/span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">(-</span><span class="number">1</span><span class="special">);</span>

        <span class="keyword">bool</span> <span class="identifier">on_document_begin</span><span class="special">(</span> <span class="identifier">error_code</span><span class="special">&amp;</span> <span class="special">)</span> <span class="special">{</span> <span class="key