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diff --git a/src/Data/ByteString/Base32.hi b/src/Data/ByteString/Base32.hi
new file mode 100644
index 0000000..ce22b69
--- /dev/null
+++ b/src/Data/ByteString/Base32.hi
diff --git a/src/Data/ByteString/Base32.hs b/src/Data/ByteString/Base32.hs
new file mode 100644
index 0000000..96bb893
--- /dev/null
+++ b/src/Data/ByteString/Base32.hs
@@ -0,0 +1,269 @@
+-- |
+--   Copyright   :  (c) Sam Truzjan 2013
+--   License     :  BSD3
+--   Maintainer  :  pxqr.sta@gmail.com
+--   Stability   :  stable
+--   Portability :  portable
+--
+--   Efficient encoding and decoding of base32 encoded bytestring
+--   according to RFC 4648. <http://tools.ietf.org/html/rfc4648>
+--
+--   This module recommended to be imported as
+--   @import Data.ByteString.Base32 as Base32@ to avoid name clashes
+--   with @Data.Binary@ or @Data.ByteString.Base64@ modules.
+--
+{-# LANGUAGE BangPatterns #-}
+module Data.ByteString.Base32
+       ( encode
+       , decode
+       , decodeLenient
+       ) where
+
+import Data.Bits.Extras
+import Data.ByteString as BS
+import Data.ByteString.Internal as BS
+import Data.Word
+import Foreign   hiding (unsafePerformIO)
+import System.IO.Unsafe (unsafePerformIO)
+import System.Endian
+
+
+{-----------------------------------------------------------------------
+-- Utils
+-----------------------------------------------------------------------}
+
+type Word5 = Word8
+
+-- System.Endian.toBE32 is slower because toBE32 implemented using
+-- cbits shuffle functions while toBE32' implemented used gcc
+-- intrinsics
+--
+toBE64' :: Word64 -> Word64
+toBE64' = if getSystemEndianness == BigEndian then id else byteSwap
+{-# INLINE toBE64' #-}
+
+toBE32' :: Word32 -> Word32
+toBE32' = if getSystemEndianness == BigEndian then id else byteSwap
+{-# INLINE toBE32' #-}
+
+fromBE32' :: Word32 -> Word32
+fromBE32' = toBE32'
+{-# INLINE fromBE32' #-}
+
+-- n = 2 ^ d
+padCeilN :: Int -> Int -> Int
+padCeilN !n !x
+  | remd == 0 = x
+  | otherwise = (x - remd) + n
+  where  mask = n - 1
+         remd = x .&. mask
+
+{-----------------------------------------------------------------------
+-- Encoding
+-----------------------------------------------------------------------}
+
+type EncTable = Ptr Word8
+
+unpack5 :: EncTable -> ByteString -> ByteString
+unpack5 !tbl bs @ (PS fptr off sz) =
+  unsafePerformIO $ do
+    let unpackedSize = dstSize $ BS.length bs
+    BS.create unpackedSize $ \ dst -> do
+        withForeignPtr fptr $ \ ptr -> do
+          dst_end <- bigStep dst (advancePtr ptr off) sz
+          _ <- fillPadding dst_end (unpackedSize - (dst_end `minusPtr` dst))
+          return ()
+  where
+    dstSize x = padCeilN 8 (d + if m == 0 then 0 else 1)
+      where (d, m) = (x * 8) `quotRem` 5
+
+    fillPadding dst s = memset dst (c2w '=') (fromIntegral s)
+
+    bigStep !dst !src !s
+      |     s >= 5  = do
+        unpack5_40 dst src
+        bigStep (dst `advancePtr` 8) (src `advancePtr` 5) (s - 5)
+      |   otherwise  = smallStep dst src s 0 0
+
+    unpack5_40 !dst !src = do
+      w32he <- peek (castPtr src) :: IO Word32
+      let w32 = toBE32' w32he
+      fill8_32 0 (w32 `unsafeShiftR` 27)
