@@ -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
@@ -55,14 +56,11 @@ module Data.Binary.Bits.Get
55 -- $bitget
56 -- $bitget
59 , runBitGet
59 , runBitGet
64 -- ** Get bytes
61 -- ** Get bytes
66 , getWord8
64 , getWord8
67 , getWord16
65 , getWord16
68 , getWord32
66 , getWord32
@@ -99,6 +97,9 @@ module Data.Binary.Bits.Get
100import Data.Binary.Get as B ( Get, getLazyByteString, isEmpty )
98import Data.Binary.Get as B ( Get, getLazyByteString, isEmpty )
101import Data.Binary.Get.Internal as B ( get, put, ensureN )
99import 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
103import Data.ByteString as B
104import Data.ByteString as B
104import qualified Data.ByteString.Lazy as L
105import qualified Data.ByteString.Lazy as L
@@ -114,12 +115,8 @@ import Control.Applicative
114import Control.Monad (when,foldM_)
115import Control.Monad (when,foldM_)
116import Prelude as P
117import Prelude as P
118−#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
120import GHC.Word
118import GHC.Word
121−#endif
119+import GHC.Base (uncheckedShiftLWord8#, wordToWord8#, Int (..), andWord8#, Word8#, (-#), Int#, xorI#, eqWord8#, TYPE)
124-- $bitget
121-- $bitget
125-- Parse bits using a monad.
122-- Parse bits using a monad.
@@ -172,16 +169,6 @@ data S = S {-# UNPACK #-} !ByteString -- Input
172 !BitOrder -- Bit order
169 !BitOrder -- Bit order
173 deriving (Show)
170 deriving (Show)
175−-- | Compute bit offset (equivalent to x `mod` 8 but faster)
176−bit_offset :: Int -> Int
177−bit_offset n = make_mask 3 .&. n
178−{-# INLINE bit_offset #-}
180−-- | Compute byte offset (equivalent to x `div` 8 but faster)
181−byte_offset :: Int -> Int
182−byte_offset n = n `shiftR` 3
183−{-# INLINE byte_offset #-}
185-- | Increment the current bit offset
172-- | Increment the current bit offset
186incS :: Int -> S -> S
173incS :: Int -> S -> S
187incS o (S bs n bo) = S (unsafeDrop d bs) n' bo
174incS o (S bs n bo) = S (unsafeDrop d bs) n' bo
@@ -190,58 +177,30 @@ incS o (S bs n bo) = S (unsafeDrop d bs) n' bo
190 !d = byte_offset o'
177 !d = byte_offset o'
191 !n' = bit_offset o'
178 !n' = bit_offset o'
193−-- | Select the bit ordering
194−selectBitOrderS :: BitOrder -> S -> S
195−selectBitOrderS bo (S bs o _) = S bs o bo
197−-- | make_mask 3 = 00000111
198−make_mask :: (Bits a, Num a) => Int -> a
199−make_mask n = (1 `shiftL` fromIntegral n) - 1
200−{-# SPECIALIZE make_mask :: Int -> Int #-}
201−{-# SPECIALIZE make_mask :: Int -> Word #-}
202−{-# SPECIALIZE make_mask :: Int -> Word8 #-}
203−{-# SPECIALIZE make_mask :: Int -> Word16 #-}
204−{-# SPECIALIZE make_mask :: Int -> Word32 #-}
205−{-# SPECIALIZE make_mask :: Int -> Word64 #-}
207−-- | Keep only the n least-significant bits of the given value
208−mask :: (Bits a, Num a) => Int -> a -> a
209−mask n v = v .&. make_mask n
214−-- E.g. two words of 5 bits: ABCDE, VWXYZ
215−-- - BB: ABCDEVWX YZxxxxxx
216−-- - LB: XYZABCDE xxxxxxVW
217−-- - BL: EDCBAZYX WVxxxxxx
218−-- - LL: XWVEDCBA xxxxxxZY
219−data BitOrder = BB | LB | BL | LL deriving (Show)
221−-- | Reverse the @n@ least important bits of the given value
222−reverseBits :: (Num a, FastBits a, Bits a) => Int -> a -> a
223−reverseBits n value = rec value n 0
226− -- v is orginal value shifted
227− -- i is the remaining number of bits
228− -- r is current value
230− rec 0 i r = r `fastShiftL` i
