    {-# LANGUAGE CPP, FlexibleContexts #-}
    #if __GLASGOW_HASKELL__ >= 701
    {-# LANGUAGE Trustworthy #-}
    #endif
    #ifdef GENERICS
    {-# LANGUAGE DefaultSignatures #-}
    #endif

    #if MIN_VERSION_base(4,8,0)
    #define HAS_NATURAL
    #endif

    -----------------------------------------------------------------------------
    -- |
    -- Module      : Data.Binary.Class
    -- Copyright   : Lennart Kolmodin
    -- License     : BSD3-style (see LICENSE)
    --
    -- Maintainer  : Lennart Kolmodin <kolmodin@gmail.com>
    -- Stability   : unstable
    -- Portability : portable to Hugs and GHC. Requires the FFI and some flexible instances
    --
    -- Typeclass and instances for binary serialization.
    --
    -----------------------------------------------------------------------------

    module Data.Binary.Class (

        -- * The Binary class
          Binary(..)

    #ifdef GENERICS
        -- * Support for generics
        , GBinary(..)
    #endif

        ) where

    import Data.Word

    import Data.Binary.Put
    import Data.Binary.Get

    import Control.Monad
    import Foreign

    import Data.ByteString.Lazy (ByteString)
    import qualified Data.ByteString.Lazy as L

    import Data.Char    (ord)
    import Data.List    (unfoldr)

    -- And needed for the instances:
    import qualified Data.ByteString as B
    import qualified Data.Map        as Map
    import qualified Data.Set        as Set
    import qualified Data.IntMap     as IntMap
    import qualified Data.IntSet     as IntSet
    import qualified Data.Ratio      as R

    import qualified Data.Tree as T

    import Data.Array.Unboxed

    #ifdef GENERICS
    import GHC.Generics
    #endif

    #ifdef HAS_NATURAL
    import Numeric.Natural
    #endif
    --
    -- This isn't available in older Hugs or older GHC
    --
    #if __GLASGOW_HASKELL__ >= 606
    import qualified Data.Sequence as Seq
    import qualified Data.Foldable as Fold
    #endif

    ------------------------------------------------------------------------

    #ifdef GENERICS
    class GBinary f where
        gput :: f t -> Put
        gget :: Get (f t)
    #endif

    -- | The 'Binary' class provides 'put' and 'get', methods to encode and
    -- decode a Haskell value to a lazy 'ByteString'. It mirrors the 'Read' and
    -- 'Show' classes for textual representation of Haskell types, and is
    -- suitable for serialising Haskell values to disk, over the network.
    --
    -- For decoding and generating simple external binary formats (e.g. C
    -- structures), Binary may be used, but in general is not suitable
    -- for complex protocols. Instead use the 'Put' and 'Get' primitives
    -- directly.
    --
    -- Instances of Binary should satisfy the following property:
    --
    -- > decode . encode == id
    --
    -- That is, the 'get' and 'put' methods should be the inverse of each
    -- other. A range of instances are provided for basic Haskell types.
    --
    class Binary t where
        -- | Encode a value in the Put monad.
        put :: t -> Put
        -- | Decode a value in the Get monad
        get :: Get t

    #ifdef GENERICS
        default put :: (Generic t, GBinary (Rep t)) => t -> Put
        put = gput . from

        default get :: (Generic t, GBinary (Rep t)) => Get t
        get = to `fmap` gget
    #endif

    ------------------------------------------------------------------------
    -- Simple instances

    -- The () type need never be written to disk: values of singleton type
    -- can be reconstructed from the type alone
    instance Binary () where
        put ()  = return ()
        get     = return ()

    -- Bools are encoded as a byte in the range 0 .. 1
    instance Binary Bool where
        put     = putWord8 . fromIntegral . fromEnum
        get     = liftM (toEnum . fromIntegral) getWord8

    -- Values of type 'Ordering' are encoded as a byte in the range 0 .. 2
    instance Binary Ordering where
        put     = putWord8 . fromIntegral . fromEnum
        get     = liftM (toEnum . fromIntegral) getWord8

    ------------------------------------------------------------------------
    -- Words and Ints

