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veccell
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✨ More methods (in particular partialeq and clone)

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pull/1/head
Shad Amethyst 2 years ago
parent 141be13feb
commit 6297af17eb
Signed by: amethyst
GPG Key ID: D970C8DD1D6DEE36
1 changed files with 347 additions and 16 deletions
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363
src/lib.rs
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@ -1,6 +1,21 @@
#![feature(type_alias_impl_trait)]
use std::cell::{Cell, UnsafeCell};
use std::fmt::{self, Debug};
use std::ops::{Deref, DerefMut};
///
/// # Safety
///
/// The following invariants are enforced by the code:
///
/// - (I) mutable guards (`RefMut`) may only be created if `vec.mut_borrow.is_none()` and `vec.borrows == 0`
/// - (II) when a mutable guard is created, `vec.mut_borrow` is set to `Some(index)`
/// - (III) when a mutable guard is dropped, `vec.mut_borrow` may be set back to `None`
/// - (IV) a mutable reference may only be created if:
/// - (IV-a) exclusive access to the `VecCell` is guaranteed (`&mut VecCell`)
/// - (IV-b) it is created from a mutable guard, and the mutable guard's lifetime does not exceed that of the mutable guard
#[derive(Debug)]
pub struct VecCell<T> {
mut_borrow: Cell<Option<usize>>,
borrows: Cell<usize>,
@ -41,6 +56,36 @@ impl<T> VecCell<T> {
self.inner.len()
}
#[inline]
pub fn capacity(&self) -> usize {
self.inner.capacity()
}
#[inline]
pub fn reserve(&mut self, additional: usize) {
self.inner.reserve(additional);
}
#[inline]
pub fn remove(&mut self, index: usize) -> T {
self.inner.remove(index).into_inner()
}
#[inline]
pub fn swap_remove(&mut self, index: usize) -> T {
self.inner.swap_remove(index).into_inner()
}
#[inline]
pub fn inner(&self) -> &Vec<UnsafeCell<T>> {
&self.inner
}
#[inline]
pub fn inner_mut(&mut self) -> &mut Vec<UnsafeCell<T>> {
&mut self.inner
}
pub fn borrows(&self) -> usize {
self.borrows.get()
}
@ -77,15 +122,113 @@ impl<T> VecCell<T> {
pub unsafe fn get_mut_unchecked(&self, index: usize) -> &mut T {
&mut *self.inner.get_unchecked(index).get()
}
pub fn iter<'b>(&'b self) -> impl Iterator<Item = VecRef<'b, T>> {
self.into_iter()
}
pub fn iter_mut<'b>(&'b mut self) -> impl Iterator<Item = &'b mut T> {
self.inner.iter_mut().map(UnsafeCell::get_mut)
}
}
impl<'a, T: 'a> IntoIterator for &'a VecCell<T> {
type Item = VecRef<'a, T>;
type IntoIter = impl Iterator<Item = Self::Item>;
/// # Panics
///
/// Panics if a value is currently mutably borrowed
fn into_iter(self) -> Self::IntoIter {
(0..self.len()).map(|index| {
self.get(index).expect("An element of VecCell is currently mutably borrowed")
})
}
}
impl<T> IntoIterator for VecCell<T> {
type Item = T;
type IntoIter = impl Iterator<Item = Self::Item>;
/// # Panics
///
/// Panics if a value is currently mutably borrowed
fn into_iter(self) -> Self::IntoIter {
self.inner.into_iter().map(|x| x.into_inner())
}
}
impl<T: Clone> Clone for VecCell<T> {
/// # Panics
///
/// Panics if a value is currently mutably borrowed
fn clone(&self) -> Self {
VecCell {
inner: self.into_iter().map(|x| UnsafeCell::new((*x).clone())).collect::<Vec<_>>(),
mut_borrow: Cell::new(None),
borrows: Cell::new(0),
}
}
}
impl<T: PartialEq> PartialEq for VecCell<T> {
/// # Panics
///
/// Panics if a value in `self` or `other` is currently mutably borrowed when it is encountered in the comparison.
fn eq(&self, other: &Self) -> bool {
if self.len() != other.len() {
return false
}
for (s, o) in self.iter().zip(other.iter()) {
if *s != *o {
return false
}
}
true
}
}
impl<T: PartialEq> PartialEq<Vec<T>> for VecCell<T> {
/// # Panics
///
/// Panics if a value in `self` is currently mutably borrowed when it is encountered in the comparison.
