    {-# LANGUAGE Trustworthy #-}
    {-# LANGUAGE CPP
               , NoImplicitPrelude
               , NondecreasingIndentation
      #-}
    {-# OPTIONS_HADDOCK hide #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  GHC.IO.Encoding.Iconv
    -- Copyright   :  (c) The University of Glasgow, 2008-2009
    -- License     :  see libraries/base/LICENSE
    --
    -- Maintainer  :  libraries@haskell.org
    -- Stability   :  internal
    -- Portability :  non-portable
    --
    -- This module provides text encoding/decoding using iconv
    --
    -----------------------------------------------------------------------------

    module GHC.IO.Encoding.Iconv (
    #if !defined(mingw32_HOST_OS)
       iconvEncoding, mkIconvEncoding,
       localeEncodingName
    #endif
     ) where

    #include "MachDeps.h"
    #include "HsBaseConfig.h"

    #if defined(mingw32_HOST_OS)
    import GHC.Base () -- For build ordering
    #else

    import Foreign
    import Foreign.C
    import Data.Maybe
    import GHC.Base
    import GHC.IO.Buffer
    import GHC.IO.Encoding.Failure
    import GHC.IO.Encoding.Types
    import GHC.List (span)
    import GHC.Num
    import GHC.Show
    import GHC.Real
    import System.IO.Unsafe (unsafePerformIO)
    import System.Posix.Internals

    c_DEBUG_DUMP :: Bool
    c_DEBUG_DUMP = False

    iconv_trace :: String -> IO ()
    iconv_trace s
     | c_DEBUG_DUMP = puts s
     | otherwise    = return ()

    -- -----------------------------------------------------------------------------
    -- iconv encoders/decoders

    {-# NOINLINE localeEncodingName #-}
    localeEncodingName :: String
    localeEncodingName = unsafePerformIO $ do
       -- Use locale_charset() or nl_langinfo(CODESET) to get the encoding
       -- if we have either of them.
       cstr <- c_localeEncoding
       peekCAString cstr -- Assume charset names are ASCII

    -- We hope iconv_t is a storable type.  It should be, since it has at least the
    -- value -1, which is a possible return value from iconv_open.
    type IConv = CLong -- ToDo: (#type iconv_t)

    foreign import ccall unsafe "hs_iconv_open"
        hs_iconv_open :: CString -> CString -> IO IConv

    foreign import ccall unsafe "hs_iconv_close"
        hs_iconv_close :: IConv -> IO CInt

    foreign import ccall unsafe "hs_iconv"
        hs_iconv :: IConv -> Ptr CString -> Ptr CSize -> Ptr CString -> Ptr CSize
              -> IO CSize

    foreign import ccall unsafe "localeEncoding"
        c_localeEncoding :: IO CString

    haskellChar :: String
    #ifdef WORDS_BIGENDIAN
    haskellChar | charSize == 2 = "UTF-16BE"
                | otherwise     = "UTF-32BE"
    #else
    haskellChar | charSize == 2 = "UTF-16LE"
                | otherwise     = "UTF-32LE"
    #endif

    char_shift :: Int
    char_shift | charSize == 2 = 1
               | otherwise     = 2

    iconvEncoding :: String -> IO TextEncoding
    iconvEncoding = mkIconvEncoding ErrorOnCodingFailure

    mkIconvEncoding :: CodingFailureMode -> String -> IO TextEncoding
    mkIconvEncoding cfm charset = do
      return (TextEncoding {
                    textEncodingName = charset,
                    mkTextDecoder = newIConv raw_charset (haskellChar ++ suffix) (recoverDecode cfm) iconvDecode,
                    mkTextEncoder = newIConv haskellChar charset                 (recoverEncode cfm) iconvEncode})
      where
        -- An annoying feature of GNU iconv is that the //PREFIXES only take
        -- effect when they appear on the tocode parameter to iconv_open:
        (raw_charset, suffix) = span (/= '/') charset