    -- Words8s are written as bytes
    instance Binary Word8 where
        put     = putWord8
        get     = getWord8

    -- Words16s are written as 2 bytes in big-endian (network) order
    instance Binary Word16 where
        put     = putWord16be
        get     = getWord16be

    -- Words32s are written as 4 bytes in big-endian (network) order
    instance Binary Word32 where
        put     = putWord32be
        get     = getWord32be

    -- Words64s are written as 8 bytes in big-endian (network) order
    instance Binary Word64 where
        put     = putWord64be
        get     = getWord64be

    -- Int8s are written as a single byte.
    instance Binary Int8 where
        put i   = put (fromIntegral i :: Word8)
        get     = liftM fromIntegral (get :: Get Word8)

    -- Int16s are written as a 2 bytes in big endian format
    instance Binary Int16 where
        put i   = put (fromIntegral i :: Word16)
        get     = liftM fromIntegral (get :: Get Word16)

    -- Int32s are written as a 4 bytes in big endian format
    instance Binary Int32 where
        put i   = put (fromIntegral i :: Word32)
        get     = liftM fromIntegral (get :: Get Word32)

    -- Int64s are written as a 8 bytes in big endian format
    instance Binary Int64 where
        put i   = put (fromIntegral i :: Word64)
        get     = liftM fromIntegral (get :: Get Word64)

    ------------------------------------------------------------------------

    -- Words are are written as Word64s, that is, 8 bytes in big endian format
    instance Binary Word where
        put i   = put (fromIntegral i :: Word64)
        get     = liftM fromIntegral (get :: Get Word64)

    -- Ints are are written as Int64s, that is, 8 bytes in big endian format
    instance Binary Int where
        put i   = put (fromIntegral i :: Int64)
        get     = liftM fromIntegral (get :: Get Int64)

    ------------------------------------------------------------------------
    --
    -- Portable, and pretty efficient, serialisation of Integer
    --

    -- Fixed-size type for a subset of Integer
    type SmallInt = Int32

    -- Integers are encoded in two ways: if they fit inside a SmallInt,
    -- they're written as a byte tag, and that value.  If the Integer value
    -- is too large to fit in a SmallInt, it is written as a byte array,
    -- along with a sign and length field.

    instance Binary Integer where

        {-# INLINE put #-}
        put n | n >= lo && n <= hi = do
            putWord8 0
            put (fromIntegral n :: SmallInt)  -- fast path
         where
            lo = fromIntegral (minBound :: SmallInt) :: Integer
            hi = fromIntegral (maxBound :: SmallInt) :: Integer

        put n = do
            putWord8 1
            put sign
            put (unroll (abs n))         -- unroll the bytes
         where
            sign = fromIntegral (signum n) :: Word8

        {-# INLINE get #-}
        get = do
            tag <- get :: Get Word8
            case tag of
                0 -> liftM fromIntegral (get :: Get SmallInt)
                _ -> do sign  <- get
                        bytes <- get
                        let v = roll bytes
                        return $! if sign == (1 :: Word8) then v else - v

    --
    -- Fold and unfold an Integer to and from a list of its bytes
    --
    unroll :: (Integral a, Num a, Bits a) => a -> [Word8]
    unroll = unfoldr step
      where
        step 0 = Nothing
        step i = Just (fromIntegral i, i `shiftR` 8)

    roll :: (Integral a, Num a, Bits a) => [Word8] -> a
    roll   = foldr unstep 0
      where
        unstep b a = a `shiftL` 8 .|. fromIntegral b

    #ifdef HAS_NATURAL
    -- Fixed-size type for a subset of Natural
    type NaturalWord = Word64

    instance Binary Natural where
        {-# INLINE put #-}
        put n | n <= hi = do
            putWord8 0
            put (fromIntegral n :: NaturalWord)  -- fast path
         where
            hi = fromIntegral (maxBound :: NaturalWord) :: Natural

        put n = do
            putWord8 1
            put (unroll (abs n))         -- unroll the bytes

