@@ -4,6 +4,7 @@
44-- |
55-- Module : Data.Binary.Bits.Get
66-- Copyright : (c) Lennart Kolmodin 2010-2011
7+-- (c) Sylvain Henry 2015
78-- License : BSD3-style (see LICENSE)
89--
910-- Maintainer : kolmodin@gmail.com
@@ -55,13 +56,11 @@ module Data.Binary.Bits.Get
5556 -- $bitget
5657
5758 BitGet
58− , BitOrder(..)
5959 , runBitGet
60− , selectBitOrder
61− , withBitOrder
6260
6361 -- ** Get bytes
6462 , getBool
63+ , getBool#
6564 , getWord8
6665 , getWord16
6766 , getWord32
@@ -98,6 +97,9 @@ module Data.Binary.Bits.Get
9897
9998import Data.Binary.Get as B ( Get, getLazyByteString, isEmpty )
10099import 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
101103
102104import Data.ByteString as B
103105import qualified Data.ByteString.Lazy as L
@@ -113,12 +115,8 @@ import Control.Applicative
113115import Control.Monad (when,foldM_)
114116
115117import Prelude as P
116−
117−#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
118−import GHC.Base
119118import GHC.Word
120−#endif
121−
119+import GHC.Base (uncheckedShiftLWord8#, wordToWord8#, Int (..), andWord8#, Word8#, (-#), Int#, xorI#, eqWord8#, TYPE)
122120
123121-- $bitget
124122-- Parse bits using a monad.
@@ -171,16 +169,6 @@ data S = S {-# UNPACK #-} !ByteString -- Input
171169 !BitOrder -- Bit order
172170 deriving (Show)
173171
174−-- | Compute bit offset (equivalent to x `mod` 8 but faster)
175−bit_offset :: Int -> Int
176−bit_offset n = make_mask 3 .&. n
177−{-# INLINE bit_offset #-}
178−
179−-- | Compute byte offset (equivalent to x `div` 8 but faster)
180−byte_offset :: Int -> Int
181−byte_offset n = n `shiftR` 3
182−{-# INLINE byte_offset #-}
183−
184172-- | Increment the current bit offset
185173incS :: Int -> S -> S
186174incS o (S bs n bo) = S (unsafeDrop d bs) n' bo
@@ -189,58 +177,30 @@ incS o (S bs n bo) = S (unsafeDrop d bs) n' bo
189177 !d = byte_offset o'
190178 !n' = bit_offset o'
191179
192−-- | Select the bit ordering
193−selectBitOrderS :: BitOrder -> S -> S
194−selectBitOrderS bo (S bs o _) = S bs o bo
195−
196−-- | make_mask 3 = 00000111
197−make_mask :: (Bits a, Num a) => Int -> a
198−make_mask n = (1 `shiftL` fromIntegral n) - 1
199−{-# SPECIALIZE make_mask :: Int -> Int #-}
200−{-# SPECIALIZE make_mask :: Int -> Word #-}
201−{-# SPECIALIZE make_mask :: Int -> Word8 #-}
202−{-# SPECIALIZE make_mask :: Int -> Word16 #-}
203−{-# SPECIALIZE make_mask :: Int -> Word32 #-}
204−{-# SPECIALIZE make_mask :: Int -> Word64 #-}
205−
206−-- | Keep only the n least-significant bits of the given value
207−mask :: (Bits a, Num a) => Int -> a -> a
208−mask n v = v .&. make_mask n
209−{-# INLINE mask #-}
210−
211−-- | Bit order
212−--
213−-- E.g. two words of 5 bits: ABCDE, VWXYZ
214−-- - BB: ABCDEVWX YZxxxxxx
215−-- - LB: XYZABCDE xxxxxxVW
216−-- - BL: EDCBAZYX WVxxxxxx
217−-- - LL: XWVEDCBA xxxxxxZY
218−data BitOrder = BB | LB | BL | LL deriving (Show)
219−
220−-- | Reverse the @n@ least important bits of the given value
221−reverseBits :: (Num a, FastBits a, Bits a) => Int -> a -> a
222−reverseBits n value = rec value n 0
