big boi rewrite

haskell · Jun 16, 2020 · 17e7c3a · 17e7c3a
1 parent 10f4255
commit 17e7c3a
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diff --git a/.travis.yml b/.travis.yml
@@ -2,9 +2,13 @@
 #
 #   haskell-ci 'base16-bytestring.cabal'
 #
+# To regenerate the script (for example after adjusting tested-with) run
+#
+#   haskell-ci regenerate
+#
 # For more information, see https://github.com/haskell-CI/haskell-ci
 #
-# version: 0.9.20200406
+# version: 0.10.1
 #
 version: ~> 1.0
 language: c
@@ -162,5 +166,5 @@ script:
   - rm -f cabal.project.local
   - ${CABAL} v2-build $WITHCOMPILER --disable-tests --disable-benchmarks all
 
-# REGENDATA ("0.9.20200406",["base16-bytestring.cabal"])
+# REGENDATA ("0.10.1",["base16-bytestring.cabal"])
 # EOF
diff --git a/Data/ByteString/Base16.hs b/Data/ByteString/Base16.hs
@@ -1,32 +1,39 @@
-{-# LANGUAGE BangPatterns, MagicHash #-}
-
+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE MagicHash #-}
 -- |
 -- Module      : Data.ByteString.Base16
 -- Copyright   : (c) 2011 MailRank, Inc.
 --
 -- License     : BSD
--- Maintainer  : bos@serpentine.com
+-- Maintainer  : Herbert Valerio Riedel <hvr@gnu.org>,
+--               Mikhail Glushenkov <mikhail.glushenkov@gmail.com>,
+--               Emily Pillmore <emilypi@cohomolo.gy>
 -- Stability   : experimental
 -- Portability : GHC
 --
 -- Fast and efficient encoding and decoding of base16-encoded strings.
-
+--
 module Data.ByteString.Base16
-    (
-      encode
-    , decode
-    ) where
+( encode
+, decode
+, decodeLenient
+) where
+
+import Data.ByteString (empty)
+import Data.ByteString.Base16.Internal
+import Data.ByteString.Internal
+
+import Foreign.ForeignPtr
+import Foreign.Ptr
+
+import GHC.ForeignPtr
+#if __GLASGOW_HASKELL__ >= 702
+import System.IO.Unsafe (unsafeDupablePerformIO)
+#else
+import GHC.IO (unsafeDupablePerformIO)
+#endif
 
-import Data.ByteString.Char8 (empty)
-import Data.ByteString.Internal (ByteString(..), createAndTrim', unsafeCreate)
-import Data.Bits (shiftL)
-import Foreign.ForeignPtr (ForeignPtr, withForeignPtr)
-import Foreign.Ptr (Ptr, minusPtr, plusPtr)
-import Foreign.Storable (peek, poke)
-import System.IO.Unsafe (unsafePerformIO)
-import GHC.Prim
-import GHC.Types
-import GHC.Word
 
 -- | Encode a string into base16 form.  The result will always be a
 -- multiple of 2 bytes in length.
@@ -37,108 +44,46 @@ import GHC.Word
 encode :: ByteString -> ByteString
 encode (PS sfp soff slen)
     | slen > maxBound `div` 2 =
-        error "Data.ByteString.Base16.encode: input too long"
-    | otherwise = unsafeCreate (slen*2) $ \dptr ->
-                    withForeignPtr sfp $ \sptr ->
-                      enc (sptr `plusPtr` soff) dptr
- where
-  enc sptr = go sptr where
-    e = sptr `plusPtr` slen
-    go s d | s == e = return ()
-           | otherwise = do
-      x <- peek8 s
-      poke d (tlookup tableHi x)
-      poke (d `plusPtr` 1) (tlookup tableLo x)
-      go (s `plusPtr` 1) (d `plusPtr` 2)
-    tlookup :: Addr# -> Int -> Word8
-    tlookup table (I# index) = W8# (indexWord8OffAddr# table index)
-    !tableLo =
-      "\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
-      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66"#
-    !tableHi =
-      "\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\
-      \\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\
-      \\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\
-      \\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\
-      \\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\
-      \\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\
-      \\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\
-      \\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\
-      \\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\
-      \\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\
-      \\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\
-      \\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\
-      \\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\
-      \\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\
-      \\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\
-      \\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66"#
+      error "Data.ByteString.Base16.encode: input too long"
+    | otherwise = unsafeCreate (slen * 2) $ \dptr ->
+        withForeignPtr sfp $ \sptr ->
+          encodeLoop dptr
+          (sptr `plusPtr` soff)
+          (sptr `plusPtr` (soff + slen))
 
