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
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
use crate::future::poll_fn;
use crate::io::{AsyncRead, AsyncWrite, Interest, PollEvented, ReadBuf, Ready};
use crate::net::unix::split::{split, ReadHalf, WriteHalf};
use crate::net::unix::split_owned::{split_owned, OwnedReadHalf, OwnedWriteHalf};
use crate::net::unix::ucred::{self, UCred};
use crate::net::unix::SocketAddr;

use std::convert::TryFrom;
use std::fmt;
use std::io::{self, Read, Write};
use std::net::Shutdown;
use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
use std::os::unix::net;
use std::path::Path;
use std::pin::Pin;
use std::task::{Context, Poll};

cfg_io_util! {
    use bytes::BufMut;
}

cfg_net_unix! {
    /// A structure representing a connected Unix socket.
    ///
    /// This socket can be connected directly with `UnixStream::connect` or accepted
    /// from a listener with `UnixListener::incoming`. Additionally, a pair of
    /// anonymous Unix sockets can be created with `UnixStream::pair`.
    ///
    /// To shut down the stream in the write direction, you can call the
    /// [`shutdown()`] method. This will cause the other peer to receive a read of
    /// length 0, indicating that no more data will be sent. This only closes
    /// the stream in one direction.
    ///
    /// [`shutdown()`]: fn@crate::io::AsyncWriteExt::shutdown
    pub struct UnixStream {
        io: PollEvented<mio::net::UnixStream>,
    }
}

impl UnixStream {
    /// Connects to the socket named by `path`.
    ///
    /// This function will create a new Unix socket and connect to the path
    /// specified, associating the returned stream with the default event loop's
    /// handle.
    pub async fn connect<P>(path: P) -> io::Result<UnixStream>
    where
        P: AsRef<Path>,
    {
        let stream = mio::net::UnixStream::connect(path)?;
        let stream = UnixStream::new(stream)?;

        poll_fn(|cx| stream.io.registration().poll_write_ready(cx)).await?;
        Ok(stream)
    }

    /// Wait for any of the requested ready states.
    ///
    /// This function is usually paired with `try_read()` or `try_write()`. It
    /// can be used to concurrently read / write to the same socket on a single
    /// task without splitting the socket.
    ///
    /// # Examples
    ///
    /// Concurrently read and write to the stream on the same task without
    /// splitting.
    ///
    /// ```no_run
    /// use tokio::io::Interest;
    /// use tokio::net::UnixStream;
    /// use std::error::Error;
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> Result<(), Box<dyn Error>> {
    ///     let dir = tempfile::tempdir().unwrap();
    ///     let bind_path = dir.path().join("bind_path");
    ///     let stream = UnixStream::connect(bind_path).await?;
    ///
    ///     loop {
    ///         let ready = stream.ready(Interest::READABLE | Interest::WRITABLE).await?;
    ///
    ///         if ready.is_readable() {
    ///             let mut data = vec![0; 1024];
    ///             // Try to read data, this may still fail with `WouldBlock`
    ///             // if the readiness event is a false positive.
    ///             match stream.try_read(&mut data) {
    ///                 Ok(n) => {
    ///                     println!("read {} bytes", n);        
    ///                 }
    ///                 Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
    ///                     continue;
    ///                 }
    ///                 Err(e) => {
    ///                     return Err(e.into());
    ///                 }
    ///             }
    ///
    ///         }
    ///
    ///         if ready.is_writable() {
    ///             // Try to write data, this may still fail with `WouldBlock`
    ///             // if the readiness event is a false positive.
    ///             match stream.try_write(b"hello world") {
    ///                 Ok(n) => {
    ///                     println!("write {} bytes", n);
    ///                 }
    ///                 Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
    ///                     continue;
    ///                 }
    ///                 Err(e) => {
    ///                     return Err(e.into());
    ///                 }
    ///             }
    ///         }
    ///     }
    /// }
    /// ```
    pub async fn ready(&self, interest: Interest) -> io::Result<Ready> {
        let event = self.io.registration().readiness(interest).await?;
        Ok(event.ready)
    }

