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Copy pathboxvec.rs
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708 lines (616 loc) · 18.4 KB
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// spell-checker:disable
//! An unresizable vector backed by a `Box<[T]>`
#![allow(clippy::needless_lifetimes)]
use alloc::{fmt, slice};
use core::{
borrow::{Borrow, BorrowMut},
cmp,
mem::{self, MaybeUninit},
ops::{Bound, Deref, DerefMut, RangeBounds},
ptr,
};
pub struct BoxVec<T> {
xs: Box<[MaybeUninit<T>]>,
len: usize,
}
impl<T> Drop for BoxVec<T> {
fn drop(&mut self) {
self.clear();
// MaybeUninit inhibits array's drop
}
}
macro_rules! panic_oob {
($method_name:expr, $index:expr, $len:expr) => {
panic!(
concat!(
"BoxVec::",
$method_name,
": index {} is out of bounds in vector of length {}"
),
$index, $len
)
};
}
impl<T> BoxVec<T> {
pub fn new(n: usize) -> Self {
Self {
xs: Box::new_uninit_slice(n),
len: 0,
}
}
#[inline]
pub const fn len(&self) -> usize {
self.len
}
#[inline]
pub const fn is_empty(&self) -> bool {
self.len() == 0
}
#[inline]
pub const fn capacity(&self) -> usize {
self.xs.len()
}
pub const fn is_full(&self) -> bool {
self.len() == self.capacity()
}
pub const fn remaining_capacity(&self) -> usize {
self.capacity() - self.len()
}
pub fn push(&mut self, element: T) {
self.try_push(element).unwrap()
}
pub fn try_push(&mut self, element: T) -> Result<(), CapacityError<T>> {
if self.len() < self.capacity() {
unsafe {
self.push_unchecked(element);
}
Ok(())
} else {
Err(CapacityError::new(element))
}
}
/// # Safety
/// Must ensure that self.len() < self.capacity()
pub unsafe fn push_unchecked(&mut self, element: T) {
let len = self.len();
debug_assert!(len < self.capacity());
// SAFETY: len < capacity
unsafe {
ptr::write(self.get_unchecked_ptr(len), element);
self.set_len(len + 1);
}
}
/// Get pointer to where element at `index` would be
unsafe fn get_unchecked_ptr(&mut self, index: usize) -> *mut T {
unsafe { self.xs.as_mut_ptr().add(index).cast() }
}
pub fn insert(&mut self, index: usize, element: T) {
self.try_insert(index, element).unwrap()
}
pub fn try_insert(&mut self, index: usize, element: T) -> Result<(), CapacityError<T>> {
if index > self.len() {
panic_oob!("try_insert", index, self.len())
}
if self.len() == self.capacity() {
return Err(CapacityError::new(element));
}
let len = self.len();
// follows is just like Vec<T>
unsafe {
// infallible
// The spot to put the new value
{
let p: *mut _ = self.get_unchecked_ptr(index);
// Shift everything over to make space. (Duplicating the
// `index`th element into two consecutive places.)
ptr::copy(p, p.offset(1), len - index);
// Write it in, overwriting the first copy of the `index`th
// element.
ptr::write(p, element);
}
self.set_len(len + 1);
}
Ok(())
}
pub fn pop(&mut self) -> Option<T> {
if self.is_empty() {
return None;
}
unsafe {
let new_len = self.len() - 1;
self.set_len(new_len);
Some(ptr::read(self.get_unchecked_ptr(new_len)))
}
}
pub fn swap_remove(&mut self, index: usize) -> T {
self.swap_pop(index)
.unwrap_or_else(|| panic_oob!("swap_remove", index, self.len()))
}
pub fn swap_pop(&mut self, index: usize) -> Option<T> {
let len = self.len();
if index >= len {
return None;
}
self.swap(index, len - 1);
self.pop()
}
pub fn remove(&mut self, index: usize) -> T {
self.pop_at(index)
.unwrap_or_else(|| panic_oob!("remove", index, self.len()))
}
pub fn pop_at(&mut self, index: usize) -> Option<T> {
if index >= self.len() {
None
} else {
self.drain(index..=index).next()
}
}
pub fn truncate(&mut self, new_len: usize) {
unsafe {
if new_len < self.len() {
let tail: *mut [_] = &mut self[new_len..];
self.len = new_len;
ptr::drop_in_place(tail);
}
}
}
/// Remove all elements in the vector.
pub fn clear(&mut self) {
self.truncate(0)
}
/// Retains only the elements specified by the predicate.
