Add ByteString version of Attoparsec

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 _ = ""