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use core::convert::TryInto;
use core::mem::replace;
use core::ops;
// Vec is part of the prelude when std is enabled.
#[cfg(not(feature = "std"))]
use alloc::vec::Vec;
use crate::free_pointer::FreePointer;
use crate::generation::Generation;
use crate::iter::{Drain, IntoIter, Iter, IterMut};
/// Container that can have elements inserted into it and removed from it.
///
/// Indices use the [`Index`] type, created by inserting values with [`Arena::insert`].
#[derive(Debug, Clone)]
pub struct Arena<T> {
storage: Vec<Entry<T>>,
len: u32,
first_free: Option<FreePointer>,
}
/// Index type for [`Arena`] that has a generation attached to it.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct Index {
pub(crate) slot: u32,
pub(crate) generation: Generation,
}
impl Index {
/// Represents an `Index` that is unlikely to be in use. This is useful for
/// programs that want to do two-phase initialization in safe Rust. Avoid
/// using this value to represent the absence of an `Index`: prefer
/// `Option<Index>`.
pub const DANGLING: Self = Self {
slot: u32::MAX,
generation: Generation::DANGLING,
};
/// Convert this `Index` to an equivalent `u64` representation. Mostly
/// useful for passing to code outside of Rust.
#[allow(clippy::integer_arithmetic)]
pub const fn to_bits(self) -> u64 {
// This is safe because a `u32` bit-shifted by 32 will still fit in a `u64`.
((self.generation.to_u32() as u64) << 32) | (self.slot as u64)
}
/// Create an `Index` from bits created with `Index::to_bits`.
///
/// If this function is called with bits that are not valid for an `Index`,
/// returns `None`. This can happen if the encoded generation value is 0,
/// for example.
///
/// ## Stability
/// Bits from `Index` values are guaranteed to be compatible within all
/// semver-compatible versions of Thunderdome. That is, using
/// `Index::to_bits` in 0.4.0 and `Index::from_bits` in 0.4.2 is guaranteed
/// to work.
#[allow(clippy::integer_arithmetic)]
pub const fn from_bits(bits: u64) -> Option<Self> {
// By bit-shifting right by 32, we're undoing the left-shift in `to_bits`
// thus this is okay by the same rationale.
let generation = match Generation::from_u32((bits >> 32) as u32) {
Some(v) => v,
None => return None,
};
let slot = bits as u32;
Some(Self { generation, slot })
}
/// Convert this `Index` into a generation, discarding its slot.
pub const fn generation(self) -> u32 {
self.generation.to_u32()
}
/// Convert this `Index` into a slot, discarding its generation. Slots describe a
/// location in an [`Arena`] and are reused when entries are removed.
pub const fn slot(self) -> u32 {
self.slot
}
}
#[derive(Debug, Clone)]
pub(crate) enum Entry<T> {
Occupied(OccupiedEntry<T>),
Empty(EmptyEntry),
}
impl<T> Entry<T> {
/// Consume the entry, and if it's occupied, return the value.
fn into_value(self) -> Option<T> {
match self {
Entry::Occupied(occupied) => Some(occupied.value),
Entry::Empty(_) => None,
}
}
fn get_value_mut(&mut self, generation: Generation) -> Option<&mut T> {
match self {
Entry::Occupied(occupied) if occupied.generation == generation => {
Some(&mut occupied.value)
}
_ => None,
}
}
/// If the entry is empty, a reference to it.
fn as_empty(&self) -> Option<&EmptyEntry> {
match self {
Entry::Empty(empty) => Some(empty),
Entry::Occupied(_) => None,
}
}
/// If the entry is empty, return a mutable reference to it.
fn as_empty_mut(&mut self) -> Option<&mut EmptyEntry> {
match self {
Entry::Empty(empty) => Some(empty),
Entry::Occupied(_) => None,
}
}
}
#[derive(Debug, Clone)]
pub(crate) struct OccupiedEntry<T> {
pub(crate) generation: Generation,
pub(crate) value: T,
}
#[derive(Debug, Clone, Copy)]
pub(crate) struct EmptyEntry {
pub(crate) generation: Generation,
pub(crate) next_free: Option<FreePointer>,
}
impl<T> Arena<T> {
/// Construct an empty arena.
pub const fn new() -> Self {
Self {
storage: Vec::new(),
len: 0,
first_free: None,
}
}
/// Construct an empty arena with space to hold exactly `capacity` elements
/// without reallocating.
