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mod inner;
#[cfg(test)]
mod tests;
use std::{fmt, mem};
use self::inner::{Link, Slot};
#[derive(Clone, Default)]
pub struct IndexQueue {
slots: Vec<Slot>,
ends: Slot,
}
impl IndexQueue {
pub fn is_empty(&self) -> bool {
self.ends.is_empty()
}
pub fn contains(&self, index: usize) -> bool {
match self.slots.get(index) {
Some(slot) => !slot.is_empty(),
_ => false,
}
}
pub fn remove(&mut self, index: usize) -> bool {
let slot = match self.slots.get_mut(index) {
None => return false,
Some(slot) => mem::replace(slot, Slot::default()),
};
match slot.as_ref() {
None => return false,
Some(&Link { prev, next }) => {
let ends = self.ends.unwrap_mut();
if ends.prev != ends.next {
if index == ends.next {
ends.next = next;
} else {
self.slots[prev].unwrap_mut().next = next;
}
if index == ends.prev {
ends.prev = prev;
} else {
self.slots[next].unwrap_mut().prev = prev;
}
return true;
}
}
}
self.ends.clear();
true
}
pub fn push_back(&mut self, index: usize) -> bool {
loop {
match self.slots.get_mut(index) {
Some(ref slot) if !slot.is_empty() => return false,
Some(slot) => {
*slot = Slot::from(Link {
next: 0,
prev: self.ends.as_ref().map(|link| link.prev)
.unwrap_or( 0),
});
break;
}
None => {}
}
self.slots.push(Slot::default())
}
match self.ends.as_mut_ref() {
None => {}
Some(ends) => {
let back = mem::replace(&mut ends.prev, index);
self.slots[back].unwrap_mut().next = index;
return true;
}
}
self.ends = Slot::from(Link { prev: index, next: index });
true
}
pub fn pop_front(&mut self) -> Option<usize> {
let (is_last, popped) = {
let (is_last, popped, front) = match self.ends.as_mut_ref() {
None => return None,
Some(ends) => {
let is_last = ends.prev == ends.next;
let popped = ends.next;
(is_last, popped, &mut ends.next)
}
};
let slot = &mut self.slots[*front];
let next = slot.unwrap().next;
slot.clear();
if !is_last {
*front = next;
}
(is_last, popped)
};
if is_last {
self.ends.clear();
}
Some(popped)
}
}
impl fmt::Debug for IndexQueue {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let mut queue = self.clone();
let mut items = Vec::new();
while let Some(i) = queue.pop_front() {
items.push(i);
}
f.debug_tuple("IndexQueue").field(&items).finish()
}
}