core/net/
display_buffer.rs

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<'a> {
6    buf: &'a mut [MaybeUninit<u8>],
7    len: usize,
8}
9
10impl<'a> DisplayBuffer<'a> {
11    #[inline]
12    pub(super) const fn new(buf: &'a mut [MaybeUninit<u8>]) -> Self {
13        Self { buf, len: 0 }
14    }
15
16    #[inline]
17    pub(super) const fn buffer<const SIZE: usize>() -> [MaybeUninit<u8>; SIZE] {
18        [MaybeUninit::uninit(); SIZE]
19    }
20
21    #[inline]
22    pub(super) fn as_str(&self) -> &str {
23        // SAFETY: `buf` is only written to by the `fmt::Write::write_str` implementation
24        // which writes a valid UTF-8 string to `buf` and correctly sets `len`.
25        unsafe {
26            let s = self.buf[..self.len].assume_init_ref();
27            str::from_utf8_unchecked(s)
28        }
29    }
30}
31
32impl fmt::Write for DisplayBuffer<'_> {
33    fn write_str(&mut self, s: &str) -> fmt::Result {
34        let bytes = s.as_bytes();
35
36        if let Some(buf) = self.buf.get_mut(self.len..(self.len + bytes.len())) {
37            buf.write_copy_of_slice(bytes);
38            self.len += bytes.len();
39            Ok(())
40        } else {
41            Err(fmt::Error)
42        }
43    }
44}
core/net/display_buffer.rs

core/net/
display_buffer.rs