///
/// In other words, remove all elements `e` such that `f(&mut e)` returns false.
/// This method operates in place and preserves the order of the retained
/// elements.
pub fn retain<F>(&mut self, mut f: F)
where
F: FnMut(&mut T) -> bool,
{
let len = self.len();
let mut del = 0;
{
let v = &mut **self;
for i in 0..len {
if !f(&mut v[i]) {
del += 1;
} else if del > 0 {
v.swap(i - del, i);
}
}
}
if del > 0 {
self.drain(len - del..);
}
}
/// Set the vector’s length without dropping or moving out elements
///
/// This method is `unsafe` because it changes the notion of the
/// number of “valid” elements in the vector. Use with care.
///
/// This method uses *debug assertions* to check that `length` is
/// not greater than the capacity.
///
/// # Safety
/// Must ensure that length <= self.capacity()
pub unsafe fn set_len(&mut self, length: usize) {
debug_assert!(length <= self.capacity());
self.len = length;
}
/// Copy and appends all elements in a slice to the `BoxVec`.
///
/// # Errors
///
/// This method will return an error if the capacity left (see
/// [`remaining_capacity`]) is smaller then the length of the provided
/// slice.
///
/// [`remaining_capacity`]: #method.remaining_capacity
pub fn try_extend_from_slice(&mut self, other: &[T]) -> Result<(), CapacityError>
where
T: Copy,
{
if self.remaining_capacity() < other.len() {
return Err(CapacityError::new(()));
}
let self_len = self.len();
let other_len = other.len();
unsafe {
let dst = self.as_mut_ptr().add(self_len);
ptr::copy_nonoverlapping(other.as_ptr(), dst, other_len);
self.set_len(self_len + other_len);
}
Ok(())
}
/// Create a draining iterator that removes the specified range in the vector
/// and yields the removed items from start to end. The element range is
/// removed even if the iterator is not consumed until the end.
///
/// Note: It is unspecified how many elements are removed from the vector,
/// if the `Drain` value is leaked.
///
/// **Panics** if the starting point is greater than the end point or if
/// the end point is greater than the length of the vector.
pub fn drain<R>(&mut self, range: R) -> Drain<'_, T>
where
R: RangeBounds<usize>,
{
// Memory safety
//
// When the Drain is first created, it shortens the length of
// the source vector to make sure no uninitialized or moved-from elements
// are accessible at all if the Drain's destructor never gets to run.
//
// Drain will ptr::read out the values to remove.
// When finished, remaining tail of the vec is copied back to cover
// the hole, and the vector length is restored to the new length.
//
let len = self.len();
let start = match range.start_bound() {
Bound::Unbounded => 0,
Bound::Included(&i) => i,
Bound::Excluded(&i) => i.saturating_add(1),
};
let end = match range.end_bound() {
Bound::Excluded(&j) => j,
Bound::Included(&j) => j.saturating_add(1),
Bound::Unbounded => len,
};
self.drain_range(start, end)
}
fn drain_range(&mut self, start: usize, end: usize) -> Drain<'_, T> {
let len = self.len();
// bounds check happens here (before length is changed!)
let range_slice: *const _ = &self[start..end];
// Calling `set_len` creates a fresh and thus unique mutable references, making all
// older aliases we created invalid. So we cannot call that function.
self.len = start;
unsafe {
Drain {
tail_start: end,
tail_len: len - end,
iter: (*range_slice).iter(),
vec: ptr::NonNull::from(self),
}
}
}
/// Return a slice containing all elements of the vector.
pub fn as_slice(&self) -> &[T] {
self
}
/// Return a mutable slice containing all elements of the vector.
pub fn as_mut_slice(&mut self) -> &mut [T] {
self
}
/// Return a raw pointer to the vector's buffer.
#[inline]
pub fn as_ptr(&self) -> *const T {
self.xs.as_ptr().cast()
}
/// Return a raw mutable pointer to the vector's buffer.
