{-# LANGUAGE ForeignFunctionInterface #-}

-- |
-- Module: Codec.Binary.Xx
-- Copyright: (c) 2012 Magnus Therning
-- License: BSD3
--
-- Xxencoding is obsolete but still included for completeness.  Further
-- information on the encoding can be found at
-- <http://en.wikipedia.org/wiki/Xxencode>.  It should be noted that this
-- implementation performs no padding.
--
-- This encoding is very similar to uuencoding, therefore further information
-- regarding the functions can be found in the documentation of
-- "Codec.Binary.Uu".
module Codec.Binary.Xx
    ( xxEncodePart
    , xxEncodeFinal
    , xxDecodePart
    , xxDecodeFinal
    , encode
    , decode
    ) where

import Data.ByteString.Unsafe
import Foreign
import Foreign.C.Types
import System.IO.Unsafe as U
import qualified Data.ByteString as BS

castEnum :: (Enum a, Enum b) => a -> b
castEnum :: a -> b
castEnum = Int -> b
forall a. Enum a => Int -> a
toEnum (Int -> b) -> (a -> Int) -> a -> b
forall b c a. (b -> c) -> (a -> b) -> a -> c
. a -> Int
forall a. Enum a => a -> Int
fromEnum

foreign import ccall "static uu.h xx_enc_part"
    c_xx_enc_part :: Ptr Word8 -> CSize -> Ptr Word8 -> Ptr CSize -> Ptr (Ptr Word8) -> Ptr CSize -> IO ()

foreign import ccall "static uu.h xx_enc_final"
    c_xx_enc_final :: Ptr Word8 -> CSize -> Ptr Word8 -> Ptr CSize -> IO CInt

foreign import ccall "static uu.h xx_dec_part"
    c_xx_dec_part :: Ptr Word8 -> CSize -> Ptr Word8 -> Ptr CSize -> Ptr (Ptr Word8) -> Ptr CSize -> IO CInt

foreign import ccall "static uu.h xx_dec_final"
    c_xx_dec_final :: Ptr Word8 -> CSize -> Ptr Word8 -> Ptr CSize -> IO CInt

