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sUSDS Base vs Mainnet

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// SPDX-License-Identifier: AGPL-3.0-or-later

/// SUsds.sol -- SUsds token

/// SUsds.sol

// This program is free software: you can redistribute it and/or modify

// it under the terms of the GNU Affero General Public License as published by

// the Free Software Foundation, either version 3 of the License, or

// (at your option) any later version.

// This program is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

// GNU Affero General Public License for more details.

// You should have received a copy of the GNU Affero General Public License

// along with this program. If not, see <https://www.gnu.org/licenses/>.

pragma solidity ^0.8.21;

import "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";

interface IERC1271 {

function isValidSignature(

bytes32,

bytes memory

) external view returns (bytes4);

}

interface VatLike {

function hope(address) external;

function suck(address, address, uint256) external;

}

interface UsdsJoinLike {

function vat() external view returns (address);

function usds() external view returns (address);

function exit(address, uint256) external;

}

interface UsdsLike {

function transfer(address, uint256) external;

function transferFrom(address, address, uint256) external;

}

contract SUsds is UUPSUpgradeable {

// --- Storage Variables ---

// Admin

mapping (address => uint256) public wards;

// ERC20

uint256 public totalSupply;

Text moved from lines 42-44

mapping (address => uint256) public balanceOf;

mapping (address => mapping (address => uint256)) public allowance;

mapping (address => uint256) public nonces;

// Savings yield

uint192 public chi; // The Rate Accumulator [ray]

uint64 public rho; // Time of last drip [unix epoch time]

uint256 public ssr; // The USDS Savings Rate [ray]

// --- ERC20 Data ---

// --- Constants ---

// ERC20

string public constant name = "Savings USDS";

string public constant symbol = "sUSDS";

string public constant version = "1";

uint8 public constant decimals = 18;

uint256 public totalSupply;

// Math

uint256 private constant RAY = 10 ** 27;

Text moved to lines 56-58

mapping (address => uint256) public balanceOf;

// --- Immutables ---

mapping (address => mapping (address => uint256)) public allowance;

mapping (address => uint256) public nonces;

// EIP712

bytes32 public constant PERMIT_TYPEHASH = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");

// Savings yield

UsdsJoinLike public immutable usdsJoin;

VatLike public immutable vat;

UsdsLike public immutable usds;

address public immutable vow;

// --- Events ---

// Admin

event Rely(address indexed usr);

event Deny(address indexed usr);

event File(bytes32 indexed what, uint256 data);

// ERC20

event Approval(address indexed owner, address indexed spender, uint256 value);

event Transfer(address indexed from, address indexed to, uint256 value);

// ERC4626

event Deposit(address indexed sender, address indexed owner, uint256 assets, uint256 shares);

event Withdraw(address indexed sender, address indexed receiver, address indexed owner, uint256 assets, uint256 shares);

// Referral

event Referral(uint16 indexed referral, address indexed owner, uint256 assets, uint256 shares);

// Savings yield

event Drip(uint256 chi, uint256 diff);

// --- EIP712 niceties ---

// --- Modifiers ---

bytes32 public constant PERMIT_TYPEHASH = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");

modifier auth {

require(wards[msg.sender] == 1, "SUsds/not-authorized");

}

constructor() {

// --- Constructor ---

constructor(address usdsJoin_, address vow_) {

_disableInitializers(); // Avoid initializing in the context of the implementation

usdsJoin = UsdsJoinLike(usdsJoin_);

vat = VatLike(UsdsJoinLike(usdsJoin_).vat());

usds = UsdsLike(UsdsJoinLike(usdsJoin_).usds());

vow = vow_;

}

// --- Upgradability ---

function initialize() initializer external {

__UUPSUpgradeable_init();

chi = uint192(RAY);

rho = uint64(block.timestamp);

ssr = RAY;

vat.hope(address(usdsJoin));

wards[msg.sender] = 1;

emit Rely(msg.sender);

}

function _authorizeUpgrade(address newImplementation) internal override auth {}

function getImplementation() external view returns (address) {

return ERC1967Utils.getImplementation();

