Create StringUtils.sol

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

@@ -0,0 +1,20 @@
+pragma solidity ^0.8.0;
+
+library StringUtils {
+    function concat(string memory _a, string memory _b) internal pure returns (string memory) {
+        return string(abi.encodePacked(_a, _b));
+    }
+
+    function substring(string memory _str, uint256 _start, uint256 _end) internal pure returns (string memory) {
+        bytes memory strBytes = bytes(_str);
+        bytes memory result = new bytes(_end - _start);
+        for (uint256 i = _start; i < _end; i++) {
+            result[i - _start] = strBytes[i];
+        }
+        return string(result);
+    }
+
+    function compare(string memory _a, string memory _b) internal pure returns (bool) {
+        return keccak256(abi.encodePacked(_a)) == keccak256(abi.encodePacked(_b));
+    }
+}