From 43d159c841fbfd04355460639b7320e4e5f62813 Mon Sep 17 00:00:00 2001
From: Edward Kmett <ekmett@gmail.com>
Date: Wed, 5 Jun 2019 17:03:49 -0400
Subject: [PATCH] Use plusForeignPtr (Close #174)

---
 Data/ByteString.hs                            | 233 +++++++++---------
 Data/ByteString/Builder/Internal.hs           |  10 +-
 Data/ByteString/Builder/Prim.hs               |   6 +-
 .../Builder/Prim/Internal/Base16.hs           |   2 +-
 Data/ByteString/Char8.hs                      |  16 +-
 Data/ByteString/Internal.hs                   | 171 +++++++++----
 Data/ByteString/Lazy.hs                       |  14 +-
 Data/ByteString/Lazy/Internal.hs              |   8 +-
 Data/ByteString/Short/Internal.hs             |   9 +-
 Data/ByteString/Unsafe.hs                     |  40 +--
 bytestring.cabal                              |   2 +-
 tests/Hash.hs                                 |  13 +-
 tests/Words.hs                                |  10 +-
 tests/test-compare.hs                         |  15 +-
 tests/unpack.hs                               |   4 +-
 15 files changed, 309 insertions(+), 244 deletions(-)

diff --git a/Data/ByteString.hs b/Data/ByteString.hs
index 8d80d262d..bd29635d8 100644
--- a/Data/ByteString.hs
+++ b/Data/ByteString.hs
@@ -292,7 +292,7 @@ finiteBitSize = bitSize
 
 -- | /O(1)/ The empty 'ByteString'
 empty :: ByteString
-empty = PS nullForeignPtr 0 0
+empty = BS nullForeignPtr 0
 
 -- | /O(1)/ Convert a 'Word8' into a 'ByteString'
 singleton :: Word8 -> ByteString
@@ -349,13 +349,13 @@ unpackFoldr bs k z = foldr k z bs
 
 -- | /O(1)/ Test whether a ByteString is empty.
 null :: ByteString -> Bool
-null (PS _ _ l) = assert (l >= 0) $ l <= 0
+null (BS _ l) = assert (l >= 0) $ l <= 0
 {-# INLINE null #-}
 
 -- ---------------------------------------------------------------------
 -- | /O(1)/ 'length' returns the length of a ByteString as an 'Int'.
 length :: ByteString -> Int
-length (PS _ _ l) = assert (l >= 0) l
+length (BS _ l) = assert (l >= 0) l
 {-# INLINE length #-}
 
 ------------------------------------------------------------------------
@@ -366,15 +366,15 @@ infixl 5 `snoc`
 -- | /O(n)/ 'cons' is analogous to (:) for lists, but of different
 -- complexity, as it requires making a copy.
 cons :: Word8 -> ByteString -> ByteString
-cons c (PS x s l) = unsafeCreate (l+1) $ \p -> withForeignPtr x $ \f -> do
+cons c (BS x l) = unsafeCreate (l+1) $ \p -> withForeignPtr x $ \f -> do
         poke p c
-        memcpy (p `plusPtr` 1) (f `plusPtr` s) (fromIntegral l)
+        memcpy (p `plusPtr` 1) f (fromIntegral l)
 {-# INLINE cons #-}
 
 -- | /O(n)/ Append a byte to the end of a 'ByteString'
 snoc :: ByteString -> Word8 -> ByteString
-snoc (PS x s l) c = unsafeCreate (l+1) $ \p -> withForeignPtr x $ \f -> do
-        memcpy p (f `plusPtr` s) (fromIntegral l)
+snoc (BS x l) c = unsafeCreate (l+1) $ \p -> withForeignPtr x $ \f -> do
+        memcpy p f (fromIntegral l)
         poke (p `plusPtr` l) c
 {-# INLINE snoc #-}
 
@@ -383,54 +383,54 @@ snoc (PS x s l) c = unsafeCreate (l+1) $ \p -> withForeignPtr x $ \f -> do
 -- | /O(1)/ Extract the first element of a ByteString, which must be non-empty.
 -- An exception will be thrown in the case of an empty ByteString.
 head :: ByteString -> Word8
-head (PS x s l)
+head (BS x l)
     | l <= 0    = errorEmptyList "head"
-    | otherwise = accursedUnutterablePerformIO $ withForeignPtr x $ \p -> peekByteOff p s
+    | otherwise = accursedUnutterablePerformIO $ withForeignPtr x $ \p -> peek p
 {-# INLINE head #-}
 
 -- | /O(1)/ Extract the elements after the head of a ByteString, which must be non-empty.
 -- An exception will be thrown in the case of an empty ByteString.
 tail :: ByteString -> ByteString
-tail (PS p s l)
+tail (BS p l)
     | l <= 0    = errorEmptyList "tail"
-    | otherwise = PS p (s+1) (l-1)
+    | otherwise = BS (plusForeignPtr p 1) (l-1)
 {-# INLINE tail #-}
 
 -- | /O(1)/ Extract the head and tail of a ByteString, returning Nothing
 -- if it is empty.
 uncons :: ByteString -> Maybe (Word8, ByteString)
-uncons (PS x s l)
+uncons (BS x l)
     | l <= 0    = Nothing
     | otherwise = Just (accursedUnutterablePerformIO $ withForeignPtr x
-                                                     $ \p -> peekByteOff p s,
-                        PS x (s+1) (l-1))
+                                                     $ \p -> peek p,
+                        BS (plusForeignPtr x 1) (l-1))
 {-# INLINE uncons #-}
 
 -- | /O(1)/ Extract the last element of a ByteString, which must be finite and non-empty.
 -- An exception will be thrown in the case of an empty ByteString.
 last :: ByteString -> Word8
-last ps@(PS x s l)
+last ps@(BS x l)
     | null ps   = errorEmptyList "last"
     | otherwise = accursedUnutterablePerformIO $
-                    withForeignPtr x $ \p -> peekByteOff p (s+l-1)
+                    withForeignPtr x $ \p -> peekByteOff p (l-1)
 {-# INLINE last #-}
 
 -- | /O(1)/ Return all the elements of a 'ByteString' except the last one.
 -- An exception will be thrown in the case of an empty ByteString.
 init :: ByteString -> ByteString
-init ps@(PS p s l)
+init ps@(BS p l)
     | null ps   = errorEmptyList "init"
-    | otherwise = PS p s (l-1)
+    | otherwise = BS p (l-1)
 {-# INLINE init #-}
 
 -- | /O(1)/ Extract the 'init' and 'last' of a ByteString, returning Nothing
 -- if it is empty.
 unsnoc :: ByteString -> Maybe (ByteString, Word8)
-unsnoc (PS x s l)
+unsnoc (BS x l)
     | l <= 0    = Nothing
-    | otherwise = Just (PS x s (l-1),
+    | otherwise = Just (BS x (l-1),
                         accursedUnutterablePerformIO $
-                          withForeignPtr x $ \p -> peekByteOff p (s+l-1))
+                          withForeignPtr x $ \p -> peekByteOff p (l-1))
 {-# INLINE unsnoc #-}
 
 -- | /O(n)/ Append two ByteStrings
@@ -444,8 +444,8 @@ append = mappend
 -- | /O(n)/ 'map' @f xs@ is the ByteString obtained by applying @f@ to each
 -- element of @xs@.
 map :: (Word8 -> Word8) -> ByteString -> ByteString
-map f (PS fp s len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a ->
-    create len $ map_ 0 (a `plusPtr` s)
+map f (BS fp len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a ->
+    create len $ map_ 0 a
   where
     map_ :: Int -> Ptr Word8 -> Ptr Word8 -> IO ()
     map_ !n !p1 !p2
@@ -458,18 +458,18 @@ map f (PS fp s len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a ->
 
 -- | /O(n)/ 'reverse' @xs@ efficiently returns the elements of @xs@ in reverse order.
 reverse :: ByteString -> ByteString
-reverse (PS x s l) = unsafeCreate l $ \p -> withForeignPtr x $ \f ->
-        c_reverse p (f `plusPtr` s) (fromIntegral l)
+reverse (BS x l) = unsafeCreate l $ \p -> withForeignPtr x $ \f ->
+        c_reverse p f (fromIntegral l)
 
 -- | /O(n)/ The 'intersperse' function takes a 'Word8' and a
 -- 'ByteString' and \`intersperses\' that byte between the elements of
 -- the 'ByteString'.  It is analogous to the intersperse function on
 -- Lists.
 intersperse :: Word8 -> ByteString -> ByteString
-intersperse c ps@(PS x s l)
+intersperse c ps@(BS x l)
     | length ps < 2  = ps
     | otherwise      = unsafeCreate (2*l-1) $ \p -> withForeignPtr x $ \f ->
-        c_intersperse p (f `plusPtr` s) (fromIntegral l) c
+        c_intersperse p f (fromIntegral l) c
 
 -- | The 'transpose' function transposes the rows and columns of its
 -- 'ByteString' argument.
@@ -484,9 +484,9 @@ transpose ps = P.map pack . List.transpose . P.map unpack $ ps
 -- ByteString using the binary operator, from left to right.
 --
 foldl :: (a -> Word8 -> a) -> a -> ByteString -> a
-foldl f z (PS fp off len) =
+foldl f z (BS fp len) =
       let p = unsafeForeignPtrToPtr fp
-       in go (p `plusPtr` (off+len-1)) (p `plusPtr` (off-1))
+       in go (p `plusPtr` (len-1)) (p `plusPtr` (-1))
     where
       -- not tail recursive; traverses array right to left
       go !p !q | p == q    = z
@@ -500,9 +500,9 @@ foldl f z (PS fp off len) =
 -- | 'foldl'' is like 'foldl', but strict in the accumulator.
 --
 foldl' :: (a -> Word8 -> a) -> a -> ByteString -> a
-foldl' f v (PS fp off len) =
+foldl' f v (BS fp len) =
       accursedUnutterablePerformIO $ withForeignPtr fp $ \p ->
-        go v (p `plusPtr` off) (p `plusPtr` (off+len))
+        go v p (p `plusPtr` len)
     where
       -- tail recursive; traverses array left to right
       go !z !p !q | p == q    = return z
@@ -514,9 +514,9 @@ foldl' f v (PS fp off len) =
 -- (typically the right-identity of the operator), and a ByteString,
 -- reduces the ByteString using the binary operator, from right to left.
 foldr :: (Word8 -> a -> a) -> a -> ByteString -> a
-foldr k z (PS fp off len) =
+foldr k z (BS fp len) =
       let p = unsafeForeignPtrToPtr fp
-       in go (p `plusPtr` off) (p `plusPtr` (off+len))
+       in go p (p `plusPtr` len)
     where
       -- not tail recursive; traverses array left to right
       go !p !q | p == q    = z
@@ -529,9 +529,9 @@ foldr k z (PS fp off len) =
 
