Schedule state changes on the EVM
The repo provides tools to let you easily schedule state changes on the EVM. It does it by dividing time in epochs through onchain "clocks". Clocks are single contracts following a common interface (ICron.sol)
Every cron contract calculates the number of ocurrences a given pattern has done since a initial date, called initialTimestamp(), using modular arithmetics through the DateTime library.
This number is provided via heigh() function, enabling you to handle states referencing this contract. They also provide the following event, through a next()function. This one is useful for schedule external contract execution through oracles.
Timestamp(in seconds) where the counter starts.
function initTimestamp() public view returns (uint256);Return the number of occurrences of the stored crontab expression from initialTimestamp() to block.timestamp
function height(bytes32 _id) public view returns (uint256);Return the number of occurrences of the stored crontab expression from initTimestamp() to a given _timestamp
function heightOf(bytes32 _id, uint256 _timestamp) public view returns (uint256);Return the next timestamp where height will be changed, 2^256-1 if no new event is expected
function next(bytes32 _id) public view returns (uint256);While we explore a generic clock compiler, we have set some clocks provided to test in Rinkeby, tracking the amount of days/months/hours since the network was released.
Their solidity code can be found at ./contracts/clocks.
| Test Contract | Cron expression | Network | Address |
|---|---|---|---|
| Hourly | 0 * * * * / @hourly | Rinkeby | 0xaeec5734b4fbf6fd176d308ed5cdd143fc0d0810 |
| Daily | 0 0 * * * / @Daily | Rinkeby | 0x4b8eb7f7788f2770d0b172a8e3757f481cdc5cb0 |
| Monthly | 0 0 1 * * /@Monthly | Rinkeby | 0x4e8A7a5dcE61bF881Cebe4193410FC496414ca09 |
In order to use it in your project, you can just import ICron interface and point to one of the previously mentioned instances:
address hourly = 0xaeec5734b4fbf6fd176d308ed5cdd143fc0d0810
ICron c = ICron(0xaeec5734b4fbf6fd176d308ed5cdd143fc0d0810)
uint256 height() =c.height() // this variable will automatically increment every hour!You can always use the truffle package to test and contribute to the library. The package needs from a running Ethereum rpc instance in localhost, port 8545. You can run a ganache-cli instance or run geth. You can run the tests by just running:
truffle testThe project is open to contributions, just open a PR! We follow Angular Git Commit guidelines, to follow semantic-releaseversioning.