@@ -1,72 +1,145 @@
11{-# LANGUAGE RankNTypes, MagicHash, BangPatterns, CPP #-}
22
3+-----------------------------------------------------------------------------
4+-- |
5+-- Module : Data.Binary.Bits.Get
6+-- Copyright : (c) Lennart Kolmodin 2010-2011
7+-- (c) Sylvain Henry 2015
8+-- License : BSD3-style (see LICENSE)
9+--
10+-- Maintainer : kolmodin@gmail.com
11+-- Stability : experimental
12+-- Portability : portable (should run where the package binary runs)
13+--
14+-- Parse bits easily. Parsing can be done either in a monadic style, or more
15+-- efficiently, using the 'Applicative' style.
16+--
17+-- For the monadic style, write your parser as a 'BitGet' monad using the
18+--
19+-- * 'getBool'
20+--
21+-- * 'getWord8'
22+--
23+-- * 'getWord16be'
24+--
25+-- * 'getWord32be'
26+--
27+-- * 'getWord64be'
28+--
29+-- * 'getByteString'
30+--
31+-- functions and run it with 'runBitGet'.
32+--
33+-- For the applicative style, compose the fuctions
34+--
35+-- * 'bool'
36+--
37+-- * 'word8'
38+--
39+-- * 'word16be'
40+--
41+-- * 'word32be'
42+--
43+-- * 'word64be'
44+--
45+-- * 'byteString'
46+--
47+-- to make a 'Block'.
48+-- Use 'block' to turn it into the 'BitGet' monad to be able to run it with
49+-- 'runBitGet'.
50+-----------------------------------------------------------------------------
51+
352module Data.Binary.Bits.Get
4− ( BitGet
53+ (
54+ -- * BitGet monad
55+
56+ -- $bitget
57+
58+ BitGet
559 , runBitGet
660
61+ -- ** Get bytes
762 , getBool
63+ , getBool#
864 , getWord8
65+ , getWord16
66+ , getWord32
67+ , getWord64
968 , getWord16be
1069 , getWord32be
1170 , getWord64be
1271
72+ -- ** Skip bits
73+ , skipBits
74+ , alignByte
75+
76+ -- * Blocks
77+
78+ -- $blocks
79+ , Block
80+ , block
81+
82+ -- ** Read in Blocks
1383 , bool
1484 , word8
85+ , word16
86+ , word32
87+ , word64
1588 , word16be
1689 , word32be
1790 , word64be
1891 , byteString
19−
20− , block
21−
2292 , Data.Binary.Bits.Get.getByteString
93+ , Data.Binary.Bits.Get.getLazyByteString
94+ , Data.Binary.Bits.Get.isEmpty
95+
2396 ) where
2497
25−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
26103
27104import Data.ByteString as B
28−import Data.ByteString.Internal
29−import Data.ByteString.Unsafe
30−
31105import qualified Data.ByteString.Lazy as L
106+import Data.ByteString.Unsafe
107+import Foreign.Marshal.Alloc (mallocBytes)
108+import Foreign.Ptr
109+import Foreign.Storable (poke)
110+import System.IO.Unsafe (unsafePerformIO)
32111
33112import Data.Bits
34113import Data.Word
35−import Data.List as List ( reverse )
36−
37114import Control.Applicative
115+import Control.Monad (when,foldM_)
38116
39117import Prelude as P
40−
41−#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
42−import GHC.Base
43118import GHC.Word
44−import GHC.Int
45−#endif
46−
47−data S = S !ByteString -- Input
48− !Int -- Bit offset (0-7)
49− deriving (Show)
50−
51−-- | A block that will be read with only one boundry check. Needs to know the
52−-- number of bits in advance.
