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#[cfg(test)]
mod test;
use crate::core::{BusEvent, BusListenerCookie, BusListenerFilter, BusListenerScope};
use crate::error::Error;
use crate::handle::Handle;
use futures_channel::mpsc::{UnboundedReceiver, UnboundedSender};
use futures_core::stream::{FusedStream, Stream};
use std::collections::HashSet;
use std::future;
use std::pin::Pin;
use std::task::{Context, Poll};
/// Monitors the bus for the creation and destruction of objects and services.
///
/// `BusListener`s use [`BusListenerFilter`] to specify which objects and/or services to
/// consider. It is possible to register interest in either a set of specific objects (based on
/// their [`ObjectUuid`](crate::core::ObjectUuid)), any object or no objects at all. The same
/// applies also to services. In all cases, filters match both creation and destruction events. It
/// is not possible to limit a `BusListener` to just one type.
///
/// `BusListener`s must be started before they emit events. At this point a [`BusListenerScope`] has
/// to be specified, which controls whether to consider current objects/services, future ones, or
/// both.
///
/// It is also possible to repeatedly start and stop a `BusListener`, as well as add and remove
/// filters at any time. However, some caveats need to be kept in mind:
///
/// - Adding filters will not cause events to be emitted for objects/services which exist already on
/// the bus (if the `BusListener` is started and the scope matches). For this to work, it must be
/// stopped and restarted.
/// - Adding and removing filters is not synchronized with the broker (the respective functions are
/// not `async`). This means that they will not take effect immediately.
///
/// # Examples
///
/// ## Enumerating all current objects and services
///
/// ```
/// use aldrin::core::{BusEvent, BusListenerFilter, BusListenerScope, ObjectUuid, ServiceUuid};
/// # #[tokio::main]
/// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
/// # let broker = aldrin_test::tokio::TestBroker::new();
/// # let handle = broker.add_client().await;
///
/// // Create a few objects and services.
/// let obj1 = handle.create_object(ObjectUuid::new_v4()).await?;
/// let service1 = obj1.create_service(ServiceUuid::new_v4(), 0).await?;
/// let obj2 = handle.create_object(ObjectUuid::new_v4()).await?;
/// let service2 = obj2.create_service(ServiceUuid::new_v4(), 0).await?;
///
/// // Create a bus listener.
/// let mut bus_listener = handle.create_bus_listener().await?;
///
/// // Add filters for all objects and services.
/// bus_listener.add_filter(BusListenerFilter::any_object())?;
/// bus_listener.add_filter(BusListenerFilter::any_object_any_service())?;
///
/// // Start the bus listener and limit the scope to only current objects and services.
/// bus_listener.start(BusListenerScope::Current).await?;
///
/// // Drain the bus listener of all events. When using [`BusListenerScope::Current`], then only
/// // creation events will be emitted and `None` will be returned when the bus listener finishes.
/// # let mut num = 0;
/// while let Some(event) = bus_listener.next_event().await {
/// match event {
/// BusEvent::ObjectCreated(id) => {
/// println!("Object {} found.", id.uuid);
/// }
///
/// BusEvent::ServiceCreated(id) => {
/// println!("Service {} on object {} found.", id.uuid, id.object_id.uuid);
/// }
///
/// BusEvent::ObjectDestroyed(_) | BusEvent::ServiceDestroyed(_) => unreachable!(),
/// }
/// # num += 1;
/// }
/// # assert_eq!(num, 4);
/// # assert!(bus_listener.is_finished());
/// # Ok(())
/// # }
/// ```
#[derive(Debug)]
pub struct BusListener {
cookie: BusListenerCookie,
client: Handle,
filters: HashSet<BusListenerFilter>,
scope: Option<BusListenerScope>,
pending_started: usize,
pending_stopped: usize,
pending_current_finished: usize,
events: UnboundedReceiver<BusListenerEvent>,
}
impl BusListener {
/// Creates a new bus listener.
pub async fn new(client: &Handle) -> Result<Self, Error> {
client.create_bus_listener().await
}
pub(crate) fn new_impl(
cookie: BusListenerCookie,
client: Handle,
events: UnboundedReceiver<BusListenerEvent>,
) -> Self {
Self {
cookie,
client,
filters: HashSet::new(),
scope: None,
pending_started: 0,
pending_stopped: 0,
pending_current_finished: 0,
events,
}
}
/// Returns a handle to the client that was used to create the bus listener.
pub fn client(&self) -> &Handle {
&self.client
}
/// Destroys the bus listener.
