@@ -4,6 +4,7 @@
5-- Module : Data.Binary.Bits.Get
5-- Module : Data.Binary.Bits.Get
6-- Copyright : (c) Lennart Kolmodin 2010-2011
6-- Copyright : (c) Lennart Kolmodin 2010-2011
7+-- (c) Sylvain Henry 2015
7-- License : BSD3-style (see LICENSE)
8-- License : BSD3-style (see LICENSE)
9-- Maintainer : kolmodin@gmail.com
10-- Maintainer : kolmodin@gmail.com
@@ -59,11 +60,19 @@ module Data.Binary.Bits.Get
60 -- ** Get bytes
61 -- ** Get bytes
62 , getWord8
64 , getWord8
63 , getWord16be
68 , getWord16be
64 , getWord32be
69 , getWord32be
65 , getWord64be
70 , getWord64be
67 -- * Blocks
76 -- * Blocks
69 -- $blocks
78 -- $blocks
@@ -73,31 +82,41 @@ module Data.Binary.Bits.Get
73 -- ** Read in Blocks
82 -- ** Read in Blocks
76 , word16be
88 , word16be
77 , word32be
89 , word32be
78 , word64be
90 , word64be
79 , byteString
91 , byteString
80 , Data.Binary.Bits.Get.getByteString
92 , Data.Binary.Bits.Get.getByteString
93+ , Data.Binary.Bits.Get.getLazyByteString
94+ , Data.Binary.Bits.Get.isEmpty
84−import Data.Binary.Get as B ( runGet, Get, getByteString )
98+import Data.Binary.Get as B ( Get, getLazyByteString, isEmpty )
99+import Data.Binary.Get.Internal as B ( get, put, ensureN )
100+import Data.Binary.Bits.BitOrder
101+import Data.Binary.Bits.Internal
102+import Data.Binary.Bits.Alignment
86import Data.ByteString as B
104import Data.ByteString as B
105+import qualified Data.ByteString.Lazy as L
87import Data.ByteString.Unsafe
106import Data.ByteString.Unsafe
107+import Foreign.Marshal.Alloc (mallocBytes)
109+import Foreign.Storable (poke)
110+import System.IO.Unsafe (unsafePerformIO)
89import Data.Bits
112import Data.Bits
90import Data.Word
113import Data.Word
92import Control.Applicative
114import Control.Applicative
115+import Control.Monad (when,foldM_)
94import Prelude as P
117import Prelude as P
96−#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
98import GHC.Word
118import GHC.Word
99−#endif
119+import GHC.Base (uncheckedShiftLWord8#, wordToWord8#, Int (..), andWord8#, Word8#, (-#), Int#, xorI#, eqWord8#, TYPE)
102-- $bitget
121-- $bitget
103-- Parse bits using a monad.
122-- Parse bits using a monad.
@@ -145,188 +164,121 @@ import GHC.Word
145--ipv6Header = 'runBitGet' ('block' ipv6headerblock)
164--ipv6Header = 'runBitGet' ('block' ipv6headerblock)
148−data S = S !ByteString -- Input
167+data S = S {-# UNPACK #-} !ByteString -- Input
149− !Int -- Bit offset (0-7)
168+ {-# UNPACK #-} !Int -- Bit offset (0-7)
169+ !BitOrder -- Bit order
150 deriving (Show)
170 deriving (Show)
152−-- | A block that will be read with only one boundry check. Needs to know the
172+-- | Increment the current bit offset
153−-- number of bits in advance.
154−data Block a = Block !Int (S -> a)
156−instance Functor Block where
157− fmap f (Block i p) = Block i (\s -> f (p s))
159−instance Applicative Block where
160− pure a = Block 0 (\_ -> a)
161− (Block i p) <*> (Block j q) = Block (i+j) (\s -> p s $ q (incS i s))
162− (Block i _) *> (Block j q) = Block (i+j) (q . incS i)
163− (Block i p) <* (Block j _) = Block (i+j) p
165−-- | Get a block. Will be read with one single boundry check, and
166−-- therefore requires a statically known number of bits.
