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
use std::os::unix::io::{RawFd, AsRawFd};
use std::{slice, mem};
use libc::{c_uint};
use nix;
use nix::unistd;
use nix::sys::eventfd;
use nix::errno::Errno;
use Result;
const EFD_VAL_SIZE: usize = mem::size_of::<u64>();
pub type EfdFlags = eventfd::EfdFlags;
pub struct EventFd {
fd: RawFd,
}
impl EventFd {
pub fn new(initval: c_uint, flags: EfdFlags) -> Result<EventFd> {
let fd = eventfd::eventfd(initval, flags)?;
Ok(EventFd { fd })
}
pub fn read(&self) -> Result<u64> {
let mut buf: [u8; 8] = [0; EFD_VAL_SIZE];
if unistd::read(self.fd, &mut buf)? != EFD_VAL_SIZE {
return Err(nix::Error::Sys(Errno::EIO));
}
let val: u64 = unsafe {
*(&buf as *const u8 as *const u64)
};
Ok(val)
}
pub fn write(&self, val: u64) -> Result<()> {
let buf = unsafe {
slice::from_raw_parts(&val as *const u64 as *const u8,
EFD_VAL_SIZE)
};
if unistd::write(self.fd, &buf)? != EFD_VAL_SIZE {
return Err(nix::Error::Sys(Errno::EIO));
}
Ok(())
}
}
impl AsRawFd for EventFd {
fn as_raw_fd(&self) -> RawFd {
self.fd
}
}
impl Drop for EventFd {
fn drop(&mut self) {
let _ = unistd::close(self.fd);
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::os::unix::io::AsRawFd;
use nix::Error;
#[test]
fn test_normal() {
let evtfd = EventFd::new(0, EfdFlags::empty()).unwrap();
assert!(evtfd.as_raw_fd() >= 0);
evtfd.write(1).unwrap();
let n = evtfd.read().unwrap();
assert_eq!(1, n);
evtfd.write(42).unwrap();
let n = evtfd.read().unwrap();
assert_eq!(42, n);
}
#[test]
fn test_non_blocking() {
let evtfd = EventFd::new(0, EfdFlags::EFD_NONBLOCK).unwrap();
assert!(evtfd.as_raw_fd() >= 0);
match evtfd.read() {
Ok(_) => assert!(false),
Err(err) => assert_eq!(Error::Sys(Errno::EAGAIN), err),
}
evtfd.write(1).unwrap();
let n = evtfd.read().unwrap();
assert_eq!(1, n);
match evtfd.read() {
Ok(_) => assert!(false),
Err(err) => assert_eq!(Error::Sys(Errno::EAGAIN), err),
}
evtfd.write(42).unwrap();
let n = evtfd.read().unwrap();
assert_eq!(42, n);
}
#[test]
fn test_semaphore() {
let evtfd = EventFd::new(0, EfdFlags::EFD_SEMAPHORE).unwrap();
assert!(evtfd.as_raw_fd() >= 0);
evtfd.write(1).unwrap();
let n = evtfd.read().unwrap();
assert_eq!(1, n);
evtfd.write(2).unwrap();
let n = evtfd.read().unwrap();
assert_eq!(1, n);
let n = evtfd.read().unwrap();
assert_eq!(1, n);
}
#[test]
fn test_semaphore_non_blocking() {
let evtfd = EventFd::new(0, EfdFlags::EFD_SEMAPHORE | EfdFlags::EFD_NONBLOCK).unwrap();
assert!(evtfd.as_raw_fd() >= 0);
evtfd.write(2).unwrap();
let n = evtfd.read().unwrap();
assert_eq!(1, n);
let n = evtfd.read().unwrap();
assert_eq!(1, n);
match evtfd.read() {
Ok(_) => assert!(false),
Err(err) => assert_eq!(Error::Sys(Errno::EAGAIN), err),
}
}
}