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pragma solidity ^0.4.24;
/**
* @title Proxy
* @dev Implements delegation of calls to other contracts, with proper
* forwarding of return values and bubbling of failures.
* It defines a fallback function that delegates all calls to the address
* returned by the abstract _implementation() internal function.
*/
contract Proxy {
/**
* @dev Fallback function.
* Implemented entirely in `_fallback`.
*/
function () payable external {
_fallback();
}
/**
* @return The Address of the implementation.
*/
function _implementation() internal view returns (address);
/**
* @dev Delegates execution to an implementation contract.
* This is a low level function that doesn't return to its internal call site.
* It will return to the external caller whatever the implementation returns.
* @param implementation Address to delegate.
*/
function _delegate(address implementation) internal {
assembly {
// Copy msg.data. We take full control of memory in this inline assembly
// block because it will not return to Solidity code. We overwrite the
// Solidity scratch pad at memory position 0.
calldatacopy(0, 0, calldatasize)
// Call the implementation.
// out and outsize are 0 because we don't know the size yet.
let result := delegatecall(gas, implementation, 0, calldatasize, 0, 0)
// Copy the returned data.
returndatacopy(0, 0, returndatasize)
switch result
// delegatecall returns 0 on error.
case 0 { revert(0, returndatasize) }
default { return(0, returndatasize) }
}
}
/**
* @dev Function that is run as the first thing in the fallback function.
* Can be redefined in derived contracts to add functionality.
* Redefinitions must call super._willFallback().
*/
function _willFallback() internal {
}
/**
* @dev fallback implementation.
* Extracted to enable manual triggering.
*/
function _fallback() internal {
_willFallback();
_delegate(_implementation());
}
}