--- | Decode a string from base16 form. The first element of the
--- returned tuple contains the decoded data. The second element starts
--- at the first invalid base16 sequence in the original string.
+-- | Decode a base16-encoded 'ByteString' value.
 --
--- Examples:
+-- If errors are encountered during the decoding process,
+-- then they will be returned in the @Left@ clause of the
+-- coproduct.
 --
--- > decode "666f6f"  == ("foo", "")
--- > decode "66quux"  == ("f", "quux")
--- > decode "666quux" == ("f", "6quux")
-decode :: ByteString -> (ByteString, ByteString)
-decode (PS sfp soff slen) =
-  unsafePerformIO . createAndTrim' (slen `div` 2) $ \dptr ->
-      withForeignPtr sfp $ \sptr ->
-        dec (sptr `plusPtr` soff) dptr
- where
-  dec sptr = go sptr where
-    e = sptr `plusPtr` if odd slen then slen - 1 else slen
-    go s d | s == e = let len = e `minusPtr` sptr
-                      in return (0, len `div` 2, ps sfp (soff+len) (slen-len))
-           | otherwise = do
-      hi <- hex `fmap` peek8 s
-      lo <- hex `fmap` peek8 (s `plusPtr` 1)
-      if lo == 0xff || hi == 0xff
-        then let len = s `minusPtr` sptr
-             in return (0, len `div` 2, ps sfp (soff+len) (slen-len))
-        else do
-          poke d . fromIntegral $ lo + (hi `shiftL` 4)
-          go (s `plusPtr` 2) (d `plusPtr` 1)
-
-    hex (I# index) = W8# (indexWord8OffAddr# table index)
-    !table =
-        "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\xff\xff\xff\xff\xff\xff\
-        \\xff\x0a\x0b\x0c\x0d\x0e\x0f\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\x0a\x0b\x0c\x0d\x0e\x0f\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\
-        \\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"#
+decode :: ByteString -> Either String ByteString
+decode (PS sfp soff slen)
+    | slen == 0 = Right empty
+    | r /= 0 = Left "invalid bytestring size"
+    | otherwise = unsafeDupablePerformIO $ do
+      dfp <- mallocPlainForeignPtrBytes q
+      withForeignPtr dfp $ \dptr ->
+        withForeignPtr sfp $ \sptr ->
+          decodeLoop dfp dptr
+          (plusPtr sptr soff)
+          (plusPtr sptr (soff + slen))
+  where
+    !q = slen `quot` 2
+    !r = slen `rem` 2
 