53−data Block a = Block !Int (S -> a)
119+import GHC.Base (uncheckedShiftLWord8#, wordToWord8#, Int (..), andWord8#, Word8#, (-#), Int#, xorI#, eqWord8#, TYPE)
54120
55−instance Functor Block where
56− fmap f (Block i p) = Block i (\s -> f (p s))
57−
58−instance Applicative Block where
59− pure a = Block 0 (\_ -> a)
60− (Block i p) <*> (Block j q) = Block (i+j) (\s -> p s $ q (incS i s))
61− (Block i _) *> (Block j q) = Block (i+j) (q . incS i)
62− (Block i p) <* (Block j _) = Block (i+j) p
63−
64−-- | Get a block. Guaranteed to be done with one single boundry check, and must
65−-- therefore require a statically known number of bits.
66−-- Build blocks using 'bool', 'word8', 'word16be', 'word32be', 'word64be' and 'Applicative'.
121+-- $bitget
122+-- Parse bits using a monad.
123+--
124+-- @
125+--myBitParser :: 'Get' ('Word8', 'Word8')
126+--myBitParser = 'runGetBit' parse4by4
67127--
128+--parse4by4 :: 'BitGet' ('Word8', 'Word8')
129+--parse4by4 = do
130+-- bits <- 'getWord8' 4
131+-- more <- 'getWord8' 4
132+-- return (bits,more)
133+-- @
134+
135+-- $blocks
136+-- Parse more efficiently in blocks. Each block is read with only one boundry
137+-- check (checking that there is enough input) as the size of the block can be
138+-- calculated statically. This is somewhat limiting as you cannot make the
139+-- parsing depend on the input being parsed.
140+--
68141-- @
69−-- data IPV6Header = IPV6Header {
142+--data IPV6Header = IPV6Header {
70143-- ipv6Version :: 'Word8'
71144-- , ipv6TrafficClass :: 'Word8'
72145-- , ipv6FlowLabel :: 'Word32
@@ -77,7 +150,8 @@ instance Applicative Block where
77150-- , ipv6DestinationAddress :: 'ByteString'
78151-- }
79152--
80−-- parse = IPV6Header '<$>' 'word8' 4
153+-- ipv6headerblock =
154+-- IPV6Header '<$>' 'word8' 4
81155-- '<*>' 'word8' 8
82156-- '<*>' 'word32be' 24
83157-- '<*>' 'word16be' 16
@@ -85,174 +159,134 @@ instance Applicative Block where
85159-- '<*>' 'word8' 8
86160-- '<*>' 'byteString' 16
87161-- '<*>' 'byteString' 16
162+--
163+--ipv6Header :: 'Get' IPV6Header
164+--ipv6Header = 'runBitGet' ('block' ipv6headerblock)
88165-- @
89−block :: Block a -> BitGet a
90−block (Block i p) = do
91− ensureBits i
92− modifyState (\s -> (incS i s, p s))
93−
94−-- | make_mask 3 = 00000111
95−make_mask :: Bits a => Int -> a
96−make_mask n = (1 `shiftL` fromIntegral n) - 1
97−{-# SPECIALIZE make_mask :: Int -> Int #-}
98−{-# SPECIALIZE make_mask :: Int -> Word #-}
99−{-# SPECIALIZE make_mask :: Int -> Word8 #-}
100−{-# SPECIALIZE make_mask :: Int -> Word16 #-}
101−{-# SPECIALIZE make_mask :: Int -> Word32 #-}
102−{-# SPECIALIZE make_mask :: Int -> Word64 #-}
103166
104−readBool :: S -> Bool
105−readBool (S bs n) = testBit (unsafeHead bs) (7-n)
167+data S = S {-# UNPACK #-} !ByteString -- Input
168+ {-# UNPACK #-} !Int -- Bit offset (0-7)
169+ !BitOrder -- Bit order
170+ deriving (Show)
106171
172+-- | Increment the current bit offset
