpreted on a specific
-- operating system, eg to perform portability checks.
--
fromTarPathToPosixPath :: TarPath -> FilePath
fromTarPathToPosixPath (TarPath namebs prefixbs) = adjustDirectory $
  FilePath.Posix.joinPath $ FilePath.Posix.splitDirectories prefix
                         ++ FilePath.Posix.splitDirectories name
  where
    name   = BS.Char8.unpack namebs
    prefix = BS.Char8.unpack prefixbs
    adjustDirectory | FilePath.Posix.hasTrailingPathSeparator name
                    = FilePath.Posix.addTrailingPathSeparator
                    | otherwise = id

-- | Convert a 'TarPath' to a Windows 'FilePath'.
--
-- The only difference compared to 'fromTarPath' is that it always returns a
-- Windows style path irrespective of the current operating system.
--
-- This is useful to check how a 'TarPath' would be interpreted on a specific
-- operating system, eg to perform portability checks.
--
fromTarPathToWindowsPath :: TarPath -> FilePath
fromTarPathToWindowsPath (TarPath namebs prefixbs) = adjustDirectory $
  FilePath.Windows.joinPath $ FilePath.Posix.splitDirectories prefix
                           ++ FilePath.Posix.splitDirectories name
  where
    name   = BS.Char8.unpack namebs
    prefix = BS.Char8.unpack prefixbs
    adjustDirectory | FilePath.Posix.hasTrailingPathSeparator name
                    = FilePath.Windows.addTrailingPathSeparator
                    | otherwise = id

-- | Convert a native 'FilePath' to a 'TarPath'.
--
-- The conversion may fail if the 'FilePath' is too long. See 'TarPath' for a
-- description of the problem with splitting long 'FilePath's.
--
toTarPath :: Bool -- ^ Is the path for a directory? This is needed because for
                  -- directories a 'TarPath' must always use a trailing @\/@.
          -> FilePath -> Either String TarPath
toTarPath isDir = splitLongPath
                . addTrailingSep
                . FilePath.Posix.joinPath
                . FilePath.Native.splitDirectories
  where
    addTrailingSep | isDir     = FilePath.Posix.addTrailingPathSeparator
                   | otherwise = id

-- | Take a sanitised path, split on directory separators and try to pack it
-- into the 155 + 100 tar file name format.
--
-- The strategy is this: take the name-directory components in reverse order
-- and try to fit as many components into the 100 long name area as possible.
-- If all the remaining components fit in the 155 name area then we win.
--
splitLongPath :: FilePath -> Either String TarPath
splitLongPath path =
  case packName nameMax (reverse (FilePath.Posix.splitPath path)) of
    Left err                 -> Left err
    Right (name, [])         -> Right $! TarPath (BS.Char8.pack name)
                                                  BS.empty
    Right (name, first:rest) -> case packName prefixMax remainder of
      Left err               -> Left err
      Right (_     , (_:_))  -> Left "File name too long (cannot split)"
      Right (prefix, [])     -> Right $! TarPath (BS.Char8.pack name)
                                                 (BS.Char8.pack prefix)
      where
        -- drop the '/' between the name and prefix:
        remainder = init first : rest

  where
    nameMax, prefixMax :: Int
    nameMax   = 100
    prefixMax = 155

    packName _      []     = Left "File name empty"
    packName maxLen (c:cs)
      | n > maxLen         = Left "File name too long"
      | otherwise          = Right (packName' maxLen n [c] cs)
      where n = length c

    packName' maxLen n ok (c:cs)
      | n' <= maxLen             = packName' maxLen n' (c:ok) cs
                                     where n' = n + length c
    packName' _      _ ok    cs  = (FilePath.Posix.joinPath ok, cs)

-- | The tar format allows just 100 ASCII characters for the 'SymbolicLink' and
-- 'HardLink' entry types.
--
newtype LinkTarget = LinkTarget BS.ByteString
  deriving (Eq, Ord, Show)

instance NFData LinkTarget where
    rnf (LinkTarget bs) = rnf bs

-- | Convert a native 'FilePath' to a tar 'LinkTarget'. This may fail if the
-- string is longer than 100 characters or if it contains non-portable
-- characters.
--
toLinkTarget   :: FilePath -> Maybe LinkTarget
toLinkTarget path | length path <= 100 = Just $! LinkTarget (BS.Char8.pack path)
                  | otherwise          = Nothing

-- | Convert a tar 'LinkTarget' to a native 'FilePath'.
--
fromLinkTarget :: LinkTarget -> FilePath
fromLinkTarget (LinkTarget pathbs) = adjustDirectory $
  FilePath.Native.joinPath $ FilePath.Posix.splitDirectories path
  where
    path = BS.Char8.unpack pathbs
    adjustDirectory | FilePath.Posix.hasTrailingPathSeparator path
                    = FilePath.Native.addTrailingPathSeparator
                    | otherwise = id

