智能合约根据逻辑来编写和运作。只要满足输入要求,也就是说只要代码编写的要求被满足,合约中的义务将在安全和去信任的网络中得到执行。
UpgradeabilityProxy.sol
import './Proxy.sol';
import './Address.sol';
/**
* @title UpgradeabilityProxy
* @dev This contract represents a proxy where the implementation address to which it will delegate can be upgraded
*/
contract UpgradeabilityProxy is Proxy {
/**
* @dev This event will be emitted every time the implementation gets upgraded
* @param implementation representing the address of the upgraded implementation
*/
event Upgraded(address indexed implementation);
// Storage position of the address of the current implementation
bytes32 private constant implementationPosition = keccak256("org.zeppelinos.proxy.implementation");
/**
* @dev Constructor function
*/
constructor() public {}
/**
* @dev Tells the address of the current implementation
* @return address of the current implementation
*/
function implementation() public view returns (address impl) {
bytes32 position = implementationPosition;
assembly {
impl := sload(position)
}
}
/**
* @dev Sets the address of the current implementation
* @param newImplementation address representing the new implementation to be set
*/
function setImplementation(address newImplementation) internal {
require(Address.isContract(newImplementation),"newImplementation is not a contractAddress");
bytes32 position = implementationPosition;
assembly {
sstore(position, newImplementation)
}
}
/**
* @dev Upgrades the implementation address
* @param newImplementation representing the address of the new implementation to be set
*/
function _upgradeTo(address newImplementation) internal {
address currentImplementation = implementation();
require(currentImplementation != newImplementation);
setImplementation(newImplementation);
emit Upgraded(newImplementation);
}
}