NoBey/uniswap-v2
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clean up fee minting

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This commit is contained in:
Noah Zinsmeister
2020-01-02 18:01:30 -05:00
parent baa8ccb5dc
commit 3395f3c56c
1 changed files with 26 additions and 20 deletions
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46
contracts/UniswapV2.sol
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@ -56,27 +56,33 @@ contract UniswapV2 is IUniswapV2, ERC20("Uniswap V2", "UNI-V2", 18, 0) {
require(balance0 <= uint112(-1) && balance1 <= uint112(-1), "UniswapV2: BALANCE_OVERFLOW");
uint32 blockNumber = uint32(block.number % 2**32);
uint32 blocksElapsed = blockNumber - blockNumberLast; // overflow is desired
if (reserve0 != 0 && reserve1 != 0 && blocksElapsed > 0) {
if (blocksElapsed > 0 && reserve0 != 0 && reserve1 != 0) {
// * never overflows, and + overflow is desired
price0CumulativeLast += uint(UQ112x112.encode(reserve1).qdiv(reserve0)) * blocksElapsed;
price1CumulativeLast += uint(UQ112x112.encode(reserve0).qdiv(reserve1)) * blocksElapsed;
}
// ↓↓↓↓ single SSTORE ↓↓↓↓
reserve0 = uint112(balance0);
reserve1 = uint112(balance1);
blockNumberLast = blockNumber;
// ↑↑↑↑ single SSTORE ↑↑↑↑
emit Sync(reserve0, reserve1);
}
// mint liquidity equivalent to 20% of accumulated fees
function _mintFeeLiquidity(address feeTo) private {
if (feeTo != address(0) && invariantLast != 0) {
uint invariant = Math.sqrt(uint(reserve0).mul(reserve1));
if (invariant > invariantLast) {
uint numerator = totalSupply.mul(invariant.sub(invariantLast));
uint denominator = uint(4).mul(invariant).add(invariantLast);
uint liquidity = numerator / denominator;
if (liquidity > 0) _mint(feeTo, liquidity);
// mint liquidity equivalent to 20% of newly accumulated fees
function _mintFee(uint invariantNext) private {
address feeTo = IUniswapV2Factory(factory).feeTo();
if (feeTo != address(0)) {
if (invariantLast != 0) {
uint invariant = Math.sqrt(uint(reserve0).mul(reserve1));
if (invariant > invariantLast) {
uint numerator = totalSupply.mul(invariant.sub(invariantLast));
uint denominator = uint(4).mul(invariant).add(invariantLast);
uint liquidity = numerator / denominator;
if (liquidity > 0) _mint(feeTo, liquidity);
}
}
invariantLast = invariantNext;
}
}
@ -86,8 +92,7 @@ contract UniswapV2 is IUniswapV2, ERC20("Uniswap V2", "UNI-V2", 18, 0) {
uint amount0 = balance0.sub(reserve0);
uint amount1 = balance1.sub(reserve1);
address feeTo = IUniswapV2Factory(factory).feeTo();
_mintFeeLiquidity(feeTo);
_mintFee(Math.sqrt(balance0.mul(balance1)));
liquidity = totalSupply == 0 ?
Math.sqrt(amount0.mul(amount1)) :
Math.min(amount0.mul(totalSupply) / reserve0, amount1.mul(totalSupply) / reserve1);
@ -95,25 +100,26 @@ contract UniswapV2 is IUniswapV2, ERC20("Uniswap V2", "UNI-V2", 18, 0) {
_mint(to, liquidity);
_update(balance0, balance1);
if (feeTo != address(0)) invariantLast = Math.sqrt(uint(reserve0).mul(reserve1));
emit Mint(msg.sender, amount0, amount1);
}
function burn(address to) external lock returns (uint amount0, uint amount1) {
uint balance0 = IERC20(token0).balanceOf(address(this));
uint balance1 = IERC20(token1).balanceOf(address(this));
uint liquidity = balanceOf[address(this)];
address feeTo = IUniswapV2Factory(factory).feeTo();
_mintFeeLiquidity(feeTo);
// there's a funny case here where if a token deflates uniswap's balance, we give too many tokens...
amount0 = liquidity.mul(reserve0) / totalSupply;
amount1 = liquidity.mul(reserve1) / totalSupply;
_mintFee(Math.sqrt(balance0.mul(balance1)));
// use balances instead of reserves to address edges cases
amount0 = liquidity.mul(balance0) / totalSupply;
amount1 = liquidity.mul(balance1) / totalSupply;
require(amount0 > 0 && amount1 > 0, "UniswapV2: INSUFFICIENT_LIQUIDITY_BURNED");
_safeTransfer(token0, to, amount0);
_safeTransfer(token1, to, amount1);
balance0 = IERC20(token0).balanceOf(address(this));
balance1 = IERC20(token1).balanceOf(address(this));
_burn(address(this), liquidity);
_update(IERC20(token0).balanceOf(address(this)), IERC20(token1).balanceOf(address(this)));
if (feeTo != address(0)) invariantLast = Math.sqrt(uint(reserve0).mul(reserve1));
_update(balance0, balance1);
emit Burn(msg.sender, amount0, amount1, to);
}