Merge pull request #25 from Sean329/main

Fixed a potential mistake in the fee calculation with round up
dragonfly-xyz · Nov 21, 2023 · f2a68ea · f2a68ea
2 parents 923763f + 178fa9f
commit f2a68ea
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diff --git a/patterns/flash-loans/FlashLoanPool.sol b/patterns/flash-loans/FlashLoanPool.sol
@@ -48,7 +48,7 @@ contract FlashLoanPool {
         uint256 balanceBefore = token.balanceOf(address(this));
         require(balanceBefore >= borrowAmount, 'too much');
         // Compute the fee, rounded up.
-        uint256 fee = FEE_BPS * (borrowAmount + 1e4-1) / 1e4;
+        uint256 fee = (FEE_BPS * borrowAmount + 1e4-1) / 1e4;
         // Transfer tokens to the borrower contract.
         token.transfer(address(borrower), borrowAmount);
         // Let the borrower do its thing.

diff --git a/patterns/flash-loans/README.md b/patterns/flash-loans/README.md
@@ -76,7 +76,7 @@ function flashLoan(
     uint256 balanceBefore = token.balanceOf(address(this));
     require(balanceBefore >= borrowAmount, 'too much');
     // Compute the fee, rounded up.
-    uint256 fee = FEE_BPS * (borrowAmount + 1e4-1) / 1e4;
+    uint256 fee = (FEE_BPS * borrowAmount + 1e4-1) / 1e4;
     // Transfer tokens to the borrower contract.
     token.transfer(address(borrower), borrowAmount);
     // Let the borrower do its thing.

diff --git a/test/FlashLoanPool.t.sol b/test/FlashLoanPool.t.sol
@@ -161,7 +161,7 @@ contract FlashLoanPoolTest is TestUtils, FlashLoanValidator {
     }
 
     function _getFee(uint256 amount) private view returns (uint256) {
-        return pool.FEE_BPS() * (amount + 1e4-1) / 1e4;
+        return (pool.FEE_BPS() * amount + 1e4-1) / 1e4;
     }
 
     function test_canWithdraw() external {