        {-# INLINE get #-}
        get = do
            tag <- get :: Get Word8
            case tag of
                0 -> liftM fromIntegral (get :: Get NaturalWord)
                _ -> do bytes <- get
                        return $! roll bytes
    #endif

    {-

    --
    -- An efficient, raw serialisation for Integer (GHC only)
    --

    -- TODO  This instance is not architecture portable.  GMP stores numbers as
    -- arrays of machine sized words, so the byte format is not portable across
    -- architectures with different endianness and word size.

    import Data.ByteString.Base (toForeignPtr,unsafePackAddress, memcpy)
    import GHC.Base     hiding (ord, chr)
    import GHC.Prim
    import GHC.Ptr (Ptr(..))
    import GHC.IOBase (IO(..))

    instance Binary Integer where
        put (S# i)    = putWord8 0 >> put (I# i)
        put (J# s ba) = do
            putWord8 1
            put (I# s)
            put (BA ba)

        get = do
            b <- getWord8
            case b of
                0 -> do (I# i#) <- get
                        return (S# i#)
                _ -> do (I# s#) <- get
                        (BA a#) <- get
                        return (J# s# a#)

    instance Binary ByteArray where

        -- Pretty safe.
        put (BA ba) =
            let sz   = sizeofByteArray# ba   -- (primitive) in *bytes*
                addr = byteArrayContents# ba
                bs   = unsafePackAddress (I# sz) addr
            in put bs   -- write as a ByteString. easy, yay!

        -- Pretty scary. Should be quick though
        get = do
            (fp, off, n@(I# sz)) <- liftM toForeignPtr get      -- so decode a ByteString
            assert (off == 0) $ return $ unsafePerformIO $ do
                (MBA arr) <- newByteArray sz                    -- and copy it into a ByteArray#
                let to = byteArrayContents# (unsafeCoerce# arr) -- urk, is this safe?
                withForeignPtr fp $ \from -> memcpy (Ptr to) from (fromIntegral n)
                freezeByteArray arr

    -- wrapper for ByteArray#
    data ByteArray = BA  {-# UNPACK #-} !ByteArray#
    data MBA       = MBA {-# UNPACK #-} !(MutableByteArray# RealWorld)

    newByteArray :: Int# -> IO MBA
    newByteArray sz = IO $ \s ->
      case newPinnedByteArray# sz s of { (# s', arr #) ->
      (# s', MBA arr #) }

    freezeByteArray :: MutableByteArray# RealWorld -> IO ByteArray
    freezeByteArray arr = IO $ \s ->
      case unsafeFreezeByteArray# arr s of { (# s', arr' #) ->
      (# s', BA arr' #) }

    -}

    instance (Binary a,Integral a) => Binary (R.Ratio a) where
        put r = put (R.numerator r) >> put (R.denominator r)
        get = liftM2 (R.%) get get

    ------------------------------------------------------------------------

    -- Char is serialised as UTF-8
    instance Binary Char where
        put a | c <= 0x7f     = put (fromIntegral c :: Word8)
              | c <= 0x7ff    = do put (0xc0 .|. y)
                                   put (0x80 .|. z)
              | c <= 0xffff   = do put (0xe0 .|. x)
                                   put (0x80 .|. y)
                                   put (0x80 .|. z)
              | c <= 0x10ffff = do put (0xf0 .|. w)
                                   put (0x80 .|. x)
                                   put (0x80 .|. y)
                                   put (0x80 .|. z)
              | otherwise     = error "Not a valid Unicode code point"
         where
            c = ord a
            z, y, x, w :: Word8
            z = fromIntegral (c           .&. 0x3f)
            y = fromIntegral (shiftR c 6  .&. 0x3f)
            x = fromIntegral (shiftR c 12 .&. 0x3f)
            w = fromIntegral (shiftR c 18 .&. 0x7)

