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|
-- |
-- Module : Codec.Binary.QuotedPrintable
-- Copyright : (c) 2009 Magnus Therning
-- License : BSD3
--
-- Implementation of Quoted-Printable based on RFC 2045
-- (<http://tools.ietf.org/html/rfc2045>).
--
-- This encoding encodes _everything_ that is passed in, it will not try to
-- guess the native line ending for your architecture. In other words, if you
-- are using this to encode text you need to split it into separate lines
-- before encoding and chopping it up.
--
-- Further documentation and information can be found at
-- <http://www.haskell.org/haskellwiki/Library/Data_encoding>.
module Codec.Binary.QuotedPrintable
( EncIncData(..)
, EncIncRes(..)
, encodeInc
, encode
, DecIncData(..)
, DecIncRes(..)
, decodeInc
, decode
, chop
, unchop
) where
import Codec.Binary.Util
import Data.Char
import Data.Maybe
import Data.Word
-- {{{1 encode
-- | Incremental encoder function.
encodeInc :: EncIncData -> EncIncRes String
encodeInc e = eI e
where
enc [] = []
enc (o:os)
| o < 33 || o == 61 || o > 126 = ('=' : toHex o) ++ enc os
| otherwise = chr (fromIntegral o) : enc os
eI EDone = EFinal []
eI (EChunk bs) = EPart (enc bs) encodeInc
-- | Encode data.
encode :: [Word8] -> String
encode = encoder encodeInc
-- {{{1 decode
-- | Incremental decoder function.
decodeInc :: DecIncData String -> DecIncRes String
decodeInc d = dI [] d
where
dI [] DDone = DFinal [] []
dI lo DDone = DFail [] lo
dI lo (DChunk s) = doDec [] (lo ++ s)
where
doDec acc [] = DPart acc (dI [])
doDec acc s'@('=':c0:c1:cs) = let
o = fromHex [c0, c1]
in if isJust o
then doDec (acc ++ [fromJust o]) cs
else DFail acc s'
doDec acc s'@(c:cs)
| c /= '=' = doDec (acc ++ [fromIntegral $ ord c]) cs
| otherwise = DPart acc (dI s')
-- | Decode data.
decode :: String -> Maybe [Word8]
decode = decoder decodeInc
-- {{{1 chop
-- | Chop up a string in parts.
chop :: Int -- ^ length of individual lines (values @\< 4@ are ignored)
-> String
-> [String]
chop n "" = []
chop n s = let
n' = max 3 $ n - 1
_c i ts "" acc = ts : acc
_c i ts tss@('=' : tss') acc
| i + 2 < n' = _c (i + 1) ('=' : ts) tss' acc
| otherwise = _c 0 "" tss (('=' : ts) : acc)
_c i ts tss@(c : tss') acc
| i < n' = _c (i + 1) (c : ts) tss' acc
| otherwise = _c 0 "" tss (('=' : ts) : acc)
in map reverse . reverse $ _c 0 "" s []
-- {{{1 unchop
-- | Concatenate the list of strings into one long string.
unchop :: [String] -> String
unchop [] = ""
unchop (s : ss) = let
dropLast = last s == '='
len = length s
in if dropLast
then take (len - 1) s ++ unchop ss
else s ++ unchop ss
|