}

// --- Internals ---

// EIP712

function _calculateDomainSeparator(uint256 chainId) private view returns (bytes32) {

return keccak256(

abi.encode(

keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),

keccak256(bytes(name)),

keccak256(bytes(version)),

chainId,

address(this)

)

);

}

function DOMAIN_SEPARATOR() external view returns (bytes32) {

return _calculateDomainSeparator(block.chainid);

}

// --- Administration ---

// Math

function _rpow(uint256 x, uint256 n) internal pure returns (uint256 z) {

assembly {

switch x case 0 {switch n case 0 {z := RAY} default {z := 0}}

default {

switch mod(n, 2) case 0 { z := RAY } default { z := x }

let half := div(RAY, 2) // for rounding.

for { n := div(n, 2) } n { n := div(n,2) } {

let xx := mul(x, x)

if iszero(eq(div(xx, x), x)) { revert(0,0) }

let xxRound := add(xx, half)

if lt(xxRound, xx) { revert(0,0) }

x := div(xxRound, RAY)

if mod(n,2) {

let zx := mul(z, x)

if and(iszero(iszero(x)), iszero(eq(div(zx, x), z))) { revert(0,0) }

let zxRound := add(zx, half)

if lt(zxRound, zx) { revert(0,0) }

z := div(zxRound, RAY)

}

function _divup(uint256 x, uint256 y) internal pure returns (uint256 z) {

// Note: _divup(0,0) will return 0 differing from natural solidity division

unchecked {

z = x != 0 ? ((x - 1) / y) + 1 : 0;

}

// --- Admin external functions ---

function rely(address usr) external auth {

wards[usr] = 1;

emit Rely(usr);

}

function deny(address usr) external auth {

wards[usr] = 0;

emit Deny(usr);

}

function file(bytes32 what, uint256 data) external auth {

if (what == "ssr") {

require(data >= RAY, "SUsds/wrong-ssr-value");

require(rho == block.timestamp, "SUsds/chi-not-up-to-date");

ssr = data;

} else revert("SUsds/file-unrecognized-param");

emit File(what, data);

}

// --- Savings Rate Accumulation external/internal function ---

function drip() public returns (uint256 nChi) {

(uint256 chi_, uint256 rho_) = (chi, rho);

uint256 diff;

if (block.timestamp > rho_) {

nChi = _rpow(ssr, block.timestamp - rho_) * chi_ / RAY;

uint256 totalSupply_ = totalSupply;

diff = totalSupply_ * nChi / RAY - totalSupply_ * chi_ / RAY;

vat.suck(address(vow), address(this), diff * RAY);

usdsJoin.exit(address(this), diff);

chi = uint192(nChi); // safe as nChi is limited to maxUint256/RAY (which is < maxUint192)

rho = uint64(block.timestamp);

} else {

nChi = chi_;

}

emit Drip(nChi, diff);

}

// --- ERC20 Mutations ---

function transfer(address to, uint256 value) external returns (bool) {

require(to != address(0) && to != address(this), "SUsds/invalid-address");

uint256 balance = balanceOf[msg.sender];

require(balance >= value, "SUsds/insufficient-balance");

unchecked {

balanceOf[msg.sender] = balance - value;

balanceOf[to] += value; // note: we don't need an overflow check here b/c sum of all balances == totalSupply

}

emit Transfer(msg.sender, to, value);

return true;

}

function transferFrom(address from, address to, uint256 value) external returns (bool) {

require(to != address(0) && to != address(this), "SUsds/invalid-address");

uint256 balance = balanceOf[from];

require(balance >= value, "SUsds/insufficient-balance");

if (from != msg.sender) {

uint256 allowed = allowance[from][msg.sender];

if (allowed != type(uint256).max) {

require(allowed >= value, "SUsds/insufficient-allowance");

unchecked {

allowance[from][msg.sender] = allowed - value;

}

unchecked {

balanceOf[from] = balance - value;

balanceOf[to] += value; // note: we don't need an overflow check here b/c sum of all balances == totalSupply

}

emit Transfer(from, to, value);

return true;

