> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cow.bleu.builders/llms.txt
> Use this file to discover all available pages before exploring further.

# GPv2Order API

> Order library API providing core data structures and utilities for Gnosis Protocol v2

# GPv2Order API

The `GPv2Order` library provides core order data structures and utilities for Gnosis Protocol v2, handling order hashing, UID packing, and parameter extraction.

## Data Structure

```solidity theme={null}
struct Data {
    IERC20 sellToken;
    IERC20 buyToken;
    address receiver;
    uint256 sellAmount;
    uint256 buyAmount;
    uint32 validTo;
    bytes32 appData;
    uint256 feeAmount;
    bytes32 kind;
    bool partiallyFillable;
    bytes32 sellTokenBalance;
    bytes32 buyTokenBalance;
}
```

| Field               | Type      | Description                                              |
| ------------------- | --------- | -------------------------------------------------------- |
| `sellToken`         | `IERC20`  | Token to sell                                            |
| `buyToken`          | `IERC20`  | Token to buy                                             |
| `receiver`          | `address` | Recipient of buy tokens (`address(0)` defaults to owner) |
| `sellAmount`        | `uint256` | Amount of sell token                                     |
| `buyAmount`         | `uint256` | Amount of buy token                                      |
| `validTo`           | `uint32`  | Order expiration as Unix timestamp                       |
| `appData`           | `bytes32` | Application-specific metadata                            |
| `feeAmount`         | `uint256` | Fee amount in sell token                                 |
| `kind`              | `bytes32` | Order kind (`KIND_SELL` or `KIND_BUY`)                   |
| `partiallyFillable` | `bool`    | Whether partial fills are allowed                        |
| `sellTokenBalance`  | `bytes32` | Source of sell tokens                                    |
| `buyTokenBalance`   | `bytes32` | Destination of buy tokens                                |

## Constants

```solidity theme={null}
bytes32 constant KIND_SELL = keccak256("sell");
bytes32 constant KIND_BUY = keccak256("buy");
bytes32 constant BALANCE_ERC20 = keccak256("erc20");
bytes32 constant BALANCE_EXTERNAL = keccak256("external");
bytes32 constant BALANCE_INTERNAL = keccak256("internal");
uint256 constant UID_LENGTH = 56;
```

## Functions

### hash

Generates the EIP-712 signing digest for an order.

```solidity theme={null}
function hash(
    Data memory order,
    bytes32 domainSeparator
) internal pure returns (bytes32);
```

### actualReceiver

Resolves the receiver address, returning the owner if receiver is `address(0)`.

```solidity theme={null}
function actualReceiver(
    Data memory order,
    address owner
) internal pure returns (address);
```

### packOrderUidParams

Encodes the 56-byte order UID from its components.

```solidity theme={null}
function packOrderUidParams(
    bytes memory orderUid,
    bytes32 orderDigest,
    address owner,
    uint32 validTo
) internal pure;
```

### extractOrderUidParams

Decodes UID components from a packed order UID.

```solidity theme={null}
function extractOrderUidParams(
    bytes calldata orderUid
) internal pure returns (
    bytes32 orderDigest,
    address owner,
    uint32 validTo
);
```

## Order UID Format

The 56-byte UID is packed as:

| Bytes | Field                       |
| ----- | --------------------------- |
| 0-31  | Order digest (EIP-712 hash) |
| 32-51 | Owner address               |
| 52-55 | `validTo` timestamp         |

All functions use assembly optimization for gas efficiency.