display_buffer.rs - source
Description: Source of the Rust file `library/core/src/net/display_buffer.rs`.

#
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<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}