pub fn with_capacity(capacity: usize) -> Self {
Self {
storage: Vec::with_capacity(capacity),
len: 0,
first_free: None,
}
}
/// Return the number of elements contained in the arena.
pub const fn len(&self) -> usize {
self.len as usize
}
/// Return the number of elements the arena can hold without allocating,
/// including the elements currently in the arena.
pub fn capacity(&self) -> usize {
self.storage.capacity()
}
/// Returns whether the arena is empty.
pub const fn is_empty(&self) -> bool {
self.len == 0
}
/// Insert a new value into the arena, returning an index that can be used
/// to later retrieve the value.
pub fn insert(&mut self, value: T) -> Index {
// This value will definitely be inserted, so we can update length now.
self.len = self
.len
.checked_add(1)
.unwrap_or_else(|| panic!("Cannot insert more than u32::MAX elements into Arena"));
// If there was a previously free entry, we can re-use its slot as long
// as we increment its generation.
if let Some(free_pointer) = self.first_free {
let slot = free_pointer.slot();
let entry = self.storage.get_mut(slot as usize).unwrap_or_else(|| {
unreachable!("first_free pointed past the end of the arena's storage")
});
let empty = entry
.as_empty()
.unwrap_or_else(|| unreachable!("first_free pointed to an occupied entry"));
// If there is another empty entry after this one, we'll update the
// arena to point to it to use it on the next insertion.
self.first_free = empty.next_free;
// Overwrite the entry directly using our mutable reference instead
// of indexing into our storage again. This should avoid an
// additional bounds check.
let generation = empty.generation.next();
*entry = Entry::Occupied(OccupiedEntry { generation, value });
Index { slot, generation }
} else {
// There were no more empty entries left in our free list, so we'll
// create a new first-generation entry and push it into storage.
let generation = Generation::first();
let slot: u32 = self.storage.len().try_into().unwrap_or_else(|_| {
unreachable!("Arena storage exceeded what can be represented by a u32")
});
self.storage
.push(Entry::Occupied(OccupiedEntry { generation, value }));
Index { slot, generation }
}
}
/// Traverse the free list and remove this known-empty slot from it, given the slot to remove
/// and the `next_free` pointer of that slot.
fn remove_slot_from_free_list(&mut self, slot: u32, new_next_free: Option<FreePointer>) {
// We will need to fix up the free list so that whatever pointer previously pointed
// to this empty entry will point to the next empty entry after it.
let mut next_fp = self
.first_free
.expect("Free entry exists but first_free is None");
// As state during this traversal, we keep the "next free" pointer which we are testing
// (which will always be `Some` as long as the free list is correct and contains this empty
// entry) as well as the current slot that contains that "next free" pointer. If the current
// slot is `None`, it means that the container of the relevant "next free" pointer is
// actually the root (`self.first_free`).
let mut current_slot = None;
while next_fp.slot() != slot {
current_slot = Some(next_fp.slot());
next_fp = self
.storage
.get(next_fp.slot() as usize)
.expect("Empty entry not in storage!")
.as_empty()
.expect("Entry in free list not actually empty!")
.next_free
.expect("Hit the end of the free list without finding the target slot!");
}
// If we found the slot to fix, then fix it; otherwise, we know that this slot is
// actually the very first in the free list, so fix it at the root.
match current_slot {
Some(slot_to_fix) => {
self.storage[slot_to_fix as usize]
.as_empty_mut()
.unwrap()
.next_free = new_next_free
}
None => self.first_free = new_next_free,
}
}
// Shared functionality between `insert_at` and `insert_at_slot`.
#[inline]
fn insert_at_inner(
&mut self,
slot: u32,
generation: Option<Generation>,
value: T,
) -> (Index, Option<T>) {
// Three cases to consider:
//
// 1.) The slot is free; we need to traverse the free list, remove it from the list, and
// then insert the value.
// 2.) The slot is occupied; we can just replace the value and return the old one.
