Created
November 19, 2018 08:50
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pragma solidity ^0.4.21; | |
import './Proxy.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 | |
*/ | |
function UpgradeabilityProxy() 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 { | |
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); | |
} | |
} |
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