NoBey/uniswap-v2
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fix bug with updating invariantLast

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This commit is contained in:
Noah Zinsmeister
2020-01-08 13:19:26 -05:00
parent 9f15d75925
commit 5a84023836
1 changed files with 32 additions and 29 deletions
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61
contracts/UniswapV2.sol
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@ -14,9 +14,9 @@ contract UniswapV2 is IUniswapV2, ERC20("Uniswap V2", "UNI-V2", 18, 0) {
address public token0; address public token0;
address public token1; address public token1;
uint112 private reserve0_; uint112 private reserve0;
uint112 private reserve1_; uint112 private reserve1;
uint32 private blockNumberLast_; uint32 private blockNumberLast;
uint public price0CumulativeLast; uint public price0CumulativeLast;
uint public price1CumulativeLast; uint public price1CumulativeLast;
@ -51,35 +51,36 @@ contract UniswapV2 is IUniswapV2, ERC20("Uniswap V2", "UNI-V2", 18, 0) {
token1 = _token1; token1 = _token1;
} }
function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockNumberLast) { function getReserves() external view returns (uint112 _reserve0, uint112 _reserve1, uint32 _blockNumberLast) {
return (reserve0_, reserve1_, blockNumberLast_); return (reserve0, reserve1, blockNumberLast);
} }
// update reserves and, if necessary, increment price accumulators // update reserves and, if necessary, increment price accumulators
function _update(uint balance0, uint balance1, uint112 _reserve0, uint112 _reserve1) private { function _update(uint balance0, uint balance1, uint112 _reserve0, uint112 _reserve1) private {
require(balance0 <= uint112(-1) && balance1 <= uint112(-1), "UniswapV2: BALANCE_OVERFLOW"); require(balance0 <= uint112(-1) && balance1 <= uint112(-1), "UniswapV2: BALANCE_OVERFLOW");
uint32 blockNumber = uint32(block.number % 2**32); uint32 blockNumber = uint32(block.number % 2**32);
uint32 blocksElapsed = blockNumber - blockNumberLast_; // overflow is desired uint32 blocksElapsed = blockNumber - blockNumberLast; // overflow is desired
if (blocksElapsed > 0 && _reserve0 != 0 && _reserve1 != 0) { if (blocksElapsed > 0 && _reserve0 != 0 && _reserve1 != 0) {
// * never overflows, and + overflow is desired // * never overflows, and + overflow is desired
price0CumulativeLast += uint(UQ112x112.encode(_reserve1).qdiv(_reserve0)) * blocksElapsed; price0CumulativeLast += uint(UQ112x112.encode(_reserve1).qdiv(_reserve0)) * blocksElapsed;
price1CumulativeLast += uint(UQ112x112.encode(_reserve0).qdiv(_reserve1)) * blocksElapsed; price1CumulativeLast += uint(UQ112x112.encode(_reserve0).qdiv(_reserve1)) * blocksElapsed;
} }
// ↓↓↓↓ single SSTORE ↓↓↓↓ // ↓↓↓↓ single SSTORE ↓↓↓↓
reserve0_ = uint112(balance0); reserve0 = uint112(balance0);
reserve1_ = uint112(balance1); reserve1 = uint112(balance1);
blockNumberLast_ = blockNumber; blockNumberLast = blockNumber;
// ↑↑↑↑ single SSTORE ↑↑↑↑ // ↑↑↑↑ single SSTORE ↑↑↑↑
emit Sync(reserve0_, reserve1_); emit Sync(reserve0, reserve1);
} }
// mint liquidity equivalent to 20% of newly accumulated fees // mint liquidity equivalent to 20% of newly accumulated fees
function _mintFee(uint balance0, uint balance1) private { function _mintFee(uint112 _reserve0, uint112 _reserve1) private returns (bool feeOn) {
address feeTo = IUniswapV2Factory(factory).feeTo(); address feeTo = IUniswapV2Factory(factory).feeTo();
if (feeTo != address(0)) { feeOn = feeTo != address(0);
if (feeOn) {
uint _invariantLast = invariantLast; // for gas savings uint _invariantLast = invariantLast; // for gas savings
if (_invariantLast != 0) { if (_invariantLast != 0) {
uint invariant = Math.sqrt(uint(reserve0_) * reserve1_); // * doesn't overflow uint invariant = Math.sqrt(uint(_reserve0) * _reserve1); // * doesn't overflow
if (invariant > _invariantLast) { if (invariant > _invariantLast) {
uint numerator = totalSupply.mul(invariant.sub(_invariantLast)); uint numerator = totalSupply.mul(invariant.sub(_invariantLast));
uint denominator = uint(4).mul(invariant).add(_invariantLast); uint denominator = uint(4).mul(invariant).add(_invariantLast);
@ -87,20 +88,19 @@ contract UniswapV2 is IUniswapV2, ERC20("Uniswap V2", "UNI-V2", 18, 0) {
if (liquidity > 0) _mint(feeTo, liquidity); if (liquidity > 0) _mint(feeTo, liquidity);
} }
} }
invariantLast = Math.sqrt(balance0.mul(balance1));
} }
} }
function mint(address to) external lock returns (uint liquidity) { function mint(address to) external lock returns (uint liquidity) {
uint _totalSupply = totalSupply; // for gas savings uint _totalSupply = totalSupply; // for gas savings
uint112 _reserve0 = reserve0_; // for gas savings uint112 _reserve0 = reserve0; // for gas savings
uint112 _reserve1 = reserve1_; // for gas savings uint112 _reserve1 = reserve1; // for gas savings
uint balance0 = IERC20(token0).balanceOf(address(this)); uint balance0 = IERC20(token0).balanceOf(address(this));
uint balance1 = IERC20(token1).balanceOf(address(this)); uint balance1 = IERC20(token1).balanceOf(address(this));
uint amount0 = balance0.sub(_reserve0); uint amount0 = balance0.sub(_reserve0);
uint amount1 = balance1.sub(_reserve1); uint amount1 = balance1.sub(_reserve1);
_mintFee(balance0, balance1); bool feeOn = _mintFee(_reserve0, _reserve1);
liquidity = _totalSupply == 0 ? liquidity = _totalSupply == 0 ?
