v4版本相较于v3,主要引入了4个功能:
1.Hooks
在uniswapv4中,每个流动池不再对应一个合约，而是所有池子都在一个合约下(PoolKey作为Pool的唯一ID),以下是官方给出创建流动池的例子
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;
import {IPoolManager} from "v4-core/src/interfaces/IPoolManager.sol";
import {IHooks} from "v4-core/src/interfaces/IHooks.sol";
import {PoolKey} from "v4-core/src/types/PoolKey.sol";
import {CurrencyLibrary, Currency} from "v4-core/src/types/Currency.sol";
contract PoolInitialize {
using CurrencyLibrary for Currency;
// set the initialize router
IPoolManager manager = IPoolManager(address(0x01));
function init(
address token0,
address token1,
uint24 swapFee,
int24 tickSpacing,
address hook,
uint160 sqrtPriceX96,
bytes calldata hookData
) external {
// sort your tokens! v4 requires token0 < token1
if (token0 > token1) {
(token0, token1) = (token1, token0);
}
PoolKey memory pool = PoolKey({
currency0: Currency.wrap(token0),
currency1: Currency.wrap(token1),
fee: swapFee,
tickSpacing: tickSpacing,
hooks: IHooks(hook)
});
manager.initialize(pool, sqrtPriceX96, hookData);
}
}
可见即使token,swapFee等相同,但是如果hook的address不同，也会被看成不同的流动池.
hook也许是uniswapv4中最重要的内容(在javascript中,hook作为拦截和修改func,使开发者可以拓展代码而不需要修改原始代码),在uniswapv4中,hook的作用也差不多.
在v4中,hooks可以发挥5个主要功能:
1.beforeInitialize/afterInitialize
2.beforeAddLiquidity/afterAddLiquidity
3.beforeRemoveLiquidity/afterRemoveLiquidity
4.beforeSwap/afterSwap
5.beforeDonate/afterDonate
v4中允许hook在特定操作(如上面功能名称)前后进行调用,从而实现特定操作,同时,hook可以在swap中收取费用，可以静态也可以动态管理.也可以进行特定比例分配给任意地址.
下图是官方白皮书中hook的工作流程,描述了beforeSwap和afterSwap中hook是如何工作的.
官方给出的hook示例:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;
import {BaseHook} from "v4-periphery/src/base/hooks/BaseHook.sol";
import {PoolKey} from "v4-core/types/PoolKey.sol";
import {IPoolManager} from "v4-core/interfaces/IPoolManager.sol";
import {Hooks} from "v4-core/libraries/Hooks.sol";
contract SampleHook is BaseHook {
constructor(IPoolManager _manager, string memory _name, string memory _symbol) BaseHook(_manager){
// do something
}
function getHookPermissions() public pure override returns (Hooks.Permissions memory) {
return Hooks.Permissions({
beforeInitialize: false,
afterInitialize: false,
beforeAddLiquidity: true,
beforeRemoveLiquidity: false,
afterAddLiquidity: true,
afterRemoveLiquidity: false,
beforeSwap: false,
afterSwap: false,
beforeDonate: false,
afterDonate: false,
beforeSwapReturnDelta: false,
afterSwapReturnDelta: false,
afterAddLiquidityReturnDelta: false,
afterRemoveLiquidityReturnDelta: false
});
}
function beforeAddLiquidity(
address sender,
PoolKey calldata key,
IPoolManager.ModifyLiquidityParams calldata params,
bytes override calldata hookData
) external returns (bytes4){
// do something
}
function afterAddLiquidity(
address sender,
PoolKey calldata key,
IPoolManager.ModifyLiquidityParams calldata params,
BalanceDelta delta,
bytes calldata hookData
) external override returns (bytes4, BalanceDelta); {
// do something
}
}
可以看到，hook作为一个合约，继承于BaseHook,
在构造一个hook中,必须包含 IPoolManager参数，其为管理接口,同时也有如 onlyByPoolManager修饰符,作为管理员权限func.
getHookPermissionfunc必须重载,可以实现上面所说的五个功能，把对应的功能(如beforeAddLiquidity)设置为true即可.
2.Singleton
先前的Uniswap版本使用factor/pool模式进行代币部署,Uniswapv4使用singleton设计模式,所有资金池由一个合约管理,使池子到部署成本降低99%.
同时singleton与flash accounting互补,v4中，每个操作(如兑换或向池中添加流动性),只更新一个内部净余额delta,仅在锁定结束时进行外部转账.新的take()和settle()分别借入或存入.
By requiring that no tokens are owed to the pool manager or to the caller by the end of the call, the pool’s solvency is enforced.
3.Flash accounting
两者加上hook，可以增加pool的数量
4.Native ETH
5.Custom Accounting
Hooks without Custom Accounting:
大多数流程中(如beforeswap)会造成revert;
potential attack:
removing liquidity: beforeSwap
sandwich attack: beforeSwap+afterSwap and before donate+after donate
permanently lock: before removeLiquidity, after removeLiquidity