add GSP

contracts/DODOGasSavingPool/lib/DecimalMath.sol

@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity 0.8.16;
+pragma experimental ABIEncoderV2;
+
+import {Math} from "@openzeppelin/contracts/utils/math/Math.sol";
+
+/**
+ * @title DecimalMath
+ * @author DODO Breeder
+ *
+ * @notice Functions for fixed point number with 18 decimals
+ */
+
+library DecimalMath {
+    uint256 internal constant ONE = 10 ** 18;
+    uint256 internal constant ONE2 = 10 ** 36;
+
+    function mul(uint256 target, uint256 d) internal pure returns (uint256) {
+        return target * d / (10 ** 18);
+    }
+
+    function mulFloor(uint256 target, uint256 d) internal pure returns (uint256) {
+        return target * d / (10 ** 18);
+    }
+
+    function mulCeil(uint256 target, uint256 d) internal pure returns (uint256) {
+        return _divCeil(target * d, 10 ** 18);
+    }
+
+    function div(uint256 target, uint256 d) internal pure returns (uint256) {
+        return target * (10 ** 18) / d;
+    }
+
+    function divFloor(uint256 target, uint256 d) internal pure returns (uint256) {
+        return target * (10 ** 18) / d;
+    }
+
+    function divCeil(uint256 target, uint256 d) internal pure returns (uint256) {
+        return _divCeil(target * (10 ** 18), d);
+    }
+
+    function reciprocalFloor(uint256 target) internal pure returns (uint256) {
+        return uint256(10 ** 36) / target;
+    }
+
+    function reciprocalCeil(uint256 target) internal pure returns (uint256) {
+        return _divCeil(uint256(10 ** 36), target);
+    }
+
+    function sqrt(uint256 target) internal pure returns (uint256) {
+        return Math.sqrt(target * ONE);
+    }
+
+    function powFloor(uint256 target, uint256 e) internal pure returns (uint256) {
+        if (e == 0) {
+            return 10 ** 18;
+        } else if (e == 1) {
+            return target;
+        } else {
+            uint256 p = powFloor(target, e / 2);
+            p = p * p / (10 ** 18);
+            if (e % 2 == 1) {
+                p = p * target / (10 ** 18);
+            }
+            return p;
+        }
+    }
+
+    function _divCeil(uint256 a, uint256 b) internal pure returns (uint256) {
+        uint256 quotient = a / b;
+        uint256 remainder = a - quotient * b;
+        if (remainder > 0) {
+            return quotient + 1;
+        } else {
+            return quotient;
+        }
+    }
+}