///
/// Bus listener are also destroyed implicitly when they fall out of scope.
///
/// Events that have already been emitted by the broker may still be emitted by the bus listener
/// after destroying it.
pub async fn destroy(&mut self) -> Result<(), Error> {
self.client.destroy_bus_listener(self.cookie).await?;
self.events.close();
self.pending_started = 0;
self.pending_stopped = 0;
self.pending_current_finished = 0;
Ok(())
}
/// Adds a filter to the bus listener.
///
/// For an event to be emitted, there must be a filter that matches it. Adding the same filter
/// twice has no effect. In particular, there is no reference counting for filters.
///
/// Note that new filters do not affect events which are already in the bus listener's internal
/// queue.
///
/// # Examples
///
/// ```
/// use aldrin::core::{BusListenerFilter, ObjectUuid};
/// # use uuid::uuid;
/// # #[tokio::main]
/// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
/// # let broker = aldrin_test::tokio::TestBroker::new();
/// # let handle = broker.add_client().await;
/// # let mut bus_listener = handle.create_bus_listener().await?;
///
/// const MY_OBJECT_UUID: ObjectUuid = ObjectUuid(uuid!("0228a930-e194-4b1a-bc3e-6a4defb32527"));
///
/// // Add a filter for `MY_OBJECT_UUID`.
/// bus_listener.add_filter(BusListenerFilter::object(MY_OBJECT_UUID))?;
///
/// // Add a filter for all services of `MY_OBJECT_UUID`.
/// bus_listener.add_filter(BusListenerFilter::specific_object_any_service(MY_OBJECT_UUID))?;
///
/// # Ok(())
/// # }
/// ```
pub fn add_filter(&mut self, filter: BusListenerFilter) -> Result<(), Error> {
if self.filters.insert(filter) {
self.client.add_bus_listener_filter(self.cookie, filter)
} else {
Ok(())
}
}
/// Remove a filter from the bus listener.
///
/// Removing a filter, that isn't present in the bus listener, has no effect.
///
/// Note that filters do not affect events which are already in the bus listener's internal
/// queue. Thus, events that match only a single filter, may still be emitted after removing it.
///
/// # Examples
///
/// ```
/// use aldrin::core::BusListenerFilter;
/// # use uuid::uuid;
/// # #[tokio::main]
/// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
/// # let broker = aldrin_test::tokio::TestBroker::new();
/// # let handle = broker.add_client().await;
/// # let mut bus_listener = handle.create_bus_listener().await?;
///
/// // Remove the filter that matches all services of any object.
/// bus_listener.remove_filter(BusListenerFilter::any_object_any_service())?;
///
/// # Ok(())
/// # }
/// ```
pub fn remove_filter(&mut self, filter: BusListenerFilter) -> Result<(), Error> {
if self.filters.remove(&filter) {
self.client.remove_bus_listener_filter(self.cookie, filter)
} else {
Ok(())
}
}
/// Clears the set of all filters.
///
/// The same caveats as with [`remove_filter`](Self::remove_filter) apply.
pub fn clear_filters(&mut self) -> Result<(), Error> {
if !self.filters.is_empty() {
self.filters.clear();
self.client.clear_bus_listener_filters(self.cookie)
} else {
Ok(())
}
}
/// Returns an iterator of all filters.
///
/// The order in which the filters are returned is unspecified.
pub fn filters(&self) -> impl Iterator<Item = BusListenerFilter> + '_ {
self.filters.iter().copied()
}
/// Checks if a specific filter is present.
///
/// # Examples
///
/// ```
/// use aldrin::core::BusListenerFilter;
/// # use uuid::uuid;
/// # #[tokio::main]
/// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
/// # let broker = aldrin_test::tokio::TestBroker::new();
/// # let handle = broker.add_client().await;
/// # let mut bus_listener = handle.create_bus_listener().await?;
///
/// bus_listener.add_filter(BusListenerFilter::any_object_any_service())?;
/// assert!(bus_listener.has_filter(BusListenerFilter::any_object_any_service()));
///
/// bus_listener.remove_filter(BusListenerFilter::any_object_any_service())?;
/// assert!(!bus_listener.has_filter(BusListenerFilter::any_object_any_service()));
///
/// # Ok(())
/// # }
/// ```
pub fn has_filter(&self, filter: BusListenerFilter) -> bool {
self.filters.contains(&filter)
}
/// Checks if the bus listener has any filters.
