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
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
//! Unix pipe.
//!
//! See the [`new`] function for documentation.

use std::fs::File;
use std::io::{self, IoSlice, IoSliceMut, Read, Write};
use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
use std::process::{ChildStderr, ChildStdin, ChildStdout};

use crate::io_source::IoSource;
use crate::{event, Interest, Registry, Token};

/// Create a new non-blocking Unix pipe.
///
/// This is a wrapper around Unix's [`pipe(2)`] system call and can be used as
/// inter-process or thread communication channel.
///
/// This channel may be created before forking the process and then one end used
/// in each process, e.g. the parent process has the sending end to send command
/// to the child process.
///
/// [`pipe(2)`]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/pipe.html
///
/// # Events
///
/// The [`Sender`] can be registered with [`WRITABLE`] interest to receive
/// [writable events], the [`Receiver`] with [`READABLE`] interest. Once data is
/// written to the `Sender` the `Receiver` will receive an [readable event].
///
/// In addition to those events, events will also be generated if the other side
/// is dropped. To check if the `Sender` is dropped you'll need to check
/// [`is_read_closed`] on events for the `Receiver`, if it returns true the
/// `Sender` is dropped. On the `Sender` end check [`is_write_closed`], if it
/// returns true the `Receiver` was dropped. Also see the second example below.
///
/// [`WRITABLE`]: Interest::WRITABLE
/// [writable events]: event::Event::is_writable
/// [`READABLE`]: Interest::READABLE
/// [readable event]: event::Event::is_readable
/// [`is_read_closed`]: event::Event::is_read_closed
/// [`is_write_closed`]: event::Event::is_write_closed
///
/// # Deregistering
///
/// Both `Sender` and `Receiver` will deregister themselves when dropped,
/// **iff** the file descriptors are not duplicated (via [`dup(2)`]).
///
/// [`dup(2)`]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/dup.html
///
/// # Examples
///
/// Simple example that writes data into the sending end and read it from the
/// receiving end.
///
/// ```
/// use std::io::{self, Read, Write};
///
/// use mio::{Poll, Events, Interest, Token};
/// use mio::unix::pipe;
///
/// // Unique tokens for the two ends of the channel.
/// const PIPE_RECV: Token = Token(0);
/// const PIPE_SEND: Token = Token(1);
///
/// # fn main() -> io::Result<()> {
/// // Create our `Poll` instance and the `Events` container.
/// let mut poll = Poll::new()?;
/// let mut events = Events::with_capacity(8);
///
/// // Create a new pipe.
/// let (mut sender, mut receiver) = pipe::new()?;
///
/// // Register both ends of the channel.
/// poll.registry().register(&mut receiver, PIPE_RECV, Interest::READABLE)?;
/// poll.registry().register(&mut sender, PIPE_SEND, Interest::WRITABLE)?;
///
/// const MSG: &[u8; 11] = b"Hello world";
///
/// loop {
///     poll.poll(&mut events, None)?;
///
///     for event in events.iter() {
///         match event.token() {
///             PIPE_SEND => sender.write(MSG)
///                 .and_then(|n| if n != MSG.len() {
///                         // We'll consider a short write an error in this
///                         // example. NOTE: we can't use `write_all` with
///                         // non-blocking I/O.
///                         Err(io::ErrorKind::WriteZero.into())
///                     } else {
///                         Ok(())
///                     })?,
///             PIPE_RECV => {
///                 let mut buf = [0; 11];
///                 let n = receiver.read(&mut buf)?;
///                 println!("received: {:?}", &buf[0..n]);
///                 assert_eq!(n, MSG.len());
///                 assert_eq!(&buf, &*MSG);
///                 return Ok(());
///             },
///             _ => unreachable!(),
///         }
///     }
/// }
/// # }
/// ```
///
/// Example that receives an event once the `Sender` is dropped.
///
/// ```
/// # use std::io;
/// #
/// # use mio::{Poll, Events, Interest, Token};
/// # use mio::unix::pipe;
/// #
/// # const PIPE_RECV: Token = Token(0);
/// # const PIPE_SEND: Token = Token(1);
/// #
/// # fn main() -> io::Result<()> {
/// // Same setup as in the example above.
/// let mut poll = Poll::new()?;
/// let mut events = Events::with_capacity(8);
///
/// let (mut sender, mut receiver) = pipe::new()?;
///
/// poll.registry().register(&mut receiver, PIPE_RECV, Interest::READABLE)?;
/// poll.registry().register(&mut sender, PIPE_SEND, Interest::WRITABLE)?;
///
/// // Drop the sender.
/// drop(sender);
///
/// poll.poll(&mut events, None)?;
///
/// for event in events.iter() {
///     match event.token() {
///         PIPE_RECV if event.is_read_closed() => {
///             // Detected that the sender was dropped.
///             println!("Sender dropped!");
///             return Ok(());
///         },
///         _ => unreachable!(),
///     }
/// }
/// # unreachable!();
/// # }
/// ```
pub fn new() -> io::Result<(Sender, Receiver)> {
    let mut fds: [RawFd; 2] = [-1, -1];

