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use std::{
slice,
};
pub struct Iter<'a, T> {
data: &'a Vec<T>,
iter: slice::Iter<'a, usize>,
}
impl<'a, T> Iterator for Iter<'a, T> {
type Item = &'a T;
fn next(&mut self) -> Option<Self::Item> {
let offset = self.iter.next()?;
unsafe {
Some(self.data.get_unchecked(*offset))
}
}
}
pub struct IterMut<'a, T> {
data: &'a mut Vec<T>,
iter: slice::Iter<'a, usize>,
}
impl<'a, T> Iterator for IterMut<'a, T> {
type Item = &'a mut T;
fn next(&mut self) -> Option<Self::Item> {
use std::mem;
let offset = self.iter.next()?;
unsafe {
Some(mem::transmute(self.data.get_unchecked_mut(*offset)))
}
}
}
pub struct Pool<T: Default> {
data: Vec<T>,
offsets: Vec<usize>,
alive_ct: usize,
}
impl<T: Default> Pool<T> {
pub fn new(size: usize) -> Self {
let mut data: Vec<T> = Vec::with_capacity(size);
for _ in 0..size {
data.push(T::default());
}
let mut offsets = Vec::with_capacity(size);
for i in 0..size {
offsets.push(i);
}
Self {
data,
offsets,
alive_ct: 0,
}
}
#[inline]
pub fn spawn(&mut self) -> Option<&mut T> {
if self.is_empty() {
None
} else {
Some(unsafe { self.spawn_unchecked() })
}
}
#[inline]
pub fn please_spawn(&mut self) -> &mut T {
if self.is_empty() {
self.offsets.push(self.data.len());
self.data.push(T::default());
}
unsafe { self.spawn_unchecked() }
}
#[inline]
unsafe fn get_at_offset(&mut self, at: usize) -> &mut T {
self.data.get_unchecked_mut(self.offsets[at])
}
pub unsafe fn spawn_unchecked(&mut self) -> &mut T {
let at = self.alive_ct;
self.alive_ct += 1;
self.get_at_offset(at)
}
pub fn reclaim<F: FnMut(&T) -> bool>(&mut self, mut kill_fn: F) {
let mut alive_ct = self.alive_ct;
let mut i = 0;
loop {
if i >= alive_ct {
break;
}
if kill_fn(unsafe { self.get_at_offset(i) }) {
alive_ct -= 1;
self.offsets.swap(i, alive_ct);
}
i += 1;
}
self.alive_ct = alive_ct;
}
pub fn iter(&self) -> Iter<T> {
Iter {
data: &self.data,
iter: (&self.offsets[..self.alive_ct]).iter(),
}
}
pub fn iter_mut(&mut self) -> IterMut<T> {
IterMut {
data: &mut self.data,
iter: (&self.offsets[..self.alive_ct]).iter(),
}
}
pub fn sort_the_dead(&mut self) {
if self.available() >= 2 {
self.offsets[self.alive_ct..].sort_unstable();
}
}
#[inline]
pub fn is_empty(&self) -> bool {
self.available() == 0
}
#[inline]
pub fn available(&self) -> usize {
self.offsets.len() - self.alive_ct
}
}
pub trait Recyclable: Default {
fn reset(&mut self);
}
impl<T: Recyclable> Pool<T> {
pub fn spawn_new(&mut self) -> Option<&mut T> {
let obj = self.spawn()?;
obj.reset();
Some(obj)
}
pub unsafe fn spawn_new_unchecked(&mut self) -> &mut T {
let obj = self.spawn_unchecked();
obj.reset();
obj
}
}