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pragma solidity ^0.4.24;
import './Proxy.sol';
import 'openzeppelin-solidity/contracts/AddressUtils.sol';
/**
* @title UpgradeabilityProxy
* @dev This contract implements a proxy that allows to change the
* implementation address to which it will delegate.
* Such a change is called an implementation upgrade.
*/
contract UpgradeabilityProxy is Proxy {
/**
* @dev Emitted when the implementation is upgraded.
* @param implementation Address of the new implementation.
*/
event Upgraded(address indexed implementation);
/**
* @dev Storage slot with the address of the current implementation.
* This is the keccak-256 hash of "org.zeppelinos.proxy.implementation", and is
* validated in the constructor.
*/
bytes32 private constant IMPLEMENTATION_SLOT = 0x7050c9e0f4ca769c69bd3a8ef740bc37934f8e2c036e5a723fd8ee048ed3f8c3;
/**
* @dev Contract constructor.
* @param _implementation Address of the initial implementation.
* @param _data Data to send as msg.data to the implementation to initialize the proxied contract.
* It should include the signature and the parameters of the function to be called, as described in
* https://solidity.readthedocs.io/en/v0.4.24/abi-spec.html#function-selector-and-argument-encoding.
* This parameter is optional, if no data is given the initialization call to proxied contract will be skipped.
*/
constructor(address _implementation, bytes _data) public payable {
assert(IMPLEMENTATION_SLOT == keccak256("org.zeppelinos.proxy.implementation"));
_setImplementation(_implementation);
if(_data.length > 0) {
require(_implementation.delegatecall(_data));
}
}
/**
* @dev Returns the current implementation.
* @return Address of the current implementation
*/
function _implementation() internal view returns (address impl) {
bytes32 slot = IMPLEMENTATION_SLOT;
assembly {
impl := sload(slot)
}
}
/**
* @dev Upgrades the proxy to a new implementation.
* @param newImplementation Address of the new implementation.
*/
function _upgradeTo(address newImplementation) internal {
_setImplementation(newImplementation);
emit Upgraded(newImplementation);
}
/**
* @dev Sets the implementation address of the proxy.
* @param newImplementation Address of the new implementation.
*/
function _setImplementation(address newImplementation) private {
require(AddressUtils.isContract(newImplementation), "Cannot set a proxy implementation to a non-contract address");
bytes32 slot = IMPLEMENTATION_SLOT;
assembly {
sstore(slot, newImplementation)
}
}
}