///
/// # Examples
///
/// ```
/// use aldrin::core::BusListenerFilter;
/// # use uuid::uuid;
/// # #[tokio::main]
/// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
/// # let broker = aldrin_test::tokio::TestBroker::new();
/// # let handle = broker.add_client().await;
/// # let mut bus_listener = handle.create_bus_listener().await?;
///
/// assert!(!bus_listener.has_any_filters());
///
/// bus_listener.add_filter(BusListenerFilter::any_object_any_service())?;
/// assert!(bus_listener.has_any_filters());
///
/// bus_listener.remove_filter(BusListenerFilter::any_object_any_service())?;
/// assert!(!bus_listener.has_any_filters());
///
/// # Ok(())
/// # }
/// ```
pub fn has_any_filters(&self) -> bool {
!self.filters.is_empty()
}
/// Checks if the bus listener has no filters.
///
/// # Examples
///
/// ```
/// use aldrin::core::BusListenerFilter;
/// # use uuid::uuid;
/// # #[tokio::main]
/// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
/// # let broker = aldrin_test::tokio::TestBroker::new();
/// # let handle = broker.add_client().await;
/// # let mut bus_listener = handle.create_bus_listener().await?;
///
/// assert!(bus_listener.has_no_filters());
///
/// bus_listener.add_filter(BusListenerFilter::any_object_any_service())?;
/// assert!(!bus_listener.has_no_filters());
///
/// bus_listener.remove_filter(BusListenerFilter::any_object_any_service())?;
/// assert!(bus_listener.has_no_filters());
///
/// # Ok(())
/// # }
/// ```
pub fn has_no_filters(&self) -> bool {
self.filters.is_empty()
}
/// Returns the number of filters.
///
/// # Examples
///
/// ```
/// use aldrin::core::BusListenerFilter;
/// # use uuid::uuid;
/// # #[tokio::main]
/// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
/// # let broker = aldrin_test::tokio::TestBroker::new();
/// # let handle = broker.add_client().await;
/// # let mut bus_listener = handle.create_bus_listener().await?;
///
/// assert_eq!(bus_listener.num_filters(), 0);
///
/// bus_listener.add_filter(BusListenerFilter::any_object_any_service())?;
/// assert_eq!(bus_listener.num_filters(), 1);
///
/// bus_listener.add_filter(BusListenerFilter::any_object_any_service())?;
/// assert_eq!(bus_listener.num_filters(), 1); // No duplicates
///
/// bus_listener.remove_filter(BusListenerFilter::any_object_any_service())?;
/// assert_eq!(bus_listener.num_filters(), 0);
///
/// # Ok(())
/// # }
/// ```
pub fn num_filters(&self) -> usize {
self.filters.len()
}
/// Starts the bus listener with the given scope.
///
/// Bus listeners can only be started when they are stopped.
pub async fn start(&mut self, scope: BusListenerScope) -> Result<(), Error> {
self.client.start_bus_listener(self.cookie, scope).await?;
self.pending_started += 1;
if scope.includes_current() {
self.pending_current_finished += 1;
}
Ok(())
}
/// Stops the bus listener.
pub async fn stop(&mut self) -> Result<(), Error> {
self.client.stop_bus_listener(self.cookie).await?;
self.pending_stopped += 1;
Ok(())
}
/// Returns the bus listener's active scope, if any.
///
/// The scope returned by this function does not change immediately after calling
/// [`start`](Self::start). It returns the scope that is associated with the events that are
/// currently returned by [`next_event`](Self::next_event) and
/// [`poll_next_event`](Self::poll_next_event).
pub fn scope(&self) -> Option<BusListenerScope> {
self.scope
}
/// Indicates whether the bus listener can return more events.
///
/// This function essentially indicates whether [`next_event`](Self::next_event) and
/// [`poll_next_event`](Self::poll_next_event) can possible return `Some` or not. You should
/// continue to call either function for as long as this function returns `false`.
