hledger/hledger-lib/Hledger/Utils/UTF8IOCompat.hs

124 lines
3.6 KiB
Haskell

{-# LANGUAGE CPP #-}
{- |
UTF-8 aware string IO functions that will work across multiple platforms
and GHC versions. Includes code from Text.Pandoc.UTF8 ((C) 2010 John
MacFarlane).
Example usage:
import Prelude hiding (readFile,writeFile,appendFile,getContents,putStr,putStrLn)
import UTF8IOCompat (readFile,writeFile,appendFile,getContents,putStr,putStrLn)
import UTF8IOCompat (SystemString,fromSystemString,toSystemString,error',userError')
2013/4/10 update: we now trust that current GHC versions & platforms
do the right thing, so this file is a no-op and on its way to being removed.
Not carefully tested.
-}
-- TODO obsolete ?
module Hledger.Utils.UTF8IOCompat (
readFile,
writeFile,
appendFile,
getContents,
hGetContents,
putStr,
putStrLn,
hPutStr,
hPutStrLn,
--
SystemString,
fromSystemString,
toSystemString,
error',
userError',
usageError,
)
where
-- import Control.Monad (liftM)
-- import qualified Data.ByteString.Lazy as B
-- import qualified Data.ByteString.Lazy.Char8 as B8
-- import qualified Data.ByteString.Lazy.UTF8 as U8 (toString, fromString)
import Prelude hiding (readFile, writeFile, appendFile, getContents, putStr, putStrLn)
import System.IO -- (Handle)
-- bom :: B.ByteString
-- bom = B.pack [0xEF, 0xBB, 0xBF]
-- stripBOM :: B.ByteString -> B.ByteString
-- stripBOM s | bom `B.isPrefixOf` s = B.drop 3 s
-- stripBOM s = s
-- readFile :: FilePath -> IO String
-- readFile = liftM (U8.toString . stripBOM) . B.readFile
-- writeFile :: FilePath -> String -> IO ()
-- writeFile f = B.writeFile f . U8.fromString
-- appendFile :: FilePath -> String -> IO ()
-- appendFile f = B.appendFile f . U8.fromString
-- getContents :: IO String
-- getContents = liftM (U8.toString . stripBOM) B.getContents
-- hGetContents :: Handle -> IO String
-- hGetContents h = liftM (U8.toString . stripBOM) (B.hGetContents h)
-- putStr :: String -> IO ()
-- putStr = bs_putStr . U8.fromString
-- putStrLn :: String -> IO ()
-- putStrLn = bs_putStrLn . U8.fromString
-- hPutStr :: Handle -> String -> IO ()
-- hPutStr h = bs_hPutStr h . U8.fromString
-- hPutStrLn :: Handle -> String -> IO ()
-- hPutStrLn h = bs_hPutStrLn h . U8.fromString
-- -- span GHC versions including 6.12.3 - 7.4.1:
-- bs_putStr = B8.putStr
-- bs_putStrLn = B8.putStrLn
-- bs_hPutStr = B8.hPut
-- bs_hPutStrLn h bs = B8.hPut h bs >> B8.hPut h (B.singleton 0x0a)
-- | A string received from or being passed to the operating system, such
-- as a file path, command-line argument, or environment variable name or
-- value. With GHC versions before 7.2 on some platforms (posix) these are
-- typically encoded. When converting, we assume the encoding is UTF-8 (cf
-- <http://www.dwheeler.com/essays/fixing-unix-linux-filenames.html#UTF8>).
type SystemString = String
-- | Convert a system string to an ordinary string, decoding from UTF-8 if
-- it appears to be UTF8-encoded and GHC version is less than 7.2.
fromSystemString :: SystemString -> String
fromSystemString = id
-- | Convert a unicode string to a system string, encoding with UTF-8 if
-- we are on a posix platform with GHC < 7.2.
toSystemString :: String -> SystemString
toSystemString = id
-- | A SystemString-aware version of error.
error' :: String -> a
error' =
#if __GLASGOW_HASKELL__ < 800
-- (easier than if base < 4.9)
error . toSystemString
#else
errorWithoutStackTrace . toSystemString
#endif
-- | A SystemString-aware version of userError.
userError' :: String -> IOError
userError' = userError . toSystemString
-- | A SystemString-aware version of error that adds a usage hint.
usageError :: String -> a
usageError = error' . (++ " (use -h to see usage)")