Openzepplin contracts imported. solidity version upgraded

contracts/FxChild.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 // IStateReceiver represents interface to receive state
 interface IStateReceiver {

contracts/FxRoot.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 
 interface IStateSender {

contracts/examples/erc1155-transfer/FxERC1155ChildTunnel.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import {IFxERC1155} from "../../tokens/IFxERC1155.sol";
 import {ERC1155Holder} from "../../lib/ERC1155Holder.sol" ;

contracts/examples/erc1155-transfer/FxERC1155RootTunnel.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import {ERC1155} from "../../lib/ERC1155.sol";
 import {ERC1155Holder} from "../../lib/ERC1155Holder.sol" ;

contracts/examples/erc20-transfer/FxERC20ChildTunnel.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import { FxBaseChildTunnel } from '../../tunnel/FxBaseChildTunnel.sol';
 import { Create2 } from '../../lib/Create2.sol';

contracts/examples/erc20-transfer/FxERC20RootTunnel.sol

@@ -1,10 +1,10 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import { ERC20 } from "../../lib/ERC20.sol";
 import { Create2 } from "../../lib/Create2.sol";
 import { FxBaseRootTunnel } from "../../tunnel/FxBaseRootTunnel.sol";
-import {SafeERC20} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
+import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
 
 /**
  * @title FxERC20RootTunnel

contracts/examples/erc721-transfer/FxERC721ChildTunnel.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import { FxBaseChildTunnel } from '../../tunnel/FxBaseChildTunnel.sol';
 import { Create2 } from '../../lib/Create2.sol';

contracts/examples/erc721-transfer/FxERC721RootTunnel.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import { ERC721 } from "../../lib/ERC721.sol";
 import { Create2 } from "../../lib/Create2.sol";

contracts/examples/mintable-erc20-transfer/FxMintableERC20ChildTunnel.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import { FxBaseChildTunnel } from '../../tunnel/FxBaseChildTunnel.sol';
 import { Create2 } from '../../lib/Create2.sol';

contracts/examples/mintable-erc20-transfer/FxMintableERC20RootTunnel.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import { Create2 } from "../../lib/Create2.sol";
 import { SafeMath } from "../../lib/SafeMath.sol";

contracts/examples/state-transfer/FxStateChildTunnel.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import { FxBaseChildTunnel } from '../../tunnel/FxBaseChildTunnel.sol';
 

contracts/examples/state-transfer/FxStateRootTunnel.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import { FxBaseRootTunnel } from '../../tunnel/FxBaseRootTunnel.sol';
 

contracts/lib/Address.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 /**
  * @dev Collection of functions related to the address type

contracts/lib/Context.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 /*
  * @dev Provides information about the current execution context, including the

contracts/lib/Create2.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 
 // Create2 adds common methods for minimal proxy with create2

contracts/lib/ERC1155.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import "./IERC1155.sol";
 import "./IERC1155Receiver.sol";

contracts/lib/ERC1155Holder.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import "./ERC1155Receiver.sol";
 

contracts/lib/ERC1155Receiver.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import "./IERC1155Receiver.sol";
 import "./ERC165.sol";

contracts/lib/ERC165.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import "./IERC165.sol";
 

contracts/lib/ERC20.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import { IERC20 } from './IERC20.sol';
 import { SafeMath } from './SafeMath.sol';

contracts/lib/ERC721.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import "./IERC721.sol";
 import "./IERC721Receiver.sol";

contracts/lib/IERC1155.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import "./IERC165.sol";
 

contracts/lib/IERC1155MetadataURI.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import "./IERC1155.sol";
 

contracts/lib/IERC1155Receiver.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import "./IERC165.sol";
 

contracts/lib/IERC165.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 /**
  * @dev Interface of the ERC165 standard, as defined in the

contracts/lib/IERC20.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 /**
  * @dev Interface of the ERC20 standard as defined in the EIP.

contracts/lib/IERC721.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import "./IERC165.sol";
 

contracts/lib/IERC721Metadata.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import "./IERC721.sol";
 

contracts/lib/IERC721Receiver.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 /**
  * @title ERC721 token receiver interface

contracts/lib/Merkle.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 library Merkle {
     function checkMembership(

contracts/lib/MerklePatriciaProof.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import {RLPReader} from "./RLPReader.sol";
 

contracts/lib/Ownable.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 /**
  * @dev Contract module which provides a basic access control mechanism, where

contracts/lib/RLPReader.sol

@@ -2,7 +2,7 @@
 * @author Hamdi Allam [email protected]
 * Please reach out with any questions or concerns
 */
-pragma solidity ^0.5.0;
+pragma solidity ^0.8.0;
 
 library RLPReader {
     uint8 constant STRING_SHORT_START = 0x80;
@@ -133,6 +133,13 @@ library RLPReader {
         return result;
     }
 
+    function payloadLocation(RLPItem memory item) internal pure returns (uint, uint) {
+        uint offset = _payloadOffset(item.memPtr);
+        uint memPtr = item.memPtr + offset;
+        uint len = item.len - offset; // data length
+        return (memPtr, len);
+    }
+
     /*
      * @dev A cheaper version of keccak256(toBytes(item)) that avoids copying memory.
      * @return keccak256 hash of the item payload.

contracts/lib/SafeMath.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 /**
  * @dev Wrappers over Solidity's arithmetic operations with added overflow

contracts/lib/Strings.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 /**
  * @dev String operations.

contracts/tokens/FxERC1155.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 import {ERC1155} from "../lib/ERC1155.sol";
 import {IFxERC1155} from "./IFxERC1155.sol";
 

contracts/tokens/FxERC20.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import { ERC20 } from "../lib/ERC20.sol";
 import { IFxERC20 } from "./IFxERC20.sol";

contracts/tokens/FxERC721.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 import { ERC721 } from "../lib/ERC721.sol";
 import { IFxERC721 } from "./IFxERC721.sol";

contracts/tokens/IFxERC1155.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 interface IFxERC1155 {
     function fxManager() external returns(address);

contracts/tokens/IFxERC20.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 interface IFxERC20 {
     function fxManager() external returns(address);

contracts/tokens/IFxERC721.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 interface IFxERC721 {
     function fxManager() external returns(address);

contracts/tunnel/FxBaseChildTunnel.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 // IFxMessageProcessor represents interface to process message
 interface IFxMessageProcessor {

contracts/tunnel/FxBaseRootTunnel.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.7.3;
+pragma solidity ^0.8.0;
 
 
 import {RLPReader} from "../lib/RLPReader.sol";

hardhat.config.js

@@ -22,7 +22,7 @@ module.exports = {
   solidity: {
     compilers: [
       {
-        version: "0.7.3"
+        version: "0.8.0"
       }
     ]
   }