    /// Wait for the socket to become readable.
    ///
    /// This function is equivalent to `ready(Interest::READABLE)` and is usually
    /// paired with `try_read()`.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use tokio::net::UnixStream;
    /// use std::error::Error;
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> Result<(), Box<dyn Error>> {
    ///     // Connect to a peer
    ///     let dir = tempfile::tempdir().unwrap();
    ///     let bind_path = dir.path().join("bind_path");
    ///     let stream = UnixStream::connect(bind_path).await?;
    ///
    ///     let mut msg = vec![0; 1024];
    ///
    ///     loop {
    ///         // Wait for the socket to be readable
    ///         stream.readable().await?;
    ///
    ///         // Try to read data, this may still fail with `WouldBlock`
    ///         // if the readiness event is a false positive.
    ///         match stream.try_read(&mut msg) {
    ///             Ok(n) => {
    ///                 msg.truncate(n);
    ///                 break;
    ///             }
    ///             Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
    ///                 continue;
    ///             }
    ///             Err(e) => {
    ///                 return Err(e.into());
    ///             }
    ///         }
    ///     }
    ///
    ///     println!("GOT = {:?}", msg);
    ///     Ok(())
    /// }
    /// ```
    pub async fn readable(&self) -> io::Result<()> {
        self.ready(Interest::READABLE).await?;
        Ok(())
    }

    /// Polls for read readiness.
    ///
    /// If the unix stream is not currently ready for reading, this method will
    /// store a clone of the `Waker` from the provided `Context`. When the unix
    /// stream becomes ready for reading, `Waker::wake` will be called on the
    /// waker.
    ///
    /// Note that on multiple calls to `poll_read_ready` or `poll_read`, only
    /// the `Waker` from the `Context` passed to the most recent call is
    /// scheduled to receive a wakeup. (However, `poll_write_ready` retains a
    /// second, independent waker.)
    ///
    /// This function is intended for cases where creating and pinning a future
    /// via [`readable`] is not feasible. Where possible, using [`readable`] is
    /// preferred, as this supports polling from multiple tasks at once.
    ///
    /// # Return value
    ///
    /// The function returns:
    ///
    /// * `Poll::Pending` if the unix stream is not ready for reading.
    /// * `Poll::Ready(Ok(()))` if the unix stream is ready for reading.
    /// * `Poll::Ready(Err(e))` if an error is encountered.
    ///
    /// # Errors
    ///
    /// This function may encounter any standard I/O error except `WouldBlock`.
    ///
    /// [`readable`]: method@Self::readable
    pub fn poll_read_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
        self.io.registration().poll_read_ready(cx).map_ok(|_| ())
    }

    /// Try to read data from the stream into the provided buffer, returning how
    /// many bytes were read.
    ///
    /// Receives any pending data from the socket but does not wait for new data
    /// to arrive. On success, returns the number of bytes read. Because
    /// `try_read()` is non-blocking, the buffer does not have to be stored by
    /// the async task and can exist entirely on the stack.
    ///
    /// Usually, [`readable()`] or [`ready()`] is used with this function.
    ///
    /// [`readable()`]: UnixStream::readable()
    /// [`ready()`]: UnixStream::ready()
    ///
    /// # Return
    ///
    /// If data is successfully read, `Ok(n)` is returned, where `n` is the
    /// number of bytes read. `Ok(0)` indicates the stream's read half is closed
    /// and will no longer yield data. If the stream is not ready to read data
    /// `Err(io::ErrorKind::WouldBlock)` is returned.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use tokio::net::UnixStream;
    /// use std::error::Error;
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> Result<(), Box<dyn Error>> {
    ///     // Connect to a peer
    ///     let dir = tempfile::tempdir().unwrap();
    ///     let bind_path = dir.path().join("bind_path");
    ///     let stream = UnixStream::connect(bind_path).await?;
    ///
    ///     loop {
    ///         // Wait for the socket to be readable
    ///         stream.readable().await?;
    ///
    ///         // Creating the buffer **after** the `await` prevents it from
    ///         // being stored in the async task.
    ///         let mut buf = [0; 4096];
    ///
    ///         // Try to read data, this may still fail with `WouldBlock`
    ///         // if the readiness event is a false positive.
    ///         match stream.try_read(&mut buf) {
    ///             Ok(0) => break,
    ///             Ok(n) => {
    ///                 println!("read {} bytes", n);
    ///             }
    ///             Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
    ///                 continue;
    ///             }
    ///             Err(e) => {
    ///                 return Err(e.into());
    ///             }
    ///         }
    ///     }
    ///
    ///     Ok(())
    /// }
    /// ```
    pub fn try_read(&self, buf: &mut [u8]) -> io::Result<usize> {
        self.io
            .registration()
            .try_io(Interest::READABLE, || (&*self.io).read(buf))
    }