223− where
224− -- rec v i r, where
225− -- v is orginal value shifted
226− -- i is the remaining number of bits
227− -- r is current value
228− rec 0 0 r = r
229− rec 0 i r = r `fastShiftL` i
230− rec v i r = rec (v `fastShiftR` 1) (i-1) ((r `fastShiftL` 1) .|. (v .&. 0x1))
231−
232180-- | Read a single bit
233181readBool :: S -> Bool
234182readBool (S bs o bo) = case bo of
235183 BB -> testBit (unsafeHead bs) (7-o)
236184 BL -> testBit (unsafeHead bs) (7-o)
237− LB -> testBit (unsafeHead bs) o
238185 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+
239199
240200-- | Extract a range of bits from (ws :: ByteString)
241201--
242202-- Constraint: 8 * (length ws -1 ) < o+n <= 8 * length ws
243−extract :: (Num a, Bits a, FastBits a) => BitOrder -> ByteString -> Int -> Int -> a
203+extract :: (Num a, FastBits a) => BitOrder -> ByteString -> Int -> Int -> a
244204extract bo bs o n
245205 | n == 0 = 0
246206 | B.length bs == 0 = error "Empty ByteString"
@@ -258,36 +218,29 @@ extract bo bs o n
258218
259219 -- shift offset depending on the byte position (0..B.length-1)
260220 off i = case bo of
261− LB -> 8*i - o
262221 LL -> 8*i - o
222+ LB -> 8*i - o
263223 BB -> (B.length bs -1 - i) * 8 - r
264224 BL -> (B.length bs -1 - i) * 8 - r
265225
266226 -- reverse bits if necessary
267227 rev = case bo of
268− LL -> reverseBits n
228+ LB -> reverseBits n
269229 BL -> reverseBits n
270− BB -> id
271− LB -> id
230+ BB -> id
231+ LL -> id
272232
273233
274234-- | Generic readWord
275−readWord :: (Num a, Bits a, FastBits a) => Int -> S -> a
235+readWord :: (Num a, FastBits a) => Int -> S -> a
276236readWord n (S bs o bo)
277237 | n == 0 = 0
278− | o+n <= 8 = extract bo (unsafeTake 1 bs) o n
279− | o+n <= 16 = extract bo (unsafeTake 2 bs) o n
280− | o+n <= 24 = extract bo (unsafeTake 3 bs) o n
281− | o+n <= 32 = extract bo (unsafeTake 4 bs) o n
282− | o+n <= 40 = extract bo (unsafeTake 5 bs) o n
283− | o+n <= 48 = extract bo (unsafeTake 6 bs) o n
284− | o+n <= 56 = extract bo (unsafeTake 7 bs) o n
285− | o+n <= 64 = extract bo (unsafeTake 8 bs) o n
286− | otherwise = extract bo (unsafeTake ((o+n+7) `div` 8) bs) o n
238+ | otherwise = extract bo (unsafeTake nbytes bs) o n
239+ where nbytes = byte_offset (o+n+7)
287240
288241-- | Check that the number of bits to read is not greater than the first parameter
289242{-# INLINE readWordChecked #-}
290−readWordChecked :: (Num a, Bits a, FastBits a) => Int -> Int -> S -> a
243+readWordChecked :: (Num a, FastBits a) => Int -> Int -> S -> a
291244readWordChecked m n s
292245 | n > m = error $ "Tried to read more than " ++ show m ++ " bits (" ++ show n ++")"
293246 | otherwise = readWord n s
@@ -295,23 +248,24 @@ readWordChecked m n s
295248-- | Read the given number of bytes and return them in Big-Endian order
296249--
297250-- Examples:
298−-- BB: xxxABCDE FGHIJKLM NOPQRxxx -> ABCDEFGH IJKLMNOP QRxxxxxx
299−-- LB: NOPQRxxx FGHIJKLM xxxABCDE -> ABCDEFGH IJKLMNOP QRxxxxxx
300−-- BL: xxxRQPON MLKJIHGF EDCBAxxx -> ABCDEFGH IJKLMNOP QRxxxxxx
