    {-# LANGUAGE DeriveDataTypeable, CPP, BangPatterns, RankNTypes,
                 ForeignFunctionInterface, MagicHash, UnboxedTuples,
                 UnliftedFFITypes #-}
    {-# OPTIONS_GHC -fno-warn-name-shadowing #-}
    #if __GLASGOW_HASKELL__ >= 703
    {-# LANGUAGE Unsafe #-}
    #endif
    {-# OPTIONS_HADDOCK hide #-}

    -- |
    -- Module      : Data.ByteString.Short.Internal
    -- Copyright   : (c) Duncan Coutts 2012-2013
    -- License     : BSD-style
    --
    -- Maintainer  : duncan@community.haskell.org
    -- Stability   : stable
    -- Portability : ghc only
    --
    -- Internal representation of ShortByteString
    --
    module Data.ByteString.Short.Internal (

        -- * The @ShortByteString@ type and representation
        ShortByteString(..),

        -- * Conversions
        toShort,
        fromShort,
        pack,
        unpack,

        -- * Other operations
        empty, null, length, index, unsafeIndex,

        -- * Low level operations
        createFromPtr, copyToPtr
      ) where

    import Data.ByteString.Internal (ByteString(..), accursedUnutterablePerformIO)

    import Data.Typeable    (Typeable)
    import Data.Data        (Data(..), mkNoRepType)
    import Data.Monoid      (Monoid(..))
    import Data.String      (IsString(..))
    import Control.DeepSeq  (NFData(..))
    import qualified Data.List as List (length)
    #if MIN_VERSION_base(4,7,0)
    import Foreign.C.Types  (CSize(..), CInt(..))
    #elif MIN_VERSION_base(4,4,0)
    import Foreign.C.Types  (CSize(..), CInt(..), CLong(..))
    #else
    import Foreign.C.Types  (CSize, CInt, CLong)
    #endif
    import Foreign.Ptr
    import Foreign.ForeignPtr (touchForeignPtr)
    #if MIN_VERSION_base(4,5,0)
    import Foreign.ForeignPtr.Unsafe (unsafeForeignPtrToPtr)
    #else
    import Foreign.ForeignPtr (unsafeForeignPtrToPtr)
    #endif

    #if MIN_VERSION_base(4,5,0)
    import qualified GHC.Exts
    #endif
    import GHC.Exts ( Int(I#), Int#, Ptr(Ptr), Addr#, Char(C#)
                    , State#, RealWorld
                    , ByteArray#, MutableByteArray#
                    , newByteArray#
    #if MIN_VERSION_base(4,6,0)
                    , newPinnedByteArray#
                    , byteArrayContents#
                    , unsafeCoerce#
    #endif
    #if MIN_VERSION_base(4,3,0)
                    , sizeofByteArray#
    #endif
                    , indexWord8Array#, indexCharArray#
                    , writeWord8Array#, writeCharArray#
                    , unsafeFreezeByteArray# )
    import GHC.IO
    #if MIN_VERSION_base(4,6,0)
    import GHC.ForeignPtr (ForeignPtr(ForeignPtr), ForeignPtrContents(PlainPtr))
    #else
    import GHC.ForeignPtr (mallocPlainForeignPtrBytes)
    #endif
    import GHC.ST         (ST(ST), runST)
    import GHC.Word

    import Prelude ( Eq(..), Ord(..), Ordering(..), Read(..), Show(..)
                   , ($), error, (++)
                   , Bool(..), (&&), otherwise
                   , (+), (-), fromIntegral
                   , return )

