cp :: FileSystem -> Path -> FileSystem -> Path -> IO ()
cp (FileSystem fs) p (FileSystem fs') p' =
  withCString p $ \src -> withCString p' $ \dst ->
   throwErrnoIfMinus1_ "cp" $ c_hdfs_copy fs src fs' dst
cp :: FileSystem -> Path -> FileSystem -> Path -> IO ()
cp (FileSystem fs) p (FileSystem fs') p' =
  withCString p $ \src -> withCString p' $ \dst ->
   throwErrnoIfMinus1_ "cp" $ c_hdfs_copy fs src fs' dst
cp (FileSystem fs) p (FileSystem fs') p' =
  withCString p $ \src -> withCString p' $ \dst ->
   throwErrnoIfMinus1_ "cp" $ c_hdfs_copy fs src fs' dst