167−-- Build blocks using 'bool', 'word8', 'word16be', 'word32be', 'word64be',
168−-- 'byteString' and 'Applicative'.
169−block :: Block a -> BitGet a
170−block (Block i p) = do
172− modifyState (\s -> (incS i s, p s))
175incS :: Int -> S -> S
173incS :: Int -> S -> S
179− !n' = o' .&. make_mask 3
180− in S (unsafeDrop d bs) n'
174+incS o (S bs n bo) = S (unsafeDrop d bs) n' bo
182−-- | make_mask 3 = 00000111
176+ !o' = (n+o)
183−make_mask :: Bits a => Int -> a
184−make_mask n = (1 `shiftL` fromIntegral n) - 1
185−{-# SPECIALIZE make_mask :: Int -> Int #-}
186−{-# SPECIALIZE make_mask :: Int -> Word #-}
187−{-# SPECIALIZE make_mask :: Int -> Word8 #-}
188−{-# SPECIALIZE make_mask :: Int -> Word16 #-}
189−{-# SPECIALIZE make_mask :: Int -> Word32 #-}
190−{-# SPECIALIZE make_mask :: Int -> Word64 #-}
192−bit_offset :: Int -> Int
193−bit_offset n = make_mask 3 .&. n
195−byte_offset :: Int -> Int
177+ !d = byte_offset o'
196−byte_offset n = n `shiftR` 3
178+ !n' = bit_offset o'
180+-- | Read a single bit
198readBool :: S -> Bool
181readBool :: S -> Bool
182+readBool (S bs o bo) = case bo of
183+ BB -> testBit (unsafeHead bs) (7-o)
199−readBool (S bs n) = testBit (unsafeHead bs) (7-n)
184+ BL -> testBit (unsafeHead bs) (7-o)
200−
185+ LL -> testBit (unsafeHead bs) o
201−readWord8 :: Int -> S -> Word8
186+ LB -> testBit (unsafeHead bs) o
202−readWord8 n (S bs o)
187+
203− -- no bits at all, return 0
188+-- | Read a single bit
204− | n == 0 = 0
189+readBool# :: S -> Int
205−
190+readBool# (S bs (I# o) bo) = case bo of
206− -- all bits are in the same byte
191+ BB -> testBit# (7# -# o)
207− -- we just need to shift and mask them right
192+ BL -> testBit# (7# -# o)
208− | n <= 8 - o = let w = unsafeHead bs
193+ LL -> testBit# o
209− m = make_mask n
194+ LB -> testBit# o
210− w' = (w `shiftr_w8` (8 - o - n)) .&. m
195+ where
211− in w'
196+ !(W8# w) = unsafeHead bs
212−
197+ testBit# n = I# (((w `andWord8#` (wordToWord8# 1## `uncheckedShiftLWord8#` n)) `eqWord8#` wordToWord8# 0##) `xorI#` 1#)
213− -- the bits are in two different bytes
198+
214− -- make a word16 using both bytes, and then shift and mask
199+
215− | n <= 8 = let w = (fromIntegral (unsafeHead bs) `shiftl_w16` 8) .|.