    cfg_io_util! {
        /// Try to read data from the stream into the provided buffer, advancing the
        /// buffer's internal cursor, returning how many bytes were read.
        ///
        /// Receives any pending data from the socket but does not wait for new data
        /// to arrive. On success, returns the number of bytes read. Because
        /// `try_read_buf()` is non-blocking, the buffer does not have to be stored by
        /// the async task and can exist entirely on the stack.
        ///
        /// Usually, [`readable()`] or [`ready()`] is used with this function.
        ///
        /// [`readable()`]: UnixStream::readable()
        /// [`ready()`]: UnixStream::ready()
        ///
        /// # Return
        ///
        /// If data is successfully read, `Ok(n)` is returned, where `n` is the
        /// number of bytes read. `Ok(0)` indicates the stream's read half is closed
        /// and will no longer yield data. If the stream is not ready to read data
        /// `Err(io::ErrorKind::WouldBlock)` is returned.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use tokio::net::UnixStream;
        /// use std::error::Error;
        /// use std::io;
        ///
        /// #[tokio::main]
        /// async fn main() -> Result<(), Box<dyn Error>> {
        ///     // Connect to a peer
        ///     let dir = tempfile::tempdir().unwrap();
        ///     let bind_path = dir.path().join("bind_path");
        ///     let stream = UnixStream::connect(bind_path).await?;
        ///
        ///     loop {
        ///         // Wait for the socket to be readable
        ///         stream.readable().await?;
        ///
        ///         let mut buf = Vec::with_capacity(4096);
        ///
        ///         // Try to read data, this may still fail with `WouldBlock`
        ///         // if the readiness event is a false positive.
        ///         match stream.try_read_buf(&mut buf) {
        ///             Ok(0) => break,
        ///             Ok(n) => {
        ///                 println!("read {} bytes", n);
        ///             }
        ///             Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
        ///                 continue;
        ///             }
        ///             Err(e) => {
        ///                 return Err(e.into());
        ///             }
        ///         }
        ///     }
        ///
        ///     Ok(())
        /// }
        /// ```
        pub fn try_read_buf<B: BufMut>(&self, buf: &mut B) -> io::Result<usize> {
            self.io.registration().try_io(Interest::READABLE, || {
                use std::io::Read;

                let dst = buf.chunk_mut();
                let dst =
                    unsafe { &mut *(dst as *mut _ as *mut [std::mem::MaybeUninit<u8>] as *mut [u8]) };

                // Safety: We trust `UnixStream::read` to have filled up `n` bytes in the
                // buffer.
                let n = (&*self.io).read(dst)?;

