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70 lines
2.5 KiB
70 lines
2.5 KiB
// SPDX-License-Identifier: MIT
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// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/extensions/ERC20Votes.sol)
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pragma solidity ^0.8.0;
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import "../ERC20.sol";
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import "../../../governance/utils/Votes.sol";
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import "../../../utils/math/SafeCast.sol";
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/**
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* @dev Extension of ERC20 to support Compound-like voting and delegation. This version is more generic than Compound's,
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* and supports token supply up to 2^224^ - 1, while COMP is limited to 2^96^ - 1.
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*
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* NOTE: If exact COMP compatibility is required, use the {ERC20VotesComp} variant of this module.
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*
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* This extension keeps a history (checkpoints) of each account's vote power. Vote power can be delegated either
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* by calling the {delegate} function directly, or by providing a signature to be used with {delegateBySig}. Voting
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* power can be queried through the public accessors {getVotes} and {getPastVotes}.
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*
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* By default, token balance does not account for voting power. This makes transfers cheaper. The downside is that it
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* requires users to delegate to themselves in order to activate checkpoints and have their voting power tracked.
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*
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* _Available since v4.2._
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*/
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abstract contract ERC20Votes is ERC20, Votes {
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/**
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* @dev Maximum token supply. Defaults to `type(uint224).max` (2^224^ - 1).
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*/
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function _maxSupply() internal view virtual returns (uint224) {
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return type(uint224).max;
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}
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/**
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* @dev Move voting power when tokens are transferred.
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*
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* Emits a {IVotes-DelegateVotesChanged} event.
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*/
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function _update(
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address from,
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address to,
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uint256 amount
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) internal virtual override {
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super._update(from, to, amount);
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if (from == address(0)) {
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require(totalSupply() <= _maxSupply(), "ERC20Votes: total supply risks overflowing votes");
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}
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_transferVotingUnits(from, to, amount);
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}
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/**
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* @dev Get number of checkpoints for `account`.
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*/
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function numCheckpoints(address account) public view virtual returns (uint32) {
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return _numCheckpoints(account);
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}
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/**
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* @dev Get the `pos`-th checkpoint for `account`.
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*/
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function checkpoints(address account, uint32 pos) public view virtual returns (Checkpoints.Checkpoint memory) {
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return _checkpoints(account, pos);
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}
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/**
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* @dev Returns the balance of `account`.
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*/
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function _getVotingUnits(address account) internal view virtual override returns (uint256) {
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return balanceOf(account);
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}
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}
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