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|
{- A simple RFC1342 decoder.
-
- Copyright 2013 Raúl Benencia <rul@kalgan.cc>
-
- Licensed under the GNU GPL version 3 or higher
-
-}
module Rfc1342 (decodeField) where
import qualified Codec.Binary.Base64 as B64
import qualified Codec.Binary.QuotedPrintable as QP
import Data.Char (toLower, isSpace, chr)
import Data.List(isPrefixOf)
import Data.Word (Word8)
import Data.Encoding(decodeString)
-- Encoding imports. If you want to support more encodings, just add'em here.
import Data.Encoding.UTF8
import Data.Encoding.ISO88591
import Data.Encoding.ISO88592
import Data.Encoding.ISO88598
import Data.Encoding.ISO88599
decodeField :: String -> String
decodeField ('=':'?':cs) = decodeWithCharset dec rest
where (encoding, rest) = span (\c -> c /= '?') cs
dec = case (map toLower encoding) of
"utf-8" -> decodeString UTF8
"iso-8859-1" -> decodeString ISO88591
"iso-8859-2" -> decodeString ISO88592
"iso-8859-8" -> decodeString ISO88598
"iso-8859-9" -> decodeString ISO88599
_ -> id
decodeField [] = []
decodeField (c:cs) = c:decodeField cs
decodeWithCharset dec [] = []
decodeWithCharset dec ('?':c:'?':cs) | toLower c == 'b' = dataDecodeWith B64.decode
| toLower c == 'q' = dataDecodeWith QP.decode
| otherwise = cs
where (encoded, rest') = span (\c -> c /= '?') cs
rest = if "?=" `isPrefixOf` rest'
then drop 2 rest'
else rest'
dataDecodeWith datadec = (_2spc . dec . unwrap . datadec $ encoded) ++ (decodeField $ dropWhile isSpace rest)
unwrap :: Maybe [Word8] -> String
unwrap Nothing = []
unwrap (Just str) = bytesToString str
bytesToString :: [Word8] -> String
bytesToString = map (chr . fromIntegral)
-- Sometimes an underscore represents the SPACE character
_2spc = map (\x -> if x == '_' then ' ' else x)
|
