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<aname="events"></a><h1class="show-anchors"><div>Events<divclass="anchors"><aclass="self"href="/v5/concepts/events/#events"></a></div></div></h1><p>Explain how topics and such work</p>
<aname="events--solidity-topics"></a><h2class="show-anchors"><div>Solidity Topics<divclass="anchors"><aclass="self"href="/v5/concepts/events/#events--solidity-topics"></a></div></div></h2><p>How to compute the topic...</p>
<aname="events--logs-and-filtering"></a><h2class="show-anchors"><div>Logs and Filtering<divclass="anchors"><aclass="self"href="/v5/concepts/events/#events--logs-and-filtering"></a></div></div></h2><p>Example hog logs are used.</p>
<p>Link to provider.getLogs and contract.on</p>
<aname="events--logs-and-filtering--filters"></a><h3class="show-anchors"><div>Filters<divclass="anchors"><aclass="self"href="/v5/concepts/events/#events--logs-and-filtering--filters"></a></div></div></h3><p>Filter are used as a way to query ... efficient, explain bloom filters lightly</p>
<p>A filter may have up to 4 topic-sets, where each topic-set refers to a condition that must match the log topic in that position (i.e. each condition is <codeclass="inline">AND</code>-ed together).</p>
<p>If a topic-set is <codeclass="inline">null</code>, a log topic in that position is not filtered at all and <b>any value</b> matches.</p>
<p>If a topic-set is a single topic, a log topic in that position must match <b>that topic</b>.</p>
<p>If a topic-set is an array of topics, a log topic in that position must match any <b>one</b> of the topics (i.e. the topic in this position are <codeclass="inline">OR</code>-ed).</p>
<tableclass="table full"><tr><tdalign="center"width="25%"><b>Topic-Sets</b></td><tdalign="center"colspan="3"width="75%"><b>Matching Logs</b></td><tdclass="fix"> </td></tr><tr><tdalign="center"width="25%">[ A ]</td><tdalign="left"colspan="3"rowspan="2"width="75%">topic[0] = A</td><tdclass="fix"> </td></tr><tr><tdalign="center"width="25%">[ A, null ]</td><tdclass="fix"> </td></tr><tr><tdalign="center"width="25%">[ null, B ]</td><tdalign="left"colspan="3"rowspan="3"width="75%">topic[1] = B</td><tdclass="fix"> </td></tr><tr><tdalign="center"width="25%">[ null, [ B ] ]</td><tdclass="fix"> </td></tr><tr><tdalign="center"width="25%">[ null, [ B ], null ]</td><tdclass="fix"> </td></tr><tr><tdalign="center"width="25%">[ A, B ]</td><tdalign="left"colspan="3"rowspan="3"width="75%">(topic[0] = A) <b>AND</b> (topic[1] = B)</td><tdclass="fix"> </td></tr><tr><tdalign="center"width="25%">[ A, [ B ] ]</td><tdclass="fix"> </td></tr><tr><tdalign="center"width="25%">[ A, [ B ], null ]</td><tdclass="fix"> </td></tr><tr><tdalign="center"width="25%">[ [ A, B ] ]</td><tdalign="left"colspan="3"rowspan="2"width="75%">(topic[0] = A) <b>OR</b> (topic[0] = B)</td><tdclass="fix"> </td></tr><tr><tdalign="center"width="25%">[ [ A, B ], null ]</td><tdclass="fix"> </td></tr><tr><tdalign="center"width="25%">[ [ A, B ], [ C, D ] ]</td><tdalign="left"colspan="3"width="75%"><b>[</b> (topic[0] = A) <b>OR</b> (topic[0] = B) <b>]</b><b>AND</b><b>[</b> (topic[1] = C) <b>OR</b> (topic[1] = D) <b>]</b></td><tdclass="fix"> </td></tr><tr><tdclass="table-title"colspan="4">Example Log Matching</td><tdclass="fix"> </td></tr></table><divclass="code-title"><div>ERC-20 Transfer Filter Examples</div></div><divclass="code"><spanclass="comment">// Short example of manually creating filters for an ERC-20
</span><spanclass="comment">// Transfer event.
</span>//
<spanclass="comment">// Most users should generally use the Contract API to
</span><spanclass="comment">// compute filters, as it is much simpler, but this is
</span><spanclass="comment">// provided as an illustration for those curious. See
</span><spanclass="comment">// below for examples of the equivalent Contract API.
</span></div><aname="events--logs-and-filtering--other-things-todo"></a><h3class="show-anchors"><div>Other Things? TODO<divclass="anchors"><aclass="self"href="/v5/concepts/events/#events--logs-and-filtering--other-things-todo"></a></div></div></h3><p>Explain what happens to strings and bytes, how to filter and retain the value</p>
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