+      fill8_32 1 (w32 `unsafeShiftR` 22)
+      fill8_32 2 (w32 `unsafeShiftR` 17)
+      fill8_32 3 (w32 `unsafeShiftR` 12)
+      fill8_32 4 (w32 `unsafeShiftR` 7)
+      fill8_32 5 (w32 `unsafeShiftR` 2)
+
+      w8 <- peekElemOff src 4
+      fill8_32 6 (             (w32 `unsafeShiftL` 3)
+              .|. fromIntegral (w8  `unsafeShiftR` 5))
+      fill8_32 7 (fromIntegral w8)
+     where
+      fill8_32 :: Int -> Word32 -> IO ()
+      fill8_32 !i !w32 = do
+        w8 <- peekByteOff tbl (fromIntegral w32 .&. 0x1f)
+        poke (dst `advancePtr` i) w8
+
+    smallStep !dst !src !s !unused !un_cnt
+      | un_cnt >= 5 = do
+        let ix = unused `unsafeShiftR` 3
+        peekByteOff tbl (fromIntegral ix) >>= poke dst
+        smallStep (advancePtr dst 1)
+                  src s
+                 (unused `unsafeShiftL` 5)
+                 (un_cnt - 5)
+
+      |    s == 0   = do
+        if un_cnt == 0
+          then return dst
+          else do
+            let ix = unused `unsafeShiftR` 3
+            peekByteOff tbl (fromIntegral ix) >>= poke dst
+            return (dst `advancePtr` 1)
+
+      |  otherwise  = do
+        w8 <- peek src
+        let usd_cnt = 5 - un_cnt
+        let bits    = w8 .&. complement (bit (8 - usd_cnt) - 1)
+        let ix = (unused .|. bits `shiftR` un_cnt) `unsafeShiftR` 3
+        peekByteOff tbl (fromIntegral ix) >>= poke dst
+        smallStep (advancePtr dst 1)
+                  (advancePtr src 1) (pred s)
+                  (w8 `shiftL` usd_cnt) (8 - usd_cnt)
+
+encW5 :: Word5 -> Word8
+encW5 !x
+  |  x <= 25  = 65 + x
+  | otherwise = 24 + x
+{-# INLINE encW5 #-}
+
+encTable :: ForeignPtr Word8
+PS encTable _ _ = BS.pack $ fmap encW5 [0..31]
+
+-- | Encode a bytestring into base32 form.
+encode :: ByteString -> ByteString
+encode bs =
+  unsafePerformIO $ do
+    withForeignPtr encTable $ \ptr -> do
+      return $ unpack5 ptr bs
+
+{-----------------------------------------------------------------------
+-- Decoding
+-----------------------------------------------------------------------}
+
+type DecTable = Ptr Word5
+
+pack5 :: DecTable -> (Word8 -> Word5) -> ByteString -> ByteString
+pack5 !tbl !f bs @ (PS fptr off sz) =
+  unsafePerformIO $ do
+    let packedSize = dstSize $ BS.length bs
+    BS.createAndTrim packedSize $ \ dst -> do
+        withForeignPtr fptr $ \ ptr -> do
+          dst_end <- bigStep dst (advancePtr ptr off) sz
+          return (dst_end `minusPtr` dst)
+  where
+    lookupTable :: Word8 -> Word5
+    lookupTable ix
+        | x == invIx = error $ "base32: decode: invalid character" ++ show ix
+        | otherwise  = x
+      where x = inlinePerformIO (peekByteOff tbl (fromIntegral ix))
+    {-# INLINE lookupTable #-}
+
+    dstSize x = d + if m == 0 then 0 else 1
+      where (d, m) = (x * 5) `quotRem` 8
+
+    bigStep !dst !src !s
+      | s > 8 = do
+        pack5_40 dst src
+        bigStep (dst `advancePtr` 5) (src `advancePtr` 8) (s - 8)
+      | otherwise = smallStep dst src s (0 :: Word64) 0
+
+    pack5_40 !dst !src = do
+        w64he <- peek (castPtr src) :: IO Word64
+        let w64 = toBE64' w64he
