158 lines
4.7 KiB
Plaintext
158 lines
4.7 KiB
Plaintext
_section: Events
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Explain how topics and such work
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_subsection: Solidity Topics
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How to compute the topic...
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_subsection: Logs and Filtering
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Example hog logs are used.
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Link to provider.getLogs and contract.on
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_heading: Filters
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Filter are used as a way to query ... efficient, explain bloom filters lightly
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A filter may have up to 4 topic-sets, where each topic-set refers
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to a condition that must match the log topic in that position (i.e. each
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condition is ``AND``-ed together).
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If a topic-set is ``null``, a log topic in that position is not filtered
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at all and **any value** matches.
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If a topic-set is a single topic, a log topic in that position must match
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**that topic**.
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If a topic-set is an array of topics, a log topic in that position must
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match any **one** of the topics (i.e. the topic in this position are ``OR``-ed).
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_table: Example Log Matching @style<full>
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$TopicABaCD: **[** (topic[0] = A) **OR** (topic[0] = B) **]** **AND**
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**[** (topic[1] = C) **OR** (topic[1] = D) **]**
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| **Topic-Sets** | **Matching Logs** <<|
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| [ A ] | topic[0] = A <<|
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| [ A, null ] | ^ |
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| [ null, B ] | topic[1] = B <<|
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| [ null, [ B ] ] | ^ |
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| [ null, [ B ], null ] | ^ |
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| [ A, B ] | (topic[0] = A) **AND** (topic[1] = B) <<|
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| [ A, [ B ] ] | ^ |
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| [ A, [ B ], null ] | ^ |
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| [ [ A, B ] ] | (topic[0] = A) **OR** (topic[0] = B) <<|
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| [ [ A, B ], null ] | ^ |
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| [ [ A, B ], [ C, D ] ] | $TopicABaCD <<|
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_code: ERC-20 Transfer Filter Examples @lang<javascript>
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// <hide>
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const tokenAddress = ethers.constants.AddressZero;
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const myAddress = ethers.constants.AddressZero;
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const myOtherAddress = ethers.constants.AddressZero;
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const id = ethers.utils.id;
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const hexZeroPad = ethers.utils.hexZeroPad;
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// </hide>
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// Short example of manually creating filters for an ERC-20
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// Transfer event.
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//
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// Most users should generally use the Contract API to
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// compute filters, as it is much simpler, but this is
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// provided as an illustration for those curious. See
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// below for examples of the equivalent Contract API.
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// ERC-20:
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// Transfer(address indexed src, address indexed dst, uint val)
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//
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// -------------------^
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// ----------------------------------------^
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//
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// Notice that only *src* and *dst* are *indexed*, so ONLY they
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// qualify for filtering.
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//
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// Also, note that in Solidity an Event uses the first topic to
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// identify the Event name; for Transfer this will be:
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// id("Transfer(address,address,uint256)")
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//
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// Other Notes:
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// - A topic must be 32 bytes; so shorter types must be padded
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// List all token transfers *from* myAddress
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filter = {
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address: tokenAddress,
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topics: [
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id("Transfer(address,address,uint256)"),
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hexZeroPad(myAddress, 32)
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]
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}
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// List all token transfers *to* myAddress:
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filter = {
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address: tokenAddress,
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topics: [
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id("Transfer(address,address,uint256)"),
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null,
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hexZeroPad(myAddress, 32)
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]
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}
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// List all token transfers *to* myAddress or myOtherAddress:
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filter = {
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address: tokenAddress,
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topics: [
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id("Transfer(address,address,uint256)"),
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null,
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[
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hexZeroPad(myAddress, 32),
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hexZeroPad(myOtherAddress, 32),
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]
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]
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}
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_null:
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To simplify life, ..., explain here, the contract API
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_code: ERC-20 Contract Filter Examples @lang<javascript>
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// <hide>
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const tokenAddress = "0x6B175474E89094C44Da98b954EedeAC495271d0F"; // DAI
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const myAddress = "0x8ba1f109551bD432803012645Ac136ddd64DBA72";
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const otherAddress = "0xEA517D5a070e6705Cc5467858681Ed953d285Eb9";
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const provider = ethers.getDefaultProvider();
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const Contract = ethers.Contract;
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// </hide>
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const abi = [
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"event Transfer(address indexed src, address indexed dst, uint val)"
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];
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const contract = new Contract(tokenAddress, abi, provider);
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// List all token transfers *from* myAddress
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contract.filters.Transfer(myAddress)
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//!
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// List all token transfers *to* myAddress:
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contract.filters.Transfer(null, myAddress)
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//!
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// List all token transfers *from* myAddress *to* otherAddress:
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contract.filters.Transfer(myAddress, otherAddress)
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//!
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// List all token transfers *to* myAddress OR otherAddress:
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contract.filters.Transfer(null, [ myAddress, otherAddress ])
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//!
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_heading: Other Things? TODO
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Explain what happens to strings and bytes, how to filter and retain the value
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