}

function approve(address spender, uint256 value) external returns (bool) {

allowance[msg.sender][spender] = value;

emit Approval(msg.sender, spender, value);

return true;

}

// --- Mint/Burn ---

// --- Mint/Burn Internal ---

function mint(address to, uint256 value) external auth {

require(to != address(0) && to != address(this), "SUsds/invalid-address");

function _mint(uint256 assets, uint256 shares, address receiver) internal {

require(receiver != address(0) && receiver != address(this), "SUsds/invalid-address");

usds.transferFrom(msg.sender, address(this), assets);

unchecked {

balanceOf[to] = balanceOf[to] + value; // note: we don't need an overflow check here b/c balanceOf[to] <= totalSupply and there is an overflow check below

balanceOf[receiver] = balanceOf[receiver] + shares; // note: we don't need an overflow check here b/c balanceOf[receiver] <= totalSupply

totalSupply = totalSupply + shares; // note: we don't need an overflow check here b/c shares totalSupply will always be <= usds totalSupply

}

totalSupply = totalSupply + value;

emit Transfer(address(0), to, value);

emit Deposit(msg.sender, receiver, assets, shares);

emit Transfer(address(0), receiver, shares);

}

function burn(address from, uint256 value) external {

function _burn(uint256 assets, uint256 shares, address receiver, address owner) internal {

uint256 balance = balanceOf[from];

uint256 balance = balanceOf[owner];

require(balance >= value, "SUsds/insufficient-balance");

require(balance >= shares, "SUsds/insufficient-balance");

if (from != msg.sender) {

if (owner != msg.sender) {

uint256 allowed = allowance[from][msg.sender];

uint256 allowed = allowance[owner][msg.sender];

if (allowed != type(uint256).max) {

require(allowed >= value, "SUsds/insufficient-allowance");

require(allowed >= shares, "SUsds/insufficient-allowance");

unchecked {

allowance[from][msg.sender] = allowed - value;

allowance[owner][msg.sender] = allowed - shares;

}

unchecked {

balanceOf[from] = balance - value; // note: we don't need overflow checks b/c require(balance >= value) and balance <= totalSupply

balanceOf[owner] = balance - shares; // note: we don't need overflow checks b/c require(balance >= shares) and balance <= totalSupply

totalSupply = totalSupply - value;

totalSupply = totalSupply - shares;

}

emit Transfer(from, address(0), value);

usds.transfer(receiver, assets);

emit Transfer(owner, address(0), shares);

emit Withdraw(msg.sender, receiver, owner, assets, shares);

}

// --- ERC-4626 ---

function asset() external view returns (address) {

return address(usds);

}

function totalAssets() external view returns (uint256) {

return convertToAssets(totalSupply);

}

function convertToShares(uint256 assets) public view returns (uint256) {

uint256 chi_ = (block.timestamp > rho) ? _rpow(ssr, block.timestamp - rho) * chi / RAY : chi;

return assets * RAY / chi_;

}

function convertToAssets(uint256 shares) public view returns (uint256) {

uint256 chi_ = (block.timestamp > rho) ? _rpow(ssr, block.timestamp - rho) * chi / RAY : chi;

return shares * chi_ / RAY;

}

function maxDeposit(address) external pure returns (uint256) {

return type(uint256).max;

}

function previewDeposit(uint256 assets) external view returns (uint256) {

return convertToShares(assets);

}

function deposit(uint256 assets, address receiver) public returns (uint256 shares) {

shares = assets * RAY / drip();

_mint(assets, shares, receiver);

}

function deposit(uint256 assets, address receiver, uint16 referral) external returns (uint256 shares) {

shares = deposit(assets, receiver);

emit Referral(referral, receiver, assets, shares);

}

function maxMint(address) external pure returns (uint256) {

return type(uint256).max;

}

function previewMint(uint256 shares) external view returns (uint256) {

uint256 chi_ = (block.timestamp > rho) ? _rpow(ssr, block.timestamp - rho) * chi / RAY : chi;

return _divup(shares * chi_, RAY);