    #[cfg(any(
        target_os = "android",
        target_os = "dragonfly",
        target_os = "freebsd",
        target_os = "linux",
        target_os = "netbsd",
        target_os = "openbsd",
        target_os = "illumos",
        target_os = "redox",
    ))]
    unsafe {
        if libc::pipe2(fds.as_mut_ptr(), libc::O_CLOEXEC | libc::O_NONBLOCK) != 0 {
            return Err(io::Error::last_os_error());
        }
    }

    #[cfg(any(
        target_os = "ios",
        target_os = "macos",
        target_os = "tvos",
        target_os = "watchos",
    ))]
    unsafe {
        // For platforms that don't have `pipe2(2)` we need to manually set the
        // correct flags on the file descriptor.
        if libc::pipe(fds.as_mut_ptr()) != 0 {
            return Err(io::Error::last_os_error());
        }

        for fd in &fds {
            if libc::fcntl(*fd, libc::F_SETFL, libc::O_NONBLOCK) != 0
                || libc::fcntl(*fd, libc::F_SETFD, libc::FD_CLOEXEC) != 0
            {
                let err = io::Error::last_os_error();
                // Don't leak file descriptors. Can't handle closing error though.
                let _ = libc::close(fds[0]);
                let _ = libc::close(fds[1]);
                return Err(err);
            }
        }
    }

    #[cfg(not(any(
        target_os = "android",
        target_os = "dragonfly",
        target_os = "freebsd",
        target_os = "illumos",
        target_os = "ios",
        target_os = "linux",
        target_os = "macos",
        target_os = "netbsd",
        target_os = "openbsd",
        target_os = "redox",
        target_os = "tvos",
        target_os = "watchos",
    )))]
    compile_error!("unsupported target for `mio::unix::pipe`");

    // SAFETY: we just initialised the `fds` above.
    let r = unsafe { Receiver::from_raw_fd(fds[0]) };
    let w = unsafe { Sender::from_raw_fd(fds[1]) };

    Ok((w, r))
}

/// Sending end of an Unix pipe.
///
/// See [`new`] for documentation, including examples.
#[derive(Debug)]
pub struct Sender {
    inner: IoSource<File>,
}

impl Sender {
    /// Set the `Sender` into or out of non-blocking mode.
    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
        set_nonblocking(self.inner.as_raw_fd(), nonblocking)
    }

    /// Execute an I/O operation ensuring that the socket receives more events
    /// if it hits a [`WouldBlock`] error.
    ///
    /// # Notes
    ///
    /// This method is required to be called for **all** I/O operations to
    /// ensure the user will receive events once the socket is ready again after
    /// returning a [`WouldBlock`] error.
    ///
    /// [`WouldBlock`]: io::ErrorKind::WouldBlock
    ///
    /// # Examples
    ///
    /// ```
    /// # use std::error::Error;
    /// #
    /// # fn main() -> Result<(), Box<dyn Error>> {
    /// use std::io;
    /// use std::os::unix::io::AsRawFd;
    /// use mio::unix::pipe;
    ///
    /// let (sender, receiver) = pipe::new()?;
    ///
    /// // Wait until the sender is writable...
    ///
    /// // Write to the sender using a direct libc call, of course the
    /// // `io::Write` implementation would be easier to use.
    /// let buf = b"hello";
    /// let n = sender.try_io(|| {
    ///     let buf_ptr = &buf as *const _ as *const _;
    ///     let res = unsafe { libc::write(sender.as_raw_fd(), buf_ptr, buf.len()) };
    ///     if res != -1 {
    ///         Ok(res as usize)
    ///     } else {
    ///         // If EAGAIN or EWOULDBLOCK is set by libc::write, the closure
    ///         // should return `WouldBlock` error.
    ///         Err(io::Error::last_os_error())
    ///     }
    /// })?;
    /// eprintln!("write {} bytes", n);
    ///
    /// // Wait until the receiver is readable...
    ///
    /// // Read from the receiver using a direct libc call, of course the
    /// // `io::Read` implementation would be easier to use.
    /// let mut buf = [0; 512];
    /// let n = receiver.try_io(|| {
    ///     let buf_ptr = &mut buf as *mut _ as *mut _;
    ///     let res = unsafe { libc::read(receiver.as_raw_fd(), buf_ptr, buf.len()) };
    ///     if res != -1 {
    ///         Ok(res as usize)
    ///     } else {
    ///         // If EAGAIN or EWOULDBLOCK is set by libc::read, the closure
    ///         // should return `WouldBlock` error.
    ///         Err(io::Error::last_os_error())
    ///     }
    /// })?;
    /// eprintln!("read {} bytes", n);
    /// # Ok(())
    /// # }
    /// ```
    pub fn try_io<F, T>(&self, f: F) -> io::Result<T>
    where
        F: FnOnce() -> io::Result<T>,
    {
        self.inner.do_io(|_| f())
    }
}