 -- | 'foldr'' is like 'foldr', but strict in the accumulator.
 foldr' :: (Word8 -> a -> a) -> a -> ByteString -> a
-foldr' k v (PS fp off len) =
+foldr' k v (BS fp len) =
       accursedUnutterablePerformIO $ withForeignPtr fp $ \p ->
-        go v (p `plusPtr` (off+len-1)) (p `plusPtr` (off-1))
+        go v (p `plusPtr` (len-1)) (p `plusPtr` (-1))
     where
       -- tail recursive; traverses array right to left
       go !z !p !q | p == q    = return z
@@ -589,9 +589,9 @@ concatMap f = concat . foldr ((:) . f) []
 -- | /O(n)/ Applied to a predicate and a ByteString, 'any' determines if
 -- any element of the 'ByteString' satisfies the predicate.
 any :: (Word8 -> Bool) -> ByteString -> Bool
-any _ (PS _ _ 0) = False
-any f (PS x s l) = accursedUnutterablePerformIO $ withForeignPtr x $ \ptr ->
-        go (ptr `plusPtr` s) (ptr `plusPtr` (s+l))
+any _ (BS _ 0) = False
+any f (BS x l) = accursedUnutterablePerformIO $ withForeignPtr x $ \ptr ->
+        go ptr (ptr `plusPtr` l)
     where
         go !p !q | p == q    = return False
                  | otherwise = do c <- peek p
@@ -604,9 +604,9 @@ any f (PS x s l) = accursedUnutterablePerformIO $ withForeignPtr x $ \ptr ->
 -- | /O(n)/ Applied to a predicate and a 'ByteString', 'all' determines
 -- if all elements of the 'ByteString' satisfy the predicate.
 all :: (Word8 -> Bool) -> ByteString -> Bool
-all _ (PS _ _ 0) = True
-all f (PS x s l) = accursedUnutterablePerformIO $ withForeignPtr x $ \ptr ->
-        go (ptr `plusPtr` s) (ptr `plusPtr` (s+l))
+all _ (BS _ 0) = True
+all f (BS x l) = accursedUnutterablePerformIO $ withForeignPtr x $ \ptr ->
+        go ptr (ptr `plusPtr` l)
     where
         go !p !q | p == q     = return True  -- end of list
                  | otherwise  = do c <- peek p
@@ -621,20 +621,20 @@ all f (PS x s l) = accursedUnutterablePerformIO $ withForeignPtr x $ \ptr ->
 -- This function will fuse.
 -- An exception will be thrown in the case of an empty ByteString.
 maximum :: ByteString -> Word8
-maximum xs@(PS x s l)
+maximum xs@(BS x l)
     | null xs   = errorEmptyList "maximum"
     | otherwise = accursedUnutterablePerformIO $ withForeignPtr x $ \p ->
-                      c_maximum (p `plusPtr` s) (fromIntegral l)
+                      c_maximum p (fromIntegral l)
 {-# INLINE maximum #-}
 
 -- | /O(n)/ 'minimum' returns the minimum value from a 'ByteString'
 -- This function will fuse.
 -- An exception will be thrown in the case of an empty ByteString.
 minimum :: ByteString -> Word8
-minimum xs@(PS x s l)
+minimum xs@(BS x l)
     | null xs   = errorEmptyList "minimum"
     | otherwise = accursedUnutterablePerformIO $ withForeignPtr x $ \p ->
-                      c_minimum (p `plusPtr` s) (fromIntegral l)
+                      c_minimum p (fromIntegral l)
 {-# INLINE minimum #-}
 
 ------------------------------------------------------------------------
@@ -644,10 +644,10 @@ minimum xs@(PS x s l)
 -- passing an accumulating parameter from left to right, and returning a
 -- final value of this accumulator together with the new list.
 mapAccumL :: (acc -> Word8 -> (acc, Word8)) -> acc -> ByteString -> (acc, ByteString)
-mapAccumL f acc (PS fp o len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a -> do
+mapAccumL f acc (BS fp len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a -> do
     gp   <- mallocByteString len
-    acc' <- withForeignPtr gp $ \p -> mapAccumL_ acc 0 (a `plusPtr` o) p
-    return (acc', PS gp 0 len)
+    acc' <- withForeignPtr gp $ \p -> mapAccumL_ acc 0 a p
+    return (acc', BS gp len)
   where
     mapAccumL_ !s !n !p1 !p2
        | n >= len = return s
@@ -663,10 +663,10 @@ mapAccumL f acc (PS fp o len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a
 -- passing an accumulating parameter from right to left, and returning a
 -- final value of this accumulator together with the new ByteString.
 mapAccumR :: (acc -> Word8 -> (acc, Word8)) -> acc -> ByteString -> (acc, ByteString)
-mapAccumR f acc (PS fp o len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a -> do
+mapAccumR f acc (BS fp len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a -> do
     gp   <- mallocByteString len
-    acc' <- withForeignPtr gp $ \p -> mapAccumR_ acc (len-1) (a `plusPtr` o) p
-    return $! (acc', PS gp 0 len)
+    acc' <- withForeignPtr gp $ \p -> mapAccumR_ acc (len-1) a p
+    return $! (acc', BS gp len)
   where
     mapAccumR_ !s !n !p !q
        | n <  0    = return s
@@ -691,10 +691,10 @@ mapAccumR f acc (PS fp o len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a
 --
 scanl :: (Word8 -> Word8 -> Word8) -> Word8 -> ByteString -> ByteString
 
-scanl f v (PS fp s len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a ->
+scanl f v (BS fp len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a ->
     create (len+1) $ \q -> do
         poke q v
-        scanl_ v 0 (a `plusPtr` s) (q `plusPtr` 1)
+        scanl_ v 0 a (q `plusPtr` 1)
   where
     scanl_ !z !n !p !q
         | n >= len  = return ()
@@ -721,10 +721,10 @@ scanl1 f ps
 
 -- | scanr is the right-to-left dual of scanl.
 scanr :: (Word8 -> Word8 -> Word8) -> Word8 -> ByteString -> ByteString
-scanr f v (PS fp s len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a ->
+scanr f v (BS fp len) = unsafeDupablePerformIO $ withForeignPtr fp $ \a ->
     create (len+1) $ \q -> do
         poke (q `plusPtr` len) v
-        scanr_ v (len-1) (a `plusPtr` s) q
+        scanr_ v (len-1) a q
   where
     scanr_ !z !n !p !q
         | n <  0    = return ()
@@ -806,27 +806,27 @@ unfoldrN i f x0
 -- | /O(1)/ 'take' @n@, applied to a ByteString @xs@, returns the prefix
 -- of @xs@ of length @n@, or @xs@ itself if @n > 'length' xs@.
 take :: Int -> ByteString -> ByteString
-take n ps@(PS x s l)
+take n ps@(BS x l)
     | n <= 0    = empty
     | n >= l    = ps
-    | otherwise = PS x s n
+    | otherwise = BS x n
 {-# INLINE take #-}
 
 -- | /O(1)/ 'drop' @n xs@ returns the suffix of @xs@ after the first @n@
 -- elements, or @[]@ if @n > 'length' xs@.
 drop  :: Int -> ByteString -> ByteString
-drop n ps@(PS x s l)
+drop n ps@(BS x l)
     | n <= 0    = ps
     | n >= l    = empty
-    | otherwise = PS x (s+n) (l-n)
+    | otherwise = BS (plusForeignPtr x n) (l-n)
 {-# INLINE drop #-}
 
 -- | /O(1)/ 'splitAt' @n xs@ is equivalent to @('take' n xs, 'drop' n xs)@.
 splitAt :: Int -> ByteString -> (ByteString, ByteString)
-splitAt n ps@(PS x s l)
+splitAt n ps@(BS x l)
     | n <= 0    = (empty, ps)
     | n >= l    = (ps, empty)
-    | otherwise = (PS x s n, PS x (s+n) (l-n))
+    | otherwise = (BS x n, BS (plusForeignPtr x n) (l-n))
 {-# INLINE splitAt #-}
 
 -- | 'takeWhile', applied to a predicate @p@ and a ByteString @xs@,
@@ -906,10 +906,10 @@ span p ps = break (not . p) ps
 -- > span  (=='c') "abcd" == spanByte 'c' "abcd"
 --
 spanByte :: Word8 -> ByteString -> (ByteString, ByteString)
-spanByte c ps@(PS x s l) =
+spanByte c ps@(BS x l) =
     accursedUnutterablePerformIO $
       withForeignPtr x $ \p ->
-        go (p `plusPtr` s) 0
+        go p 0
   where
     go !p !i | i >= l    = return (ps, empty)
              | otherwise = do c' <- peekByteOff p i
@@ -958,8 +958,8 @@ spanEnd  p ps = splitAt (findFromEndUntil (not.p) ps) ps
 -- > splitWith (=='a') []        == []
 --
 splitWith :: (Word8 -> Bool) -> ByteString -> [ByteString]
-splitWith _pred (PS _  _   0) = []
-splitWith pred_ (PS fp off len) = splitWith0 pred# off len fp
+splitWith _pred (BS _  0) = []
+splitWith pred_ (BS fp len) = splitWith0 pred# 0 len fp
   where pred# c# = pred_ (W8# c#)
 
         splitWith0 !pred' !off' !len' !fp' =
@@ -974,11 +974,11 @@ splitWith pred_ (PS fp off len) = splitWith0 pred# off len fp
                   -> IO [ByteString]
 
         splitLoop pred' p idx' off' len' fp'
-            | idx' >= len'  = return [PS fp' off' idx']
+            | idx' >= len'  = return [BS (plusForeignPtr fp' off') idx']
             | otherwise = do
                 w <- peekElemOff p (off'+idx')
                 if pred' (case w of W8# w# -> w#)
-                   then return (PS fp' off' idx' :
+                   then return (BS (plusForeignPtr fp' off') idx' :
                               splitWith0 pred' (off'+idx'+1) (len'-idx'-1) fp')
                    else splitLoop pred' p (idx'+1) off' len' fp'
 {-# INLINE splitWith #-}
@@ -1000,18 +1000,18 @@ splitWith pred_ (PS fp off len) = splitWith0 pred# off len fp
 -- are slices of the original.
 --
 split :: Word8 -> ByteString -> [ByteString]
-split _ (PS _ _ 0) = []
-split w (PS x s l) = loop 0
+split _ (BS _ 0) = []
+split w (BS x l) = loop 0
     where
         loop !n =
             let q = accursedUnutterablePerformIO $ withForeignPtr x $ \p ->
-                      memchr (p `plusPtr` (s+n))
+                      memchr (p `plusPtr` n)
                              w (fromIntegral (l-n))
             in if q == nullPtr
-                then [PS x (s+n) (l-n)]
+                then [BS (plusForeignPtr x n) (l-n)]
                 else let i = accursedUnutterablePerformIO $ withForeignPtr x $ \p ->
-                               return (q `minusPtr` (p `plusPtr` s))
-                      in PS x (s+n) (i-n) : loop (i+1)
+                               return (q `minusPtr` p)
+                      in BS (plusForeignPtr x n) (i-n) : loop (i+1)
 
