zbus

A Rust API for D-Bus communication. The goal is to provide a safe and simple high- and low-level API akin to GDBus, that doesn't depend on C libraries.

The project is divided into three main crates:

zbus

The zbus crate provides the main API you will use to interact with D-Bus from Rust. It takes care of the establishment of a connection, the creation, sending and receiving of different kind of D-Bus messages (method calls, signals etc) for you.

zbus crate is currently Linux-specific¹.

Status: Stable².

Getting Started

The best way to get started with zbus is the book, where we start with basic D-Bus concepts and explain with code samples, how zbus makes D-Bus easy.

Example code

Client

This code display a notification on your Freedesktop.org-compatible OS:

use std::{collections::HashMap, error::Error};

use zbus::{Connection, dbus_proxy};
use zvariant::Value;

#[dbus_proxy(
    interface = "org.freedesktop.Notifications",
    default_service = "org.freedesktop.Notifications",
    default_path = "/org/freedesktop/Notifications"
)]
trait Notifications {
    fn notify(
        &self,
        app_name: &str,
        replaces_id: u32,
        app_icon: &str,
        summary: &str,
        body: &str,
        actions: &[&str],
        hints: &HashMap<&str, &Value<'_>>,
        expire_timeout: i32,
    ) -> zbus::Result<u32>;
}

// Although we use `async-std` here, you can use any async runtime of choice.
#[async_std::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let connection = Connection::session().await?;

    // `dbus_proxy` macro creates `NotificationProxy` based on `Notifications` trait.
    let proxy = NotificationsProxy::new(&connection).await?;
    let reply = proxy.notify(
        "my-app",
        0,
        "dialog-information",
        "A summary",
        "Some body",
        &[],
        &HashMap::new(),
        5000,
    ).await?;
    dbg!(reply);

    Ok(())
}

Server

A simple service that politely greets whoever calls its SayHello method:

use std::{
    error::Error,
    thread::sleep,
    time::Duration,
};
use zbus::{ObjectServer, ConnectionBuilder, dbus_interface, fdo};

struct Greeter {
    count: u64
}

#[dbus_interface(name = "org.zbus.MyGreeter1")]
impl Greeter {
    // Can be `async` as well.
    fn say_hello(&mut self, name: &str) -> String {
        self.count += 1;
        format!("Hello {}! I have been called: {}", name, self.count)
    }
}

// Although we use `async-std` here, you can use any async runtime of choice.
#[async_std::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let greeter = Greeter { count: 0 };
    let _ = ConnectionBuilder::session()?
        .name("org.zbus.MyGreeter")?
        .serve_at("/org/zbus/MyGreeter", greeter)?
        .build()
        .await?;

    // Do other things or go to sleep.
    sleep(Duration::from_secs(60));

    Ok(())
}

You can use the following command to test it:

$ busctl --user call org.zbus.MyGreeter /org/zbus/MyGreeter org.zbus.MyGreeter1 SayHello s "Maria"
Hello Maria!
s

Blocking API

While zbus is primarily asynchronous (since 2.0), blocking wrappers are provided for convenience.

Compatibility with async runtimes

zbus is runtime-agnostic and should work out of the box with different Rust async runtimes. However, in order to achieve that, zbus spawns a thread per connection to handle various internal tasks. If that is something you would like to avoid, you need to:

• Use ConnectionBuilder and disable the internal_executor flag.
• Ensure the internal executor keeps ticking continuously.

zvariant

This crate provides API for encoding/decoding of data to/from D-Bus wire format. This binary wire format is simple and very efficient and hence useful outside of D-Bus context as well. A modified form of this format, GVariant is very commonly used for efficient storage of arbitrary data and is also supported by this crate.

Status: Stable.

