Win32.hs

-- Copyright 2007-2009, Judah Jacobson.
-- All Rights Reserved.

-- Redistribution and use in source and binary forms, with or without
-- modification, are permitted provided that the following conditions are met:

-- - Redistribution of source code must retain the above copyright notice,
-- this list of conditions and the following disclaimer.

-- - Redistribution in binary form must reproduce the above copyright notice,
-- this list of conditions and the following disclaimer in the documentation
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-- THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND ANY
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-- DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR THE CONTRIBUTORS BE LIABLE
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-- USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
{-# LANGUAGE CPP, ForeignFunctionInterface #-}
module Darcs.Util.Encoding.Win32
    ( encode, decode
    ) where

import Darcs.Prelude

import Data.ByteString.Internal ( createAndTrim )
import qualified Data.ByteString as B
    ( ByteString, useAsCStringLen )
import Foreign ( castPtr, allocaArray0 )
import Foreign.C
    ( CInt(..), peekCWStringLen, withCWStringLen )
import System.Win32
    ( CodePage, nullPtr, getConsoleCP, getACP
    , LPCSTR, LPWSTR, LPCWSTR, LPBOOL, DWORD )

#include <windows_cconv.h>

-- | Encode a Unicode 'String' into a 'ByteString' suitable for the current
-- console.
encode :: String -> IO B.ByteString
encode str = getCodePage >>= flip unicodeToCodePage str

-- | Convert a 'ByteString' from the console's encoding into a Unicode 'String'.
decode :: B.ByteString -> IO String
decode str = getCodePage >>= flip codePageToUnicode str

------------------------
-- Multi-byte conversion

foreign import WINDOWS_CCONV "WideCharToMultiByte" wideCharToMultiByte
        :: CodePage -> DWORD -> LPCWSTR -> CInt -> LPCSTR -> CInt
                -> LPCSTR -> LPBOOL -> IO CInt

unicodeToCodePage :: CodePage -> String -> IO B.ByteString
unicodeToCodePage cp wideStr = withCWStringLen wideStr $ \(wideBuff, wideLen) -> do
    -- first, ask for the length without filling the buffer.
    outSize <- wideCharToMultiByte cp 0 wideBuff (toEnum wideLen)
                    nullPtr 0 nullPtr nullPtr
    -- then, actually perform the encoding.
    createAndTrim (fromEnum outSize) $ \outBuff ->
        fmap fromEnum $ wideCharToMultiByte cp 0 wideBuff (toEnum wideLen)
                    (castPtr outBuff) outSize nullPtr nullPtr

foreign import WINDOWS_CCONV "MultiByteToWideChar" multiByteToWideChar
        :: CodePage -> DWORD -> LPCSTR -> CInt -> LPWSTR -> CInt -> IO CInt

codePageToUnicode :: CodePage -> B.ByteString -> IO String
codePageToUnicode cp bs = B.useAsCStringLen bs $ \(inBuff, inLen) -> do
    -- first ask for the size without filling the buffer.
    outSize <- multiByteToWideChar cp 0 inBuff (toEnum inLen) nullPtr 0
    -- then, actually perform the decoding.
    allocaArray0 (fromEnum outSize) $ \outBuff -> do
        outSize' <- multiByteToWideChar cp 0 inBuff (toEnum inLen) outBuff outSize
        peekCWStringLen (outBuff, fromEnum outSize')

getCodePage :: IO CodePage
getCodePage = do
    conCP <- getConsoleCP
    if conCP > 0
        then return conCP
        else getACP