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use crate::{drain::slice_range, *};
pub trait Array<T>: AsRef<[T]> + AsMut<[T]> + Default {
/// Returns the number of elements the array can hold.
///
/// # Examples
///
/// ```
/// use stack_array::*;
///
/// let arr: ArrayBuf<u8, 4> = ArrayBuf::new();
/// assert_eq!(arr.capacity(), 4);
/// ```
fn capacity(&self) -> usize;
/// Shortens the array, keeping the first `len` elements and dropping
/// the rest.
///
/// If `len` is greater than the array's current length, this has no
/// effect.
#[inline]
fn truncate(&mut self, len: usize) {
// This is safe because:
//
// * the slice passed to `drop_in_place` is valid; the `len > self.len`
// case avoids creating an invalid slice, and
// * the `len` of the array is shrunk before calling `drop_in_place`,
// such that no value will be dropped twice in case `drop_in_place`
// were to panic once (if it panics twice, the program aborts).
unsafe {
// Note: It's intentional that this is `>` and not `>=`.
// Changing it to `>=` has negative performance
// implications in some cases. See #78884 for more.
if len > self.len() {
return;
}
let remaining_len = self.len() - len;
let s = ptr::slice_from_raw_parts_mut(self.as_mut_ptr().add(len), remaining_len);
self.set_len(len);
ptr::drop_in_place(s);
}
}
/// Returns a raw pointer to the array's buffer.
///
/// The caller must ensure that the array outlives the pointer this
/// function returns, or else it will end up pointing to garbage.
/// Modifying the array may cause its buffer to be reallocated,
/// which would also make any pointers to it invalid.
///
/// The caller must also ensure that the memory the pointer (non-transitively) points to
/// is never written to (except inside an `UnsafeCell`) using this pointer or any pointer
/// derived from it. If you need to mutate the contents of the slice, use [`as_mut_ptr`].
///
/// [`as_mut_ptr`]: Array::as_mut_ptr
fn as_ptr(&self) -> *const T;
/// Returns an unsafe mutable pointer to the array's buffer.
///
/// The caller must ensure that the array outlives the pointer this
/// function returns, or else it will end up pointing to garbage.
/// Modifying the array may cause its buffer to be reallocated,
/// which would also make any pointers to it invalid.
fn as_mut_ptr(&mut self) -> *mut T;
/// Forces the length of the array to `new_len`.
///
/// This is a low-level operation that maintains none of the normal
/// invariants of the type. Normally changing the length of a array
/// is done using one of the safe operations instead, such as
/// [`truncate`] or [`clear`].
///
/// [`truncate`]: Array::truncate
/// [`clear`]: Array::clear
///
/// # Safety
///
/// - `new_len` must be less than or equal to [`capacity()`].
/// - The elements at `old_len..new_len` must be initialized.
///
/// [`capacity()`]: Vec::capacity
unsafe fn set_len(&mut self, len: usize);
/// Extracts a slice containing the entire array.
///
/// Equivalent to `&s[..]`.
#[inline]
fn as_slice(&self) -> &[T] {
// SAFETY: slice will contain only initialized objects.
unsafe { slice::from_raw_parts(self.as_ptr(), self.len()) }
}
/// Extracts a mutable slice of the entire array.
///
/// Equivalent to `&mut s[..]`.
#[inline]
fn as_mut_slice(&mut self) -> &mut [T] {
// SAFETY: slice will contain only initialized objects.
unsafe { slice::from_raw_parts_mut(self.as_mut_ptr(), self.len()) }
}
/// Removes an element from the array and returns it.
///
/// The removed element is replaced by the last element of the array.
///
/// This does not preserve ordering, but is *O*(1).
/// If you need to preserve the element order, use [`remove`] instead.
///
/// [`remove`]: Array::remove
///
/// # Panics
///
/// Panics if `index` is out of bounds.
