dist-install/build/System/Posix/Files/Common.hs

    {-# LINE 1 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    {-# LANGUAGE Trustworthy #-}
    {-# LINE 2 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  System.Posix.Files.Common
    -- Copyright   :  (c) The University of Glasgow 2002
    -- License     :  BSD-style (see the file libraries/base/LICENSE)
    --
    -- Maintainer  :  libraries@haskell.org
    -- Stability   :  provisional
    -- Portability :  non-portable (requires POSIX)
    --
    -- Functions defined by the POSIX standards for manipulating and querying the
    -- file system. Names of underlying POSIX functions are indicated whenever
    -- possible. A more complete documentation of the POSIX functions together
    -- with a more detailed description of different error conditions are usually
    -- available in the system's manual pages or from
    -- <http://www.unix.org/version3/online.html> (free registration required).
    --
    -- When a function that calls an underlying POSIX function fails, the errno
    -- code is converted to an 'IOError' using 'Foreign.C.Error.errnoToIOError'.
    -- For a list of which errno codes may be generated, consult the POSIX
    -- documentation for the underlying function.
    --
    -----------------------------------------------------------------------------

    {-# LINE 28 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    module System.Posix.Files.Common (
        -- * File modes
        -- FileMode exported by System.Posix.Types
        unionFileModes, intersectFileModes,
        nullFileMode,
        ownerReadMode, ownerWriteMode, ownerExecuteMode, ownerModes,
        groupReadMode, groupWriteMode, groupExecuteMode, groupModes,
        otherReadMode, otherWriteMode, otherExecuteMode, otherModes,
        setUserIDMode, setGroupIDMode,
        stdFileMode,   accessModes,
        fileTypeModes,
        blockSpecialMode, characterSpecialMode, namedPipeMode, regularFileMode,
        directoryMode, symbolicLinkMode, socketMode,

        -- ** Setting file modes
        setFdMode, setFileCreationMask,

        -- * File status
        FileStatus(..),
        -- ** Obtaining file status
        getFdStatus,
        -- ** Querying file status
        deviceID, fileID, fileMode, linkCount, fileOwner, fileGroup,
        specialDeviceID, fileSize, accessTime, modificationTime,
        statusChangeTime,
        accessTimeHiRes, modificationTimeHiRes, statusChangeTimeHiRes,
        setFdTimesHiRes, touchFd,
        isBlockDevice, isCharacterDevice, isNamedPipe, isRegularFile,
        isDirectory, isSymbolicLink, isSocket,

        -- * Setting file sizes
        setFdSize,

        -- * Changing file ownership
        setFdOwnerAndGroup,

        -- * Find system-specific limits for a file
        PathVar(..), getFdPathVar, pathVarConst,

        -- * Low level types and functions

    {-# LINE 70 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        CTimeSpec(..),
        toCTimeSpec,
        c_utimensat,

    {-# LINE 74 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        CTimeVal(..),
        toCTimeVal,
        c_utimes,

    {-# LINE 78 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        c_lutimes,

    {-# LINE 80 "libraries/unix/System/Posix/Files/Common.hsc" #-}
      ) where

    import System.Posix.Types
    import System.IO.Unsafe
    import Data.Bits
    import Data.Int
    import Data.Ratio
    import Data.Time.Clock.POSIX (POSIXTime)
    import System.Posix.Internals
    import Foreign.C
    import Foreign.ForeignPtr

    {-# LINE 92 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    import Foreign.Marshal (withArray)

    {-# LINE 94 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    import Foreign.Ptr
    import Foreign.Storable

    -- -----------------------------------------------------------------------------
    -- POSIX file modes

    -- The abstract type 'FileMode', constants and operators for
    -- manipulating the file modes defined by POSIX.