-peek8 :: Ptr Word8 -> IO Int
-peek8 p = fromIntegral `fmap` peek p
-
-ps :: ForeignPtr Word8 -> Int -> Int -> ByteString
-ps fp off len
-    | len <= 0 = empty
-    | otherwise = PS fp off len
+decodeLenient :: ByteString -> ByteString
+decodeLenient (PS !sfp !soff !slen)
+  | slen == 0 = empty
+  | otherwise = unsafeDupablePerformIO $ do
+    dfp <- mallocPlainForeignPtrBytes dlen
+    withForeignPtr dfp $ \dptr ->
+      withForeignPtr sfp $ \sptr ->
+        lenientLoop
+          dfp
+          dptr
+          (plusPtr sptr soff)
+          (plusPtr sptr (soff + slen))
+  where
+    !q = slen `quot` 2
+    !dlen = q * 2
diff --git a/Data/ByteString/Base16/Internal.hs b/Data/ByteString/Base16/Internal.hs
@@ -0,0 +1,158 @@
+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE MagicHash #-}
+module Data.ByteString.Base16.Internal
+( -- * worker loops
+  encodeLoop
+, decodeLoop
+, lenientLoop
+  -- * utils
+, c2w
+, aix
+, reChunk
+, unsafeShiftR
+) where
+
+
+import Data.Bits ((.&.), (.|.))
+import qualified Data.ByteString as B
+import Data.ByteString.Internal (ByteString(..))
+import Data.Char (ord)
+
+import Foreign.ForeignPtr
+import Foreign.Ptr
+import Foreign.Storable
+
+import GHC.Word
+import GHC.Exts
+  (Int(I#), Addr#, indexWord8OffAddr#, word2Int#, uncheckedShiftRL#)
+
+
+-- ------------------------------------------------------------------ --
+-- Loops
+
+encodeLoop
+    :: Ptr Word8
+    -> Ptr Word8
+    -> Ptr Word8
+    -> IO ()
+encodeLoop !dptr !sptr !end = go dptr sptr
+  where
+    !hex = "0123456789abcdef"#
+
+    go !dst !src
+      | src == end = return ()
+      | otherwise = do
+        !t <- peek src
+
+        poke dst (aix (unsafeShiftR t 4) hex)
+        poke (plusPtr dst 1) (aix (t .&. 0x0f) hex)
+
+        go (plusPtr dst 2) (plusPtr src 1)
+{-# INLINE encodeLoop #-}
+
+decodeLoop
+  :: ForeignPtr Word8
+  -> Ptr Word8
+  -> Ptr Word8
+  -> Ptr Word8
+  -> IO (Either String ByteString)
+decodeLoop !dfp !dptr !sptr !end = go dptr sptr
+  where
+    err !src = return . Left
+      $ "invalid character at offset: "
+      ++ show (src `minusPtr` sptr)
+
+    !lo = "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\xff\xff\xff\xff\xff\xff\xff\x0a\x0b\x0c\x0d\x0e\x0f\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x0a\x0b\x0c\x0d\x0e\x0f\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"#
+
+    !hi = "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00\x10\x20\x30\x40\x50\x60\x70\x80\x90\xff\xff\xff\xff\xff\xff\xff\xa0\xb0\xc0\xd0\xe0\xf0\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xa0\xb0\xc0\xd0\xe0\xf0\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"#
+
+    go !dst !src
+      | src == end = return (Right (PS dfp 0 (src `minusPtr` sptr)))
+      | otherwise = do
+        !x <- peek src
+        !y <- peek (plusPtr src 1)
+
+        let !a = aix x hi
+            !b = aix y lo
+
+        if a == 0xff
+        then err src
+        else
+          if b == 0xff
+          then err (plusPtr src 1)
+          else do
+            poke dst (a .|. b)
+            go (plusPtr dst 1) (plusPtr src 2)
+{-# INLINE decodeLoop #-}
+
+lenientLoop
+  :: ForeignPtr Word8
+  -> Ptr Word8
+  -> Ptr Word8
+  -> Ptr Word8
+  -> IO ByteString
+lenientLoop !dfp !dptr !sptr !end = goHi dptr sptr 0
+  where
+    !lo = "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\xff\xff\xff\xff\xff\xff\xff\x0a\x0b\x0c\x0d\x0e\x0f\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x0a\x0b\x0c\x0d\x0e\x0f\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"#
+
+    !hi = "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00\x10\x20\x30\x40\x50\x60\x70\x80\x90\xff\xff\xff\xff\xff\xff\xff\xa0\xb0\xc0\xd0\xe0\xf0\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xa0\xb0\xc0\xd0\xe0\xf0\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"#
+
+    goHi !dst !src !n
+      | src == end = return (PS dfp 0 n)
+      | otherwise = do
+        !x <- peek src
+
+        let !a = aix x hi
+
+        if a == 0xff
+        then goHi dst (plusPtr src 1) n
+        else goLo dst (plusPtr src 1) a n
+
+    goLo !dst !src !a !n
+      | src == end = return (PS dfp 0 n)
+      | otherwise = do
+        !y <- peek src
+
+        let !b = aix y lo
+
+        if b == 0xff
+        then goLo dst (plusPtr src 1) a n
+        else do
+          poke dst (a .|. b)
+          goHi (plusPtr dst 1) (plusPtr src 1) (n + 1)
+{-# LANGUAGE lenientLoop #-}
+
+
+-- ------------------------------------------------------------------ --
+-- Utils
+
+aix :: Word8 -> Addr# -> Word8
+aix (W8# w) table = W8# (indexWord8OffAddr# table (word2Int# w))
+{-# INLINE aix #-}
+
+-- | Form a list of chunks, and rechunk the list of bytestrings
+-- into length multiples of 2
+--
+reChunk :: [ByteString] -> [ByteString]
+reChunk [] = []
+reChunk (c:cs) = case B.length c `divMod` 2 of
+    (_, 0) -> c : reChunk cs
+    (n, _) -> case B.splitAt (n * 2) c of
+      ~(m, q) -> m : cont_ q cs
+  where
+    cont_ q [] = [q]
+    cont_ q (a:as) = case B.splitAt 1 a of
+      ~(x, y) -> let q' = B.append q x
+        in if B.length q' == 2
+          then
+            let as' = if B.null y then as else y:as
+            in q' : reChunk as'
+          else cont_ q' as
+
+unsafeShiftR :: Word8 -> Int -> Word8
+unsafeShiftR (W8# x#) (I# i#) = W8# (x# `uncheckedShiftRL#` i#)
+{-# INLINE unsafeShiftR #-}
+
+c2w :: Char -> Word8
+c2w = fromIntegral . ord
+{-# INLINE c2w #-}