231− rec v i r = rec (v `fastShiftR` 1) (i-1) ((r `fastShiftL` 1) .|. (v .&. 0x1))
233-- | Read a single bit
180-- | Read a single bit
234readBool :: S -> Bool
181readBool :: S -> Bool
235readBool (S bs o bo) = case bo of
182readBool (S bs o bo) = case bo of
236 BB -> testBit (unsafeHead bs) (7-o)
183 BB -> testBit (unsafeHead bs) (7-o)
237 BL -> testBit (unsafeHead bs) (7-o)
184 BL -> testBit (unsafeHead bs) (7-o)
238− LB -> testBit (unsafeHead bs) o
239 LL -> testBit (unsafeHead bs) o
185 LL -> testBit (unsafeHead bs) o
186+ LB -> testBit (unsafeHead bs) o
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)
196+ !(W8# w) = unsafeHead bs
197+ testBit# n = I# (((w `andWord8#` (wordToWord8# 1## `uncheckedShiftLWord8#` n)) `eqWord8#` wordToWord8# 0##) `xorI#` 1#)
241-- | Extract a range of bits from (ws :: ByteString)
200-- | Extract a range of bits from (ws :: ByteString)
243-- Constraint: 8 * (length ws -1 ) < o+n <= 8 * length ws
202-- Constraint: 8 * (length ws -1 ) < o+n <= 8 * length ws
244−extract :: (Num a, Bits a, FastBits a) => BitOrder -> ByteString -> Int -> Int -> a
203+extract :: (Num a, FastBits a) => BitOrder -> ByteString -> Int -> Int -> a
245extract bo bs o n
204extract bo bs o n
246 | n == 0 = 0
205 | n == 0 = 0
247 | B.length bs == 0 = error "Empty ByteString"
206 | B.length bs == 0 = error "Empty ByteString"
@@ -259,21 +218,21 @@ extract bo bs o n
260 -- shift offset depending on the byte position (0..B.length-1)
219 -- shift offset depending on the byte position (0..B.length-1)
261 off i = case bo of
220 off i = case bo of
263 LL -> 8*i - o
221 LL -> 8*i - o
264 BB -> (B.length bs -1 - i) * 8 - r
223 BB -> (B.length bs -1 - i) * 8 - r
265 BL -> (B.length bs -1 - i) * 8 - r
224 BL -> (B.length bs -1 - i) * 8 - r
267 -- reverse bits if necessary
226 -- reverse bits if necessary
268 rev = case bo of
227 rev = case bo of
269− LL -> reverseBits n
228+ LB -> reverseBits n
270 BL -> reverseBits n
229 BL -> reverseBits n
272− LB -> id
231+ LL -> id
275-- | Generic readWord
234-- | Generic readWord
276−readWord :: (Num a, Bits a, FastBits a) => Int -> S -> a
235+readWord :: (Num a, FastBits a) => Int -> S -> a
277readWord n (S bs o bo)
236readWord n (S bs o bo)
278 | n == 0 = 0
237 | n == 0 = 0
279 | otherwise = extract bo (unsafeTake nbytes bs) o n
238 | otherwise = extract bo (unsafeTake nbytes bs) o n
@@ -281,7 +240,7 @@ readWord n (S bs o bo)
282-- | Check that the number of bits to read is not greater than the first parameter
241-- | Check that the number of bits to read is not greater than the first parameter
283{-# INLINE readWordChecked #-}
242{-# INLINE readWordChecked #-}
284−readWordChecked :: (Num a, Bits a, FastBits a) => Int -> Int -> S -> a
243+readWordChecked :: (Num a, FastBits a) => Int -> Int -> S -> a
285readWordChecked m n s
244readWordChecked m n s
286 | n > m = error $ "Tried to read more than " ++ show m ++ " bits (" ++ show n ++")"
245 | n > m = error $ "Tried to read more than " ++ show m ++ " bits (" ++ show n ++")"
287 | otherwise = readWord n s
246 | otherwise = readWord n s
@@ -290,22 +249,23 @@ readWordChecked m n s
291-- Examples:
250-- Examples:
292-- BB: xxxABCDE FGHIJKLM NOPxxxxx -> ABCDEFGH IJKLMNOP
251-- BB: xxxABCDE FGHIJKLM NOPxxxxx -> ABCDEFGH IJKLMNOP
293−-- LB: LMNOPxxx DEFGHIJK xxxxxABC -> ABCDEFGH IJKLMNOP
252+-- LL: LMNOPxxx DEFGHIJK xxxxxABC -> ABCDEFGH IJKLMNOP