    -- | No permissions.
    nullFileMode :: FileMode
    nullFileMode = 0

    -- | Owner has read permission.
    ownerReadMode :: FileMode
    ownerReadMode = (256)
    {-# LINE 110 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Owner has write permission.
    ownerWriteMode :: FileMode
    ownerWriteMode = (128)
    {-# LINE 114 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Owner has execute permission.
    ownerExecuteMode :: FileMode
    ownerExecuteMode = (64)
    {-# LINE 118 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Group has read permission.
    groupReadMode :: FileMode
    groupReadMode = (32)
    {-# LINE 122 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Group has write permission.
    groupWriteMode :: FileMode
    groupWriteMode = (16)
    {-# LINE 126 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Group has execute permission.
    groupExecuteMode :: FileMode
    groupExecuteMode = (8)
    {-# LINE 130 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Others have read permission.
    otherReadMode :: FileMode
    otherReadMode = (4)
    {-# LINE 134 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Others have write permission.
    otherWriteMode :: FileMode
    otherWriteMode = (2)
    {-# LINE 138 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Others have execute permission.
    otherExecuteMode :: FileMode
    otherExecuteMode = (1)
    {-# LINE 142 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Set user ID on execution.
    setUserIDMode :: FileMode
    setUserIDMode = (2048)
    {-# LINE 146 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Set group ID on execution.
    setGroupIDMode :: FileMode
    setGroupIDMode = (1024)
    {-# LINE 150 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Owner, group and others have read and write permission.
    stdFileMode :: FileMode
    stdFileMode = ownerReadMode  .|. ownerWriteMode .|.
                  groupReadMode  .|. groupWriteMode .|.
                  otherReadMode  .|. otherWriteMode

    -- | Owner has read, write and execute permission.
    ownerModes :: FileMode
    ownerModes = (448)
    {-# LINE 160 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Group has read, write and execute permission.
    groupModes :: FileMode
    groupModes = (56)
    {-# LINE 164 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Others have read, write and execute permission.
    otherModes :: FileMode
    otherModes = (7)
    {-# LINE 168 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Owner, group and others have read, write and execute permission.
    accessModes :: FileMode
    accessModes = ownerModes .|. groupModes .|. otherModes

    -- | Combines the two file modes into one that contains modes that appear in
    -- either.
    unionFileModes :: FileMode -> FileMode -> FileMode
    unionFileModes m1 m2 = m1 .|. m2

    -- | Combines two file modes into one that only contains modes that appear in
    -- both.
    intersectFileModes :: FileMode -> FileMode -> FileMode
    intersectFileModes m1 m2 = m1 .&. m2

    fileTypeModes :: FileMode
    fileTypeModes = (61440)
    {-# LINE 185 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    blockSpecialMode :: FileMode
    blockSpecialMode = (24576)
    {-# LINE 188 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    characterSpecialMode :: FileMode
    characterSpecialMode = (8192)
    {-# LINE 191 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    namedPipeMode :: FileMode
    namedPipeMode = (4096)
    {-# LINE 194 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    regularFileMode :: FileMode
    regularFileMode = (32768)
    {-# LINE 197 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    directoryMode :: FileMode
    directoryMode = (16384)
    {-# LINE 200 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    symbolicLinkMode :: FileMode
    symbolicLinkMode = (40960)
    {-# LINE 203 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    socketMode :: FileMode
    socketMode = (49152)
    {-# LINE 206 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | @setFdMode fd mode@ acts like 'setFileMode' but uses a file descriptor
    -- @fd@ instead of a 'FilePath'.
    --
    -- Note: calls @fchmod@.
    setFdMode :: Fd -> FileMode -> IO ()
    setFdMode (Fd fd) m =
      throwErrnoIfMinus1_ "setFdMode" (c_fchmod fd m)

    foreign import ccall unsafe "fchmod"
      c_fchmod :: CInt -> CMode -> IO CInt

    -- | @setFileCreationMask mode@ sets the file mode creation mask to @mode@.
    -- Modes set by this operation are subtracted from files and directories upon
    -- creation. The previous file creation mask is returned.
    --
    -- Note: calls @umask@.
    setFileCreationMask :: FileMode -> IO FileMode
    setFileCreationMask mask = c_umask mask

