Lib.rs

Orderbook program which can be used with generic assets.

Overview

This program is intended to be called upon by other programs that implement specific on-chain orderbooks. These "caller" program can use the agnostic orderbook as an underlying infrastructure.

There are two ways to interact with an asset agnostic orderbook :

• creating a new order
• cancelling an existing order

The AAOB program outputs information through the event queue account in of two ways:

• instantaneous order information through the event queue's register (accessible through the read_register primitive).
• the queue itself

Creating an order

The [new_order][fn@instruction::new_order] primitive will push a new order to the orderbook which will optionally match with existing orders if its limit price crosses the spread. The result of this is a series of matching events pushed to the event queue, as well as the writing of a new order to the orderbook, which will become immediately available to be matched agains other orders. An OrderSummary object is also written to the event queue's register, yielding a unique order identifier which will be valid for the whole lifetime of the order : until it is completely matched or cancelled (if it posted).

More information about different parameters for this primitive can be found here.

Cancelling an order

The [cancel_order][fn@instruction::cancel_order] primitive will act on orders which are posted to the orderbook. It will completely erase a posted order from the orderbook. The instruction only requires the order_id.

Processing the queue

On the caller program's side, the queue can be parsed as an EventQueue object. Its peek_at method can be used to retrieve particular events. Alternatively, the events can be iterated through with the object's iter method.

An Event object describes matching operations as well as purging of orders from the orderbook. Information about the matched parties is provided through the callback_info fields. An example of such information would be a user account or user wallet, enabling the caller program to perform a transfer of assets between those accounts. A prefix of len callback_id_len of this information is also used by the program to detect matches which would result in self trading.

Once event processing is over, it is essential to pop the processed events off the queue. This can be done through the [consume_events][fn@instruction::consume_events] primitive. In general, the event processing logic should be handled by a dedicated cranker on the caller program's side.