# protocol
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[Documentation](https://docs.rs/protocol)
Easy protocol definitions in Rust.
This crate adds a custom derive that can be added to types, allowing
structured data to be sent and received from any IO stream.
Networking is built-in, with special support for TCP and UDP.
The protocol you define can be used outside of networking too - see the `Parcel::from_raw_bytes` and `Parcel::raw_bytes` methods.
This crate also provides:
* [TCP](https://docs.rs/protocol/latest/protocol/wire/stream/index.html) and [UDP](https://docs.rs/protocol/latest/protocol/wire/dgram/index.html) modules for easy sending and receiving of `Parcel`s
* A generic [middleware](https://docs.rs/protocol/latest/protocol/wire/middleware/index.html) library for automatic transformation of sent/received data
* Middleware has already been written to support [compression](https://docs.rs/protocol/latest/protocol/wire/middleware/compression/index.html)
* Custom middleware can be implemented via a trait with two methods
Checkout the [examples](./examples) folder for usage.
## Usage
Add this to your `Cargo.toml`:
```toml
[dependencies]
protocol = "3.2"
protocol-derive = "3.2"
```
## Under the hood
The most interesting part here is the [`protocol::Parcel`](https://docs.rs/protocol/latest/protocol/trait.Parcel.html) trait. Any type that implements this trait can then be serialized to and from a byte stream. All primitive types, standard collections, tuples, and arrays implement this trait.
This crate becomes particularly useful when you define your own `Parcel` types. You can use `#[derive(Protocol)]` to do this. Note that in order for a type to implement `Parcel`, it must also implement `Clone`, `Debug`, and `PartialEq`.
```rust
#[derive(Parcel, Clone, Debug, PartialEq)]
pub struct Health(f32);
#[derive(Parcel, Clone, Debug, PartialEq)]
pub struct SetPlayerPosition {
pub position: (f32, f32),
pub health: Health,
pub values: Vec<String>,
}
```
### Custom derive
Any user-defined type can have the `Parcel` trait automatically derived.
## Example
```rust
#[macro_use] extern crate protocol_derive;
#[macro_use] extern crate protocol;
#[derive(Protocol, Clone, Debug, PartialEq)]
pub struct Handshake;
#[derive(Protocol, Clone, Debug, PartialEq)]
pub struct Hello {
id: i64,
data: Vec<u8>,
}
#[derive(Protocol, Clone, Debug, PartialEq)]
pub struct Goodbye {
id: i64,
reason: String,
}
#[derive(Protocol, Clone, Debug, PartialEq)]
pub struct Node {
name: String,
enabled: bool
}
#[protocol(discriminant = "integer")]
#[derive(Protocol, Clone, Debug, PartialEq)]
pub enum PacketKind {
#[protocol(discriminator(0x00))]
Handshake(Handshake),
#[protocol(discriminator(0xaa))]
Hello(Hello),
#[protocol(discriminator(0xaf))]
Goodbye(Goodbye),
}
fn main() {
use std::net::TcpStream;
let stream = TcpStream::connect("127.0.0.1:34254").unwrap();
let mut connection = protocol::wire::stream::Connection::new(stream, protocol::wire::middleware::pipeline::default());
connection.send_packet(&Packet::Handshake(Handshake)).unwrap();
connection.send_packet(&Packet::Hello(Hello { id: 0, data: vec![ 55 ]})).unwrap();
connection.send_packet(&Packet::Goodbye(Goodbye { id: 0, reason: "leaving".to_string() })).unwrap();
loop {
if let Some(response) = connection.receive_packet().unwrap() {
println!("{:?}", response);
break;
}
}
}
```
## Enums
### Discriminators
Enum values can be transmitted either by their 1-based variant index, or by transmitting the string name of each variant.
**NOTE:** The default behaviour is to use *the variant name as a string* (`string`).
This behaviour can be changed by the `#[protocol(discriminant = "<type>")]` attribute.
Supported discriminant types:
* `string` (default)
* This transmits the enum variant name as the over-the-wire discriminant
* This uses more bytes per message, but it very flexible
* `integer`
* This transmits the 1-based variant number as the over-the-wire discriminant
* If enum variants have explicit discriminators, the
* Enum variants cannot be reordered in the source without breaking the protocol
```rust
#[derive(Protocol, Clone, Debug, PartialEq)]
#[protocol(discriminant = "string")]
pub enum PlayerState {
Stationary,
Flying { velocity: (f32,f32,f32) },
// Discriminators can be explicitly specified.
#[protocol(discriminator("ArbitraryOverTheWireName"))]
Jumping { height: f32 },
}
```
### Misc
You can rename the variant for their serialisation.
```rust
#[derive(Protocol, Clone, Debug, PartialEq)]
#[protocol(discriminant = "string")]
pub enum Foo {
Bar,
#[protocol(name = "Biz")] // the Bing variant will be send/received as 'Biz'.
Bing,
Baz,
}
```