    -- -----------------------------------------------------------------------------
    -- stat() support

    -- | POSIX defines operations to get information, such as owner, permissions,
    -- size and access times, about a file. This information is represented by the
    -- 'FileStatus' type.
    --
    -- Note: see @chmod@.
    newtype FileStatus = FileStatus (ForeignPtr CStat)

    -- | ID of the device on which this file resides.
    deviceID         :: FileStatus -> DeviceID
    -- | inode number
    fileID           :: FileStatus -> FileID
    -- | File mode (such as permissions).
    fileMode         :: FileStatus -> FileMode
    -- | Number of hard links to this file.
    linkCount        :: FileStatus -> LinkCount
    -- | ID of owner.
    fileOwner        :: FileStatus -> UserID
    -- | ID of group.
    fileGroup        :: FileStatus -> GroupID
    -- | Describes the device that this file represents.
    specialDeviceID  :: FileStatus -> DeviceID
    -- | Size of the file in bytes. If this file is a symbolic link the size is
    -- the length of the pathname it contains.
    fileSize         :: FileStatus -> FileOffset
    -- | Time of last access.
    accessTime       :: FileStatus -> EpochTime
    -- | Time of last access in sub-second resolution.
    accessTimeHiRes  :: FileStatus -> POSIXTime
    -- | Time of last modification.
    modificationTime :: FileStatus -> EpochTime
    -- | Time of last modification in sub-second resolution.
    modificationTimeHiRes :: FileStatus -> POSIXTime
    -- | Time of last status change (i.e. owner, group, link count, mode, etc.).
    statusChangeTime :: FileStatus -> EpochTime
    -- | Time of last status change (i.e. owner, group, link count, mode, etc.) in sub-second resolution.
    statusChangeTimeHiRes :: FileStatus -> POSIXTime

    deviceID (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ ((\hsc_ptr -> peekByteOff hsc_ptr 0))
    {-# LINE 268 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    fileID (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ ((\hsc_ptr -> peekByteOff hsc_ptr 8))
    {-# LINE 270 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    fileMode (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ ((\hsc_ptr -> peekByteOff hsc_ptr 24))
    {-# LINE 272 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    linkCount (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ ((\hsc_ptr -> peekByteOff hsc_ptr 16))
    {-# LINE 274 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    fileOwner (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ ((\hsc_ptr -> peekByteOff hsc_ptr 28))
    {-# LINE 276 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    fileGroup (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ ((\hsc_ptr -> peekByteOff hsc_ptr 32))
    {-# LINE 278 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    specialDeviceID (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ ((\hsc_ptr -> peekByteOff hsc_ptr 40))
    {-# LINE 280 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    fileSize (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ ((\hsc_ptr -> peekByteOff hsc_ptr 48))
    {-# LINE 282 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    accessTime (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ ((\hsc_ptr -> peekByteOff hsc_ptr 72))
    {-# LINE 284 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    modificationTime (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ ((\hsc_ptr -> peekByteOff hsc_ptr 88))
    {-# LINE 286 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    statusChangeTime (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ ((\hsc_ptr -> peekByteOff hsc_ptr 104))
    {-# LINE 288 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    accessTimeHiRes (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ \stat_ptr -> do
        sec  <- ((\hsc_ptr -> peekByteOff hsc_ptr 72)) stat_ptr :: IO EpochTime
    {-# LINE 292 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 293 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        nsec <- ((\hsc_ptr -> peekByteOff hsc_ptr 80)) stat_ptr :: IO (Int64)
    {-# LINE 294 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        let frac = toInteger nsec % 10^(9::Int)

    {-# LINE 310 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        return $ fromRational $ toRational sec + frac

    modificationTimeHiRes (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ \stat_ptr -> do
        sec  <- ((\hsc_ptr -> peekByteOff hsc_ptr 88)) stat_ptr :: IO EpochTime
    {-# LINE 315 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 316 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        nsec <- ((\hsc_ptr -> peekByteOff hsc_ptr 96)) stat_ptr :: IO (Int64)
    {-# LINE 317 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        let frac = toInteger nsec % 10^(9::Int)