294-- BL: xxxPONML KJIHGFED CBAxxxxx -> ABCDEFGH IJKLMNOP
253-- BL: xxxPONML KJIHGFED CBAxxxxx -> ABCDEFGH IJKLMNOP
295−-- LL: EDCBAxxx MLKJIHGF xxxxxPON -> ABCDEFGH IJKLMNOP
254+-- LB: EDCBAxxx MLKJIHGF xxxxxPON -> ABCDEFGH IJKLMNOP
296readByteString :: Int -> S -> ByteString
255readByteString :: Int -> S -> ByteString
297readByteString n (S bs o bo) =
256readByteString n (S bs o bo) =
299− bs' = unsafeTake (n+1) bs
258+ bs' = unsafeTake (n+1) bs
259+ bs'' = unsafeTake n bs
300− rev = B.map (reverseBits 8)
260+ rev = B.map (reverseBits 8)
301 in case (o,bo) of
261 in case (o,bo) of
302− (0,BB) -> unsafeTake n bs
262+ (0,BB) -> bs''
303− (0,LB) -> B.reverse (unsafeTake n bs)
263+ (0,LL) -> B.reverse bs''
304− (0,BL) -> rev (unsafeTake n bs)
264+ (0,LB) -> rev bs''
305− (0,LL) -> rev (B.reverse (unsafeTake n bs))
265+ (0,BL) -> rev . B.reverse $ bs''
306− (_,BL) -> rev (readByteString n (S (B.reverse bs') o LB))
266+ (_,LL) -> readByteString n (S (B.reverse bs') (8-o) BB)
307− (_,LL) -> rev (readByteString n (S (B.reverse bs') o BB))
267+ (_,BL) -> rev . B.reverse $ readByteString n (S bs' o BB)
308− (_,LB) -> readByteString n (S (B.reverse bs') o BB)
268+ (_,LB) -> rev . B.reverse $ readByteString n (S bs' o LL)
309 (_,BB) -> unsafePerformIO $ do
269 (_,BB) -> unsafePerformIO $ do
310 let len = n+1
270 let len = n+1
311 ptr <- mallocBytes len
271 ptr <- mallocBytes len
@@ -327,7 +287,6 @@ newtype BitGet a = B { runState :: S -> Get (S,a) }
328instance Monad BitGet where
288instance Monad BitGet where
329 return x = B $ \s -> return (s,x)
289 return x = B $ \s -> return (s,x)
330− fail str = B $ \s -> putBackState s >> fail str
331 (B f) >>= g = B $ \s -> do (s',a) <- f s
290 (B f) >>= g = B $ \s -> do (s',a) <- f s
332 runState (g a) s'
291 runState (g a) s'
@@ -338,6 +297,29 @@ instance Applicative BitGet where
338 pure x = return x
297 pure x = return x
339 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
341-- | 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
342-- been partially consumed it will be discarded once 'runBitGet' is finished.
324-- been partially consumed it will be discarded once 'runBitGet' is finished.
343runBitGet :: BitGet a -> Get a
325runBitGet :: BitGet a -> Get a
@@ -372,13 +354,6 @@ withState f = do
372 s <- getState
354 s <- getState
373 putState $! f s
355 putState $! f s
375−-- | Get the bit ordering
376−getBitOrder :: BitGet BitOrder
378− (S _ _ bo) <- getState
382-- | Make sure there are at least @n@ bits.
357-- | Make sure there are at least @n@ bits.
383ensureBits :: Int -> BitGet ()
358ensureBits :: Int -> BitGet ()
384ensureBits n = do
359ensureBits n = do
@@ -392,33 +367,6 @@ ensureBits n = do
392 put B.empty
367 put B.empty
393 return (S (bs`append`bs') o bo, ())
368 return (S (bs`append`bs') o bo, ())
395−-- | Skip the given number of bits
396−skipBits :: Int -> BitGet ()
401−-- | Skip bits if necessary to align to the next byte
402−alignByte :: BitGet ()
404− (S _ o _) <- getState
408−-- | Select the bit ordering
409−selectBitOrder :: BitOrder -> BitGet ()
410−selectBitOrder = withState . selectBitOrderS
412−withBitOrder :: BitOrder -> BitGet a -> BitGet a
413−withBitOrder bo f = do
422-- | Test whether all input has been consumed, i.e. there are no remaining
370-- | Test whether all input has been consumed, i.e. there are no remaining
423-- undecoded bytes.