 {-# INLINE split #-}
 
@@ -1057,12 +1057,12 @@ intercalate s = concat . List.intersperse s
 -- with a char. Around 4 times faster than the generalised join.
 --
 intercalateWithByte :: Word8 -> ByteString -> ByteString -> ByteString
-intercalateWithByte c f@(PS ffp s l) g@(PS fgp t m) = unsafeCreate len $ \ptr ->
+intercalateWithByte c f@(BS ffp l) g@(BS fgp m) = unsafeCreate len $ \ptr ->
     withForeignPtr ffp $ \fp ->
     withForeignPtr fgp $ \gp -> do
-        memcpy ptr (fp `plusPtr` s) (fromIntegral l)
+        memcpy ptr fp (fromIntegral l)
         poke (ptr `plusPtr` l) c
-        memcpy (ptr `plusPtr` (l + 1)) (gp `plusPtr` t) (fromIntegral m)
+        memcpy (ptr `plusPtr` (l + 1)) gp (fromIntegral m)
     where
       len = length f + length g + 1
 {-# INLINE intercalateWithByte #-}
@@ -1084,10 +1084,9 @@ index ps n
 -- element, or 'Nothing' if there is no such element.
 -- This implementation uses memchr(3).
 elemIndex :: Word8 -> ByteString -> Maybe Int
-elemIndex c (PS x s l) = accursedUnutterablePerformIO $ withForeignPtr x $ \p -> do
-    let p' = p `plusPtr` s
-    q <- memchr p' c (fromIntegral l)
-    return $! if q == nullPtr then Nothing else Just $! q `minusPtr` p'
+elemIndex c (BS x l) = accursedUnutterablePerformIO $ withForeignPtr x $ \p -> do
+    q <- memchr p c (fromIntegral l)
+    return $! if q == nullPtr then Nothing else Just $! q `minusPtr` p
 {-# INLINE elemIndex #-}
 
 -- | /O(n)/ The 'elemIndexEnd' function returns the last index of the
@@ -1099,8 +1098,8 @@ elemIndex c (PS x s l) = accursedUnutterablePerformIO $ withForeignPtr x $ \p ->
 -- > (-) (length xs - 1) `fmap` elemIndex c (reverse xs)
 --
 elemIndexEnd :: Word8 -> ByteString -> Maybe Int
-elemIndexEnd ch (PS x s l) = accursedUnutterablePerformIO $ withForeignPtr x $ \p ->
-    go (p `plusPtr` s) (l-1)
+elemIndexEnd ch (BS x l) = accursedUnutterablePerformIO $ withForeignPtr x $ \p ->
+    go p (l-1)
   where
     go !p !i | i < 0     = return Nothing
              | otherwise = do ch' <- peekByteOff p i
@@ -1113,15 +1112,15 @@ elemIndexEnd ch (PS x s l) = accursedUnutterablePerformIO $ withForeignPtr x $ \
 -- the indices of all elements equal to the query element, in ascending order.
 -- This implementation uses memchr(3).
 elemIndices :: Word8 -> ByteString -> [Int]
-elemIndices w (PS x s l) = loop 0
+elemIndices w (BS x l) = loop 0
     where
         loop !n = let q = accursedUnutterablePerformIO $ withForeignPtr x $ \p ->
-                           memchr (p `plusPtr` (n+s))
+                           memchr (p `plusPtr` n)
                                                 w (fromIntegral (l - n))
                   in if q == nullPtr
                         then []
                         else let i = accursedUnutterablePerformIO $ withForeignPtr x $ \p ->
-                                       return (q `minusPtr` (p `plusPtr` s))
+                                       return (q `minusPtr` p)
                              in i : loop (i+1)
 {-# INLINE elemIndices #-}
 
@@ -1131,15 +1130,15 @@ elemIndices w (PS x s l) = loop 0
 --
 -- But more efficiently than using length on the intermediate list.
 count :: Word8 -> ByteString -> Int
-count w (PS x s m) = accursedUnutterablePerformIO $ withForeignPtr x $ \p ->
-    fmap fromIntegral $ c_count (p `plusPtr` s) (fromIntegral m) w
+count w (BS x m) = accursedUnutterablePerformIO $ withForeignPtr x $ \p ->
+    fmap fromIntegral $ c_count p (fromIntegral m) w
 {-# INLINE count #-}
 
 -- | The 'findIndex' function takes a predicate and a 'ByteString' and
 -- returns the index of the first element in the ByteString
 -- satisfying the predicate.
 findIndex :: (Word8 -> Bool) -> ByteString -> Maybe Int
-findIndex k (PS x s l) = accursedUnutterablePerformIO $ withForeignPtr x $ \f -> go (f `plusPtr` s) 0
+findIndex k (BS x l) = accursedUnutterablePerformIO $ withForeignPtr x $ \f -> go f 0
   where
     go !ptr !n | n >= l    = return Nothing
                | otherwise = do w <- peek ptr
@@ -1174,10 +1173,10 @@ notElem c ps = not (elem c ps)
 -- returns a ByteString containing those characters that satisfy the
 -- predicate.
 filter :: (Word8 -> Bool) -> ByteString -> ByteString
-filter k ps@(PS x s l)
+filter k ps@(BS x l)
     | null ps   = ps
     | otherwise = unsafePerformIO $ createAndTrim l $ \p -> withForeignPtr x $ \f -> do
-        t <- go (f `plusPtr` s) p (f `plusPtr` (s + l))
+        t <- go f p (f `plusPtr` l)
         return $! t `minusPtr` p -- actual length
     where
         go !f !t !end | f == end  = return t
@@ -1237,8 +1236,8 @@ partition f s = unsafeDupablePerformIO $
               mid <- sep 0 p end
               rev mid end
               let i = mid `minusPtr` p
-              return (PS fp' 0 i,
-                      PS fp' i (len - i))
+              return (BS fp' i,
+                      BS (plusForeignPtr fp' i) (len - i))
   where
     len  = length s
     incr = (`plusPtr` 1)
@@ -1267,12 +1266,12 @@ partition f s = unsafeDupablePerformIO $
 -- |/O(n)/ The 'isPrefixOf' function takes two ByteStrings and returns 'True'
 -- if the first is a prefix of the second.
 isPrefixOf :: ByteString -> ByteString -> Bool
-isPrefixOf (PS x1 s1 l1) (PS x2 s2 l2)
+isPrefixOf (BS x1 l1) (BS x2 l2)
     | l1 == 0   = True
     | l2 < l1   = False
     | otherwise = accursedUnutterablePerformIO $ withForeignPtr x1 $ \p1 ->
         withForeignPtr x2 $ \p2 -> do
-            i <- memcmp (p1 `plusPtr` s1) (p2 `plusPtr` s2) (fromIntegral l1)
+            i <- memcmp p1 p2 (fromIntegral l1)
             return $! i == 0
 
 -- | /O(n)/ The 'stripPrefix' function takes two ByteStrings and returns 'Just'
@@ -1281,7 +1280,7 @@ isPrefixOf (PS x1 s1 l1) (PS x2 s2 l2)
 --
 -- @since 0.10.8.0
 stripPrefix :: ByteString -> ByteString -> Maybe ByteString
-stripPrefix bs1@(PS _ _ l1) bs2
+stripPrefix bs1@(BS _ l1) bs2
    | bs1 `isPrefixOf` bs2 = Just (unsafeDrop l1 bs2)
    | otherwise = Nothing
 
@@ -1295,19 +1294,19 @@ stripPrefix bs1@(PS _ _ l1) bs2
 -- However, the real implemenation uses memcmp to compare the end of the
 -- string only, with no reverse required..
 isSuffixOf :: ByteString -> ByteString -> Bool
-isSuffixOf (PS x1 s1 l1) (PS x2 s2 l2)
+isSuffixOf (BS x1 l1) (BS x2 l2)
     | l1 == 0   = True
     | l2 < l1   = False
     | otherwise = accursedUnutterablePerformIO $ withForeignPtr x1 $ \p1 ->
         withForeignPtr x2 $ \p2 -> do
-            i <- memcmp (p1 `plusPtr` s1) (p2 `plusPtr` s2 `plusPtr` (l2 - l1)) (fromIntegral l1)
+            i <- memcmp p1 (p2 `plusPtr` (l2 - l1)) (fromIntegral l1)
             return $! i == 0
 
 -- | /O(n)/ The 'stripSuffix' function takes two ByteStrings and returns 'Just'
 -- the remainder of the second iff the first is its suffix, and otherwise
 -- 'Nothing'.
 stripSuffix :: ByteString -> ByteString -> Maybe ByteString
-stripSuffix bs1@(PS _ _ l1) bs2@(PS _ _ l2)
+stripSuffix bs1@(BS _ l1) bs2@(BS _ l2)
    | bs1 `isSuffixOf` bs2 = Just (unsafeTake (l2 - l1) bs2)
    | otherwise = Nothing
 
@@ -1474,10 +1473,10 @@ zipWith f ps qs
 -- performed on the result of zipWith.
 --
 zipWith' :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteString -> ByteString
-zipWith' f (PS fp s l) (PS fq t m) = unsafeDupablePerformIO $
+zipWith' f (BS fp l) (BS fq m) = unsafeDupablePerformIO $
     withForeignPtr fp $ \a ->
     withForeignPtr fq $ \b ->
-    create len $ zipWith_ 0 (a `plusPtr` s) (b `plusPtr` t)
+    create len $ zipWith_ 0 a b
   where
     zipWith_ :: Int -> Ptr Word8 -> Ptr Word8 -> Ptr Word8 -> IO ()
     zipWith_ !n !p1 !p2 !r
@@ -1507,7 +1506,7 @@ unzip ls = (pack (P.map fst ls), pack (P.map snd ls))
 
 -- | /O(n)/ Return all initial segments of the given 'ByteString', shortest first.
 inits :: ByteString -> [ByteString]
-inits (PS x s l) = [PS x s n | n <- [0..l]]
+inits (BS x l) = [BS x n | n <- [0..l]]
 
 -- | /O(n)/ Return all final segments of the given 'ByteString', longest first.
 tails :: ByteString -> [ByteString]
@@ -1521,10 +1520,10 @@ tails p | null p    = [empty]
 
 -- | /O(n)/ Sort a ByteString efficiently, using counting sort.
 sort :: ByteString -> ByteString
-sort (PS input s l) = unsafeCreate l $ \p -> allocaArray 256 $ \arr -> do
+sort (BS input l) = unsafeCreate l $ \p -> allocaArray 256 $ \arr -> do
 