-- | Convert a tar 'LinkTarget' to a Unix/Posix 'FilePath'.
--
fromLinkTargetToPosixPath :: LinkTarget -> FilePath
fromLinkTargetToPosixPath (LinkTarget pathbs) = adjustDirectory $
  FilePath.Posix.joinPath $ FilePath.Posix.splitDirectories path
  where
    path = BS.Char8.unpack pathbs
    adjustDirectory | FilePath.Posix.hasTrailingPathSeparator path
                    = FilePath.Native.addTrailingPathSeparator
                    | otherwise = id

-- | Convert a tar 'LinkTarget' to a Windows 'FilePath'.
--
fromLinkTargetToWindowsPath :: LinkTarget -> FilePath
fromLinkTargetToWindowsPath (LinkTarget pathbs) = adjustDirectory $
  FilePath.Windows.joinPath $ FilePath.Posix.splitDirectories path
  where
    path = BS.Char8.unpack pathbs
    adjustDirectory | FilePath.Posix.hasTrailingPathSeparator path
                    = FilePath.Windows.addTrailingPathSeparator
                    | otherwise = id

--
-- * Entries type
--

-- | A tar archive is a sequence of entries.
--
-- The point of this type as opposed to just using a list is that it makes the
-- failure case explicit. We need this because the sequence of entries we get
-- from reading a tarball can include errors.
--
-- It is a concrete data type so you can manipulate it directly but it is often
-- clearer to use the provided functions for mapping, folding and unfolding.
--
-- Converting from a list can be done with just @foldr Next Done@. Converting
-- back into a list can be done with 'foldEntries' however in that case you
-- must be prepared to handle the 'Fail' case inherent in the 'Entries' type.
--
-- The 'Monoid' instance lets you concatenate archives or append entries to an
-- archive.
--
data Entries e = Next Entry (Entries e)
               | Done
               | Fail e
  deriving (Eq, Show, Functor, Foldable, Traversable)

infixr 5 `Next`

-- | This is like the standard 'unfoldr' function on lists, but for 'Entries'.
-- It includes failure as an extra possibility that the stepper function may
-- return.
--
-- It can be used to generate 'Entries' from some other type. For example it is
-- used internally to lazily unfold entries from a 'LBS.ByteString'.
--
unfoldEntries :: (a -> Either e (Maybe (Entry, a))) -> a -> Entries e
unfoldEntries f = unfold
  where
    unfold x = case f x of
      Left err             -> Fail err
      Right Nothing        -> Done
      Right (Just (e, x')) -> Next e (unfold x')

-- | This is like the standard 'foldr' function on lists, but for 'Entries'.
-- Compared to 'foldr' it takes an extra function to account for the
-- possibility of failure.
--
-- This is used to consume a sequence of entries. For example it could be used
-- to scan a tarball for problems or to collect an index of the contents.
--
foldEntries :: (Entry -> a -> a) -> a -> (e -> a) -> Entries e -> a
foldEntries next done fail' = fold
  where
    fold (Next e es) = next e (fold es)
    fold Done        = done
    fold (Fail err)  = fail' err

-- | A 'foldl'-like function on Entries. It either returns the final
-- accumulator result, or the failure along with the intermediate accumulator
-- value.
--
foldlEntries :: (a -> Entry -> a) -> a -> Entries e -> Either (e, a) a
foldlEntries f z = go z
  where
    go !acc (Next e es) = go (f acc e) es
    go !acc  Done       = Right acc
    go !acc (Fail err)  = Left (err, acc)

-- | This is like the standard 'map' function on lists, but for 'Entries'. It
-- includes failure as a extra possible outcome of the mapping function.
--
-- If your mapping function cannot fail it may be more convenient to use
-- 'mapEntriesNoFail'
mapEntries :: (Entry -> Either e' Entry) -> Entries e -> Entries (Either e e')
mapEntries f =
  foldEntries (\entry rest -> either (Fail . Right) (flip Next rest) (f entry)) Done (Fail . Left)

-- | Like 'mapEntries' but the mapping function itself cannot fail.
--
mapEntriesNoFail :: (Entry -> Entry) -> Entries e -> Entries e
mapEntriesNoFail f =
  foldEntries (\entry -> Next (f entry)) Done Fail

-- | @since 0.5.1.0
instance Sem.Semigroup (Entries e) where
  a <> b = foldEntries Next b Fail a

instance Monoid (Entries e) where
  mempty  = Done
  mappend = (Sem.<>)

instance NFData e => NFData (Entries e) where
  rnf (Next e es) = rnf e `seq` rnf es
  rnf  Done       = ()
  rnf (Fail e)    = rnf e