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//! An address to an actor is a way to send it a message. An address allows an actor to be sent any
//! kind of message that it can receive.
use std::cmp::Ordering;
use std::fmt::{self, Debug, Formatter};
use std::future::Future;
use std::hash::{Hash, Hasher};
use std::pin::Pin;
use std::task::{Context, Poll};
use event_listener::EventListener;
use futures_util::FutureExt;
use crate::refcount::{Either, RefCounter, Strong, Weak};
use crate::send_future::{ActorNamedBroadcasting, Broadcast, ResolveToHandlerReturn};
use crate::{chan, ActorNamedSending, Handler, SendFuture};
/// An [`Address`] is a reference to an actor through which messages can be sent.
///
/// [`Address`]es can be cloned to obtain more addresses to the same actor.
/// By default (i.e without specifying the second type parameter, `Rc`, to be
/// [`Weak`], [`Address`]es are strong. Therefore, when all [`Address`]es
/// are dropped, the actor will be stopped. In other words, any existing [`Address`]es will inhibit
/// the dropping of an actor. If this is undesirable, then a [`WeakAddress`]
/// should be used instead.
///
/// The initial [`Address`] of an actor is returned when you construct a new [`Mailbox`](crate::Mailbox).
///
/// ## Mailboxes
///
/// Internally, a mailbox has three, more specific mailboxes, each for a specific kind of message:
/// 1. The default priority, or ordered mailbox.
/// 2. The priority mailbox.
/// 3. The broadcast mailbox.
///
/// The first two mailboxes are shared between all actors on the same address, whilst each actor
/// has its own broadcast mailbox.
///
/// The actor's mailbox capacity applies severally to each mailbox. This means that an actor can
/// have a total of `cap` messages in every mailbox before it is totally full. However, it must only
/// have `cap` in a given mailbox for any sends to that mailbox to be caused to wait for free space
/// and thus exercise backpressure on senders.
///
/// ### Default priority
///
/// The default priority mailbox contains messages which will be handled in order of sending. This is
/// a special property, as the other two mailboxes do not preserve send order!
/// The vast majority of actor messages will probably be sent to this mailbox. They have default
/// priority - a message will be taken from this mailbox next only if the other two mailboxes are empty.
///
/// ### Priority
///
/// The priority mailbox contains messages which will be handled in order of their priority.This
/// can be used to make sure that critical maintenance tasks such as pings are handled as soon as
/// possible. Keep in mind that if this becomes full, attempting to send in a higher priority message
/// than the current highest will still result in waiting for at least one priority message
/// to be handled.
///
/// ### Broadcast
///
/// The broadcast mailbox contains messages which will be handled by every single actor, in order
/// of their priority. All actors must handle a message for it to be removed from the mailbox and
/// the length to decrease. This means that the backpressure provided by [`Address::broadcast`] will
/// wait for the slowest actor.
pub struct Address<A, Rc: RefCounter = Strong>(pub(crate) chan::Ptr<A, Rc>);
impl<A, Rc: RefCounter> Debug for Address<A, Rc> {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
let actor_type = std::any::type_name::<A>();
let rc_type = std::any::type_name::<Rc>()
.replace("xtra::chan::ptr::", "")
.replace("Tx", "");
f.debug_struct(&format!("Address<{}, {}>", actor_type, rc_type))
.field("addresses", &self.0.sender_count())
.field("mailboxes", &self.0.receiver_count())
.finish()
}
}
/// A [`WeakAddress`] is a reference to an actor through which messages can be
/// sent. It can be cloned. Unlike [`Address`], a [`WeakAddress`] will not inhibit
/// the dropping of an actor. It is created by the [`Address::downgrade`]
/// method.
pub type WeakAddress<A> = Address<A, Weak>;
impl<A> WeakAddress<A> {
/// Try to upgrade this [`WeakAddress`] to a strong one.
///
/// This will yield `None` if there are no more other strong addresses around.
pub fn try_upgrade(&self) -> Option<Address<A>> {
Some(Address(self.0.try_to_tx_strong()?))