     _ <- memset (castPtr arr) 0 (256 * fromIntegral (sizeOf (undefined :: CSize)))
-    withForeignPtr input (\x -> countOccurrences arr (x `plusPtr` s) l)
+    withForeignPtr input (\x -> countOccurrences arr x l)
 
     let go 256 !_   = return ()
         go i   !ptr = do n <- peekElemOff arr i
@@ -1553,10 +1552,10 @@ sort (PS input s l) = unsafeCreate l $ \p -> allocaArray 256 $ \arr -> do
 -- automatically; it must not be stored or used after the
 -- subcomputation finishes.
 useAsCString :: ByteString -> (CString -> IO a) -> IO a
-useAsCString (PS fp o l) action =
+useAsCString (BS fp l) action =
  allocaBytes (l+1) $ \buf ->
    withForeignPtr fp $ \p -> do
-     memcpy buf (p `plusPtr` o) (fromIntegral l)
+     memcpy buf p (fromIntegral l)
      pokeByteOff buf l (0::Word8)
      action (castPtr buf)
 
@@ -1564,7 +1563,7 @@ useAsCString (PS fp o l) action =
 -- As for @useAsCString@ this function makes a copy of the original @ByteString@.
 -- It must not be stored or used after the subcomputation finishes.
 useAsCStringLen :: ByteString -> (CStringLen -> IO a) -> IO a
-useAsCStringLen p@(PS _ _ l) f = useAsCString p $ \cstr -> f (cstr,l)
+useAsCStringLen p@(BS _ l) f = useAsCString p $ \cstr -> f (cstr,l)
 
 ------------------------------------------------------------------------
 
@@ -1596,8 +1595,8 @@ packCStringLen (_, len) =
 -- is needed in the rest of the program.
 --
 copy :: ByteString -> ByteString
-copy (PS x s l) = unsafeCreate l $ \p -> withForeignPtr x $ \f ->
-    memcpy p (f `plusPtr` s) (fromIntegral l)
+copy (BS x l) = unsafeCreate l $ \p -> withForeignPtr x $ \f ->
+    memcpy p f (fromIntegral l)
 
 -- ---------------------------------------------------------------------
 -- Line IO
@@ -1670,8 +1669,8 @@ mkBigPS _ pss = return $! concat (P.reverse pss)
 
 -- | Outputs a 'ByteString' to the specified 'Handle'.
 hPut :: Handle -> ByteString -> IO ()
-hPut _ (PS _  _ 0) = return ()
-hPut h (PS ps s l) = withForeignPtr ps $ \p-> hPutBuf h (p `plusPtr` s) l
+hPut _ (BS _  0) = return ()
+hPut h (BS ps l) = withForeignPtr ps $ \p-> hPutBuf h p l
 
 -- | Similar to 'hPut' except that it will never block. Instead it returns
 -- any tail that did not get written. This tail may be 'empty' in the case that
@@ -1682,8 +1681,8 @@ hPut h (PS ps s l) = withForeignPtr ps $ \p-> hPutBuf h (p `plusPtr` s) l
 -- function does not work correctly; it behaves identically to 'hPut'.
 --
 hPutNonBlocking :: Handle -> ByteString -> IO ByteString
-hPutNonBlocking h bs@(PS ps s l) = do
-  bytesWritten <- withForeignPtr ps $ \p-> hPutBufNonBlocking h (p `plusPtr` s) l
+hPutNonBlocking h bs@(BS ps l) = do
+  bytesWritten <- withForeignPtr ps $ \p-> hPutBufNonBlocking h p l
   return $! drop bytesWritten bs
 
 -- | A synonym for @hPut@, for compatibility
@@ -1808,7 +1807,7 @@ hGetContentsSizeHint hnd =
     readChunks chunks sz sz' = do
       fp        <- mallocByteString sz
       readcount <- withForeignPtr fp $ \buf -> hGetBuf hnd buf sz
-      let chunk = PS fp 0 readcount
+      let chunk = BS fp readcount
       -- We rely on the hGetBuf behaviour (not hGetBufSome) where it reads up
       -- to the size we ask for, or EOF. So short reads indicate EOF.
       if readcount < sz && sz > 0
@@ -1866,10 +1865,10 @@ appendFile = modifyFile AppendMode
 -- | 'findIndexOrEnd' is a variant of findIndex, that returns the length
 -- of the string if no element is found, rather than Nothing.
 findIndexOrEnd :: (Word8 -> Bool) -> ByteString -> Int
-findIndexOrEnd k (PS x s l) =
+findIndexOrEnd k (BS x l) =
     accursedUnutterablePerformIO $
       withForeignPtr x $ \f ->
-        go (f `plusPtr` s) 0
+        go f 0
   where
     go !ptr !n | n >= l    = return l
                | otherwise = do w <- peek ptr
@@ -1897,7 +1896,7 @@ moduleErrorMsg fun msg = "Data.ByteString." ++ fun ++ ':':' ':msg
 
 -- Find from the end of the string using predicate
 findFromEndUntil :: (Word8 -> Bool) -> ByteString -> Int
-findFromEndUntil f ps@(PS x s l)
+findFromEndUntil f ps@(BS x l)
   | null ps = 0
   | f (unsafeLast ps) = l
-  | otherwise = findFromEndUntil f (PS x s (l - 1))
+  | otherwise = findFromEndUntil f (BS x (l - 1))
diff --git a/Data/ByteString/Builder/Internal.hs b/Data/ByteString/Builder/Internal.hs
index b55e0550d..3fb083052 100644
--- a/Data/ByteString/Builder/Internal.hs
+++ b/Data/ByteString/Builder/Internal.hs
@@ -203,7 +203,7 @@ newBuffer size = do
 {-# INLINE byteStringFromBuffer #-}
 byteStringFromBuffer :: Buffer -> S.ByteString
 byteStringFromBuffer (Buffer fpbuf (BufferRange op _)) =
-    S.PS fpbuf 0 (op `minusPtr` unsafeForeignPtrToPtr fpbuf)
+    S.BS fpbuf (op `minusPtr` unsafeForeignPtrToPtr fpbuf)
 
 -- | Prepend the filled part of a 'Buffer' to a lazy 'L.ByteString'
 -- trimming it if necessary.
@@ -857,7 +857,7 @@ byteStringThreshold :: Int -> S.ByteString -> Builder
 byteStringThreshold maxCopySize =
     \bs -> builder $ step bs
   where
-    step !bs@(S.PS _ _ len) !k br@(BufferRange !op _)
+    step !bs@(S.BS _ len) !k br@(BufferRange !op _)
       | len <= maxCopySize = byteStringCopyStep bs k br
       | otherwise          = return $ insertChunk op bs k
 
@@ -873,7 +873,7 @@ byteStringCopy = \bs -> builder $ byteStringCopyStep bs
 
 {-# INLINE byteStringCopyStep #-}
 byteStringCopyStep :: S.ByteString -> BuildStep a -> BuildStep a
-byteStringCopyStep (S.PS ifp ioff isize) !k0 br0@(BufferRange op ope)
+byteStringCopyStep (S.BS ifp isize) !k0 br0@(BufferRange op ope)
     -- Ensure that the common case is not recursive and therefore yields
     -- better code.
     | op' <= ope = do copyBytes op ip isize
@@ -882,7 +882,7 @@ byteStringCopyStep (S.PS ifp ioff isize) !k0 br0@(BufferRange op ope)
     | otherwise  = do wrappedBytesCopyStep (BufferRange ip ipe) k br0
   where
     op'  = op `plusPtr` isize
-    ip   = unsafeForeignPtrToPtr ifp `plusPtr` ioff
+    ip   = unsafeForeignPtrToPtr ifp
     ipe  = ip `plusPtr` isize
     k br = do touchForeignPtr ifp  -- input consumed: OK to release here
               k0 br
@@ -1147,7 +1147,7 @@ buildStepToCIOS !(AllocationStrategy nextBuffer bufSize trim) =
               -- FIXME: We could reuse the trimmed buffer here.
               return $ Yield1 bs (mkCIOS False)
           | otherwise            =
-              return $ Yield1 (S.PS fpbuf 0 chunkSize) (mkCIOS False)
+              return $ Yield1 (S.BS fpbuf chunkSize) (mkCIOS False)
           where
             chunkSize = op' `minusPtr` pbuf
             size      = pe  `minusPtr` pbuf
diff --git a/Data/ByteString/Builder/Prim.hs b/Data/ByteString/Builder/Prim.hs
index 4dcc150fb..645ab48aa 100644
--- a/Data/ByteString/Builder/Prim.hs
+++ b/Data/ByteString/Builder/Prim.hs
@@ -643,10 +643,10 @@ primMapByteStringBounded w =
     \bs -> builder $ step bs
   where
     bound = I.sizeBound w
-    step (S.PS ifp ioff isize) !k =
-        goBS (unsafeForeignPtrToPtr ifp `plusPtr` ioff)
+    step (S.BS ifp isize) !k =
+        goBS (unsafeForeignPtrToPtr ifp)
       where
-        !ipe = unsafeForeignPtrToPtr ifp `plusPtr` (ioff + isize)
+        !ipe = unsafeForeignPtrToPtr ifp `plusPtr` isize
         goBS !ip0 !br@(BufferRange op0 ope)
           | ip0 >= ipe = do
               touchForeignPtr ifp -- input buffer consumed
diff --git a/Data/ByteString/Builder/Prim/Internal/Base16.hs b/Data/ByteString/Builder/Prim/Internal/Base16.hs
index e27424f07..aa80dd176 100644
--- a/Data/ByteString/Builder/Prim/Internal/Base16.hs
+++ b/Data/ByteString/Builder/Prim/Internal/Base16.hs
@@ -48,7 +48,7 @@ import           Foreign
 newtype EncodingTable = EncodingTable (ForeignPtr Word8)
 
 tableFromList :: [Word8] -> EncodingTable
-tableFromList xs = case S.pack xs of S.PS fp _ _ -> EncodingTable fp
+tableFromList xs = case S.pack xs of S.BS fp _ -> EncodingTable fp
 
 unsafeIndex :: EncodingTable -> Int -> IO Word8
 unsafeIndex (EncodingTable table) = peekElemOff (unsafeForeignPtrToPtr table)
diff --git a/Data/ByteString/Char8.hs b/Data/ByteString/Char8.hs
index 6b1efb32f..761eed9e9 100644
--- a/Data/ByteString/Char8.hs
+++ b/Data/ByteString/Char8.hs
@@ -791,12 +791,12 @@ unsafeHead  = w2c . B.unsafeHead
 -- > break isSpace == breakSpace
 --
 breakSpace :: ByteString -> (ByteString,ByteString)
-breakSpace (PS x s l) = accursedUnutterablePerformIO $ withForeignPtr x $ \p -> do
-    i <- firstspace (p `plusPtr` s) 0 l
+breakSpace (BS x l) = accursedUnutterablePerformIO $ withForeignPtr x $ \p -> do
+    i <- firstspace p 0 l
     return $! case () of {_
-        | i == 0    -> (empty, PS x s l)
-        | i == l    -> (PS x s l, empty)
-        | otherwise -> (PS x s i, PS x (s+i) (l-i))
+        | i == 0    -> (empty, BS x l)
+        | i == l    -> (BS x l, empty)
+        | otherwise -> (BS x i, BS (plusForeignPtr x i) (l-i))
     }
 {-# INLINE breakSpace #-}
 
