@@ -1,239 +1,292 @@
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− ( T(..)
53+ (
54+ -- * BitGet monad
55+
56+ -- $bitget
57+
58+ BitGet
559 , runBitGet
6− , BitGet
760
61+ -- ** Get bytes
862 , getBool
63+ , getBool#
964 , getWord8
65+ , getWord16
66+ , getWord32
67+ , getWord64
1068 , getWord16be
1169 , getWord32be
1270 , getWord64be
1371
72+ -- ** Skip bits
73+ , skipBits
74+ , alignByte
75+
76+ -- * Blocks
77+
78+ -- $blocks
79+ , Block
80+ , block
81+
82+ -- ** Read in Blocks
1483 , bool
1584 , word8
85+ , word16
86+ , word32
87+ , word64
1688 , word16be
1789 , word32be
1890 , word64be
19−
20− , block
21−
91+ , byteString
2292 , Data.Binary.Bits.Get.getByteString
23−
24− , readBool
25− , readWord8
26− , readWord16be
93+ , Data.Binary.Bits.Get.getLazyByteString
94+ , Data.Binary.Bits.Get.isEmpty
2795
2896 ) where
2997
30−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
31103
32104import Data.ByteString as B
33−import Data.ByteString.Internal
34−import Data.ByteString.Unsafe
35−
36105import 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)
37111
38112import Data.Bits
39113import Data.Word
40−import Data.List as List ( reverse )
41−
42114import Control.Applicative
115+import Control.Monad (when,foldM_)
43116
44117import Prelude as P
45−
46−#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
47−import GHC.Base
48118import GHC.Word
49−import GHC.Int
50−#endif
51−
52−data T a b = !a :*: !b deriving (Show)
53−
54−data S = S !ByteString -- ^ Input
55− !Int -- ^ Bit offset (0-7)
119+import GHC.Base (uncheckedShiftLWord8#, wordToWord8#, Int (..), andWord8#, Word8#, (-#), Int#, xorI#, eqWord8#, TYPE)
120+
121+-- $bitget
122+-- Parse bits using a monad.
123+--
124+-- @
125+--myBitParser :: 'Get' ('Word8', 'Word8')
126+--myBitParser = 'runGetBit' parse4by4
127+--
128+--parse4by4 :: 'BitGet' ('Word8', 'Word8')
129+--parse4by4 = do
130+-- bits <- 'getWord8' 4
131+-- more <- 'getWord8' 4
132+-- return (bits,more)
133+-- @
134+
135+-- $blocks
136+-- Parse more efficiently in blocks. Each block is read with only one boundry
137+-- check (checking that there is enough input) as the size of the block can be
138+-- calculated statically. This is somewhat limiting as you cannot make the
139+-- parsing depend on the input being parsed.
140+--
141+-- @
142+--data IPV6Header = IPV6Header {
143+-- ipv6Version :: 'Word8'
144+-- , ipv6TrafficClass :: 'Word8'
145+-- , ipv6FlowLabel :: 'Word32
146+-- , ipv6PayloadLength :: 'Word16'
147+-- , ipv6NextHeader :: 'Word8'
148+-- , ipv6HopLimit :: 'Word8'
149+-- , ipv6SourceAddress :: 'ByteString'
150+-- , ipv6DestinationAddress :: 'ByteString'
151+-- }
152+--
153+-- ipv6headerblock =
154+-- IPV6Header '<$>' 'word8' 4
155+-- '<*>' 'word8' 8
156+-- '<*>' 'word32be' 24
157+-- '<*>' 'word16be' 16
158+-- '<*>' 'word8' 8
159+-- '<*>' 'word8' 8
160+-- '<*>' 'byteString' 16
161+-- '<*>' 'byteString' 16
162+--
163+--ipv6Header :: 'Get' IPV6Header
164+--ipv6Header = 'runBitGet' ('block' ipv6headerblock)
165+-- @
166+
167+data S = S {-# UNPACK #-} !ByteString -- Input
168+ {-# UNPACK #-} !Int -- Bit offset (0-7)
169+ !BitOrder -- Bit order
56170 deriving (Show)
57171
58−-- | A block that will be read with only one boundry check.