301−-- LL: EDCBAxxx MLKJIHGF xxxRQPON -> ABCDEFGH IJKLMNOP QRxxxxxx
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
302255readByteString :: Int -> S -> ByteString
303256readByteString n (S bs o bo) =
304257 let
305− bs' = unsafeTake (n+1) bs
306− rev = B.map (reverseBits 9)
258+ bs' = unsafeTake (n+1) bs
259+ bs'' = unsafeTake n bs
260+ rev = B.map (reverseBits 8)
307261 in case (o,bo) of
308− (0,BB) -> unsafeTake n bs
309− (0,LB) -> B.reverse (unsafeTake n bs)
310− (0,BL) -> rev (unsafeTake n bs)
311− (0,LL) -> rev (B.reverse (unsafeTake n bs))
312− (_,BL) -> rev (readByteString n (S (B.reverse bs') o LB))
313− (_,LL) -> rev (readByteString n (S (B.reverse bs') o BB))
314− (_,LB) -> readByteString n (S (B.reverse bs') o BB)
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)
315269 (_,BB) -> unsafePerformIO $ do
316270 let len = n+1
317271 ptr <- mallocBytes len
@@ -333,7 +287,6 @@ newtype BitGet a = B { runState :: S -> Get (S,a) }
333287
334288instance Monad BitGet where
335289 return x = B $ \s -> return (s,x)
336− fail str = B $ \s -> putBackState s >> fail str
337290 (B f) >>= g = B $ \s -> do (s',a) <- f s
338291 runState (g a) s'
339292
@@ -344,6 +297,29 @@ instance Applicative BitGet where
344297 pure x = return x
345298 fm <*> m = fm >>= \f -> m >>= \v -> return (f v)
346299
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+
347323-- | Run a 'BitGet' within the Binary packages 'Get' monad. If a byte has
348324-- been partially consumed it will be discarded once 'runBitGet' is finished.
349325runBitGet :: BitGet a -> Get a
@@ -378,13 +354,6 @@ withState f = do
378354 s <- getState
379355 putState $! f s
380356
381−-- | Get the bit ordering
382−getBitOrder :: BitGet BitOrder
383−getBitOrder = do
384− (S _ _ bo) <- getState
385− return bo
386−
387−
388357-- | Make sure there are at least @n@ bits.
389358ensureBits :: Int -> BitGet ()
390359ensureBits n = do
@@ -398,33 +367,6 @@ ensureBits n = do
398367 put B.empty
399368 return (S (bs`append`bs') o bo, ())
400369
401−-- | Skip the given number of bits
402−skipBits :: Int -> BitGet ()
403−skipBits n = do
404− ensureBits n
405− withState (incS n)
406−
407−-- | Skip bits if necessary to align to the next byte
408−alignByte :: BitGet ()
409−alignByte = do
410− (S _ o _) <- getState
411− when (o /= 0) $
412− skipBits (8-o)
413−
414−-- | Select the bit ordering
415−selectBitOrder :: BitOrder -> BitGet ()
416−selectBitOrder = withState . selectBitOrderS
417−
418−withBitOrder :: BitOrder -> BitGet a -> BitGet a
419−withBitOrder bo f = do
420− bo' <- getBitOrder
421− selectBitOrder bo
422− r <- f
423− selectBitOrder bo'
424− return r
425−
426−
427−
428370-- | Test whether all input has been consumed, i.e. there are no remaining
429371-- undecoded bytes.
430372isEmpty :: BitGet Bool
@@ -436,6 +378,10 @@ isEmpty = B $ \ (S bs o bo) -> if B.null bs
436378getBool :: BitGet Bool
437379getBool = block bool
438380
381+-- | Get 1 bit as a 'Bool'.
382+getBool# :: BitGet Int
383+getBool# = block bool#
384+
439385-- | Get @n@ bits as a 'Word8'. @n@ must be within @[0..8]@.