///
/// # Examples
///
/// ```
/// use stack_array::*;
///
/// let mut arr = ArrayBuf::from(["foo", "bar", "baz", "qux"]);
///
/// assert_eq!(arr.swap_remove(1), "bar");
/// assert_eq!(arr[..], ["foo", "qux", "baz"]);
///
/// assert_eq!(arr.swap_remove(0), "foo");
/// assert_eq!(arr[..], ["baz", "qux"]);
/// ```
#[inline]
fn swap_remove(&mut self, index: usize) -> T {
#[cold]
#[inline(never)]
fn assert_failed(index: usize, len: usize) -> ! {
panic!(
"swap_remove index (is {}) should be < len (is {})",
index, len
);
}
let len = self.len();
if index >= len {
assert_failed(index, len);
}
unsafe {
// We replace self[index] with the last element. Note that if the
// bounds check above succeeds there must be a last element (which
// can be self[index] itself).
let value = ptr::read(self.as_ptr().add(index));
let base_ptr = self.as_mut_ptr();
ptr::copy(base_ptr.add(len - 1), base_ptr.add(index), 1);
self.set_len(len - 1);
value
}
}
/// Inserts an element at position index within the array, shifting all elements after it to the right.
/// # Examples
///
/// ```
/// use stack_array::*;
///
/// let mut list: ArrayBuf<u8, 3> = ArrayBuf::from([3].as_ref());
/// list.insert(0, 1);
/// assert_eq!(&list[..], [1, 3]);
/// list.insert(1, 2);
/// assert_eq!(&list, &[1, 2, 3]);
/// ```
///
/// # Panics
/// Panics if the index is out of bounds.
#[inline]
fn insert(&mut self, index: usize, element: T) {
#[cold]
#[inline(never)]
fn assert_failed(index: usize, len: usize) -> ! {
panic!(
"insertion index (is {}) should be <= len (is {})",
index, len
);
}
let len = self.len();
if index > len {
assert_failed(index, len);
}
// space for the new element
let total_len = len + 1;
self.ensure_capacity(total_len);
unsafe {
// infallible
// The spot to put the new value
{
let p = self.as_mut_ptr().add(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(total_len);
}
}
/// Removes an element from position index within the array, shifting all elements after it to the left.
///
/// Note: Because this shifts over the remaining elements, it has a
/// worst-case performance of *O*(*n*). If you don't need the order of elements
/// to be preserved, use [`swap_remove`] instead.
///
/// [`swap_remove`]: Array::swap_remove
///
/// # Examples
///
/// ```
/// use stack_array::*;
///
/// let mut list = ArrayBuf::from([1, 2, 3]);
/// assert_eq!(list.remove(0), 1);
/// assert_eq!(list.remove(0), 2);
/// assert_eq!(list.remove(0), 3);
/// ```
///
/// # Panics
/// Panics if the index is out of bounds.
#[inline]
fn remove(&mut self, index: usize) -> T {
#[cold]
#[inline(never)]
#[track_caller]
fn assert_failed(index: usize, len: usize) -> ! {
panic!("removal index (is {}) should be < len (is {})", index, len);
}
let len = self.len();
if index >= len {
assert_failed(index, len);
}
unsafe {
// infallible
let ret;
{
// the place we are taking from.
let ptr = self.as_mut_ptr().add(index);
// copy it out, unsafely having a copy of the value on
// the stack and in the array at the same time.
ret = ptr::read(ptr);
// Shift everything down to fill in that spot.
ptr::copy(ptr.offset(1), ptr, len - index - 1);
}
self.set_len(len - 1);
ret
}
}
/// Retains only the elements specified by the predicate.
///
/// In other words, remove all elements `e` such that `f(&e)` returns `false`.
/// This method operates in place, visiting each element exactly once in the
/// original order, and preserves the order of the retained elements.
///
/// # Examples
///
/// ```
/// use stack_array::*;
///
/// let mut arr = ArrayBuf::from([1, 2, 3, 4]);
///
/// arr.retain(|x| *x % 2 == 0);
/// assert_eq!(arr[..], [2, 4]);
/// ```
///
/// Because the elements are visited exactly once in the original order,
/// external state may be used to decide which elements to keep.