200+-- | Extract a range of bits from (ws :: ByteString)
216− (fromIntegral (unsafeIndex bs 1))
201+--
217− m = make_mask n
202+-- Constraint: 8 * (length ws -1 ) < o+n <= 8 * length ws
218− w' = (w `shiftr_w16` (16 - o - n)) .&. m
203+extract :: (Num a, FastBits a) => BitOrder -> ByteString -> Int -> Int -> a
219− in fromIntegral w'
204+extract bo bs o n
221−
206+ | B.length bs == 0 = error "Empty ByteString"
222−readWord16be :: Int -> S -> Word16
207+ | otherwise = rev . mask n . foldlWithIndex' f 0 $ bs
223−readWord16be n s@(S bs o)
208+ where
224−
209+ -- B.foldl' with index
225− -- 8 or fewer bits, use readWord8
210+ foldlWithIndex' op b = fst . B.foldl' g (b,0)
226− | n <= 8 = fromIntegral (readWord8 n s)
211+ where g (b',i) w = (op b' w i, (i+1))
228− -- handle 9 or more bits, stored in two bytes
213+ -- 'or' correctly shifted words
229−
214+ f b w i = b .|. (fromIntegral w `fastShift` off i)
230− -- no offset, plain and simple 16 bytes
215+
231− | o == 0 && n == 16 = let msb = fromIntegral (unsafeHead bs)
216+ -- co-offset
232− lsb = fromIntegral (unsafeIndex bs 1)
217+ r = B.length bs * 8 - (o + n)
233− w = (msb `shiftl_w16` 8) .|. lsb
218+
234− in w
219+ -- shift offset depending on the byte position (0..B.length-1)
235−
220+ off i = case bo of
236− -- no offset, but not full 16 bytes
221+ LL -> 8*i - o
237− | o == 0 = let msb = fromIntegral (unsafeHead bs)
222+ LB -> 8*i - o
238− lsb = fromIntegral (unsafeIndex bs 1)
223+ BB -> (B.length bs -1 - i) * 8 - r
239− w = (msb `shiftl_w16` (n-8)) .|. (lsb `shiftr_w16` (16-n))
224+ BL -> (B.length bs -1 - i) * 8 - r
241−
226+ -- reverse bits if necessary
242− -- with offset, and n=9-16
227+ rev = case bo of
243− | n <= 16 = readWithOffset s shiftl_w16 shiftr_w16 n
228+ LB -> reverseBits n
244−
229+ BL -> reverseBits n
245− | otherwise = error "readWord16be: tried to read more than 16 bits"
230+ BB -> id
247−readWord32be :: Int -> S -> Word32
232+
248−readWord32be n s@(S _ o)
233+
249− -- 8 or fewer bits, use readWord8
234+-- | Generic readWord
250− | n <= 8 = fromIntegral (readWord8 n s)
235+readWord :: (Num a, FastBits a) => Int -> S -> a
251−
236+readWord n (S bs o bo)
252− -- 16 or fewer bits, use readWord16be
237+ | n == 0 = 0
253− | n <= 16 = fromIntegral (readWord16be n s)
238+ | otherwise = extract bo (unsafeTake nbytes bs) o n
254−
239+ where nbytes = byte_offset (o+n+7)
255− | o == 0 = readWithoutOffset s shiftl_w32 shiftr_w32 n
240+
256−
241+-- | Check that the number of bits to read is not greater than the first parameter
257− | n <= 32 = readWithOffset s shiftl_w32 shiftr_w32 n
242+{-# INLINE readWordChecked #-}
258−
243+readWordChecked :: (Num a, FastBits a) => Int -> Int -> S -> a
259− | otherwise = error "readWord32be: tried to read more than 32 bits"
244+readWordChecked m n s
260−
245+ | n > m = error $ "Tried to read more than " ++ show m ++ " bits (" ++ show n ++")"
261−
246+ | otherwise = readWord n s
262−readWord64be :: Int -> S -> Word64
247+
263−readWord64be n s@(S _ o)
248+-- | Read the given number of bytes and return them in Big-Endian order
264− -- 8 or fewer bits, use readWord8
249+--
265− | n <= 8 = fromIntegral (readWord8 n s)
250+-- Examples:
266−
251+-- BB: xxxABCDE FGHIJKLM NOPxxxxx -> ABCDEFGH IJKLMNOP
267− -- 16 or fewer bits, use readWord16be
252+-- LL: LMNOPxxx DEFGHIJK xxxxxABC -> ABCDEFGH IJKLMNOP
268− | n <= 16 = fromIntegral (readWord16be n s)
253+-- BL: xxxPONML KJIHGFED CBAxxxxx -> ABCDEFGH IJKLMNOP
269−
254+-- LB: EDCBAxxx MLKJIHGF xxxxxPON -> ABCDEFGH IJKLMNOP
270− | o == 0 = readWithoutOffset s shiftl_w64 shiftr_w64 n
272− | n <= 64 = readWithOffset s shiftl_w64 shiftr_w64 n
274− | otherwise = error "readWord64be: tried to read more than 64 bits"
277readByteString :: Int -> S -> ByteString
255readByteString :: Int -> S -> ByteString
278−readByteString n s@(S bs o)
256+readByteString n (S bs o bo) =
279− -- no offset, easy.
