rust-libp2p/swarm/src/lib.rs

// Copyright 2017 Parity Technologies (UK) Ltd.
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// TODO: use this once stable ; for now we just copy-paste the content of the README.md
//#![doc(include = "../README.md")]

//! Transport, protocol upgrade and swarm systems of *libp2p*.
//!
//! This crate contains all the core traits and mechanisms of the transport and swarm systems
//! of *libp2p*.
//!
//! # The `Transport` trait
//!
//! The main trait that this crate provides is `Transport`, which provides the `dial` and
//! `listen_on` methods and can be used to dial or listen on a multiaddress. The `swarm` crate
//! itself does not provide any concrete (ie. non-dummy, non-adapter) implementation of this trait.
//! It is implemented on structs that are provided by external crates, such as `TcpConfig` from
//! `tcp-transport`, `UdpConfig`, or `WebsocketConfig` (note: as of the writing of this
//! documentation, the last two structs don't exist yet).
//!
//! Each implementation of `Transport` only supports *some* multiaddress protocols, for example
//! the `TcpConfig` struct only supports multiaddresses that look like `/ip*/*.*.*.*/tcp/*`. It is
//! possible to group two implementations of `Transport` with the `or_transport` method, in order
//! to obtain a single object that supports the protocols of both objects at once. This can be done
//! multiple times in a row in order to chain as many implementations as you want.
//!
//! // TODO: right now only tcp-transport exists, we need to add an example for chaining
//! //       multiple transports once that makes sense
//!
//! ## The `MuxedTransport` trait
//!
//! The `MuxedTransport` trait is an extension to the `Transport` trait, and is implemented on
//! transports that can receive incoming connections on streams that have been opened with `dial()`.
//!
//! The trait provides the `next_incoming()` method, which returns a future that will resolve to
//! the next substream that arrives from a dialed node.
//!
//! > **Note**: This trait is mainly implemented for transports that provide stream muxing
//! >           capabilities, but it can also be implemented in a dummy way by returning an empty
//! >           iterator.
//!
//! # Connection upgrades
//!
//! Once a socket has been opened with a remote through a `Transport`, it can be *upgraded*. This
//! consists in negotiating a protocol with the remote (through `multistream-select`), and applying
//! that protocol on the socket.
//!
//! A potential connection upgrade is represented with the `ConnectionUpgrade` trait. The trait
//! consists in a protocol name plus a method that turns the socket into an `Output` object whose
//! nature and type is specific to each upgrade.
//!
//! There exists three kinds of connection upgrades: middlewares, muxers, and actual protocols.
//!
//! ## Middlewares
//!
//! Examples of middleware connection upgrades include `PlainTextConfig` (dummy upgrade) or
//! `SecioConfig` (encyption layer, provided by the `secio` crate).
//!
//! The output of a middleware connection upgrade implements the `AsyncRead` and `AsyncWrite`
//! traits, just like sockets do.
//!
//! A middleware can be applied on a transport by using the `with_upgrade` method of the
//! `Transport` trait. The return value of this method also implements the `Transport` trait, which
//! means that you can call `dial()` and `listen_on()` on it in order to directly obtain an
//! upgraded connection or a listener that will yield upgraded connections. Similarly, the
//! `next_incoming()` method will automatically apply the upgrade on both the dialer and the
//! listener. An error is produced if the remote doesn't support the protocol corresponding to the
//! connection upgrade.
//!
//! ```
//! extern crate libp2p_swarm;
//! extern crate libp2p_tcp_transport;
//! extern crate tokio_core;
//!
//! use libp2p_swarm::Transport;
//!
//! # fn main() {
//! let tokio_core = tokio_core::reactor::Core::new().unwrap();
//! let tcp_transport = libp2p_tcp_transport::TcpConfig::new(tokio_core.handle());
//! let upgraded = tcp_transport.with_upgrade(libp2p_swarm::upgrade::PlainTextConfig);
//!
//! // upgraded.dial(...)   // automatically applies the plain text protocol on the socket
//! # }
//! ```
//!
//! ## Muxers
//!
//! The concept of *muxing* consists in using a single stream as if it was multiple substreams.
//!
//! If the output of the connection upgrade instead implements the `StreamMuxer` and `Clone`
//! traits, then you can turn the `UpgradedNode` struct into a `ConnectionReuse` struct by calling
