1 | use futures_core::ready; |
2 | use futures_core::task::{Context, Poll}; |
3 | use futures_io::{AsyncRead, IoSliceMut}; |
4 | use std::fmt; |
5 | use std::io; |
6 | use std::pin::Pin; |
7 | |
8 | /// Reader for the [`repeat()`] function. |
9 | #[must_use = "readers do nothing unless polled" ] |
10 | pub struct Repeat { |
11 | byte: u8, |
12 | } |
13 | |
14 | /// Creates an instance of a reader that infinitely repeats one byte. |
15 | /// |
16 | /// All reads from this reader will succeed by filling the specified buffer with |
17 | /// the given byte. |
18 | /// |
19 | /// # Examples |
20 | /// |
21 | /// ``` |
22 | /// # futures::executor::block_on(async { |
23 | /// use futures::io::{self, AsyncReadExt}; |
24 | /// |
25 | /// let mut buffer = [0; 3]; |
26 | /// let mut reader = io::repeat(0b101); |
27 | /// reader.read_exact(&mut buffer).await.unwrap(); |
28 | /// assert_eq!(buffer, [0b101, 0b101, 0b101]); |
29 | /// # Ok::<(), Box<dyn std::error::Error>>(()) }).unwrap(); |
30 | /// ``` |
31 | pub fn repeat(byte: u8) -> Repeat { |
32 | Repeat { byte } |
33 | } |
34 | |
35 | impl AsyncRead for Repeat { |
36 | #[inline ] |
37 | fn poll_read( |
38 | self: Pin<&mut Self>, |
39 | _: &mut Context<'_>, |
40 | buf: &mut [u8], |
41 | ) -> Poll<io::Result<usize>> { |
42 | for slot in &mut *buf { |
43 | *slot = self.byte; |
44 | } |
45 | Poll::Ready(Ok(buf.len())) |
46 | } |
47 | |
48 | #[inline ] |
49 | fn poll_read_vectored( |
50 | mut self: Pin<&mut Self>, |
51 | cx: &mut Context<'_>, |
52 | bufs: &mut [IoSliceMut<'_>], |
53 | ) -> Poll<io::Result<usize>> { |
54 | let mut nwritten = 0; |
55 | for buf in bufs { |
56 | nwritten += ready!(self.as_mut().poll_read(cx, buf))?; |
57 | } |
58 | Poll::Ready(Ok(nwritten)) |
59 | } |
60 | } |
61 | |
62 | impl fmt::Debug for Repeat { |
63 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
64 | f.pad("Repeat { .. }" ) |
65 | } |
66 | } |
67 | |