    newIConv :: String -> String
       -> (Buffer a -> Buffer b -> IO (Buffer a, Buffer b))
       -> (IConv -> Buffer a -> Buffer b -> IO (CodingProgress, Buffer a, Buffer b))
       -> IO (BufferCodec a b ())
    newIConv from to rec fn =
      -- Assume charset names are ASCII
      withCAString from $ \ from_str ->
      withCAString to   $ \ to_str -> do
        iconvt <- throwErrnoIfMinus1 "mkTextEncoding" $ hs_iconv_open to_str from_str
        let iclose = throwErrnoIfMinus1_ "Iconv.close" $ hs_iconv_close iconvt
        return BufferCodec{
                    encode = fn iconvt,
                    recover = rec,
                    close  = iclose,
                    -- iconv doesn't supply a way to save/restore the state
                    getState = return (),
                    setState = const $ return ()
                    }

    iconvDecode :: IConv -> DecodeBuffer
    iconvDecode iconv_t ibuf obuf = iconvRecode iconv_t ibuf 0 obuf char_shift

    iconvEncode :: IConv -> EncodeBuffer
    iconvEncode iconv_t ibuf obuf = iconvRecode iconv_t ibuf char_shift obuf 0

    iconvRecode :: IConv -> Buffer a -> Int -> Buffer b -> Int
                -> IO (CodingProgress, Buffer a, Buffer b)
    iconvRecode iconv_t
      input@Buffer{  bufRaw=iraw, bufL=ir, bufR=iw, bufSize=_  }  iscale
      output@Buffer{ bufRaw=oraw, bufL=_,  bufR=ow, bufSize=os }  oscale
      = do
        iconv_trace ("haskellChar=" ++ show haskellChar)
        iconv_trace ("iconvRecode before, input=" ++ show (summaryBuffer input))
        iconv_trace ("iconvRecode before, output=" ++ show (summaryBuffer output))
        withRawBuffer iraw $ \ piraw -> do
        withRawBuffer oraw $ \ poraw -> do
        with (piraw `plusPtr` (ir `shiftL` iscale)) $ \ p_inbuf -> do
        with (poraw `plusPtr` (ow `shiftL` oscale)) $ \ p_outbuf -> do
        with (fromIntegral ((iw-ir) `shiftL` iscale)) $ \ p_inleft -> do
        with (fromIntegral ((os-ow) `shiftL` oscale)) $ \ p_outleft -> do
          res <- hs_iconv iconv_t p_inbuf p_inleft p_outbuf p_outleft
          new_inleft  <- peek p_inleft
          new_outleft <- peek p_outleft
          let
              new_inleft'  = fromIntegral new_inleft `shiftR` iscale
              new_outleft' = fromIntegral new_outleft `shiftR` oscale
              new_input
                | new_inleft == 0  = input { bufL = 0, bufR = 0 }
                | otherwise        = input { bufL = iw - new_inleft' }
              new_output = output{ bufR = os - new_outleft' }
          iconv_trace ("iconv res=" ++ show res)
          iconv_trace ("iconvRecode after,  input=" ++ show (summaryBuffer new_input))
          iconv_trace ("iconvRecode after,  output=" ++ show (summaryBuffer new_output))
          if (res /= -1)
            then do -- all input translated
               return (InputUnderflow, new_input, new_output)
            else do
          errno <- getErrno
          case errno of
            e | e == e2BIG  -> return (OutputUnderflow, new_input, new_output)
              | e == eINVAL -> return (InputUnderflow, new_input, new_output)
               -- Sometimes iconv reports EILSEQ for a
               -- character in the input even when there is no room
               -- in the output; in this case we might be about to
               -- change the encoding anyway, so the following bytes
               -- could very well be in a different encoding.
               --
               -- Because we can only say InvalidSequence if there is at least
               -- one element left in the output, we have to special case this.
              | e == eILSEQ -> return (if new_outleft' == 0 then OutputUnderflow else InvalidSequence, new_input, new_output)
              | otherwise -> do
                  iconv_trace ("iconv returned error: " ++ show (errnoToIOError "iconv" e Nothing Nothing))
                  throwErrno "iconvRecoder"

    #endif /* !mingw32_HOST_OS */