59−data Block a = Block Int (S -> a)
60−
61−instance Functor Block where
62− fmap f (Block i p) = Block i (\s -> f (p s))
63−
64−instance Applicative Block where
65− pure a = Block 0 (\_ -> a)
66− (Block i p) <*> (Block j q) = Block (i+j) (\s -> p s $ q (incS i s))
67− (Block i _) *> (Block j q) = Block (i+j) (q . incS i)
68− (Block i p) <* (Block j _) = Block (i+j) p
69−
70−block :: Block a -> BitGet a
71−block (Block i p) = do
72− ensureBits i
73− modifyState (\s -> (incS i s, p s))
74−
75−-- | make_mask 3 = 00000111
76−make_mask :: Bits a => Int -> a
77−make_mask n = (1 `shiftL` fromIntegral n) - 1
78−{-# SPECIALIZE make_mask :: Int -> Int #-}
79−{-# SPECIALIZE make_mask :: Int -> Word #-}
80−{-# SPECIALIZE make_mask :: Int -> Word8 #-}
81−{-# SPECIALIZE make_mask :: Int -> Word16 #-}
82−{-# SPECIALIZE make_mask :: Int -> Word32 #-}
83−{-# SPECIALIZE make_mask :: Int -> Word64 #-}
84−
85−readBool :: S -> Bool
86−readBool (S bs n) = testBit (unsafeHead bs) (7-n)
87−
172+-- | Increment the current bit offset
88173incS :: Int -> S -> S
89−incS o (S bs n) =
90− let !o' = (n+o)
91− !d = o' `shiftR` 3
92− !n' = o' .&. make_mask 3
93− 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'
94179
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
95255readByteString :: Int -> S -> ByteString
96−readByteString n s@(S bs o)
97− -- no offset, easy.
98− | o == 0 = unsafeTake n bs
99− -- offset. ugg. this is really naive and slow. but also pretty easy :)
100− | otherwise = B.pack (P.map (readWord8 8) (P.take n (iterate (incS 8) s)))
101−
102−readWord8 :: Int -> S -> Word8
103−readWord8 n s@(S bs o)
104− -- no bits at all, return 0
105− | n == 0 = 0
106−
107− -- all bits are in the same byte
108− -- we just need to shift and mask them right
109− | n <= 8 - o = let w = unsafeHead bs
110− m = make_mask n
111− w' = (w `shiftr_w8` (8 - o - n)) .&. m
112− in w'
113−
114− -- the bits are in two different bytes
115− -- make a word16 using both bytes, and then shift and mask
116− | n <= 8 = let w = (fromIntegral (unsafeHead bs) `shiftl_w16` 8) .|.
117− (fromIntegral (unsafeIndex bs 1))
118− m = make_mask n
119− w' = (w `shiftr_w16` (16 - o - n)) .&. m
120− in fromIntegral w'
121−
122−bit_offset :: Int -> Int
123−bit_offset n = make_mask 3 .&. n
124−
125−byte_offset :: Int -> Int
126−byte_offset n = n `shiftR` 3
127−
128−readWord16be :: Int -> S -> Word16
129−readWord16be n s@(S bs o)
130−
131− -- 8 or fewer bits, use readWord8
132− | n <= 8 = fromIntegral (readWord8 n s)
133−
134− -- handle 9 or more bits, stored in two bytes
135−
136− -- no offset, plain and simple 16 bytes
137− | o == 0 && n == 16 = let msb = fromIntegral (unsafeHead bs)
138− lsb = fromIntegral (unsafeIndex bs 1)
139− w = (msb `shiftl_w16` 8) .|. lsb
140− in w
141−
142− -- no offset, but not full 16 bytes
143− | o == 0 = let msb = fromIntegral (unsafeHead bs)
144− lsb = fromIntegral (unsafeIndex bs 1)
