BSwap Contract Reference

The BSwap contract implements Baseline's power-law AMM curve for token trading. It handles all buy and sell operations, applying the n=2 curve with BLV translation.

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Contract: BSwap.sol Version: 21 License: AGPL-3.0-or-later

Overview

BSwap provides four trading entry points (exact input/output for buys and sells) and corresponding quote functions. All trades execute through the power-law curve:

y_buffer = K × (x/c)²

Functions

Trading Functions

buyTokensExactIn

Buy bTokens with an exact amount of reserves.

function buyTokensExactIn(
  BToken _bToken,
  uint256 _amountIn,
  uint256 _limitAmount
) external returns (uint256 amountOut_, uint256 feesReceived_)

Parameter	Type	Description
`_bToken`	`BToken`	The bToken to buy
`_amountIn`	`uint256`	Exact reserve amount to spend
`_limitAmount`	`uint256`	Minimum bTokens to receive (slippage protection)

Returns:

amountOut_: bTokens received
feesReceived_: Fees collected

Errors:

SlippageExceeded: If amountOut_ < _limitAmount

buyTokensExactOut

Buy an exact amount of bTokens.

function buyTokensExactOut(
  BToken _bToken,
  uint256 _amountOut,
  uint256 _limitAmount
) external returns (uint256 amountIn_, uint256 feesReceived_)

Parameter	Type	Description
`_bToken`	`BToken`	The bToken to buy
`_amountOut`	`uint256`	Exact bTokens to receive
`_limitAmount`	`uint256`	Maximum reserves to spend (slippage protection)

sellTokensExactIn

Sell an exact amount of bTokens.

function sellTokensExactIn(
  BToken _bToken,
  uint256 _amountIn,
  uint256 _limitAmount
) external returns (uint256 amountOut_, uint256 feesReceived_)

Parameter	Type	Description
`_bToken`	`BToken`	The bToken to sell
`_amountIn`	`uint256`	Exact bTokens to sell
`_limitAmount`	`uint256`	Minimum reserves to receive (slippage protection)

sellTokensExactOut

Sell bTokens to receive an exact amount of reserves.

function sellTokensExactOut(
  BToken _bToken,
  uint256 _amountOut,
  uint256 _limitAmount
) external returns (uint256 amountIn_, uint256 feesReceived_)

Parameter	Type	Description
`_bToken`	`BToken`	The bToken to sell
`_amountOut`	`uint256`	Exact reserves to receive
`_limitAmount`	`uint256`	Maximum bTokens to sell (slippage protection)

Quote Functions

Quote functions return expected trade results without executing.

quoteBuyExactIn

function quoteBuyExactIn(BToken _bToken, uint256 _amountIn) 
  external view returns (uint256 amountOut_, uint256 fee_)

quoteBuyExactOut

function quoteBuyExactOut(BToken _bToken, uint256 _amountOut) 
  external view returns (uint256 amountIn_, uint256 fee_)

quoteSellExactIn

function quoteSellExactIn(BToken _bToken, uint256 _amountIn) 
  external view returns (uint256 amountOut_, uint256 fee_)

quoteSellExactOut

function quoteSellExactOut(BToken _bToken, uint256 _amountOut) 
  external view returns (uint256 amountIn_, uint256 fee_)

View Functions

getCurveParams

Get current curve parameters for a bToken.

function getCurveParams(BToken _bToken) external view returns (CurveParams memory)

Returns: CurveParams struct containing:

k: Curve invariant
blv: Current BLV (floor price)
swapFeePct: Fee percentage

Errors

Error	Description
`SlippageExceeded`	Trade output doesn't meet limit
`SolverFailed`	Numerical solver failed to converge
`AmountExceedsLiquidity`	Requested amount exceeds available liquidity

Events

event Swap(
  BToken bToken,
  address sender,
  bool isBuy,
  uint256 amountIn,
  uint256 amountOut,
  uint256 fee
);

Usage Example

// Buy 100 bTokens, paying at most 110 ETH
uint256 amountIn;
uint256 fees;
(amountIn, fees) = bswap.buyTokensExactOut(
  bToken,
  100e18,   // 100 tokens
  110e18    // max 110 reserves
);
 
// Get quote first
(uint256 quotedOut, uint256 quotedFee) = bswap.quoteBuyExactIn(
  bToken,
  100e18    // 100 reserves
);

BMM Mechanics: Power-law curve explanation
BLens Contract : View functions

Deployments BStaking