content: {-# LANGUAGE FlexibleContexts #-}
  {-# LANGUAGE Trustworthy #-}
  {-# LANGUAGE DefaultSignatures #-}
  -----------------------------------------------------------------------------
  -- |
  -- Module      : Distribution.Compat.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 Distribution.Compat.Binary.Class (
  
      -- * The Binary class
        Binary(..)
  
      -- * Support for generics
      , GBinary(..)
  
      ) 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     (chr,ord)
  import Data.List     (unfoldr)
  import Data.Foldable (traverse_)
  
  -- 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
  
  import GHC.Generics
  
  import qualified Data.Sequence as Seq
  import qualified Data.Foldable as Fold
  
  ------------------------------------------------------------------------
  
  class GBinary f where
      gput :: f t -> Put
      gget :: Get (f t)
  
  -- | 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
  
      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
  
  ------------------------------------------------------------------------
  -- 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 4 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 :: Integer -> [Word8]
  unroll = unfoldr step
    where
      step 0 = Nothing
      step i = Just (fromIntegral i, i `shiftR` 8)
  
  roll :: [Word8] -> Integer
  roll   = foldr unstep 0
    where
      unstep b a = a `shiftL` 8 .|. fromIntegral b
  
  {-
  
  --
  -- 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))))
          return $! chr r
  
  ------------------------------------------------------------------------
  -- 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) >> traverse_ 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) >> traverse_ 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) >> traverse_ put (Map.toAscList m)
      get   = liftM Map.fromDistinctAscList get
  
  instance Binary IntSet.IntSet where
      put s = put (IntSet.size s) >> traverse_ put (IntSet.toAscList s)
      get   = liftM IntSet.fromDistinctAscList get
  
  instance (Binary e) => Binary (IntMap.IntMap e) where
      put m = put (IntMap.size m) >> traverse_ put (IntMap.toAscList m)
      get   = liftM IntMap.fromDistinctAscList get
  
  ------------------------------------------------------------------------
  -- Queues and Sequences
  
  instance (Binary e) => Binary (Seq.Seq e) where
      put s = put (Seq.length s) >> Fold.traverse_ 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
  
  ------------------------------------------------------------------------
  -- Floating point
  
  instance Binary Double where
      put d = put (decodeFloat d)
      get   = liftM2 encodeFloat get get
  
  instance Binary Float where
      put f = put (decodeFloat f)
      get   = liftM2 encodeFloat get get
  
  ------------------------------------------------------------------------
  -- 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
          traverse_ 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
          traverse_ put (elems a)
      get = do
          bs <- get
          n  <- get
          xs <- getMany n
          return (listArray bs xs)
  