///
/// ```
/// use stack_array::*;
///
/// let mut arr = ArrayBuf::from([1, 2, 3, 4, 5]);
/// let keep = [false, true, true, false, true];
/// let mut iter = keep.iter();
/// arr.retain(|_| *iter.next().unwrap());
/// assert_eq!(arr[..], [2, 3, 5]);
/// ```
#[inline]
fn retain<F>(&mut self, mut f: F)
where
F: FnMut(&T) -> bool,
{
retain_mut(self, |elem| f(elem))
}
fn drain<R>(&mut self, range: R) -> Drain<'_, T, Self>
where
R: RangeBounds<usize>,
{
let len = self.len();
let Range { start, end } = slice_range(range, ..len);
unsafe {
// set self.vec length's to start, to be safe in case Drain is leaked
self.set_len(start);
// Use the borrow in the IterMut to indicate borrowing behavior of the
// whole Drain iterator (like &mut T).
let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().add(start), end - start);
Drain {
tail_start: end,
tail_len: len - end,
iter: range_slice.iter(),
vec: ptr::NonNull::from(self),
}
}
}
#[inline]
fn dedup(&mut self)
where
T: PartialEq,
{
self.dedup_by(|a, b| a == b)
}
/// Removes all but the first of consecutive elements in the array that resolve to the same
/// key.
///
/// If the array is sorted, this removes all duplicates.
///
/// # Examples
///
/// ```
/// use stack_array::*;
///
/// let mut arr = ArrayBuf::from([10, 20, 21, 30, 20]);
///
/// arr.dedup_by_key(|i| *i / 10);
///
/// assert_eq!(arr[..], [10, 20, 30, 20]);
#[inline]
fn dedup_by_key<F, K>(&mut self, mut key: F)
where
F: FnMut(&mut T) -> K,
K: PartialEq,
{
self.dedup_by(|a, b| key(a) == key(b))
}
fn dedup_by<F>(&mut self, mut same_bucket: F)
where
F: FnMut(&mut T, &mut T) -> bool,
{
let len = self.len();
if len <= 1 {
return;
}
/* INVARIANT: vec.len() > read >= write > write-1 >= 0 */
struct FillGapOnDrop<'a, T, A: Array<T>> {
/* Offset of the element we want to check if it is duplicate */
read: usize,
/* Offset of the place where we want to place the non-duplicate
* when we find it. */
write: usize,
/* The Vec that would need correction if `same_bucket` panicked */
vec: &'a mut A,
_marker: core::marker::PhantomData<T>,
}
impl<'a, T, A: Array<T>> Drop for FillGapOnDrop<'a, T, A> {
fn drop(&mut self) {
/* This code gets executed when `same_bucket` panics */
/* SAFETY: invariant guarantees that `read - write`
* and `len - read` never overflow and that the copy is always
* in-bounds. */
unsafe {
let ptr = self.vec.as_mut_ptr();
let len = self.vec.len();
/* How many items were left when `same_bucket` panicked.
* Basically vec[read..].len() */
let items_left = len.wrapping_sub(self.read);
/* Pointer to first item in vec[write..write+items_left] slice */
let dropped_ptr = ptr.add(self.write);
/* Pointer to first item in vec[read..] slice */
let valid_ptr = ptr.add(self.read);
/* Copy `vec[read..]` to `vec[write..write+items_left]`.
* The slices can overlap, so `copy_nonoverlapping` cannot be used */
ptr::copy(valid_ptr, dropped_ptr, items_left);
/* How many items have been already dropped
* Basically vec[read..write].len() */
let dropped = self.read.wrapping_sub(self.write);
self.vec.set_len(len - dropped);
}
}
}
let mut gap = FillGapOnDrop {
read: 1,
write: 1,
vec: self,
_marker: core::marker::PhantomData,
};
let ptr = gap.vec.as_mut_ptr();
/* Drop items while going through Vec, it should be more efficient than
* doing slice partition_dedup + truncate */
/* SAFETY: Because of the invariant, read_ptr, prev_ptr and write_ptr
* are always in-bounds and read_ptr never aliases prev_ptr */
unsafe {
while gap.read < len {
let read_ptr = ptr.add(gap.read);
let prev_ptr = ptr.add(gap.write.wrapping_sub(1));
if same_bucket(&mut *read_ptr, &mut *prev_ptr) {
// Increase `gap.read` now since the drop may panic.
gap.read += 1;
/* We have found duplicate, drop it in-place */
ptr::drop_in_place(read_ptr);
} else {
let write_ptr = ptr.add(gap.write);
/* Because `read_ptr` can be equal to `write_ptr`, we either
* have to use `copy` or conditional `copy_nonoverlapping`.
