Crate nemo [] [src]

Nemo provides session type abstractions for asynchronous networking protocols. It can be used to build high performance, memory safe and type-safe protocol implementations.

What are session types?

Session types allow you to encode the description of a protocol in the type system. The goal is to ensure that two clients can never disagree about their state or expectations when communicating. Through session types, it is possible to define protocols that must be implemented properly -- your code simply will not compile otherwise.



Channels are implementations of IO which can be used when building Session and designing protocols.


Peano numbers are natural numbers expressed as successions of zero. We use them in our API to provide "nested" protocol escaping, as you must indicate the number of layers you wish to escape from.


Session types encode the current state of a communication channel. It is not possible to change to another state without following the protocol.





Channels are provided to handlers to act as a "courier" for the session type and a guard for the IO backend.


Handlers must return Defer to indicate to the Session how to proceed in the future. Defer can be obtained by calling .defer() on the channel, or by calling .close() when the session is End.



Handler is implemented on Protocol for every session type you expect to defer, including the initial state.


This trait is implemented by backing IO structures to offer an interface for bi-directional channels. Discriminants are sent and received by Channel to indicate protocol changes; they tend to be smaller numbers, and so a variable length integer could be sent over a network instead of the raw usize.


A Protocol describes the underlying protocol, including the "initial" session type. Handlers are defined over concrete Protocols to implement the behavior of a protocol in a given SessionType.


An implementation of this trait provides sending and receiving functionality to Channel for an arbitrary T. Channel will only ever call these functions if it expects a T, so long as outside of this trait and IO the backing channel cannot be accessed.