Filling EVM Orders

The delivery of assets depends on the Output Settlement Interface associated with an order. The Output Settlement Interface can be read from the order: orderDto.order.remoteFiller.

BaseFiller-based (CoinFiller)

The CoinFiller is the simplest Output Settlement implementation and allows specifying limit orders and Dutch auctions.

Caution

Support for Dutch auctions is not yet provided.

To fill an output using Output Settlements based on BaseFiller, use the associated fill interfaces:

function fill(bytes32 orderId, OutputDescription calldata output, bytes32 proposedSolver) external returns (bytes32) {
  return _fill(orderId, output, proposedSolver);
}

function fillThrow(bytes32[] calldata orderIds, OutputDescription[] calldata outputs, bytes32 filler) external {
  _fillThrow(orderIds, outputs, filler);
}

function fillSkip(bytes32[] calldata orderIds, OutputDescription[] calldata outputs, bytes32 filler) external {
    _fillSkip(orderIds, outputs, filler);
}

Filling a single output description is most efficient with fill(...) since it does not contain a loop. However, it is limited to a single output at a time.

For batch filling, fillThrow or fillSkip may be better:

• fillThrow fills all outputs, but if one has already been filled by another solver, the entire call will revert. Use it when an output has multiple outputs and you are filling all outputs of an order or none.

• fillSkip fills all outputs, but if some have already been filled, those will be skipped silently. Use it when you are batch filling multiple orders. This allows you to claim as many outputs as possible in one go, even if one order has been filled by another solver.

Validation Layers

Once orders have been filled on the output settlement contract, they need to be submitted to the validation layer to be ferried to the input chain. The first step is to generate the associated payload. The reference payload encoding format is:

Encoded FillDescription
     SOLVER                          0               (32 bytes)
     + ORDERID                       32              (32 bytes)
     + TIMESTAMP                     64              (4 bytes)
     + TOKEN                         68              (32 bytes)
     + AMOUNT                        100             (32 bytes)
     + RECIPIENT                     132             (32 bytes)
     + REMOTE_CALL_LENGTH            164             (2 bytes)
     + REMOTE_CALL                   166             (LENGTH bytes)
     + FULFILLMENT_CONTEXT_LENGTH    166+RC_LENGTH   (2 bytes)
     + FULFILLMENT_CONTEXT           168+RC_LENGTH   (LENGTH bytes)

It may be beneficial to batch multiple proven outputs to the validation layer.

Simple Broadcast Interfaces (Wormhole)

For messaging protocols supporting simple broadcast interfaces like Wormhole, the following interface is used:

function submit(address proofSource, bytes[] calldata payloads) public payable returns (uint256 refund);

Where proofSource = orderDto.order.remoteFiller and payloads is the encoded OutputDescriptions.