                unsafe {
                    buf.advance_mut(n);
                }

                Ok(n)
            })
        }
    }

    /// Wait for the socket to become writable.
    ///
    /// This function is equivalent to `ready(Interest::WRITABLE)` and is usually
    /// paired with `try_write()`.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use tokio::net::UnixStream;
    /// use std::error::Error;
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> Result<(), Box<dyn Error>> {
    ///     // Connect to a peer
    ///     let dir = tempfile::tempdir().unwrap();
    ///     let bind_path = dir.path().join("bind_path");
    ///     let stream = UnixStream::connect(bind_path).await?;
    ///
    ///     loop {
    ///         // Wait for the socket to be writable
    ///         stream.writable().await?;
    ///
    ///         // Try to write data, this may still fail with `WouldBlock`
    ///         // if the readiness event is a false positive.
    ///         match stream.try_write(b"hello world") {
    ///             Ok(n) => {
    ///                 break;
    ///             }
    ///             Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
    ///                 continue;
    ///             }
    ///             Err(e) => {
    ///                 return Err(e.into());
    ///             }
    ///         }
    ///     }
    ///
    ///     Ok(())
    /// }
    /// ```
    pub async fn writable(&self) -> io::Result<()> {
        self.ready(Interest::WRITABLE).await?;
        Ok(())
    }

    /// Polls for write readiness.
    ///
    /// If the unix stream is not currently ready for writing, this method will
    /// store a clone of the `Waker` from the provided `Context`. When the unix
    /// stream becomes ready for writing, `Waker::wake` will be called on the
    /// waker.
    ///
    /// Note that on multiple calls to `poll_write_ready` or `poll_write`, only
    /// the `Waker` from the `Context` passed to the most recent call is
    /// scheduled to receive a wakeup. (However, `poll_read_ready` retains a
    /// second, independent waker.)
    ///
    /// This function is intended for cases where creating and pinning a future
    /// via [`writable`] is not feasible. Where possible, using [`writable`] is
    /// preferred, as this supports polling from multiple tasks at once.
    ///
    /// # Return value
    ///
    /// The function returns:
    ///
    /// * `Poll::Pending` if the unix stream is not ready for writing.
    /// * `Poll::Ready(Ok(()))` if the unix stream is ready for writing.
    /// * `Poll::Ready(Err(e))` if an error is encountered.
    ///
    /// # Errors
    ///
    /// This function may encounter any standard I/O error except `WouldBlock`.
    ///
    /// [`writable`]: method@Self::writable
    pub fn poll_write_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
        self.io.registration().poll_write_ready(cx).map_ok(|_| ())
    }

    /// Try to write a buffer to the stream, returning how many bytes were
    /// written.
    ///
    /// The function will attempt to write the entire contents of `buf`, but
    /// only part of the buffer may be written.
    ///
    /// This function is usually paired with `writable()`.
    ///
    /// # Return
    ///
    /// If data is successfully written, `Ok(n)` is returned, where `n` is the
    /// number of bytes written. If the stream is not ready to write data,
    /// `Err(io::ErrorKind::WouldBlock)` is returned.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use tokio::net::UnixStream;
    /// use std::error::Error;
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> Result<(), Box<dyn Error>> {
    ///     // Connect to a peer
    ///     let dir = tempfile::tempdir().unwrap();
    ///     let bind_path = dir.path().join("bind_path");
    ///     let stream = UnixStream::connect(bind_path).await?;
    ///
    ///     loop {
    ///         // Wait for the socket to be writable
    ///         stream.writable().await?;
    ///
    ///         // Try to write data, this may still fail with `WouldBlock`
    ///         // if the readiness event is a false positive.
    ///         match stream.try_write(b"hello world") {
    ///             Ok(n) => {
    ///                 break;
    ///             }
    ///             Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
    ///                 continue;
    ///             }
    ///             Err(e) => {
    ///                 return Err(e.into());
    ///             }
    ///         }
    ///     }
    ///
    ///     Ok(())
    /// }
    /// ```
    pub fn try_write(&self, buf: &[u8]) -> io::Result<usize> {
        self.io
            .registration()
            .try_io(Interest::WRITABLE, || (&*self.io).write(buf))
    }

    /// Creates new `UnixStream` from a `std::os::unix::net::UnixStream`.
    ///
    /// This function is intended to be used to wrap a UnixStream from the
    /// standard library in the Tokio equivalent. The conversion assumes
    /// nothing about the underlying stream; it is left up to the user to set
    /// it in non-blocking mode.
    ///
    /// # Panics
    ///
    /// This function panics if thread-local runtime is not set.
    ///
    /// The runtime is usually set implicitly when this function is called
    /// from a future driven by a tokio runtime, otherwise runtime can be set
    /// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
    pub fn from_std(stream: net::UnixStream) -> io::Result<UnixStream> {
        let stream = mio::net::UnixStream::from_std(stream);
        let io = PollEvented::new(stream)?;

