fuchsia_async/runtime/fuchsia/executor/
packets.rs

1// Copyright 2021 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5use rustc_hash::FxHashMap as HashMap;
6use std::ops::Deref;
7use std::sync::Arc;
8
9use super::common::EHandle;
10
11/// A trait for handling the arrival of a packet on a `zx::Port`.
12///
13/// This trait should be implemented by users who wish to write their own
14/// types which receive asynchronous notifications from a `zx::Port`.
15/// Implementors of this trait generally contain a `futures::task::AtomicWaker` which
16/// is used to wake up the task which can make progress due to the arrival of
17/// the packet.
18///
19/// `PacketReceiver`s should be registered with a `Core` using the
20/// `register_receiver` method on `Core`, `Handle`, or `Remote`.
21/// Upon registration, users will receive a `ReceiverRegistration`
22/// which provides `key` and `port` methods. These methods can be used to wait on
23/// asynchronous signals.
24///
25/// Note that `PacketReceiver`s may receive false notifications intended for a
26/// previous receiver, and should handle these gracefully.
27pub trait PacketReceiver: Send + Sync + 'static {
28    /// Receive a packet when one arrives.
29    fn receive_packet(&self, packet: zx::Packet);
30}
31
32// Simple slab::Slab replacement that doesn't re-use keys
33// TODO(https://fxbug.dev/42119369): figure out how to safely cancel async waits so we can re-use keys again.
34pub(crate) struct PacketReceiverMap<T> {
35    next_key: u64,
36    pub mapping: HashMap<u64, T>,
37}
38
39impl<T> PacketReceiverMap<T> {
40    pub fn new() -> Self {
41        Self { next_key: 0, mapping: HashMap::default() }
42    }
43
44    pub fn get(&self, key: u64) -> Option<&T> {
45        self.mapping.get(&key)
46    }
47
48    pub fn insert<R>(&mut self, val: impl FnOnce(u64) -> (T, R)) -> R {
49        let key = self.next_key;
50        self.next_key = self.next_key.checked_add(1).expect("ran out of keys");
51        let (val, out) = val(key);
52        self.mapping.insert(key, val);
53        out
54    }
55
56    pub fn remove(&mut self, key: u64) -> T {
57        self.mapping.remove(&key).unwrap_or_else(|| panic!("invalid key"))
58    }
59
60    pub fn contains(&self, key: u64) -> bool {
61        self.mapping.contains_key(&key)
62    }
63}
64
65/// A registration of a `PacketReceiver`.
66/// When dropped, it will automatically deregister the `PacketReceiver`.
67// NOTE: purposefully does not implement `Clone`.
68#[derive(Debug)]
69pub struct ReceiverRegistration<T: PacketReceiver> {
70    pub(super) receiver: Arc<T>,
71    pub(super) ehandle: EHandle,
72    pub(super) key: u64,
73}
74
75impl<T> ReceiverRegistration<T>
76where
77    T: PacketReceiver,
78{
79    /// The key with which `Packet`s destined for this receiver should be sent on the `zx::Port`.
80    pub fn key(&self) -> u64 {
81        self.key
82    }
83
84    /// The internal `PacketReceiver`.
85    pub fn receiver(&self) -> &T {
86        &self.receiver
87    }
88
89    /// The `zx::Port` on which packets destined for this `PacketReceiver` should be queued.
90    pub fn port(&self) -> &zx::Port {
91        self.ehandle.port()
92    }
93}
94
95impl<T: PacketReceiver> Deref for ReceiverRegistration<T> {
96    type Target = T;
97    fn deref(&self) -> &Self::Target {
98        self.receiver()
99    }
100}
101
102impl<T> Drop for ReceiverRegistration<T>
103where
104    T: PacketReceiver,
105{
106    fn drop(&mut self) {
107        self.ehandle.deregister_receiver(self.key);
108    }
109}
110
111#[cfg(test)]
112mod tests {
113    use super::*;
114
115    #[test]
116    fn packet_receiver_map_does_not_reuse_keys() {
117        #[derive(Debug, Copy, Clone, PartialEq)]
118        struct DummyPacketReceiver {
119            id: i32,
120        }
121        let mut map = PacketReceiverMap::<DummyPacketReceiver>::new();
122        let e1 = DummyPacketReceiver { id: 1 };
123        assert_eq!(map.insert(|key| (e1, key)), 0);
124        assert_eq!(map.insert(|key| (e1, key)), 1);
125
126        // Still doesn't reuse IDs after one is removed
127        map.remove(1);
128        assert_eq!(map.insert(|key| (e1, key)), 2);
129    }
130}
fuchsia_async/runtime/fuchsia/executor/packets.rs

fuchsia_async/runtime/fuchsia/executor/
packets.rs
