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
mod bytes;
mod chain;
mod read;
mod read_exact;
mod read_to_end;
mod read_to_string;
mod read_vectored;
mod take;

use read::ReadFuture;
use read_exact::ReadExactFuture;
use read_to_end::{read_to_end_internal, ReadToEndFuture};
use read_to_string::ReadToStringFuture;
use read_vectored::ReadVectoredFuture;

use std::mem;

use crate::io::IoSliceMut;

extension_trait! {
    use std::pin::Pin;
    use std::ops::{Deref, DerefMut};

    use crate::io;
    use crate::task::{Context, Poll};

    #[doc = r#"
        Allows reading from a byte stream.

        This trait is a re-export of [`futures::io::AsyncRead`] and is an async version of
        [`std::io::Read`].

        Methods other than [`poll_read`] and [`poll_read_vectored`] do not really exist in the
        trait itself, but they become available when [`ReadExt`] from the [prelude] is imported:

        ```
        # #[allow(unused_imports)]
        use async_std::prelude::*;
        ```

        [`std::io::Read`]: https://doc.rust-lang.org/std/io/trait.Read.html
        [`futures::io::AsyncRead`]:
        https://docs.rs/futures-preview/0.3.0-alpha.17/futures/io/trait.AsyncRead.html
        [`poll_read`]: #tymethod.poll_read
        [`poll_read_vectored`]: #method.poll_read_vectored
        [`ReadExt`]: ../io/prelude/trait.ReadExt.html
        [prelude]: ../prelude/index.html
    "#]
    pub trait Read {
        #[doc = r#"
            Attempt to read from the `AsyncRead` into `buf`.
        "#]
        fn poll_read(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            buf: &mut [u8],
        ) -> Poll<io::Result<usize>>;

        #[doc = r#"
            Attempt to read from the `AsyncRead` into `bufs` using vectored IO operations.
        "#]
        fn poll_read_vectored(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            bufs: &mut [IoSliceMut<'_>],
        ) -> Poll<io::Result<usize>> {
            unreachable!("this impl only appears in the rendered docs")
        }
    }

    #[doc = r#"
        Extension methods for [`Read`].

        [`Read`]: ../trait.Read.html
    "#]
    pub trait ReadExt: futures_io::AsyncRead {
        #[doc = r#"
            Reads some bytes from the byte stream.

            Returns the number of bytes read from the start of the buffer.

            If the return value is `Ok(n)`, then it must be guaranteed that
            `0 <= n <= buf.len()`. A nonzero `n` value indicates that the buffer has been
            filled in with `n` bytes of data. If `n` is `0`, then it can indicate one of two
            scenarios:

            1. This reader has reached its "end of file" and will likely no longer be able to
               produce bytes. Note that this does not mean that the reader will always no
               longer be able to produce bytes.
            2. The buffer specified was 0 bytes in length.

            # Examples

            ```no_run
            # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
            #
            use async_std::fs::File;
            use async_std::prelude::*;

            let mut file = File::open("a.txt").await?;

            let mut buf = vec![0; 1024];
            let n = file.read(&mut buf).await?;
            #
            # Ok(()) }) }
            ```
        "#]
        fn read<'a>(
            &'a mut self,
            buf: &'a mut [u8],
        ) -> impl Future<Output = io::Result<usize>> + 'a [ReadFuture<'a, Self>]
        where
            Self: Unpin
        {
            ReadFuture { reader: self, buf }
        }

        #[doc = r#"
            Like [`read`], except that it reads into a slice of buffers.

            Data is copied to fill each buffer in order, with the final buffer written to
            possibly being only partially filled. This method must behave as a single call to
            [`read`] with the buffers concatenated would.

            The default implementation calls [`read`] with either the first nonempty buffer
            provided, or an empty one if none exists.

            [`read`]: #tymethod.read
        "#]
        fn read_vectored<'a>(
            &'a mut self,
            bufs: &'a mut [IoSliceMut<'a>],
        ) -> impl Future<Output = io::Result<usize>> + 'a [ReadVectoredFuture<'a, Self>]
        where
            Self: Unpin,
        {
            ReadVectoredFuture { reader: self, bufs }
        }

        #[doc = r#"
            Reads all bytes from the byte stream.

            All bytes read from this stream will be appended to the specified buffer `buf`.
            This function will continuously call [`read`] to append more data to `buf` until
            [`read`] returns either `Ok(0)` or an error.

            If successful, this function will return the total number of bytes read.

