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
|
use crate::io::AsyncRead;
use std::future::Future;
use std::io;
use std::mem::MaybeUninit;
use std::pin::Pin;
use std::task::{Context, Poll};
#[derive(Debug)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
#[cfg_attr(docsrs, doc(cfg(feature = "io-util")))]
pub struct ReadToEnd<'a, R: ?Sized> {
reader: &'a mut R,
buf: &'a mut Vec<u8>,
start_len: usize,
}
pub(crate) fn read_to_end<'a, R>(reader: &'a mut R, buf: &'a mut Vec<u8>) -> ReadToEnd<'a, R>
where
R: AsyncRead + Unpin + ?Sized,
{
let start_len = buf.len();
ReadToEnd {
reader,
buf,
start_len,
}
}
struct Guard<'a> {
buf: &'a mut Vec<u8>,
len: usize,
}
impl Drop for Guard<'_> {
fn drop(&mut self) {
unsafe {
self.buf.set_len(self.len);
}
}
}
// This uses an adaptive system to extend the vector when it fills. We want to
// avoid paying to allocate and zero a huge chunk of memory if the reader only
// has 4 bytes while still making large reads if the reader does have a ton
// of data to return. Simply tacking on an extra DEFAULT_BUF_SIZE space every
// time is 4,500 times (!) slower than this if the reader has a very small
// amount of data to return.
//
// Because we're extending the buffer with uninitialized data for trusted
// readers, we need to make sure to truncate that if any of this panics.
pub(super) fn read_to_end_internal<R: AsyncRead + ?Sized>(
mut rd: Pin<&mut R>,
cx: &mut Context<'_>,
buf: &mut Vec<u8>,
start_len: usize,
) -> Poll<io::Result<usize>> {
let mut g = Guard {
len: buf.len(),
buf,
};
let ret;
loop {
if g.len == g.buf.len() {
unsafe {
g.buf.reserve(32);
let capacity = g.buf.capacity();
g.buf.set_len(capacity);
let b = &mut *(&mut g.buf[g.len..] as *mut [u8] as *mut [MaybeUninit<u8>]);
rd.prepare_uninitialized_buffer(b);
}
}
match ready!(rd.as_mut().poll_read(cx, &mut g.buf[g.len..])) {
Ok(0) => {
ret = Poll::Ready(Ok(g.len - start_len));
break;
}
Ok(n) => g.len += n,
Err(e) => {
ret = Poll::Ready(Err(e));
break;
}
}
}
ret
}
impl<A> Future for ReadToEnd<'_, A>
where
A: AsyncRead + ?Sized + Unpin,
{
type Output = io::Result<usize>;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let this = &mut *self;
read_to_end_internal(Pin::new(&mut this.reader), cx, this.buf, this.start_len)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn assert_unpin() {
use std::marker::PhantomPinned;
crate::is_unpin::<ReadToEnd<'_, PhantomPinned>>();
}
}
|