}

function mint(uint256 shares, address receiver) public returns (uint256 assets) {

assets = _divup(shares * drip(), RAY);

_mint(assets, shares, receiver);

}

function mint(uint256 shares, address receiver, uint16 referral) external returns (uint256 assets) {

assets = mint(shares, receiver);

emit Referral(referral, receiver, assets, shares);

}

function maxWithdraw(address owner) external view returns (uint256) {

return convertToAssets(balanceOf[owner]);

}

function previewWithdraw(uint256 assets) external view returns (uint256) {

uint256 chi_ = (block.timestamp > rho) ? _rpow(ssr, block.timestamp - rho) * chi / RAY : chi;

return _divup(assets * RAY, chi_);

}

function withdraw(uint256 assets, address receiver, address owner) external returns (uint256 shares) {

shares = _divup(assets * RAY, drip());

_burn(assets, shares, receiver, owner);

}

function maxRedeem(address owner) external view returns (uint256) {

return balanceOf[owner];

}

function previewRedeem(uint256 shares) external view returns (uint256) {

return convertToAssets(shares);

}

function redeem(uint256 shares, address receiver, address owner) external returns (uint256 assets) {

assets = shares * drip() / RAY;

_burn(assets, shares, receiver, owner);

}

// --- Approve by signature ---

function _isValidSignature(

address signer,

bytes32 digest,

bytes memory signature

) internal view returns (bool valid) {

if (signature.length == 65) {

bytes32 r;

bytes32 s;

uint8 v;

assembly {

r := mload(add(signature, 0x20))

s := mload(add(signature, 0x40))

v := byte(0, mload(add(signature, 0x60)))

}

if (signer == ecrecover(digest, v, r, s)) {

return true;

}

if (signer.code.length > 0) {

(bool success, bytes memory result) = signer.staticcall(

abi.encodeCall(IERC1271.isValidSignature, (digest, signature))

);

valid = (success &&

result.length == 32 &&

abi.decode(result, (bytes4)) == IERC1271.isValidSignature.selector);

}

function permit(

address owner,

address spender,

uint256 value,

uint256 deadline,

bytes memory signature

) public {

require(block.timestamp <= deadline, "SUsds/permit-expired");

require(owner != address(0), "SUsds/invalid-owner");

uint256 nonce;

unchecked { nonce = nonces[owner]++; }

bytes32 digest =

keccak256(abi.encodePacked(

"\x19\x01",

_calculateDomainSeparator(block.chainid),

keccak256(abi.encode(

PERMIT_TYPEHASH,

owner,

spender,

value,

nonce,

deadline

))

));

require(_isValidSignature(owner, digest, signature), "SUsds/invalid-permit");

allowance[owner][spender] = value;

emit Approval(owner, spender, value);

}

function permit(

address owner,

address spender,

uint256 value,

uint256 deadline,

uint8 v,

bytes32 r,

bytes32 s

) external {

permit(owner, spender, value, deadline, abi.encodePacked(r, s, v));

}

已保存差異

原始文本

開啟檔案

// SPDX-License-Identifier: AGPL-3.0-or-later

/// SUsds.sol -- SUsds token

// Copyright (C) 2017, 2018, 2019 dbrock, rain, mrchico
// Copyright (C) 2024 Dai Foundation
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

pragma solidity ^0.8.21;

import "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";

interface IERC1271 {
    function isValidSignature(
        bytes32,
        bytes memory
    ) external view returns (bytes4);
}

contract SUsds is UUPSUpgradeable {
    mapping (address => uint256) public wards;

// --- ERC20 Data ---
    string  public constant name     = "Savings USDS";
    string  public constant symbol   = "sUSDS";
    string  public constant version  = "1";
    uint8   public constant decimals = 18;
    uint256 public totalSupply;

mapping (address => uint256)                      public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;
    mapping (address => uint256)                      public nonces;

// --- Events ---
    event Rely(address indexed usr);
    event Deny(address indexed usr);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event Transfer(address indexed from, address indexed to, uint256 value);