-- | Encoding function.
--
-- >>> xxEncodePart $ Data.ByteString.Char8.pack "foo"
-- ("Naxj","")
-- >>> xxEncodePart $ Data.ByteString.Char8.pack "foob"
-- ("Naxj","b")
xxEncodePart :: BS.ByteString -> (BS.ByteString, BS.ByteString)
xxEncodePart :: ByteString -> (ByteString, ByteString)
xxEncodePart ByteString
bs = IO (ByteString, ByteString) -> (ByteString, ByteString)
forall a. IO a -> a
U.unsafePerformIO (IO (ByteString, ByteString) -> (ByteString, ByteString))
-> IO (ByteString, ByteString) -> (ByteString, ByteString)
forall a b. (a -> b) -> a -> b
$ ByteString
-> (CStringLen -> IO (ByteString, ByteString))
-> IO (ByteString, ByteString)
forall a. ByteString -> (CStringLen -> IO a) -> IO a
unsafeUseAsCStringLen ByteString
bs ((CStringLen -> IO (ByteString, ByteString))
 -> IO (ByteString, ByteString))
-> (CStringLen -> IO (ByteString, ByteString))
-> IO (ByteString, ByteString)
forall a b. (a -> b) -> a -> b
$ \ (Ptr CChar
inBuf, Int
inLen) -> do
    let maxOutLen :: Int
maxOutLen = Int
inLen Int -> Int -> Int
forall a. Integral a => a -> a -> a
`div` Int
3 Int -> Int -> Int
forall a. Num a => a -> a -> a
* Int
4
    Ptr Word8
outBuf <- Int -> IO (Ptr Word8)
forall a. Int -> IO (Ptr a)
mallocBytes Int
maxOutLen
    (Ptr CSize -> IO (ByteString, ByteString))
-> IO (ByteString, ByteString)
forall a b. Storable a => (Ptr a -> IO b) -> IO b
alloca ((Ptr CSize -> IO (ByteString, ByteString))
 -> IO (ByteString, ByteString))
-> (Ptr CSize -> IO (ByteString, ByteString))
-> IO (ByteString, ByteString)
forall a b. (a -> b) -> a -> b
$ \ Ptr CSize
pOutLen ->
        (Ptr (Ptr Word8) -> IO (ByteString, ByteString))
-> IO (ByteString, ByteString)
forall a b. Storable a => (Ptr a -> IO b) -> IO b
alloca ((Ptr (Ptr Word8) -> IO (ByteString, ByteString))
 -> IO (ByteString, ByteString))
-> (Ptr (Ptr Word8) -> IO (ByteString, ByteString))
-> IO (ByteString, ByteString)
forall a b. (a -> b) -> a -> b
$ \ Ptr (Ptr Word8)
pRemBuf ->
            (Ptr CSize -> IO (ByteString, ByteString))
-> IO (ByteString, ByteString)
forall a b. Storable a => (Ptr a -> IO b) -> IO b
alloca ((Ptr CSize -> IO (ByteString, ByteString))
 -> IO (ByteString, ByteString))
-> (Ptr CSize -> IO (ByteString, ByteString))
-> IO (ByteString, ByteString)
forall a b. (a -> b) -> a -> b
$ \ Ptr CSize
pRemLen -> do
                Ptr CSize -> CSize -> IO ()
forall a. Storable a => Ptr a -> a -> IO ()
poke Ptr CSize
pOutLen (Int -> CSize
forall a b. (Enum a, Enum b) => a -> b
castEnum Int
maxOutLen)
                Ptr Word8
-> CSize
-> Ptr Word8
-> Ptr CSize
-> Ptr (Ptr Word8)
-> Ptr CSize
-> IO ()
c_xx_enc_part (Ptr CChar -> Ptr Word8
forall a b. Ptr a -> Ptr b
castPtr Ptr CChar
inBuf) (Int -> CSize
forall a b. (Enum a, Enum b) => a -> b
castEnum Int
inLen) Ptr Word8
outBuf Ptr CSize
pOutLen Ptr (Ptr Word8)
pRemBuf Ptr CSize
pRemLen
                CSize
outLen <- Ptr CSize -> IO CSize
forall a. Storable a => Ptr a -> IO a
peek Ptr CSize
pOutLen
                Ptr Word8
remBuf <- Ptr (Ptr Word8) -> IO (Ptr Word8)
forall a. Storable a => Ptr a -> IO a
peek Ptr (Ptr Word8)
pRemBuf
                CSize
remLen <- Ptr CSize -> IO CSize
forall a. Storable a => Ptr a -> IO a
peek Ptr CSize
pRemLen
                ByteString
remBs <- CStringLen -> IO ByteString
BS.packCStringLen (Ptr Word8 -> Ptr CChar
forall a b. Ptr a -> Ptr b
castPtr Ptr Word8
remBuf, CSize -> Int
forall a b. (Enum a, Enum b) => a -> b
castEnum CSize
remLen)
                ByteString
outBs <- Ptr Word8 -> Int -> IO () -> IO ByteString
unsafePackCStringFinalizer Ptr Word8
outBuf (CSize -> Int
forall a b. (Enum a, Enum b) => a -> b
castEnum CSize
outLen) (Ptr Word8 -> IO ()
forall a. Ptr a -> IO ()
free Ptr Word8
outBuf)
                (ByteString, ByteString) -> IO (ByteString, ByteString)
forall (m :: * -> *) a. Monad m => a -> m a
return (ByteString
outBs, ByteString
remBs)

