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79 lines
2.4 KiB
79 lines
2.4 KiB
4 years ago
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// SPDX-License-Identifier: MIT
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pragma solidity ^0.6.0;
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/**
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* @title Proxy
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* @dev Implements delegation of calls to other contracts, with proper
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* forwarding of return values and bubbling of failures.
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* It defines a fallback function that delegates all calls to the address
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* returned by the abstract _implementation() internal function.
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*/
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abstract contract Proxy {
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/**
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* @dev Fallback function.
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* Implemented entirely in `_fallback`.
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*/
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fallback () payable external {
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_fallback();
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}
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/**
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* @dev Receive function.
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* Implemented entirely in `_fallback`.
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*/
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receive () payable external {
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_fallback();
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}
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/**
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* @return The Address of the implementation.
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*/
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function _implementation() internal virtual view returns (address);
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/**
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* @dev Delegates execution to an implementation contract.
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* This is a low level function that doesn't return to its internal call site.
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* It will return to the external caller whatever the implementation returns.
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* @param implementation Address to delegate.
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*/
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function _delegate(address implementation) internal {
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// solhint-disable-next-line no-inline-assembly
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assembly {
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// Copy msg.data. We take full control of memory in this inline assembly
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// block because it will not return to Solidity code. We overwrite the
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// Solidity scratch pad at memory position 0.
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calldatacopy(0, 0, calldatasize())
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// Call the implementation.
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// out and outsize are 0 because we don't know the size yet.
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let result := delegatecall(gas(), implementation, 0, calldatasize(), 0, 0)
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// Copy the returned data.
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returndatacopy(0, 0, returndatasize())
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switch result
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// delegatecall returns 0 on error.
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case 0 { revert(0, returndatasize()) }
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default { return(0, returndatasize()) }
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}
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}
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/**
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* @dev Function that is run as the first thing in the fallback function.
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* Can be redefined in derived contracts to add functionality.
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* Redefinitions must call super._willFallback().
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*/
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function _willFallback() internal virtual {
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}
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/**
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* @dev fallback implementation.
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* Extracted to enable manual triggering.
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*/
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function _fallback() internal {
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_willFallback();
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_delegate(_implementation());
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}
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}
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