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Diffstat (limited to 'vendor/attoparsec-0.10.4.0/Data/Attoparsec/ByteString/FastSet.hs')
| -rw-r--r-- | vendor/attoparsec-0.10.4.0/Data/Attoparsec/ByteString/FastSet.hs | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/vendor/attoparsec-0.10.4.0/Data/Attoparsec/ByteString/FastSet.hs b/vendor/attoparsec-0.10.4.0/Data/Attoparsec/ByteString/FastSet.hs new file mode 100644 index 00000000..73d02056 --- /dev/null +++ b/vendor/attoparsec-0.10.4.0/Data/Attoparsec/ByteString/FastSet.hs @@ -0,0 +1,115 @@ +{-# LANGUAGE BangPatterns, MagicHash #-} + +----------------------------------------------------------------------------- +-- | +-- Module : Data.Attoparsec.ByteString.FastSet +-- Copyright : Bryan O'Sullivan 2008 +-- License : BSD3 +-- +-- Maintainer : bos@serpentine.com +-- Stability : experimental +-- Portability : unknown +-- +-- Fast set membership tests for 'Word8' and 8-bit 'Char' values. The +-- set representation is unboxed for efficiency. For small sets, we +-- test for membership using a binary search. For larger sets, we use +-- a lookup table. +-- +----------------------------------------------------------------------------- +module Data.Attoparsec.ByteString.FastSet + ( + -- * Data type + FastSet + -- * Construction + , fromList + , set + -- * Lookup + , memberChar + , memberWord8 + -- * Debugging + , fromSet + -- * Handy interface + , charClass + ) where + +import Data.Bits ((.&.), (.|.)) +import Foreign.Storable (peekByteOff, pokeByteOff) +import GHC.Base (Int(I#), iShiftRA#, narrow8Word#, shiftL#) +import GHC.Word (Word8(W8#)) +import qualified Data.ByteString as B +import qualified Data.ByteString.Char8 as B8 +import qualified Data.ByteString.Internal as I +import qualified Data.ByteString.Unsafe as U + +data FastSet = Sorted { fromSet :: !B.ByteString } + | Table { fromSet :: !B.ByteString } + deriving (Eq, Ord) + +instance Show FastSet where + show (Sorted s) = "FastSet Sorted " ++ show (B8.unpack s) + show (Table _) = "FastSet Table" + +-- | The lower bound on the size of a lookup table. We choose this to +-- balance table density against performance. +tableCutoff :: Int +tableCutoff = 8 + +-- | Create a set. +set :: B.ByteString -> FastSet +set s | B.length s < tableCutoff = Sorted . B.sort $ s + | otherwise = Table . mkTable $ s + +fromList :: [Word8] -> FastSet +fromList = set . B.pack + +data I = I {-# UNPACK #-} !Int {-# UNPACK #-} !Word8 + +shiftR :: Int -> Int -> Int +shiftR (I# x#) (I# i#) = I# (x# `iShiftRA#` i#) + +shiftL :: Word8 -> Int -> Word8 +shiftL (W8# x#) (I# i#) = W8# (narrow8Word# (x# `shiftL#` i#)) + +index :: Int -> I +index i = I (i `shiftR` 3) (1 `shiftL` (i .&. 7)) +{-# INLINE index #-} + +-- | Check the set for membership. +memberWord8 :: Word8 -> FastSet -> Bool +memberWord8 w (Table t) = + let I byte bit = index (fromIntegral w) + in U.unsafeIndex t byte .&. bit /= 0 +memberWord8 w (Sorted s) = search 0 (B.length s - 1) + where search lo hi + | hi < lo = False + | otherwise = + let mid = (lo + hi) `div` 2 + in case compare w (U.unsafeIndex s mid) of + GT -> search (mid + 1) hi + LT -> search lo (mid - 1) + _ -> True + +-- | Check the set for membership. Only works with 8-bit characters: +-- characters above code point 255 will give wrong answers. +memberChar :: Char -> FastSet -> Bool +memberChar c = memberWord8 (I.c2w c) +{-# INLINE memberChar #-} + +mkTable :: B.ByteString -> B.ByteString +mkTable s = I.unsafeCreate 32 $ \t -> do + _ <- I.memset t 0 32 + U.unsafeUseAsCStringLen s $ \(p, l) -> + let loop n | n == l = return () + | otherwise = do + c <- peekByteOff p n :: IO Word8 + let I byte bit = index (fromIntegral c) + prev <- peekByteOff t byte :: IO Word8 + pokeByteOff t byte (prev .|. bit) + loop (n + 1) + in loop 0 + +charClass :: String -> FastSet +charClass = set . B8.pack . go + where go (a:'-':b:xs) = [a..b] ++ go xs + go (x:xs) = x : go xs + go _ = "" |