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Outline

•  contract ImmutableCreate2Factory *
•    - function safeCreate2(
•    - function findCreate2Address(
•    - function findCreate2AddressViaHash(
•    - function hasBeenDeployed(

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/**
 *Submitted for verification at Etherscan.io on 2022-12-05
*/

/**
 *Submitted for verification at Etherscan.io on 2019-07-30
*/

pragma solidity 0.5.16; // optimization enabled, 99999 runs, evm: petersburg


/**
 * @title Immutable Create2 Contract Factory
 * @author 0age
 * @notice This contract provides a safeCreate2 function that takes a salt value
 * and a block of initialization code as arguments and passes them into inline
 * assembly. The contract prevents redeploys by maintaining a mapping of all
 * contracts that have already been deployed, and prevents frontrunning or other
 * collisions by requiring that the first 20 bytes of the salt are equal to the
 * address of the caller (this can be bypassed by setting the first 20 bytes to
 * the null address). There is also a view function that computes the address of
 * the contract that will be created when submitting a given salt or nonce along
 * with a given block of initialization code.
 * @dev This contract has not yet been fully tested or audited - proceed with
 * caution and please share any exploits or optimizations you discover.
 */
contract ImmutableCreate2Factory {
    // mapping to track which addresses have already been deployed.
    mapping(address => bool) private _deployed;

    /**
     * @dev Create a contract using CREATE2 by submitting a given salt or nonce
   * along with the initialization code for the contract. Note that the first 20
   * bytes of the salt must match those of the calling address, which prevents
   * contract creation events from being submitted by unintended parties.
   * @param salt bytes32 The nonce that will be passed into the CREATE2 call.
   * @param initializationCode bytes The initialization code that will be passed
   * into the CREATE2 call.
   * @return Address of the contract that will be created, or the null address
   * if a contract already exists at that address.
   */
    function safeCreate2(
        bytes32 salt,
        bytes calldata initializationCode
    ) external payable containsCaller(salt) returns (address deploymentAddress) {
        // move the initialization code from calldata to memory.
        bytes memory initCode = initializationCode;

        // determine the target address for contract deployment.
        address targetDeploymentAddress = address(
            uint160(                    // downcast to match the address type.
                uint256(                  // convert to uint to truncate upper digits.
                    keccak256(              // compute the CREATE2 hash using 4 inputs.
                        abi.encodePacked(     // pack all inputs to the hash together.
                            hex"ff",            // start with 0xff to distinguish from RLP.
                            address(this),      // this contract will be the caller.
                            salt,               // pass in the supplied salt value.
                            keccak256(          // pass in the hash of initialization code.
                                abi.encodePacked(
                                    initCode
                                )
                            )
                        )
                    )
                )
            )
        );

        // ensure that a contract hasn't been previously deployed to target address.
        require(
            !_deployed[targetDeploymentAddress],
            "Invalid contract creation - contract has already been deployed."
        );

        // using inline assembly: load data and length of data, then call CREATE2.
        assembly {                                // solhint-disable-line
            let encoded_data := add(0x20, initCode) // load initialization code.
            let encoded_size := mload(initCode)     // load the init code's length.
            deploymentAddress := create2(           // call CREATE2 with 4 arguments.
            callvalue,                            // forward any attached value.
            encoded_data,                         // pass in initialization code.
            encoded_size,                         // pass in init code's length.
            salt                                  // pass in the salt value.
            )
        }

        // check address against target to ensure that deployment was successful.
        require(
            deploymentAddress == targetDeploymentAddress,
            "Failed to deploy contract using provided salt and initialization code."
        );

        // record the deployment of the contract to prevent redeploys.
        _deployed[deploymentAddress] = true;
    }

    /**
     * @dev Compute the address of the contract that will be created when
   * submitting a given salt or nonce to the contract along with the contract's
   * initialization code. The CREATE2 address is computed in accordance with
   * EIP-1014, and adheres to the formula therein of
   * `keccak256( 0xff ++ address ++ salt ++ keccak256(init_code)))[12:]` when
   * performing the computation. The computed address is then checked for any
   * existing contract code - if so, the null address will be returned instead.
   * @param salt bytes32 The nonce passed into the CREATE2 address calculation.
   * @param initCode bytes The contract initialization code to be used.
   * that will be passed into the CREATE2 address calculation.
   * @return Address of the contract that will be created, or the null address
   * if a contract has already been deployed to that address.
   */
    function findCreate2Address(
        bytes32 salt,
        bytes calldata initCode
    ) external view returns (address deploymentAddress) {
        // determine the address where the contract will be deployed.
        deploymentAddress = address(
            uint160(                      // downcast to match the address type.
                uint256(                    // convert to uint to truncate upper digits.
                    keccak256(                // compute the CREATE2 hash using 4 inputs.
                        abi.encodePacked(       // pack all inputs to the hash together.
                            hex"ff",              // start with 0xff to distinguish from RLP.
                            address(this),        // this contract will be the caller.
                            salt,                 // pass in the supplied salt value.
                            keccak256(            // pass in the hash of initialization code.
                                abi.encodePacked(
                                    initCode
                                )
                            )
                        )
                    )
                )
            )
        );