440386getWord8 :: Int -> BitGet Word8
441387getWord8 n = block (word8 n)
@@ -511,6 +457,10 @@ block (Block i p) = do
511457bool :: Block Bool
512458bool = Block 1 readBool
513459
460+-- | Read a 1 bit 'Bool'.
461+bool# :: Block Int
462+bool# = Block 1 readBool#
463+
514464-- | Read @n@ bits as a 'Word8'. @n@ must be within @[0..8]@.
515465word8 :: Int -> Block Word8
516466word8 n = Block n (readWordChecked 8 n)
@@ -544,84 +494,3 @@ byteString :: Int -> Block ByteString
544494byteString n | n > 0 = Block (n*8) (readByteString n)
545495 | otherwise = Block 0 (\_ -> B.empty)
546496
547−
548−---------------------------------------------------------------------
549−-- Unchecked shifts, from the "binary" package
550−
551−-- | Class for types supporting fast bit shifting
552−class FastBits a where
553− fastShiftR :: a -> Int -> a
554− fastShiftL :: a -> Int -> a
555−
556− {-# INLINE fastShift #-}
557− fastShift :: a -> Int -> a
558− fastShift x n
559− | n > 0 = fastShiftL x n
560− | n < 0 = fastShiftR x (negate n)
561− | otherwise = x
562−
563−instance FastBits Word8 where
564− fastShiftR = shiftr_w8
565− fastShiftL = shiftl_w8
566−
567−instance FastBits Word16 where
568− fastShiftR = shiftr_w16
569− fastShiftL = shiftl_w16
570−
571−instance FastBits Word32 where
572− fastShiftR = shiftr_w32
573− fastShiftL = shiftl_w32
574−
575−instance FastBits Word64 where
576− fastShiftR = shiftr_w64
577− fastShiftL = shiftl_w64
578−
579−
580−shiftl_w8 :: Word8 -> Int -> Word8
581−shiftl_w16 :: Word16 -> Int -> Word16
582−shiftl_w32 :: Word32 -> Int -> Word32
583−shiftl_w64 :: Word64 -> Int -> Word64
584−
585−shiftr_w8 :: Word8 -> Int -> Word8
586−shiftr_w16 :: Word16 -> Int -> Word16
587−shiftr_w32 :: Word32 -> Int -> Word32
588−shiftr_w64 :: Word64 -> Int -> Word64
589−
590−#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
591−shiftl_w8 (W8# w) (I# i) = W8# (w `uncheckedShiftL#` i)
592−shiftl_w16 (W16# w) (I# i) = W16# (w `uncheckedShiftL#` i)
593−shiftl_w32 (W32# w) (I# i) = W32# (w `uncheckedShiftL#` i)
594−
595−shiftr_w8 (W8# w) (I# i) = W8# (w `uncheckedShiftRL#` i)
596−shiftr_w16 (W16# w) (I# i) = W16# (w `uncheckedShiftRL#` i)
597−shiftr_w32 (W32# w) (I# i) = W32# (w `uncheckedShiftRL#` i)
598−
599−
600−#if WORD_SIZE_IN_BITS < 64
601−shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL64#` i)
602−shiftr_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftRL64#` i)
603−
604−#if __GLASGOW_HASKELL__ <= 606
605−-- Exported by GHC.Word in GHC 6.8 and higher
606−foreign import ccall unsafe "stg_uncheckedShiftL64"
607− uncheckedShiftL64# :: Word64# -> Int# -> Word64#
608−foreign import ccall unsafe "stg_uncheckedShiftRL64"
609− uncheckedShiftRL64# :: Word64# -> Int# -> Word64#
610−#endif
611−
612−#else
613−shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL#` i)
614−shiftr_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftRL#` i)
615−#endif
616−
617−#else
618−shiftl_w8 = shiftL
619−shiftl_w16 = shiftL
620−shiftl_w32 = shiftL
621−shiftl_w64 = shiftL
622−
623−shiftr_w8 = shiftR
624−shiftr_w16 = shiftR
625−shiftr_w32 = shiftR
626−shiftr_w64 = shiftR
627−#endif