        get = do
            let getByte = liftM (fromIntegral :: Word8 -> Int) get
                shiftL6 = flip shiftL 6 :: Int -> Int
            w <- getByte
            r <- case () of
                    _ | w < 0x80  -> return w
                      | w < 0xe0  -> do
                                        x <- liftM (xor 0x80) getByte
                                        return (x .|. shiftL6 (xor 0xc0 w))
                      | w < 0xf0  -> do
                                        x <- liftM (xor 0x80) getByte
                                        y <- liftM (xor 0x80) getByte
                                        return (y .|. shiftL6 (x .|. shiftL6
                                                (xor 0xe0 w)))
                      | otherwise -> do
                                    x <- liftM (xor 0x80) getByte
                                    y <- liftM (xor 0x80) getByte
                                    z <- liftM (xor 0x80) getByte
                                    return (z .|. shiftL6 (y .|. shiftL6
                                            (x .|. shiftL6 (xor 0xf0 w))))
            getChr r
          where
            getChr w
              | w <= 0x10ffff = return $! toEnum $ fromEnum w
              | otherwise = fail "Not a valid Unicode code point!"

    ------------------------------------------------------------------------
    -- Instances for the first few tuples

    instance (Binary a, Binary b) => Binary (a,b) where
        put (a,b)           = put a >> put b
        get                 = liftM2 (,) get get

    instance (Binary a, Binary b, Binary c) => Binary (a,b,c) where
        put (a,b,c)         = put a >> put b >> put c
        get                 = liftM3 (,,) get get get

    instance (Binary a, Binary b, Binary c, Binary d) => Binary (a,b,c,d) where
        put (a,b,c,d)       = put a >> put b >> put c >> put d
        get                 = liftM4 (,,,) get get get get

    instance (Binary a, Binary b, Binary c, Binary d, Binary e) => Binary (a,b,c,d,e) where
        put (a,b,c,d,e)     = put a >> put b >> put c >> put d >> put e
        get                 = liftM5 (,,,,) get get get get get

    --
    -- and now just recurse:
    --

    instance (Binary a, Binary b, Binary c, Binary d, Binary e, Binary f)
            => Binary (a,b,c,d,e,f) where
        put (a,b,c,d,e,f)   = put (a,(b,c,d,e,f))
        get                 = do (a,(b,c,d,e,f)) <- get ; return (a,b,c,d,e,f)

    instance (Binary a, Binary b, Binary c, Binary d, Binary e, Binary f, Binary g)
            => Binary (a,b,c,d,e,f,g) where
        put (a,b,c,d,e,f,g) = put (a,(b,c,d,e,f,g))
        get                 = do (a,(b,c,d,e,f,g)) <- get ; return (a,b,c,d,e,f,g)

    instance (Binary a, Binary b, Binary c, Binary d, Binary e,
              Binary f, Binary g, Binary h)
            => Binary (a,b,c,d,e,f,g,h) where
        put (a,b,c,d,e,f,g,h) = put (a,(b,c,d,e,f,g,h))
        get                   = do (a,(b,c,d,e,f,g,h)) <- get ; return (a,b,c,d,e,f,g,h)

    instance (Binary a, Binary b, Binary c, Binary d, Binary e,
              Binary f, Binary g, Binary h, Binary i)
            => Binary (a,b,c,d,e,f,g,h,i) where
        put (a,b,c,d,e,f,g,h,i) = put (a,(b,c,d,e,f,g,h,i))
        get                     = do (a,(b,c,d,e,f,g,h,i)) <- get ; return (a,b,c,d,e,f,g,h,i)

    instance (Binary a, Binary b, Binary c, Binary d, Binary e,
              Binary f, Binary g, Binary h, Binary i, Binary j)
            => Binary (a,b,c,d,e,f,g,h,i,j) where
        put (a,b,c,d,e,f,g,h,i,j) = put (a,(b,c,d,e,f,g,h,i,j))
        get                       = do (a,(b,c,d,e,f,g,h,i,j)) <- get ; return (a,b,c,d,e,f,g,h,i,j)

    ------------------------------------------------------------------------
    -- Container types

    instance Binary a => Binary [a] where
        put l  = put (length l) >> mapM_ put l
        get    = do n <- get :: Get Int
                    getMany n

