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|
-- |
-- Module : Codec.Binary.Yenc
-- Copyright : (c) 2007 Magnus Therning
-- License : BSD3
--
-- Implementation based on the specification found at
-- <http://yence.sourceforge.net/docs/protocol/version1_3_draft.html>.
--
-- Further documentation and information can be found at
-- <http://www.haskell.org/haskellwiki/Library/Data_encoding>.
module Codec.Binary.Yenc
( EncIncData(..)
, EncIncRes(..)
, encodeInc
, encode
, DecIncData(..)
, DecIncRes(..)
, decodeInc
, decode
, chop
, unchop
) where
import Codec.Binary.Util
import Data.Word
_criticalsIn = [0xd6, 0xe0, 0xe3, 0x13]
_equal = 0x3d
-- {{{1 encode
-- | Incremental encoder function.
encodeInc :: EncIncData -> EncIncRes [Word8]
encodeInc e = eI e
where
enc [] = []
enc (o:os)
| o `elem` _criticalsIn = _equal : o + 106 : enc os
| otherwise = o + 42 : enc os
eI EDone = EFinal []
eI (EChunk bs) = EPart (enc bs) encodeInc
-- | Encode data.
encode :: [Word8] -> [Word8]
encode = encoder encodeInc
-- {{{1 decode
-- | Incremental decoder function.
decodeInc :: DecIncData [Word8] -> DecIncRes [Word8]
decodeInc d = dI [] d
where
dI [] DDone = DFinal [] []
dI lo DDone = DFail [] lo
dI lo (DChunk s) = doDec [] (lo ++ s)
where
doDec acc (0x3d:d:ds) = doDec (acc ++ [d + 150]) ds
doDec acc (d:ds) = doDec (acc ++ [d + 214]) ds
doDec acc s' = DPart acc (dI s')
-- | Decode data.
decode :: [Word8] -> Maybe [Word8]
decode = decoder decodeInc
-- {{{1 chop
-- | Chop up a string in parts.
chop :: Int -- ^ length of individual lines
-> [Word8]
-> [[Word8]]
chop _ [] = []
chop n ws = let
_n = max n 1
(p1, p2) = splitAt _n ws
in
if last p1 == _equal
then (p1 ++ take 1 p2) : chop _n (drop 1 p2)
else p1 : chop _n p2
-- {{{1 unchop
-- | Concatenate the strings into one long string.
unchop :: [[Word8]]
-> [Word8]
unchop = concat
|