@@ -813,9 +813,9 @@ firstspace !ptr !n !m
 -- > dropWhile isSpace == dropSpace
 --
 dropSpace :: ByteString -> ByteString
-dropSpace (PS x s l) = accursedUnutterablePerformIO $ withForeignPtr x $ \p -> do
-    i <- firstnonspace (p `plusPtr` s) 0 l
-    return $! if i == l then empty else PS x (s+i) (l-i)
+dropSpace (BS x l) = accursedUnutterablePerformIO $ withForeignPtr x $ \p -> do
+    i <- firstnonspace p 0 l
+    return $! if i == l then empty else BS (plusForeignPtr x i) (l-i)
 {-# INLINE dropSpace #-}
 
 firstnonspace :: Ptr Word8 -> Int -> Int -> IO Int
diff --git a/Data/ByteString/Internal.hs b/Data/ByteString/Internal.hs
index 4e1e19b21..4fbc838ec 100644
--- a/Data/ByteString/Internal.hs
+++ b/Data/ByteString/Internal.hs
@@ -1,6 +1,9 @@
 {-# LANGUAGE CPP, ForeignFunctionInterface, BangPatterns #-}
 {-# LANGUAGE UnliftedFFITypes, MagicHash,
             UnboxedTuples, DeriveDataTypeable #-}
+#if __GLASGOW_HASKELL__ >= 800
+{-# LANGUAGE PatternSynonyms, ViewPatterns #-}
+#endif
 #if __GLASGOW_HASKELL__ >= 703
 {-# LANGUAGE Unsafe #-}
 #endif
@@ -26,7 +29,12 @@
 module Data.ByteString.Internal (
 
         -- * The @ByteString@ type and representation
-        ByteString(..),         -- instances: Eq, Ord, Show, Read, Data, Typeable
+        ByteString
+        ( BS
+#if __GLASGOW_HASKELL__ >= 800
+        , PS -- backwards compatibility shim
+#endif
+        ), -- instances: Eq, Ord, Show, Read, Data, Typeable
 
         -- * Conversion with lists: packing and unpacking
         packBytes, packUptoLenBytes, unsafePackLenBytes,
@@ -47,6 +55,8 @@ module Data.ByteString.Internal (
         -- * Conversion to and from ForeignPtrs
         fromForeignPtr,         -- :: ForeignPtr Word8 -> Int -> Int -> ByteString
         toForeignPtr,           -- :: ByteString -> (ForeignPtr Word8, Int, Int)
+        fromForeignPtr0,        -- :: ForeignPtr Word8 -> Int -> ByteString
+        toForeignPtr0,          -- :: ByteString -> (ForeignPtr Word8, Int)
 
         -- * Utilities
         nullForeignPtr,         -- :: ForeignPtr Word8
@@ -73,7 +83,10 @@ module Data.ByteString.Internal (
 
         -- * Deprecated and unmentionable
         accursedUnutterablePerformIO, -- :: IO a -> a
-        inlinePerformIO               -- :: IO a -> a
+        inlinePerformIO,              -- :: IO a -> a
+
+        -- * Exported compatibility shim
+        plusForeignPtr
   ) where
 
 import Prelude hiding (concat, null)
@@ -103,6 +116,7 @@ import Data.List.NonEmpty       (NonEmpty ((:|)))
 import Data.Monoid              (Monoid(..))
 #endif
 
+
 import Control.DeepSeq          (NFData(rnf))
 
 import Data.String              (IsString(..))
@@ -133,6 +147,13 @@ import GHC.IOBase               (IO(IO),RawBuffer,unsafeDupablePerformIO)
 
 import GHC.ForeignPtr           (ForeignPtr(ForeignPtr)
                                 ,newForeignPtr_, mallocPlainForeignPtrBytes)
+#if MIN_VERSION_base(4,10,0)
+import GHC.ForeignPtr           (plusForeignPtr)
+#else
+import GHC.Types                (Int (..))
+import GHC.Prim                 (plusAddr#)
+#endif
+
 import GHC.Ptr                  (Ptr(..), castPtr)
 
 #if __GLASGOW_HASKELL__ >= 811
@@ -144,6 +165,25 @@ import GHC.ForeignPtr           (ForeignPtrContents(FinalPtr))
 -- CFILES stuff is Hugs only
 {-# CFILES cbits/fpstring.c #-}
 
+#if !MIN_VERSION_base(4,10,0)
+-- |Advances the given address by the given offset in bytes.
+--
+-- The new 'ForeignPtr' shares the finalizer of the original,
+-- equivalent from a finalization standpoint to just creating another
+-- reference to the original. That is, the finalizer will not be
+-- called before the new 'ForeignPtr' is unreachable, nor will it be
+-- called an additional time due to this call, and the finalizer will
+-- be called with the same address that it would have had this call
+-- not happened, *not* the new address.
+plusForeignPtr :: ForeignPtr a -> Int -> ForeignPtr b
+plusForeignPtr (ForeignPtr addr guts) (I# offset) = ForeignPtr (plusAddr# addr offset) guts
+{-# INLINE [0] plusForeignPtr #-}
+{-# RULES
+"ByteString plusForeignPtr/0" forall fp .
+   plusForeignPtr fp 0 = fp
+ #-}
+#endif
+
 -- -----------------------------------------------------------------------------
 
 -- | A space-efficient representation of a 'Word8' vector, supporting many
@@ -153,11 +193,31 @@ import GHC.ForeignPtr           (ForeignPtrContents(FinalPtr))
 -- "Data.ByteString.Char8" it can be interpreted as containing 8-bit
 -- characters.
 --
-data ByteString = PS {-# UNPACK #-} !(ForeignPtr Word8) -- payload
-                     {-# UNPACK #-} !Int                -- offset
+data ByteString = BS {-# UNPACK #-} !(ForeignPtr Word8) -- payload
                      {-# UNPACK #-} !Int                -- length
     deriving (Typeable)
 
+
+#if __GLASGOW_HASKELL__ >= 800
+-- |
+-- @'PS' foreignPtr offset length@ represents a 'ByteString' with data
+-- backed by a given @foreignPtr@, starting at a given @offset@ in bytes
+-- and of a specified @length@.
+--
+-- This pattern is used to emulate the legacy 'ByteString' data
+-- constructor, so that pre-existing code generally doesn't need to
+-- change to benefit from the simplified 'BS' constructor and can
+-- continue to function unchanged.
+--
+-- /Note:/ Matching with this constructor will always be given a 0 'offset',
+-- as the base will be manipulated by 'plusForeignPtr' instead.
+--
+pattern PS :: ForeignPtr Word8 -> Int -> Int -> ByteString
+pattern PS fp zero len <- BS fp (((,) 0) -> (zero, len)) where
+  PS fp o len = BS (plusForeignPtr fp o) len
+{-# COMPLETE PS #-}
+#endif
+
 instance Eq  ByteString where
     (==)    = eq
 
@@ -171,7 +231,7 @@ instance Semigroup ByteString where
 #endif
 
 instance Monoid ByteString where
-    mempty  = PS nullForeignPtr 0 0
+    mempty  = BS nullForeignPtr 0
 #if MIN_VERSION_base(4,9,0)
     mappend = (<>)
 #else
@@ -180,7 +240,7 @@ instance Monoid ByteString where
     mconcat = concat
 
 instance NFData ByteString where
-    rnf PS{} = ()
+    rnf BS{} = ()
 
 instance Show ByteString where
     showsPrec p ps r = showsPrec p (unpackChars ps) r
@@ -253,15 +313,13 @@ unsafePackLenChars len cs0 =
 unsafePackAddress :: Addr# -> IO ByteString
 unsafePackAddress addr# = do
 #if __GLASGOW_HASKELL__ >= 811
-    return $ PS
+    return $ BS
       (accursedUnutterablePerformIO (newForeignPtr_ (Ptr addr#)))
-      0
       (I# (cstringLength# addr#))
 #else
     p <- newForeignPtr_ (castPtr cstr)
     l <- c_strlen cstr
-    let len = fromIntegral l
-    return $ PS p 0 len
+    return $ BS p (fromIntegral l)
   where
     cstr :: CString
     cstr = Ptr addr#
@@ -279,10 +337,10 @@ unsafePackAddress addr# = do
 unsafePackLiteral :: Addr# -> ByteString
 unsafePackLiteral addr# =
 #if __GLASGOW_HASKELL__ >= 811
-  PS (ForeignPtr addr# FinalPtr) 0 (I# (cstringLength# addr#))
+  BS (ForeignPtr addr# FinalPtr) (I# (cstringLength# addr#))
 #else
   let len = accursedUnutterablePerformIO (c_strlen (Ptr addr#))
-   in PS (accursedUnutterablePerformIO (newForeignPtr_ (Ptr addr#))) 0 (fromIntegral len)
+   in BS (accursedUnutterablePerformIO (newForeignPtr_ (Ptr addr#))) (fromIntegral len)
 #endif
 {-# INLINE unsafePackLiteral #-}
 
@@ -321,22 +379,22 @@ unpackChars :: ByteString -> [Char]
 unpackChars bs = unpackAppendCharsLazy bs []
 
 unpackAppendBytesLazy :: ByteString -> [Word8] -> [Word8]
-unpackAppendBytesLazy (PS fp off len) xs
-  | len <= 100 = unpackAppendBytesStrict (PS fp off len) xs
-  | otherwise  = unpackAppendBytesStrict (PS fp off 100) remainder
+unpackAppendBytesLazy (BS fp len) xs
+  | len <= 100 = unpackAppendBytesStrict (BS fp len) xs
+  | otherwise  = unpackAppendBytesStrict (BS fp 100) remainder
   where
-    remainder  = unpackAppendBytesLazy (PS fp (off+100) (len-100)) xs
+    remainder  = unpackAppendBytesLazy (BS (plusForeignPtr fp 100) (len-100)) xs
 
