/
pipe.rs
131 lines (115 loc) · 4.59 KB
/
pipe.rs
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
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use io;
use libc::{self, c_int};
use mem;
use sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
use sys::fd::FileDesc;
use sys::{cvt, cvt_r};
////////////////////////////////////////////////////////////////////////////////
// Anonymous pipes
////////////////////////////////////////////////////////////////////////////////
pub struct AnonPipe(FileDesc);
pub fn anon_pipe() -> io::Result<(AnonPipe, AnonPipe)> {
weak! { fn pipe2(*mut c_int, c_int) -> c_int }
static INVALID: AtomicBool = ATOMIC_BOOL_INIT;
let mut fds = [0; 2];
// Unfortunately the only known way right now to create atomically set the
// CLOEXEC flag is to use the `pipe2` syscall on Linux. This was added in
// 2.6.27, however, and because we support 2.6.18 we must detect this
// support dynamically.
if cfg!(any(target_os = "dragonfly",
target_os = "freebsd",
target_os = "linux",
target_os = "netbsd",
target_os = "openbsd")) &&
!INVALID.load(Ordering::SeqCst)
{
if let Some(pipe) = pipe2.get() {
// Note that despite calling a glibc function here we may still
// get ENOSYS. Glibc has `pipe2` since 2.9 and doesn't try to
// emulate on older kernels, so if you happen to be running on
// an older kernel you may see `pipe2` as a symbol but still not
// see the syscall.
match cvt(unsafe { pipe(fds.as_mut_ptr(), libc::O_CLOEXEC) }) {
Ok(_) => {
return Ok((AnonPipe(FileDesc::new(fds[0])),
AnonPipe(FileDesc::new(fds[1]))));
}
Err(ref e) if e.raw_os_error() == Some(libc::ENOSYS) => {
INVALID.store(true, Ordering::SeqCst);
}
Err(e) => return Err(e),
}
}
}
cvt(unsafe { libc::pipe(fds.as_mut_ptr()) })?;
let fd0 = FileDesc::new(fds[0]);
let fd1 = FileDesc::new(fds[1]);
fd0.set_cloexec()?;
fd1.set_cloexec()?;
Ok((AnonPipe(fd0), AnonPipe(fd1)))
}
impl AnonPipe {
pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
self.0.read(buf)
}
pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
self.0.write(buf)
}
pub fn fd(&self) -> &FileDesc { &self.0 }
pub fn into_fd(self) -> FileDesc { self.0 }
}
pub fn read2(p1: AnonPipe,
v1: &mut Vec<u8>,
p2: AnonPipe,
v2: &mut Vec<u8>) -> io::Result<()> {
// Set both pipes into nonblocking mode as we're gonna be reading from both
// in the `select` loop below, and we wouldn't want one to block the other!
let p1 = p1.into_fd();
let p2 = p2.into_fd();
p1.set_nonblocking(true)?;
p2.set_nonblocking(true)?;
let mut fds: [libc::pollfd; 2] = unsafe { mem::zeroed() };
fds[0].fd = p1.raw();
fds[0].events = libc::POLLIN;
fds[1].fd = p2.raw();
fds[1].events = libc::POLLIN;
loop {
// wait for either pipe to become readable using `poll`
cvt_r(|| unsafe { libc::poll(fds.as_mut_ptr(), 2, -1) })?;
if fds[0].revents != 0 && read(&p1, v1)? {
p2.set_nonblocking(false)?;
return p2.read_to_end(v2).map(|_| ());
}
if fds[1].revents != 0 && read(&p2, v2)? {
p1.set_nonblocking(false)?;
return p1.read_to_end(v1).map(|_| ());
}
}
// Read as much as we can from each pipe, ignoring EWOULDBLOCK or
// EAGAIN. If we hit EOF, then this will happen because the underlying
// reader will return Ok(0), in which case we'll see `Ok` ourselves. In
// this case we flip the other fd back into blocking mode and read
// whatever's leftover on that file descriptor.
fn read(fd: &FileDesc, dst: &mut Vec<u8>) -> Result<bool, io::Error> {
match fd.read_to_end(dst) {
Ok(_) => Ok(true),
Err(e) => {
if e.raw_os_error() == Some(libc::EWOULDBLOCK) ||
e.raw_os_error() == Some(libc::EAGAIN) {
Ok(false)
} else {
Err(e)
}
}
}
}
}