impl event::Source for Sender {
    fn register(
        &mut self,
        registry: &Registry,
        token: Token,
        interests: Interest,
    ) -> io::Result<()> {
        self.inner.register(registry, token, interests)
    }

    fn reregister(
        &mut self,
        registry: &Registry,
        token: Token,
        interests: Interest,
    ) -> io::Result<()> {
        self.inner.reregister(registry, token, interests)
    }

    fn deregister(&mut self, registry: &Registry) -> io::Result<()> {
        self.inner.deregister(registry)
    }
}

impl Write for Sender {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.inner.do_io(|mut sender| sender.write(buf))
    }

    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
        self.inner.do_io(|mut sender| sender.write_vectored(bufs))
    }

    fn flush(&mut self) -> io::Result<()> {
        self.inner.do_io(|mut sender| sender.flush())
    }
}

impl Write for &Sender {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.inner.do_io(|mut sender| sender.write(buf))
    }

    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
        self.inner.do_io(|mut sender| sender.write_vectored(bufs))
    }

    fn flush(&mut self) -> io::Result<()> {
        self.inner.do_io(|mut sender| sender.flush())
    }
}

/// # Notes
///
/// The underlying pipe is **not** set to non-blocking.
impl From<ChildStdin> for Sender {
    fn from(stdin: ChildStdin) -> Sender {
        // Safety: `ChildStdin` is guaranteed to be a valid file descriptor.
        unsafe { Sender::from_raw_fd(stdin.into_raw_fd()) }
    }
}

impl FromRawFd for Sender {
    unsafe fn from_raw_fd(fd: RawFd) -> Sender {
        Sender {
            inner: IoSource::new(File::from_raw_fd(fd)),
        }
    }
}

impl AsRawFd for Sender {
    fn as_raw_fd(&self) -> RawFd {
        self.inner.as_raw_fd()
    }
}

impl IntoRawFd for Sender {
    fn into_raw_fd(self) -> RawFd {
        self.inner.into_inner().into_raw_fd()
    }
}

/// Receiving end of an Unix pipe.
///
/// See [`new`] for documentation, including examples.
#[derive(Debug)]
pub struct Receiver {
    inner: IoSource<File>,
}

impl Receiver {
    /// Set the `Receiver` into or out of non-blocking mode.
    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
        set_nonblocking(self.inner.as_raw_fd(), nonblocking)
    }