#[inline]
pub fn as_mut_ptr(&mut self) -> *mut T {
self.xs.as_mut_ptr().cast()
}
}
impl<T> Deref for BoxVec<T> {
type Target = [T];
#[inline]
fn deref(&self) -> &[T] {
unsafe { slice::from_raw_parts(self.as_ptr(), self.len()) }
}
}
impl<T> DerefMut for BoxVec<T> {
#[inline]
fn deref_mut(&mut self) -> &mut [T] {
let len = self.len();
unsafe { slice::from_raw_parts_mut(self.as_mut_ptr(), len) }
}
}
/// Iterate the `BoxVec` with references to each element.
impl<'a, T> IntoIterator for &'a BoxVec<T> {
type Item = &'a T;
type IntoIter = slice::Iter<'a, T>;
fn into_iter(self) -> Self::IntoIter {
self.iter()
}
}
/// Iterate the `BoxVec` with mutable references to each element.
impl<'a, T> IntoIterator for &'a mut BoxVec<T> {
type Item = &'a mut T;
type IntoIter = slice::IterMut<'a, T>;
fn into_iter(self) -> Self::IntoIter {
self.iter_mut()
}
}
/// Iterate the `BoxVec` with each element by value.
///
/// The vector is consumed by this operation.
impl<T> IntoIterator for BoxVec<T> {
type Item = T;
type IntoIter = IntoIter<T>;
fn into_iter(self) -> IntoIter<T> {
IntoIter { index: 0, v: self }
}
}
/// By-value iterator for `BoxVec`.
pub struct IntoIter<T> {
index: usize,
v: BoxVec<T>,
}
impl<T> Iterator for IntoIter<T> {
type Item = T;
fn next(&mut self) -> Option<T> {
if self.index == self.v.len {
None
} else {
unsafe {
let index = self.index;
self.index += 1;
Some(ptr::read(self.v.get_unchecked_ptr(index)))
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let len = self.v.len() - self.index;
(len, Some(len))
}
}
impl<T> DoubleEndedIterator for IntoIter<T> {
fn next_back(&mut self) -> Option<T> {
if self.index == self.v.len {
None
} else {
unsafe {
let new_len = self.v.len() - 1;
self.v.set_len(new_len);
Some(ptr::read(self.v.get_unchecked_ptr(new_len)))
}
}
}
}
impl<T> ExactSizeIterator for IntoIter<T> {}
impl<T> Drop for IntoIter<T> {
fn drop(&mut self) {
// panic safety: Set length to 0 before dropping elements.
let index = self.index;
let len = self.v.len();
unsafe {
self.v.set_len(0);
let elements = slice::from_raw_parts_mut(self.v.get_unchecked_ptr(index), len - index);
ptr::drop_in_place(elements);
}
}
}
impl<T> fmt::Debug for IntoIter<T>
where
T: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_list().entries(&self.v[self.index..]).finish()
}
}
/// A draining iterator for `BoxVec`.
pub struct Drain<'a, T> {
/// Index of tail to preserve
tail_start: usize,
/// Length of tail
tail_len: usize,
/// Current remaining range to remove
iter: slice::Iter<'a, T>,
vec: ptr::NonNull<BoxVec<T>>,
}
unsafe impl<T: Sync> Sync for Drain<'_, T> {}
unsafe impl<T: Sync> Send for Drain<'_, T> {}
impl<T> Iterator for Drain<'_, T> {
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
self.iter
.next()
.map(|elt| unsafe { ptr::read(elt as *const _) })
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}
impl<T> DoubleEndedIterator for Drain<'_, T> {
fn next_back(&mut self) -> Option<Self::Item> {
self.iter
.next_back()
.map(|elt| unsafe { ptr::read(elt as *const _) })
}
}
impl<T> ExactSizeIterator for Drain<'_, T> {}
impl<'a, T> Drain<'a, T> {
pub fn as_slice(&self) -> &'a [T] {
self.iter.as_slice()
}
}
impl<T> Drop for Drain<'_, T> {
fn drop(&mut self) {
// len is currently 0 so panicking while dropping will not cause a double drop.
for _ in self.by_ref() {}
if self.tail_len > 0 {
unsafe {
let source_vec = self.vec.as_mut();
// memmove back untouched tail, update to new length
let start = source_vec.len();
let tail = self.tail_start;
let src = source_vec.as_ptr().add(tail);
let dst = source_vec.as_mut_ptr().add(start);
ptr::copy(src, dst, self.tail_len);
source_vec.set_len(start + self.tail_len);
}
}
}
}
struct ScopeExitGuard<T, Data, F>
where
F: FnMut(&Data, &mut T),
{
value: T,
data: Data,
f: F,
}
impl<T, Data, F> Drop for ScopeExitGuard<T, Data, F>
where
F: FnMut(&Data, &mut T),
{
fn drop(&mut self) {
(self.f)(&self.data, &mut self.value)
}
}
/// Extend the `BoxVec` with an iterator.