Math.sqrt(amount0.mul(amount1)) : Math.sqrt(amount0.mul(amount1)) :
Math.min(amount0.mul(_totalSupply) / _reserve0, amount1.mul(_totalSupply) / _reserve1); Math.min(amount0.mul(_totalSupply) / _reserve0, amount1.mul(_totalSupply) / _reserve1);
@ -108,21 +108,23 @@ contract UniswapV2 is IUniswapV2, ERC20("Uniswap V2", "UNI-V2", 18, 0) {
_mint(to, liquidity); _mint(to, liquidity);
_update(balance0, balance1, _reserve0, _reserve1); _update(balance0, balance1, _reserve0, _reserve1);
if (feeOn) invariantLast = Math.sqrt(uint(reserve0).mul(reserve1));
emit Mint(msg.sender, amount0, amount1); emit Mint(msg.sender, amount0, amount1);
} }
function burn(address to) external lock returns (uint amount0, uint amount1) { function burn(address to) external lock returns (uint amount0, uint amount1) {
uint _totalSupply = totalSupply; // for gas savings uint _totalSupply = totalSupply; // for gas savings
uint112 _reserve0 = reserve0; // for gas savings
uint112 _reserve1 = reserve1; // for gas savings
address _token0 = token0; // for gas savings address _token0 = token0; // for gas savings
address _token1 = token1; // for gas savings address _token1 = token1; // for gas savings
uint balance0 = IERC20(_token0).balanceOf(address(this)); uint balance0 = IERC20(_token0).balanceOf(address(this));
uint balance1 = IERC20(_token1).balanceOf(address(this)); uint balance1 = IERC20(_token1).balanceOf(address(this));
uint liquidity = balanceOf[address(this)]; uint liquidity = balanceOf[address(this)];
_mintFee(balance0, balance1); bool feeOn = _mintFee(_reserve0, _reserve1);
// use balances instead of reserves to address edges cases amount0 = liquidity.mul(balance0) / _totalSupply; // use balances instead of reserves to address edges case
amount0 = liquidity.mul(balance0) / _totalSupply; amount1 = liquidity.mul(balance1) / _totalSupply; // use balances instead of reserves to address edges case
amount1 = liquidity.mul(balance1) / _totalSupply;
require(amount0 > 0 && amount1 > 0, "UniswapV2: INSUFFICIENT_LIQUIDITY_BURNED"); require(amount0 > 0 && amount1 > 0, "UniswapV2: INSUFFICIENT_LIQUIDITY_BURNED");
_safeTransfer(_token0, to, amount0); _safeTransfer(_token0, to, amount0);
_safeTransfer(_token1, to, amount1); _safeTransfer(_token1, to, amount1);
@ -130,15 +132,16 @@ contract UniswapV2 is IUniswapV2, ERC20("Uniswap V2", "UNI-V2", 18, 0) {
balance1 = IERC20(_token1).balanceOf(address(this)); balance1 = IERC20(_token1).balanceOf(address(this));
_burn(address(this), liquidity); _burn(address(this), liquidity);
_update(balance0, balance1, reserve0_, reserve1_); _update(balance0, balance1, _reserve0, _reserve1);
if (feeOn) invariantLast = Math.sqrt(uint(reserve0).mul(reserve1));
emit Burn(msg.sender, amount0, amount1, to); emit Burn(msg.sender, amount0, amount1, to);
} }
function swap(address tokenIn, uint amountOut, address to) external lock { function swap(address tokenIn, uint amountOut, address to) external lock {
address _token0 = token0; // for gas savings uint112 _reserve0 = reserve0; // for gas savings
address _token1 = token1; // for gas savings uint112 _reserve1 = reserve1; // for gas savings
uint112 _reserve0 = reserve0_; // for gas savings address _token0 = token0; // for gas savings
uint112 _reserve1 = reserve1_; // for gas savings address _token1 = token1; // for gas savings
uint balance0; uint balance1; uint amountIn; uint balance0; uint balance1; uint amountIn;
if (tokenIn == _token0) { if (tokenIn == _token0) {
@ -168,12 +171,12 @@ contract UniswapV2 is IUniswapV2, ERC20("Uniswap V2", "UNI-V2", 18, 0) {
function skim(address to) external lock { function skim(address to) external lock {
address _token0 = token0; // for gas savings address _token0 = token0; // for gas savings
address _token1 = token1; // for gas savings address _token1 = token1; // for gas savings
_safeTransfer(_token0, to, IERC20(_token0).balanceOf(address(this)).sub(reserve0_)); _safeTransfer(_token0, to, IERC20(_token0).balanceOf(address(this)).sub(reserve0));
_safeTransfer(_token1, to, IERC20(_token1).balanceOf(address(this)).sub(reserve1_)); _safeTransfer(_token1, to, IERC20(_token1).balanceOf(address(this)).sub(reserve1));
} }
// force reserves to match balances // force reserves to match balances
function sync() external lock { function sync() external lock {
_update(IERC20(token0).balanceOf(address(this)), IERC20(token1).balanceOf(address(this)), reserve0_, reserve1_); _update(IERC20(token0).balanceOf(address(this)), IERC20(token1).balanceOf(address(this)), reserve0, reserve1);
} }
} }