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
|
//! Channel that delivers messages periodically.
//!
//! Messages cannot be sent into this kind of channel; they are materialized on demand.
use std::thread;
use std::time::{Duration, Instant};
use crossbeam_utils::atomic::AtomicCell;
use crate::context::Context;
use crate::err::{RecvTimeoutError, TryRecvError};
use crate::select::{Operation, SelectHandle, Token};
use crate::utils;
/// Result of a receive operation.
pub(crate) type TickToken = Option<Instant>;
/// Channel that delivers messages periodically.
pub(crate) struct Channel {
/// The instant at which the next message will be delivered.
delivery_time: AtomicCell<Instant>,
/// The time interval in which messages get delivered.
duration: Duration,
}
impl Channel {
/// Creates a channel that delivers messages periodically.
#[inline]
pub(crate) fn new(dur: Duration) -> Self {
Channel {
delivery_time: AtomicCell::new(utils::convert_timeout_to_deadline(dur)),
duration: dur,
}
}
/// Attempts to receive a message without blocking.
#[inline]
pub(crate) fn try_recv(&self) -> Result<Instant, TryRecvError> {
loop {
let now = Instant::now();
let delivery_time = self.delivery_time.load();
if now < delivery_time {
return Err(TryRecvError::Empty);
}
if self
.delivery_time
.compare_exchange(delivery_time, now + self.duration)
.is_ok()
{
return Ok(delivery_time);
}
}
}
/// Receives a message from the channel.
#[inline]
pub(crate) fn recv(&self, deadline: Option<Instant>) -> Result<Instant, RecvTimeoutError> {
loop {
let delivery_time = self.delivery_time.load();
let now = Instant::now();
if let Some(d) = deadline {
if d < delivery_time {
if now < d {
thread::sleep(d - now);
}
return Err(RecvTimeoutError::Timeout);
}
}
if self
.delivery_time
.compare_exchange(delivery_time, delivery_time.max(now) + self.duration)
.is_ok()
{
if now < delivery_time {
thread::sleep(delivery_time - now);
}
return Ok(delivery_time);
}
}
}
/// Reads a message from the channel.
#[inline]
pub(crate) unsafe fn read(&self, token: &mut Token) -> Result<Instant, ()> {
token.tick.ok_or(())
}
/// Returns `true` if the channel is empty.
#[inline]
pub(crate) fn is_empty(&self) -> bool {
Instant::now() < self.delivery_time.load()
}
/// Returns `true` if the channel is full.
#[inline]
pub(crate) fn is_full(&self) -> bool {
!self.is_empty()
}
/// Returns the number of messages in the channel.
#[inline]
pub(crate) fn len(&self) -> usize {
if self.is_empty() {
0
} else {
1
}
}
/// Returns the capacity of the channel.
#[inline]
pub(crate) fn capacity(&self) -> Option<usize> {
Some(1)
}
}
impl SelectHandle for Channel {
#[inline]
fn try_select(&self, token: &mut Token) -> bool {
match self.try_recv() {
Ok(msg) => {
token.tick = Some(msg);
true
}
Err(TryRecvError::Disconnected) => {
token.tick = None;
true
}
Err(TryRecvError::Empty) => false,
}
}
#[inline]
fn deadline(&self) -> Option<Instant> {
Some(self.delivery_time.load())
}
#[inline]
fn register(&self, _oper: Operation, _cx: &Context) -> bool {
self.is_ready()
}
#[inline]
fn unregister(&self, _oper: Operation) {}
#[inline]
fn accept(&self, token: &mut Token, _cx: &Context) -> bool {
self.try_select(token)
}
#[inline]
fn is_ready(&self) -> bool {
!self.is_empty()
}
#[inline]
fn watch(&self, _oper: Operation, _cx: &Context) -> bool {
self.is_ready()
}
#[inline]
fn unwatch(&self, _oper: Operation) {}
}
|