updateEndOfSlice :: Buffer    -- Old buffer
                 -> Ptr Word8 -- New end of slice
                 -> Buffer    -- Updated buffer
updateEndOfSlice (Buffer fpbuf p0 _ ope) op' = Buffer fpbuf p0 op' ope
updateEndOfSlice :: Buffer    -- Old buffer
                 -> Ptr Word8 -- New end of slice
                 -> Buffer
updateEndOfSlice (Buffer fpbuf p0 _ ope) op' = Buffer fpbuf p0 op' ope
updateEndOfSlice (Buffer fpbuf p0 _ ope) op' = Buffer fpbuf p0 op' ope