-- | Encoding function for the final block.
--
-- >>> xxEncodeFinal $ Data.ByteString.Char8.pack "r"
-- Just "QU"
-- >>> xxEncodeFinal $ Data.ByteString.Char8.pack "foo"
-- Nothing
xxEncodeFinal :: BS.ByteString -> Maybe BS.ByteString
xxEncodeFinal :: ByteString -> Maybe ByteString
xxEncodeFinal ByteString
bs = IO (Maybe ByteString) -> Maybe ByteString
forall a. IO a -> a
U.unsafePerformIO (IO (Maybe ByteString) -> Maybe ByteString)
-> IO (Maybe ByteString) -> Maybe ByteString
forall a b. (a -> b) -> a -> b
$ ByteString
-> (CStringLen -> IO (Maybe ByteString)) -> IO (Maybe ByteString)
forall a. ByteString -> (CStringLen -> IO a) -> IO a
unsafeUseAsCStringLen ByteString
bs ((CStringLen -> IO (Maybe ByteString)) -> IO (Maybe ByteString))
-> (CStringLen -> IO (Maybe ByteString)) -> IO (Maybe ByteString)
forall a b. (a -> b) -> a -> b
$ \ (Ptr CChar
inBuf, Int
inLen) -> do
    Ptr Word8
outBuf <- Int -> IO (Ptr Word8)
forall a. Int -> IO (Ptr a)
mallocBytes Int
4
    (Ptr CSize -> IO (Maybe ByteString)) -> IO (Maybe ByteString)
forall a b. Storable a => (Ptr a -> IO b) -> IO b
alloca ((Ptr CSize -> IO (Maybe ByteString)) -> IO (Maybe ByteString))
-> (Ptr CSize -> IO (Maybe ByteString)) -> IO (Maybe ByteString)
forall a b. (a -> b) -> a -> b
$ \ Ptr CSize
pOutLen -> do
        CInt
r <- Ptr Word8 -> CSize -> Ptr Word8 -> Ptr CSize -> IO CInt
c_xx_enc_final (Ptr CChar -> Ptr Word8
forall a b. Ptr a -> Ptr b
castPtr Ptr CChar
inBuf) (Int -> CSize
forall a b. (Enum a, Enum b) => a -> b
castEnum Int
inLen) Ptr Word8
outBuf Ptr CSize
pOutLen
        if CInt
r CInt -> CInt -> Bool
forall a. Eq a => a -> a -> Bool
== CInt
0
            then do
                CSize
outLen <- Ptr CSize -> IO CSize
forall a. Storable a => Ptr a -> IO a
peek Ptr CSize
pOutLen
                Ptr Word8
newOutBuf <- Ptr Word8 -> Int -> IO (Ptr Word8)
forall a. Ptr a -> Int -> IO (Ptr a)
reallocBytes Ptr Word8
outBuf (CSize -> Int
forall a b. (Enum a, Enum b) => a -> b
castEnum CSize
outLen)
                ByteString
outBs <- Ptr Word8 -> Int -> IO () -> IO ByteString
unsafePackCStringFinalizer Ptr Word8
newOutBuf (CSize -> Int
forall a b. (Enum a, Enum b) => a -> b
castEnum CSize
outLen) (Ptr Word8 -> IO ()
forall a. Ptr a -> IO ()
free Ptr Word8
newOutBuf)
                Maybe ByteString -> IO (Maybe ByteString)
forall (m :: * -> *) a. Monad m => a -> m a
return (Maybe ByteString -> IO (Maybe ByteString))
-> Maybe ByteString -> IO (Maybe ByteString)
forall a b. (a -> b) -> a -> b
$ ByteString -> Maybe ByteString
forall a. a -> Maybe a
Just ByteString
outBs
            else Ptr Word8 -> IO ()
forall a. Ptr a -> IO ()
free Ptr Word8
outBuf IO () -> IO (Maybe ByteString) -> IO (Maybe ByteString)
forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
>> Maybe ByteString -> IO (Maybe ByteString)
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe ByteString
forall a. Maybe a
Nothing