// 3.) The slot is beyond the current length of the arena. In this case, we must extend
// the arena with new empty slots filling the free list accordingly, and then insert the
// value.
let (index, old_value) = match self.storage.get_mut(slot as usize) {
Some(Entry::Empty(empty)) => {
let generation = generation.unwrap_or_else(|| empty.generation.next());
// We will need to fix up the free list so that whatever pointer previously pointed
// to this empty entry will point to the next empty entry after it.
let new_next_free = empty.next_free;
self.remove_slot_from_free_list(slot, new_next_free);
self.storage[slot as usize] = Entry::Occupied(OccupiedEntry { generation, value });
(Index { slot, generation }, None)
}
Some(Entry::Occupied(occupied)) => {
occupied.generation = generation.unwrap_or_else(|| occupied.generation.next());
let generation = occupied.generation;
let old_value = replace(&mut occupied.value, value);
(Index { slot, generation }, Some(old_value))
}
None => {
let mut first_free = self.first_free;
while self.storage.len() < slot as usize {
let new_slot: u32 = self.storage.len().try_into().unwrap_or_else(|_| {
unreachable!("Arena storage exceeded what can be represented by a u32")
});
self.storage.push(Entry::Empty(EmptyEntry {
generation: Generation::first(),
next_free: first_free,
}));
first_free = Some(FreePointer::from_slot(new_slot));
}
self.first_free = first_free;
let generation = generation.unwrap_or_else(Generation::first);
self.storage
.push(Entry::Occupied(OccupiedEntry { generation, value }));
(Index { slot, generation }, None)
}
};
// If this insertion didn't replace an old value, then the arena now contains one more
// element; we need to update its length accordingly.
if old_value.is_none() {
self.len = self
.len
.checked_add(1)
.unwrap_or_else(|| panic!("Cannot insert more than u32::MAX elements into Arena"));
}
(index, old_value)
}
/// Insert a new value at a given index, returning the old value if present. The entry's
/// generation is set to the given index's generation.
///
/// # Caveats
///
/// This method is capable of "resurrecting" an old `Index`. This is unavoidable; if we already
/// have an occupied entry (or had) at this index of some generation M, and then `insert_at`
/// that same slot but with a generation N < M, eventually after some number of insertions and
/// removals it is possible we could end up with an index matching that old index. There are few
/// cases where this is likely to be a problem, but it is still possible.
pub fn insert_at(&mut self, index: Index, value: T) -> Option<T> {
self.insert_at_inner(index.slot, Some(index.generation), value)
.1
}
/// Insert a new value at a given slot, returning the old value if present. If the slot is
/// already occupied, this will increment the generation of the slot, and invalidate any
/// previous indices pointing to it.
pub fn insert_at_slot(&mut self, slot: u32, value: T) -> (Index, Option<T>) {
self.insert_at_inner(slot, None, value)
}
/// Returns true if the given index is valid for the arena.
pub fn contains(&self, index: Index) -> bool {
match self.storage.get(index.slot as usize) {
Some(Entry::Occupied(occupied)) if occupied.generation == index.generation => true,
_ => false,
}
}
/// Checks to see whether a slot is occupied in the arena, and if it is,
/// returns `Some` with the true `Index` of that slot (slot plus generation.)
/// Otherwise, returns `None`.
pub fn contains_slot(&self, slot: u32) -> Option<Index> {
match self.storage.get(slot as usize) {
Some(Entry::Occupied(occupied)) => Some(Index {
slot,
generation: occupied.generation,
}),
_ => None,
}
}
/// Get an immutable reference to a value inside the arena by
/// [`Index`], returning `None` if the index is not contained in the arena.
pub fn get(&self, index: Index) -> Option<&T> {
match self.storage.get(index.slot as usize) {
Some(Entry::Occupied(occupied)) if occupied.generation == index.generation => {
Some(&occupied.value)
}
_ => None,
}
}
/// Get a mutable reference to a value inside the arena by [`Index`],
/// returning `None` if the index is not contained in the arena.
pub fn get_mut(&mut self, index: Index) -> Option<&mut T> {
match self.storage.get_mut(index.slot as usize) {
Some(entry) => entry.get_value_mut(index.generation),
_ => None,
}
}
/// Get mutable references of two values inside this arena at once by
/// [`Index`], returning `None` if the corresponding `index` is not
/// contained in this arena.
