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
//! Asynchronous I/O
//!
//! This crate contains the `AsyncRead`, `AsyncWrite`, `AsyncSeek`, and
//! `AsyncBufRead` traits, the asynchronous analogs to
//! `std::io::{Read, Write, Seek, BufRead}`. The primary difference is
//! that these traits integrate with the asynchronous task system.
//!
//! All items of this library are only available when the `std` feature of this
//! library is activated, and it is activated by default.

#![cfg_attr(not(feature = "std"), no_std)]
#![warn(missing_debug_implementations, missing_docs, rust_2018_idioms, unreachable_pub)]
// It cannot be included in the published code because this lints have false positives in the minimum required version.
#![cfg_attr(test, warn(single_use_lifetimes))]
#![doc(test(
    no_crate_inject,
    attr(
        deny(warnings, rust_2018_idioms, single_use_lifetimes),
        allow(dead_code, unused_assignments, unused_variables)
    )
))]
#![cfg_attr(docsrs, feature(doc_cfg))]

#[cfg(feature = "std")]
mod if_std {
    use std::io;
    use std::ops::DerefMut;
    use std::pin::Pin;
    use std::task::{Context, Poll};

    // Re-export some types from `std::io` so that users don't have to deal
    // with conflicts when `use`ing `futures::io` and `std::io`.
    #[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
    #[doc(no_inline)]
    pub use io::{Error, ErrorKind, IoSlice, IoSliceMut, Result, SeekFrom};

    /// Read bytes asynchronously.
    ///
    /// This trait is analogous to the `std::io::Read` trait, but integrates
    /// with the asynchronous task system. In particular, the `poll_read`
    /// method, unlike `Read::read`, will automatically queue the current task
    /// for wakeup and return if data is not yet available, rather than blocking
    /// the calling thread.
    pub trait AsyncRead {
        /// Attempt to read from the `AsyncRead` into `buf`.
        ///
        /// On success, returns `Poll::Ready(Ok(num_bytes_read))`.
        ///
        /// If no data is available for reading, the method returns
        /// `Poll::Pending` and arranges for the current task (via
        /// `cx.waker().wake_by_ref()`) to receive a notification when the object becomes
        /// readable or is closed.
        ///
        /// # Implementation
        ///
        /// This function may not return errors of kind `WouldBlock` or
        /// `Interrupted`.  Implementations must convert `WouldBlock` into
        /// `Poll::Pending` and either internally retry or convert
        /// `Interrupted` into another error kind.
        fn poll_read(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            buf: &mut [u8],
        ) -> Poll<Result<usize>>;

        /// Attempt to read from the `AsyncRead` into `bufs` using vectored
        /// IO operations.
        ///
        /// This method is similar to `poll_read`, but allows data to be read
        /// into multiple buffers using a single operation.
        ///
        /// On success, returns `Poll::Ready(Ok(num_bytes_read))`.
        ///
        /// If no data is available for reading, the method returns
        /// `Poll::Pending` and arranges for the current task (via
        /// `cx.waker().wake_by_ref()`) to receive a notification when the object becomes
        /// readable or is closed.
        /// By default, this method delegates to using `poll_read` on the first
        /// nonempty buffer in `bufs`, or an empty one if none exists. Objects which
        /// support vectored IO should override this method.
        ///
        /// # Implementation
        ///
        /// This function may not return errors of kind `WouldBlock` or
        /// `Interrupted`.  Implementations must convert `WouldBlock` into
        /// `Poll::Pending` and either internally retry or convert
        /// `Interrupted` into another error kind.
        fn poll_read_vectored(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            bufs: &mut [IoSliceMut<'_>],
        ) -> Poll<Result<usize>> {
            for b in bufs {
                if !b.is_empty() {
                    return self.poll_read(cx, b);
                }
            }

            self.poll_read(cx, &mut [])
        }
    }

    /// Write bytes asynchronously.
    ///
    /// This trait is analogous to the `std::io::Write` trait, but integrates
    /// with the asynchronous task system. In particular, the `poll_write`
    /// method, unlike `Write::write`, will automatically queue the current task
    /// for wakeup and return if the writer cannot take more data, rather than blocking
    /// the calling thread.
    pub trait AsyncWrite {
        /// Attempt to write bytes from `buf` into the object.
        ///
        /// On success, returns `Poll::Ready(Ok(num_bytes_written))`.
        ///
        /// If the object is not ready for writing, the method returns
        /// `Poll::Pending` and arranges for the current task (via
        /// `cx.waker().wake_by_ref()`) to receive a notification when the object becomes
        /// writable or is closed.
        ///
        /// # Implementation
        ///
        /// This function may not return errors of kind `WouldBlock` or
        /// `Interrupted`.  Implementations must convert `WouldBlock` into
        /// `Poll::Pending` and either internally retry or convert
        /// `Interrupted` into another error kind.
        ///
        /// `poll_write` must try to make progress by flushing the underlying object if
        /// that is the only way the underlying object can become writable again.
        fn poll_write(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            buf: &[u8],
        ) -> Poll<Result<usize>>;