    -- | A compact representation of a 'Word8' vector.
    --
    -- It has a lower memory overhead than a 'ByteString' and and does not
    -- contribute to heap fragmentation. It can be converted to or from a
    -- 'ByteString' (at the cost of copying the string data). It supports very few
    -- other operations.
    --
    -- It is suitable for use as an internal representation for code that needs
    -- to keep many short strings in memory, but it /should not/ be used as an
    -- interchange type. That is, it should not generally be used in public APIs.
    -- The 'ByteString' type is usually more suitable for use in interfaces; it is
    -- more flexible and it supports a wide range of operations.
    --
    data ShortByteString = SBS ByteArray#
    #if !(MIN_VERSION_base(4,3,0))
               {-# UNPACK #-} !Int  -- ^ Prior to ghc-7.0.x, 'ByteArray#'s reported
                                    -- their length rounded up to the nearest word.
                                    -- This means we have to store the true length
                                    -- separately, wasting a word.
    #define LEN(x) (x)
    #else
    #define _len   /* empty */
    #define LEN(x) /* empty */
    #endif
        deriving Typeable

    -- The ByteArray# representation is always word sized and aligned but with a
    -- known byte length. Our representation choice for ShortByteString is to leave
    -- the 0--3 trailing bytes undefined. This means we can use word-sized writes,
    -- but we have to be careful with reads, see equateBytes and compareBytes below.

    instance Eq ShortByteString where
        (==)    = equateBytes

    instance Ord ShortByteString where
        compare = compareBytes

    instance Monoid ShortByteString where
        mempty  = empty
        mappend = append
        mconcat = concat

    instance NFData ShortByteString where
        rnf (SBS {}) = ()

    instance Show ShortByteString where
        showsPrec p ps r = showsPrec p (unpackChars ps) r

    instance Read ShortByteString where
        readsPrec p str = [ (packChars x, y) | (x, y) <- readsPrec p str ]

    instance IsString ShortByteString where
        fromString = packChars

    instance Data ShortByteString where
      gfoldl f z txt = z packBytes `f` (unpackBytes txt)
      toConstr _     = error "Data.ByteString.Short.ShortByteString.toConstr"
      gunfold _ _    = error "Data.ByteString.Short.ShortByteString.gunfold"
    #if MIN_VERSION_base(4,2,0)
      dataTypeOf _   = mkNoRepType "Data.ByteString.Short.ShortByteString"
    #else
      dataTypeOf _   = mkNorepType "Data.ByteString.Short.ShortByteString"
    #endif

    ------------------------------------------------------------------------
    -- Simple operations

    -- | /O(1)/. The empty 'ShortByteString'.
    empty :: ShortByteString
    empty = create 0 (\_ -> return ())

    -- | /O(1)/ The length of a 'ShortByteString'.
    length :: ShortByteString -> Int
    #if MIN_VERSION_base(4,3,0)
    length (SBS barr#) = I# (sizeofByteArray# barr#)
    #else
    length (SBS _ len) = len
    #endif

    -- | /O(1)/ Test whether a 'ShortByteString' is empty.
    null :: ShortByteString -> Bool
    null sbs = length sbs == 0

    -- | /O(1)/ 'ShortByteString' index (subscript) operator, starting from 0.
    index :: ShortByteString -> Int -> Word8
    index sbs i
      | i >= 0 && i < length sbs = unsafeIndex sbs i
      | otherwise                = indexError sbs i

    unsafeIndex :: ShortByteString -> Int -> Word8
    unsafeIndex sbs = indexWord8Array (asBA sbs)

    indexError :: ShortByteString -> Int -> a
    indexError sbs i =
      error $ "Data.ByteString.Short.index: error in array index; " ++ show i
           ++ " not in range [0.." ++ show (length sbs) ++ ")"

    ------------------------------------------------------------------------
    -- Internal utils

    asBA :: ShortByteString -> BA
    asBA (SBS ba# _len) = BA# ba#

    create :: Int -> (forall s. MBA s -> ST s ()) -> ShortByteString
    create len fill =
        runST (do
          mba <- newByteArray len
          fill mba
          BA# ba# <- unsafeFreezeByteArray mba
          return (SBS ba# LEN(len)))
    {-# INLINE create #-}

    ------------------------------------------------------------------------
    -- Conversion to and from ByteString