fn eq(&self, other: &Vec<T>) -> bool {
if self.len() != other.len() {
return false
}
for (s, o) in self.iter().zip(other.iter()) {
if *s != *o {
return false
}
}
true
}
}
impl<T> From<Vec<T>> for VecCell<T> {
fn from(vec: Vec<T>) -> Self {
VecCell {
inner: vec.into_iter().map(|x| UnsafeCell::new(x)).collect::<Vec<_>>(),
mut_borrow: Cell::new(None),
borrows: Cell::new(0),
}
}
}
pub struct VecRef<'a, T> {
pub struct VecRef<'a, T: ?Sized> {
borrows: &'a Cell<usize>,
value: &'a T,
}
impl<'a, T> VecRef<'a, T> {
fn new(vec: &'a VecCell<T>, index: usize) -> Option<Self> {
impl<'a, T: ?Sized> VecRef<'a, T> {
fn new(vec: &'a VecCell<T>, index: usize) -> Option<Self>
where
T: Sized
{
if vec.mut_borrow.get() == Some(index) {
return None
}
@ -104,9 +247,23 @@ impl<'a, T> VecRef<'a, T> {
}
})
}
pub fn get(&self) -> &T {
&*self.value
}
pub fn map<'b, U: ?Sized, F>(original: VecRef<'b, T>, f: F) -> VecRef<'b, U>
where
F: FnOnce(&T) -> &U
{
VecRef {
value: f(original.value),
borrows: original.borrows
}
}
}
impl<'a, T> std::ops::Deref for VecRef<'a, T> {
impl<'a, T: ?Sized> Deref for VecRef<'a, T> {
type Target = T;
fn deref(&self) -> &Self::Target {
@ -114,7 +271,7 @@ impl<'a, T> std::ops::Deref for VecRef<'a, T> {
}
}
impl<'a, T> Drop for VecRef<'a, T> {
impl<'a, T: ?Sized> Drop for VecRef<'a, T> {
#[inline]
fn drop(&mut self) {
debug_assert!(self.borrows.get() > 0, "Borrow count was null yet there was still a borrow!");
@ -122,7 +279,7 @@ impl<'a, T> Drop for VecRef<'a, T> {
}
}
impl<'a, T: Debug> Debug for VecRef<'a, T> {
impl<'a, T: Debug + Sized> Debug for VecRef<'a, T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("VecRef")
.field(self.value)
@ -130,13 +287,37 @@ impl<'a, T: Debug> Debug for VecRef<'a, T> {
}
}
pub struct VecRefMut<'a, T> {
impl<'a, T: PartialEq + ?Sized> PartialEq for VecRef<'a, T> {
fn eq(&self, other: &Self) -> bool {
self.get() == other.get()
}
}
impl<'a, T: PartialEq + ?Sized> PartialEq<T> for VecRef<'a, T> {
fn eq(&self, other: &T) -> bool {
self.get() == other
}
}
pub struct VecRefMut<'a, T: ?Sized> {
mut_borrow: &'a Cell<Option<usize>>,
value: &'a mut T,
}
impl<'a, T> VecRefMut<'a, T> {
fn new(vec: &'a VecCell<T>, index: usize) -> Option<Self> {
impl<'a, T: ?Sized> VecRefMut<'a, T> {
/// # Safety
///
/// If this function returns Some(ref), then there are no mutable borrows of ∀x, vec.inner[x]:
/// by contradiction, let `B: 'b` be a mutable borrow of lifetime `'b`. By conjunction on (IV):
/// - either `B` had exclusive access, in which case calling `VecCell::borrow_mut` is UB
/// - either `B` was obtained from a guard `VecRefMut<'c>`, in which case `'c: 'b` and `vec.mut_borrow.is_some()`, which contradicts our assertion
///
/// - The invariant (I) is upheld by the first assertion.
/// - The invariant (II) is upheld by this function, as it sets `vec.mut_borrow` to `Some(index)`.