257+ let
280− | o == 0 = unsafeTake n bs
258+ bs' = unsafeTake (n+1) bs
281− -- offset. ugg. this is really naive and slow. but also pretty easy :)
259+ bs'' = unsafeTake n bs
282− | otherwise = B.pack (P.map (readWord8 8) (P.take n (iterate (incS 8) s)))
260+ rev = B.map (reverseBits 8)
283−
261+ in case (o,bo) of
284−readWithoutOffset :: (Bits a, Num a)
262+ (0,BB) -> bs''
285− => S -> (a -> Int -> a) -> (a -> Int -> a) -> Int -> a
263+ (0,LL) -> B.reverse bs''
286−readWithoutOffset (S bs o) shifterL shifterR n
264+ (0,LB) -> rev bs''
287− | o /= 0 = error "readWithoutOffset: there is an offset"
265+ (0,BL) -> rev . B.reverse $ bs''
288−
266+ (_,LL) -> readByteString n (S (B.reverse bs') (8-o) BB)
289− | bit_offset n == 0 && byte_offset n <= 4 =
267+ (_,BL) -> rev . B.reverse $ readByteString n (S bs' o BB)
290− let segs = byte_offset n
268+ (_,LB) -> rev . B.reverse $ readByteString n (S bs' o LL)
291− bn 0 = fromIntegral (unsafeHead bs)
269+ (_,BB) -> unsafePerformIO $ do
271+ ptr <- mallocBytes len
292− bn n = (bn (n-1) `shifterL` 8) .|. fromIntegral (unsafeIndex bs n)
274+ w = unsafeIndex bs (len-i)
293−
275+ w' = (w `fastShiftL` o) .|. r
294− in bn (segs-1)
276+ r' = w `fastShiftR` (8-o)
277+ poke (ptr `plusPtr` (len-i)) w'
280+ unsafeInit <$> unsafePackMallocCStringLen (ptr,len)
296− | n <= 64 = let segs = byte_offset n
297− o' = bit_offset (n - 8 + o)
299− bn 0 = fromIntegral (unsafeHead bs)
300− bn n = (bn (n-1) `shifterL` 8) .|. fromIntegral (unsafeIndex bs n)
302− msegs = bn (segs-1) `shifterL` o'
304− last = (fromIntegral (unsafeIndex bs segs)) `shifterR` (8 - o')
309−readWithOffset :: (Bits a, Num a)
310− => S -> (a -> Int -> a) -> (a -> Int -> a) -> Int -> a
311−readWithOffset (S bs o) shifterL shifterR n
312− | n <= 64 = let bits_in_msb = 8 - o
313− (n',top) = (n - bits_in_msb
314− , (fromIntegral (unsafeHead bs) .&. make_mask bits_in_msb) `shifterL` n')
316− segs = byte_offset n'
319− bn n = (bn (n-1) `shifterL` 8) .|. fromIntegral (unsafeIndex bs n)
323− mseg = bn segs `shifterL` o'
325− last | o' > 0 = (fromIntegral (unsafeIndex bs (segs + 1))) `shifterR` (8 - o')
328− w = top .|. mseg .|. last
331------------------------------------------------------------------------
283------------------------------------------------------------------------
332-- | 'BitGet' is a monad, applicative and a functor. See 'runBitGet'
284-- | 'BitGet' is a monad, applicative and a functor. See 'runBitGet'
@@ -335,7 +287,6 @@ newtype BitGet a = B { runState :: S -> Get (S,a) }
336instance Monad BitGet where
288instance Monad BitGet where
337 return x = B $ \s -> return (s,x)
289 return x = B $ \s -> return (s,x)
338− fail str = B $ \_s -> fail str
339 (B f) >>= g = B $ \s -> do (s',a) <- f s
290 (B f) >>= g = B $ \s -> do (s',a) <- f s