    -- | /O(n)/. Convert a 'ByteString' into a 'ShortByteString'.
    --
    -- This makes a copy, so does not retain the input string.
    --
    toShort :: ByteString -> ShortByteString
    toShort !bs = unsafeDupablePerformIO (toShortIO bs)

    toShortIO :: ByteString -> IO ShortByteString
    toShortIO (PS fptr off len) = do
        mba <- stToIO (newByteArray len)
        let ptr = unsafeForeignPtrToPtr fptr
        stToIO (copyAddrToByteArray (ptr `plusPtr` off) mba 0 len)
        touchForeignPtr fptr
        BA# ba# <- stToIO (unsafeFreezeByteArray mba)
        return (SBS ba# LEN(len))

    -- | /O(n)/. Convert a 'ShortByteString' into a 'ByteString'.
    --
    fromShort :: ShortByteString -> ByteString
    fromShort !sbs = unsafeDupablePerformIO (fromShortIO sbs)

    fromShortIO :: ShortByteString -> IO ByteString
    fromShortIO sbs = do
    #if MIN_VERSION_base(4,6,0)
        let len = length sbs
        mba@(MBA# mba#) <- stToIO (newPinnedByteArray len)
        stToIO (copyByteArray (asBA sbs) 0 mba 0 len)
        let fp = ForeignPtr (byteArrayContents# (unsafeCoerce# mba#))
                            (PlainPtr mba#)
        return (PS fp 0 len)
    #else
        -- Before base 4.6 ForeignPtrContents is not exported from GHC.ForeignPtr
        -- so we cannot get direct access to the mbarr#
        let len = length sbs
        fptr <- mallocPlainForeignPtrBytes len
        let ptr = unsafeForeignPtrToPtr fptr
        stToIO (copyByteArrayToAddr (asBA sbs) 0 ptr len)
        touchForeignPtr fptr
        return (PS fptr 0 len)
    #endif

    ------------------------------------------------------------------------
    -- Packing and unpacking from lists

    -- | /O(n)/. Convert a list into a 'ShortByteString'
    pack :: [Word8] -> ShortByteString
    pack = packBytes

    -- | /O(n)/. Convert a 'ShortByteString' into a list.
    unpack :: ShortByteString -> [Word8]
    unpack = unpackBytes

    packChars :: [Char] -> ShortByteString
    packChars cs = packLenChars (List.length cs) cs

    packBytes :: [Word8] -> ShortByteString
    packBytes cs = packLenBytes (List.length cs) cs

    packLenChars :: Int -> [Char] -> ShortByteString
    packLenChars len cs0 =
        create len (\mba -> go mba 0 cs0)
      where
        go :: MBA s -> Int -> [Char] -> ST s ()
        go !_   !_ []     = return ()
        go !mba !i (c:cs) = do
          writeCharArray mba i c
          go mba (i+1) cs

    packLenBytes :: Int -> [Word8] -> ShortByteString
    packLenBytes len ws0 =
        create len (\mba -> go mba 0 ws0)
      where
        go :: MBA s -> Int -> [Word8] -> ST s ()
        go !_   !_ []     = return ()
        go !mba !i (w:ws) = do
          writeWord8Array mba i w
          go mba (i+1) ws

    -- Unpacking bytestrings into lists effeciently is a tradeoff: on the one hand
    -- we would like to write a tight loop that just blats the list into memory, on
    -- the other hand we want it to be unpacked lazily so we don't end up with a
    -- massive list data structure in memory.
    --
    -- Our strategy is to combine both: we will unpack lazily in reasonable sized
    -- chunks, where each chunk is unpacked strictly.
    --
    -- unpackChars does the lazy loop, while unpackAppendBytes and
    -- unpackAppendChars do the chunks strictly.

    unpackChars :: ShortByteString -> [Char]
    unpackChars bs = unpackAppendCharsLazy bs []

    unpackBytes :: ShortByteString -> [Word8]
    unpackBytes bs = unpackAppendBytesLazy bs []