    -- | 'getMany n' get 'n' elements in order, without blowing the stack.
    getMany :: Binary a => Int -> Get [a]
    getMany n = go [] n
     where
        go xs 0 = return $! reverse xs
        go xs i = do x <- get
                     -- we must seq x to avoid stack overflows due to laziness in
                     -- (>>=)
                     x `seq` go (x:xs) (i-1)
    {-# INLINE getMany #-}

    instance (Binary a) => Binary (Maybe a) where
        put Nothing  = putWord8 0
        put (Just x) = putWord8 1 >> put x
        get = do
            w <- getWord8
            case w of
                0 -> return Nothing
                _ -> liftM Just get

    instance (Binary a, Binary b) => Binary (Either a b) where
        put (Left  a) = putWord8 0 >> put a
        put (Right b) = putWord8 1 >> put b
        get = do
            w <- getWord8
            case w of
                0 -> liftM Left  get
                _ -> liftM Right get

    ------------------------------------------------------------------------
    -- ByteStrings (have specially efficient instances)

    instance Binary B.ByteString where
        put bs = do put (B.length bs)
                    putByteString bs
        get    = get >>= getByteString

    --
    -- Using old versions of fps, this is a type synonym, and non portable
    --
    -- Requires 'flexible instances'
    --
    instance Binary ByteString where
        put bs = do put (fromIntegral (L.length bs) :: Int)
                    putLazyByteString bs
        get    = get >>= getLazyByteString

    ------------------------------------------------------------------------
    -- Maps and Sets

    instance (Binary a) => Binary (Set.Set a) where
        put s = put (Set.size s) >> mapM_ put (Set.toAscList s)
        get   = liftM Set.fromDistinctAscList get

    instance (Binary k, Binary e) => Binary (Map.Map k e) where
        put m = put (Map.size m) >> mapM_ put (Map.toAscList m)
        get   = liftM Map.fromDistinctAscList get

    instance Binary IntSet.IntSet where
        put s = put (IntSet.size s) >> mapM_ put (IntSet.toAscList s)
        get   = liftM IntSet.fromDistinctAscList get

    instance (Binary e) => Binary (IntMap.IntMap e) where
        put m = put (IntMap.size m) >> mapM_ put (IntMap.toAscList m)
        get   = liftM IntMap.fromDistinctAscList get

    ------------------------------------------------------------------------
    -- Queues and Sequences

    #if __GLASGOW_HASKELL__ >= 606
    --
    -- This is valid Hugs, but you need the most recent Hugs
    --

    instance (Binary e) => Binary (Seq.Seq e) where
        put s = put (Seq.length s) >> Fold.mapM_ put s
        get = do n <- get :: Get Int
                 rep Seq.empty n get
          where rep xs 0 _ = return $! xs
                rep xs n g = xs `seq` n `seq` do
                               x <- g
                               rep (xs Seq.|> x) (n-1) g

    #endif

    ------------------------------------------------------------------------
    -- Floating point

    instance Binary Double where
        put d = put (decodeFloat d)
        get   = do
            x <- get
            y <- get
            return $! encodeFloat x y

    instance Binary Float where
        put f = put (decodeFloat f)
        get   =  do
            x <- get
            y <- get
            return $! encodeFloat x y

    ------------------------------------------------------------------------
    -- Trees

    instance (Binary e) => Binary (T.Tree e) where
        put (T.Node r s) = put r >> put s
        get = liftM2 T.Node get get

    ------------------------------------------------------------------------
    -- Arrays

    instance (Binary i, Ix i, Binary e) => Binary (Array i e) where
        put a = do
            put (bounds a)
            put (rangeSize $ bounds a) -- write the length
            mapM_ put (elems a)        -- now the elems.
        get = do
            bs <- get
            n  <- get                  -- read the length
            xs <- getMany n            -- now the elems.
            return (listArray bs xs)

    --
    -- The IArray UArray e constraint is non portable. Requires flexible instances
    --
    instance (Binary i, Ix i, Binary e, IArray UArray e) => Binary (UArray i e) where
        put a = do
            put (bounds a)
            put (rangeSize $ bounds a) -- now write the length
            mapM_ put (elems a)
        get = do
            bs <- get
            n  <- get
            xs <- getMany n
            return (listArray bs xs)