一、create2方法说明
create2
是以太坊上的一个特殊函数,用于在智能合约中创建新的合约实例。它是一种在特定地址上创建合约的方法,该地址是通过提供计算合约地址所需的参数(创建者地址、随机 salt 值)来计算得出的。
create2
方法的语法如下:
function create2(uint256 _value, bytes memory _code) public returns (address)
其中 _value
是要传递给合约构造函数的以太币数量, _code
是要部署的合约的字节码。
在调用 create2
函数时,以太坊虚拟机会将合约代码 _code
部署到一个新的地址上,并返回该地址。地址的计算方式是通过将创建者地址、salt 值和 _code
的 keccak256 哈希结果进行哈希计算而得到的。
create2
方法的主要优势在于,它可以根据特定的参数计算出合约地址,而不必实际执行合约的部署操作。这使得在智能合约中可以根据条件动态创建合约,并根据不同的参数在不同的地址上部署合约。这种方法可以带来更灵活和可预测的合约创建过程。
需要注意的是,create2
方法只在以太坊的某些硬分叉(如 Constantinople 分叉)之后才可用。在使用 create2
方法时,需要仔细评估安全性和风险,并确保对合约地址的计算方式有清晰的理解。
二、create2类库
使用以下create类库,可以方便的提前计算部署的合约地址,可以根据实际的需求,干预合约地址的生成,生成自己期望的合约地址。
// SPDX-License-Identifier: MIT // OpenZeppelin Contracts (last updated v4.8.0) (utils/Create2.sol) pragma solidity ^0.8.0; /** * @dev Helper to make usage of the `CREATE2` EVM opcode easier and safer. * `CREATE2` can be used to compute in advance the address where a smart * contract will be deployed, which allows for interesting new mechanisms known * as 'counterfactual interactions'. * * See the https://eips.ethereum.org/EIPS/eip-1014#motivation[EIP] for more * information. */ library Create2 { /** * @dev Deploys a contract using `CREATE2`. The address where the contract * will be deployed can be known in advance via {computeAddress}. * * The bytecode for a contract can be obtained from Solidity with * `type(contractName).creationCode`. * * Requirements: * * - `bytecode` must not be empty. * - `salt` must have not been used for `bytecode` already. * - the factory must have a balance of at least `amount`. * - if `amount` is non-zero, `bytecode` must have a `payable` constructor. */ function deploy(uint256 amount, bytes32 salt, bytes memory bytecode) internal returns (address addr) { require(address(this).balance >= amount, "Create2: insufficient balance"); require(bytecode.length != 0, "Create2: bytecode length is zero"); /// @solidity memory-safe-assembly assembly { addr := create2(amount, add(bytecode, 0x20), mload(bytecode), salt) } require(addr != address(0), "Create2: Failed on deploy"); } /** * @dev Returns the address where a contract will be stored if deployed via {deploy}. Any change in the * `bytecodeHash` or `salt` will result in a new destination address. */ function computeAddress(bytes32 salt, bytes32 bytecodeHash) internal view returns (address) { return computeAddress(salt, bytecodeHash, address(this)); } /** * @dev Returns the address where a contract will be stored if deployed via {deploy} from a contract located at * `deployer`. If `deployer` is this contract's address, returns the same value as {computeAddress}. */ function computeAddress(bytes32 salt, bytes32 bytecodeHash, address deployer) internal pure returns (address addr) { /// @solidity memory-safe-assembly assembly { let ptr := mload(0x40) // Get free memory pointer // | | ↓ ptr ... ↓ ptr + 0x0B (start) ... ↓ ptr + 0x20 ... ↓ ptr + 0x40 ... | // |-------------------|---------------------------------------------------------------------------| // | bytecodeHash | CCCCCCCCCCCCC...CC | // | salt | BBBBBBBBBBBBB...BB | // | deployer | 000000...0000AAAAAAAAAAAAAAAAAAA...AA | // | 0xFF | FF | // |-------------------|---------------------------------------------------------------------------| // | memory | 000000...00FFAAAAAAAAAAAAAAAAAAA...AABBBBBBBBBBBBB...BBCCCCCCCCCCCCC...CC | // | keccak(start, 85) | ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ | mstore(add(ptr, 0x40), bytecodeHash) mstore(add(ptr, 0x20), salt) mstore(ptr, deployer) // Right-aligned with 12 preceding garbage bytes let start := add(ptr, 0x0b) // The hashed data starts at the final garbage byte which we will set to 0xff mstore8(start, 0xff) addr := keccak256(start, 85) } } }
至此,完成solidity合约中使用create2方法提前计算部署的合约地址所有操作流程。
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