    -- Why 100 bytes you ask? Because on a 64bit machine the list we allocate
    -- takes just shy of 4k which seems like a reasonable amount.
    -- (5 words per list element, 8 bytes per word, 100 elements = 4000 bytes)

    unpackAppendCharsLazy :: ShortByteString -> [Char] -> [Char]
    unpackAppendCharsLazy sbs cs0 =
        go 0 (length sbs) cs0
      where
        sz = 100

        go off len cs
          | len <= sz = unpackAppendCharsStrict sbs off len cs
          | otherwise = unpackAppendCharsStrict sbs off sz  remainder
                          where remainder = go (off+sz) (len-sz) cs

    unpackAppendBytesLazy :: ShortByteString -> [Word8] -> [Word8]
    unpackAppendBytesLazy sbs ws0 =
        go 0 (length sbs) ws0
      where
        sz = 100

        go off len ws
          | len <= sz = unpackAppendBytesStrict sbs off len ws
          | otherwise = unpackAppendBytesStrict sbs off sz  remainder
                          where remainder = go (off+sz) (len-sz) ws

    -- For these unpack functions, since we're unpacking the whole list strictly we
    -- build up the result list in an accumulator. This means we have to build up
    -- the list starting at the end. So our traversal starts at the end of the
    -- buffer and loops down until we hit the sentinal:

    unpackAppendCharsStrict :: ShortByteString -> Int -> Int -> [Char] -> [Char]
    unpackAppendCharsStrict !sbs off len cs =
        go (off-1) (off-1 + len) cs
      where
        go !sentinal !i !acc
          | i == sentinal = acc
          | otherwise     = let !c = indexCharArray (asBA sbs) i
                            in go sentinal (i-1) (c:acc)

    unpackAppendBytesStrict :: ShortByteString -> Int -> Int -> [Word8] -> [Word8]
    unpackAppendBytesStrict !sbs off len ws =
        go (off-1) (off-1 + len) ws
      where
        go !sentinal !i !acc
          | i == sentinal = acc
          | otherwise     = let !w = indexWord8Array (asBA sbs) i
                             in go sentinal (i-1) (w:acc)

    ------------------------------------------------------------------------
    -- Eq and Ord implementations

    equateBytes :: ShortByteString -> ShortByteString -> Bool
    equateBytes sbs1 sbs2 =
        let !len1 = length sbs1
            !len2 = length sbs2
         in len1 == len2
         && 0 == accursedUnutterablePerformIO
                   (memcmp_ByteArray (asBA sbs1) (asBA sbs2) len1)

    compareBytes :: ShortByteString -> ShortByteString -> Ordering
    compareBytes sbs1 sbs2 =
        let !len1 = length sbs1
            !len2 = length sbs2
            !len  = min len1 len2
         in case accursedUnutterablePerformIO
                   (memcmp_ByteArray (asBA sbs1) (asBA sbs2) len) of
              i | i    < 0    -> LT
                | i    > 0    -> GT
                | len2 > len1 -> LT
                | len2 < len1 -> GT
                | otherwise   -> EQ

    ------------------------------------------------------------------------
    -- Appending and concatenation

    append :: ShortByteString -> ShortByteString -> ShortByteString
    append src1 src2 =
      let !len1 = length src1
          !len2 = length src2
       in create (len1 + len2) $ \dst -> do
            copyByteArray (asBA src1) 0 dst 0    len1
            copyByteArray (asBA src2) 0 dst len1 len2

    concat :: [ShortByteString] -> ShortByteString
    concat sbss =
        create (totalLen 0 sbss) (\dst -> copy dst 0 sbss)
      where
        totalLen !acc []          = acc
        totalLen !acc (sbs: sbss) = totalLen (acc + length sbs) sbss

        copy :: MBA s -> Int -> [ShortByteString] -> ST s ()
        copy !_   !_   []                           = return ()
        copy !dst !off (src : sbss) = do
          let !len = length src
          copyByteArray (asBA src) 0 dst off len
          copy dst (off + len) sbss