    {-# LINE 333 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        return $ fromRational $ toRational sec + frac

    statusChangeTimeHiRes (FileStatus stat) =
      unsafePerformIO $ withForeignPtr stat $ \stat_ptr -> do
        sec  <- ((\hsc_ptr -> peekByteOff hsc_ptr 104)) stat_ptr :: IO EpochTime
    {-# LINE 338 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 339 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        nsec <- ((\hsc_ptr -> peekByteOff hsc_ptr 112)) stat_ptr :: IO (Int64)
    {-# LINE 340 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        let frac = toInteger nsec % 10^(9::Int)

    {-# LINE 356 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        return $ fromRational $ toRational sec + frac

    -- | Checks if this file is a block device.
    isBlockDevice     :: FileStatus -> Bool
    -- | Checks if this file is a character device.
    isCharacterDevice :: FileStatus -> Bool
    -- | Checks if this file is a named pipe device.
    isNamedPipe       :: FileStatus -> Bool
    -- | Checks if this file is a regular file device.
    isRegularFile     :: FileStatus -> Bool
    -- | Checks if this file is a directory device.
    isDirectory       :: FileStatus -> Bool
    -- | Checks if this file is a symbolic link device.
    isSymbolicLink    :: FileStatus -> Bool
    -- | Checks if this file is a socket device.
    isSocket          :: FileStatus -> Bool

    isBlockDevice stat =
      (fileMode stat `intersectFileModes` fileTypeModes) == blockSpecialMode
    isCharacterDevice stat =
      (fileMode stat `intersectFileModes` fileTypeModes) == characterSpecialMode
    isNamedPipe stat =
      (fileMode stat `intersectFileModes` fileTypeModes) == namedPipeMode
    isRegularFile stat =
      (fileMode stat `intersectFileModes` fileTypeModes) == regularFileMode
    isDirectory stat =
      (fileMode stat `intersectFileModes` fileTypeModes) == directoryMode
    isSymbolicLink stat =
      (fileMode stat `intersectFileModes` fileTypeModes) == symbolicLinkMode
    isSocket stat =
      (fileMode stat `intersectFileModes` fileTypeModes) == socketMode

    -- | @getFdStatus fd@ acts as 'getFileStatus' but uses a file descriptor @fd@.
    --
    -- Note: calls @fstat@.
    getFdStatus :: Fd -> IO FileStatus
    getFdStatus (Fd fd) = do
      fp <- mallocForeignPtrBytes (144)
    {-# LINE 394 "libraries/unix/System/Posix/Files/Common.hsc" #-}
      withForeignPtr fp $ \p ->
        throwErrnoIfMinus1_ "getFdStatus" (c_fstat fd p)
      return (FileStatus fp)

    -- -----------------------------------------------------------------------------
    -- Setting file times

    {-# LINE 402 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    data CTimeSpec = CTimeSpec EpochTime CLong

    instance Storable CTimeSpec where
        sizeOf    _ = (16)
    {-# LINE 406 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        alignment _ = alignment (undefined :: CInt)
        poke p (CTimeSpec sec nsec) = do
            ((\hsc_ptr -> pokeByteOff hsc_ptr 0)) p sec
    {-# LINE 409 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            ((\hsc_ptr -> pokeByteOff hsc_ptr 8)) p nsec
    {-# LINE 410 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        peek p = do
            sec  <- (\hsc_ptr -> peekByteOff hsc_ptr 0) p
    {-# LINE 412 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            nsec <- (\hsc_ptr -> peekByteOff hsc_ptr 8) p
    {-# LINE 413 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            return $ CTimeSpec sec nsec

    toCTimeSpec :: POSIXTime -> CTimeSpec
    toCTimeSpec t = CTimeSpec (CTime sec) (truncate $ 10^(9::Int) * frac)
      where
        (sec, frac) = if (frac' < 0) then (sec' - 1, frac' + 1) else (sec', frac')
        (sec', frac') = properFraction $ toRational t

