Address

• contracts/oz/proxy/Proxy.sol
• contracts/oz/utils/Address.sol
• contracts/oz/utils/StorageSlot.sol
• contracts/oz/proxy/beacon/IBeacon.sol
• contracts/oz/proxy/beacon/BeaconProxy.sol
• contracts/oz/interfaces/draft-IERC1822.sol
• contracts/oz/proxy/ERC1967/ERC1967Upgrade.sol

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (proxy/Proxy.sol)

pragma solidity ^0.8.0;

/**
 * @dev This abstract contract provides a fallback function that delegates all calls to another contract using the EVM
 * instruction `delegatecall`. We refer to the second contract as the _implementation_ behind the proxy, and it has to
 * be specified by overriding the virtual {_implementation} function.
 *
 * Additionally, delegation to the implementation can be triggered manually through the {_fallback} function, or to a
 * different contract through the {_delegate} function.
 *
 * The success and return data of the delegated call will be returned back to the caller of the proxy.
 */
abstract contract Proxy {
  /**
   * @dev Delegates the current call to `implementation`.
   *
   * This function does not return to its internal call site, it will return directly to the external caller.
   */
  function _delegate(address implementation) internal virtual {
    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 This is a virtual function that should be overriden so it returns the address to which the fallback function
   * and {_fallback} should delegate.
   */
  function _implementation() internal view virtual returns (address);

  /**
   * @dev Delegates the current call to the address returned by `_implementation()`.
   *
   * This function does not return to its internall call site, it will return directly to the external caller.
   */
  function _fallback() internal virtual {
    _beforeFallback();
    _delegate(_implementation());
  }

  /**
   * @dev Fallback function that delegates calls to the address returned by `_implementation()`. Will run if no other
   * function in the contract matches the call data.
   */
  fallback() external payable virtual {
    _fallback();
  }

  /**
   * @dev Fallback function that delegates calls to the address returned by `_implementation()`. Will run if call data
   * is empty.
   */
  receive() external payable virtual {
    _fallback();
  }

  /**
   * @dev Hook that is called before falling back to the implementation. Can happen as part of a manual `_fallback`
   * call, or as part of the Solidity `fallback` or `receive` functions.
   *
   * If overriden should call `super._beforeFallback()`.
   */
  function _beforeFallback() internal virtual {}
}