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use std::convert::TryInto;
use std::iter::{Enumerate, ExactSizeIterator, FusedIterator};
use std::slice;
use crate::arena::{Entry, Index};
/// See [`Arena::iter_mut`][Arena::iter_mut].
pub struct IterMut<'a, T> {
pub(crate) len: u32,
pub(crate) inner: Enumerate<slice::IterMut<'a, Entry<T>>>,
}
impl<'a, T> Iterator for IterMut<'a, T> {
type Item = (Index, &'a T);
fn next(&mut self) -> Option<Self::Item> {
loop {
if self.len == 0 {
return None;
}
match self.inner.next()? {
(_, Entry::Empty(_)) => continue,
(slot, Entry::Occupied(occupied)) => {
self.len = self
.len
.checked_sub(1)
.unwrap_or_else(|| unreachable!("Underflowed u32 trying to iterate Arena"));
let slot: u32 = slot
.try_into()
.unwrap_or_else(|_| unreachable!("Overflowed u32 trying to iterate Arena"));
let index = Index {
slot,
generation: occupied.generation,
};
return Some((index, &mut occupied.value));
}
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
(self.len as usize, Some(self.len as usize))
}
}
impl<'a, T> FusedIterator for IterMut<'a, T> {}
impl<'a, T> ExactSizeIterator for IterMut<'a, T> {}
#[cfg(test)]
mod test {
use crate::Arena;
use std::collections::HashSet;
#[test]
fn iter_mut() {
let mut arena = Arena::with_capacity(2);
let one = arena.insert(1);
let two = arena.insert(2);
let mut pairs = HashSet::new();
let mut iter = arena.iter_mut();
assert_eq!(iter.size_hint(), (2, Some(2)));
pairs.insert(iter.next().unwrap());
assert_eq!(iter.size_hint(), (1, Some(1)));
pairs.insert(iter.next().unwrap());
assert_eq!(iter.size_hint(), (0, Some(0)));
assert_eq!(iter.next(), None);
assert_eq!(iter.next(), None);
assert_eq!(iter.size_hint(), (0, Some(0)));
assert!(pairs.contains(&(one, &1)));
assert!(pairs.contains(&(two, &2)));
}
}
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