            [`read`]: #tymethod.read

            # Examples

            ```no_run
            # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
            #
            use async_std::fs::File;
            use async_std::prelude::*;

            let mut file = File::open("a.txt").await?;

            let mut buf = Vec::new();
            file.read_to_end(&mut buf).await?;
            #
            # Ok(()) }) }
            ```
        "#]
        fn read_to_end<'a>(
            &'a mut self,
            buf: &'a mut Vec<u8>,
        ) -> impl Future<Output = io::Result<usize>> + 'a [ReadToEndFuture<'a, Self>]
        where
            Self: Unpin,
        {
            let start_len = buf.len();
            ReadToEndFuture {
                reader: self,
                buf,
                start_len,
            }
        }

        #[doc = r#"
            Reads all bytes from the byte stream and appends them into a string.

            If successful, this function will return the number of bytes read.

            If the data in this stream is not valid UTF-8 then an error will be returned and
            `buf` will be left unmodified.

            # Examples

            ```no_run
            # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
            #
            use async_std::fs::File;
            use async_std::prelude::*;

            let mut file = File::open("a.txt").await?;

            let mut buf = String::new();
            file.read_to_string(&mut buf).await?;
            #
            # Ok(()) }) }
            ```
        "#]
        fn read_to_string<'a>(
            &'a mut self,
            buf: &'a mut String,
        ) -> impl Future<Output = io::Result<usize>> + 'a [ReadToStringFuture<'a, Self>]
        where
            Self: Unpin,
        {
            let start_len = buf.len();
            ReadToStringFuture {
                reader: self,
                bytes: unsafe { mem::replace(buf.as_mut_vec(), Vec::new()) },
                buf,
                start_len,
            }
        }

        #[doc = r#"
            Reads the exact number of bytes required to fill `buf`.

            This function reads as many bytes as necessary to completely fill the specified
            buffer `buf`.

            No guarantees are provided about the contents of `buf` when this function is
            called, implementations cannot rely on any property of the contents of `buf` being
            true. It is recommended that implementations only write data to `buf` instead of
            reading its contents.

            If this function encounters an "end of file" before completely filling the buffer,
            it returns an error of the kind [`ErrorKind::UnexpectedEof`].  The contents of
            `buf` are unspecified in this case.

            If any other read error is encountered then this function immediately returns. The
            contents of `buf` are unspecified in this case.

            If this function returns an error, it is unspecified how many bytes it has read,
            but it will never read more than would be necessary to completely fill the buffer.

            [`ErrorKind::UnexpectedEof`]: enum.ErrorKind.html#variant.UnexpectedEof

            # Examples

            ```no_run
            # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
            #
            use async_std::fs::File;
            use async_std::prelude::*;

            let mut file = File::open("a.txt").await?;

            let mut buf = vec![0; 10];
            file.read_exact(&mut buf).await?;
            #
            # Ok(()) }) }
            ```
        "#]
        fn read_exact<'a>(
            &'a mut self,
            buf: &'a mut [u8],
        ) -> impl Future<Output = io::Result<()>> + 'a [ReadExactFuture<'a, Self>]
        where
            Self: Unpin,
        {
            ReadExactFuture { reader: self, buf }
        }

        #[doc = r#"
            Creates an adaptor which will read at most `limit` bytes from it.

            This function returns a new instance of `Read` which will read at most
            `limit` bytes, after which it will always return EOF ([`Ok(0)`]). Any
            read errors will not count towards the number of bytes read and future
            calls to [`read`] may succeed.

            # Examples

            [`File`]s implement `Read`:

            [`File`]: ../fs/struct.File.html
            [`Ok(0)`]: ../../std/result/enum.Result.html#variant.Ok
            [`read`]: tymethod.read

            ```no_run
            # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
            #
            use async_std::io::prelude::*;
            use async_std::fs::File;

            let f = File::open("foo.txt").await?;
            let mut buffer = [0; 5];

            // read at most five bytes
            let mut handle = f.take(5);

            handle.read(&mut buffer).await?;
            #
            # Ok(()) }) }
            ```
        "#]
        fn take(self, limit: u64) -> take::Take<Self>
        where
            Self: Sized,
        {
            take::Take { inner: self, limit }
        }

        #[doc = r#"
            Creates a "by reference" adaptor for this instance of `Read`.

            The returned adaptor also implements `Read` and will simply borrow this
            current reader.