    /// Execute an I/O operation ensuring that the socket receives more events
    /// if it hits a [`WouldBlock`] error.
    ///
    /// # Notes
    ///
    /// This method is required to be called for **all** I/O operations to
    /// ensure the user will receive events once the socket is ready again after
    /// returning a [`WouldBlock`] error.
    ///
    /// [`WouldBlock`]: io::ErrorKind::WouldBlock
    ///
    /// # Examples
    ///
    /// ```
    /// # use std::error::Error;
    /// #
    /// # fn main() -> Result<(), Box<dyn Error>> {
    /// use std::io;
    /// use std::os::unix::io::AsRawFd;
    /// use mio::unix::pipe;
    ///
    /// let (sender, receiver) = pipe::new()?;
    ///
    /// // Wait until the sender is writable...
    ///
    /// // Write to the sender using a direct libc call, of course the
    /// // `io::Write` implementation would be easier to use.
    /// let buf = b"hello";
    /// let n = sender.try_io(|| {
    ///     let buf_ptr = &buf as *const _ as *const _;
    ///     let res = unsafe { libc::write(sender.as_raw_fd(), buf_ptr, buf.len()) };
    ///     if res != -1 {
    ///         Ok(res as usize)
    ///     } else {
    ///         // If EAGAIN or EWOULDBLOCK is set by libc::write, the closure
    ///         // should return `WouldBlock` error.
    ///         Err(io::Error::last_os_error())
    ///     }
    /// })?;
    /// eprintln!("write {} bytes", n);
    ///
    /// // Wait until the receiver is readable...
    ///
    /// // Read from the receiver using a direct libc call, of course the
    /// // `io::Read` implementation would be easier to use.
    /// let mut buf = [0; 512];
    /// let n = receiver.try_io(|| {
    ///     let buf_ptr = &mut buf as *mut _ as *mut _;
    ///     let res = unsafe { libc::read(receiver.as_raw_fd(), buf_ptr, buf.len()) };
    ///     if res != -1 {
    ///         Ok(res as usize)
    ///     } else {
    ///         // If EAGAIN or EWOULDBLOCK is set by libc::read, the closure
    ///         // should return `WouldBlock` error.
    ///         Err(io::Error::last_os_error())
    ///     }
    /// })?;
    /// eprintln!("read {} bytes", n);
    /// # Ok(())
    /// # }
    /// ```
    pub fn try_io<F, T>(&self, f: F) -> io::Result<T>
    where
        F: FnOnce() -> io::Result<T>,
    {
        self.inner.do_io(|_| f())
    }
}

impl event::Source for Receiver {
    fn register(
        &mut self,
        registry: &Registry,
        token: Token,
        interests: Interest,
    ) -> io::Result<()> {
        self.inner.register(registry, token, interests)
    }

    fn reregister(
        &mut self,
        registry: &Registry,
        token: Token,
        interests: Interest,
    ) -> io::Result<()> {
        self.inner.reregister(registry, token, interests)
    }

    fn deregister(&mut self, registry: &Registry) -> io::Result<()> {
        self.inner.deregister(registry)
    }
}

impl Read for Receiver {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.inner.do_io(|mut sender| sender.read(buf))
    }

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

impl Read for &Receiver {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.inner.do_io(|mut sender| sender.read(buf))
    }

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

/// # Notes
///
/// The underlying pipe is **not** set to non-blocking.
impl From<ChildStdout> for Receiver {
    fn from(stdout: ChildStdout) -> Receiver {
        // Safety: `ChildStdout` is guaranteed to be a valid file descriptor.
        unsafe { Receiver::from_raw_fd(stdout.into_raw_fd()) }
    }
}

/// # Notes
///
/// The underlying pipe is **not** set to non-blocking.
impl From<ChildStderr> for Receiver {
    fn from(stderr: ChildStderr) -> Receiver {
        // Safety: `ChildStderr` is guaranteed to be a valid file descriptor.
        unsafe { Receiver::from_raw_fd(stderr.into_raw_fd()) }
    }
}

impl FromRawFd for Receiver {
    unsafe fn from_raw_fd(fd: RawFd) -> Receiver {
        Receiver {
            inner: IoSource::new(File::from_raw_fd(fd)),
        }
    }
}

impl AsRawFd for Receiver {
    fn as_raw_fd(&self) -> RawFd {
        self.inner.as_raw_fd()
    }
}

impl IntoRawFd for Receiver {
    fn into_raw_fd(self) -> RawFd {
        self.inner.into_inner().into_raw_fd()
    }
}

#[cfg(not(target_os = "illumos"))]
fn set_nonblocking(fd: RawFd, nonblocking: bool) -> io::Result<()> {
    let value = nonblocking as libc::c_int;
    if unsafe { libc::ioctl(fd, libc::FIONBIO, &value) } == -1 {
        Err(io::Error::last_os_error())
    } else {
        Ok(())
    }
}

#[cfg(target_os = "illumos")]
fn set_nonblocking(fd: RawFd, nonblocking: bool) -> io::Result<()> {
    let flags = unsafe { libc::fcntl(fd, libc::F_GETFL) };
    if flags < 0 {
        return Err(io::Error::last_os_error());
    }

    let nflags = if nonblocking {
        flags | libc::O_NONBLOCK
    } else {
        flags & !libc::O_NONBLOCK
    };

    if flags != nflags {
        if unsafe { libc::fcntl(fd, libc::F_SETFL, nflags) } < 0 {
            return Err(io::Error::last_os_error());
        }
    }

    Ok(())
}