///
/// Bus listeners can only ever finish if they are stopped or if their scope is
/// [`BusListenerScope::Current`] and all events have been emitted.
pub fn is_finished(&self) -> bool {
self.events.is_terminated()
|| (!self.includes_new()
&& (self.pending_started == 0)
&& (self.pending_stopped == 0)
&& (self.pending_current_finished == 0))
}
/// Polls the bus listener for an event.
pub fn poll_next_event(&mut self, cx: &mut Context) -> Poll<Option<BusEvent>> {
loop {
if self.is_finished() {
break Poll::Ready(None);
}
match Pin::new(&mut self.events).poll_next(cx) {
Poll::Ready(Some(BusListenerEvent::Started(scope))) => {
self.scope = Some(scope);
self.pending_started -= 1;
}
Poll::Ready(Some(BusListenerEvent::Stopped)) => {
self.scope = None;
self.pending_stopped -= 1;
}
Poll::Ready(Some(BusListenerEvent::Event(event))) => {
return Poll::Ready(Some(event))
}
Poll::Ready(Some(BusListenerEvent::CurrentFinished)) => {
self.pending_current_finished -= 1;
}
Poll::Ready(None) => break Poll::Ready(None),
Poll::Pending => break Poll::Pending,
}
}
}
/// Await an event from the bus listener.
pub async fn next_event(&mut self) -> Option<BusEvent> {
future::poll_fn(|cx| self.poll_next_event(cx)).await
}
fn includes_new(&self) -> bool {
self.scope
.map(BusListenerScope::includes_new)
.unwrap_or(false)
}
}
impl Drop for BusListener {
fn drop(&mut self) {
self.client.destroy_bus_listener_now(self.cookie);
}
}
impl Stream for BusListener {
type Item = BusEvent;
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<BusEvent>> {
self.poll_next_event(cx)
}
}
impl FusedStream for BusListener {
fn is_terminated(&self) -> bool {
self.is_finished()
}
}
#[derive(Debug)]
pub(crate) struct BusListenerHandle {
filters: HashSet<BusListenerFilter>,
events: UnboundedSender<BusListenerEvent>,
scope: Option<BusListenerScope>,
current_finished: bool,
}
impl BusListenerHandle {
pub fn new(events: UnboundedSender<BusListenerEvent>) -> Self {
Self {
filters: HashSet::new(),
events,
scope: None,
current_finished: false,
}
}
pub fn add_filter(&mut self, filter: BusListenerFilter) {
self.filters.insert(filter);
}
pub fn remove_filter(&mut self, filter: BusListenerFilter) {
self.filters.remove(&filter);
}
pub fn clear_filters(&mut self) {
self.filters.clear();
}
pub fn start(&mut self, scope: BusListenerScope) -> bool {
if self.scope.is_none() {
self.scope = Some(scope);
self.current_finished = !scope.includes_current();
self.events
.unbounded_send(BusListenerEvent::Started(scope))
.ok();
true
} else {
false
}
}
pub fn stop(&mut self) -> bool {
if self.scope.is_some() {
self.scope = None;
self.events.unbounded_send(BusListenerEvent::Stopped).ok();
true
} else {
false
}
}
pub fn current_finished(&mut self) -> bool {
if !self.current_finished {
self.events
.unbounded_send(BusListenerEvent::CurrentFinished)
.ok();
self.current_finished = true;
true
} else {
false
}
}
pub fn emit_current(&self, event: BusEvent) -> bool {
if self.includes_current() && !self.current_finished {
self.events
.unbounded_send(BusListenerEvent::Event(event))
.ok();
true
} else {
false
}
}
pub fn emit_new_if_matches(&self, event: BusEvent) {
if self.includes_new() && self.matches_filters(event) {
self.events
.unbounded_send(BusListenerEvent::Event(event))
.ok();
}
}
fn includes_current(&self) -> bool {
self.scope
.map(BusListenerScope::includes_current)
.unwrap_or(false)
}
fn includes_new(&self) -> bool {
self.scope
.map(BusListenerScope::includes_new)
.unwrap_or(false)
}
fn matches_filters(&self, event: BusEvent) -> bool {
self.filters
.iter()
.any(|filter| filter.matches_event(event))
}
}
#[derive(Debug)]
pub(crate) enum BusListenerEvent {
Started(BusListenerScope),
Stopped,
Event(BusEvent),
CurrentFinished,
}