   -- Why 100 bytes you ask? Because on a 64bit machine the list we allocate
   -- takes just shy of 4k which seems like a reasonable amount.
   -- (5 words per list element, 8 bytes per word, 100 elements = 4000 bytes)
 
 unpackAppendCharsLazy :: ByteString -> [Char] -> [Char]
-unpackAppendCharsLazy (PS fp off len) cs
-  | len <= 100 = unpackAppendCharsStrict (PS fp off len) cs
-  | otherwise  = unpackAppendCharsStrict (PS fp off 100) remainder
+unpackAppendCharsLazy (BS fp len) cs
+  | len <= 100 = unpackAppendCharsStrict (BS fp len) cs
+  | otherwise  = unpackAppendCharsStrict (BS fp 100) remainder
   where
-    remainder  = unpackAppendCharsLazy (PS fp (off+100) (len-100)) cs
+    remainder  = unpackAppendCharsLazy (BS (plusForeignPtr fp 100) (len-100)) cs
 
 -- For these unpack functions, since we're unpacking the whole list strictly we
 -- build up the result list in an accumulator. This means we have to build up
@@ -344,9 +402,9 @@ unpackAppendCharsLazy (PS fp off len) cs
 -- buffer and loops down until we hit the sentinal:
 
 unpackAppendBytesStrict :: ByteString -> [Word8] -> [Word8]
-unpackAppendBytesStrict (PS fp off len) xs =
+unpackAppendBytesStrict (BS fp len) xs =
     accursedUnutterablePerformIO $ withForeignPtr fp $ \base ->
-      loop (base `plusPtr` (off-1)) (base `plusPtr` (off-1+len)) xs
+      loop (base `plusPtr` (-1)) (base `plusPtr` (-1+len)) xs
   where
     loop !sentinal !p acc
       | p == sentinal = return acc
@@ -354,9 +412,9 @@ unpackAppendBytesStrict (PS fp off len) xs =
                            loop sentinal (p `plusPtr` (-1)) (x:acc)
 
 unpackAppendCharsStrict :: ByteString -> [Char] -> [Char]
-unpackAppendCharsStrict (PS fp off len) xs =
+unpackAppendCharsStrict (BS fp len) xs =
     accursedUnutterablePerformIO $ withForeignPtr fp $ \base ->
-      loop (base `plusPtr` (off-1)) (base `plusPtr` (off-1+len)) xs
+      loop (base `plusPtr` (-1)) (base `plusPtr` (-1+len)) xs
   where
     loop !sentinal !p acc
       | p == sentinal = return acc
@@ -382,14 +440,25 @@ fromForeignPtr :: ForeignPtr Word8
                -> Int -- ^ Offset
                -> Int -- ^ Length
                -> ByteString
-fromForeignPtr = PS
+fromForeignPtr fp o len = BS (plusForeignPtr fp o) len
 {-# INLINE fromForeignPtr #-}
 
+fromForeignPtr0 :: ForeignPtr Word8
+               -> Int -- ^ Length
+               -> ByteString
+fromForeignPtr0 = BS
+{-# INLINE fromForeignPtr0 #-}
+
 -- | /O(1)/ Deconstruct a ForeignPtr from a ByteString
 toForeignPtr :: ByteString -> (ForeignPtr Word8, Int, Int) -- ^ (ptr, offset, length)
-toForeignPtr (PS ps s l) = (ps, s, l)
+toForeignPtr (BS ps l) = (ps, 0, l)
 {-# INLINE toForeignPtr #-}
 
+-- | /O(1)/ Deconstruct a ForeignPtr from a ByteString
+toForeignPtr0 :: ByteString -> (ForeignPtr Word8, Int) -- ^ (ptr, length)
+toForeignPtr0 (BS ps l) = (ps, l)
+{-# INLINE toForeignPtr0 #-}
+
 -- | A way of creating ByteStrings outside the IO monad. The @Int@
 -- argument gives the final size of the ByteString.
 unsafeCreate :: Int -> (Ptr Word8 -> IO ()) -> ByteString
@@ -413,7 +482,7 @@ create :: Int -> (Ptr Word8 -> IO ()) -> IO ByteString
 create l f = do
     fp <- mallocByteString l
     withForeignPtr fp $ \p -> f p
-    return $! PS fp 0 l
+    return $! BS fp l
 {-# INLINE create #-}
 
 -- | Create ByteString of up to size size @l@ and use action @f@ to fill it's
@@ -422,7 +491,7 @@ createUptoN :: Int -> (Ptr Word8 -> IO Int) -> IO ByteString
 createUptoN l f = do
     fp <- mallocByteString l
     l' <- withForeignPtr fp $ \p -> f p
-    assert (l' <= l) $ return $! PS fp 0 l'
+    assert (l' <= l) $ return $! BS fp l'
 {-# INLINE createUptoN #-}
 
 -- | Create ByteString of up to size @l@ and use action @f@ to fill it's contents which returns its true size.
@@ -430,7 +499,7 @@ createUptoN' :: Int -> (Ptr Word8 -> IO (Int, a)) -> IO (ByteString, a)
 createUptoN' l f = do
     fp <- mallocByteString l
     (l', res) <- withForeignPtr fp $ \p -> f p
-    assert (l' <= l) $ return (PS fp 0 l', res)
+    assert (l' <= l) $ return (BS fp l', res)
 {-# INLINE createUptoN' #-}
 
 -- | Given the maximum size needed and a function to make the contents
@@ -447,7 +516,7 @@ createAndTrim l f = do
     withForeignPtr fp $ \p -> do
         l' <- f p
         if assert (l' <= l) $ l' >= l
-            then return $! PS fp 0 l
+            then return $! BS fp l
             else create l' $ \p' -> memcpy p' p l'
 {-# INLINE createAndTrim #-}
 
@@ -457,7 +526,7 @@ createAndTrim' l f = do
     withForeignPtr fp $ \p -> do
         (off, l', res) <- f p
         if assert (l' <= l) $ l' >= l
-            then return (PS fp 0 l, res)
+            then return (BS fp l, res)
             else do ps <- create l' $ \p' ->
                             memcpy p' (p `plusPtr` off) l'
                     return (ps, res)
@@ -472,32 +541,32 @@ mallocByteString = mallocPlainForeignPtrBytes
 -- Implementations for Eq, Ord and Monoid instances
 
 eq :: ByteString -> ByteString -> Bool
-eq a@(PS fp off len) b@(PS fp' off' len')
-  | len /= len'              = False    -- short cut on length
-  | fp == fp' && off == off' = True     -- short cut for the same string
-  | otherwise                = compareBytes a b == EQ
+eq a@(BS fp len) b@(BS fp' len')
+  | len /= len' = False    -- short cut on length
+  | fp == fp'   = True     -- short cut for the same string
+  | otherwise   = compareBytes a b == EQ
 {-# INLINE eq #-}
 -- ^ still needed
 
 compareBytes :: ByteString -> ByteString -> Ordering
-compareBytes (PS _   _    0)    (PS _   _    0)    = EQ  -- short cut for empty strings
-compareBytes (PS fp1 off1 len1) (PS fp2 off2 len2) =
+compareBytes (BS _   0)    (BS _   0)    = EQ  -- short cut for empty strings
+compareBytes (BS fp1 len1) (BS fp2 len2) =
     accursedUnutterablePerformIO $
       withForeignPtr fp1 $ \p1 ->
       withForeignPtr fp2 $ \p2 -> do
-        i <- memcmp (p1 `plusPtr` off1) (p2 `plusPtr` off2) (min len1 len2)
+        i <- memcmp p1 p2 (min len1 len2)
         return $! case i `compare` 0 of
                     EQ  -> len1 `compare` len2
                     x   -> x
 
 append :: ByteString -> ByteString -> ByteString
-append (PS _   _    0)    b                  = b
-append a                  (PS _   _    0)    = a
-append (PS fp1 off1 len1) (PS fp2 off2 len2) =
+append (BS _   0)    b                  = b
+append a             (BS _   0)    = a
+append (BS fp1 len1) (BS fp2 len2) =
     unsafeCreate (len1+len2) $ \destptr1 -> do
       let destptr2 = destptr1 `plusPtr` len1
-      withForeignPtr fp1 $ \p1 -> memcpy destptr1 (p1 `plusPtr` off1) len1
-      withForeignPtr fp2 $ \p2 -> memcpy destptr2 (p2 `plusPtr` off2) len2
+      withForeignPtr fp1 $ \p1 -> memcpy destptr1 p1 len1
+      withForeignPtr fp2 $ \p2 -> memcpy destptr2 p2 len2
 
 concat :: [ByteString] -> ByteString
 concat = \bss0 -> goLen0 bss0 bss0
@@ -520,26 +589,26 @@ concat = \bss0 -> goLen0 bss0 bss0
   where
     -- It's still possible that the result is empty
     goLen0 _    []                     = mempty
-    goLen0 bss0 (PS _ _ 0     :bss)    = goLen0 bss0 bss
+    goLen0 bss0 (BS _ 0     :bss)    = goLen0 bss0 bss
     goLen0 bss0 (bs           :bss)    = goLen1 bss0 bs bss
 
     -- It's still possible that the result is a single chunk
     goLen1 _    bs []                  = bs
-    goLen1 bss0 bs (PS _ _ 0  :bss)    = goLen1 bss0 bs bss
-    goLen1 bss0 bs (PS _ _ len:bss)    = goLen bss0 (checkedAdd "concat" len' len) bss
-      where PS _ _ len' = bs
+    goLen1 bss0 bs (BS _ 0  :bss)    = goLen1 bss0 bs bss
+    goLen1 bss0 bs (BS _ len:bss)    = goLen bss0 (checkedAdd "concat" len' len) bss
+      where BS _ len' = bs
 
     -- General case, just find the total length we'll need
-    goLen bss0 !total (PS _ _ len:bss) = goLen bss0 total' bss
+    goLen bss0 !total (BS _ len:bss) = goLen bss0 total' bss
       where total' = checkedAdd "concat" total len
     goLen bss0 total [] =
       unsafeCreate total $ \ptr -> goCopy bss0 ptr
 
     -- Copy the data
     goCopy []                  !_   = return ()
-    goCopy (PS _  _   0  :bss) !ptr = goCopy bss ptr
-    goCopy (PS fp off len:bss) !ptr = do
-      withForeignPtr fp $ \p -> memcpy ptr (p `plusPtr` off) len
+    goCopy (BS _  0  :bss) !ptr = goCopy bss ptr
+    goCopy (BS fp len:bss) !ptr = do
+      withForeignPtr fp $ \p -> memcpy ptr p len
       goCopy bss (ptr `plusPtr` len)
 {-# NOINLINE concat #-}
 
diff --git a/Data/ByteString/Lazy.hs b/Data/ByteString/Lazy.hs
index 9157826f2..9a1e9b2e9 100644
--- a/Data/ByteString/Lazy.hs
+++ b/Data/ByteString/Lazy.hs
@@ -309,10 +309,10 @@ toStrict = \cs -> goLen0 cs cs
 
