1 | use crate::io::util::read_line::finish_string_read; |
2 | use crate::io::util::read_to_end::read_to_end_internal; |
3 | use crate::io::util::vec_with_initialized::VecWithInitialized; |
4 | use crate::io::AsyncRead; |
5 | |
6 | use pin_project_lite::pin_project; |
7 | use std::future::Future; |
8 | use std::marker::PhantomPinned; |
9 | use std::pin::Pin; |
10 | use std::task::{Context, Poll}; |
11 | use std::{io, mem}; |
12 | |
13 | pin_project! { |
14 | /// Future for the [`read_to_string`](super::AsyncReadExt::read_to_string) method. |
15 | #[derive(Debug)] |
16 | #[must_use = "futures do nothing unless you `.await` or poll them" ] |
17 | pub struct ReadToString<'a, R: ?Sized> { |
18 | reader: &'a mut R, |
19 | // This is the buffer we were provided. It will be replaced with an empty string |
20 | // while reading to postpone utf-8 handling until after reading. |
21 | output: &'a mut String, |
22 | // The actual allocation of the string is moved into this vector instead. |
23 | buf: VecWithInitialized<Vec<u8>>, |
24 | // The number of bytes appended to buf. This can be less than buf.len() if |
25 | // the buffer was not empty when the operation was started. |
26 | read: usize, |
27 | // Make this future `!Unpin` for compatibility with async trait methods. |
28 | #[pin] |
29 | _pin: PhantomPinned, |
30 | } |
31 | } |
32 | |
33 | pub(crate) fn read_to_string<'a, R>( |
34 | reader: &'a mut R, |
35 | string: &'a mut String, |
36 | ) -> ReadToString<'a, R> |
37 | where |
38 | R: AsyncRead + ?Sized + Unpin, |
39 | { |
40 | let buf = mem::take(string).into_bytes(); |
41 | ReadToString { |
42 | reader, |
43 | buf: VecWithInitialized::new(buf), |
44 | output: string, |
45 | read: 0, |
46 | _pin: PhantomPinned, |
47 | } |
48 | } |
49 | |
50 | fn read_to_string_internal<R: AsyncRead + ?Sized>( |
51 | reader: Pin<&mut R>, |
52 | output: &mut String, |
53 | buf: &mut VecWithInitialized<Vec<u8>>, |
54 | read: &mut usize, |
55 | cx: &mut Context<'_>, |
56 | ) -> Poll<io::Result<usize>> { |
57 | let io_res = ready!(read_to_end_internal(buf, reader, read, cx)); |
58 | let utf8_res = String::from_utf8(buf.take()); |
59 | |
60 | // At this point both buf and output are empty. The allocation is in utf8_res. |
61 | |
62 | debug_assert!(buf.is_empty()); |
63 | debug_assert!(output.is_empty()); |
64 | finish_string_read(io_res, utf8_res, *read, output, true) |
65 | } |
66 | |
67 | impl<A> Future for ReadToString<'_, A> |
68 | where |
69 | A: AsyncRead + ?Sized + Unpin, |
70 | { |
71 | type Output = io::Result<usize>; |
72 | |
73 | fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { |
74 | let me = self.project(); |
75 | |
76 | read_to_string_internal(Pin::new(*me.reader), me.output, me.buf, me.read, cx) |
77 | } |
78 | } |
79 | |