    {-# LINE 421 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 423 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    foreign import ccall unsafe "utimensat"
        c_utimensat :: CInt -> CString -> Ptr CTimeSpec -> CInt -> IO CInt

    {-# LINE 426 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 428 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    foreign import ccall unsafe "futimens"
        c_futimens :: CInt -> Ptr CTimeSpec -> IO CInt

    {-# LINE 431 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    data CTimeVal = CTimeVal CLong CLong

    instance Storable CTimeVal where
        sizeOf    _ = (16)
    {-# LINE 436 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        alignment _ = alignment (undefined :: CInt)
        poke p (CTimeVal sec usec) = do
            ((\hsc_ptr -> pokeByteOff hsc_ptr 0)) p sec
    {-# LINE 439 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            ((\hsc_ptr -> pokeByteOff hsc_ptr 8)) p usec
    {-# LINE 440 "libraries/unix/System/Posix/Files/Common.hsc" #-}
        peek p = do
            sec  <- (\hsc_ptr -> peekByteOff hsc_ptr 0) p
    {-# LINE 442 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            usec <- (\hsc_ptr -> peekByteOff hsc_ptr 8) p
    {-# LINE 443 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            return $ CTimeVal sec usec

    toCTimeVal :: POSIXTime -> CTimeVal
    toCTimeVal t = CTimeVal sec (truncate $ 10^(6::Int) * frac)
      where
        (sec, frac) = if (frac' < 0) then (sec' - 1, frac' + 1) else (sec', frac')
        (sec', frac') = properFraction $ toRational t

    foreign import ccall unsafe "utimes"
        c_utimes :: CString -> Ptr CTimeVal -> IO CInt

    {-# LINE 455 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    foreign import ccall unsafe "lutimes"
        c_lutimes :: CString -> Ptr CTimeVal -> IO CInt

    {-# LINE 458 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 460 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    foreign import ccall unsafe "futimes"
        c_futimes :: CInt -> Ptr CTimeVal -> IO CInt

    {-# LINE 463 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Like 'setFileTimesHiRes' but uses a file descriptor instead of a path.
    -- This operation is not supported on all platforms. On these platforms,
    -- this function will raise an exception.
    --
    -- Note: calls @futimens@ or @futimes@.
    --
    -- @since 2.7.0.0
    setFdTimesHiRes :: Fd -> POSIXTime -> POSIXTime -> IO ()

    {-# LINE 473 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    setFdTimesHiRes (Fd fd) atime mtime =
      withArray [toCTimeSpec atime, toCTimeSpec mtime] $ \times ->
        throwErrnoIfMinus1_ "setFdTimesHiRes" (c_futimens fd times)

    {-# LINE 484 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | Like 'touchFile' but uses a file descriptor instead of a path.
    -- This operation is not supported on all platforms. On these platforms,
    -- this function will raise an exception.
    --
    -- Note: calls @futimes@.
    --
    -- @since 2.7.0.0
    touchFd :: Fd -> IO ()

    {-# LINE 494 "libraries/unix/System/Posix/Files/Common.hsc" #-}
    touchFd (Fd fd) =
      throwErrnoIfMinus1_ "touchFd" (c_futimes fd nullPtr)

    {-# LINE 500 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- -----------------------------------------------------------------------------
    -- fchown()

    -- | Acts as 'setOwnerAndGroup' but uses a file descriptor instead of a
    -- 'FilePath'.
    --
    -- Note: calls @fchown@.
    setFdOwnerAndGroup :: Fd -> UserID -> GroupID -> IO ()
    setFdOwnerAndGroup (Fd fd) uid gid =
      throwErrnoIfMinus1_ "setFdOwnerAndGroup" (c_fchown fd uid gid)

    foreign import ccall unsafe "fchown"
      c_fchown :: CInt -> CUid -> CGid -> IO CInt

    -- -----------------------------------------------------------------------------
    -- ftruncate()