//! `ConnectionReuse::from(upgraded_node)`.
//!
//! The `ConnectionReuse` struct then implements the `Transport` and `MuxedTransport` traits, and
//! can be used to dial or listen to multiaddresses, just like any other transport. The only
//! difference is that dialing a node will try to open a new substream on an existing connection
//! instead of opening a new one every time.
//!
//! > **Note**: Right now the `ConnectionReuse` struct is not fully implemented.
//!
//! TODO: add an example once the multiplex pull request is merged
//!
//! ## Actual protocols
//!
//! *Actual protocols* work the same way as middlewares, except that their `Output` doesn't
//! implement the `AsyncRead` and `AsyncWrite` traits. This means that that the return value of
//! `with_upgrade` does **not** implement the `Transport` trait and thus cannot be used as a
//! transport.
//!
//! However the `UpgradedNode` struct returned by `with_upgrade` still provides methods named
//! `dial`, `listen_on`, and `next_incoming`, which will yield you a `Future` or a `Stream`,
//! which you can use to obtain the `Output`. This `Output` can then be used in a protocol-specific
//! way to use the protocol.
//!
//! ```no_run
//! extern crate futures;
//! extern crate libp2p_ping;
//! extern crate libp2p_swarm;
//! extern crate libp2p_tcp_transport;
//! extern crate tokio_core;
//!
//! use futures::Future;
//! use libp2p_ping::Ping;
//! use libp2p_swarm::Transport;
//!
//! # fn main() {
//! let mut core = tokio_core::reactor::Core::new().unwrap();
//!
//! let ping_finished_future = libp2p_tcp_transport::TcpConfig::new(core.handle())
//!     // We have a `TcpConfig` struct that implements `Transport`, and apply a `Ping` upgrade on it.
//!     .with_upgrade(Ping)
//!     // TODO: right now the only available protocol is ping, but we want to replace it with
//!     //       something that is more simple to use
//!     .dial("127.0.0.1:12345".parse::<libp2p_swarm::Multiaddr>().unwrap()).unwrap_or_else(|_| panic!())
//!     .and_then(|((mut pinger, service), _)| {
//!         pinger.ping().map_err(|_| panic!()).select(service).map_err(|_| panic!())
//!     });
//!
//! // Runs until the ping arrives.
//! core.run(ping_finished_future).unwrap();
//! # }
//! ```
//!
//! ## Grouping protocols
//!
//! You can use the `.or_upgrade()` method to group multiple upgrades together. The return value
//! also implements the `ConnectionUpgrade` trait and will choose one of the protocols amongst the
//! ones supported.
//!
//! # Swarm
//!
//! Once you have created an object that implements the `Transport` trait, you can put it in a
//! *swarm*. This is done by calling the `swarm()` freestanding function with the transport
//! alongside with a function or a closure that will turn the output of the upgrade (usually an
//! actual protocol, as explained above) into a `Future` producing `()`.
//!
//! ```no_run
//! extern crate futures;
//! extern crate libp2p_ping;
//! extern crate libp2p_swarm;
//! extern crate libp2p_tcp_transport;
//! extern crate tokio_core;
//!
//! use futures::Future;
//! use libp2p_ping::Ping;
//! use libp2p_swarm::Transport;
//!
//! # fn main() {
//! let mut core = tokio_core::reactor::Core::new().unwrap();
//!
//! let transport = libp2p_tcp_transport::TcpConfig::new(core.handle())
//!     .with_dummy_muxing();
//!
//! let (swarm_controller, swarm_future) = libp2p_swarm::swarm(transport, Ping, |(mut pinger, service), client_addr| {
//!     pinger.ping().map_err(|_| panic!())
//!         .select(service).map_err(|_| panic!())
//!         .map(|_| ())
//! });
//!
//! // The `swarm_controller` can then be used to do some operations.
//! swarm_controller.listen_on("/ip4/0.0.0.0/tcp/0".parse().unwrap());
//!
//! // Runs until everything is finished.
//! core.run(swarm_future).unwrap();
//! # }
//! ```

extern crate bytes;
extern crate fnv;
#[macro_use]
extern crate futures;
#[macro_use]
extern crate log;
extern crate multistream_select;
extern crate parking_lot;
extern crate smallvec;
extern crate tokio_io;

/// Multi-address re-export.
pub extern crate multiaddr;

mod connection_reuse;
mod either;

pub mod muxing;
pub mod swarm;
pub mod transport;
pub mod upgrade;

pub use self::connection_reuse::ConnectionReuse;
pub use self::multiaddr::{AddrComponent, Multiaddr};
pub use self::muxing::StreamMuxer;
pub use self::swarm::{swarm, SwarmController, SwarmFuture};
pub use self::transport::{MuxedTransport, Transport};
pub use self::upgrade::{ConnectionUpgrade, Endpoint};