    ------------------------------------------------------------------------
    -- Exported low level operations

    copyToPtr :: ShortByteString  -- ^ source data
              -> Int              -- ^ offset into source
              -> Ptr a            -- ^ destination
              -> Int              -- ^ number of bytes to copy
              -> IO ()
    copyToPtr src off dst len =
        stToIO $
          copyByteArrayToAddr (asBA src) off dst len

    createFromPtr :: Ptr a   -- ^ source data
                  -> Int     -- ^ number of bytes to copy
                  -> IO ShortByteString
    createFromPtr !ptr len =
        stToIO $ do
          mba <- newByteArray len
          copyAddrToByteArray ptr mba 0 len
          BA# ba# <- unsafeFreezeByteArray mba
          return (SBS ba# LEN(len))

    ------------------------------------------------------------------------
    -- Primop wrappers

    data BA    = BA# ByteArray#
    data MBA s = MBA# (MutableByteArray# s)

    indexCharArray :: BA -> Int -> Char
    indexCharArray (BA# ba#) (I# i#) = C# (indexCharArray# ba# i#)

    indexWord8Array :: BA -> Int -> Word8
    indexWord8Array (BA# ba#) (I# i#) = W8# (indexWord8Array# ba# i#)

    newByteArray :: Int -> ST s (MBA s)
    newByteArray (I# len#) =
        ST $ \s -> case newByteArray# len# s of
                     (# s, mba# #) -> (# s, MBA# mba# #)

    #if MIN_VERSION_base(4,6,0)
    newPinnedByteArray :: Int -> ST s (MBA s)
    newPinnedByteArray (I# len#) =
        ST $ \s -> case newPinnedByteArray# len# s of
                     (# s, mba# #) -> (# s, MBA# mba# #)
    #endif

    unsafeFreezeByteArray :: MBA s -> ST s BA
    unsafeFreezeByteArray (MBA# mba#) =
        ST $ \s -> case unsafeFreezeByteArray# mba# s of
                     (# s, ba# #) -> (# s, BA# ba# #)

    writeCharArray :: MBA s -> Int -> Char -> ST s ()
    writeCharArray (MBA# mba#) (I# i#) (C# c#) =
      ST $ \s -> case writeCharArray# mba# i# c# s of
                   s -> (# s, () #)

    writeWord8Array :: MBA s -> Int -> Word8 -> ST s ()
    writeWord8Array (MBA# mba#) (I# i#) (W8# w#) =
      ST $ \s -> case writeWord8Array# mba# i# w# s of
                   s -> (# s, () #)

    copyAddrToByteArray :: Ptr a -> MBA RealWorld -> Int -> Int -> ST RealWorld ()
    copyAddrToByteArray (Ptr src#) (MBA# dst#) (I# dst_off#) (I# len#) =
        ST $ \s -> case copyAddrToByteArray# src# dst# dst_off# len# s of
                     s -> (# s, () #)

    copyByteArrayToAddr :: BA -> Int -> Ptr a -> Int -> ST RealWorld ()
    copyByteArrayToAddr (BA# src#) (I# src_off#) (Ptr dst#) (I# len#) =
        ST $ \s -> case copyByteArrayToAddr# src# src_off# dst# len# s of
                     s -> (# s, () #)

    copyByteArray :: BA -> Int -> MBA s -> Int -> Int -> ST s ()
    copyByteArray (BA# src#) (I# src_off#) (MBA# dst#) (I# dst_off#) (I# len#) =
        ST $ \s -> case copyByteArray# src# src_off# dst# dst_off# len# s of
                     s -> (# s, () #)

    ------------------------------------------------------------------------
    -- FFI imports

    memcmp_ByteArray :: BA -> BA -> Int -> IO CInt
    memcmp_ByteArray (BA# ba1#) (BA# ba2#) len =
      c_memcmp_ByteArray ba1# ba2# (fromIntegral len)

    foreign import ccall unsafe "string.h memcmp"
      c_memcmp_ByteArray :: ByteArray# -> ByteArray# -> CSize -> IO CInt

