A freelist in Rust
0
$begingroup$
pub struct FreeList<T: Copy, I: Copy> {
items: Vec<Node<T, I>>,
free: I,
}
union Node<T: Copy, I: Copy> {
used: T,
free: I,
}
impl<T: Copy, I: ID> FreeList<T, I> {
pub fn new() -> Self {
Self { items: Vec::new(), free: I::none() }
}
pub unsafe fn insert(&mut self, x: T) -> I {
if self.free.is_none() {
let i = I::from_usize(self.items.len());
self.items.push(Node { used: x });
i
} else {
let i = self.free;
let slot = self.items.get_unchecked_mut(i.into_usize());
self.free = slot.free;
*slot = Node { used: x };
i
}
}
pub unsafe fn remove(&mut self, i: I) -> T {
let slot = self.items.get_unchecked_mut(i.into_usize());
let data = slot.used;
*slot = Node { free: self.free };
self.free = i;
data
}
pub unsafe fn get(&self, i: I) -> &T {
&self.items.get_unchecked(i.into_usize()).used
}
pub unsafe fn get_mut(&mut self, i: I) -> &mut T {
&mut self.items.get_unchecked_mut(i.into_usize()).used
}
}
fn main() {}
pub trait ID: Copy {
fn from_usize(u: usize) -> Self;
fn into_usize(self) -> usize;
fn none() -> Self;
fn is_none(self) -> bool;
}
This is just a freelist. There's a lot of unsafety, though, so I wanted to make sure that I got it right. In particular:
- is insert always safe?
- is remove safe as long as there isn't a use-after-remove?
- is the drop code correct?
rust
asked 1 hour ago
Shigeo KageyamaShigeo Kageyama
1
New contributor
Shigeo Kageyama is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
0
$begingroup$
pub struct FreeList<T: Copy, I: Copy> {
items: Vec<Node<T, I>>,
free: I,
}
union Node<T: Copy, I: Copy> {
used: T,
free: I,
}
impl<T: Copy, I: ID> FreeList<T, I> {
pub fn new() -> Self {
Self { items: Vec::new(), free: I::none() }
}
pub unsafe fn insert(&mut self, x: T) -> I {
if self.free.is_none() {
let i = I::from_usize(self.items.len());
self.items.push(Node { used: x });
i
} else {
let i = self.free;
let slot = self.items.get_unchecked_mut(i.into_usize());
self.free = slot.free;
*slot = Node { used: x };
i
}
}
pub unsafe fn remove(&mut self, i: I) -> T {
let slot = self.items.get_unchecked_mut(i.into_usize());
let data = slot.used;
*slot = Node { free: self.free };
self.free = i;
data
}
pub unsafe fn get(&self, i: I) -> &T {
&self.items.get_unchecked(i.into_usize()).used
}
pub unsafe fn get_mut(&mut self, i: I) -> &mut T {
&mut self.items.get_unchecked_mut(i.into_usize()).used
}
}
fn main() {}
pub trait ID: Copy {
fn from_usize(u: usize) -> Self;
fn into_usize(self) -> usize;
fn none() -> Self;
fn is_none(self) -> bool;
}
This is just a freelist. There's a lot of unsafety, though, so I wanted to make sure that I got it right. In particular:
- is insert always safe?
- is remove safe as long as there isn't a use-after-remove?
- is the drop code correct?
rust
asked 1 hour ago
Shigeo KageyamaShigeo Kageyama
1
New contributor
Shigeo Kageyama is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
0
0
0
$begingroup$
pub struct FreeList<T: Copy, I: Copy> {
items: Vec<Node<T, I>>,
free: I,
}
union Node<T: Copy, I: Copy> {
used: T,
free: I,
}
impl<T: Copy, I: ID> FreeList<T, I> {
pub fn new() -> Self {
Self { items: Vec::new(), free: I::none() }
}
pub unsafe fn insert(&mut self, x: T) -> I {
if self.free.is_none() {
let i = I::from_usize(self.items.len());
self.items.push(Node { used: x });
i
} else {
let i = self.free;
let slot = self.items.get_unchecked_mut(i.into_usize());
self.free = slot.free;
*slot = Node { used: x };
i
}
}
pub unsafe fn remove(&mut self, i: I) -> T {
let slot = self.items.get_unchecked_mut(i.into_usize());
let data = slot.used;
*slot = Node { free: self.free };
self.free = i;
data
}
pub unsafe fn get(&self, i: I) -> &T {
&self.items.get_unchecked(i.into_usize()).used
}
pub unsafe fn get_mut(&mut self, i: I) -> &mut T {
&mut self.items.get_unchecked_mut(i.into_usize()).used
}
}
fn main() {}
pub trait ID: Copy {
fn from_usize(u: usize) -> Self;
fn into_usize(self) -> usize;
fn none() -> Self;
fn is_none(self) -> bool;
}
This is just a freelist. There's a lot of unsafety, though, so I wanted to make sure that I got it right. In particular:
- is insert always safe?
- is remove safe as long as there isn't a use-after-remove?
- is the drop code correct?
rust
asked 1 hour ago
Shigeo KageyamaShigeo Kageyama
1
New contributor
Shigeo Kageyama is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
pub struct FreeList<T: Copy, I: Copy> {
items: Vec<Node<T, I>>,
free: I,
}
union Node<T: Copy, I: Copy> {
used: T,
free: I,
}
impl<T: Copy, I: ID> FreeList<T, I> {
pub fn new() -> Self {
Self { items: Vec::new(), free: I::none() }
}
pub unsafe fn insert(&mut self, x: T) -> I {
if self.free.is_none() {
let i = I::from_usize(self.items.len());
self.items.push(Node { used: x });
i
} else {
let i = self.free;
let slot = self.items.get_unchecked_mut(i.into_usize());
self.free = slot.free;
*slot = Node { used: x };
i
}
}
pub unsafe fn remove(&mut self, i: I) -> T {
let slot = self.items.get_unchecked_mut(i.into_usize());
let data = slot.used;
*slot = Node { free: self.free };
self.free = i;
data
}
pub unsafe fn get(&self, i: I) -> &T {
&self.items.get_unchecked(i.into_usize()).used
}
pub unsafe fn get_mut(&mut self, i: I) -> &mut T {
&mut self.items.get_unchecked_mut(i.into_usize()).used
}
}
fn main() {}
pub trait ID: Copy {
fn from_usize(u: usize) -> Self;
fn into_usize(self) -> usize;
fn none() -> Self;
fn is_none(self) -> bool;
}
This is just a freelist. There's a lot of unsafety, though, so I wanted to make sure that I got it right. In particular:
- is insert always safe?
- is remove safe as long as there isn't a use-after-remove?
- is the drop code correct?
rust
rust
asked 1 hour ago
Shigeo KageyamaShigeo Kageyama
1
New contributor
Shigeo Kageyama is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 1 hour ago
Shigeo KageyamaShigeo Kageyama
1
New contributor
Shigeo Kageyama is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 1 hour ago
Shigeo KageyamaShigeo Kageyama
1
New contributor
Shigeo Kageyama is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 1 hour ago
Shigeo KageyamaShigeo Kageyama
1
asked 1 hour ago
Shigeo KageyamaShigeo Kageyama
1
1
New contributor
Shigeo Kageyama is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Shigeo Kageyama is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Shigeo Kageyama is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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