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
|
use futures_core::task::{Context, Poll};
use futures_io::{AsyncBufRead, AsyncRead, AsyncSeek, AsyncWrite, IoSlice, IoSliceMut, SeekFrom};
use std::io;
use std::pin::Pin;
/// A `Cursor` wraps an in-memory buffer and provides it with a
/// [`AsyncSeek`] implementation.
///
/// `Cursor`s are used with in-memory buffers, anything implementing
/// `AsRef<[u8]>`, to allow them to implement [`AsyncRead`] and/or [`AsyncWrite`],
/// allowing these buffers to be used anywhere you might use a reader or writer
/// that does actual I/O.
///
/// This library implements some I/O traits on various types which
/// are commonly used as a buffer, like `Cursor<`[`Vec`]`<u8>>` and
/// `Cursor<`[`&[u8]`][bytes]`>`.
///
/// [`AsyncSeek`]: trait.AsyncSeek.html
/// [`AsyncRead`]: trait.AsyncRead.html
/// [`AsyncWrite`]: trait.AsyncWrite.html
/// [bytes]: https://doc.rust-lang.org/std/primitive.slice.html
#[derive(Clone, Debug, Default)]
pub struct Cursor<T> {
inner: io::Cursor<T>,
}
impl<T> Cursor<T> {
/// Creates a new cursor wrapping the provided underlying in-memory buffer.
///
/// Cursor initial position is `0` even if underlying buffer (e.g., `Vec`)
/// is not empty. So writing to cursor starts with overwriting `Vec`
/// content, not with appending to it.
///
/// # Examples
///
/// ```
/// use futures::io::Cursor;
///
/// let buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
/// ```
pub fn new(inner: T) -> Self {
Self { inner: io::Cursor::new(inner) }
}
/// Consumes this cursor, returning the underlying value.
///
/// # Examples
///
/// ```
/// use futures::io::Cursor;
///
/// let buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
///
/// let vec = buff.into_inner();
/// ```
pub fn into_inner(self) -> T {
self.inner.into_inner()
}
/// Gets a reference to the underlying value in this cursor.
///
/// # Examples
///
/// ```
/// use futures::io::Cursor;
///
/// let buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
///
/// let reference = buff.get_ref();
/// ```
pub fn get_ref(&self) -> &T {
self.inner.get_ref()
}
/// Gets a mutable reference to the underlying value in this cursor.
///
/// Care should be taken to avoid modifying the internal I/O state of the
/// underlying value as it may corrupt this cursor's position.
///
/// # Examples
///
/// ```
/// use futures::io::Cursor;
///
/// let mut buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
///
/// let reference = buff.get_mut();
/// ```
pub fn get_mut(&mut self) -> &mut T {
self.inner.get_mut()
}
/// Returns the current position of this cursor.
///
/// # Examples
///
/// ```
/// # futures::executor::block_on(async {
/// use futures::io::{AsyncSeekExt, Cursor, SeekFrom};
///
/// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
///
/// assert_eq!(buff.position(), 0);
///
/// buff.seek(SeekFrom::Current(2)).await?;
/// assert_eq!(buff.position(), 2);
///
/// buff.seek(SeekFrom::Current(-1)).await?;
/// assert_eq!(buff.position(), 1);
/// # Ok::<(), Box<dyn std::error::Error>>(()) }).unwrap();
/// ```
pub fn position(&self) -> u64 {
self.inner.position()
}
/// Sets the position of this cursor.
///
/// # Examples
///
/// ```
/// use futures::io::Cursor;
///
/// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
///
/// assert_eq!(buff.position(), 0);
///
/// buff.set_position(2);
/// assert_eq!(buff.position(), 2);
///
/// buff.set_position(4);
/// assert_eq!(buff.position(), 4);
/// ```
pub fn set_position(&mut self, pos: u64) {
self.inner.set_position(pos)
}
}
impl<T> AsyncSeek for Cursor<T>
where
T: AsRef<[u8]> + Unpin,
{
fn poll_seek(
mut self: Pin<&mut Self>,
_: &mut Context<'_>,
pos: SeekFrom,
) -> Poll<io::Result<u64>> {
Poll::Ready(io::Seek::seek(&mut self.inner, pos))
}
}
impl<T: AsRef<[u8]> + Unpin> AsyncRead for Cursor<T> {
fn poll_read(
mut self: Pin<&mut Self>,
_cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<io::Result<usize>> {
Poll::Ready(io::Read::read(&mut self.inner, buf))
}
fn poll_read_vectored(
mut self: Pin<&mut Self>,
_: &mut Context<'_>,
bufs: &mut [IoSliceMut<'_>],
) -> Poll<io::Result<usize>> {
Poll::Ready(io::Read::read_vectored(&mut self.inner, bufs))
}
}
impl<T> AsyncBufRead for Cursor<T>
where
T: AsRef<[u8]> + Unpin,
{
fn poll_fill_buf(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<&[u8]>> {
Poll::Ready(io::BufRead::fill_buf(&mut self.get_mut().inner))
}
fn consume(mut self: Pin<&mut Self>, amt: usize) {
io::BufRead::consume(&mut self.inner, amt)
}
}
macro_rules! delegate_async_write_to_stdio {
() => {
fn poll_write(
mut self: Pin<&mut Self>,
_: &mut Context<'_>,
buf: &[u8],
) -> Poll<io::Result<usize>> {
Poll::Ready(io::Write::write(&mut self.inner, buf))
}
fn poll_write_vectored(
mut self: Pin<&mut Self>,
_: &mut Context<'_>,
bufs: &[IoSlice<'_>],
) -> Poll<io::Result<usize>> {
Poll::Ready(io::Write::write_vectored(&mut self.inner, bufs))
}
fn poll_flush(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
Poll::Ready(io::Write::flush(&mut self.inner))
}
fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
self.poll_flush(cx)
}
};
}
impl AsyncWrite for Cursor<&mut [u8]> {
delegate_async_write_to_stdio!();
}
impl AsyncWrite for Cursor<&mut Vec<u8>> {
delegate_async_write_to_stdio!();
}
impl AsyncWrite for Cursor<Vec<u8>> {
delegate_async_write_to_stdio!();
}
impl AsyncWrite for Cursor<Box<[u8]>> {
delegate_async_write_to_stdio!();
}
|
