ass="identifier">zs</span><span class="special">.</span><span class="identifier">next_in</span></code>
          or <code class="computeroutput"><span class="identifier">zs</span><span class="special">.</span><span class="identifier">next_out</span></code> was null), <code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">need_buffers</span></code>
          if no progress is possible or if there was not enough room in the output
          bu