MakerDAO-Join
MakerDAO Join 合约分析
// SPDX-License-Identifier: AGPL-3.0-or-later
/// join.sol -- Basic token adapters 基本 Token 适配器
// Copyright (C) 2018 Rain <rainbreak@riseup.net>
//
// 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 ^0.6.12;
// FIXME: This contract was altered compared to the production version.
// It doesn't use LibNote anymore.
// New deployments of this contract will need to include custom events (TO DO).
interface GemLike {
function decimals() external view returns (uint256);
function transfer(address, uint256) external returns (bool);
function transferFrom(address, address, uint256) external returns (bool);
}
interface DSTokenLike {
function mint(address, uint256) external;
function burn(address, uint256) external;
}
interface VatLike {
function slip(bytes32, address, int256) external;
function move(address, address, uint256) external;
}
/*
Here we provide *adapters* to connect the Vat to arbitrary external
token implementations, creating a bounded context for the Vat. The
adapters here are provided as working examples:
- `GemJoin`: For well behaved ERC20 tokens, with simple transfer
semantics.
- `ETHJoin`: For native Ether.
- `DaiJoin`: For connecting internal Dai balances to an external
`DSToken` implementation.
In practice, adapter implementations will be varied and specific to
individual collateral types, accounting for different transfer
semantics and token standards.
Adapters need to implement two basic methods:
- `join`: enter collateral into the system
- `exit`: remove collateral from the system
*/
/**
* @title
* @author
* @notice
* - 当用户想要将抵押品存入/取出系统(`Vat`)时,与该合约交互
* - 每一种 ERC20 Token 对应一个 Gemjoin 合约
*/
contract GemJoin {
// --- Auth ---
mapping(address => uint256) public wards;
function rely(address usr) external auth {
wards[usr] = 1;
emit Rely(usr);
}
function deny(address usr) external auth {
wards[usr] = 0;
emit Deny(usr);
}
modifier auth() {
require(wards[msg.sender] == 1, "GemJoin/not-authorized");
_;
}
VatLike public vat; // CDP Engine
bytes32 public ilk; // Collateral Type
GemLike public gem;
uint256 public dec;
uint256 public live; // Active Flag
// Events
event Rely(address indexed usr);
event Deny(address indexed usr);
event Join(address indexed usr, uint256 wad);
event Exit(address indexed usr, uint256 wad);
event Cage();
constructor(address vat_, bytes32 ilk_, address gem_) public {
wards[msg.sender] = 1;
live = 1;
vat = VatLike(vat_);
ilk = ilk_;
gem = GemLike(gem_);
dec = gem.decimals();
emit Rely(msg.sender);
}
/**
* @notice
* - 修改 GemJoin 合约的状态,适配器排空(不允许 `join`,但是允许 `exit`)
* - `join` 受限:防止在系统非活跃状态下增加新的抵押品,从而避免系统风险增加。
* - `exit` 不受限:用户可以在任何时候取回他们的抵押品,确保用户资产的自由流动。
*/
function cage() external auth {
live = 0;
emit Cage();
}
/**
* @notice 将用户的 ERC-20 代币存入系统(消耗 `msg.sender` 的 Token,增加 `usr` 的抵押品数量)
* @param usr 存入抵押品的地址(若为 `msg.sender` 自己,则 `usr = msg.sender`
* @param wad 存入的代币数量,单位 wad (10^18)
* @notice
* - 此函数用于将用户的 ERC-20 代币存入 MakerDAO 系统,并记录到 `Vat` 合约中
* - 用户存入代币时需要确保系统处于活跃状态(`live == 1`),并且代币数量非负(`int256(wad) >= 0`)
* - 成功存入代币后,触发 `Join` 事件
* - `msg.sender` -> `vat[usr]` (`msg.sender`把抵押品存入合约,视为 `usr` 的抵押品)
*/
function join(address usr, uint256 wad) external {
require(live == 1, "GemJoin/not-live");
require(int256(wad) >= 0, "GemJoin/overflow");
vat.slip(ilk, usr, int256(wad));
require(gem.transferFrom(msg.sender, address(this), wad), "GemJoin/failed-transfer");
