    <span class="comment">// This call guarantees it will make some</span>
        <span class="comment">// forward progress, or otherwise return an error.</span>
        <span class="identifier">write_some</span><span class="special">(</span><span class="identifier">stream</span><span class="special">,</span> <span class="identifier">sr</span><span class="special">);</span>
    <span class="special">}</span>
    <span class="keyword">while</span><span class="special">(!</span> <span class="identifier">sr</