107173incS :: Int -> S -> S
108−incS o (S bs n) =
109− let !o' = (n+o)
110− !d = o' `shiftR` 3
111− !n' = o' .&. make_mask 3
112− in S (unsafeDrop d bs) n'
174+incS o (S bs n bo) = S (unsafeDrop d bs) n' bo
175+ where
176+ !o' = (n+o)
177+ !d = byte_offset o'
178+ !n' = bit_offset o'
113179
180+-- | Read a single bit
181+readBool :: S -> Bool
182+readBool (S bs o bo) = case bo of
183+ BB -> testBit (unsafeHead bs) (7-o)
184+ BL -> testBit (unsafeHead bs) (7-o)
185+ LL -> testBit (unsafeHead bs) o
186+ LB -> testBit (unsafeHead bs) o
187+
188+-- | Read a single bit
189+readBool# :: S -> Int
190+readBool# (S bs (I# o) bo) = case bo of
191+ BB -> testBit# (7# -# o)
192+ BL -> testBit# (7# -# o)
193+ LL -> testBit# o
194+ LB -> testBit# o
195+ where
196+ !(W8# w) = unsafeHead bs
197+ testBit# n = I# (((w `andWord8#` (wordToWord8# 1## `uncheckedShiftLWord8#` n)) `eqWord8#` wordToWord8# 0##) `xorI#` 1#)
198+
199+
200+-- | Extract a range of bits from (ws :: ByteString)
201+--
202+-- Constraint: 8 * (length ws -1 ) < o+n <= 8 * length ws
203+extract :: (Num a, FastBits a) => BitOrder -> ByteString -> Int -> Int -> a
204+extract bo bs o n
205+ | n == 0 = 0
206+ | B.length bs == 0 = error "Empty ByteString"
207+ | otherwise = rev . mask n . foldlWithIndex' f 0 $ bs
208+ where
209+ -- B.foldl' with index
210+ foldlWithIndex' op b = fst . B.foldl' g (b,0)
211+ where g (b',i) w = (op b' w i, (i+1))
212+
213+ -- 'or' correctly shifted words
214+ f b w i = b .|. (fromIntegral w `fastShift` off i)
215+
216+ -- co-offset
217+ r = B.length bs * 8 - (o + n)
218+
219+ -- shift offset depending on the byte position (0..B.length-1)
220+ off i = case bo of
221+ LL -> 8*i - o
222+ LB -> 8*i - o
223+ BB -> (B.length bs -1 - i) * 8 - r
224+ BL -> (B.length bs -1 - i) * 8 - r
225+
226+ -- reverse bits if necessary
227+ rev = case bo of
228+ LB -> reverseBits n
229+ BL -> reverseBits n
230+ BB -> id
231+ LL -> id
232+
233+
234+-- | Generic readWord
235+readWord :: (Num a, FastBits a) => Int -> S -> a
236+readWord n (S bs o bo)
237+ | n == 0 = 0
238+ | otherwise = extract bo (unsafeTake nbytes bs) o n
239+ where nbytes = byte_offset (o+n+7)
240+
241+-- | Check that the number of bits to read is not greater than the first parameter
242+{-# INLINE readWordChecked #-}
243+readWordChecked :: (Num a, FastBits a) => Int -> Int -> S -> a
244+readWordChecked m n s
245+ | n > m = error $ "Tried to read more than " ++ show m ++ " bits (" ++ show n ++")"
246+ | otherwise = readWord n s
247+
248+-- | Read the given number of bytes and return them in Big-Endian order
249+--
250+-- Examples:
251+-- BB: xxxABCDE FGHIJKLM NOPxxxxx -> ABCDEFGH IJKLMNOP
252+-- LL: LMNOPxxx DEFGHIJK xxxxxABC -> ABCDEFGH IJKLMNOP
253+-- BL: xxxPONML KJIHGFED CBAxxxxx -> ABCDEFGH IJKLMNOP
254+-- LB: EDCBAxxx MLKJIHGF xxxxxPON -> ABCDEFGH IJKLMNOP
114255readByteString :: Int -> S -> ByteString
115−readByteString n s@(S bs o)
116− -- no offset, easy.