340 runState (g a) s'
291 runState (g a) s'
@@ -346,123 +297,200 @@ instance Applicative BitGet where
346 pure x = return x
297 pure x = return x
347 fm <*> m = fm >>= \f -> m >>= \v -> return (f v)
298 fm <*> m = fm >>= \f -> m >>= \v -> return (f v)
300+instance BitOrderable BitGet where
302+ (S bs o _) <- getState
303+ putState (S bs o bo)
306+ (S _ _ bo) <- getState
309+instance Alignable BitGet where
310+ -- | Skip the given number of bits
315+ -- | Skip bits if necessary to align to the next byte
317+ (S _ o _) <- getState
349-- | Run a 'BitGet' within the Binary packages 'Get' monad. If a byte has
323-- | Run a 'BitGet' within the Binary packages 'Get' monad. If a byte has
350-- been partially consumed it will be discarded once 'runBitGet' is finished.
324-- been partially consumed it will be discarded once 'runBitGet' is finished.
351runBitGet :: BitGet a -> Get a
325runBitGet :: BitGet a -> Get a
352runBitGet bg = do
326runBitGet bg = do
353− (_,a) <- runState bg (S B.empty 0)
328+ (s',a) <- runState bg s
338+putBackState :: S -> Get ()
339+putBackState (S bs o _) = do
343+ _ -> unsafeDrop 1 bs
344+ put (bs' `B.append` remaining)
356getState :: BitGet S
346getState :: BitGet S
357getState = B $ \s -> return (s,s)
347getState = B $ \s -> return (s,s)
359putState :: S -> BitGet ()
349putState :: S -> BitGet ()
360putState s = B $ \_ -> return (s,())
350putState s = B $ \_ -> return (s,())
362−modifyState :: (S -> (S,a)) -> BitGet a
352+withState :: (S -> S) -> BitGet ()
363−modifyState f = B $ \s -> return (f s)
353+withState f = do
365-- | Make sure there are at least @n@ bits.
357-- | Make sure there are at least @n@ bits.
366ensureBits :: Int -> BitGet ()
358ensureBits :: Int -> BitGet ()
367ensureBits n = do
359ensureBits n = do
368− (S bs o) <- getState
360+ (S bs o bo) <- getState
369 if n <= (B.length bs * 8 - o)
361 if n <= (B.length bs * 8 - o)
370 then return ()
362 then return ()
371 else do let currentBits = B.length bs * 8 - o
363 else do let currentBits = B.length bs * 8 - o
372− let byteCount = (n - currentBits + 7) `div` 8
364+ let byteCount = byte_offset (n - currentBits + 7)
373− B $ \_ -> do bs' <- B.getByteString byteCount
365+ B $ \_ -> do B.ensureN byteCount
374− return (S (bs`append`bs') o, ())
368+ return (S (bs`append`bs') o bo, ())
370+-- | Test whether all input has been consumed, i.e. there are no remaining
372+isEmpty :: BitGet Bool
373+isEmpty = B $ \ (S bs o bo) -> if B.null bs
374+ then B.isEmpty >>= \e -> return (S bs o bo, e)
375+ else return (S bs o bo, False)
376-- | Get 1 bit as a 'Bool'.
377-- | Get 1 bit as a 'Bool'.
377getBool :: BitGet Bool
378getBool :: BitGet Bool
378getBool = block bool
379getBool = block bool
381+-- | Get 1 bit as a 'Bool'.