+        let w40 = putAsW5 (w64 `unsafeShiftR` 00) $
+                  putAsW5 (w64 `unsafeShiftR` 08) $
+                  putAsW5 (w64 `unsafeShiftR` 16) $
+                  putAsW5 (w64 `unsafeShiftR` 24) $
+                  putAsW5 (w64 `unsafeShiftR` 32) $
+                  putAsW5 (w64 `unsafeShiftR` 40) $
+                  putAsW5 (w64 `unsafeShiftR` 48) $
+                  putAsW5 (w64 `unsafeShiftR` 56) 0
+        pokeW40 w40
+      where
+        putAsW5 :: Word64 -> Word64 -> Word64
+        {-# INLINE putAsW5 #-}
+        putAsW5 !w8 !acc = (acc `unsafeShiftL` 5)
+                       .|. fromIntegral (lookupTable (fromIntegral w8))
+
+        pokeW40 :: Word64 -> IO ()
+        {-# INLINE pokeW40 #-}
+        pokeW40 !w40 = do
+          poke dst (fromIntegral (w40 `unsafeShiftR` 32) :: Word8)
+          poke (castPtr (dst `advancePtr` 1))
+               (fromBE32' (fromIntegral w40 :: Word32))
+
+    smallStep !dst !src !s !unused !un_cnt
+      | un_cnt >= 8 = do
+        poke dst $ fromIntegral (unused `unsafeShiftR` (un_cnt - 8))
+        smallStep (dst `advancePtr` 1) src s unused (un_cnt - 8)
+
+      |   s == 0  = return dst
+      | otherwise = do
+        w8 <- peek src
+        if w2c w8 == '='
+           then if (bit un_cnt - 1) .&. unused == 0
+                then smallStep dst src 0 0 0
+                else smallStep dst src 0 (unused `shiftL` (8 - un_cnt)) 8
+           else smallStep dst
+                  (src `advancePtr` 1) (pred s)
+                  ((unused `unsafeShiftL` 5) .|. fromIntegral (f w8))
+                  (un_cnt + 5)
+
+invIx :: Word5
+invIx = 255
+
+decW5 :: Word8 -> Word5
+decW5 !x
+  | x <  50 {- c2w '2' -} = invIx
+  | x <= 55 {- c2w '7' -} = x - 24
+  | x <  65 {- c2w 'A' -} = invIx
+  | x <= 90 {- c2w 'Z' -} = x - 65
+  |       otherwise       = invIx
+{-# INLINE decW5 #-}
+
+decTable :: ForeignPtr Word8
+PS decTable _ _ = BS.pack $ fmap decW5 [minBound .. maxBound]
+
+-- | Decode a base32 encoded bytestring.
+decode :: ByteString -> ByteString
+decode bs =
+  unsafePerformIO $ do
+    withForeignPtr decTable $ \tbl ->
+      return $ pack5 tbl decW5 bs
+
+{-----------------------------------------------------------------------
+-- Lenient Decoding
+-----------------------------------------------------------------------}
+
+decCharLenient :: Char -> Word5
+decCharLenient x
+  | x <  '2'  = err
+  | x <= '7'  = 26 + fromIntegral (fromEnum x) - fromIntegral (fromEnum '2')
+  | x <  'A'  = err
+  | x <= 'Z'  = fromIntegral (fromEnum x) - fromIntegral (fromEnum 'A')
+  | x <  'a'  = err
+  | x <= 'z'  = fromIntegral (fromEnum x) - fromIntegral (fromEnum 'a')
+  | otherwise = err
+  where
+    err = error "base32: decodeChar: out of range"
+
+decW5Lenient :: Word8 -> Word5
+decW5Lenient = decCharLenient . w2c
+{-# INLINE decW5Lenient #-}
+
+-- TODO padding leniency
+-- | Case-insensitive counterpart of the 'decode'.
+decodeLenient :: ByteString -> ByteString
+decodeLenient = id -- pack5 nullPtr decW5Lenient
\ No newline at end of file
diff --git a/src/Data/ByteString/Base32.o b/src/Data/ByteString/Base32.o
new file mode 100644
index 0000000..eadc3fe
--- /dev/null
+++ b/src/Data/ByteString/Base32.o