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// 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)> {
syscall! { fn pipe2(fds: *mut c_int, flags: 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)
{
// 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 { pipe2(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)
}
}
}
}
}
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