-- | Decoding function.
--
-- >>> xxDecodePart $ Data.ByteString.Char8.pack "Naxj"
-- Right ("foo","")
-- >>> xxDecodePart $ Data.ByteString.Char8.pack "NaxjMa3"
-- Right ("foo","Ma3")
--
-- >>> xxDecodePart $ Data.ByteString.Char8.pack "Na j"
-- Left ("","Na J")
xxDecodePart :: BS.ByteString -> Either (BS.ByteString, BS.ByteString) (BS.ByteString, BS.ByteString)
xxDecodePart :: ByteString
-> Either (ByteString, ByteString) (ByteString, ByteString)
xxDecodePart ByteString
bs = IO (Either (ByteString, ByteString) (ByteString, ByteString))
-> Either (ByteString, ByteString) (ByteString, ByteString)
forall a. IO a -> a
U.unsafePerformIO (IO (Either (ByteString, ByteString) (ByteString, ByteString))
 -> Either (ByteString, ByteString) (ByteString, ByteString))
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
-> Either (ByteString, ByteString) (ByteString, ByteString)
forall a b. (a -> b) -> a -> b
$ ByteString
-> (CStringLen
    -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall a. ByteString -> (CStringLen -> IO a) -> IO a
unsafeUseAsCStringLen ByteString
bs ((CStringLen
  -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
 -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> (CStringLen
    -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall a b. (a -> b) -> a -> b
$ \ (Ptr CChar
inBuf, Int
inLen) -> do
    let maxOutLen :: Int
maxOutLen = Int
inLen Int -> Int -> Int
forall a. Integral a => a -> a -> a
`div` Int
4 Int -> Int -> Int
forall a. Num a => a -> a -> a
* Int
3
    Ptr Word8
outBuf <- Int -> IO (Ptr Word8)
forall a. Int -> IO (Ptr a)
mallocBytes Int
maxOutLen
    (Ptr CSize
 -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall a b. Storable a => (Ptr a -> IO b) -> IO b
alloca ((Ptr CSize
  -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
 -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> (Ptr CSize
    -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall a b. (a -> b) -> a -> b
$ \ Ptr CSize
pOutLen ->
        (Ptr (Ptr Word8)
 -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall a b. Storable a => (Ptr a -> IO b) -> IO b
alloca ((Ptr (Ptr Word8)
  -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
 -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> (Ptr (Ptr Word8)
    -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall a b. (a -> b) -> a -> b
$ \ Ptr (Ptr Word8)
pRemBuf ->
            (Ptr CSize
 -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall a b. Storable a => (Ptr a -> IO b) -> IO b
alloca ((Ptr CSize
  -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
 -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> (Ptr CSize
    -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall a b. (a -> b) -> a -> b
$ \ Ptr CSize
pRemLen -> do
                Ptr CSize -> CSize -> IO ()
forall a. Storable a => Ptr a -> a -> IO ()
poke Ptr CSize
pOutLen (Int -> CSize
forall a b. (Enum a, Enum b) => a -> b
castEnum Int
maxOutLen)
                CInt
r <- Ptr Word8
-> CSize
-> Ptr Word8
-> Ptr CSize
-> Ptr (Ptr Word8)
-> Ptr CSize
-> IO CInt
c_xx_dec_part (Ptr CChar -> Ptr Word8
forall a b. Ptr a -> Ptr b
castPtr Ptr CChar
inBuf) (Int -> CSize
forall a b. (Enum a, Enum b) => a -> b
castEnum Int
inLen) Ptr Word8
outBuf Ptr CSize
pOutLen Ptr (Ptr Word8)
pRemBuf Ptr CSize
pRemLen
                CSize
outLen <- Ptr CSize -> IO CSize
forall a. Storable a => Ptr a -> IO a
peek Ptr CSize
pOutLen
                Ptr Word8
newOutBuf <- Ptr Word8 -> Int -> IO (Ptr Word8)
forall a. Ptr a -> Int -> IO (Ptr a)
reallocBytes Ptr Word8
outBuf (CSize -> Int
forall a b. (Enum a, Enum b) => a -> b
castEnum CSize
outLen)
                Ptr Word8
remBuf <- Ptr (Ptr Word8) -> IO (Ptr Word8)
forall a. Storable a => Ptr a -> IO a
peek Ptr (Ptr Word8)
pRemBuf
                CSize
remLen <- Ptr CSize -> IO CSize
forall a. Storable a => Ptr a -> IO a
peek Ptr CSize
pRemLen
                ByteString
remBs <- CStringLen -> IO ByteString
BS.packCStringLen (Ptr Word8 -> Ptr CChar
forall a b. Ptr a -> Ptr b
castPtr Ptr Word8
remBuf, CSize -> Int
forall a b. (Enum a, Enum b) => a -> b
castEnum CSize
remLen)
                ByteString
outBs <- Ptr Word8 -> Int -> IO () -> IO ByteString
unsafePackCStringFinalizer Ptr Word8
newOutBuf (CSize -> Int
forall a b. (Enum a, Enum b) => a -> b
castEnum CSize
outLen) (Ptr Word8 -> IO ()
forall a. Ptr a -> IO ()
free Ptr Word8
newOutBuf)
                if CInt
r CInt -> CInt -> Bool
forall a. Eq a => a -> a -> Bool
== CInt
0
                    then Either (ByteString, ByteString) (ByteString, ByteString)
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall (m :: * -> *) a. Monad m => a -> m a
return (Either (ByteString, ByteString) (ByteString, ByteString)
 -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> Either (ByteString, ByteString) (ByteString, ByteString)
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall a b. (a -> b) -> a -> b
$ (ByteString, ByteString)
-> Either (ByteString, ByteString) (ByteString, ByteString)
forall a b. b -> Either a b
Right (ByteString
outBs, ByteString
remBs)
                    else Either (ByteString, ByteString) (ByteString, ByteString)
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall (m :: * -> *) a. Monad m => a -> m a
return (Either (ByteString, ByteString) (ByteString, ByteString)
 -> IO (Either (ByteString, ByteString) (ByteString, ByteString)))
-> Either (ByteString, ByteString) (ByteString, ByteString)
-> IO (Either (ByteString, ByteString) (ByteString, ByteString))
forall a b. (a -> b) -> a -> b
$ (ByteString, ByteString)
-> Either (ByteString, ByteString) (ByteString, ByteString)
forall a b. a -> Either a b
Left (ByteString
outBs, ByteString
remBs)

