title: How to create a Ptr Word8 for ByteString
body: <p><a href="https://github.com/haskell/bytestring/blob/master/Data/ByteString/Internal.hs#L39" rel="nofollow noreferrer">create</a>, from Data.ByteString.Internal, states that it needs a <code>Ptr Word8</code> in order to create a ByteString. I'm guessing this is like a reference to the head of the bytestring or something. However, I'm not sure what I should use to create a new pointer - I'm fairly sure it's not done properly with <a href="https://www.stackage.org/haddock/lts-9.6/base-4.9.1.0/Foreign-Ptr.html#v:nullPtr" rel="nofollow noreferrer">nullPtr</a>.</p>