mai

A higher-level event loop built on top of mio. mai manages buffers and streams so you can focus on sending and receiving your protocol's frames.

Status

Largely functional. APIs subject to change.

Getting Started

Using mai requires three steps:

• Selecting a data type to be your protocol's Frame, an actionable message.
• Defining a Codec that knows how to read and write Frames into byte buffers.
• Specifying a Handler to react to new connections, incoming Frames and errors.

Buffer pooling, low-level reads and writes and Token management are handled by mai.

An Echo Client example

Protocol

Implement the Protocol trait by specifying the family of types you'll be using.

```rust use mai::*;

struct EchoCodec; struct EchoClientHandler; struct EchoClient;

impl Protocol for EchoClient { type ByteStream = TcpStream; // vs a UnixStream, for example type Frame = String; type Codec = EchoCodec; type Handler = EchoClientHandler; type Timeout = usize; } ```

Codec

Define methods to encode and decode your frames. Use the return codes to indicate that you got a frame, don't have enough bytes to read a frame yet or that you encountered a protocol error.

```rust

// For a simple Echo server, we can use String as our Frame type. // This codec would work for both a client and server connection. impl Codec for EchoCodec { // Provide a method to try to write a given frame to a byte buffer fn encode(&mut self, message: &String, buffer: &mut [u8]) -> EncodingResult { let bytes = message.as_bytes(); // If the buffer isn't big enough, say so via the return value if bytes.len() > buffer.len() { return Err(EncodingError::InsufficientBuffer); } // Copy the bytes of our String into the buffer for (index, &byte) in bytes.iter().enumerate() { buffer[index] = byte; } // Tell the frame engine how many bytes we wrote Ok(BytesWritten(bytes.len())) }

// Provide a method to try to parse a frame from a byte buffer fn decode(&mut self, buffer: &[u8]) -> DecodingResult { use std::str; // Validate that the buffer contains a utf-8 String let message: String = match str::fromutf8(buffer) { Ok(message) => message.toowned(), // For this example, assume that an invalid message means // that we just don't have enough bytes yet Err(error) => return Err(DecodingError::IncompleteFrame) }; Ok(DecodedFrame::new(message, BytesRead(buffer.len()))) } } ```

FrameHandler

Define callbacks to handle byte stream events: connections, frames, timeouts, errors, and disconnects. ```rust use mai::*;

impl Handler for EchoClientHandler { fn onready(&mut self, context: &mut Context) { let stream = context.stream(); println!("Connected to {:?}", stream.peeraddr()); let message: String = "Supercalifragilisticexpialidocious!".toowned(); stream.send(message); } fn onframe(&mut self, stream: &mut Context, message: String) { let stream = context.stream(); println!("Received a message from {:?}: '{}'", stream.peeraddr(), &message.trimright()); } fn ontimeout(&mut self, timeout: usize) { println!("A timeout has occurred: {:?}", timeout); } fn onerror(&mut self, context: &mut Context, error: &Error) { let stream = context.stream(); println!("Error. {:?}, {:?}", stream.peeraddr(), error); } fn onclosed(&mut self, stream: &Context) { let stream = context.stream(); println!("Disconnected from {:?}", stream.peer_addr()); } } ```

Get to work

Create a ProtocolEngine and hand it any mio type that is Evented+Read+Write. Watch it go! ``rust fn main() { // Create a TcpStream connected tonc` running as an echo server // nc -l -p 2000 -c 'xargs -n1 echo' println!("Connecting to localhost:9999..."); let address = "0.0.0.0:9999".parse().unwrap(); let socket = TcpSocket::v4().unwrap(); let (stream, _complete) = socket.connect(&address).unwrap();

// Hand the TcpStream off to our new ProtocolEngine configured to treat its // byte streams as Echo clients. let protocolengine: ProtocolEngine = mai::protocolengine(EchoClientHandler) .with(InitialBufferSize(Kilobytes(32)) .with(InitialBufferPoolSize(16)) .with(MaxBufferPoolSize(128)) .build(); let token = protocolengine.manage(stream); let _ = protocolengine.wait(); } ```

Creating a Server

Currently mai does not have a built-in way to manage incoming connections. This is being worked on.

Running a server is conceptually a straightforward process: create a separate thread using mio to listen for incoming connections. Each time a client connection is avialable, pass the corresponding TcpStream to the ProtocolEngine running in the background. Until there is a formal API, you can get a channel to send commands to the ProtocolEngine instance by running protocol_engine.command_sender.clone() and sending a Command::Manage(P::ByteStream) message that contains the ByteStream you'd like it to manage.