    -- | Acts as 'setFileSize' but uses a file descriptor instead of a 'FilePath'.
    --
    -- Note: calls @ftruncate@.
    setFdSize :: Fd -> FileOffset -> IO ()
    setFdSize (Fd fd) off =
      throwErrnoIfMinus1_ "setFdSize" (c_ftruncate fd off)

    -- -----------------------------------------------------------------------------
    -- pathconf()/fpathconf() support

    data PathVar
      = FileSizeBits                  {- _PC_FILESIZEBITS     -}
      | LinkLimit                     {- _PC_LINK_MAX         -}
      | InputLineLimit                {- _PC_MAX_CANON        -}
      | InputQueueLimit               {- _PC_MAX_INPUT        -}
      | FileNameLimit                 {- _PC_NAME_MAX         -}
      | PathNameLimit                 {- _PC_PATH_MAX         -}
      | PipeBufferLimit               {- _PC_PIPE_BUF         -}
                                      -- These are described as optional in POSIX:
                                      {- _PC_ALLOC_SIZE_MIN     -}
                                      {- _PC_REC_INCR_XFER_SIZE -}
                                      {- _PC_REC_MAX_XFER_SIZE  -}
                                      {- _PC_REC_MIN_XFER_SIZE  -}
                                      {- _PC_REC_XFER_ALIGN     -}
      | SymbolicLinkLimit             {- _PC_SYMLINK_MAX      -}
      | SetOwnerAndGroupIsRestricted  {- _PC_CHOWN_RESTRICTED -}
      | FileNamesAreNotTruncated      {- _PC_NO_TRUNC         -}
      | VDisableChar                  {- _PC_VDISABLE         -}
      | AsyncIOAvailable              {- _PC_ASYNC_IO         -}
      | PrioIOAvailable               {- _PC_PRIO_IO          -}
      | SyncIOAvailable               {- _PC_SYNC_IO          -}

    pathVarConst :: PathVar -> CInt
    pathVarConst v = case v of
            LinkLimit                       -> (0)
    {-# LINE 553 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            InputLineLimit                  -> (1)
    {-# LINE 554 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            InputQueueLimit                 -> (2)
    {-# LINE 555 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            FileNameLimit                   -> (3)
    {-# LINE 556 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            PathNameLimit                   -> (4)
    {-# LINE 557 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            PipeBufferLimit                 -> (5)
    {-# LINE 558 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            SetOwnerAndGroupIsRestricted    -> (6)
    {-# LINE 559 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            FileNamesAreNotTruncated        -> (7)
    {-# LINE 560 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            VDisableChar                    -> (8)
    {-# LINE 561 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 563 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            SyncIOAvailable         -> (9)
    {-# LINE 564 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 567 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 569 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            AsyncIOAvailable        -> (10)
    {-# LINE 570 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 573 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 575 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            PrioIOAvailable         -> (11)
    {-# LINE 576 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 579 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 583 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            FileSizeBits            -> error "_PC_FILESIZEBITS not available"

    {-# LINE 585 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    {-# LINE 589 "libraries/unix/System/Posix/Files/Common.hsc" #-}
            SymbolicLinkLimit       -> error "_PC_SYMLINK_MAX not available"

    {-# LINE 591 "libraries/unix/System/Posix/Files/Common.hsc" #-}

    -- | @getFdPathVar var fd@ obtains the dynamic value of the requested
    -- configurable file limit or option associated with the file or directory
    -- attached to the open channel @fd@. For defined file limits, @getFdPathVar@
    -- returns the associated value.  For defined file options, the result of
    -- @getFdPathVar@ is undefined, but not failure.
    --
    -- Note: calls @fpathconf@.
    getFdPathVar :: Fd -> PathVar -> IO Limit
    getFdPathVar (Fd fd) v =
        throwErrnoIfMinus1 "getFdPathVar" $
          c_fpathconf fd (pathVarConst v)

    foreign import ccall unsafe "fpathconf"
      c_fpathconf :: CInt -> CInt -> IO CLong