    {-# 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 hiding (charIsRepresentable)
    import Data.Maybe
    import GHC.Base
    import GHC.Foreign (charIsRepresentable)
    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 (Maybe TextEncoding)
    iconvEncoding = mkIconvEncoding ErrorOnCodingFailure

    -- | Construct an iconv-based 'TextEncoding' for the given character set and
    -- 'CodingFailureMode'.
    --
    -- As iconv is missing in some minimal environments (e.g. #10298), this
    -- checks to ensure that iconv is working properly before returning the
    -- encoding, returning 'Nothing' if not.
    mkIconvEncoding :: CodingFailureMode -> String -> IO (Maybe TextEncoding)
    mkIconvEncoding cfm charset = do
        let enc = TextEncoding {
                      textEncodingName = charset,
                      mkTextDecoder = newIConv raw_charset (haskellChar ++ suffix)
                                               (recoverDecode cfm) iconvDecode,
                      mkTextEncoder = newIConv haskellChar charset
                                               (recoverEncode cfm) iconvEncode}
        good <- charIsRepresentable enc 'a'
        return $ if good
                   then Just enc
                   else Nothing
      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 */