117− | o == 0 = unsafeTake n bs
118− -- offset. ugg. this is really naive and slow. but also pretty easy :)
119− | otherwise = B.pack (P.map (readWord8 8) (P.take n (iterate (incS 8) s)))
120−
121−readWord8 :: Int -> S -> Word8
122−readWord8 n s@(S bs o)
123− -- no bits at all, return 0
124− | n == 0 = 0
125−
126− -- all bits are in the same byte
127− -- we just need to shift and mask them right
128− | n <= 8 - o = let w = unsafeHead bs
129− m = make_mask n
130− w' = (w `shiftr_w8` (8 - o - n)) .&. m
131− in w'
132−
133− -- the bits are in two different bytes
134− -- make a word16 using both bytes, and then shift and mask
135− | n <= 8 = let w = (fromIntegral (unsafeHead bs) `shiftl_w16` 8) .|.
136− (fromIntegral (unsafeIndex bs 1))
137− m = make_mask n
138− w' = (w `shiftr_w16` (16 - o - n)) .&. m
139− in fromIntegral w'
140−
141−bit_offset :: Int -> Int
142−bit_offset n = make_mask 3 .&. n
143−
144−byte_offset :: Int -> Int
145−byte_offset n = n `shiftR` 3
146−
147−readWord16be :: Int -> S -> Word16
148−readWord16be n s@(S bs o)
149−
150− -- 8 or fewer bits, use readWord8
151− | n <= 8 = fromIntegral (readWord8 n s)
152−
153− -- handle 9 or more bits, stored in two bytes
154−
155− -- no offset, plain and simple 16 bytes
156− | o == 0 && n == 16 = let msb = fromIntegral (unsafeHead bs)
157− lsb = fromIntegral (unsafeIndex bs 1)
158− w = (msb `shiftl_w16` 8) .|. lsb
159− in w
256+readByteString n (S bs o bo) =
257+ let
258+ bs' = unsafeTake (n+1) bs
259+ bs'' = unsafeTake n bs
260+ rev = B.map (reverseBits 8)
261+ in case (o,bo) of
262+ (0,BB) -> bs''
263+ (0,LL) -> B.reverse bs''
264+ (0,LB) -> rev bs''
265+ (0,BL) -> rev . B.reverse $ bs''
266+ (_,LL) -> readByteString n (S (B.reverse bs') (8-o) BB)
267+ (_,BL) -> rev . B.reverse $ readByteString n (S bs' o BB)
268+ (_,LB) -> rev . B.reverse $ readByteString n (S bs' o LL)
269+ (_,BB) -> unsafePerformIO $ do
270+ let len = n+1
271+ ptr <- mallocBytes len
272+ let f r i = do
273+ let
274+ w = unsafeIndex bs (len-i)
275+ w' = (w `fastShiftL` o) .|. r
276+ r' = w `fastShiftR` (8-o)
277+ poke (ptr `plusPtr` (len-i)) w'
278+ return r'
279+ foldM_ f 0 [1..len]
280+ unsafeInit <$> unsafePackMallocCStringLen (ptr,len)
160281
161− -- no offset, but not full 16 bytes
162− | o == 0 = let msb = fromIntegral (unsafeHead bs)
163− lsb = fromIntegral (unsafeIndex bs 1)
164− w = (msb `shiftl_w16` (n-8)) .|. (lsb `shiftr_w16` (16-n))
165− in w
166−
167− -- with offset, and n=9-16
168− | n <= 16 = readWithOffset s shiftl_w16 shiftr_w16 n
169−
170− | otherwise = error "readWord16be: tried to read more than 16 bits"
171−
172−readWithoutOffset :: (Bits a, Num a)
173− => S -> (a -> Int -> a) -> (a -> Int -> a) -> Int -> a
174−readWithoutOffset s@(S bs o) shifterL shifterR n
175− | o /= 0 = error "readWithoutOffset: there is an offset"
176−
177− | bit_offset n == 0 && byte_offset n <= 4 =
178− let segs = byte_offset n
179− bn 0 = fromIntegral (unsafeHead bs)
180− bn n = (bn (n-1) `shifterL` 8) .|. fromIntegral (unsafeIndex bs n)
181−
182− in bn (segs-1)
183−
184− | n <= 64 = let segs = byte_offset n
185− o' = bit_offset (n - 8 + o)