        /// Attempt to write bytes from `bufs` into the object using vectored
        /// IO operations.
        ///
        /// This method is similar to `poll_write`, but allows data from multiple buffers to be written
        /// using a single operation.
        ///
        /// On success, returns `Poll::Ready(Ok(num_bytes_written))`.
        ///
        /// If the object is not ready for writing, the method returns
        /// `Poll::Pending` and arranges for the current task (via
        /// `cx.waker().wake_by_ref()`) to receive a notification when the object becomes
        /// writable or is closed.
        ///
        /// By default, this method delegates to using `poll_write` on the first
        /// nonempty buffer in `bufs`, or an empty one if none exists. Objects which
        /// support vectored IO should override this method.
        ///
        /// # Implementation
        ///
        /// This function may not return errors of kind `WouldBlock` or
        /// `Interrupted`.  Implementations must convert `WouldBlock` into
        /// `Poll::Pending` and either internally retry or convert
        /// `Interrupted` into another error kind.
        fn poll_write_vectored(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            bufs: &[IoSlice<'_>],
        ) -> Poll<Result<usize>> {
            for b in bufs {
                if !b.is_empty() {
                    return self.poll_write(cx, b);
                }
            }

            self.poll_write(cx, &[])
        }

        /// Attempt to flush the object, ensuring that any buffered data reach
        /// their destination.
        ///
        /// On success, returns `Poll::Ready(Ok(()))`.
        ///
        /// If flushing cannot immediately complete, this method returns
        /// `Poll::Pending` and arranges for the current task (via
        /// `cx.waker().wake_by_ref()`) to receive a notification when the object can make
        /// progress towards flushing.
        ///
        /// # Implementation
        ///
        /// This function may not return errors of kind `WouldBlock` or
        /// `Interrupted`.  Implementations must convert `WouldBlock` into
        /// `Poll::Pending` and either internally retry or convert
        /// `Interrupted` into another error kind.
        ///
        /// It only makes sense to do anything here if you actually buffer data.
        fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>;

        /// Attempt to close the object.
        ///
        /// On success, returns `Poll::Ready(Ok(()))`.
        ///
        /// If closing cannot immediately complete, this function returns
        /// `Poll::Pending` and arranges for the current task (via
        /// `cx.waker().wake_by_ref()`) to receive a notification when the object can make
        /// progress towards closing.
        ///
        /// # Implementation
        ///
        /// This function may not return errors of kind `WouldBlock` or
        /// `Interrupted`.  Implementations must convert `WouldBlock` into
        /// `Poll::Pending` and either internally retry or convert
        /// `Interrupted` into another error kind.
        fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>;
    }

    /// Seek bytes asynchronously.
    ///
    /// This trait is analogous to the `std::io::Seek` trait, but integrates
    /// with the asynchronous task system. In particular, the `poll_seek`
    /// method, unlike `Seek::seek`, will automatically queue the current task
    /// for wakeup and return if data is not yet available, rather than blocking
    /// the calling thread.
    pub trait AsyncSeek {
        /// Attempt to seek to an offset, in bytes, in a stream.
        ///
        /// A seek beyond the end of a stream is allowed, but behavior is defined
        /// by the implementation.
        ///
        /// If the seek operation completed successfully,
        /// this method returns the new position from the start of the stream.
        /// That position can be used later with [`SeekFrom::Start`].
        ///
        /// # Errors
        ///
        /// Seeking to a negative offset is considered an error.
        ///
        /// # Implementation
        ///
        /// This function may not return errors of kind `WouldBlock` or
        /// `Interrupted`.  Implementations must convert `WouldBlock` into
        /// `Poll::Pending` and either internally retry or convert
        /// `Interrupted` into another error kind.
        fn poll_seek(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            pos: SeekFrom,
        ) -> Poll<Result<u64>>;
    }