        Ok(UnixStream { io })
    }

    /// Turn a [`tokio::net::UnixStream`] into a [`std::os::unix::net::UnixStream`].
    ///
    /// The returned [`std::os::unix::net::UnixStream`] will have nonblocking
    /// mode set as `true`.  Use [`set_nonblocking`] to change the blocking
    /// mode if needed.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::error::Error;
    /// use std::io::Read;
    /// use tokio::net::UnixListener;
    /// # use tokio::net::UnixStream;
    /// # use tokio::io::AsyncWriteExt;
    ///
    /// #[tokio::main]
    /// async fn main() -> Result<(), Box<dyn Error>> {
    ///     let dir = tempfile::tempdir().unwrap();
    ///     let bind_path = dir.path().join("bind_path");
    ///
    ///     let mut data = [0u8; 12];
    ///     let listener = UnixListener::bind(&bind_path)?;
    /// #   let handle = tokio::spawn(async {
    /// #       let mut stream = UnixStream::connect(bind_path).await.unwrap();
    /// #       stream.write(b"Hello world!").await.unwrap();
    /// #   });
    ///     let (tokio_unix_stream, _) = listener.accept().await?;
    ///     let mut std_unix_stream = tokio_unix_stream.into_std()?;
    /// #   handle.await.expect("The task being joined has panicked");
    ///     std_unix_stream.set_nonblocking(false)?;
    ///     std_unix_stream.read_exact(&mut data)?;
    /// #   assert_eq!(b"Hello world!", &data);
    ///     Ok(())
    /// }
    /// ```
    /// [`tokio::net::UnixStream`]: UnixStream
    /// [`std::os::unix::net::UnixStream`]: std::os::unix::net::UnixStream
    /// [`set_nonblocking`]: fn@std::os::unix::net::UnixStream::set_nonblocking
    pub fn into_std(self) -> io::Result<std::os::unix::net::UnixStream> {
        self.io
            .into_inner()
            .map(|io| io.into_raw_fd())
            .map(|raw_fd| unsafe { std::os::unix::net::UnixStream::from_raw_fd(raw_fd) })
    }

    /// Creates an unnamed pair of connected sockets.
    ///
    /// This function will create a pair of interconnected Unix sockets for
    /// communicating back and forth between one another. Each socket will
    /// be associated with the default event loop's handle.
    pub fn pair() -> io::Result<(UnixStream, UnixStream)> {
        let (a, b) = mio::net::UnixStream::pair()?;
        let a = UnixStream::new(a)?;
        let b = UnixStream::new(b)?;

        Ok((a, b))
    }

    pub(crate) fn new(stream: mio::net::UnixStream) -> io::Result<UnixStream> {
        let io = PollEvented::new(stream)?;
        Ok(UnixStream { io })
    }

    /// Returns the socket address of the local half of this connection.
    pub fn local_addr(&self) -> io::Result<SocketAddr> {
        self.io.local_addr().map(SocketAddr)
    }

    /// Returns the socket address of the remote half of this connection.
    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
        self.io.peer_addr().map(SocketAddr)
    }

    /// Returns effective credentials of the process which called `connect` or `pair`.
    pub fn peer_cred(&self) -> io::Result<UCred> {
        ucred::get_peer_cred(self)
    }

    /// Returns the value of the `SO_ERROR` option.
    pub fn take_error(&self) -> io::Result<Option<io::Error>> {
        self.io.take_error()
    }

    /// Shuts down the read, write, or both halves of this connection.
    ///
    /// This function will cause all pending and future I/O calls on the
    /// specified portions to immediately return with an appropriate value
    /// (see the documentation of `Shutdown`).
    pub(super) fn shutdown_std(&self, how: Shutdown) -> io::Result<()> {
        self.io.shutdown(how)
    }

