1 | use futures_core::future::Future; |
2 | use futures_core::ready; |
3 | use futures_core::task::{Context, Poll}; |
4 | use futures_io::AsyncRead; |
5 | use std::io; |
6 | use std::pin::Pin; |
7 | use std::vec::Vec; |
8 | |
9 | /// Future for the [`read_to_end`](super::AsyncReadExt::read_to_end) method. |
10 | #[derive (Debug)] |
11 | #[must_use = "futures do nothing unless you `.await` or poll them" ] |
12 | pub struct ReadToEnd<'a, R: ?Sized> { |
13 | reader: &'a mut R, |
14 | buf: &'a mut Vec<u8>, |
15 | start_len: usize, |
16 | } |
17 | |
18 | impl<R: ?Sized + Unpin> Unpin for ReadToEnd<'_, R> {} |
19 | |
20 | impl<'a, R: AsyncRead + ?Sized + Unpin> ReadToEnd<'a, R> { |
21 | pub(super) fn new(reader: &'a mut R, buf: &'a mut Vec<u8>) -> Self { |
22 | let start_len: usize = buf.len(); |
23 | Self { reader, buf, start_len } |
24 | } |
25 | } |
26 | |
27 | struct Guard<'a> { |
28 | buf: &'a mut Vec<u8>, |
29 | len: usize, |
30 | } |
31 | |
32 | impl Drop for Guard<'_> { |
33 | fn drop(&mut self) { |
34 | unsafe { |
35 | self.buf.set_len(self.len); |
36 | } |
37 | } |
38 | } |
39 | |
40 | // This uses an adaptive system to extend the vector when it fills. We want to |
41 | // avoid paying to allocate and zero a huge chunk of memory if the reader only |
42 | // has 4 bytes while still making large reads if the reader does have a ton |
43 | // of data to return. Simply tacking on an extra DEFAULT_BUF_SIZE space every |
44 | // time is 4,500 times (!) slower than this if the reader has a very small |
45 | // amount of data to return. |
46 | // |
47 | // Because we're extending the buffer with uninitialized data for trusted |
48 | // readers, we need to make sure to truncate that if any of this panics. |
49 | pub(super) fn read_to_end_internal<R: AsyncRead + ?Sized>( |
50 | mut rd: Pin<&mut R>, |
51 | cx: &mut Context<'_>, |
52 | buf: &mut Vec<u8>, |
53 | start_len: usize, |
54 | ) -> Poll<io::Result<usize>> { |
55 | let mut g = Guard { len: buf.len(), buf }; |
56 | loop { |
57 | if g.len == g.buf.len() { |
58 | unsafe { |
59 | g.buf.reserve(32); |
60 | let capacity = g.buf.capacity(); |
61 | g.buf.set_len(capacity); |
62 | super::initialize(&rd, &mut g.buf[g.len..]); |
63 | } |
64 | } |
65 | |
66 | let buf = &mut g.buf[g.len..]; |
67 | match ready!(rd.as_mut().poll_read(cx, buf)) { |
68 | Ok(0) => return Poll::Ready(Ok(g.len - start_len)), |
69 | Ok(n) => { |
70 | // We can't allow bogus values from read. If it is too large, the returned vec could have its length |
71 | // set past its capacity, or if it overflows the vec could be shortened which could create an invalid |
72 | // string if this is called via read_to_string. |
73 | assert!(n <= buf.len()); |
74 | g.len += n; |
75 | } |
76 | Err(e) => return Poll::Ready(Err(e)), |
77 | } |
78 | } |
79 | } |
80 | |
81 | impl<A> Future for ReadToEnd<'_, A> |
82 | where |
83 | A: AsyncRead + ?Sized + Unpin, |
84 | { |
85 | type Output = io::Result<usize>; |
86 | |
87 | fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { |
88 | let this: &mut ReadToEnd<'_, A> = &mut *self; |
89 | read_to_end_internal(rd:Pin::new(&mut this.reader), cx, this.buf, this.start_len) |
90 | } |
91 | } |
92 | |