ss="identifier">uint64_t</span> <span class="identifier">size</span><span class="special">,</span>         <span class="comment">// Size of the chunk, or zero for the last chunk</span>
        <span class="identifier">string_view</span> <span class="identifier">extensions</span><span class="special">,</span>     <span class="comment">// The raw chunk-extensions string. Already validated.</span>
        <span class="identifier">error_code</span><span class="special">&amp;</span> <span class="identifier">ev</