            # Examples

            [`File`][file]s implement `Read`:

            [file]: ../fs/struct.File.html

            ```no_run
            # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
            #
            use async_std::prelude::*;
            use async_std::fs::File;

            let mut f = File::open("foo.txt").await?;
            let mut buffer = Vec::new();
            let mut other_buffer = Vec::new();

            {
                let reference = f.by_ref();

                // read at most 5 bytes
                reference.take(5).read_to_end(&mut buffer).await?;

            } // drop our &mut reference so we can use f again

            // original file still usable, read the rest
            f.read_to_end(&mut other_buffer).await?;
            #
            # Ok(()) }) }
            ```
        "#]
        fn by_ref(&mut self) -> &mut Self where Self: Sized { self }


        #[doc = r#"
            Transforms this `Read` instance to a `Stream` over its bytes.

            The returned type implements `Stream` where the `Item` is
            `Result<u8, io::Error>`.
            The yielded item is `Ok` if a byte was successfully read and `Err`
            otherwise. EOF is mapped to returning `None` from this iterator.

            # Examples

            [`File`][file]s implement `Read`:

            [file]: ../fs/struct.File.html

            ```no_run
            # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
            #
            use async_std::prelude::*;
            use async_std::fs::File;

            let f = File::open("foo.txt").await?;
            let mut s = f.bytes();

            while let Some(byte) = s.next().await {
                println!("{}", byte.unwrap());
            }
            #
            # Ok(()) }) }
            ```
        "#]
        fn bytes(self) -> bytes::Bytes<Self> where Self: Sized {
            bytes::Bytes { inner: self }
        }

        #[doc = r#"
            Creates an adaptor which will chain this stream with another.

            The returned `Read` instance will first read all bytes from this object
            until EOF is encountered. Afterwards the output is equivalent to the
            output of `next`.

            # Examples

            [`File`][file]s implement `Read`:

            [file]: ../fs/struct.File.html

            ```no_run
            # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
            #
            use async_std::prelude::*;
            use async_std::fs::File;

            let f1 = File::open("foo.txt").await?;
            let f2 = File::open("bar.txt").await?;

            let mut handle = f1.chain(f2);
            let mut buffer = String::new();

            // read the value into a String. We could use any Read method here,
            // this is just one example.
            handle.read_to_string(&mut buffer).await?;
            #
            # Ok(()) }) }
            ```
        "#]
        fn chain<R: Read>(self, next: R) -> chain::Chain<Self, R> where Self: Sized {
            chain::Chain { first: self, second: next, done_first: false }
        }

    }

    impl<T: Read + Unpin + ?Sized> Read for Box<T> {
        fn poll_read(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            buf: &mut [u8],
        ) -> Poll<io::Result<usize>> {
            unreachable!("this impl only appears in the rendered docs")
        }
    }

    impl<T: Read + Unpin + ?Sized> Read for &mut T {
        fn poll_read(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            buf: &mut [u8],
        ) -> Poll<io::Result<usize>> {
            unreachable!("this impl only appears in the rendered docs")
        }
    }

    impl<P> Read for Pin<P>
    where
        P: DerefMut + Unpin,
        <P as Deref>::Target: Read,
    {
        fn poll_read(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            buf: &mut [u8],
        ) -> Poll<io::Result<usize>> {
            unreachable!("this impl only appears in the rendered docs")
        }
    }

    impl Read for &[u8] {
        fn poll_read(
            self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            buf: &mut [u8],
        ) -> Poll<io::Result<usize>> {
            unreachable!("this impl only appears in the rendered docs")
        }
    }
}

/// Initializes a buffer if necessary.
///
/// Currently, a buffer is always initialized because `read_initializer`
/// feature is not stable.
#[inline]
unsafe fn initialize<R: futures_io::AsyncRead>(_reader: &R, buf: &mut [u8]) {
    std::ptr::write_bytes(buf.as_mut_ptr(), 0, buf.len())
}

#[cfg(test)]
mod tests {
    use crate::io;
    use crate::prelude::*;

    #[test]
    fn test_read_by_ref() -> io::Result<()> {
        crate::task::block_on(async {
            let mut f = io::Cursor::new(vec![0u8, 1, 2, 3, 4, 5, 6, 7, 8]);
            let mut buffer = Vec::new();
            let mut other_buffer = Vec::new();

            {
                let reference = f.by_ref();

                // read at most 5 bytes
                assert_eq!(reference.take(5).read_to_end(&mut buffer).await?, 5);
                assert_eq!(&buffer, &[0, 1, 2, 3, 4])
            } // drop our &mut reference so we can use f again

            // original file still usable, read the rest
            assert_eq!(f.read_to_end(&mut other_buffer).await?, 4);
            assert_eq!(&other_buffer, &[5, 6, 7, 8]);
            Ok(())
        })
    }
}