update approve logic

2020-11-16 10:54:05 +08:00
parent c827514ee7
commit bd21a14b53
3 changed files with 19 additions and 8 deletions
--- a/contracts/lib/UniversalERC20.sol
+++ b/contracts/lib/UniversalERC20.sol
@@ -43,7 +43,18 @@ library UniversalERC20 {

    function universalApprove(IERC20 token, address to, uint256 amount) internal {
        if (token != ZERO_ADDRESS && token != ETH_ADDRESS) {
-            token.safeApprove(to, amount);
+            if (amount == 0) {
+                token.safeApprove(to, 0);
+                return;
+            }
+
+            uint256 allowance = token.allowance(address(this), to);
+            if (allowance < amount) {
+                if (allowance > 0) {
+                    token.safeApprove(to, 0);
+                }
+                token.safeApprove(to, amount);
+            }
        }
    }