///
/// # Panics
///
/// This function panics when the two indices are equal (having the same
/// slot number and generation).
pub fn get2_mut(&mut self, index1: Index, index2: Index) -> (Option<&mut T>, Option<&mut T>) {
if index1 == index2 {
panic!("Arena::get2_mut is called with two identical indices");
}
// Same entry with a different generation. We'll prefer the first value
// that matches.
if index1.slot == index2.slot {
// The borrow checker forces us to index into our storage twice here
// due to `return` extending borrows.
if self.get(index1).is_some() {
return (self.get_mut(index1), None);
} else {
return (None, self.get_mut(index2));
}
}
// If the indices point to different slots, we can mutably split the
// underlying storage to get the desired entry in each slice.
let (entry1, entry2) = if index1.slot > index2.slot {
let (slice1, slice2) = self.storage.split_at_mut(index1.slot as usize);
(slice2.get_mut(0), slice1.get_mut(index2.slot as usize))
} else {
let (slice1, slice2) = self.storage.split_at_mut(index2.slot as usize);
(slice1.get_mut(index1.slot as usize), slice2.get_mut(0))
};
(
entry1.and_then(|e| e.get_value_mut(index1.generation)),
entry2.and_then(|e| e.get_value_mut(index2.generation)),
)
}
/// Remove the value contained at the given index from the arena, returning
/// it if it was present.
pub fn remove(&mut self, index: Index) -> Option<T> {
let entry = self.storage.get_mut(index.slot as usize)?;
match entry {
Entry::Occupied(occupied) if occupied.generation == index.generation => {
// We can replace an occupied entry with an empty entry with the
// same generation. On next insertion, this generation will
// increment.
let new_entry = Entry::Empty(EmptyEntry {
generation: occupied.generation,
next_free: self.first_free,
});
// Swap our new entry into our storage and take ownership of the
// old entry. We'll consume it for its value so we can give that
// back to our caller.
let old_entry = replace(entry, new_entry);
let value = old_entry.into_value().unwrap_or_else(|| unreachable!());
// The next time we insert, we can re-use the empty entry we
// just created. If another removal happens before then, that
// entry will be used before this one (FILO).
self.first_free = Some(FreePointer::from_slot(index.slot));
self.len = self.len.checked_sub(1).unwrap_or_else(|| unreachable!());
Some(value)
}
_ => None,
}
}
/// Invalidate the given index and return a new index to the same value. This
/// is roughly equivalent to `remove` followed by `insert`, but much faster.
/// If the old index is already invalid, this method returns `None`.
pub fn invalidate(&mut self, index: Index) -> Option<Index> {
let entry = self.storage.get_mut(index.slot as usize)?;
match entry {
Entry::Occupied(occupied) if occupied.generation == index.generation => {
occupied.generation = occupied.generation.next();
Some(Index {
generation: occupied.generation,
..index
})
}
_ => None,
}
}
/// Attempt to look up the given slot in the arena, disregarding any generational
/// information, and retrieve an immutable reference to it. Returns `None` if the
/// slot is empty.
pub fn get_by_slot(&self, slot: u32) -> Option<(Index, &T)> {
match self.storage.get(slot as usize) {
Some(Entry::Occupied(occupied)) => {
let index = Index {
slot,
generation: occupied.generation,
};
Some((index, &occupied.value))
}
_ => None,
}
}
/// Attempt to look up the given slot in the arena, disregarding any generational
/// information, and retrieve a mutable reference to it. Returns `None` if the
/// slot is empty.
pub fn get_by_slot_mut(&mut self, slot: u32) -> Option<(Index, &mut T)> {
match self.storage.get_mut(slot as usize) {
Some(Entry::Occupied(occupied)) => {
let index = Index {
slot,
generation: occupied.generation,
};
Some((index, &mut occupied.value))
}
_ => None,
}
}
/// Remove an entry in the arena by its slot, disregarding any generational info.
/// Returns `None` if the slot was already empty.
pub fn remove_by_slot(&mut self, slot: u32) -> Option<(Index, T)> {
let entry = self.storage.get_mut(slot as usize)?;
match entry {
Entry::Occupied(occupied) => {
// Construct the index that would be used to access this entry.
let index = Index {
generation: occupied.generation,
slot,
};
// This occupied entry will be replaced with an empty one of the
// same generation. Generation will be incremented on the next
// insert.
let next_entry = Entry::Empty(EmptyEntry {
generation: occupied.generation,
next_free: self.first_free,
});
// Swap new entry into place and consume the old one.
let old_entry = replace(entry, next_entry);
let value = old_entry.into_value().unwrap_or_else(|| unreachable!());
// Set this entry as the next one that should be inserted into,
// should an insertion happen.
self.first_free = Some(FreePointer::from_slot(slot));
self.len = self.len.checked_sub(1).unwrap_or_else(|| unreachable!());
Some((index, value))
}
_ => None,
}
}
/// Clear the arena and drop all elements.
pub fn clear(&mut self) {
self.drain().for_each(drop);
}
/// Iterate over all of the indexes and values contained in the arena.