// --- EIP712 niceties ---
    bytes32 public constant PERMIT_TYPEHASH = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");

modifier auth {
        require(wards[msg.sender] == 1, "SUsds/not-authorized");
        _;
    }

constructor() {
        _disableInitializers(); // Avoid initializing in the context of the implementation
    }

// --- Upgradability ---

function initialize() initializer external {
        __UUPSUpgradeable_init();

wards[msg.sender] = 1;
        emit Rely(msg.sender);
    }

function _authorizeUpgrade(address newImplementation) internal override auth {}

function getImplementation() external view returns (address) {
        return ERC1967Utils.getImplementation();
    }

function _calculateDomainSeparator(uint256 chainId) private view returns (bytes32) {
        return keccak256(
            abi.encode(
                keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),
                keccak256(bytes(name)),
                keccak256(bytes(version)),
                chainId,
                address(this)
            )
        );
    }

function DOMAIN_SEPARATOR() external view returns (bytes32) {
        return _calculateDomainSeparator(block.chainid);
    }

// --- Administration ---
    function rely(address usr) external auth {
        wards[usr] = 1;
        emit Rely(usr);
    }

function deny(address usr) external auth {
        wards[usr] = 0;
        emit Deny(usr);
    }

// --- ERC20 Mutations ---
    function transfer(address to, uint256 value) external returns (bool) {
        require(to != address(0) && to != address(this), "SUsds/invalid-address");
        uint256 balance = balanceOf[msg.sender];
        require(balance >= value, "SUsds/insufficient-balance");

unchecked {
            balanceOf[msg.sender] = balance - value;
            balanceOf[to] += value; // note: we don't need an overflow check here b/c sum of all balances == totalSupply
        }

emit Transfer(msg.sender, to, value);

return true;
    }

function transferFrom(address from, address to, uint256 value) external returns (bool) {
        require(to != address(0) && to != address(this), "SUsds/invalid-address");
        uint256 balance = balanceOf[from];
        require(balance >= value, "SUsds/insufficient-balance");

if (from != msg.sender) {
            uint256 allowed = allowance[from][msg.sender];
            if (allowed != type(uint256).max) {
                require(allowed >= value, "SUsds/insufficient-allowance");

unchecked {
                    allowance[from][msg.sender] = allowed - value;
                }
            }
        }

unchecked {
            balanceOf[from] = balance - value;
            balanceOf[to] += value; // note: we don't need an overflow check here b/c sum of all balances == totalSupply
        }

emit Transfer(from, to, value);

return true;
    }

function approve(address spender, uint256 value) external returns (bool) {
        allowance[msg.sender][spender] = value;

emit Approval(msg.sender, spender, value);

return true;
    }

// --- Mint/Burn ---
    function mint(address to, uint256 value) external auth {
        require(to != address(0) && to != address(this), "SUsds/invalid-address");
        unchecked {
            balanceOf[to] = balanceOf[to] + value; // note: we don't need an overflow check here b/c balanceOf[to] <= totalSupply and there is an overflow check below
        }
        totalSupply = totalSupply + value;

emit Transfer(address(0), to, value);
    }

function burn(address from, uint256 value) external {
        uint256 balance = balanceOf[from];
        require(balance >= value, "SUsds/insufficient-balance");

unchecked {
                    allowance[from][msg.sender] = allowed - value;
                }
            }
        }

unchecked {
            balanceOf[from] = balance - value; // note: we don't need overflow checks b/c require(balance >= value) and balance <= totalSupply
            totalSupply     = totalSupply - value;
        }

emit Transfer(from, address(0), value);
    }

// --- Approve by signature ---
    function _isValidSignature(
        address signer,
        bytes32 digest,
        bytes memory signature
    ) internal view returns (bool valid) {
        if (signature.length == 65) {
            bytes32 r;
            bytes32 s;
            uint8 v;
            assembly {
                r := mload(add(signature, 0x20))
                s := mload(add(signature, 0x40))
                v := byte(0, mload(add(signature, 0x60)))
            }
            if (signer == ecrecover(digest, v, r, s)) {
                return true;
            }
        }

