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|
{- -*- Mode: haskell; -*-
Haskell magic Interface
Copyright (C) 2005 John Goerzen <jgoerzen@complete.org>
This code is under a 3-clause BSD license; see COPYING for details.
-}
{- |
Module : Magic.Utils
Copyright : Copyright (C) 2005 John Goerzen
License : BSD
Maintainer : John Goerzen,
Maintainer : jgoerzen\@complete.org
Stability : provisional
Portability: portable
Utils
Written by John Goerzen, jgoerzen\@complete.org
-}
module Magic.Utils (flaglist2int, fromMagicPtr, withMagicPtr, checkIntError,
throwErrorIfNull)
where
import Foreign
import Foreign.C.Error
import Foreign.C.String
import Foreign.ForeignPtr
import Magic.TypesLL
import Magic.Types
import Data.Bits
import Foreign.C.Types
import Magic.Data
flaglist2int :: [MagicFlag] -> CInt
flaglist2int mfl =
foldl (\c f -> c .|. (fromIntegral . fromEnum $ f)) 0 mfl
fromMagicPtr :: String -> IO (Ptr CMagic) -> IO Magic
fromMagicPtr caller action =
do ptr <- throwErrnoIfNull caller action
newForeignPtr magic_close ptr
throwErrorIfNull :: String -> Magic -> IO (Ptr a) -> IO (Ptr a)
throwErrorIfNull caller m action =
do res <- action
if res == nullPtr
then throwError caller m
else return res
withMagicPtr :: Magic -> (Ptr CMagic -> IO a) -> IO a
withMagicPtr m = withForeignPtr m
throwError :: String -> Magic -> IO a
throwError caller m = withMagicPtr m (\cmagic ->
do errormsg <- magic_error cmagic
if errormsg /= nullPtr
then do em <- peekCString errormsg
fail $ caller ++ ": " ++ em
else fail $ caller ++ ": got error code but no error message"
)
checkIntError :: String -> Magic -> IO CInt -> IO ()
checkIntError caller m action =
do res <- action
if res == 0
then return ()
else throwError caller m
foreign import ccall unsafe "magic.h &magic_close"
magic_close :: FunPtr (Ptr CMagic -> IO ())
foreign import ccall unsafe "magic.h magic_error"
magic_error :: Ptr CMagic -> IO CString
|