382+getBool# :: BitGet Int
383+getBool# = block bool#
380-- | Get @n@ bits as a 'Word8'. @n@ must be within @[0..8]@.
385-- | Get @n@ bits as a 'Word8'. @n@ must be within @[0..8]@.
381getWord8 :: Int -> BitGet Word8
386getWord8 :: Int -> BitGet Word8
382getWord8 n = block (word8 n)
387getWord8 n = block (word8 n)
384-- | Get @n@ bits as a 'Word16'. @n@ must be within @[0..16]@.
389-- | Get @n@ bits as a 'Word16'. @n@ must be within @[0..16]@.
390+getWord16 :: Int -> BitGet Word16
391+getWord16 n = block (word16 n)
385getWord16be :: Int -> BitGet Word16
393getWord16be :: Int -> BitGet Word16
386−getWord16be n = block (word16be n)
394+getWord16be = getWord16
395+{-# DEPRECATED getWord16be "Use 'getWord16' instead" #-}
388-- | Get @n@ bits as a 'Word32'. @n@ must be within @[0..32]@.
397-- | Get @n@ bits as a 'Word32'. @n@ must be within @[0..32]@.
398+getWord32 :: Int -> BitGet Word32
399+getWord32 n = block (word32 n)
389getWord32be :: Int -> BitGet Word32
401getWord32be :: Int -> BitGet Word32
390−getWord32be n = block (word32be n)
402+getWord32be = getWord32
403+{-# DEPRECATED getWord32be "Use 'getWord32' instead" #-}
392-- | Get @n@ bits as a 'Word64'. @n@ must be within @[0..64]@.
405-- | Get @n@ bits as a 'Word64'. @n@ must be within @[0..64]@.
406+getWord64 :: Int -> BitGet Word64
407+getWord64 n = block (word64 n)
393getWord64be :: Int -> BitGet Word64
409getWord64be :: Int -> BitGet Word64
394−getWord64be n = block (word64be n)
410+getWord64be = getWord64
411+{-# DEPRECATED getWord64be "Use 'getWord64' instead" #-}
396-- | Get @n@ bytes as a 'ByteString'.
413-- | Get @n@ bytes as a 'ByteString'.
397getByteString :: Int -> BitGet ByteString
414getByteString :: Int -> BitGet ByteString
398getByteString n = block (byteString n)
415getByteString n = block (byteString n)
417+-- | Get @n@ bytes as a lazy ByteString.
418+getLazyByteString :: Int -> BitGet L.ByteString
419+getLazyByteString n = do
420+ (S _ o bo) <- getState
424+ lbs <- B.getLazyByteString (fromIntegral n)
425+ return (S B.empty 0 bo, lbs)
426+ _ -> L.fromChunks . (:[]) <$> Data.Binary.Bits.Get.getByteString n
432+-- | A block that will be read with only one boundary check. Needs to know the
433+-- number of bits in advance.
434+data Block a = Block Int (S -> a)
436+instance Functor Block where
437+ fmap f (Block i p) = Block i (\s -> f (p s))
439+instance Applicative Block where
440+ pure a = Block 0 (\_ -> a)
441+ (Block i p) <*> (Block j q) = Block (i+j) (\s -> p s $ q (incS i s))
442+ (Block i _) *> (Block j q) = Block (i+j) (q . incS i)
443+ (Block i p) <* (Block j _) = Block (i+j) p
445+-- | Get a block. Will be read with one single boundry check, and
446+-- therefore requires a statically known number of bits.
447+-- Build blocks using 'bool', 'word8', 'word16be', 'word32be', 'word64be',
448+-- 'byteString' and 'Applicative'.
449+block :: Block a -> BitGet a
450+block (Block i p) = do
453+ putState $! (incS i s)
400-- | Read a 1 bit 'Bool'.
456-- | Read a 1 bit 'Bool'.
401bool :: Block Bool
457bool :: Block Bool
402bool = Block 1 readBool
458bool = Block 1 readBool
460+-- | Read a 1 bit 'Bool'.
