1 files changed, 122 insertions, 0 deletions
diff --git a/library/std/src/sys/unix/pipe.rs b/library/std/src/sys/unix/pipe.rs
new file mode 100644
index 00000000000..7ae37bdda70
--- /dev/null
+++ b/library/std/src/sys/unix/pipe.rs
@@ -0,0 +1,122 @@
+use crate::io::{self, IoSlice, IoSliceMut};
+use crate::mem;
+use crate::sys::fd::FileDesc;
+use crate::sys::{cvt, cvt_r};
+
+////////////////////////////////////////////////////////////////////////////////
+// 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"
+        ))] {
+            cvt(unsafe { libc::pipe2(fds.as_mut_ptr(), libc::O_CLOEXEC) })?;
+            Ok((AnonPipe(FileDesc::new(fds[0])), AnonPipe(FileDesc::new(fds[1]))))
+        } else {
+            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 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 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()
+    }
+
+    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(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)
+                }
+            }
+        }
+    }
+}