}
}
/// Functions which apply only to strong addresses (the default kind).
impl<A> Address<A, Strong> {
/// Create a weak address to the actor. Unlike with the strong variety of address (this kind),
/// an actor will not be prevented from being dropped if only weak sinks, channels, and
/// addresses exist.
pub fn downgrade(&self) -> WeakAddress<A> {
Address(self.0.to_tx_weak())
}
}
/// Functions which apply only to addresses which can either be strong or weak.
impl<A> Address<A, Either> {
/// Converts this address into a weak address.
pub fn downgrade(&self) -> WeakAddress<A> {
Address(self.0.to_tx_weak())
}
}
/// Functions which apply to any kind of address, be they strong or weak.
impl<A, Rc> Address<A, Rc>
where
Rc: RefCounter + Into<Either>,
{
/// Convert this address into a generic address which can be weak or strong.
pub fn as_either(&self) -> Address<A, Either> {
Address(self.0.to_tx_either())
}
}
/// Functions which apply to any kind of address, be they strong or weak.
impl<A, Rc: RefCounter> Address<A, Rc> {
/// Returns whether the actors referred to by this address are running and accepting messages.
///
/// ```rust
/// # use xtra::prelude::*;
/// # use std::time::Duration;
/// # struct MyActor;
/// # impl Actor for MyActor {type Stop = (); async fn stopped(self) -> Self::Stop {} }
/// struct Shutdown;
///
///
/// impl Handler<Shutdown> for MyActor {
/// type Return = ();
///
/// async fn handle(&mut self, _: Shutdown, ctx: &mut Context<Self>) {
/// ctx.stop_all();
/// }
/// }
///
/// # #[cfg(feature = "smol")]
/// smol::block_on(async {
/// let addr = xtra::spawn_smol(MyActor, Mailbox::unbounded());
/// assert!(addr.is_connected());
/// addr.send(Shutdown).await;
/// smol::Timer::after(Duration::from_secs(1)).await; // Give it time to shut down
/// assert!(!addr.is_connected());
/// })
/// ```
pub fn is_connected(&self) -> bool {
self.0.is_connected()
}
/// Returns the number of messages in the actor's mailbox. This will be the sum of broadcast
/// messages, priority messages, and ordered messages. It can be up to three times the capacity,
/// as the capacity is for each send type (broadcast, priority, and ordered).
pub fn len(&self) -> usize {
self.0.len()
}
/// The capacity of the actor's mailbox per send type (broadcast, priority, and ordered).
pub fn capacity(&self) -> Option<usize> {
self.0.capacity()
}
/// Returns whether the actor's mailbox is empty.
pub fn is_empty(&self) -> bool {
self.len() == 0
}
/// Send a message to the actor. The message will, by default, have a priority of 0 and be sent
/// into the ordered queue. This can be configured through [`SendFuture::priority`].
///
/// The actor must implement [`Handler<Message>`] for this to work.
///
/// This function returns a [`Future`](SendFuture) that resolves to the [`Return`](crate::Handler::Return) value of the handler.
/// The [`SendFuture`] will resolve to [`Err(Disconnected)`] in case the actor is stopped and not accepting messages.
#[allow(clippy::type_complexity)]
pub fn send<M>(
&self,
message: M,
) -> SendFuture<ActorNamedSending<A, Rc>, ResolveToHandlerReturn<<A as Handler<M>>::Return>>
where
M: Send + 'static,
A: Handler<M>,
{
SendFuture::sending_named(message, self.0.clone())
}
/// Send a message to all actors on this address. The message will, by default, have a priority
/// of 0. This can be configured through [`SendFuture::priority`].
///
/// The actor must implement [`Handler<Message>`] for this to work where [`Handler::Return`] is
/// set to `()`.
pub fn broadcast<M>(&self, msg: M) -> SendFuture<ActorNamedBroadcasting<A, Rc>, Broadcast>
where
M: Clone + Send + Sync + 'static,
A: Handler<M, Return = ()>,
{
SendFuture::broadcast_named(msg, self.0.clone())
}
/// Waits until this address becomes disconnected. Note that if this is called on a strong
/// address, it will only ever trigger if the actor calls [`Context::stop_self`](crate::Context::stop_self),
/// as the address would prevent the actor being dropped due to too few strong addresses.
pub fn join(&self) -> ActorJoinHandle {
ActorJoinHandle(self.0.disconnect_listener())
}
/// Returns true if this address and the other address point to the same actor. This is
/// distinct from the implementation of `PartialEq` as it ignores reference count type, which
/// must be the same for `PartialEq` to return `true`.
pub fn same_actor<Rc2: RefCounter>(&self, other: &Address<A, Rc2>) -> bool {
self.0.inner_ptr() == other.0.inner_ptr()
}
/// Converts this address into a sink that can be used to send messages to the actor. These
/// messages will have default priority and will be handled in send order.