186−
187− bn 0 = fromIntegral (unsafeHead bs)
188− bn n = (bn (n-1) `shifterL` 8) .|. fromIntegral (unsafeIndex bs n)
189−
190− msegs = bn (segs-1) `shifterL` o'
191−
192− last = (fromIntegral (unsafeIndex bs segs)) `shifterR` (8 - o')
193−
194− w = msegs .|. last
195− in w
196−
197−readWithOffset :: (Bits a, Num a)
198− => S -> (a -> Int -> a) -> (a -> Int -> a) -> Int -> a
199−readWithOffset s@(S bs o) shifterL shifterR n
200− | n <= 64 = let bits_in_msb = 8 - o
201− (n',top) = (n - bits_in_msb
202− , (fromIntegral (unsafeHead bs) .&. make_mask bits_in_msb) `shifterL` n')
203−
204− segs = byte_offset n'
205−
206− bn 0 = 0
207− bn n = (bn (n-1) `shifterL` 8) .|. fromIntegral (unsafeIndex bs n)
208−
209− o' = bit_offset n'
210−
211− mseg = bn segs `shifterL` o'
212−
213− last | o' > 0 = (fromIntegral (unsafeIndex bs (segs + 1))) `shifterR` (8 - o')
214− | otherwise = 0
215−
216− w = top .|. mseg .|. last
217− in w
218−
219−
220−readWord32be :: Int -> S -> Word32
221−readWord32be n s@(S bs o)
222− -- 8 or fewer bits, use readWord8
223− | n <= 8 = fromIntegral (readWord8 n s)
224−
225− -- 16 or fewer bits, use readWord16be
226− | n <= 16 = fromIntegral (readWord16be n s)
227−
228− | o == 0 = readWithoutOffset s shiftl_w32 shiftr_w32 n
229−
230− | n <= 32 = readWithOffset s shiftl_w32 shiftr_w32 n
231−
232− | otherwise = error "readWord32be: tried to read more than 32 bits"
233−
234−
235−readWord64be :: Int -> S -> Word64
236−readWord64be n s@(S bs o)
237− -- 8 or fewer bits, use readWord8
238− | n <= 8 = fromIntegral (readWord8 n s)
239−
240− -- 16 or fewer bits, use readWord16be
241− | n <= 16 = fromIntegral (readWord16be n s)
242−
243− | o == 0 = readWithoutOffset s shiftl_w64 shiftr_w64 n
244−
245− | n <= 64 = readWithOffset s shiftl_w64 shiftr_w64 n
246−
247− | otherwise = error "readWord64be: tried to read more than 64 bits"
248282
249283------------------------------------------------------------------------
250−
284+-- | 'BitGet' is a monad, applicative and a functor. See 'runBitGet'
285+-- for how to run it.
251286newtype BitGet a = B { runState :: S -> Get (S,a) }
252287
253288instance Monad BitGet where
254289 return x = B $ \s -> return (s,x)
255− fail str = B $ \_s -> fail str
256290 (B f) >>= g = B $ \s -> do (s',a) <- f s
257291 runState (g a) s'
258292
@@ -263,109 +297,200 @@ instance Applicative BitGet where
263297 pure x = return x
264298 fm <*> m = fm >>= \f -> m >>= \v -> return (f v)
265299
300+instance BitOrderable BitGet where
301+ setBitOrder bo = do
302+ (S bs o _) <- getState
303+ putState (S bs o bo)
304+
305+ getBitOrder = do
306+ (S _ _ bo) <- getState
307+ return bo
308+
309+instance Alignable BitGet where
310+ -- | Skip the given number of bits
311+ skipBits n = do
312+ ensureBits n
313+ withState (incS n)
314+
315+ -- | Skip bits if necessary to align to the next byte
316+ alignByte = do
317+ (S _ o _) <- getState
318+ when (o /= 0) $
319+ skipBits (8-o)
320+
321+
322+
323+-- | Run a 'BitGet' within the Binary packages 'Get' monad. If a byte has
324+-- been partially consumed it will be discarded once 'runBitGet' is finished.
