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use crate::{BuddyCollection, BuddyLine, OligarchyCollection, Order};
use core::{fmt, ptr::NonNull};
pub struct LinkedListBuddy {
free_list: Node,
order: Order,
}
unsafe impl Send for LinkedListBuddy {}
impl BuddyLine for LinkedListBuddy {
const INTRUSIVE_META_SIZE: usize = core::mem::size_of::<Node>();
const EMPTY: Self = Self {
free_list: Node { next: None },
order: Order::new(0),
};
#[inline]
fn init(&mut self, order: usize, _base: usize) {
self.order = Order::new(order);
}
fn take(&mut self, _idx: usize) -> bool {
unimplemented!("not efficient")
}
}
impl OligarchyCollection for LinkedListBuddy {
#[inline]
fn take_any(&mut self, align_order: usize, count: usize) -> Option<usize> {
if count > 1 || align_order > 0 {
None
} else {
self.free_list
.take_any()
.map(|ptr| self.order.ptr_to_idx(ptr))
}
}
#[inline]
fn put(&mut self, idx: usize) {
self.free_list
.insert_unordered(unsafe { self.order.idx_to_ptr(idx) });
}
}
impl BuddyCollection for LinkedListBuddy {
#[inline]
fn take_any(&mut self, align_order: usize) -> Option<usize> {
if align_order != 0 {
None
} else {
self.free_list
.take_any()
.map(|ptr| self.order.ptr_to_idx(ptr))
}
}
fn put(&mut self, idx: usize) -> Option<usize> {
let node = unsafe { self.order.idx_to_ptr(idx) };
let buddy = unsafe { self.order.idx_to_ptr(idx ^ 1) };
if self.free_list.insert(node, buddy) {
None
} else {
Some(idx >> 1)
}
}
}
impl fmt::Debug for LinkedListBuddy {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "[")?;
let mut cursor = &self.free_list;
while let Some(next) = cursor.next {
write!(f, "{:#x}, ", self.order.ptr_to_idx(next))?;
cursor = unsafe { next.as_ref() };
}
write!(f, "]")
}
}
#[repr(transparent)]
struct Node {
next: Option<NonNull<Node>>,
}
impl Node {
#[inline]
fn insert(&mut self, mut node: NonNull<Node>, buddy: NonNull<Node>) -> bool {
let mut cursor = self;
loop {
if let Some(mut next) = cursor.next {
use core::cmp::Ordering::*;
match next.cmp(&buddy) {
Less => cursor = unsafe { next.as_mut() },
Equal => {
cursor.next = unsafe { next.as_ref().next };
unsafe { node.as_mut() }.next = None;
break false;
}
Greater => {
cursor.next = Some(node);
unsafe { node.as_mut() }.next = Some(next);
break true;
}
}
} else {
cursor.next = Some(node);
unsafe { node.as_mut() }.next = None;
break true;
}
}
}
#[inline]
fn insert_unordered(&mut self, mut node: NonNull<Node>) {
unsafe { node.as_mut() }.next = core::mem::replace(&mut self.next, Some(node));
}
#[inline]
fn take_any(&mut self) -> Option<NonNull<Node>> {
let root = self.next;
self.next = root.and_then(|node| unsafe { node.as_ref().next });
root
}
}