        // return null address to signify failure if contract has been deployed.
        if (_deployed[deploymentAddress]) {
            return address(0);
        }
    }

    /**
     * @dev Compute the address of the contract that will be created when
   * submitting a given salt or nonce to the contract along with the keccak256
   * hash of the contract's initialization code. The CREATE2 address is computed
   * in accordance with EIP-1014, and adheres to the formula therein of
   * `keccak256( 0xff ++ address ++ salt ++ keccak256(init_code)))[12:]` when
   * performing the computation. The computed address is then checked for any
   * existing contract code - if so, the null address will be returned instead.
   * @param salt bytes32 The nonce passed into the CREATE2 address calculation.
   * @param initCodeHash bytes32 The keccak256 hash of the initialization code
   * that will be passed into the CREATE2 address calculation.
   * @return Address of the contract that will be created, or the null address
   * if a contract has already been deployed to that address.
   */
    function findCreate2AddressViaHash(
        bytes32 salt,
        bytes32 initCodeHash
    ) external view returns (address deploymentAddress) {
        // determine the address where the contract will be deployed.
        deploymentAddress = address(
            uint160(                      // downcast to match the address type.
                uint256(                    // convert to uint to truncate upper digits.
                    keccak256(                // compute the CREATE2 hash using 4 inputs.
                        abi.encodePacked(       // pack all inputs to the hash together.
                            hex"ff",              // start with 0xff to distinguish from RLP.
                            address(this),        // this contract will be the caller.
                            salt,                 // pass in the supplied salt value.
                            initCodeHash          // pass in the hash of initialization code.
                        )
                    )
                )
            )
        );

        // return null address to signify failure if contract has been deployed.
        if (_deployed[deploymentAddress]) {
            return address(0);
        }
    }

    /**
     * @dev Determine if a contract has already been deployed by the factory to a
   * given address.
   * @param deploymentAddress address The contract address to check.
   * @return True if the contract has been deployed, false otherwise.
   */
    function hasBeenDeployed(
        address deploymentAddress
    ) external view returns (bool) {
        // determine if a contract has been deployed to the provided address.
        return _deployed[deploymentAddress];
    }

    /**
     * @dev Modifier to ensure that the first 20 bytes of a submitted salt match
   * those of the calling account. This provides protection against the salt
   * being stolen by frontrunners or other attackers. The protection can also be
   * bypassed if desired by setting each of the first 20 bytes to zero.
   * @param salt bytes32 The salt value to check against the calling address.
   */
    modifier containsCaller(bytes32 salt) {
        // prevent contract submissions from being stolen from tx.pool by requiring
        // that the first 20 bytes of the submitted salt match msg.sender.
        require(
            (address(bytes20(salt)) == msg.sender) ||
            (bytes20(salt) == bytes20(0)),
            "Invalid salt - first 20 bytes of the salt must match calling address."
        );
        _;
    }
}

• No Contract Security Audit Submitted- Submit Audit Here

[{"constant":true,"inputs":[{"internalType":"bytes32","name":"salt","type":"bytes32"},{"internalType":"bytes","name":"initCode","type":"bytes"}],"name":"findCreate2Address","outputs":[{"internalType":"address","name":"deploymentAddress","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"bytes32","name":"salt","type":"bytes32"},{"internalType":"bytes32","name":"initCodeHash","type":"bytes32"}],"name":"findCreate2AddressViaHash","outputs":[{"internalType":"address","name":"deploymentAddress","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"deploymentAddress","type":"address"}],"name":"hasBeenDeployed","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"bytes32","name":"salt","type":"bytes32"},{"internalType":"bytes","name":"initializationCode","type":"bytes"}],"name":"safeCreate2","outputs":[{"internalType":"address","name":"deploymentAddress","type":"address"}],"payable":true,"stateMutability":"payable","type":"function"}]

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