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May 1, 2022 05:40
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// SPDX-License-Identifier: GPL-3.0 | |
pragma solidity >=0.7.0 <0.9.0; | |
/** | |
* @title Ballot | |
* @dev Implements voting process along with vote delegation | |
*/ | |
contract TimedBallot { | |
struct Voter { | |
uint weight; // weight is accumulated by delegation | |
bool voted; // if true, that person already voted | |
address delegate; // person delegated to | |
uint vote; // index of the voted proposal | |
} | |
struct Proposal { | |
// If you can limit the length to a certain number of bytes, | |
// always use one of bytes1 to bytes32 because they are much cheaper | |
bytes32 name; // short name (up to 32 bytes) | |
uint voteCount; // number of accumulated votes | |
} | |
address public chairperson; | |
mapping(address => Voter) public voters; | |
uint startTime; // voting start time | |
Proposal[] public proposals; | |
/** | |
* @dev Create a new ballot to choose one of 'proposalNames'. | |
* @param proposalNames names of proposals | |
*/ | |
constructor(bytes32[] memory proposalNames) { | |
chairperson = msg.sender; | |
voters[chairperson].weight = 1; | |
startTime = block.timestamp; | |
for (uint i = 0; i < proposalNames.length; i++) { | |
// 'Proposal({...})' creates a temporary | |
// Proposal object and 'proposals.push(...)' | |
// appends it to the end of 'proposals'. | |
proposals.push(Proposal({ | |
name: proposalNames[i], | |
voteCount: 0 | |
})); | |
} | |
} | |
/** | |
* @dev Modifier to check if the voting period is over. | |
*/ | |
modifier voteEnded() { | |
require(block.timestamp <= (startTime + 5 minutes), "Voting is over"); | |
// Underscore is a special character only used inside | |
// a function modifier and it tells Solidity to | |
// execute the rest of the code. | |
_; | |
} | |
/** | |
* @dev Give 'voter' the right to vote on this ballot. May only be called by 'chairperson'. | |
* @param voter address of voter | |
*/ | |
function giveRightToVote(address voter) voteEnded public { | |
require( | |
msg.sender == chairperson, | |
"Only chairperson can give right to vote." | |
); | |
require( | |
!voters[voter].voted, | |
"The voter already voted." | |
); | |
require(voters[voter].weight == 0); | |
voters[voter].weight = 1; | |
} | |
/** | |
* @dev Delegate your vote to the voter 'to'. | |
* @param to address to which vote is delegated | |
*/ | |
function delegate(address to) voteEnded public { | |
Voter storage sender = voters[msg.sender]; | |
require(!sender.voted, "You already voted."); | |
require(to != msg.sender, "Self-delegation is disallowed."); | |
while (voters[to].delegate != address(0)) { | |
to = voters[to].delegate; | |
// We found a loop in the delegation, not allowed. | |
require(to != msg.sender, "Found loop in delegation."); | |
} | |
sender.voted = true; | |
sender.delegate = to; | |
Voter storage delegate_ = voters[to]; | |
if (delegate_.voted) { | |
// If the delegate already voted, | |
// directly add to the number of votes | |
proposals[delegate_.vote].voteCount += sender.weight; | |
} else { | |
// If the delegate did not vote yet, | |
// add to her weight. | |
delegate_.weight += sender.weight; | |
} | |
} | |
/** | |
* @dev Give your vote (including votes delegated to you) to proposal 'proposals[proposal].name'. | |
* @param proposal index of proposal in the proposals array | |
*/ | |
function vote(uint proposal) voteEnded public { | |
Voter storage sender = voters[msg.sender]; | |
require(sender.weight != 0, "Has no right to vote"); | |
require(!sender.voted, "Already voted."); | |
sender.voted = true; | |
sender.vote = proposal; | |
// If 'proposal' is out of the range of the array, | |
// this will throw automatically and revert all | |
// changes. | |
proposals[proposal].voteCount += sender.weight; | |
} | |
/** | |
* @dev Computes the winning proposal taking all previous votes into account. | |
* @return winningProposal_ index of winning proposal in the proposals array | |
*/ | |
function winningProposal() public view | |
returns (uint winningProposal_) | |
{ | |
uint winningVoteCount = 0; | |
for (uint p = 0; p < proposals.length; p++) { | |
if (proposals[p].voteCount > winningVoteCount) { | |
winningVoteCount = proposals[p].voteCount; | |
winningProposal_ = p; | |
} | |
} | |
} | |
/** | |
* @dev Calls winningProposal() function to get the index of the winner contained in the proposals array and then | |
* @return winnerName_ the name of the winner | |
*/ | |
function winnerName() public view | |
returns (bytes32 winnerName_) | |
{ | |
winnerName_ = proposals[winningProposal()].name; | |
} | |
} |
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