if (signer.code.length > 0) {
            (bool success, bytes memory result) = signer.staticcall(
                abi.encodeCall(IERC1271.isValidSignature, (digest, signature))
            );
            valid = (success &&
                result.length == 32 &&
                abi.decode(result, (bytes4)) == IERC1271.isValidSignature.selector);
        }
    }

function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        bytes memory signature
    ) public {
        require(block.timestamp <= deadline, "SUsds/permit-expired");
        require(owner != address(0), "SUsds/invalid-owner");

uint256 nonce;
        unchecked { nonce = nonces[owner]++; }

bytes32 digest =
            keccak256(abi.encodePacked(
                "\x19\x01",
                _calculateDomainSeparator(block.chainid),
                keccak256(abi.encode(
                    PERMIT_TYPEHASH,
                    owner,
                    spender,
                    value,
                    nonce,
                    deadline
                ))
            ));

require(_isValidSignature(owner, digest, signature), "SUsds/invalid-permit");

allowance[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external {
        permit(owner, spender, value, deadline, abi.encodePacked(r, s, v));
    }
}

更改後文本

開啟檔案

// SPDX-License-Identifier: AGPL-3.0-or-later

/// SUsds.sol

// Copyright (C) 2017, 2018, 2019 dbrock, rain, mrchico
// Copyright (C) 2021 Dai Foundation
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

pragma solidity ^0.8.21;

import "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";

interface IERC1271 {
    function isValidSignature(
        bytes32,
        bytes memory
    ) external view returns (bytes4);
}

interface VatLike {
    function hope(address) external;
    function suck(address, address, uint256) external;
}

interface UsdsJoinLike {
    function vat() external view returns (address);
    function usds() external view returns (address);
    function exit(address, uint256) external;
}

interface UsdsLike {
    function transfer(address, uint256) external;
    function transferFrom(address, address, uint256) external;
}

contract SUsds is UUPSUpgradeable {

// --- Storage Variables ---

// Admin
    mapping (address => uint256) public wards;
    // ERC20
    uint256                                           public totalSupply;
    mapping (address => uint256)                      public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;
    mapping (address => uint256)                      public nonces;
    // Savings yield
    uint192 public chi;   // The Rate Accumulator  [ray]
    uint64  public rho;   // Time of last drip     [unix epoch time]
    uint256 public ssr;   // The USDS Savings Rate [ray]

// --- Constants ---

// ERC20
    string  public constant name     = "Savings USDS";
    string  public constant symbol   = "sUSDS";
    string  public constant version  = "1";
    uint8   public constant decimals = 18;
    // Math
    uint256 private constant RAY = 10 ** 27;

// --- Immutables ---

// EIP712
    bytes32 public constant PERMIT_TYPEHASH = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    // Savings yield
    UsdsJoinLike public immutable usdsJoin;
    VatLike      public immutable vat;
    UsdsLike     public immutable usds;
    address      public immutable vow;

// --- Events ---

// Admin
    event Rely(address indexed usr);
    event Deny(address indexed usr);
    event File(bytes32 indexed what, uint256 data);
    // ERC20
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event Transfer(address indexed from, address indexed to, uint256 value);
    // ERC4626
    event Deposit(address indexed sender, address indexed owner, uint256 assets, uint256 shares);
    event Withdraw(address indexed sender, address indexed receiver, address indexed owner, uint256 assets, uint256 shares);
    // Referral
    event Referral(uint16 indexed referral, address indexed owner, uint256 assets, uint256 shares);
    // Savings yield
    event Drip(uint256 chi, uint256 diff);

// --- Modifiers ---

modifier auth {
        require(wards[msg.sender] == 1, "SUsds/not-authorized");
        _;
    }

// --- Constructor ---

constructor(address usdsJoin_, address vow_) {
        _disableInitializers(); // Avoid initializing in the context of the implementation

usdsJoin = UsdsJoinLike(usdsJoin_);
        vat = VatLike(UsdsJoinLike(usdsJoin_).vat());
        usds = UsdsLike(UsdsJoinLike(usdsJoin_).usds());
        vow = vow_;
    }