145− w = (msb `shiftl_w16` (n-8)) .|. (lsb `shiftr_w16` (16-n))
146− in w
147−
148− -- with offset, and n=9-16
149− | n <= 16 = readWithOffset s shiftl_w16 shiftr_w16 n
150−
151− | otherwise = error "readWord16be: tried to read more than 16 bits"
152−
153−readWithoutOffset :: (Bits a, Num a)
154− => S -> (a -> Int -> a) -> (a -> Int -> a) -> Int -> a
155−readWithoutOffset s@(S bs o) shifterL shifterR n
156− | o /= 0 = error "readWithoutOffset: there is an offset"
157−
158− | bit_offset n == 0 && byte_offset n <= 4 =
159− let segs = byte_offset n
160− bn 0 = fromIntegral (unsafeHead bs)
161− bn n = (bn (n-1) `shifterL` 8) .|. fromIntegral (unsafeIndex bs n)
162−
163− in bn (segs-1)
164−
165− | n <= 64 = let segs = byte_offset n
166− o' = bit_offset (n - 8 + o)
167−
168− bn 0 = fromIntegral (unsafeHead bs)
169− bn n = (bn (n-1) `shifterL` 8) .|. fromIntegral (unsafeIndex bs n)
170−
171− msegs = bn (segs-1) `shifterL` o'
172−
173− last = (fromIntegral (unsafeIndex bs segs)) `shifterR` (8 - o')
174−
175− w = msegs .|. last
176− in w
177−
178−readWithOffset :: (Bits a, Num a)
179− => S -> (a -> Int -> a) -> (a -> Int -> a) -> Int -> a
180−readWithOffset s@(S bs o) shifterL shifterR n
181− | n <= 64 = let bits_in_msb = 8 - o
182− (n',top) = (n - bits_in_msb
183− , (fromIntegral (unsafeHead bs) .&. make_mask bits_in_msb) `shifterL` n')
184−
185− segs = byte_offset n'
186−
187− bn 0 = 0
188− bn n = (bn (n-1) `shifterL` 8) .|. fromIntegral (unsafeIndex bs n)
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)
189281
190− o' = bit_offset n'
191−
192− mseg = bn segs `shifterL` o'
193−
194− last | o' > 0 = (fromIntegral (unsafeIndex bs (segs + 1))) `shifterR` (8 - o')
195− | otherwise = 0
196−
197− w = top .|. mseg .|. last
198− in w
199−
200−
201−readWord32be :: Int -> S -> Word32
202−readWord32be n s@(S bs o)
203− -- 8 or fewer bits, use readWord8
204− | n <= 8 = fromIntegral (readWord8 n s)
205−
206− -- 16 or fewer bits, use readWord16be
207− | n <= 16 = fromIntegral (readWord16be n s)
208−
209− | o == 0 = readWithoutOffset s shiftl_w32 shiftr_w32 n
210−
211− | n <= 32 = readWithOffset s shiftl_w32 shiftr_w32 n
212−
213− | otherwise = error "readWord32be: tried to read more than 32 bits"
214−
215−
216−readWord64be :: Int -> S -> Word64
217−readWord64be n s@(S bs o)
218− -- 8 or fewer bits, use readWord8
219− | n <= 8 = fromIntegral (readWord8 n s)
220−
221− -- 16 or fewer bits, use readWord16be
222− | n <= 16 = fromIntegral (readWord16be n s)
223−
224− | o == 0 = readWithoutOffset s shiftl_w64 shiftr_w64 n
225−
226− | n <= 64 = readWithOffset s shiftl_w64 shiftr_w64 n
227−
228− | otherwise = error "readWord64be: tried to read more than 64 bits"
229282
230283------------------------------------------------------------------------
231−-- unrolled codensity/state monad
284+-- | 'BitGet' is a monad, applicative and a functor. See 'runBitGet'
285+-- for how to run it.
