56 lines
1.4 KiB
Solidity
56 lines
1.4 KiB
Solidity
// SPDX-License-Identifier: MIT
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pragma solidity ^0.8.0;
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import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
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contract Collateral {
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IERC20 private immutable token;
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Totals private totals;
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mapping(address => uint256) private balances;
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constructor(IERC20 _token) invariant {
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token = _token;
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}
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function balanceOf(address account) public view returns (uint256) {
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return balances[account];
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}
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function add(address account, uint256 amount) private {
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balances[account] += amount;
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totals.balance += amount;
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}
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function subtract(address account, uint256 amount) private {
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balances[account] -= amount;
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totals.balance -= amount;
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}
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function deposit(uint256 amount) public invariant {
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token.transferFrom(msg.sender, address(this), amount);
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totals.deposited += amount;
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add(msg.sender, amount);
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}
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function withdraw() public invariant {
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uint256 amount = balanceOf(msg.sender);
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totals.withdrawn += amount;
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subtract(msg.sender, amount);
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assert(token.transfer(msg.sender, amount));
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}
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modifier invariant() {
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Totals memory oldTotals = totals;
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_;
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assert(totals.deposited >= oldTotals.deposited);
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assert(totals.withdrawn >= oldTotals.withdrawn);
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assert(totals.deposited == totals.balance + totals.withdrawn);
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}
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struct Totals {
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uint256 balance;
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uint256 deposited;
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uint256 withdrawn;
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}
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}
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