// --- Upgradability ---

function initialize() initializer external {
        __UUPSUpgradeable_init();

chi = uint192(RAY);
        rho = uint64(block.timestamp);
        ssr = RAY;
        vat.hope(address(usdsJoin));
        wards[msg.sender] = 1;
        emit Rely(msg.sender);
    }

function _authorizeUpgrade(address newImplementation) internal override auth {}

function getImplementation() external view returns (address) {
        return ERC1967Utils.getImplementation();
    }

// --- Internals ---

// EIP712

function DOMAIN_SEPARATOR() external view returns (bytes32) {
        return _calculateDomainSeparator(block.chainid);
    }

// Math

function _rpow(uint256 x, uint256 n) internal pure returns (uint256 z) {
        assembly {
            switch x case 0 {switch n case 0 {z := RAY} default {z := 0}}
            default {
                switch mod(n, 2) case 0 { z := RAY } default { z := x }
                let half := div(RAY, 2)  // for rounding.
                for { n := div(n, 2) } n { n := div(n,2) } {
                    let xx := mul(x, x)
                    if iszero(eq(div(xx, x), x)) { revert(0,0) }
                    let xxRound := add(xx, half)
                    if lt(xxRound, xx) { revert(0,0) }
                    x := div(xxRound, RAY)
                    if mod(n,2) {
                        let zx := mul(z, x)
                        if and(iszero(iszero(x)), iszero(eq(div(zx, x), z))) { revert(0,0) }
                        let zxRound := add(zx, half)
                        if lt(zxRound, zx) { revert(0,0) }
                        z := div(zxRound, RAY)
                    }
                }
            }
        }
    }

function _divup(uint256 x, uint256 y) internal pure returns (uint256 z) {
        // Note: _divup(0,0) will return 0 differing from natural solidity division
        unchecked {
            z = x != 0 ? ((x - 1) / y) + 1 : 0;
        }
    }

// --- Admin external functions ---

function rely(address usr) external auth {
        wards[usr] = 1;
        emit Rely(usr);
    }

function deny(address usr) external auth {
        wards[usr] = 0;
        emit Deny(usr);
    }

function file(bytes32 what, uint256 data) external auth {
        if (what == "ssr") {
            require(data >= RAY, "SUsds/wrong-ssr-value");
            require(rho == block.timestamp, "SUsds/chi-not-up-to-date");
            ssr = data;
        } else revert("SUsds/file-unrecognized-param");
        emit File(what, data);
    }

// --- Savings Rate Accumulation external/internal function ---

// --- ERC20 Mutations ---

function transfer(address to, uint256 value) external returns (bool) {
        require(to != address(0) && to != address(this), "SUsds/invalid-address");
        uint256 balance = balanceOf[msg.sender];
        require(balance >= value, "SUsds/insufficient-balance");

unchecked {
            balanceOf[msg.sender] = balance - value;
            balanceOf[to] += value; // note: we don't need an overflow check here b/c sum of all balances == totalSupply
        }

emit Transfer(msg.sender, to, value);

return true;
    }

unchecked {
                    allowance[from][msg.sender] = allowed - value;
                }
            }
        }

unchecked {
            balanceOf[from] = balance - value;
            balanceOf[to] += value; // note: we don't need an overflow check here b/c sum of all balances == totalSupply
        }

emit Transfer(from, to, value);

return true;
    }

function approve(address spender, uint256 value) external returns (bool) {
        allowance[msg.sender][spender] = value;

emit Approval(msg.sender, spender, value);

return true;
    }

// --- Mint/Burn Internal ---

function _mint(uint256 assets, uint256 shares, address receiver) internal {
        require(receiver != address(0) && receiver != address(this), "SUsds/invalid-address");

usds.transferFrom(msg.sender, address(this), assets);

unchecked {
            balanceOf[receiver] = balanceOf[receiver] + shares; // note: we don't need an overflow check here b/c balanceOf[receiver] <= totalSupply
            totalSupply = totalSupply + shares; // note: we don't need an overflow check here b/c shares totalSupply will always be <= usds totalSupply
        }