     -- Copy the data
     goCopy Empty                        !_   = return ()
-    goCopy (Chunk (S.PS _  _   0  ) cs) !ptr = goCopy cs ptr
-    goCopy (Chunk (S.PS fp off len) cs) !ptr = do
+    goCopy (Chunk (S.BS _  0  ) cs) !ptr = goCopy cs ptr
+    goCopy (Chunk (S.BS fp len) cs) !ptr = do
       withForeignPtr fp $ \p -> do
-        S.memcpy ptr (p `plusPtr` off) len
+        S.memcpy ptr p len
         goCopy cs (ptr `plusPtr` len)
 -- See the comment on Data.ByteString.Internal.concat for some background on
 -- this implementation.
@@ -464,10 +464,10 @@ intersperse _ Empty        = Empty
 intersperse w (Chunk c cs) = Chunk (S.intersperse w c)
                                    (foldrChunks (Chunk . intersperse') Empty cs)
   where intersperse' :: P.ByteString -> P.ByteString
-        intersperse' (S.PS fp o l) =
+        intersperse' (S.BS fp l) =
           S.unsafeCreate (2*l) $ \p' -> withForeignPtr fp $ \p -> do
             poke p' w
-            S.c_intersperse (p' `plusPtr` 1) (p `plusPtr` o) (fromIntegral l) w
+            S.c_intersperse (p' `plusPtr` 1) p (fromIntegral l) w
 
 -- | The 'transpose' function transposes the rows and columns of its
 -- 'ByteString' argument.
@@ -1360,9 +1360,9 @@ revChunks cs = L.foldl' (flip chunk) Empty cs
 -- | 'findIndexOrEnd' is a variant of findIndex, that returns the length
 -- of the string if no element is found, rather than Nothing.
 findIndexOrEnd :: (Word8 -> Bool) -> P.ByteString -> Int
-findIndexOrEnd k (S.PS x s l) =
+findIndexOrEnd k (S.BS x l) =
     S.accursedUnutterablePerformIO $
-      withForeignPtr x $ \f -> go (f `plusPtr` s) 0
+      withForeignPtr x $ \f -> go f 0
   where
     go !ptr !n | n >= l    = return l
                | otherwise = do w <- peek ptr
diff --git a/Data/ByteString/Lazy/Internal.hs b/Data/ByteString/Lazy/Internal.hs
index bd07fb570..cf569c020 100644
--- a/Data/ByteString/Lazy/Internal.hs
+++ b/Data/ByteString/Lazy/Internal.hs
@@ -153,12 +153,12 @@ unpackChars (Chunk c cs) = S.unpackAppendCharsLazy c (unpackChars cs)
 --
 invariant :: ByteString -> Bool
 invariant Empty                     = True
-invariant (Chunk (S.PS _ _ len) cs) = len > 0 && invariant cs
+invariant (Chunk (S.BS _ len) cs) = len > 0 && invariant cs
 
 -- | In a form that checks the invariant lazily.
 checkInvariant :: ByteString -> ByteString
 checkInvariant Empty = Empty
-checkInvariant (Chunk c@(S.PS _ _ len) cs)
+checkInvariant (Chunk c@(S.BS _ len) cs)
     | len > 0   = Chunk c (checkInvariant cs)
     | otherwise = error $ "Data.ByteString.Lazy: invariant violation:"
                ++ show (Chunk c cs)
@@ -167,8 +167,8 @@ checkInvariant (Chunk c@(S.PS _ _ len) cs)
 
 -- | Smart constructor for 'Chunk'. Guarantees the data type invariant.
 chunk :: S.ByteString -> ByteString -> ByteString
-chunk c@(S.PS _ _ len) cs | len == 0  = cs
-                          | otherwise = Chunk c cs
+chunk c@(S.BS _ len) cs | len == 0  = cs
+                        | otherwise = Chunk c cs
 {-# INLINE chunk #-}
 
 -- | Consume the chunks of a lazy ByteString with a natural right fold.
diff --git a/Data/ByteString/Short/Internal.hs b/Data/ByteString/Short/Internal.hs
index 17ff47db0..8bdc4d754 100644
--- a/Data/ByteString/Short/Internal.hs
+++ b/Data/ByteString/Short/Internal.hs
@@ -65,7 +65,6 @@ import Foreign.C.Types  (CSize(..), CInt(..), CLong(..))
 import Foreign.C.Types  (CSize, CInt, CLong)
 #endif
 import Foreign.Marshal.Alloc (allocaBytes)
-import Foreign.Ptr
 import Foreign.ForeignPtr (touchForeignPtr)
 #if MIN_VERSION_base(4,5,0)
 import Foreign.ForeignPtr.Unsafe (unsafeForeignPtrToPtr)
@@ -239,10 +238,10 @@ toShort :: ByteString -> ShortByteString
 toShort !bs = unsafeDupablePerformIO (toShortIO bs)
 
 toShortIO :: ByteString -> IO ShortByteString
-toShortIO (PS fptr off len) = do
+toShortIO (BS fptr len) = do
     mba <- stToIO (newByteArray len)
     let ptr = unsafeForeignPtrToPtr fptr
-    stToIO (copyAddrToByteArray (ptr `plusPtr` off) mba 0 len)
+    stToIO (copyAddrToByteArray ptr mba 0 len)
     touchForeignPtr fptr
     BA# ba# <- stToIO (unsafeFreezeByteArray mba)
     return (SBS ba# LEN(len))
@@ -261,7 +260,7 @@ fromShortIO sbs = do
     stToIO (copyByteArray (asBA sbs) 0 mba 0 len)
     let fp = ForeignPtr (byteArrayContents# (unsafeCoerce# mba#))
                         (PlainPtr mba#)
-    return (PS fp 0 len)
+    return (BS fp len)
 #else
     -- Before base 4.6 ForeignPtrContents is not exported from GHC.ForeignPtr
     -- so we cannot get direct access to the mbarr#
@@ -270,7 +269,7 @@ fromShortIO sbs = do
     let ptr = unsafeForeignPtrToPtr fptr
     stToIO (copyByteArrayToAddr (asBA sbs) 0 ptr len)
     touchForeignPtr fptr
-    return (PS fptr 0 len)
+    return (BS fptr len)
 #endif
 
 
diff --git a/Data/ByteString/Unsafe.hs b/Data/ByteString/Unsafe.hs
index a9e29db25..fed1f3c23 100644
--- a/Data/ByteString/Unsafe.hs
+++ b/Data/ByteString/Unsafe.hs
@@ -51,7 +51,7 @@ module Data.ByteString.Unsafe (
 import Data.ByteString.Internal
 
 import Foreign.ForeignPtr       (newForeignPtr_, newForeignPtr, withForeignPtr)
-import Foreign.Ptr              (Ptr, plusPtr, castPtr)
+import Foreign.Ptr              (Ptr, castPtr)
 
 import Foreign.Storable         (Storable(..))
 import Foreign.C.String         (CString, CStringLen)
@@ -75,30 +75,30 @@ import GHC.Ptr                  (Ptr(..))
 -- check for the empty case, so there is an obligation on the programmer
 -- to provide a proof that the ByteString is non-empty.
 unsafeHead :: ByteString -> Word8
-unsafeHead (PS x s l) = assert (l > 0) $
-    accursedUnutterablePerformIO $ withForeignPtr x $ \p -> peekByteOff p s
+unsafeHead (BS x l) = assert (l > 0) $
+    accursedUnutterablePerformIO $ withForeignPtr x $ \p -> peek p
 {-# INLINE unsafeHead #-}
 
 -- | A variety of 'tail' for non-empty ByteStrings. 'unsafeTail' omits the
 -- check for the empty case. As with 'unsafeHead', the programmer must
 -- provide a separate proof that the ByteString is non-empty.
 unsafeTail :: ByteString -> ByteString
-unsafeTail (PS ps s l) = assert (l > 0) $ PS ps (s+1) (l-1)
+unsafeTail (BS ps l) = assert (l > 0) $ BS (plusForeignPtr ps 1) (l-1)
 {-# INLINE unsafeTail #-}
 
 -- | A variety of 'init' for non-empty ByteStrings. 'unsafeInit' omits the
 -- check for the empty case. As with 'unsafeHead', the programmer must
 -- provide a separate proof that the ByteString is non-empty.
 unsafeInit :: ByteString -> ByteString
-unsafeInit (PS ps s l) = assert (l > 0) $ PS ps s (l-1)
+unsafeInit (BS ps l) = assert (l > 0) $ BS ps (l-1)
 {-# INLINE unsafeInit #-}
 
 -- | A variety of 'last' for non-empty ByteStrings. 'unsafeLast' omits the
 -- check for the empty case. As with 'unsafeHead', the programmer must
 -- provide a separate proof that the ByteString is non-empty.
 unsafeLast :: ByteString -> Word8
-unsafeLast (PS x s l) = assert (l > 0) $
-    accursedUnutterablePerformIO $ withForeignPtr x $ \p -> peekByteOff p (s+l-1)
+unsafeLast (BS x l) = assert (l > 0) $
+    accursedUnutterablePerformIO $ withForeignPtr x $ \p -> peekByteOff p (l-1)
 {-# INLINE unsafeLast #-}
 
 -- | Unsafe 'ByteString' index (subscript) operator, starting from 0, returning a 'Word8'
@@ -106,20 +106,20 @@ unsafeLast (PS x s l) = assert (l > 0) $
 -- obligation on the programmer to ensure the bounds are checked in some
 -- other way.
 unsafeIndex :: ByteString -> Int -> Word8
-unsafeIndex (PS x s l) i = assert (i >= 0 && i < l) $
-    accursedUnutterablePerformIO $ withForeignPtr x $ \p -> peekByteOff p (s+i)
+unsafeIndex (BS x l) i = assert (i >= 0 && i < l) $
+    accursedUnutterablePerformIO $ withForeignPtr x $ \p -> peekByteOff p i
 {-# INLINE unsafeIndex #-}
 
 -- | A variety of 'take' which omits the checks on @n@ so there is an
 -- obligation on the programmer to provide a proof that @0 <= n <= 'length' xs@.
 unsafeTake :: Int -> ByteString -> ByteString
-unsafeTake n (PS x s l) = assert (0 <= n && n <= l) $ PS x s n
+unsafeTake n (BS x l) = assert (0 <= n && n <= l) $ BS x n
 {-# INLINE unsafeTake #-}
 
 -- | A variety of 'drop' which omits the checks on @n@ so there is an
 -- obligation on the programmer to provide a proof that @0 <= n <= 'length' xs@.
 unsafeDrop  :: Int -> ByteString -> ByteString
-unsafeDrop n (PS x s l) = assert (0 <= n && n <= l) $ PS x (s+n) (l-n)
+unsafeDrop n (BS x l) = assert (0 <= n && n <= l) $ BS (plusForeignPtr x n) (l-n)
 {-# INLINE unsafeDrop #-}
 