fn new(vec: &'a VecCell<T>, index: usize) -> Option<Self>
where
T: Sized
{
if vec.borrows.get() > 0 || vec.mut_borrow.get().is_some() {
return None
}
@ -150,29 +331,48 @@ impl<'a, T> VecRefMut<'a, T> {
Some(Self {
mut_borrow: &vec.mut_borrow,
value: unsafe {
// SAFETY: there are no mutable borrows of ∀x, vec.inner[x],
// and we set vec.mut_borrow to Some(index), guaranteeing no further aliasing
vec.get_mut_unchecked(index)
}
})
}
pub fn get(&self) -> &T {
&*self.value
}
pub fn get_mut(&mut self) -> &mut T {
&mut *self.value
}
// pub fn map<'b, U: ?Sized, F>(original: VecRefMut<'b, T>, f: F) -> VecRefMut<'b, U>
// where
// F: FnOnce(&mut T) -> &mut U
// {
// let VecRefMut { value, mut_borrow } = original;
// VecRefMut {
// value: f(value),
// mut_borrow
// }
// }
}
impl<'a, T> std::ops::Deref for VecRefMut<'a, T> {
impl<'a, T: ?Sized> Deref for VecRefMut<'a, T> {
type Target = T;
// SAFETY: Upholds invariant (IV)
fn deref(&self) -> &Self::Target {
self.value
}
}
impl<'a, T> std::ops::DerefMut for VecRefMut<'a, T> {
impl<'a, T: ?Sized> DerefMut for VecRefMut<'a, T> {
// SAFETY: Upholds invariant (IV)
fn deref_mut(&mut self) -> &mut Self::Target {
self.value
}
}
impl<'a, T> Drop for VecRefMut<'a, T> {
impl<'a, T: ?Sized> Drop for VecRefMut<'a, T> {
#[inline]
fn drop(&mut self) {
debug_assert!(self.mut_borrow.get().is_some());
@ -180,10 +380,141 @@ impl<'a, T> Drop for VecRefMut<'a, T> {
}
}
impl<'a, T: Debug> Debug for VecRefMut<'a, T> {
impl<'a, T: Debug + Sized> Debug for VecRefMut<'a, T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("VecRefMut")
.field(self.value)
.finish()
}
}
impl<'a, T: PartialEq + ?Sized> PartialEq for VecRefMut<'a, T> {
fn eq(&self, other: &Self) -> bool {
self.get() == other.get()
}
}
impl<'a, T: PartialEq + ?Sized> PartialEq<T> for VecRefMut<'a, T> {
fn eq(&self, other: &T) -> bool {
self.get() == other
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_create_vec() {
let vec: VecCell<usize> = VecCell::new();
assert_eq!(vec.len(), 0);
let vec: VecCell<i8> = VecCell::new();
assert_eq!(vec.len(), 0);
let vec: VecCell<()> = VecCell::new();
assert_eq!(vec.len(), 0);
let vec: VecCell<usize> = VecCell::with_capacity(16);
assert_eq!(vec.len(), 0);
assert_eq!(vec.capacity(), 16);
let vec: VecCell<i8> = VecCell::with_capacity(16);
assert_eq!(vec.len(), 0);
assert_eq!(vec.capacity(), 16);
let vec: VecCell<()> = VecCell::with_capacity(16);
assert_eq!(vec.len(), 0);
assert_eq!(vec.capacity(), usize::MAX);
let vec: VecCell<usize> = VecCell::with_capacity(0);
assert_eq!(vec.len(), 0);
assert_eq!(vec.capacity(), 0);
let vec: VecCell<i8> = VecCell::with_capacity(0);
assert_eq!(vec.len(), 0);
assert_eq!(vec.capacity(), 0);
let vec: VecCell<()> = VecCell::with_capacity(0);
assert_eq!(vec.len(), 0);
assert_eq!(vec.capacity(), usize::MAX);
}
#[test]
fn test_push() {
let mut vec: VecCell<usize> = VecCell::with_capacity(1);
vec.push(0);
assert_eq!(vec.len(), 1);
vec.push(1);
assert_eq!(vec.len(), 2);
vec.push(2);
assert_eq!(vec.len(), 3);
assert_eq!(vec, vec![0, 1, 2]);
}
#[test]
fn test_pop() {
let mut vec: VecCell<usize> = VecCell::new();
vec.push(1);
assert_eq!(vec.len(), 1);
vec.push(2);
assert_eq!(vec.len(), 2);
assert_eq!(vec.pop(), Some(2));
assert_eq!(vec.len(), 1);
assert_eq!(vec.pop(), Some(1));
assert_eq!(vec.len(), 0);
}
#[test]
fn test_borrow() {
let mut vec: VecCell<usize> = VecCell::new();
vec.push(1);
vec.push(2);
let mut x = vec.borrow_mut(1).unwrap();
assert_eq!(vec.get(0).unwrap(), 1);
assert_eq!(vec.get(1), None);
*x = 3;
std::mem::drop(x);
assert_eq!(vec.get(1).unwrap(), 3);
}
#[test]
fn test_double_borrow() {
let mut vec: VecCell<usize> = VecCell::new();
vec.push(1);
vec.push(2);
let mut x = vec.borrow_mut(1).unwrap();
let y = vec.borrow_mut(0);
assert!(y.is_none());
assert_eq!(vec.mut_borrow(), Some(1));
assert!(vec.borrow_mut(1).is_none());
assert_eq!(vec.mut_borrow(), Some(1));
assert_eq!(vec.get(0).unwrap(), 1);
assert_eq!(vec.get(1), None);
*x = 3;
std::mem::drop(x);
std::mem::drop(y);
assert_eq!(vec.mut_borrow(), None);
assert_eq!(vec.get(1).unwrap(), 3);
}
#[test]
fn test_out_of_bounds() {
let mut vec: VecCell<usize> = VecCell::new();
assert!(vec.get(0).is_none());
vec.push(1);
assert!(vec.get(0).is_some());
assert!(vec.get(1).is_none());
}
}

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