Example code

use std::collections::HashMap;
use byteorder::LE;
use zvariant::{from_slice, to_bytes};
use zvariant::EncodingContext as Context;

// All serialization and deserialization API, needs a context.
let ctxt = Context::<LE>::new_dbus(0);
// You can also use the more efficient GVariant format:
// let ctxt = Context::
     
      ::new_gvariant(0);
     

// i16
let encoded = to_bytes(ctxt, &42i16).unwrap();
let decoded: i16 = from_slice(&encoded, ctxt).unwrap();
assert_eq!(decoded, 42);

// strings
let encoded = to_bytes(ctxt, &"hello").unwrap();
let decoded: &str = from_slice(&encoded, ctxt).unwrap();
assert_eq!(decoded, "hello");

// tuples
let t = ("hello", 42i32, true);
let encoded = to_bytes(ctxt, &t).unwrap();
let decoded: (&str, i32, bool) = from_slice(&encoded, ctxt).unwrap();
assert_eq!(decoded, t);

// Vec
let v = vec!["hello", "world!"];
let encoded = to_bytes(ctxt, &v).unwrap();
let decoded: Vec<&str> = from_slice(&encoded, ctxt).unwrap();
assert_eq!(decoded, v);

// Dictionary
let mut map: HashMap<i64, &str> = HashMap::new();
map.insert(1, "123");
map.insert(2, "456");
let encoded = to_bytes(ctxt, &map).unwrap();
let decoded: HashMap<i64, &str> = from_slice(&encoded, ctxt).unwrap();
assert_eq!(decoded[&1], "123");
assert_eq!(decoded[&2], "456");

zvariant_derive

This crate provides a derive macro to easily implement Type trait on structs and enums.

Status: Stable.

Example code

use zvariant::{EncodingContext, from_slice, to_bytes};
use zvariant::{derive::Type, Type};
use serde::{Deserialize, Serialize};
use byteorder::LE;

#[derive(Deserialize, Serialize, Type, PartialEq, Debug)]
struct Struct<'s> {
    field1: u16,
    field2: i64,
    field3: &'s str,
}

assert_eq!(Struct::signature(), "(qxs)");
let s = Struct {
    field1: 42,
    field2: i64::max_value(),
    field3: "hello",
};
let ctxt = EncodingContext::<LE>::new_dbus(0);
let encoded = to_bytes(ctxt, &s).unwrap();
let decoded: Struct = from_slice(&encoded, ctxt).unwrap();
assert_eq!(decoded, s);

Other crates

Apart from the three crates described above, zbus project also provides a few other crates:

zbus_macros

This crate provides the convenient zbus macros that we already saw in action in the sample code above. However, zbus crate re-exports the macros for your convenience so you do not need to use this crate directly.

Status: Stable.

zbus_polkit

A crate to interact with PolicyKit, a toolkit for defining and handling authorizations. It is used for allowing unprivileged processes to speak to privileged processes.

Status: Stable.

Example code

use zbus::Connection;
use zbus_polkit::policykit1::*;

// Although we use `async-std` here, you can use any async runtime of choice.
#[async_std::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let connection = Connection::system().await?;
    let proxy = AuthorityProxy::new(&connection).await?;
    let subject = Subject::new_for_owner(std::process::id(), None, None)?;
    let result = proxy.check_authorization(
        &subject,
        "org.zbus.BeAwesome",
        &std::collections::HashMap::new(),
        CheckAuthorizationFlags::AllowUserInteraction.into(),
        "",
    ).await?;

    Ok(())
}

zbus_xmlgen

A binary crate that provides a developer tool to generate Rust code from D-Bus XML interface descriptions. It can be used to generate the code directly from a running D-Bus system, session or other service, or using a preexisting XML file for input.

Status: Stable.

Usage

$ cargo install zbus_xmlgen
$ zbus-xmlgen --system org.freedesktop.login1 /org/freedesktop/login1
$ zbus-xmlgen --session org.freedesktop.ScreenSaver /org/freedesktop/ScreenSaver
$ zbus-xmlgen --address unix:abstract=/home/user/.cache/ibus/dbus-fpxKwgbJ org.freedesktop.IBus /org/freedesktop/IBus
$ zbus-xmlgen interface.xml

zbus_names

This crate provides collection of types for various D-Bus bus names.

This is used by zbus (and in future by zbus_macros as well) crate. Other D-Bus crates are also encouraged to use this API in the spirit of cooperation. :)

Status: Stable.

Getting Help

If you need help in using these crates, are looking for ways to contribute, or just want to hang out with the cool kids, please come chat with us in the #zbus:matrix.org Matrix room. If something doesn't seem right, please file an issue.

Portability

All crates are currently Unix-only and will fail to build on non-unix. This is hopefully a temporary limitation. Moreover, integration tests of zbus crate currently require a session bus running on the build host.

License

MIT license LICENSE-MIT