CarryStrategy

A trading tax hook. It takes a cut of every trade, keeps rewards to claim and stops liquidity being added or removed directly.

• Takes a cut of every trade

  On top of the normal pool fee, it keeps a share of each trade. The fee can be changed. The fee builds up in the hook until it is collected.

  The code that does this (beforeSwap):

  function beforeSwap(address sender, PoolKey calldata key, SwapParams calldata params, bytes calldata)
      external
      returns (bytes4, BeforeSwapDelta, uint24)
  {
      if (msg.sender != address(poolManager)) revert OnlyPoolManager();
      _enter();
      PoolId id = key.toId();
      Pool storage p = pools[id];
      if (!p.exists) revert UnknownPool();
      if (!p.live) revert NotLive();
      if (params.amountSpecified == 0 || params.amountSpecified == type(int256).min) revert BadParams();
  
      (uint256 kb, uint256 ks, uint256 pb, uint256 ps) = _prepareSame(p);
  
      bool exactIn = params.amountSpecified < 0;
      uint256 spec = exactIn ? uint256(-params.amountSpecified) : uint256(params.amountSpecified);
      // input is currency0 when zeroForOne; the input is the coin on a sell
      bool sell = params.zeroForOne == p.coinIs0;
      (uint256 coinAmt, uint256 quoteAmt) =
          _fill(p.book.x, p.book.y, p.tX128, sell ? ks : kb, sell ? ps : pb, sell, exactIn, spec);
      if (sell) p.book.swap(int256(coinAmt), -int256(quoteAmt));
      else p.book.swap(-int256(coinAmt), int256(quoteAmt));
  
      Currency coinC = Currency.wrap(p.coin);
      Currency quoteC = Currency.wrap(p.quote);
      Currency inC = sell ? coinC : quoteC;
      Currency outC = sell ? quoteC : coinC;
      uint256 inAmt = sell ? coinAmt : quoteAmt;
      uint256 outAmt = sell ? quoteAmt : coinAmt;
      // claims only: the PoolManager need not hold the input token yet (the swapper pays after the hook runs)
      // …

• Rewards to claim

  It keeps track of what people have earned, and they claim it themselves.

  The code that does this (claim):

  function claim(PoolId id, uint256 lot) external lock returns (uint256 x, uint256 y) {
      Pool storage p = _live(id);
      _markLoss(p);
      (x, y) = BK.claim(p.book, lot, msg.sender);
      _moves(id, _pair(p, x, y, msg.sender, false));
      emit Claimed(id, msg.sender, x, y);
  }

• Liquidity can’t be added or removed directly

  Nobody can add or remove liquidity through Uniswap directly. Liquidity only moves through the hook’s own code.

• Only approved callers create pools

  New pools with this hook can only be created by approved callers, for example its own factory or launcher.

  The code that does this (beforeInitialize):

  function beforeInitialize(address, PoolKey calldata, uint160) external view returns (bytes4) {
      if (msg.sender != address(poolManager)) revert OnlyPoolManager();
      revert ExternalInit();
  }

• No trading before the start

  Trades are refused until trading has been opened.

  The code that does this (beforeSwap):

  function beforeSwap(address sender, PoolKey calldata key, SwapParams calldata params, bytes calldata)
      external
      returns (bytes4, BeforeSwapDelta, uint24)
  {
      if (msg.sender != address(poolManager)) revert OnlyPoolManager();
      _enter();
      PoolId id = key.toId();
      Pool storage p = pools[id];
      if (!p.exists) revert UnknownPool();
      if (!p.live) revert NotLive();
      if (params.amountSpecified == 0 || params.amountSpecified == type(int256).min) revert BadParams();
  
      (uint256 kb, uint256 ks, uint256 pb, uint256 ps) = _prepareSame(p);
  
      bool exactIn = params.amountSpecified < 0;
      uint256 spec = exactIn ? uint256(-params.amountSpecified) : uint256(params.amountSpecified);
      // input is currency0 when zeroForOne; the input is the coin on a sell
      bool sell = params.zeroForOne == p.coinIs0;
      (uint256 coinAmt, uint256 quoteAmt) =
          _fill(p.book.x, p.book.y, p.tX128, sell ? ks : kb, sell ? ps : pb, sell, exactIn, spec);
      if (sell) p.book.swap(int256(coinAmt), -int256(quoteAmt));
      else p.book.swap(-int256(coinAmt), int256(quoteAmt));
  
      Currency coinC = Currency.wrap(p.coin);
      Currency quoteC = Currency.wrap(p.quote);
      Currency inC = sell ? coinC : quoteC;
      Currency outC = sell ? quoteC : coinC;
      uint256 inAmt = sell ? coinAmt : quoteAmt;
      uint256 outAmt = sell ? quoteAmt : coinAmt;
      // claims only: the PoolManager need not hold the input token yet (the swapper pays after the hook runs)
      // …

• Anyone can trigger payouts

  Anyone can send the collected fees on to where they go, so nobody has to wait on the hook developer.

  The code that does this (sweep):

  function sweep(PoolId id) external lock {
      _live(id);
      poolManager.unlock(abi.encode(OP_SWEEP, id, address(0), uint16(0), new Move[](0)));
  }

Who controls it: The hook developer can change the fee and the trading limits. The hook developer can also change: leader, tip rule, depth rule, tail, carry. The hook developer can also call: propose admin, accept admin. The pool creator can change: creator. The code cannot be changed.

Based on the hook’s published code.What do these labels mean?