    /// Read bytes asynchronously.
    ///
    /// This trait is analogous to the `std::io::BufRead` trait, but integrates
    /// with the asynchronous task system. In particular, the `poll_fill_buf`
    /// method, unlike `BufRead::fill_buf`, will automatically queue the current task
    /// for wakeup and return if data is not yet available, rather than blocking
    /// the calling thread.
    pub trait AsyncBufRead: AsyncRead {
        /// Attempt to return the contents of the internal buffer, filling it with more data
        /// from the inner reader if it is empty.
        ///
        /// On success, returns `Poll::Ready(Ok(buf))`.
        ///
        /// If no data is available for reading, the method returns
        /// `Poll::Pending` and arranges for the current task (via
        /// `cx.waker().wake_by_ref()`) to receive a notification when the object becomes
        /// readable or is closed.
        ///
        /// This function is a lower-level call. It needs to be paired with the
        /// [`consume`] method to function properly. When calling this
        /// method, none of the contents will be "read" in the sense that later
        /// calling [`poll_read`] may return the same contents. As such, [`consume`] must
        /// be called with the number of bytes that are consumed from this buffer to
        /// ensure that the bytes are never returned twice.
        ///
        /// [`poll_read`]: AsyncRead::poll_read
        /// [`consume`]: AsyncBufRead::consume
        ///
        /// An empty buffer returned indicates that the stream has reached EOF.
        ///
        /// # Implementation
        ///
        /// This function may not return errors of kind `WouldBlock` or
        /// `Interrupted`.  Implementations must convert `WouldBlock` into
        /// `Poll::Pending` and either internally retry or convert
        /// `Interrupted` into another error kind.
        fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<&[u8]>>;

        /// Tells this buffer that `amt` bytes have been consumed from the buffer,
        /// so they should no longer be returned in calls to [`poll_read`].
        ///
        /// This function is a lower-level call. It needs to be paired with the
        /// [`poll_fill_buf`] method to function properly. This function does
        /// not perform any I/O, it simply informs this object that some amount of
        /// its buffer, returned from [`poll_fill_buf`], has been consumed and should
        /// no longer be returned. As such, this function may do odd things if
        /// [`poll_fill_buf`] isn't called before calling it.
        ///
        /// The `amt` must be `<=` the number of bytes in the buffer returned by
        /// [`poll_fill_buf`].
        ///
        /// [`poll_read`]: AsyncRead::poll_read
        /// [`poll_fill_buf`]: AsyncBufRead::poll_fill_buf
        fn consume(self: Pin<&mut Self>, amt: usize);
    }

    macro_rules! deref_async_read {
        () => {
            fn poll_read(
                mut self: Pin<&mut Self>,
                cx: &mut Context<'_>,
                buf: &mut [u8],
            ) -> Poll<Result<usize>> {
                Pin::new(&mut **self).poll_read(cx, buf)
            }

            fn poll_read_vectored(
                mut self: Pin<&mut Self>,
                cx: &mut Context<'_>,
                bufs: &mut [IoSliceMut<'_>],
            ) -> Poll<Result<usize>> {
                Pin::new(&mut **self).poll_read_vectored(cx, bufs)
            }
        };
    }

    impl<T: ?Sized + AsyncRead + Unpin> AsyncRead for Box<T> {
        deref_async_read!();
    }

    impl<T: ?Sized + AsyncRead + Unpin> AsyncRead for &mut T {
        deref_async_read!();
    }

    impl<P> AsyncRead for Pin<P>
    where
        P: DerefMut + Unpin,
        P::Target: AsyncRead,
    {
        fn poll_read(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            buf: &mut [u8],
        ) -> Poll<Result<usize>> {
            self.get_mut().as_mut().poll_read(cx, buf)
        }

        fn poll_read_vectored(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            bufs: &mut [IoSliceMut<'_>],
        ) -> Poll<Result<usize>> {
            self.get_mut().as_mut().poll_read_vectored(cx, bufs)
        }
    }

    macro_rules! delegate_async_read_to_stdio {
        () => {
            fn poll_read(
                mut self: Pin<&mut Self>,
                _: &mut Context<'_>,
                buf: &mut [u8],
            ) -> Poll<Result<usize>> {
                Poll::Ready(io::Read::read(&mut *self, buf))
            }

            fn poll_read_vectored(
                mut self: Pin<&mut Self>,
                _: &mut Context<'_>,
                bufs: &mut [IoSliceMut<'_>],
            ) -> Poll<Result<usize>> {
                Poll::Ready(io::Read::read_vectored(&mut *self, bufs))
            }
        };
    }

    impl AsyncRead for &[u8] {
        delegate_async_read_to_stdio!();
    }

    macro_rules! deref_async_write {
        () => {
            fn poll_write(
                mut self: Pin<&mut Self>,
                cx: &mut Context<'_>,
                buf: &[u8],
            ) -> Poll<Result<usize>> {
                Pin::new(&mut **self).poll_write(cx, buf)
            }

