Single Swap

Function and Struct Definitions

Swap function

swap(SingleSwap singleSwap,
     FundManagement funds,
     uint256 limit,
     uint256 deadline) returns (uint256 amountCalculated[In/Out])
  • singleSwap: A definition of the swap to be executed, defined below
  • funds: A definition of where funds are going to/from, defined below
  • limit: The meaning of limit depends on the value of singleSwap.kind
    • GIVEN_IN: The minimum amount of tokens to receive from the swap.
    • GIVEN_OUT: The maximum amount of tokens to send for the swap.
  • deadline: The UNIX timestamp at which our swap must be completed by - if the transaction is confirmed after this time then the transaction will fail.

SingleSwap struct

The SingleSwap struct is defined as below.

enum SwapKind { GIVEN_IN, GIVEN_OUT }

struct SingleSwap {
   bytes32 poolId;
   SwapKind kind;
   IAsset assetIn;
   IAsset assetOut;
   uint256 amount;
   bytes userData;
  • poolId: The id of the pool to swap with.
  • kind: The type of swap to perform - either "Out Given Exact In" or "In Given Exact Out."
  • assetIn: The address of the token to swap into the pool.
  • assetOut: The address of the token to receive in return.
  • amount: The meaning of amount depends on the value of kind.
    • GIVEN_IN: The amount of tokens being sent
    • GIVEN_OUT: The amount of tokens being received
  • userData: Any additional data which the pool requires to perform the swap. This allows pools to have more flexible swapping logic in future - for all current Balancer pools this can be left empty.

FundManagement struct

The FundManagement struct defines where the input tokens for the swap are coming from and where the output tokens should be sent. The FundManagement struct is defined as below.

struct FundManagement {
    address sender;
    bool fromInternalBalance;
    address payable recipient;
    bool toInternalBalance;
  • sender: The address from which tokens will be taken to perform the swap.
  • fromInternalBalance: Whether the swap should use tokens owned by the sender which are already stored in the Vault.
  • recipient: The address to which tokens will be sent to after the swap.
  • toInternalBalance: Whether the tokens should be sent to the recipient or stored within their internal balance within the Vault.