    ------------------------------------------------------------------------
    -- Primop replacements

    copyAddrToByteArray# :: Addr#
                         -> MutableByteArray# RealWorld -> Int#
                         -> Int#
                         -> State# RealWorld -> State# RealWorld

    copyByteArrayToAddr# :: ByteArray# -> Int#
                         -> Addr#
                         -> Int#
                         -> State# RealWorld -> State# RealWorld

    copyByteArray#       :: ByteArray# -> Int#
                         -> MutableByteArray# s -> Int#
                         -> Int#
                         -> State# s -> State# s

    #if MIN_VERSION_base(4,7,0)

    -- These exist as real primops in ghc-7.8, and for before that we use
    -- FFI to C memcpy.
    copyAddrToByteArray# = GHC.Exts.copyAddrToByteArray#
    copyByteArrayToAddr# = GHC.Exts.copyByteArrayToAddr#

    #else

    copyAddrToByteArray# src dst dst_off len s =
      unIO_ (memcpy_AddrToByteArray dst (clong dst_off) src 0 (csize len)) s

    copyAddrToByteArray0 :: Addr# -> MutableByteArray# s -> Int#
                         -> State# RealWorld -> State# RealWorld
    copyAddrToByteArray0 src dst len s =
      unIO_ (memcpy_AddrToByteArray0 dst src (csize len)) s

    {-# INLINE [0] copyAddrToByteArray# #-}
    {-# RULES "copyAddrToByteArray# dst_off=0"
          forall src dst len s.
              copyAddrToByteArray# src dst 0# len s
            = copyAddrToByteArray0 src dst    len s  #-}

    foreign import ccall unsafe "fpstring.h fps_memcpy_offsets"
      memcpy_AddrToByteArray :: MutableByteArray# s -> CLong -> Addr# -> CLong -> CSize -> IO ()

    foreign import ccall unsafe "string.h memcpy"
      memcpy_AddrToByteArray0 :: MutableByteArray# s -> Addr# -> CSize -> IO ()

    copyByteArrayToAddr# src src_off dst len s =
      unIO_ (memcpy_ByteArrayToAddr dst 0 src (clong src_off) (csize len)) s

    copyByteArrayToAddr0 :: ByteArray# -> Addr# -> Int#
                         -> State# RealWorld -> State# RealWorld
    copyByteArrayToAddr0 src dst len s =
      unIO_ (memcpy_ByteArrayToAddr0 dst src (csize len)) s

    {-# INLINE [0] copyByteArrayToAddr# #-}
    {-# RULES "copyByteArrayToAddr# src_off=0"
          forall src dst len s.
              copyByteArrayToAddr# src 0# dst len s
            = copyByteArrayToAddr0 src    dst len s  #-}

    foreign import ccall unsafe "fpstring.h fps_memcpy_offsets"
      memcpy_ByteArrayToAddr :: Addr# -> CLong -> ByteArray# -> CLong -> CSize -> IO ()

    foreign import ccall unsafe "string.h memcpy"
      memcpy_ByteArrayToAddr0 :: Addr# -> ByteArray# -> CSize -> IO ()

    unIO_ :: IO () -> State# RealWorld -> State# RealWorld
    unIO_ io s = case unIO io s of (# s, _ #) -> s

    clong :: Int# -> CLong
    clong i# = fromIntegral (I# i#)

    csize :: Int# -> CSize
    csize i# = fromIntegral (I# i#)
    #endif

    #if MIN_VERSION_base(4,5,0)
    copyByteArray# = GHC.Exts.copyByteArray#
    #else
    copyByteArray# src src_off dst dst_off len s =
        unST_ (unsafeIOToST
          (memcpy_ByteArray dst (clong dst_off) src (clong src_off) (csize len))) s
      where
        unST (ST st) = st
        unST_ st s = case unST st s of (# s, _ #) -> s

    foreign import ccall unsafe "fpstring.h fps_memcpy_offsets"
      memcpy_ByteArray :: MutableByteArray# s -> CLong
                       -> ByteArray# -> CLong -> CSize -> IO ()
    #endif