diff --git a/Data/Byteable.hs b/Data/Byteable.hs
--- a/Data/Byteable.hs
+++ b/Data/Byteable.hs
@@ -10,13 +10,27 @@
     , constEqBytes
     ) where
 
+import Foreign.Ptr (Ptr, plusPtr)
+import Foreign.ForeignPtr (withForeignPtr)
 import Data.ByteString (ByteString)
 import Data.List (foldl')
+import Data.Word (Word8)
 import qualified Data.ByteString as B (length, zipWith)
+import qualified Data.ByteString.Internal as B (toForeignPtr)
 
 -- | Class of things that can generate sequence of bytes
 class Byteable a where
-    toBytes :: a -> ByteString
+    -- | Convert a byteable type to a bytestring
+    toBytes        :: a -> ByteString
+
+    -- | Return the size of the byteable .
+    byteableLength :: a -> Int
+    byteableLength = B.length . toBytes
+
+    -- | Provide a way to look at the data of a byteable type with a ptr.
+    withBytePtr :: a -> (Ptr Word8 -> IO b) -> IO b
+    withBytePtr a f = withForeignPtr fptr $ \ptr -> f (ptr `plusPtr` off)
+      where (fptr, off, _) = B.toForeignPtr $ toBytes a
 
 instance Byteable ByteString where
     toBytes bs = bs
diff --git a/byteable.cabal b/byteable.cabal
--- a/byteable.cabal
+++ b/byteable.cabal
@@ -1,5 +1,5 @@
 Name:                byteable
-Version:             0.1.0
+Version:             0.1.1
 Synopsis:            Type class for sequence of bytes
 Description:
     Abstract class to manipulate sequence of bytes
@@ -8,7 +8,7 @@
     types that are just wrapping a bytestring with stronger and
     more meaniful name.
     .
-    Usual definition is of the form: newtype MyType = MyType ByteString
+    Usual definition of those types are of the form: newtype MyType = MyType ByteString
 License:             BSD3
 License-file:        LICENSE
 Copyright:           Vincent Hanquez <vincent@snarc.org>