160;</td>
        </tr>
        <tr>
          <td></td>
          <td>)</td>
          <td></td><td></td>
        </tr>
      </table>
</div><div class="memdoc">
<p>Places the value for the key into the store if and only if the key does not exist.</p>
<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">rev</td><td>the location where to store the revision of this value, or <code>NULL</code> if the stream information is not needed. </td></tr>
    <tr><td class="p