| 1 | use crate::mem::MaybeUninit; |
| 2 | use crate::{fmt, str}; |
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| 3 | |
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| 4 | /// Used for slow path in `Display` implementations when alignment is required. |
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| 5 | pub(super) struct DisplayBuffer<const SIZE: usize> { |
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| 6 | buf: [MaybeUninit<u8>; SIZE], |
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| 7 | len: usize, |
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| 8 | } |
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| 9 | |
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| 10 | impl<const SIZE: usize> DisplayBuffer<SIZE> { |
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| 11 | #[inline ] |
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| 12 | pub(super) const fn new() -> Self { |
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| 13 | Self { buf: [MaybeUninit::uninit(); SIZE], len: 0 } |
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| 14 | } |
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| 15 | |
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| 16 | #[inline ] |
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| 17 | pub(super) fn as_str(&self) -> &str { |
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| 18 | // SAFETY: `buf` is only written to by the `fmt::Write::write_str` implementation |
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| 19 | // which writes a valid UTF-8 string to `buf` and correctly sets `len`. |
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| 20 | unsafe { |
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| 21 | let s: &[u8] = self.buf[..self.len].assume_init_ref(); |
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| 22 | str::from_utf8_unchecked(s) |
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| 23 | } |
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| 24 | } |
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| 25 | } |
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| 26 | |
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| 27 | impl<const SIZE: usize> fmt::Write for DisplayBuffer<SIZE> { |
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| 28 | fn write_str(&mut self, s: &str) -> fmt::Result { |
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| 29 | let bytes: &[u8] = s.as_bytes(); |
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| 30 | |
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| 31 | if let Some(buf: &mut [MaybeUninit]) = self.buf.get_mut(self.len..(self.len + bytes.len())) { |
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| 32 | buf.write_copy_of_slice(src:bytes); |
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| 33 | self.len += bytes.len(); |
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| 34 | Ok(()) |
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| 35 | } else { |
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| 36 | Err(fmt::Error) |
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| 37 | } |
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| 38 | } |
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| 39 | } |
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| 40 | |
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