266325runBitGet :: BitGet a -> Get a
267326runBitGet bg = do
268− (_,a) <- runState bg (S B.empty 0)
327+ s <- mkInitState
328+ (s',a) <- runState bg s
329+ putBackState s'
269330 return a
270331
332+mkInitState :: Get S
333+mkInitState = do
334+ bs <- get
335+ put B.empty
336+ return (S bs 0 BB)
337+
338+putBackState :: S -> Get ()
339+putBackState (S bs o _) = do
340+ remaining <- get
341+ let bs' = case o of
342+ 0 -> bs
343+ _ -> unsafeDrop 1 bs
344+ put (bs' `B.append` remaining)
345+
271346getState :: BitGet S
272347getState = B $ \s -> return (s,s)
273348
274349putState :: S -> BitGet ()
275350putState s = B $ \_ -> return (s,())
276351
277−modifyState :: (S -> (S,a)) -> BitGet a
278−modifyState f = B $ \s -> return (f s)
352+withState :: (S -> S) -> BitGet ()
353+withState f = do
354+ s <- getState
355+ putState $! f s
279356
280357-- | Make sure there are at least @n@ bits.
281358ensureBits :: Int -> BitGet ()
282359ensureBits n = do
283− s@(S bs o) <- getState
360+ (S bs o bo) <- getState
284361 if n <= (B.length bs * 8 - o)
285362 then return ()
286363 else do let currentBits = B.length bs * 8 - o
287− let byteCount = (n - currentBits + 7) `div` 8
288− B $ \s -> do bs' <- B.getByteString byteCount
289− return (S (bs`append`bs') o, ())
290−
364+ let byteCount = byte_offset (n - currentBits + 7)
365+ B $ \_ -> do B.ensureN byteCount
366+ bs' <- B.get
367+ put B.empty
368+ return (S (bs`append`bs') o bo, ())
369+
370+-- | Test whether all input has been consumed, i.e. there are no remaining
371+-- undecoded bytes.
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+
377+-- | Get 1 bit as a 'Bool'.
291378getBool :: BitGet Bool
292379getBool = block bool
293380
381+-- | Get 1 bit as a 'Bool'.
382+getBool# :: BitGet Int
383+getBool# = block bool#
384+
385+-- | Get @n@ bits as a 'Word8'. @n@ must be within @[0..8]@.
294386getWord8 :: Int -> BitGet Word8
295387getWord8 n = block (word8 n)
296388
389+-- | Get @n@ bits as a 'Word16'. @n@ must be within @[0..16]@.
390+getWord16 :: Int -> BitGet Word16
391+getWord16 n = block (word16 n)
392+
297393getWord16be :: Int -> BitGet Word16
298−getWord16be n = block (word16be n)
394+getWord16be = getWord16
395+{-# DEPRECATED getWord16be "Use 'getWord16' instead" #-}
396+
397+-- | Get @n@ bits as a 'Word32'. @n@ must be within @[0..32]@.
398+getWord32 :: Int -> BitGet Word32
399+getWord32 n = block (word32 n)
299400
300401getWord32be :: Int -> BitGet Word32
301−getWord32be n = block (word32be n)
402+getWord32be = getWord32
403+{-# DEPRECATED getWord32be "Use 'getWord32' instead" #-}
404+
405+-- | Get @n@ bits as a 'Word64'. @n@ must be within @[0..64]@.
406+getWord64 :: Int -> BitGet Word64
407+getWord64 n = block (word64 n)
302408
303409getWord64be :: Int -> BitGet Word64
304−getWord64be n = block (word64be n)
410+getWord64be = getWord64
411+{-# DEPRECATED getWord64be "Use 'getWord64' instead" #-}
305412
413+-- | Get @n@ bytes as a 'ByteString'.
306414getByteString :: Int -> BitGet ByteString
307415getByteString n = block (byteString n)
308416
417+-- | Get @n@ bytes as a lazy ByteString.
