1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
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))
}
}