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
use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
use crate::mem;
use crate::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, RawFd};
use crate::sys::fd::FileDesc;
use crate::sys::{cvt, cvt_r};
use crate::sys_common::IntoInner;

////////////////////////////////////////////////////////////////////////////////
// Anonymous pipes
////////////////////////////////////////////////////////////////////////////////

pub struct AnonPipe(FileDesc);

pub fn anon_pipe() -> io::Result<(AnonPipe, AnonPipe)> {
    let mut fds = [0; 2];

    // The only known way right now to create atomically set the CLOEXEC flag is
    // to use the `pipe2` syscall. This was added to Linux in 2.6.27, glibc 2.9
    // and musl 0.9.3, and some other targets also have it.
    cfg_if::cfg_if! {
        if #[cfg(any(
            target_os = "dragonfly",
            target_os = "freebsd",
            target_os = "linux",
            target_os = "netbsd",
            target_os = "openbsd",
            target_os = "redox"
        ))] {
            unsafe {
                cvt(libc::pipe2(fds.as_mut_ptr(), libc::O_CLOEXEC))?;
                Ok((AnonPipe(FileDesc::from_raw_fd(fds[0])), AnonPipe(FileDesc::from_raw_fd(fds[1]))))
            }
        } else {
            unsafe {
                cvt(libc::pipe(fds.as_mut_ptr()))?;

                let fd0 = FileDesc::from_raw_fd(fds[0]);
                let fd1 = FileDesc::from_raw_fd(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 read_buf(&self, buf: BorrowedCursor<'_>) -> io::Result<()> {
        self.0.read_buf(buf)
    }

    pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
        self.0.read_vectored(bufs)
    }

    #[inline]
    pub fn is_read_vectored(&self) -> bool {
        self.0.is_read_vectored()
    }

    pub fn read_to_end(&self, buf: &mut Vec<u8>) -> io::Result<usize> {
        self.0.read_to_end(buf)
    }

    pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
        self.0.write(buf)
    }

    pub fn write_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
        self.0.write_vectored(bufs)
    }

    #[inline]
    pub fn is_write_vectored(&self) -> bool {
        self.0.is_write_vectored()
    }
}

impl IntoInner<FileDesc> for AnonPipe {
    fn into_inner(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_inner();
    let p2 = p2.into_inner();
    p1.set_nonblocking(true)?;
    p2.set_nonblocking(true)?;

    let mut fds: [libc::pollfd; 2] = unsafe { mem::zeroed() };
    fds[0].fd = p1.as_raw_fd();
    fds[0].events = libc::POLLIN;
    fds[1].fd = p2.as_raw_fd();
    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(drop);
        }
        if fds[1].revents != 0 && read(&p2, v2)? {
            p1.set_nonblocking(false)?;
            return p1.read_to_end(v1).map(drop);
        }
    }

    // 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)
                }
            }
        }
    }
}

impl AsRawFd for AnonPipe {
    #[inline]
    fn as_raw_fd(&self) -> RawFd {
        self.0.as_raw_fd()
    }
}

impl AsFd for AnonPipe {
    fn as_fd(&self) -> BorrowedFd<'_> {
        self.0.as_fd()
    }
}

impl IntoRawFd for AnonPipe {
    fn into_raw_fd(self) -> RawFd {
        self.0.into_raw_fd()
    }
}

impl FromRawFd for AnonPipe {
    unsafe fn from_raw_fd(raw_fd: RawFd) -> Self {
        Self(FromRawFd::from_raw_fd(raw_fd))
    }
}