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Documentation Index

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Overview

Fills an order with the caller (msg.sender) as the taker. This function allows an operator to execute a single order for a specified fill amount. 
function fillOrder(Order memory order, uint256 fillAmount) external nonReentrant onlyOperator notPaused

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Parameters

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order
Order
required
The order to be filled. See Order Structure for details.The order must:
  • Have a valid signature from the maker
  • Not be expired (if expiration is set)
  • Not be cancelled or fully filled
  • Have a valid nonce
  • Have a fee rate below the maximum allowed
  • Reference a registered token ID
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fillAmount
uint256
required
The amount to be filled, always denominated in terms of the maker amount.Must be:
  • Less than or equal to the remaining unfilled amount
  • Greater than 0 for a meaningful fill

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Requirements

  • Caller must be an authorized operator (onlyOperator)
  • Trading must not be paused (notPaused)
  • Function must not be re-entered (nonReentrant)
  • Order must pass all validation checks (signature, expiration, nonce, etc.)
  • Caller must have sufficient balance of the taker asset
  • Order maker must have sufficient balance of the maker asset

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Behavior

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Asset Transfer Flow

  1. Validation: The order is validated including signature verification, expiration check, and nonce validation
  2. Fee Calculation: Fees are calculated based on the order’s feeRateBps and the fill amounts
  3. Asset Transfers:
    • Taker asset (minus fees) is transferred from the operator to the order maker
    • Maker asset is transferred from the order maker to the operator
    • Fees are implicitly collected by the operator (deducted from assets paid by operator)
  4. State Update: Order status is updated with the new remaining amount

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Partial Fills

Orders can be partially filled. The order’s remaining amount is tracked on-chain and updated with each fill. When fully filled, the order is marked as isFilledOrCancelled = true.

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Events

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OrderFilled
event
Emitted when an order is successfully filled.
event OrderFilled(
    bytes32 indexed orderHash,
    address indexed maker,
    address indexed taker,
    uint256 makerAssetId,
    uint256 takerAssetId,
    uint256 makerAmountFilled,
    uint256 takerAmountFilled,
    uint256 fee
)
  • orderHash: Hash of the filled order
  • maker: Address of the order maker
  • taker: Address of the taker (operator calling fillOrder)
  • makerAssetId: Token ID of the asset sold by maker (0 for collateral)
  • takerAssetId: Token ID of the asset bought by maker (0 for collateral)
  • makerAmountFilled: Amount of maker asset transferred
  • takerAmountFilled: Amount of taker asset transferred
  • fee: Fee charged to the maker on their proceeds
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FeeCharged
event
Emitted when a fee is charged (if fee > 0).
event FeeCharged(
    address indexed receiver,
    uint256 indexed tokenId,
    uint256 amount
)

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Errors

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NotOperator
error
Caller is not an authorized operator
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Paused
error
Trading is currently paused
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OrderExpired
error
Order has passed its expiration timestamp
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OrderFilledOrCancelled
error
Order has already been fully filled or cancelled
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InvalidSignature
error
Order signature is invalid
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InvalidNonce
error
Order nonce is invalid (maker has incremented their nonce)
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FeeTooHigh
error
Order fee rate exceeds the maximum allowed
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MakingGtRemaining
error
Fill amount exceeds the remaining unfilled amount
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NotTaker
error
Order specifies a specific taker and caller is not that address

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Example Usage

// Create a BUY order for YES tokens
Order memory order = Order({
    salt: 1,
    maker: 0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb,
    signer: 0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb,
    taker: address(0), // Public order
    tokenId: yesTokenId,
    makerAmount: 50_000_000, // 50 USDC (6 decimals)
    takerAmount: 100_000_000, // 100 YES tokens
    expiration: 0, // No expiration
    nonce: 0,
    feeRateBps: 100, // 1% fee
    side: Side.BUY,
    signatureType: SignatureType.EOA,
    signature: orderSignature
});

// Fill 50% of the order (25 USDC worth)
uint256 fillAmount = 25_000_000;

// As an operator, fill the order
exchange.fillOrder(order, fillAmount);

// Result:
// - Operator receives 25 USDC from maker
// - Maker receives ~50 YES tokens (minus 1% fee)
// - Order can be filled again for remaining 25 USDC

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See Also

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