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

            fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>> {
                Pin::new(&mut **self).poll_flush(cx)
            }

            fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>> {
                Pin::new(&mut **self).poll_close(cx)
            }
        };
    }

    impl<T: ?Sized + AsyncWrite + Unpin> AsyncWrite for Box<T> {
        deref_async_write!();
    }

    impl<T: ?Sized + AsyncWrite + Unpin> AsyncWrite for &mut T {
        deref_async_write!();
    }

    impl<P> AsyncWrite for Pin<P>
    where
        P: DerefMut + Unpin,
        P::Target: AsyncWrite,
    {
        fn poll_write(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            buf: &[u8],
        ) -> Poll<Result<usize>> {
            self.get_mut().as_mut().poll_write(cx, buf)
        }

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

        fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>> {
            self.get_mut().as_mut().poll_flush(cx)
        }

        fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>> {
            self.get_mut().as_mut().poll_close(cx)
        }
    }

    macro_rules! delegate_async_write_to_stdio {
        () => {
            fn poll_write(
                mut self: Pin<&mut Self>,
                _: &mut Context<'_>,
                buf: &[u8],
            ) -> Poll<Result<usize>> {
                Poll::Ready(io::Write::write(&mut *self, buf))
            }

            fn poll_write_vectored(
                mut self: Pin<&mut Self>,
                _: &mut Context<'_>,
                bufs: &[IoSlice<'_>],
            ) -> Poll<Result<usize>> {
                Poll::Ready(io::Write::write_vectored(&mut *self, bufs))
            }

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

            fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>> {
                self.poll_flush(cx)
            }
        };
    }

    impl AsyncWrite for Vec<u8> {
        delegate_async_write_to_stdio!();
    }

    macro_rules! deref_async_seek {
        () => {
            fn poll_seek(
                mut self: Pin<&mut Self>,
                cx: &mut Context<'_>,
                pos: SeekFrom,
            ) -> Poll<Result<u64>> {
                Pin::new(&mut **self).poll_seek(cx, pos)
            }
        };
    }

    impl<T: ?Sized + AsyncSeek + Unpin> AsyncSeek for Box<T> {
        deref_async_seek!();
    }

    impl<T: ?Sized + AsyncSeek + Unpin> AsyncSeek for &mut T {
        deref_async_seek!();
    }

    impl<P> AsyncSeek for Pin<P>
    where
        P: DerefMut + Unpin,
        P::Target: AsyncSeek,
    {
        fn poll_seek(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            pos: SeekFrom,
        ) -> Poll<Result<u64>> {
            self.get_mut().as_mut().poll_seek(cx, pos)
        }
    }

    macro_rules! deref_async_buf_read {
        () => {
            fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<&[u8]>> {
                Pin::new(&mut **self.get_mut()).poll_fill_buf(cx)
            }

            fn consume(mut self: Pin<&mut Self>, amt: usize) {
                Pin::new(&mut **self).consume(amt)
            }
        };
    }

    impl<T: ?Sized + AsyncBufRead + Unpin> AsyncBufRead for Box<T> {
        deref_async_buf_read!();
    }

    impl<T: ?Sized + AsyncBufRead + Unpin> AsyncBufRead for &mut T {
        deref_async_buf_read!();
    }

    impl<P> AsyncBufRead for Pin<P>
    where
        P: DerefMut + Unpin,
        P::Target: AsyncBufRead,
    {
        fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<&[u8]>> {
            self.get_mut().as_mut().poll_fill_buf(cx)
        }

        fn consume(self: Pin<&mut Self>, amt: usize) {
            self.get_mut().as_mut().consume(amt)
        }
    }

    macro_rules! delegate_async_buf_read_to_stdio {
        () => {
            fn poll_fill_buf(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Result<&[u8]>> {
                Poll::Ready(io::BufRead::fill_buf(self.get_mut()))
            }

            fn consume(self: Pin<&mut Self>, amt: usize) {
                io::BufRead::consume(self.get_mut(), amt)
            }
        };
    }

    impl AsyncBufRead for &[u8] {
        delegate_async_buf_read_to_stdio!();
    }
}

#[cfg(feature = "std")]
pub use self::if_std::*;