371-- undecoded bytes.
424isEmpty :: BitGet Bool
372isEmpty :: BitGet Bool
@@ -430,6 +378,10 @@ isEmpty = B $ \ (S bs o bo) -> if B.null bs
430getBool :: BitGet Bool
378getBool :: BitGet Bool
431getBool = block bool
379getBool = block bool
381+-- | Get 1 bit as a 'Bool'.
382+getBool# :: BitGet Int
383+getBool# = block bool#
433-- | 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]@.
434getWord8 :: Int -> BitGet Word8
386getWord8 :: Int -> BitGet Word8
435getWord8 n = block (word8 n)
387getWord8 n = block (word8 n)
@@ -505,6 +457,10 @@ block (Block i p) = do
505bool :: Block Bool
457bool :: Block Bool
506bool = Block 1 readBool
458bool = Block 1 readBool
460+-- | Read a 1 bit 'Bool'.
462+bool# = Block 1 readBool#
508-- | 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]@.
509word8 :: Int -> Block Word8
465word8 :: Int -> Block Word8
510word8 n = Block n (readWordChecked 8 n)
466word8 n = Block n (readWordChecked 8 n)
@@ -538,84 +494,3 @@ byteString :: Int -> Block ByteString
538byteString n | n > 0 = Block (n*8) (readByteString n)
494byteString n | n > 0 = Block (n*8) (readByteString n)
539 | otherwise = Block 0 (\_ -> B.empty)
495 | otherwise = Block 0 (\_ -> B.empty)
542−---------------------------------------------------------------------
543−-- Unchecked shifts, from the "binary" package
545−-- | Class for types supporting fast bit shifting
546−class FastBits a where
547− fastShiftR :: a -> Int -> a
548− fastShiftL :: a -> Int -> a
550− {-# INLINE fastShift #-}
551− fastShift :: a -> Int -> a
553− | n > 0 = fastShiftL x n
554− | n < 0 = fastShiftR x (negate n)
557−instance FastBits Word8 where
558− fastShiftR = shiftr_w8
559− fastShiftL = shiftl_w8
561−instance FastBits Word16 where
562− fastShiftR = shiftr_w16
563− fastShiftL = shiftl_w16
565−instance FastBits Word32 where
566− fastShiftR = shiftr_w32
567− fastShiftL = shiftl_w32
569−instance FastBits Word64 where
570− fastShiftR = shiftr_w64
571− fastShiftL = shiftl_w64
574−shiftl_w8 :: Word8 -> Int -> Word8
575−shiftl_w16 :: Word16 -> Int -> Word16
576−shiftl_w32 :: Word32 -> Int -> Word32
577−shiftl_w64 :: Word64 -> Int -> Word64
579−shiftr_w8 :: Word8 -> Int -> Word8
580−shiftr_w16 :: Word16 -> Int -> Word16
581−shiftr_w32 :: Word32 -> Int -> Word32
582−shiftr_w64 :: Word64 -> Int -> Word64
584−#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
585−shiftl_w8 (W8# w) (I# i) = W8# (w `uncheckedShiftL#` i)
586−shiftl_w16 (W16# w) (I# i) = W16# (w `uncheckedShiftL#` i)
587−shiftl_w32 (W32# w) (I# i) = W32# (w `uncheckedShiftL#` i)
589−shiftr_w8 (W8# w) (I# i) = W8# (w `uncheckedShiftRL#` i)
590−shiftr_w16 (W16# w) (I# i) = W16# (w `uncheckedShiftRL#` i)
591−shiftr_w32 (W32# w) (I# i) = W32# (w `uncheckedShiftRL#` i)
594−#if WORD_SIZE_IN_BITS < 64
595−shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL64#` i)
596−shiftr_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftRL64#` i)
598−#if __GLASGOW_HASKELL__ <= 606
599−-- Exported by GHC.Word in GHC 6.8 and higher
600−foreign import ccall unsafe "stg_uncheckedShiftL64"
601− uncheckedShiftL64# :: Word64# -> Int# -> Word64#
602−foreign import ccall unsafe "stg_uncheckedShiftRL64"
603− uncheckedShiftRL64# :: Word64# -> Int# -> Word64#
607−shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL#` i)
608−shiftr_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftRL#` i)