nbio

Description

This crate aims to make it easier to reason about uni-directional and bi-directional nonblocking I/O.

This is done using patterns that extend beyond dealing directly with raw bytes, the [std::io::Read] and [std::io::Write] traits, and [std::io::ErrorKind::WouldBlock] errors. Since this crate's main focus is nonblocking I/O, all [Session] implementations provided by this crate are non-blocking by default.

Sessions

The core [Session] trait encapsulates controlling a single instance of a connection or logical session. To differentiate with the [std::io::Read] and [std::io::Write] traits that only deal with raw bytes, this crate uses [Publish] and [Receive] terminology, which utilize associated types to handle any payload type.

A [Session] impl is typically also either [Publish], [Receive], or both. While the [tcp] module provides a [Session] implementation that provides unframed non-blocking binary IO operations, other [Session] impls are able to provide significantly more functionality using the same non-blocking patterns.

This crate will often use the term Duplex to distinguish a [Session] that is both [Publish] and [Receive].

Associated Types

Sessions operate on implementation-specific [Receive::ReceivePayload] and [Publish::PublishPayload] types. These types are able to utilize a lifetime 'a, which is tied to the lifetime of the underlying [Session], providing the ability for implementations to reference internal buffers or queues without copying.

Errors

The philosophy of this crate is that an [Err] should always represent a transport or protocol-level error. An [Err] should not be returned by a function as a condition that should be handled during normal branching logic. As a result, instead of forcing you to handle [std::io::ErrorKind::WouldBlock] everywhere you deal with nonblocking code, this crate will indicate partial receive/publish operations using [ReceiveOutcome::Idle], [ReceiveOutcome::Buffered], and [PublishOutcome::Incomplete] as [Result::Ok].

Features

The [Session] impls in this crate are enabled by certain features. By default, all features are enabled for rapid prototyping. In a production codebase, you will likey want to pick and choose your required features.

Feature list:

• http
• tcp
• websocket

Examples

Streaming TCP

The following example shows how to use streaming TCP to publish and receive a traditional stream of bytes.

use nbio::{Publish, PublishOutcome, Receive, ReceiveOutcome, Session};
use nbio::tcp::TcpSession;

// establish connection
let mut client = TcpSession::connect("192.168.123.456:54321").unwrap();

// publish some bytes until completion
let mut pending_publish = "hello world!".as_bytes();
while let PublishOutcome::Incomplete(pending) = client.publish(pending_publish).unwrap() {
    pending_publish = pending;
    client.drive().unwrap();
}

// print received bytes
loop {
    if let ReceiveOutcome::Payload(payload) = client.receive().unwrap() {
        println!("received: {payload:?}");
    }
}

Framing TCP

The following example shows how to [frame] messages over TCP to publish and receive payloads framed with a preceeding u64 length field. Notice how it is almost identical to the code above, except it guarantees that read slices are always identical to their corresponding write slices.

use nbio::{Publish, PublishOutcome, Receive, ReceiveOutcome, Session};
use nbio::tcp::TcpSession;
use nbio::frame::{FrameDuplex, U64FrameDeserializer, U64FrameSerializer};

// establish connection wrapped in a framing session
let client = TcpSession::connect("192.168.123.456:54321").unwrap();
let mut client = FrameDuplex::new(client, U64FrameDeserializer::new(), U64FrameSerializer::new(), 4096);

// publish some bytes until completion
let mut pending_publish = "hello world!".as_bytes();
while let PublishOutcome::Incomplete(pending) = client.publish(pending_publish).unwrap() {
    pending_publish = pending;
    client.drive().unwrap();
}

// print received bytes
loop {
    if let ReceiveOutcome::Payload(payload) = client.receive().unwrap() {
        println!("received: {payload:?}");
    }
}

HTTP Client

The following example shows how to use the [http] module to drive an HTTP 1.x request/response using the same non-blocking model. Notice how the primitives of driving a buffered write to completion and receiving a framed response is the same as any other framed session. In fact, the conn returned by client.request(..) is simply a [frame::FrameDuplex] that utilizes a [http::Http1RequestSerializer] and [http::Http1ResponseDeserializer].

use http::Request;
use nbio::{Receive, Session, ReceiveOutcome};
use nbio::http::HttpClient;
use tcp_stream::OwnedTLSConfig;

// create the client and make the request
let mut client = HttpClient::new();
let mut conn = client
    .request(Request::get("http://icanhazip.com").body(()).unwrap())
    .unwrap();

// drive and read the conn until a full response is received
loop {
    conn.drive().unwrap();
    if let ReceiveOutcome::Payload(r) = conn.receive().unwrap() {
        println!("Response Body: {}", String::from_utf8_lossy(r.body()));
        break;
    }
}

WebSocket

The following example sends a message and then receives all subsequent messages from a websocket connection. Just like the HTTP example, this simply encapsulates [frame::FrameDuplex] but utilizes a [websocket::WebSocketFrameSerializer] and [websocket::WebSocketFrameDeserializer]. All TLS and WebSocket handshaking is taken care of during the [SessionStatus::Establishing] [Session::status] workflow.

use nbio::{Publish, PublishOutcome, Receive, Session, SessionStatus, ReceiveOutcome};
use nbio::websocket::{Message, WebSocketSession};

// create the client and make the request
let mut session = WebSocketSession::connect("wss://echo.websocket.org/", None).unwrap();
while session.status() == SessionStatus::Establishing {
     session.drive().unwrap();
}

// publish a message
let mut pending_publish = Message::Text("hello world!".into());
while let PublishOutcome::Incomplete(pending) = session.publish(pending_publish).unwrap() {
    pending_publish = pending;
    session.drive().unwrap();
}

// drive and receive messages
loop {
    session.drive().unwrap();
    if let ReceiveOutcome::Payload(r) = session.receive().unwrap() {
        println!("Received: {:?}", r);
        break;
    }
}

License: MIT OR Apache-2.0