    {-# OPTIONS_GHC  -XNoImplicitPrelude -funbox-strict-fields #-}
    {-# LANGUAGE BangPatterns #-}
    -----------------------------------------------------------------------------
    -- |
    -- Module      :  GHC.IO.Encoding.Latin1
    -- Copyright   :  (c) The University of Glasgow, 2009
    -- License     :  see libraries/base/LICENSE
    --
    -- Maintainer  :  libraries@haskell.org
    -- Stability   :  internal
    -- Portability :  non-portable
    --
    -- UTF-32 Codecs for the IO library
    --
    -- Portions Copyright   : (c) Tom Harper 2008-2009,
    --                        (c) Bryan O'Sullivan 2009,
    --                        (c) Duncan Coutts 2009
    --
    -----------------------------------------------------------------------------

    module GHC.IO.Encoding.Latin1 (
      latin1,
      latin1_checked,
      latin1_decode,
      latin1_encode,
      latin1_checked_encode,
      ) where

    import GHC.Base
    import GHC.Real
    import GHC.Num
    -- import GHC.IO
    import GHC.IO.Exception
    import GHC.IO.Buffer
    import GHC.IO.Encoding.Types
    import Data.Maybe

    -- -----------------------------------------------------------------------------
    -- Latin1

    latin1 :: TextEncoding
    latin1 = TextEncoding { textEncodingName = "ISO8859-1",
                            mkTextDecoder = latin1_DF,
                            mkTextEncoder = latin1_EF }

    latin1_DF :: IO (TextDecoder ())
    latin1_DF =
      return (BufferCodec {
                 encode   = latin1_decode,
                 close    = return (),
                 getState = return (),
                 setState = const $ return ()
              })

    latin1_EF :: IO (TextEncoder ())
    latin1_EF =
      return (BufferCodec {
                 encode   = latin1_encode,
                 close    = return (),
                 getState = return (),
                 setState = const $ return ()
              })

    latin1_checked :: TextEncoding
    latin1_checked = TextEncoding { textEncodingName = "ISO8859-1(checked)",
                                    mkTextDecoder = latin1_DF,
                                    mkTextEncoder = latin1_checked_EF }

    latin1_checked_EF :: IO (TextEncoder ())
    latin1_checked_EF =
      return (BufferCodec {
                 encode   = latin1_checked_encode,
                 close    = return (),
                 getState = return (),
                 setState = const $ return ()
              })

    latin1_decode :: DecodeBuffer
    latin1_decode
      input@Buffer{  bufRaw=iraw, bufL=ir0, bufR=iw,  bufSize=_  }
      output@Buffer{ bufRaw=oraw, bufL=_,   bufR=ow0, bufSize=os }
     = let
           loop !ir !ow
             | ow >= os || ir >= iw =  done ir ow
             | otherwise = do
                  c0 <- readWord8Buf iraw ir
                  ow' <- writeCharBuf oraw ow (unsafeChr (fromIntegral c0))
                  loop (ir+1) ow'

           -- lambda-lifted, to avoid thunks being built in the inner-loop:
           done !ir !ow = return (if ir == iw then input{ bufL=0, bufR=0 }
                                              else input{ bufL=ir },
                             output{ bufR=ow })
        in
        loop ir0 ow0

    latin1_encode :: EncodeBuffer
    latin1_encode
      input@Buffer{  bufRaw=iraw, bufL=ir0, bufR=iw,  bufSize=_  }
      output@Buffer{ bufRaw=oraw, bufL=_,   bufR=ow0, bufSize=os }
     = let
          done !ir !ow = return (if ir == iw then input{ bufL=0, bufR=0 }
                                             else input{ bufL=ir },
                                 output{ bufR=ow })
          loop !ir !ow
            | ow >= os || ir >= iw =  done ir ow
            | otherwise = do
               (c,ir') <- readCharBuf iraw ir
               writeWord8Buf oraw ow (fromIntegral (ord c))
               loop ir' (ow+1)
        in
        loop ir0 ow0

    latin1_checked_encode :: EncodeBuffer
    latin1_checked_encode
      input@Buffer{  bufRaw=iraw, bufL=ir0, bufR=iw,  bufSize=_  }
      output@Buffer{ bufRaw=oraw, bufL=_,   bufR=ow0, bufSize=os }
     = let
          done !ir !ow = return (if ir == iw then input{ bufL=0, bufR=0 }
                                             else input{ bufL=ir },
                                 output{ bufR=ow })
          loop !ir !ow
            | ow >= os || ir >= iw =  done ir ow
            | otherwise = do
               (c,ir') <- readCharBuf iraw ir
               if ord c > 0xff then invalid else do
               writeWord8Buf oraw ow (fromIntegral (ord c))
               loop ir' (ow+1)
            where
               invalid = if ir > ir0 then done ir ow else ioe_encodingError
        in
        loop ir0 ow0

    ioe_encodingError :: IO a
    ioe_encodingError = ioException
         (IOError Nothing InvalidArgument "latin1_checked_encode"
              "character is out of range for this encoding" Nothing Nothing)