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use std::sync::Arc;
use std::sync::atomic::{AtomicU64, Ordering};
use std::time::Duration;
use crate::error::{Error, Result};
use crate::link::Link;
use crate::link::catch::{FilterSet, collapse};
use crate::types::{CatchEvent, CatchFilter};
use super::Device;
/// A live stream of [`CatchEvent`]s from the box (the `CATCH` feature, §3.9).
///
/// Unsubscribes when the last clone drops. For decoded press and release edges rather than held-usage
/// snapshots, use [`Device::input_events`].
#[derive(Clone, Debug)]
pub struct EventStream {
rx: flume::Receiver<CatchEvent>,
dropped: Arc<AtomicU64>,
// Reference-counted so a clone keeps the subscription alive.
_guard: Arc<CatchGuard>,
}
#[derive(Debug)]
struct CatchGuard {
link: Link,
id: u64,
}
impl Drop for CatchGuard {
fn drop(&mut self) {
self.link.catch_unsubscribe(self.id);
}
}
impl EventStream {
pub(crate) fn new(
rx: flume::Receiver<CatchEvent>,
dropped: Arc<AtomicU64>,
link: Link,
id: u64,
) -> EventStream {
EventStream {
rx,
dropped,
_guard: Arc::new(CatchGuard { link, id }),
}
}
/// Block until the next event arrives.
pub fn recv(&self) -> Result<CatchEvent> {
self.rx.recv().map_err(|_| Error::Disconnected)
}
/// The next buffered event, or `None` if none is queued (never blocks).
pub fn try_recv(&self) -> Option<CatchEvent> {
self.rx.try_recv().ok()
}
/// Block up to `timeout` for the next event; `None` on timeout (or a closed channel).
///
/// A closed stream returns at once rather than waiting, so a poll loop that ignores
/// [`Self::is_connected`] spins once the box goes away.
pub fn recv_timeout(&self, timeout: Duration) -> Option<CatchEvent> {
self.rx.recv_timeout(timeout).ok()
}
/// A blocking iterator over the stream, ending when the box disconnects.
pub fn iter(&self) -> impl Iterator<Item = CatchEvent> + '_ {
self.rx.iter()
}
/// Drain every currently-buffered event without blocking.
pub fn try_iter(&self) -> impl Iterator<Item = CatchEvent> + '_ {
self.rx.try_iter()
}
/// Await the next event; runtime-agnostic, runs under any executor.
#[cfg(feature = "async")]
pub async fn recv_async(&self) -> Result<CatchEvent> {
self.rx.recv_async().await.map_err(|_| Error::Disconnected)
}
/// The stream as a [`Stream`](futures_core::Stream), for `.next().await` and the combinators.
#[cfg(feature = "async")]
pub fn stream(&self) -> impl futures_core::Stream<Item = CatchEvent> + '_ {
self.rx.stream()
}
/// Events this stream dropped because the consumer fell behind (host-side back-pressure).
pub fn dropped(&self) -> u64 {
self.dropped.load(Ordering::Relaxed)
}
/// Whether the box is still delivering to this stream.
///
/// [`Self::recv_timeout`] and [`Self::try_recv`] both answer `None` for "nothing yet" and for
/// "nothing ever again", which are different situations: one means wait longer, the other means
/// stop. This separates them.
pub fn is_connected(&self) -> bool {
!self.rx.is_disconnected()
}
}
impl Iterator for EventStream {
type Item = CatchEvent;
fn next(&mut self) -> Option<CatchEvent> {
self.recv().ok()
}
}
impl<'a> IntoIterator for &'a EventStream {
type Item = CatchEvent;
type IntoIter = Box<dyn Iterator<Item = CatchEvent> + 'a>;
fn into_iter(self) -> Self::IntoIter {
Box::new(self.iter())
}
}
/// Check a subscription and collapse it onto one entry per box table slot.
pub(crate) fn prepare(filters: impl IntoIterator<Item = CatchFilter>) -> Result<FilterSet> {
let wanted: Vec<CatchFilter> = filters.into_iter().collect();
// An empty subscription is a stream that never yields, which reads as a dead box rather than as
// the mistake it is.
if wanted.is_empty() {
return Err(Error::EmptySubscription);
}
// WITH/AGAINST are resolved against the injection in flight when a report is weighed. A
// subscription is addressed long before any of that, so a relative direction here has nothing to
// resolve against and the box would drop the entry silently.
if let Some(f) = wanted.iter().find(|f| f.direction().is_relative()) {
return Err(Error::RelativeDirection {
direction: f.direction(),
what: "catch subscription",
});
}
if let Some(f) = wanted.iter().find(|f| !f.capture_is_meaningful()) {
return Err(Error::CaptureNotApplicable {
class: f.class().expect("a meaningless capture names a class"),
});
}
// 0xFFFF is the every-id sentinel, so an exact subscription to it becomes the class blanket the
// moment it reaches the wire -- a much wider stream than the caller asked for, and silent. Only a
// media usage is wide enough to express it.
if let Some((class, id)) = wanted.iter().find_map(|f| {
let (_, id) = f.wire();
(f.id() == Some(id)).then(|| (f.class(), id))
}) && id == crate::protocol::opcode::CATCH_ID_ANY
{
return Err(Error::ReservedId {
class: class.expect("an exact id names a class"),
id,
});
}
Ok(collapse(wanted))
}
impl Device {
/// Subscribe to the catch stream for the given filters (the `CATCH` feature, §3.9).
///
/// Overlapping subscriptions from different callers collapse into the one table the box holds,
/// and each consumer still receives only what it asked for.
///
/// ```no_run
/// # use medius::{Capture, CatchFilter, Device, TrafficClass};
/// # fn f(dev: &Device) -> medius::Result<()> {
/// let events = dev.catch_events([
/// CatchFilter::everything().with_capture(Capture::First(16)),
/// CatchFilter::traffic(TrafficClass::VendorBulk, 0x83),
/// ])?;
/// # Ok(()) }
/// ```
///
/// # Errors
///
/// [`Error::EmptySubscription`] for no filters, [`Error::CaptureNotApplicable`] for a
/// [`Capture`](crate::Capture) on an input class, [`Error::RelativeDirection`] for a filter
/// addressed [`With`](crate::Direction::With) or [`Against`](crate::Direction::Against), and
/// [`Error::CatchTableFull`] when the union with every other subscription in this process
/// exceeds the box's table.
pub fn catch_events(
&self,
filters: impl IntoIterator<Item = CatchFilter>,
) -> Result<EventStream> {
let (id, rx, dropped) = self.link.catch_subscribe(prepare(filters)?)?;
Ok(EventStream::new(rx, dropped, self.link.clone(), id))
}
}