    // These lifetime markers also appear in the generated documentation, and make
    // it more clear that this is a *borrowed* split.
    #[allow(clippy::needless_lifetimes)]
    /// Split a `UnixStream` into a read half and a write half, which can be used
    /// to read and write the stream concurrently.
    ///
    /// This method is more efficient than [`into_split`], but the halves cannot be
    /// moved into independently spawned tasks.
    ///
    /// [`into_split`]: Self::into_split()
    pub fn split<'a>(&'a mut self) -> (ReadHalf<'a>, WriteHalf<'a>) {
        split(self)
    }

    /// Splits a `UnixStream` into a read half and a write half, which can be used
    /// to read and write the stream concurrently.
    ///
    /// Unlike [`split`], the owned halves can be moved to separate tasks, however
    /// this comes at the cost of a heap allocation.
    ///
    /// **Note:** Dropping the write half will shut down the write half of the
    /// stream. This is equivalent to calling [`shutdown()`] on the `UnixStream`.
    ///
    /// [`split`]: Self::split()
    /// [`shutdown()`]: fn@crate::io::AsyncWriteExt::shutdown
    pub fn into_split(self) -> (OwnedReadHalf, OwnedWriteHalf) {
        split_owned(self)
    }
}

impl TryFrom<net::UnixStream> for UnixStream {
    type Error = io::Error;

    /// Consumes stream, returning the tokio I/O object.
    ///
    /// This is equivalent to
    /// [`UnixStream::from_std(stream)`](UnixStream::from_std).
    fn try_from(stream: net::UnixStream) -> io::Result<Self> {
        Self::from_std(stream)
    }
}

impl AsyncRead for UnixStream {
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &mut ReadBuf<'_>,
    ) -> Poll<io::Result<()>> {
        self.poll_read_priv(cx, buf)
    }
}

impl AsyncWrite for UnixStream {
    fn poll_write(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &[u8],
    ) -> Poll<io::Result<usize>> {
        self.poll_write_priv(cx, buf)
    }

    fn poll_write_vectored(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        bufs: &[io::IoSlice<'_>],
    ) -> Poll<io::Result<usize>> {
        self.poll_write_vectored_priv(cx, bufs)
    }

    fn is_write_vectored(&self) -> bool {
        true
    }

    fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
        Poll::Ready(Ok(()))
    }

    fn poll_shutdown(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
        self.shutdown_std(std::net::Shutdown::Write)?;
        Poll::Ready(Ok(()))
    }
}

impl UnixStream {
    // == Poll IO functions that takes `&self` ==
    //
    // They are not public because (taken from the doc of `PollEvented`):
    //
    // While `PollEvented` is `Sync` (if the underlying I/O type is `Sync`), the
    // caller must ensure that there are at most two tasks that use a
    // `PollEvented` instance concurrently. One for reading and one for writing.
    // While violating this requirement is "safe" from a Rust memory model point
    // of view, it will result in unexpected behavior in the form of lost
    // notifications and tasks hanging.

    pub(crate) fn poll_read_priv(
        &self,
        cx: &mut Context<'_>,
        buf: &mut ReadBuf<'_>,
    ) -> Poll<io::Result<()>> {
        // Safety: `UnixStream::read` correctly handles reads into uninitialized memory
        unsafe { self.io.poll_read(cx, buf) }
    }

    pub(crate) fn poll_write_priv(
        &self,
        cx: &mut Context<'_>,
        buf: &[u8],
    ) -> Poll<io::Result<usize>> {
        self.io.poll_write(cx, buf)
    }

    pub(super) fn poll_write_vectored_priv(
        &self,
        cx: &mut Context<'_>,
        bufs: &[io::IoSlice<'_>],
    ) -> Poll<io::Result<usize>> {
        self.io.poll_write_vectored(cx, bufs)
    }
}

impl fmt::Debug for UnixStream {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.io.fmt(f)
    }
}

impl AsRawFd for UnixStream {
    fn as_raw_fd(&self) -> RawFd {
        self.io.as_raw_fd()
    }
}