* Looks like the first option is faster. */
ptr::copy(read_ptr, write_ptr, 1);
/* We have filled that place, so go further */
gap.write += 1;
gap.read += 1;
}
}
/* Technically we could let `gap` clean up with its Drop, but
* when `same_bucket` is guaranteed to not panic, this bloats a little
* the codegen, so we just do it manually */
gap.vec.set_len(gap.write);
mem::forget(gap);
}
}
#[inline]
fn push(&mut self, value: T) {
// This will panic or abort if we would allocate > isize::MAX bytes
// or if the length increment would overflow for zero-sized types.
let len = self.len();
let total_len = len + 1;
self.ensure_capacity(total_len);
unsafe {
let end = self.as_mut_ptr().add(len);
ptr::write(end, value);
self.set_len(total_len);
}
}
#[inline]
fn append(&mut self, other: &mut Self) {
unsafe {
let count = other.len();
let len = self.len();
let total_len = len + count;
self.ensure_capacity(total_len);
ptr::copy_nonoverlapping(
other.as_ptr() as *const T,
self.as_mut_ptr().add(len),
count,
);
self.set_len(total_len);
other.set_len(0);
}
}
/// Clears the array, removing all values.
///
/// # Examples
///
/// ```
/// use stack_array::*;
///
/// let mut list = ArrayBuf::from([1, 2, 3]);
/// list.clear();
/// assert!(list.is_empty());
/// ```
#[inline]
fn clear(&mut self) {
self.truncate(0)
}
/// Returns the number of elements currently in the array.
///
/// # Examples
///
/// ```
/// use stack_array::*;
///
/// let arr: ArrayBuf<u8, 3> = ArrayBuf::from([1, 2].as_ref());
/// assert_eq!(arr.len(), 2);
/// ```
fn len(&self) -> usize;
/// Returns true if the array contains no elements.
///
/// # Examples
///
/// ```
/// use stack_array::*;
///
/// let mut arr: ArrayBuf<u8, 2> = ArrayBuf::new();
/// assert!(arr.is_empty());
///
/// arr.push(1);
/// assert!(!arr.is_empty());
/// ```
#[inline]
fn is_empty(&self) -> bool {
self.len() == 0
}
/// Removes the last element from a collection and returns it.
///
/// # Examples
///
/// ```rust
/// use stack_array::*;
///
/// let mut arr: ArrayBuf<u8, 3> = ArrayBuf::from([1, 2].as_ref());
/// assert_eq!(arr.pop(), Some(2));
/// assert_eq!(arr.pop(), Some(1));
/// assert!(arr.is_empty());
/// ```
#[inline]
fn pop(&mut self) -> Option<T> {
if self.is_empty() {
None
} else {
unsafe {
let len = self.len() - 1;
self.set_len(len);
Some(ptr::read(self.as_ptr().add(len)))
}
}
}
//============================================================
#[inline]
fn ensure_capacity(&mut self, total_len: usize) {
if total_len > self.capacity() {
panic!(
"Array is full, Max capacity: {}, But got: {total_len}",
self.capacity()
);
}
}
/// Returns the number of elements can be inserted into the array.
///
/// # Examples
///
/// ```
/// use stack_array::*;
///
/// let arr: ArrayBuf<u8, 3> = ArrayBuf::from([1, 2].as_ref());
/// assert_eq!(arr.remaining_capacity(), 1);
/// ```
#[inline]
fn remaining_capacity(&self) -> usize {
self.capacity() - self.len()
}
#[inline]
fn extend_from_slice(&mut self, other: impl AsRef<[T]>)
where
T: Copy,
{
let other = other.as_ref();
let count = other.len();
let len = self.len();
let total_len = len + count;
self.ensure_capacity(total_len);
unsafe {
ptr::copy_nonoverlapping(other.as_ptr(), self.as_mut_ptr().add(len), count);
self.set_len(total_len);
}
}
}