1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
|
use core::ops::{Deref, DerefMut};
use super::Vec;
use crate::fmt;
/// Structure wrapping a mutable reference to the last item in a
/// `Vec`.
///
/// This `struct` is created by the [`peek_mut`] method on [`Vec`]. See
/// its documentation for more.
///
/// [`peek_mut`]: Vec::peek_mut
#[unstable(feature = "vec_peek_mut", issue = "122742")]
pub struct PeekMut<'a, T> {
vec: &'a mut Vec<T>,
}
#[unstable(feature = "vec_peek_mut", issue = "122742")]
impl<T: fmt::Debug> fmt::Debug for PeekMut<'_, T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("PeekMut").field(self.deref()).finish()
}
}
impl<'a, T> PeekMut<'a, T> {
pub(crate) fn new(vec: &'a mut Vec<T>) -> Option<Self> {
if vec.is_empty() { None } else { Some(Self { vec }) }
}
/// Removes the peeked value from the vector and returns it.
#[unstable(feature = "vec_peek_mut", issue = "122742")]
pub fn pop(self) -> T {
// SAFETY: PeekMut is only constructed if the vec is non-empty
unsafe { self.vec.pop().unwrap_unchecked() }
}
}
#[unstable(feature = "vec_peek_mut", issue = "122742")]
impl<'a, T> Deref for PeekMut<'a, T> {
type Target = T;
fn deref(&self) -> &Self::Target {
// SAFETY: PeekMut is only constructed if the vec is non-empty
unsafe { self.vec.get_unchecked(self.vec.len() - 1) }
}
}
#[unstable(feature = "vec_peek_mut", issue = "122742")]
impl<'a, T> DerefMut for PeekMut<'a, T> {
fn deref_mut(&mut self) -> &mut Self::Target {
let idx = self.vec.len() - 1;
// SAFETY: PeekMut is only constructed if the vec is non-empty
unsafe { self.vec.get_unchecked_mut(idx) }
}
}
|