///
/// Iteration order is not defined.
pub fn iter(&self) -> Iter<'_, T> {
Iter {
inner: self.storage.iter(),
slot: 0,
len: self.len,
}
}
/// Iterate over all of the indexes and values contained in the arena, with
/// mutable access to each value.
///
/// Iteration order is not defined.
pub fn iter_mut(&mut self) -> IterMut<'_, T> {
IterMut {
inner: self.storage.iter_mut(),
slot: 0,
len: self.len,
}
}
/// Returns an iterator that removes each element from the arena.
///
/// Iteration order is not defined.
///
/// If the iterator is dropped before it is fully consumed, any uniterated
/// items will be dropped from the arena, and the arena will be empty.
/// The arena's capacity will not be changed.
pub fn drain(&mut self) -> Drain<'_, T> {
Drain {
arena: self,
slot: 0,
}
}
/// Remove all entries in the `Arena` which don't satisfy the provided predicate.
pub fn retain<F: FnMut(Index, &mut T) -> bool>(&mut self, mut f: F) {
for (i, entry) in self.storage.iter_mut().enumerate() {
if let Entry::Occupied(occupied) = entry {
let index = Index {
slot: i as u32,
generation: occupied.generation,
};
if !f(index, &mut occupied.value) {
// We can replace an occupied entry with an empty entry with the
// same generation. On next insertion, this generation will
// increment.
*entry = Entry::Empty(EmptyEntry {
generation: occupied.generation,
next_free: self.first_free,
});
// The next time we insert, we can re-use the empty entry we
// just created. If another removal happens before then, that
// entry will be used before this one (FILO).
self.first_free = Some(FreePointer::from_slot(index.slot));
// We just verified that this entry is (was) occupied, so there's
// trivially no way for this `checked_sub` to fail.
self.len = self.len.checked_sub(1).unwrap_or_else(|| unreachable!());
}
}
}
}
}
impl<T> Default for Arena<T> {
fn default() -> Self {
Arena::new()
}
}
impl<T> IntoIterator for Arena<T> {
type Item = (Index, T);
type IntoIter = IntoIter<T>;
fn into_iter(self) -> Self::IntoIter {
IntoIter {
arena: self,
slot: 0,
}
}
}
impl<'a, T> IntoIterator for &'a Arena<T> {
type Item = (Index, &'a T);
type IntoIter = Iter<'a, T>;
fn into_iter(self) -> Self::IntoIter {
self.iter()
}
}
impl<'a, T> IntoIterator for &'a mut Arena<T> {
type Item = (Index, &'a mut T);
type IntoIter = IterMut<'a, T>;
fn into_iter(self) -> Self::IntoIter {
self.iter_mut()
}
}
impl<T> ops::Index<Index> for Arena<T> {
type Output = T;
fn index(&self, index: Index) -> &Self::Output {
self.get(index)
.unwrap_or_else(|| panic!("No entry at index {:?}", index))
}
}
impl<T> ops::IndexMut<Index> for Arena<T> {
fn index_mut(&mut self, index: Index) -> &mut Self::Output {
self.get_mut(index)
.unwrap_or_else(|| panic!("No entry at index {:?}", index))
}
}
#[cfg(test)]
mod test {
use crate::free_pointer::FreePointer;
use super::{Arena, Generation, Index};
use core::mem::size_of;
#[test]
fn size_of_index() {
assert_eq!(size_of::<Index>(), 8);
assert_eq!(size_of::<Option<Index>>(), 8);
}
#[test]
fn new() {
let arena: Arena<u32> = Arena::new();
assert_eq!(arena.len(), 0);
assert_eq!(arena.capacity(), 0);
}
#[test]
fn with_capacity() {
let arena: Arena<u32> = Arena::with_capacity(8);
assert_eq!(arena.len(), 0);
assert_eq!(arena.capacity(), 8);
}
#[test]
fn insert_and_get() {
let mut arena = Arena::new();
let one = arena.insert(1);
assert_eq!(arena.len(), 1);
assert_eq!(arena.get(one), Some(&1));
let two = arena.insert(2);
assert_eq!(arena.len(), 2);
assert_eq!(arena.get(one), Some(&1));