462+bool# = Block 1 readBool#
404-- | Read @n@ bits as a 'Word8'. @n@ must be within @[0..8]@.
464-- | Read @n@ bits as a 'Word8'. @n@ must be within @[0..8]@.
405word8 :: Int -> Block Word8
465word8 :: Int -> Block Word8
406−word8 n = Block n (readWord8 n)
466+word8 n = Block n (readWordChecked 8 n)
408-- | Read @n@ bits as a 'Word16'. @n@ must be within @[0..16]@.
468-- | Read @n@ bits as a 'Word16'. @n@ must be within @[0..16]@.
469+word16 :: Int -> Block Word16
470+word16 n = Block n (readWordChecked 16 n)
409word16be :: Int -> Block Word16
472word16be :: Int -> Block Word16
410−word16be n = Block n (readWord16be n)
473+word16be = word16
474+{-# DEPRECATED word16be "Use 'word16' instead" #-}
412-- | Read @n@ bits as a 'Word32'. @n@ must be within @[0..32]@.
476-- | Read @n@ bits as a 'Word32'. @n@ must be within @[0..32]@.
477+word32 :: Int -> Block Word32
478+word32 n = Block n (readWordChecked 32 n)
413word32be :: Int -> Block Word32
480word32be :: Int -> Block Word32
414−word32be n = Block n (readWord32be n)
481+word32be = word32
482+{-# DEPRECATED word32be "Use 'word32' instead" #-}
416-- | Read @n@ bits as a 'Word64'. @n@ must be within @[0..64]@.
484-- | Read @n@ bits as a 'Word64'. @n@ must be within @[0..64]@.
485+word64 :: Int -> Block Word64
486+word64 n = Block n (readWordChecked 64 n)
417word64be :: Int -> Block Word64
488word64be :: Int -> Block Word64
418−word64be n = Block n (readWord64be n)
489+word64be = word64
490+{-# DEPRECATED word64be "Use 'word64' instead" #-}
420-- | Read @n@ bytes as a 'ByteString'.
492-- | Read @n@ bytes as a 'ByteString'.
421byteString :: Int -> Block ByteString
493byteString :: Int -> Block ByteString
422−byteString n = Block (n*8) (readByteString n)
494+byteString n | n > 0 = Block (n*8) (readByteString n)
495+ | otherwise = Block 0 (\_ -> B.empty)
424−------------------------------------------------------------------------
425−-- Unchecked shifts, from the package binary
427−shiftl_w16 :: Word16 -> Int -> Word16
428−shiftl_w32 :: Word32 -> Int -> Word32
429−shiftl_w64 :: Word64 -> Int -> Word64
431−#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
432−shiftl_w8 (W8# w) (I# i) = W8# (w `uncheckedShiftL#` i)
433−shiftl_w16 (W16# w) (I# i) = W16# (w `uncheckedShiftL#` i)
434−shiftl_w32 (W32# w) (I# i) = W32# (w `uncheckedShiftL#` i)
436−shiftr_w8 (W8# w) (I# i) = W8# (w `uncheckedShiftRL#` i)
437−shiftr_w16 (W16# w) (I# i) = W16# (w `uncheckedShiftRL#` i)
438−shiftr_w32 (W32# w) (I# i) = W32# (w `uncheckedShiftRL#` i)
441−#if WORD_SIZE_IN_BITS < 64
442−shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL64#` i)
443−shiftr_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftRL64#` i)
445−#if __GLASGOW_HASKELL__ <= 606
446−-- Exported by GHC.Word in GHC 6.8 and higher
447−foreign import ccall unsafe "stg_uncheckedShiftL64"
448− uncheckedShiftL64# :: Word64# -> Int# -> Word64#
449−foreign import ccall unsafe "stg_uncheckedShiftRL64"
450− uncheckedShiftRL64# :: Word64# -> Int# -> Word64#
454−shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL#` i)
455−shiftr_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftRL#` i)