232286newtype BitGet a = B { runState :: S -> Get (S,a) }
233287
234288instance Monad BitGet where
235289 return x = B $ \s -> return (s,x)
236− fail str = B $ \_s -> fail str
237290 (B f) >>= g = B $ \s -> do (s',a) <- f s
238291 runState (g a) s'
239292
@@ -244,192 +297,200 @@ instance Applicative BitGet where
244297 pure x = return x
245298 fm <*> m = fm >>= \f -> m >>= \v -> return (f v)
246299
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.
247325runBitGet :: BitGet a -> Get a
248326runBitGet bg = do
249− (_,a) <- runState bg (S B.empty 0)
327+ s <- mkInitState
328+ (s',a) <- runState bg s
329+ putBackState s'
250330 return a
251331
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+
252346getState :: BitGet S
253347getState = B $ \s -> return (s,s)
254348
255349putState :: S -> BitGet ()
256350putState s = B $ \_ -> return (s,())
257351
258−modifyState :: (S -> (S,a)) -> BitGet a
259−modifyState f = B $ \s -> return (f s)
352+withState :: (S -> S) -> BitGet ()
353+withState f = do
354+ s <- getState
355+ putState $! f s
260356
261357-- | Make sure there are at least @n@ bits.
262358ensureBits :: Int -> BitGet ()
263359ensureBits n = do
264− s@(S bs o) <- getState
360+ (S bs o bo) <- getState
265361 if n <= (B.length bs * 8 - o)
266362 then return ()
267363 else do let currentBits = B.length bs * 8 - o
268− let byteCount = (n - currentBits + 7) `div` 8
269− B $ \s -> do bs' <- B.getByteString byteCount
270− return (S (bs`append`bs') o, ())
271−
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'.
272378getBool :: BitGet Bool
273379getBool = block bool
274380
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]@.
275386getWord8 :: Int -> BitGet Word8
276387getWord8 n = block (word8 n)
277388
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+
278393getWord16be :: Int -> BitGet Word16
279−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)
280400
281401getWord32be :: Int -> BitGet Word32
282−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)
283408
284409getWord64be :: Int -> BitGet Word64
285−getWord64be n = block (word64be n)
410+getWord64be = getWord64
411+{-# DEPRECATED getWord64be "Use 'getWord64' instead" #-}
286412
413+-- | Get @n@ bytes as a 'ByteString'.
287414getByteString :: Int -> BitGet ByteString
288415getByteString n = block (byteString n)
289416
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'.
290457bool :: Block Bool
291458bool = Block 1 readBool
292459
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]@.
293465word8 :: Int -> Block Word8
294−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)
295471
296472word16be :: Int -> Block Word16
297−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)
298479
299480word32be :: Int -> Block Word32
300−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)
301487
302488word64be :: Int -> Block Word64
303−word64be n = Block n (readWord64be n)
489+word64be = word64
490+{-# DEPRECATED word64be "Use 'word64' instead" #-}
304491
492+-- | Read @n@ bytes as a 'ByteString'.
305493byteString :: Int -> Block ByteString
306−byteString n = Block (n*8) (readByteString n)
307−
308−------------------------------------------------------------------------
309−-- Unchecked shifts, from the package binary
310−
311−shiftl_w16 :: Word16 -> Int -> Word16
312−shiftl_w32 :: Word32 -> Int -> Word32
313−shiftl_w64 :: Word64 -> Int -> Word64
314−
315−#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
316−shiftl_w8 (W8# w) (I# i) = W8# (w `uncheckedShiftL#` i)
317−shiftl_w16 (W16# w) (I# i) = W16# (w `uncheckedShiftL#` i)
