Create SafeMath.sol

blockchain_integration/pi_network/contracts/PI-bank/libraries/SafeMath.sol

@@ -0,0 +1,28 @@
+pragma solidity ^0.8.0;
+
+library SafeMath {
+    function add(uint256 a, uint256 b) internal pure returns (uint256) {
+        uint256 c = a + b;
+        require(c >= a, "SafeMath: addition overflow");
+        return c;
+    }
+
+    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
+        require(b <= a, "SafeMath: subtraction underflow");
+        return a - b;
+    }
+
+    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
+        if (a == 0) {
+            return 0;
+        }
+        uint256 c = a * b;
+        require(c / a == b, "SafeMath: multiplication overflow");
+        return c;
+    }
+
+    function div(uint256 a, uint256 b) internal pure returns (uint256) {
+        require(b > 0, "SafeMath: division by zero");
+        return a / b;
+    }
+}