emit Deposit(msg.sender, receiver, assets, shares);
        emit Transfer(address(0), receiver, shares);
    }

function _burn(uint256 assets, uint256 shares, address receiver, address owner) internal {
        uint256 balance = balanceOf[owner];
        require(balance >= shares, "SUsds/insufficient-balance");

if (owner != msg.sender) {
            uint256 allowed = allowance[owner][msg.sender];
            if (allowed != type(uint256).max) {
                require(allowed >= shares, "SUsds/insufficient-allowance");

unchecked {
                    allowance[owner][msg.sender] = allowed - shares;
                }
            }
        }

unchecked {
            balanceOf[owner] = balance - shares; // note: we don't need overflow checks b/c require(balance >= shares) and balance <= totalSupply
            totalSupply      = totalSupply - shares;
        }

usds.transfer(receiver, assets);

emit Transfer(owner, address(0), shares);
        emit Withdraw(msg.sender, receiver, owner, assets, shares);
    }

// --- ERC-4626 ---

function asset() external view returns (address) {
        return address(usds);
    }

function totalAssets() external view returns (uint256) {
        return convertToAssets(totalSupply);
    }

function convertToShares(uint256 assets) public view returns (uint256) {
        uint256 chi_ = (block.timestamp > rho) ? _rpow(ssr, block.timestamp - rho) * chi / RAY : chi;
        return assets * RAY / chi_;
    }

function convertToAssets(uint256 shares) public view returns (uint256) {
        uint256 chi_ = (block.timestamp > rho) ? _rpow(ssr, block.timestamp - rho) * chi / RAY : chi;
        return shares * chi_ / RAY;
    }

function maxDeposit(address) external pure returns (uint256) {
        return type(uint256).max;
    }

function previewDeposit(uint256 assets) external view returns (uint256) {
        return convertToShares(assets);
    }

function deposit(uint256 assets, address receiver) public returns (uint256 shares) {
        shares = assets * RAY / drip();
        _mint(assets, shares, receiver);
    }

function deposit(uint256 assets, address receiver, uint16 referral) external returns (uint256 shares) {
        shares = deposit(assets, receiver);
        emit Referral(referral, receiver, assets, shares);
    }

function maxMint(address) external pure returns (uint256) {
        return type(uint256).max;
    }

function previewMint(uint256 shares) external view returns (uint256) {
        uint256 chi_ = (block.timestamp > rho) ? _rpow(ssr, block.timestamp - rho) * chi / RAY : chi;
        return _divup(shares * chi_, RAY);
    }

function mint(uint256 shares, address receiver) public returns (uint256 assets) {
        assets = _divup(shares * drip(), RAY);
        _mint(assets, shares, receiver);
    }

function mint(uint256 shares, address receiver, uint16 referral) external returns (uint256 assets) {
        assets = mint(shares, receiver);
        emit Referral(referral, receiver, assets, shares);
    }

function maxWithdraw(address owner) external view returns (uint256) {
        return convertToAssets(balanceOf[owner]);
    }

function previewWithdraw(uint256 assets) external view returns (uint256) {
        uint256 chi_ = (block.timestamp > rho) ? _rpow(ssr, block.timestamp - rho) * chi / RAY : chi;
        return _divup(assets * RAY, chi_);
    }

function withdraw(uint256 assets, address receiver, address owner) external returns (uint256 shares) {
        shares = _divup(assets * RAY, drip());
        _burn(assets, shares, receiver, owner);
    }

function maxRedeem(address owner) external view returns (uint256) {
        return balanceOf[owner];
    }

function previewRedeem(uint256 shares) external view returns (uint256) {
        return convertToAssets(shares);
    }

function redeem(uint256 shares, address receiver, address owner) external returns (uint256 assets) {
        assets = shares * drip() / RAY;
        _burn(assets, shares, receiver, owner);
    }

// --- Approve by signature ---

uint256 nonce;
        unchecked { nonce = nonces[owner]++; }

require(_isValidSignature(owner, digest, signature), "SUsds/invalid-permit");

allowance[owner][spender] = value;
        emit Approval(owner, spender, value);
    }