-- | Decoding function for the final block.
--
-- >>> xxDecodeFinal $ Data.ByteString.Char8.pack "Naw"
-- Just "fo"
-- >>> xxDecodeFinal $ Data.ByteString.Char8.pack ""
-- Just ""
-- >>> xxDecodeFinal $ Data.ByteString.Char8.pack "Na "
-- Nothing
--
-- >>> xxDecodeFinal $ encode $ Data.ByteString.Char8.pack "foo"
-- Nothing
xxDecodeFinal :: BS.ByteString -> Maybe BS.ByteString
xxDecodeFinal :: ByteString -> Maybe ByteString
xxDecodeFinal ByteString
bs = IO (Maybe ByteString) -> Maybe ByteString
forall a. IO a -> a
U.unsafePerformIO (IO (Maybe ByteString) -> Maybe ByteString)
-> IO (Maybe ByteString) -> Maybe ByteString
forall a b. (a -> b) -> a -> b
$ ByteString
-> (CStringLen -> IO (Maybe ByteString)) -> IO (Maybe ByteString)
forall a. ByteString -> (CStringLen -> IO a) -> IO a
unsafeUseAsCStringLen ByteString
bs ((CStringLen -> IO (Maybe ByteString)) -> IO (Maybe ByteString))
-> (CStringLen -> IO (Maybe ByteString)) -> IO (Maybe ByteString)
forall a b. (a -> b) -> a -> b
$ \ (Ptr CChar
inBuf, Int
inLen) -> do
    Ptr Word8
outBuf <- Int -> IO (Ptr Word8)
forall a. Int -> IO (Ptr a)
mallocBytes Int
3
    (Ptr CSize -> IO (Maybe ByteString)) -> IO (Maybe ByteString)
forall a b. Storable a => (Ptr a -> IO b) -> IO b
alloca ((Ptr CSize -> IO (Maybe ByteString)) -> IO (Maybe ByteString))
-> (Ptr CSize -> IO (Maybe ByteString)) -> IO (Maybe ByteString)
forall a b. (a -> b) -> a -> b
$ \ Ptr CSize
pOutLen -> do
        CInt
r <- Ptr Word8 -> CSize -> Ptr Word8 -> Ptr CSize -> IO CInt
c_xx_dec_final (Ptr CChar -> Ptr Word8
forall a b. Ptr a -> Ptr b
castPtr Ptr CChar
inBuf) (Int -> CSize
forall a b. (Enum a, Enum b) => a -> b
castEnum Int
inLen) Ptr Word8
outBuf Ptr CSize
pOutLen
        if CInt
r CInt -> CInt -> Bool
forall a. Eq a => a -> a -> Bool
== CInt
0
            then do
                CSize
outLen <- Ptr CSize -> IO CSize
forall a. Storable a => Ptr a -> IO a
peek Ptr CSize
pOutLen
                Ptr Word8
newOutBuf <- Ptr Word8 -> Int -> IO (Ptr Word8)
forall a. Ptr a -> Int -> IO (Ptr a)
reallocBytes Ptr Word8
outBuf (CSize -> Int
forall a b. (Enum a, Enum b) => a -> b
castEnum CSize
outLen)
                ByteString
outBs <- Ptr Word8 -> Int -> IO () -> IO ByteString
unsafePackCStringFinalizer Ptr Word8
newOutBuf (CSize -> Int
forall a b. (Enum a, Enum b) => a -> b
castEnum CSize
outLen) (Ptr Word8 -> IO ()
forall a. Ptr a -> IO ()
free Ptr Word8
newOutBuf)
                Maybe ByteString -> IO (Maybe ByteString)
forall (m :: * -> *) a. Monad m => a -> m a
return (Maybe ByteString -> IO (Maybe ByteString))
-> Maybe ByteString -> IO (Maybe ByteString)
forall a b. (a -> b) -> a -> b
$ ByteString -> Maybe ByteString
forall a. a -> Maybe a
Just ByteString
outBs
            else Ptr Word8 -> IO ()
forall a. Ptr a -> IO ()
free Ptr Word8
outBuf IO () -> IO (Maybe ByteString) -> IO (Maybe ByteString)
forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
>> Maybe ByteString -> IO (Maybe ByteString)
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe ByteString
forall a. Maybe a
Nothing