///
/// Does not extract more items than there is space for. No error
/// occurs if there are more iterator elements.
impl<T> Extend<T> for BoxVec<T> {
fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
let take = self.capacity() - self.len();
unsafe {
let len = self.len();
let mut ptr = raw_ptr_add(self.as_mut_ptr(), len);
let end_ptr = raw_ptr_add(ptr, take);
// Keep the length in a separate variable, write it back on scope
// exit. To help the compiler with alias analysis and stuff.
// We update the length to handle panic in the iteration of the
// user's iterator, without dropping any elements on the floor.
let mut guard = ScopeExitGuard {
value: &mut self.len,
data: len,
f: move |&len, self_len| {
**self_len = len;
},
};
let mut iter = iter.into_iter();
loop {
if core::ptr::eq(ptr, end_ptr) {
break;
}
if let Some(elt) = iter.next() {
raw_ptr_write(ptr, elt);
ptr = raw_ptr_add(ptr, 1);
guard.data += 1;
} else {
break;
}
}
}
}
}
/// Rawptr add but uses arithmetic distance for ZST
unsafe fn raw_ptr_add<T>(ptr: *mut T, offset: usize) -> *mut T {
if mem::size_of::<T>() == 0 {
// Special case for ZST
(ptr as usize).wrapping_add(offset) as _
} else {
unsafe { ptr.add(offset) }
}
}
unsafe fn raw_ptr_write<T>(ptr: *mut T, value: T) {
if mem::size_of::<T>() == 0 {
/* nothing */
} else {
unsafe { ptr::write(ptr, value) }
}
}
impl<T> Clone for BoxVec<T>
where
T: Clone,
{
fn clone(&self) -> Self {
let mut new = Self::new(self.capacity());
new.extend(self.iter().cloned());
new
}
fn clone_from(&mut self, rhs: &Self) {
// recursive case for the common prefix
let prefix = cmp::min(self.len(), rhs.len());
self[..prefix].clone_from_slice(&rhs[..prefix]);
if prefix < self.len() {
// rhs was shorter
for _ in 0..self.len() - prefix {
self.pop();
}
} else {
let rhs_elems = rhs[self.len()..].iter().cloned();
self.extend(rhs_elems);
}
}
}
impl<T> PartialEq for BoxVec<T>
where
T: PartialEq,
{
fn eq(&self, other: &Self) -> bool {
**self == **other
}
}
impl<T> PartialEq<[T]> for BoxVec<T>
where
T: PartialEq,
{
fn eq(&self, other: &[T]) -> bool {
**self == *other
}
}
impl<T> Eq for BoxVec<T> where T: Eq {}
impl<T> Borrow<[T]> for BoxVec<T> {
fn borrow(&self) -> &[T] {
self
}
}
impl<T> BorrowMut<[T]> for BoxVec<T> {
fn borrow_mut(&mut self) -> &mut [T] {
self
}
}
impl<T> AsRef<[T]> for BoxVec<T> {
fn as_ref(&self) -> &[T] {
self
}
}
impl<T> AsMut<[T]> for BoxVec<T> {
fn as_mut(&mut self) -> &mut [T] {
self
}
}
impl<T> fmt::Debug for BoxVec<T>
where
T: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
(**self).fmt(f)
}
}
/// Error value indicating insufficient capacity
#[derive(Clone, Copy, Eq, Ord, PartialEq, PartialOrd)]
pub struct CapacityError<T = ()> {
element: T,
}
impl<T> CapacityError<T> {
/// Create a new `CapacityError` from `element`.
pub const fn new(element: T) -> Self {
Self { element }
}
/// Extract the overflowing element
pub fn element(self) -> T {
self.element
}
/// Convert into a `CapacityError` that does not carry an element.
pub fn simplify(self) -> CapacityError {
CapacityError { element: () }
}
}
const CAPERROR: &str = "insufficient capacity";
impl<T> core::error::Error for CapacityError<T> {}
impl<T> fmt::Display for CapacityError<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{CAPERROR}")
}
}
impl<T> fmt::Debug for CapacityError<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "capacity error: {CAPERROR}")
}
}
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