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Implement slice::{Iter, IterMut}::{advance_by, advance_back_by}

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Co-authored-by: The8472 <git@infinite-source.de>
This commit is contained in:
Tim Vermeulen 2020-10-02 02:46:19 +02:00 • committed by The8472
parent e742158ef5
commit 2b89914962
1 changed files with 16 additions and 0 deletions
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16
library/core/src/slice/iter/macros.rs
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@ -185,6 +185,14 @@ macro_rules! iterator {
}
}
#[inline]
fn advance_by(&mut self, n: usize) -> Result<(), usize>{
let advance = cmp::min(n, len!(self));
// SAFETY: `advance` does not exceed `self.len()` by construction
unsafe { self.post_inc_start(advance as isize) };
if advance == n { Ok(()) } else { Err(advance) }
}
#[inline]
fn last(mut self) -> Option<$elem> {
self.next_back()
@ -371,6 +379,14 @@ macro_rules! iterator {
Some(next_back_unchecked!(self))
}
}
#[inline]
fn advance_back_by(&mut self, n: usize) -> Result<(), usize> {
let advance = cmp::min(n, len!(self));
// SAFETY: `advance` does not exceed `self.len()` by construction
unsafe { self.pre_dec_end(advance as isize) };
if advance == n { Ok(()) } else { Err(advance) }
}
}
#[stable(feature = "fused", since = "1.26.0")]