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Merge pull request #62 from tomaka/swarm-docs-pass2

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More documentation for libp2p-swarm
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Fredrik Harrysson 2017-12-07 12:46:59 +01:00 committed by GitHub
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70
libp2p-swarm/README.md
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@ -5,19 +5,20 @@ This crate contains all the core traits and mechanisms of the transport system o
# 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. This crate does not
provide any concrete (non-dummy, non-adapter) implementation of this trait. It is implemented
on structs such as `TcpConfig`, `UdpConfig`, `WebsocketConfig` that are provided by external
crates.
`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/*`. Two
implementations of `Transport` can be grouped together with the `or_transport` method, in order
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 order to chain as many implementations as you want.
multiple times in a row in order to chain as many implementations as you want.
// TODO: right now only tcp-transport exists, but we need to add an example for chaining multiple
// transports once that makes sense
// TODO: right now only tcp-transport exists, we need to add an example for chaining
// multiple transports once that makes sense
# Connection upgrades
@ -29,22 +30,23 @@ A potential connection upgrade is represented with the `ConnectionUpgrade` 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 two kinds of connection upgrades: middlewares, and actual protocols.
There exists three kinds of connection upgrades: middlewares, muxers, and actual protocols.
## Middlewares
Examples of middleware protocol upgrades include `PlainTextConfig` (dummy upgrade),
`SecioConfig` (encyption layer), or `MultiplexConfig`.
Examples of middleware connection upgrades include `PlainTextConfig` (dummy upgrade) or
`SecioConfig` (encyption layer, provided by the `secio` crate).
The output of a middleware protocol upgrade must implement the `AsyncRead` and `AsyncWrite`
The output of a middleware connection upgrade must implement the `AsyncRead` and `AsyncWrite`
traits, just like sockets do.
A middleware can be applied 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. An
error is produced if the remote doesn't support the protocol that you are trying to negotiate.
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. An error is produced if
the remote doesn't support the protocol corresponding to the connection upgrade.
```
```rust
extern crate libp2p_swarm;
extern crate libp2p_tcp_transport;
extern crate tokio_core;
@ -53,22 +55,37 @@ use libp2p_swarm::Transport;
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::PlainText);
let upgraded = tcp_transport.with_upgrade(libp2p_swarm::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` trait, 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.
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. The consequence of this is that the return
value of `with_upgrade` **cannot** doesn't implement the `Transport` trait and thus cannot be
used as a transport.
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 value returned by `with_upgrade` still provides methods named `dial` and
`listen_on`, which will yield you respectively 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.
However the `UpgradedNode` struct returned by `with_upgrade` still provides methods named
`dial` and `listen_on`, which will yield you respectively 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.
```rust
extern crate futures;
@ -102,4 +119,3 @@ core.run(ping_finished_future).unwrap();
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.

65
libp2p-swarm/src/lib.rs
View File

@ -28,19 +28,20 @@
//! # 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. This crate does not
//! provide any concrete (non-dummy, non-adapter) implementation of this trait. It is implemented
//! on structs such as `TcpConfig`, `UdpConfig`, `WebsocketConfig` that are provided by external
//! crates.
//! `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/*`. Two
//! implementations of `Transport` can be grouped together with the `or_transport` method, in order
//! 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 order to chain as many implementations as you want.
//! multiple times in a row in order to chain as many implementations as you want.
//!
//! // TODO: right now only tcp-transport exists, but we need to add an example for chaining multiple
//! // transports once that makes sense
//! // TODO: right now only tcp-transport exists, we need to add an example for chaining
//! // multiple transports once that makes sense
//!
//! # Connection upgrades
//!
@ -52,20 +53,21 @@
//! 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 two kinds of connection upgrades: middlewares, and actual protocols.
//! There exists three kinds of connection upgrades: middlewares, muxers, and actual protocols.
//!
//! ## Middlewares
//!
//! Examples of middleware protocol upgrades include `PlainTextConfig` (dummy upgrade),
//! `SecioConfig` (encyption layer), or `MultiplexConfig`.
//! Examples of middleware connection upgrades include `PlainTextConfig` (dummy upgrade) or
//! `SecioConfig` (encyption layer, provided by the `secio` crate).
//!
//! The output of a middleware protocol upgrade must implement the `AsyncRead` and `AsyncWrite`
//! The output of a middleware connection upgrade must implement the `AsyncRead` and `AsyncWrite`
//! traits, just like sockets do.
//!
//! A middleware can be applied 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. An
//! error is produced if the remote doesn't support the protocol that you are trying to negotiate.
//! 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. An error is produced if
//! the remote doesn't support the protocol corresponding to the connection upgrade.
//!
//! ```
//! extern crate libp2p_swarm;
@ -82,18 +84,33 @@
//! // 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` trait, 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.
//!
//! 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. The consequence of this is that the return
//! value of `with_upgrade` **cannot** doesn't implement the `Transport` trait and thus cannot be
//! used as a transport.
//! 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 value returned by `with_upgrade` still provides methods named `dial` and
//! `listen_on`, which will yield you respectively 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.
//! However the `UpgradedNode` struct returned by `with_upgrade` still provides methods named
//! `dial` and `listen_on`, which will yield you respectively 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;