 
@@ -143,7 +143,7 @@ unsafeDrop n (PS x s l) = assert (0 <= n && n <= l) $ PS x (s+n) (l-n)
 unsafePackAddressLen :: Int -> Addr# -> IO ByteString
 unsafePackAddressLen len addr# = do
     p <- newForeignPtr_ (Ptr addr#)
-    return $ PS p 0 len
+    return $ BS p len
 {-# INLINE unsafePackAddressLen #-}
 
 -- | /O(1)/ Construct a 'ByteString' given a Ptr Word8 to a buffer, a
@@ -158,7 +158,7 @@ unsafePackAddressLen len addr# = do
 unsafePackCStringFinalizer :: Ptr Word8 -> Int -> IO () -> IO ByteString
 unsafePackCStringFinalizer p l f = do
     fp <- FC.newForeignPtr p f
-    return $ PS fp 0 l
+    return $ BS fp l
 
 -- | Explicitly run the finaliser associated with a 'ByteString'.
 -- References to this value after finalisation may generate invalid memory
@@ -170,7 +170,7 @@ unsafePackCStringFinalizer p l f = do
 -- ever generated from the underlying byte array are no longer live.
 --
 unsafeFinalize :: ByteString -> IO ()
-unsafeFinalize (PS p _ _) = FC.finalizeForeignPtr p
+unsafeFinalize (BS p _) = FC.finalizeForeignPtr p
 
 ------------------------------------------------------------------------
 -- Packing CStrings into ByteStrings
@@ -188,7 +188,7 @@ unsafePackCString :: CString -> IO ByteString
 unsafePackCString cstr = do
     fp <- newForeignPtr_ (castPtr cstr)
     l <- c_strlen cstr
-    return $! PS fp 0 (fromIntegral l)
+    return $! BS fp (fromIntegral l)
 
 -- | /O(1)/ Build a 'ByteString' from a 'CStringLen'. This value will
 -- have /no/ finalizer associated with it, and will not be garbage
@@ -202,7 +202,7 @@ unsafePackCString cstr = do
 unsafePackCStringLen :: CStringLen -> IO ByteString
 unsafePackCStringLen (ptr,len) = do
     fp <- newForeignPtr_ (castPtr ptr)
-    return $! PS fp 0 (fromIntegral len)
+    return $! BS fp (fromIntegral len)
 
 -- | /O(n)/ Build a 'ByteString' from a malloced 'CString'. This value will
 -- have a @free(3)@ finalizer associated to it.
@@ -219,7 +219,7 @@ unsafePackMallocCString :: CString -> IO ByteString
 unsafePackMallocCString cstr = do
     fp <- newForeignPtr c_free_finalizer (castPtr cstr)
     len <- c_strlen cstr
-    return $! PS fp 0 (fromIntegral len)
+    return $! BS fp (fromIntegral len)
 
 -- | /O(1)/ Build a 'ByteString' from a malloced 'CStringLen'. This
 -- value will have a @free(3)@ finalizer associated to it.
@@ -235,7 +235,7 @@ unsafePackMallocCString cstr = do
 unsafePackMallocCStringLen :: CStringLen -> IO ByteString
 unsafePackMallocCStringLen (cstr, len) = do
     fp <- newForeignPtr c_free_finalizer (castPtr cstr)
-    return $! PS fp 0 len
+    return $! BS fp len
 
 -- ---------------------------------------------------------------------
 
@@ -265,7 +265,7 @@ unsafePackMallocCStringLen (cstr, len) = do
 -- after this.
 --
 unsafeUseAsCString :: ByteString -> (CString -> IO a) -> IO a
-unsafeUseAsCString (PS ps s _) ac = withForeignPtr ps $ \p -> ac (castPtr p `plusPtr` s)
+unsafeUseAsCString (BS ps _) ac = withForeignPtr ps $ \p -> ac (castPtr p)
 
 -- | /O(1) construction/ Use a 'ByteString' with a function requiring a
 -- 'CStringLen'.
@@ -283,4 +283,4 @@ unsafeUseAsCString (PS ps s _) ac = withForeignPtr ps $ \p -> ac (castPtr p `plu
 -- 'useAsCStringLen', which makes a copy of the original 'ByteString'.
 --
 unsafeUseAsCStringLen :: ByteString -> (CStringLen -> IO a) -> IO a
-unsafeUseAsCStringLen (PS ps s l) f = withForeignPtr ps $ \p -> f (castPtr p `plusPtr` s,l)
+unsafeUseAsCStringLen (BS ps l) f = withForeignPtr ps $ \p -> f (castPtr p,l)
diff --git a/bytestring.cabal b/bytestring.cabal
index b6384047b..5269c41f9 100644
--- a/bytestring.cabal
+++ b/bytestring.cabal
@@ -1,5 +1,5 @@
 Name:                bytestring
-Version:             0.10.10.0
+Version:             0.11.0.0
 Synopsis:            Fast, compact, strict and lazy byte strings with a list interface
 Description:
     An efficient compact, immutable byte string type (both strict and lazy)
diff --git a/tests/Hash.hs b/tests/Hash.hs
index 2e86b55d2..ea7b4e234 100644
--- a/tests/Hash.hs
+++ b/tests/Hash.hs
@@ -64,16 +64,15 @@ mulHi a b = fromIntegral (r `shiftR` 32)
 newtype OrdString = OrdString S.ByteString
      deriving Show
 
-eq a@(S.PS p s l) b@(S.PS p' s' l')
-         | l /= l'            = False    -- short cut on length
-         | p == p' && s == s' = True     -- short cut for the same string
-         | otherwise          = compare a b == EQ
+eq a@(S.BS p l) b@(S.BS p' l')
+         | l /= l' = False    -- shortcut on length
+         | p == p' = True     -- shortcut for the same string
+         | otherwise = compare a b == EQ
   where
-    compare (S.PS fp1 off1 len1) (S.PS fp2 off2 len2) = S.inlinePerformIO $
+    compare (S.BS fp1 len1) (S.BS fp2 len2) = S.inlinePerformIO $
         withForeignPtr fp1 $ \p1 ->
             withForeignPtr fp2 $ \p2 ->
-                cmp (p1 `plusPtr` off1)
-                    (p2 `plusPtr` off2) 0 len1 len2
+                cmp p1 p2 0 len1 len2
 
 cmp :: Ptr Word8 -> Ptr Word8 -> Int -> Int -> Int-> IO Ordering
 cmp !p1 !p2 !n len1 len2
diff --git a/tests/Words.hs b/tests/Words.hs
index 45a561d4b..499185cb1 100644
--- a/tests/Words.hs
+++ b/tests/Words.hs
@@ -35,11 +35,11 @@ instance Ord OrdString where
     compare (OrdString p) (OrdString q) = compareBytes p q
 
 compareBytes :: ByteString -> ByteString -> Ordering
-compareBytes (PS fp1 off1 len1) (PS fp2 off2 len2)
-    | len1 == 0  && len2 == 0                     = EQ  -- short cut for empty strings
-    | fp1 == fp2 && off1 == off2 && len1 == len2  = EQ  -- short cut for the same string
---  | max len1 len2 > 1                           = inlinePerformIO $
-    | otherwise                                   = inlinePerformIO $
+compareBytes (BS fp1 len1) (BS fp2 len2)
+    | len1 == 0  && len2 == 0     = EQ  -- shortcut for empty strings
+    | fp1 == fp2 && len1 == len2  = EQ  -- shortcut for the same string
+--  | max len1 len2 > 1           = inlinePerformIO $
+    | otherwise                   = inlinePerformIO $
     withForeignPtr fp1 $ \p1 ->
     withForeignPtr fp2 $ \p2 -> do
         i <- memcmp (p1 `plusPtr` off1) (p2 `plusPtr` off2) (fromIntegral $ min len1 len2)
diff --git a/tests/test-compare.hs b/tests/test-compare.hs
index 77d44c65e..6c0d2c330 100644
--- a/tests/test-compare.hs
+++ b/tests/test-compare.hs
@@ -37,14 +37,13 @@ main = do
 ------------------------------------------------------------------------
 
 compareBytes :: ByteString -> ByteString -> Ordering
-compareBytes (PS fp1 off1 len1) (PS fp2 off2 len2)
+compareBytes (BS fp1 len1) (BS fp2 len2)
 --    | len1 == 0  && len2 == 0                     = EQ  -- short cut for empty strings
 --    | fp1 == fp2 && off1 == off2 && len1 == len2  = EQ  -- short cut for the same string
     | otherwise                                   = inlinePerformIO $
     withForeignPtr fp1 $ \p1 ->
         withForeignPtr fp2 $ \p2 ->
-            cmp (p1 `plusPtr` off1)
-                (p2 `plusPtr` off2) 0 len1 len2
+            cmp p1 p2 0 len1 len2
  
 cmp :: Ptr Word8 -> Ptr Word8 -> Int -> Int -> Int-> IO Ordering
 cmp p1 p2 n len1 len2
@@ -58,13 +57,13 @@ cmp p1 p2 n len1 len2
                 LT -> return LT
                 GT -> return GT
  
-compareBytesC (PS x1 s1 l1) (PS x2 s2 l2)
-    | l1 == 0  && l2 == 0               = EQ  -- short cut for empty strings
-    | x1 == x2 && s1 == s2 && l1 == l2  = EQ  -- short cut for the same string
-    | otherwise                         = inlinePerformIO $
+compareBytesC (BS x1 l1) (BS x2 l2)
+    | l1 == 0  && l2 == 0   = EQ  -- short cut for empty strings
+    | x1 == x2 && l1 == l2  = EQ  -- short cut for the same string
+    | otherwise             = inlinePerformIO $
         withForeignPtr x1 $ \p1 ->
         withForeignPtr x2 $ \p2 -> do
-            i <- memcmp (p1 `plusPtr` s1) (p2 `plusPtr` s2) (fromIntegral $ min l1 l2)
+            i <- memcmp p1 p2 (fromIntegral $ min l1 l2)
             return $! case i `compare` 0 of
                         EQ  -> l1 `compare` l2
                         x   -> x
diff --git a/tests/unpack.hs b/tests/unpack.hs
index 71bcf97c6..27972e3a0 100644
--- a/tests/unpack.hs
+++ b/tests/unpack.hs
@@ -26,11 +26,11 @@ my_unpack ps = build (unpackFoldr ps)
 {-# INLINE my_unpack #-}
 
 unpackFoldr :: ByteString -> (Word8 -> a -> a) -> a -> a
-unpackFoldr (PS fp off len) f ch =
+unpackFoldr (BS fp len) f ch =
     unsafePerformIO $ withForeignPtr fp $ \p -> do
         let loop a b c | a `seq` b `seq` False = undefined -- needs the strictness
             loop _ (-1) acc = return acc
             loop q n    acc = do
                a <- peekByteOff q n
                loop q (n-1) (a `f` acc)
-        loop (p `plusPtr` off) (len-1) ch
+        loop p (len-1) ch