318−shiftl_w32 (W32# w) (I# i) = W32# (w `uncheckedShiftL#` i)
319−
320−shiftr_w8 (W8# w) (I# i) = W8# (w `uncheckedShiftRL#` i)
321−shiftr_w16 (W16# w) (I# i) = W16# (w `uncheckedShiftRL#` i)
322−shiftr_w32 (W32# w) (I# i) = W32# (w `uncheckedShiftRL#` i)
323−
324−
325−#if WORD_SIZE_IN_BITS < 64
326−shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL64#` i)
327−shiftr_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftRL64#` i)
328−
329−#if __GLASGOW_HASKELL__ <= 606
330−-- Exported by GHC.Word in GHC 6.8 and higher
331−foreign import ccall unsafe "stg_uncheckedShiftL64"
332− uncheckedShiftL64# :: Word64# -> Int# -> Word64#
333−foreign import ccall unsafe "stg_uncheckedShiftRL64"
334− uncheckedShiftRL64# :: Word64# -> Int# -> Word64#
335−#endif
336−
337−#else
338−shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL#` i)
339−shiftr_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftRL#` i)
340−#endif
341−
342−#else
343−shiftl_w8 = shiftL
344−shiftl_w16 = shiftL
345−shiftl_w32 = shiftL
346−shiftl_w64 = shiftL
347−
348−shiftr_w8 = shiftR
349−shiftr_w16 = shiftR
350−shiftr_w32 = shiftR
351−shiftr_w64 = shiftR
352−#endif
353−
354−{-
355−data R a where
356− RBool :: R Bool
357− RWord8 :: Int -> R Word8
358− RWord16be :: Int -> R Word16
359− RWord32be :: Int -> R Word32
360− RByteString :: Int -> R ByteString
361− RThis :: a -> R a
362− RNextTo :: R a -> R b -> R (T a b)
363− RMap :: R b -> (b -> R a) -> R a
364− RMapPure :: R a -> (a -> b) -> R b
365− RList :: Int -> R a -> R [a]
366− RCheck :: R a -> (a -> Bool) -> String -> R a
367−
368−instance Functor R where
369− fmap f m = RMapPure m f
370−
371−instance Show (R a) where
372− show r = case r of
373− RBool -> "Bool"
374−
375−size_in_bits :: forall a. R a -- ^ The record
376− -> Int -- ^ Number of bits
377−size_in_bits r = case r of
378− RBool -> 1
379− RWord8 n -> min n 8
380− RWord16be n -> min n 16
381− RWord32be n -> min n 16
382− RByteString n -> 8 * n
383− RThis _ -> 0
384− RList n r -> n * size_in_bits r
385− RMap r _ -> size_in_bits r
386− RMapPure r _ -> size_in_bits r
387− RCheck r _ _ -> size_in_bits r
388− RNextTo a b -> size_in_bits a + size_in_bits b
389−
390−size_in_bytes :: forall a. R a
391− -> Int
392−size_in_bytes r = byte_offset (size_in_bits r + 7)
393−
394−get :: R a -> Get a
395−get r = do
396− bs <- getByteString (size_in_bytes r)
397− a :*: s <- getR (S bs 0) r
398− return a
399−
400−getR :: S -> R a -> Get (T a S)
401−getR s0 r = do
402− case r of
403− RBool -> return (readBool s0)
404− RWord8 n -> return (readWord8 s0 n)
405− RWord16be n -> return (readWord16be s0 n)
406− RWord32be n -> return (readWord32be s0 n)
407− RByteString n -> return (readByteString s0 n)
408− RThis x -> return (x :*: s0)
409− RNextTo a b -> do
410− t :*: s <- getR s0 a
411− u :*: s' <- getR s b
412− return (t:*:u:*:s')
413− RMap r p -> do
414− a :*: s@(S bs o) <- getR s0 r
415− let codepath = p a
416− required_bytes = byte_offset (size_in_bits r - o)
417− bs' <- getByteString required_bytes
418− getR (S (bs `append` bs') o) codepath
419− RMapPure r f -> do
420− a :*: s <- getR s0 r
421− return (f a :*: s)
422− RList n r ->
423− let loop 0 s acc = return (List.reverse acc :*: s)
424− loop m s acc = do
425− a :*: s' <- getR s r
426− loop (m-1) s' (a:acc)
427− in loop n s0 []
428− RCheck r c m -> do
429− a :*: s <- getR s0 r
430− if c a
431− then return (a :*: s)
432− else fail m
433−-}
434−
494+byteString n | n > 0 = Block (n*8) (readByteString n)
495+ | otherwise = Block 0 (\_ -> B.empty)
435496