418+getLazyByteString :: Int -> BitGet L.ByteString
419+getLazyByteString n = do
420+ (S _ o bo) <- getState
421+ case o of
422+ 0 -> B $ \s -> do
423+ putBackState s
424+ lbs <- B.getLazyByteString (fromIntegral n)
425+ return (S B.empty 0 bo, lbs)
426+ _ -> L.fromChunks . (:[]) <$> Data.Binary.Bits.Get.getByteString n
427+
428+
429+
430+
431+
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)
435+
436+instance Functor Block where
437+ fmap f (Block i p) = Block i (\s -> f (p s))
438+
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
444+
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
451+ ensureBits i
452+ s <- getState
453+ putState $! (incS i s)
454+ return $! p s
455+
456+-- | Read a 1 bit 'Bool'.
309457bool :: Block Bool
310458bool = Block 1 readBool
311459
460+-- | Read a 1 bit 'Bool'.
461+bool# :: Block Int
462+bool# = Block 1 readBool#
463+
464+-- | Read @n@ bits as a 'Word8'. @n@ must be within @[0..8]@.
312465word8 :: Int -> Block Word8
313−word8 n = Block n (readWord8 n)
466+word8 n = Block n (readWordChecked 8 n)
467+
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)
314471
315472word16be :: Int -> Block Word16
316−word16be n = Block n (readWord16be n)
473+word16be = word16
474+{-# DEPRECATED word16be "Use 'word16' instead" #-}
475+
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)
317479
318480word32be :: Int -> Block Word32
319−word32be n = Block n (readWord32be n)
481+word32be = word32
482+{-# DEPRECATED word32be "Use 'word32' instead" #-}
483+
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)
320487
321488word64be :: Int -> Block Word64
322−word64be n = Block n (readWord64be n)
489+word64be = word64
490+{-# DEPRECATED word64be "Use 'word64' instead" #-}
323491
492+-- | Read @n@ bytes as a 'ByteString'.
324493byteString :: Int -> Block ByteString
325−byteString n = Block (n*8) (readByteString n)
494+byteString n | n > 0 = Block (n*8) (readByteString n)
495+ | otherwise = Block 0 (\_ -> B.empty)
326496
327−------------------------------------------------------------------------
328−-- Unchecked shifts, from the package binary
329−
330−shiftl_w16 :: Word16 -> Int -> Word16
331−shiftl_w32 :: Word32 -> Int -> Word32
332−shiftl_w64 :: Word64 -> Int -> Word64
333−
334−#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
335−shiftl_w8 (W8# w) (I# i) = W8# (w `uncheckedShiftL#` i)
336−shiftl_w16 (W16# w) (I# i) = W16# (w `uncheckedShiftL#` i)
337−shiftl_w32 (W32# w) (I# i) = W32# (w `uncheckedShiftL#` i)
338−
339−shiftr_w8 (W8# w) (I# i) = W8# (w `uncheckedShiftRL#` i)
340−shiftr_w16 (W16# w) (I# i) = W16# (w `uncheckedShiftRL#` i)
341−shiftr_w32 (W32# w) (I# i) = W32# (w `uncheckedShiftRL#` i)
342−
343−
344−#if WORD_SIZE_IN_BITS < 64
345−shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL64#` i)
346−shiftr_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftRL64#` i)
347−
348−#if __GLASGOW_HASKELL__ <= 606
349−-- Exported by GHC.Word in GHC 6.8 and higher
350−foreign import ccall unsafe "stg_uncheckedShiftL64"
351− uncheckedShiftL64# :: Word64# -> Int# -> Word64#
352−foreign import ccall unsafe "stg_uncheckedShiftRL64"
353− uncheckedShiftRL64# :: Word64# -> Int# -> Word64#
354−#endif
355−
356−#else
357−shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL#` i)
358−shiftr_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftRL#` i)
359−#endif
360−
361−#else
362−shiftl_w8 = shiftL
363−shiftl_w16 = shiftL
364−shiftl_w32 = shiftL
365−shiftl_w64 = shiftL
366−
367−shiftr_w8 = shiftR
368−shiftr_w16 = shiftR
369−shiftr_w32 = shiftR
370−shiftr_w64 = shiftR
371−#endif