Contract

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106

// SPDX-License-Identifier: MIT
pragma solidity 0.8.22;

/**
 * @title Proxy
 * @author Pragma Labs
 * @dev Implementation based on ERC1967: Proxy Storage Slots.
 * See https://eips.ethereum.org/EIPS/eip-1967.
 */
contract Proxy {
    /* //////////////////////////////////////////////////////////////
                                CONSTANTS
    ////////////////////////////////////////////////////////////// */

    // Storage slot with the address of the current implementation.
    // This is the hardcoded keccak-256 hash of: "eip1967.proxy.implementation" subtracted by 1.
    bytes32 internal constant IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;

    /* //////////////////////////////////////////////////////////////
                                STORAGE
    ////////////////////////////////////////////////////////////// */

    // Storage slot for the Account logic, a struct to avoid storage conflict when dealing with upgradeable contracts.
    struct AddressSlot {
        address value;
    }

    /* //////////////////////////////////////////////////////////////
                                EVENTS
    ////////////////////////////////////////////////////////////// */

    event Upgraded(address indexed implementation);

    /* //////////////////////////////////////////////////////////////
                            CONSTRUCTOR
    ////////////////////////////////////////////////////////////// */

    /**
     * @param implementation The contract address of the Account logic.
     */
    constructor(address implementation) payable {
        _getAddressSlot(IMPLEMENTATION_SLOT).value = implementation;
        emit Upgraded(implementation);
    }

    /**
     * @dev Fallback function that delegates calls to the implementation address.
     * Will run if call data is empty.
     */
    receive() external payable virtual {
        _delegate(_getAddressSlot(IMPLEMENTATION_SLOT).value);
    }

    /**
     * @dev Fallback function that delegates calls to the implementation address.
     * Will run if no other function in the contract matches the call data.
     */
    fallback() external payable virtual {
        _delegate(_getAddressSlot(IMPLEMENTATION_SLOT).value);
    }

    /*///////////////////////////////////////////////////////////////
                        IMPLEMENTATION LOGIC
    ///////////////////////////////////////////////////////////////*/

    /**
     * @notice Returns the "AddressSlot" with member "value" located at "slot".
     * @param slot The slot where the address of the Logic contract is stored.
     * @return r The address stored in slot.
     */
    function _getAddressSlot(bytes32 slot) internal pure returns (AddressSlot storage r) {
        assembly {
            r.slot := slot
        }
    }

    /*///////////////////////////////////////////////////////////////
                          DELEGATION LOGIC
    ///////////////////////////////////////////////////////////////*/

    /**
     * @param implementation The contract address of the logic.
     * @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()) }
        }
    }
}