encode :: BS.ByteString -> BS.ByteString
encode :: ByteString -> ByteString
encode ByteString
bs = ByteString
first ByteString -> ByteString -> ByteString
`BS.append` ByteString
final
    where
        (ByteString
first, ByteString
rest) = ByteString -> (ByteString, ByteString)
xxEncodePart ByteString
bs
        Just ByteString
final = ByteString -> Maybe ByteString
xxEncodeFinal ByteString
rest

decode :: BS.ByteString -> Either (BS.ByteString, BS.ByteString) BS.ByteString
decode :: ByteString -> Either (ByteString, ByteString) ByteString
decode ByteString
bs = ((ByteString, ByteString)
 -> Either (ByteString, ByteString) ByteString)
-> ((ByteString, ByteString)
    -> Either (ByteString, ByteString) ByteString)
-> Either (ByteString, ByteString) (ByteString, ByteString)
-> Either (ByteString, ByteString) ByteString
forall a c b. (a -> c) -> (b -> c) -> Either a b -> c
either
    (ByteString, ByteString)
-> Either (ByteString, ByteString) ByteString
forall a b. a -> Either a b
Left
    (\ (ByteString
first, ByteString
rest) ->
        Either (ByteString, ByteString) ByteString
-> (ByteString -> Either (ByteString, ByteString) ByteString)
-> Maybe ByteString
-> Either (ByteString, ByteString) ByteString
forall b a. b -> (a -> b) -> Maybe a -> b
maybe
            ((ByteString, ByteString)
-> Either (ByteString, ByteString) ByteString
forall a b. a -> Either a b
Left (ByteString
first, ByteString
rest))
            (\ ByteString
fin -> ByteString -> Either (ByteString, ByteString) ByteString
forall a b. b -> Either a b
Right (ByteString
first ByteString -> ByteString -> ByteString
`BS.append` ByteString
fin))
            (ByteString -> Maybe ByteString
xxDecodeFinal ByteString
rest))
    (ByteString
-> Either (ByteString, ByteString) (ByteString, ByteString)
xxDecodePart ByteString
bs)