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use super::Entity;
pub struct SparseSet<T> {
pub dense: Vec<T>,
pub entities: Vec<Entity>,
pub sparse: Vec<Option<usize>>,
}
impl<T> SparseSet<T> {
pub fn new() -> Self {
Self {
dense: Vec::new(),
entities: Vec::new(),
sparse: Vec::new(),
}
}
pub fn insert(&mut self, entity: Entity, component: T) {
if self.sparse.len() <= entity {
self.sparse.resize(entity + 1, None);
}
self.dense.push(component);
self.entities.push(entity);
let id = self.dense.len() - 1;
self.sparse[entity] = Some(id);
}
pub fn remove(&mut self, entity: Entity) {
let Some(id) = self.sparse.get(entity).copied().flatten() else {
return;
};
let Some(last) = self.entities.last().copied() else {
return;
};
self.dense.swap_remove(id);
self.entities.swap_remove(id);
self.sparse[last] = Some(id);
self.sparse[entity] = None;
}
pub fn iter(&self) -> impl Iterator<Item = (Entity, &T)> {
self.entities.iter().copied().zip(self.dense.iter())
}
pub fn iter_mut(&mut self) -> impl Iterator<Item = (Entity, &mut T)> {
self.entities.iter().copied().zip(self.dense.iter_mut())
}
pub fn get(&self, entity: Entity) -> Option<&T> {
if let Some(id) = self.sparse.get(entity) {
match id {
Some(id) => self.dense.get(*id),
None => None,
}
} else {
None
}
}
pub fn get_mut(&mut self, entity: Entity) -> Option<&mut T> {
if let Some(id) = self.sparse.get(entity) {
match id {
Some(id) => self.dense.get_mut(*id),
None => None,
}
} else {
None
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_remove() {
let mut set = SparseSet::<i32>::new();
set.insert(3, 300);
set.insert(2, 200);
set.insert(4, 400);
set.insert(7, 700);
set.remove(4);
assert!(set.get(7).copied() == Some(700));
assert!(set.get(3).copied() == Some(300));
assert!(set.get(2).copied() == Some(200));
assert!(set.get(4).copied().is_none());
set.remove(7);
assert!(set.get(7).copied().is_none());
assert!(set.get(3).copied() == Some(300));
assert!(set.get(2).copied() == Some(200));
assert!(set.get(4).copied().is_none());
}
}
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