///
/// When converting an [`Address`] into a [`Sink`], it is important to think about the address'
/// reference counts. By default [`Address`]es are [`Strong`]. The [`Sink`] wraps the [`Address`]
/// for its entire lifetime and will thus inherit the reference count type.
///
/// If you are going to use [`Address::into_sink`] in combination with things like
/// [`Stream::forward`](futures_util::stream::StreamExt::forward), bear in mind that a
/// strong [`Address`] will keep the actor alive for as long as that
/// [`Stream`](futures_util::stream::Stream) is being polled. Depending on your usecase, you
/// may want to use a [`WeakAddress`] instead.
///
/// Because [`Sink`]s do not return anything, this function is only available for messages with
/// a [`Handler`] implementation that sets [`Return`](Handler::Return) to `()`.
///
/// [`Sink`]: futures_sink::Sink
#[cfg(feature = "sink")]
pub fn into_sink<M>(self) -> impl futures_sink::Sink<M, Error = crate::Error>
where
A: Handler<M, Return = ()>,
M: Send + 'static,
{
futures_util::sink::unfold((), move |(), message| self.send(message))
}
}
/// A future which will complete when the corresponding actor stops and its address becomes
/// disconnected.
#[must_use = "Futures do nothing unless polled"]
pub struct ActorJoinHandle(Option<EventListener>);
impl Future for ActorJoinHandle {
type Output = ();
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
match self.0.take() {
Some(mut listener) => match listener.poll_unpin(cx) {
Poll::Ready(()) => Poll::Ready(()),
Poll::Pending => {
self.0 = Some(listener);
Poll::Pending
}
},
None => Poll::Ready(()),
}
}
}
// Required because #[derive] adds an A: Clone bound
impl<A, Rc: RefCounter> Clone for Address<A, Rc> {
fn clone(&self) -> Self {
Address(self.0.clone())
}
}
/// Determines whether this and the other address point to the same actor mailbox **and**
/// they have reference count type equality. This means that this will only return true if
/// [`Address::same_actor`] returns true **and** if they both have weak or strong reference
/// counts. [`Either`](crate::refcount::Either) will compare as whichever reference count type
/// it wraps.
impl<A, Rc: RefCounter, Rc2: RefCounter> PartialEq<Address<A, Rc2>> for Address<A, Rc> {
fn eq(&self, other: &Address<A, Rc2>) -> bool {
(self.same_actor(other)) && (self.0.is_strong() == other.0.is_strong())
}
}
impl<A, Rc: RefCounter> Eq for Address<A, Rc> {}
/// Compare this address to another. This comparison has little semantic meaning, and is intended
/// to be used for comparison-based indexing only (e.g to allow addresses to be keys in binary search
/// trees). The pointer of the actors' mailboxes will be compared, and if they are equal, a strong
/// address will compare as greater than a weak one.
impl<A, Rc: RefCounter, Rc2: RefCounter> PartialOrd<Address<A, Rc2>> for Address<A, Rc> {
fn partial_cmp(&self, other: &Address<A, Rc2>) -> Option<Ordering> {
Some(match self.0.inner_ptr().cmp(&other.0.inner_ptr()) {
Ordering::Equal => self.0.is_strong().cmp(&other.0.is_strong()),
ord => ord,
})
}
}
impl<A, Rc: RefCounter> Ord for Address<A, Rc> {
fn cmp(&self, other: &Self) -> Ordering {
self.0.inner_ptr().cmp(&other.0.inner_ptr())
}
}
impl<A, Rc: RefCounter> Hash for Address<A, Rc> {
fn hash<H: Hasher>(&self, state: &mut H) {
state.write_usize(self.0.inner_ptr() as *const _ as usize);
state.write_u8(self.0.is_strong() as u8);
state.finish();
}
}