emit Join(usr, wad);
}
/**
* 从系统中取出用户的 ERC-20 代币(减少 `msg.sender` 的 `vat` 余额,发送给 `usr`)
* @param usr 接收取出代币的用户地址(若为 `msg.sender` 自己,则 `usr = msg.sender`
* @param wad 取出的代币数量,单位为 wad (10^18)
* @notice
* - 此函数用于将用户的 ERC-20 代币从 MakerDAO 系统中取出,并将其发送到指定的用户地址。
* - 用户在取出代币时需要确保数量不超过 2^255,并且转账操作成功
* - 成功取出代币后,触发 `Exit` 事件
* - `vat[msg.sender]` -> `usr` (`msg.sender`在 vat 中的抵押品取出,取出给 `usr`)
*/
function exit(address usr, uint256 wad) external {
require(wad <= 2 ** 255, "GemJoin/overflow");
vat.slip(ilk, msg.sender, -int256(wad));
require(gem.transfer(usr, wad), "GemJoin/failed-transfer");
emit Exit(usr, wad);
}
}
/**
* @notice
* - 当用户想将 Dai 存入/取出 系统(`Vat`)时与该合约交互
*/
contract DaiJoin {
// --- Auth ---
mapping(address => uint256) public wards;
function rely(address usr) external auth {
wards[usr] = 1;
emit Rely(usr);
}
function deny(address usr) external auth {
wards[usr] = 0;
emit Deny(usr);
}
modifier auth() {
require(wards[msg.sender] == 1, "DaiJoin/not-authorized");
_;
}
VatLike public vat; // CDP Engine
DSTokenLike public dai; // Stablecoin Token
uint256 public live; // Active Flag
// Events
event Rely(address indexed usr);
event Deny(address indexed usr);
event Join(address indexed usr, uint256 wad);
event Exit(address indexed usr, uint256 wad);
event Cage();
constructor(address vat_, address dai_) public {
wards[msg.sender] = 1;
live = 1;
vat = VatLike(vat_);
dai = DSTokenLike(dai_);
}
/**
* @notice
* - 修改 DaiJoin 合约的状态,适配器排空(允许 `join`,不允许`exit`)
* - `join` 不受限:Dai 的存入不会直接影响系统的稳定性,因此不受限制。
* - `exit` 受限:防止在系统非活跃状态下生成新的 Dai,确保系统的稳定性和一致性。
*/
function cage() external auth {
live = 0;
emit Cage();
}
uint256 constant ONE = 10 ** 27;
function mul(uint256 x, uint256 y) internal pure returns (uint256 z) {
require(y == 0 || (z = x * y) / y == x);
}
/**
* 将用户的 Dai 存入 Vat(减少 `msg.sender` 的 Dai,增加 `usr` 的 Dai 余额)
* @param usr 存入 Dai 的账户(若为自己,则 `usr = msg.sender`)
* @param wad 存入的 Dai 数量,单位为 wad (10^18)
*
* @notice
* - 此函数将 `msg.sender` 的 Dai 转移到 Vat 中,并增加 `usr` 的 Dai 余额。
* - `vat.move` 函数用于在 `Vat` 合约中移动 Dai 余额。
* - `dai.burn` 函数销毁 `msg.sender` 的 Dai。
* - 调用成功后,触发 `Join` 事件。
*
* @dev
* `Vat` 合约中的 Dai 不是以 ERC-20 代币的形式存在,而是作为系统内部的记账单位 `rad` (rad = 10^45)
* 所以将 Dai 存入 `Vat` 后,需要 `burn` `msg.sender` 相应数量的 Dai。
*/
function join(address usr, uint256 wad) external {
// vat.move(from, to, amount) amount 单位 [rad = 10^45] 10^27 * 10^18 = 10^45
// rad [rad = 10^45] ONE * wad = 10^18 * 10^27 = 10^45 == rad
// 增加 usr 在 Vat 合约中的 Dai 余额,减少 DaiJoin 合约在 Vat 中的 Dai 余额。
vat.move(address(this), usr, mul(ONE, wad));
// 从系统中实际销毁 msg.sender 的 Dai 代币,减少系统中的 Dai 供应。
// dai.burn(usr, wad)
dai.burn(msg.sender, wad);
emit Join(usr, wad);
}
/**
* 从系统中取出 Dai
* @param usr 接受 Dai 的地址(若为 `msg.sender` 自身,则 `usr = msg.sender`)
* @param wad 取出的 Dai 的数量
* @notice
* - 此函数将 `msg.sender` 存在系统`Vat`中的 Dai 取出,接收方为 `usr`
* - 因为 `Vat` 合约中的 Dai 不是以 ERC-20 代币的形式存在,所以取出 Dai
* 实际上是 `mint` 了新的 Dai,同时减少了 `Vat` 中 `msg.sender` 的数量
*/
function exit(address usr, uint256 wad) external {
require(live == 1, "DaiJoin/not-live");
// vat.move(from, to, amount) amount 单位 [rad = 10^45] 10^27 * 10^18 = 10^45
// rad [rad = 10^45] ONE * wad = 10^18 * 10^27 = 10^45 == rad
vat.move(msg.sender, address(this), mul(ONE, wad));
dai.mint(usr, wad);
emit Exit(usr, wad);
}
}
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