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|
--------------------------------------------------------------------
-- |
-- Module : Codec.MIME.Decode
-- Copyright : (c) 2006-2009, Galois, Inc.
-- License : BSD3
--
-- Maintainer: Sigbjorn Finne <sigbjorn.finne@gmail.com>
-- Stability : provisional
-- Portability: portable
--
--
--
--------------------------------------------------------------------
module Codec.MIME.Decode where
import Data.Char
import Codec.MIME.QuotedPrintable as QP
import Codec.MIME.Base64 as Base64
-- | @decodeBody enc str@ decodes @str@ according to the scheme
-- specified by @enc@. Currently, @base64@ and @quoted-printable@ are
-- the only two encodings supported. If you supply anything else
-- for @enc@, @decodeBody@ returns @str@.
--
decodeBody :: String -> String -> String
decodeBody enc body =
case map toLower enc of
"base64" -> Base64.decodeToString body
"quoted-printable" -> QP.decode body
_ -> body
-- Decoding of RFC 2047's "encoded-words" production
-- (as used in email-headers and some HTTP header cases
-- (AtomPub's Slug: header))
decodeWord :: String -> Maybe (String, String)
decodeWord str =
case str of
'=':'?':xs ->
case dropLang $ break (\ch -> ch =='?' || ch == '*') xs of
(cs,_:x:'?':bs)
| isKnownCharset (map toLower cs) ->
case toLower x of
'q' -> decodeQ cs (break (=='?') bs)
'b' -> decodeB cs (break (=='?') bs)
_ -> Nothing
_ -> Nothing
_ -> Nothing
where
isKnownCharset cs = cs `elem` ["iso-8859-1", "us-ascii"]
-- ignore RFC 2231 extension of permitting a language tag to be supplied
-- after the charset.
dropLang (as,'*':bs) = (as,dropWhile (/='?') bs)
dropLang (as,bs) = (as,bs)
decodeQ cset (fs,'?':'=':rs) = Just (fromCharset cset (QP.decode fs),rs)
decodeQ _ _ = Nothing
decodeB cset (fs,'?':'=':rs) =
Just (fromCharset cset (Base64.decodeToString fs),rs)
decodeB _ _ = Nothing
fromCharset _cset cs = cs
decodeWords :: String -> String
decodeWords "" = ""
decodeWords (x:xs)
| isSpace x = x : decodeWords xs
| otherwise =
case decodeWord (x:xs) of
Nothing -> x : decodeWords xs
Just (as,bs) -> as ++ decodeWords bs
|
