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deque: Add front, front_mut, back, back_mut.

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This commit is contained in:
Dario Nieuwenhuis 2021-08-08 21:24:41 +02:00
parent a11ed8c33e
commit e292ca4486
1 changed files with 71 additions and 0 deletions
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71
src/deque.rs
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@ -191,6 +191,44 @@ impl<T, const N: usize> Deque<T, N> {
}
}
/// Provides a reference to the front element, or None if the `Deque` is empty.
pub fn front(&self) -> Option<&T> {
if self.is_empty() {
None
} else {
Some(unsafe { &*self.buffer.get_unchecked(self.front).as_ptr() })
}
}
/// Provides a mutable reference to the front element, or None if the `Deque` is empty.
pub fn front_mut(&mut self) -> Option<&mut T> {
if self.is_empty() {
None
} else {
Some(unsafe { &mut *self.buffer.get_unchecked_mut(self.front).as_mut_ptr() })
}
}
/// Provides a reference to the back element, or None if the `Deque` is empty.
pub fn back(&self) -> Option<&T> {
if self.is_empty() {
None
} else {
let index = Self::decrement(self.back);
Some(unsafe { &*self.buffer.get_unchecked(index).as_ptr() })
}
}
/// Provides a mutable reference to the back element, or None if the `Deque` is empty.
pub fn back_mut(&mut self) -> Option<&mut T> {
if self.is_empty() {
None
} else {
let index = Self::decrement(self.back);
Some(unsafe { &mut *self.buffer.get_unchecked_mut(index).as_mut_ptr() })
}
}
/// Removes the item from the front of the deque and returns it, or `None` if it's empty
pub fn pop_front(&mut self) -> Option<T> {
if self.is_empty() {
@ -606,6 +644,39 @@ mod tests {
assert!(v.is_empty());
}
#[test]
fn front_back() {
let mut v: Deque<i32, 4> = Deque::new();
assert_eq!(v.front(), None);
assert_eq!(v.front_mut(), None);
assert_eq!(v.back(), None);
assert_eq!(v.back_mut(), None);
v.push_back(4).unwrap();
assert_eq!(v.front(), Some(&4));
assert_eq!(v.front_mut(), Some(&mut 4));
assert_eq!(v.back(), Some(&4));
assert_eq!(v.back_mut(), Some(&mut 4));
v.push_front(3).unwrap();
assert_eq!(v.front(), Some(&3));
assert_eq!(v.front_mut(), Some(&mut 3));
assert_eq!(v.back(), Some(&4));
assert_eq!(v.back_mut(), Some(&mut 4));
v.pop_back().unwrap();
assert_eq!(v.front(), Some(&3));
assert_eq!(v.front_mut(), Some(&mut 3));
assert_eq!(v.back(), Some(&3));
assert_eq!(v.back_mut(), Some(&mut 3));
v.pop_front().unwrap();
assert_eq!(v.front(), None);
assert_eq!(v.front_mut(), None);
assert_eq!(v.back(), None);
assert_eq!(v.back_mut(), None);
}
#[test]
fn iter() {
let mut v: Deque<i32, 4> = Deque::new();