ax_io/utils/
empty.rs

1#[cfg(feature = "alloc")]
2use alloc::{string::String, vec::Vec};
3use core::{fmt, io::BorrowedCursor};
4
5use crate::{BufRead, Error, IoBuf, IoBufMut, Read, Result, Seek, SeekFrom, Write};
6
7/// `Empty` ignores any data written via [`Write`], and will always be empty
8/// (returning zero bytes) when read via [`Read`].
9///
10/// This struct is generally created by calling [`empty()`]. Please
11/// see the documentation of [`empty()`] for more details.
12#[non_exhaustive]
13#[derive(Copy, Clone, Debug, Default)]
14pub struct Empty;
15
16/// Creates a value that is always at EOF for reads, and ignores all data written.
17///
18/// See [`std::io::empty()`] for more details.
19#[must_use]
20pub const fn empty() -> Empty {
21    Empty
22}
23
24impl Read for Empty {
25    #[inline]
26    fn read(&mut self, _buf: &mut [u8]) -> Result<usize> {
27        Ok(0)
28    }
29
30    #[inline]
31    fn read_exact(&mut self, buf: &mut [u8]) -> Result<()> {
32        if !buf.is_empty() {
33            Err(Error::UnexpectedEof)
34        } else {
35            Ok(())
36        }
37    }
38
39    #[inline]
40    fn read_buf(&mut self, _cursor: BorrowedCursor<'_>) -> Result<()> {
41        Ok(())
42    }
43
44    #[inline]
45    fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<()> {
46        if cursor.capacity() != 0 {
47            Err(Error::UnexpectedEof)
48        } else {
49            Ok(())
50        }
51    }
52
53    #[inline]
54    #[cfg(feature = "alloc")]
55    fn read_to_end(&mut self, _buf: &mut Vec<u8>) -> Result<usize> {
56        Ok(0)
57    }
58
59    #[inline]
60    #[cfg(feature = "alloc")]
61    fn read_to_string(&mut self, _buf: &mut String) -> Result<usize> {
62        Ok(0)
63    }
64}
65
66impl BufRead for Empty {
67    #[inline]
68    fn fill_buf(&mut self) -> Result<&[u8]> {
69        Ok(&[])
70    }
71
72    #[inline]
73    fn consume(&mut self, _n: usize) {}
74
75    #[inline]
76    fn has_data_left(&mut self) -> Result<bool> {
77        Ok(false)
78    }
79
80    #[inline]
81    fn skip_until(&mut self, _byte: u8) -> Result<usize> {
82        Ok(0)
83    }
84
85    #[inline]
86    #[cfg(feature = "alloc")]
87    fn read_until(&mut self, _byte: u8, _buf: &mut Vec<u8>) -> Result<usize> {
88        Ok(0)
89    }
90
91    #[inline]
92    #[cfg(feature = "alloc")]
93    fn read_line(&mut self, _buf: &mut String) -> Result<usize> {
94        Ok(0)
95    }
96}
97
98impl Seek for Empty {
99    #[inline]
100    fn seek(&mut self, _pos: SeekFrom) -> Result<u64> {
101        Ok(0)
102    }
103
104    #[inline]
105    fn stream_len(&mut self) -> Result<u64> {
106        Ok(0)
107    }
108
109    #[inline]
110    fn stream_position(&mut self) -> Result<u64> {
111        Ok(0)
112    }
113}
114
115impl Write for Empty {
116    #[inline]
117    fn write(&mut self, buf: &[u8]) -> Result<usize> {
118        Ok(buf.len())
119    }
120
121    #[inline]
122    fn write_all(&mut self, _buf: &[u8]) -> Result<()> {
123        Ok(())
124    }
125
126    #[inline]
127    fn write_fmt(&mut self, _args: fmt::Arguments<'_>) -> Result<()> {
128        Ok(())
129    }
130
131    #[inline]
132    fn flush(&mut self) -> Result<()> {
133        Ok(())
134    }
135}
136
137impl Write for &Empty {
138    #[inline]
139    fn write(&mut self, buf: &[u8]) -> Result<usize> {
140        Ok(buf.len())
141    }
142
143    #[inline]
144    fn write_all(&mut self, _buf: &[u8]) -> Result<()> {
145        Ok(())
146    }
147
148    #[inline]
149    fn write_fmt(&mut self, _args: fmt::Arguments<'_>) -> Result<()> {
150        Ok(())
151    }
152
153    #[inline]
154    fn flush(&mut self) -> Result<()> {
155        Ok(())
156    }
157}
158
159impl IoBuf for Empty {
160    #[inline]
161    fn remaining(&self) -> usize {
162        0
163    }
164}
165
166impl IoBufMut for Empty {
167    #[inline]
168    fn remaining_mut(&self) -> usize {
169        usize::MAX
170    }
171}
ax_io/utils/empty.rs

ax_io/utils/
empty.rs
