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Solidity

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (governance/extensions/GovernorVotesQuorumFraction.sol)
pragma solidity ^0.8.0;
import "./GovernorVotes.sol";
import "../../utils/Checkpoints.sol";
import "../../utils/math/SafeCast.sol";
/**
* @dev Extension of {Governor} for voting weight extraction from an {ERC20Votes} token and a quorum expressed as a
* fraction of the total supply.
*
* _Available since v4.3._
*/
abstract contract GovernorVotesQuorumFraction is GovernorVotes {
using Checkpoints for Checkpoints.History;
uint256 private _quorumNumerator; // DEPRECATED
Checkpoints.History private _quorumNumeratorHistory;
event QuorumNumeratorUpdated(uint256 oldQuorumNumerator, uint256 newQuorumNumerator);
/**
* @dev Initialize quorum as a fraction of the token's total supply.
*
* The fraction is specified as `numerator / denominator`. By default the denominator is 100, so quorum is
* specified as a percent: a numerator of 10 corresponds to quorum being 10% of total supply. The denominator can be
* customized by overriding {quorumDenominator}.
*/
constructor(uint256 quorumNumeratorValue) {
_updateQuorumNumerator(quorumNumeratorValue);
}
/**
* @dev Returns the current quorum numerator. See {quorumDenominator}.
*/
function quorumNumerator() public view virtual returns (uint256) {
return _quorumNumeratorHistory._checkpoints.length == 0 ? _quorumNumerator : _quorumNumeratorHistory.latest();
}
/**
* @dev Returns the quorum numerator at a specific block number. See {quorumDenominator}.
*/
function quorumNumerator(uint256 blockNumber) public view virtual returns (uint256) {
// If history is empty, fallback to old storage
uint256 length = _quorumNumeratorHistory._checkpoints.length;
if (length == 0) {
return _quorumNumerator;
}
// Optimistic search, check the latest checkpoint
Checkpoints.Checkpoint memory latest = _quorumNumeratorHistory._checkpoints[length - 1];
if (latest._blockNumber <= blockNumber) {
return latest._value;
}
// Otherwise, do the binary search
return _quorumNumeratorHistory.getAtBlock(blockNumber);
}
/**
* @dev Returns the quorum denominator. Defaults to 100, but may be overridden.
*/
function quorumDenominator() public view virtual returns (uint256) {
return 100;
}
/**
* @dev Returns the quorum for a block number, in terms of number of votes: `supply * numerator / denominator`.
*/
function quorum(uint256 blockNumber) public view virtual override returns (uint256) {
return (token.getPastTotalSupply(blockNumber) * quorumNumerator(blockNumber)) / quorumDenominator();
}
/**
* @dev Changes the quorum numerator.
*
* Emits a {QuorumNumeratorUpdated} event.
*
* Requirements:
*
* - Must be called through a governance proposal.
* - New numerator must be smaller or equal to the denominator.
*/
function updateQuorumNumerator(uint256 newQuorumNumerator) external virtual onlyGovernance {
_updateQuorumNumerator(newQuorumNumerator);
}
/**
* @dev Changes the quorum numerator.
*
* Emits a {QuorumNumeratorUpdated} event.
*
* Requirements:
*
* - New numerator must be smaller or equal to the denominator.
*/
function _updateQuorumNumerator(uint256 newQuorumNumerator) internal virtual {
require(
newQuorumNumerator <= quorumDenominator(),
"GovernorVotesQuorumFraction: quorumNumerator over quorumDenominator"
);
uint256 oldQuorumNumerator = quorumNumerator();
// Make sure we keep track of the original numerator in contracts upgraded from a version without checkpoints.
if (oldQuorumNumerator != 0 && _quorumNumeratorHistory._checkpoints.length == 0) {
_quorumNumeratorHistory._checkpoints.push(
Checkpoints.Checkpoint({_blockNumber: 0, _value: SafeCast.toUint224(oldQuorumNumerator)})
);
}
// Set new quorum for future proposals
_quorumNumeratorHistory.push(newQuorumNumerator);
emit QuorumNumeratorUpdated(oldQuorumNumerator, newQuorumNumerator);
}
}