core/net/
display_buffer.rs

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1use crate::mem::MaybeUninit;
2use crate::{fmt, str};
3
4/// Used for slow path in `Display` implementations when alignment is required.
5pub(super) struct DisplayBuffer<const SIZE: usize> {
6    buf: [MaybeUninit<u8>; SIZE],
7    len: usize,
8}
9
10impl<const SIZE: usize> DisplayBuffer<SIZE> {
11    #[inline]
12    pub(super) const fn new() -> Self {
13        Self { buf: [MaybeUninit::uninit(); SIZE], len: 0 }
14    }
15
16    #[inline]
17    pub(super) fn as_str(&self) -> &str {
18        // SAFETY: `buf` is only written to by the `fmt::Write::write_str` implementation
19        // which writes a valid UTF-8 string to `buf` and correctly sets `len`.
20        unsafe {
21            let s = self.buf[..self.len].assume_init_ref();
22            str::from_utf8_unchecked(s)
23        }
24    }
25}
26
27impl<const SIZE: usize> fmt::Write for DisplayBuffer<SIZE> {
28    fn write_str(&mut self, s: &str) -> fmt::Result {
29        let bytes = s.as_bytes();
30
31        if let Some(buf) = self.buf.get_mut(self.len..(self.len + bytes.len())) {
32            buf.write_copy_of_slice(bytes);
33            self.len += bytes.len();
34            Ok(())
35        } else {
36            Err(fmt::Error)
37        }
38    }
39}
core/net/display_buffer.rs

core/net/
display_buffer.rs