assert_eq!(arena.get(two), Some(&2));
}
#[test]
fn insert_remove_get() {
let mut arena = Arena::new();
let one = arena.insert(1);
let two = arena.insert(2);
assert_eq!(arena.len(), 2);
assert!(arena.contains(two));
assert_eq!(arena.remove(two), Some(2));
assert!(!arena.contains(two));
let three = arena.insert(3);
assert_eq!(arena.len(), 2);
assert_eq!(arena.get(one), Some(&1));
assert_eq!(arena.get(three), Some(&3));
assert_eq!(arena.get(two), None);
}
#[test]
fn insert_remove_get_by_slot() {
let mut arena = Arena::new();
let one = arena.insert(1);
let two = arena.insert(2);
assert_eq!(arena.len(), 2);
assert!(arena.contains(two));
assert_eq!(arena.remove_by_slot(two.slot()), Some((two, 2)));
assert!(!arena.contains(two));
assert_eq!(arena.get_by_slot(two.slot()), None);
let three = arena.insert(3);
assert_eq!(arena.len(), 2);
assert_eq!(arena.get(one), Some(&1));
assert_eq!(arena.get(three), Some(&3));
assert_eq!(arena.get(two), None);
assert_eq!(arena.get_by_slot(two.slot()), Some((three, &3)));
}
#[test]
fn insert_at() {
let mut arena = Arena::new();
// Numbers definitely not chosen by fair dice roll
let index = Index {
slot: 42,
generation: Generation::from_u32(78).unwrap(),
};
arena.insert_at(index, 5);
assert_eq!(arena.len(), 1);
assert_eq!(arena.get(index), Some(&5));
assert_eq!(arena.get_by_slot(42), Some((index, &5)));
}
#[test]
fn insert_at_first_slot() {
let mut arena = Arena::new();
// Numbers definitely not chosen by fair dice roll
let index = Index {
slot: 0,
generation: Generation::from_u32(3).unwrap(),
};
arena.insert_at(index, 5);
assert_eq!(arena.len(), 1);
assert_eq!(arena.get(index), Some(&5));
assert_eq!(arena.get_by_slot(0), Some((index, &5)));
}
#[test]
fn insert_at_slot() {
let mut arena = Arena::new();
let (index, _) = arena.insert_at_slot(42, 5);
assert_eq!(arena.len(), 1);
assert_eq!(arena.get(index), Some(&5));
assert_eq!(arena.get_by_slot(42), Some((index, &5)));
}
#[test]
fn insert_at_middle() {
let mut arena = Arena::new();
arena.insert_at_slot(4, 50);
arena.insert_at_slot(2, 40);
let empty = arena.storage.get(3).unwrap().as_empty().unwrap();
if empty.next_free != Some(FreePointer::from_slot(1)) {
panic!("Invalid free list: {:#?}", arena);
}
}
#[test]
fn get_mut() {
let mut arena = Arena::new();
let foo = arena.insert(5);
let handle = arena.get_mut(foo).unwrap();
*handle = 6;
assert_eq!(arena.get(foo), Some(&6));
}
#[test]
fn get2_mut() {
let mut arena = Arena::new();
let foo = arena.insert(100);
let bar = arena.insert(500);
let (foo_handle, bar_handle) = arena.get2_mut(foo, bar);
let foo_handle = foo_handle.unwrap();
let bar_handle = bar_handle.unwrap();
*foo_handle = 105;
*bar_handle = 505;
assert_eq!(arena.get(foo), Some(&105));
assert_eq!(arena.get(bar), Some(&505));
}
#[test]
fn get2_mut_reversed_order() {
let mut arena = Arena::new();
let foo = arena.insert(100);
let bar = arena.insert(500);
let (bar_handle, foo_handle) = arena.get2_mut(bar, foo);
let foo_handle = foo_handle.unwrap();
let bar_handle = bar_handle.unwrap();
*foo_handle = 105;
*bar_handle = 505;
assert_eq!(arena.get(foo), Some(&105));
assert_eq!(arena.get(bar), Some(&505));
}
#[test]
fn get2_mut_non_exist_handle() {
let mut arena = Arena::new();
let foo = arena.insert(100);
let bar = arena.insert(500);
arena.remove(bar);
let (bar_handle, foo_handle) = arena.get2_mut(bar, foo);
let foo_handle = foo_handle.unwrap();
assert!(bar_handle.is_none());
*foo_handle = 105;
assert_eq!(arena.get(foo), Some(&105));
}
#[test]
fn get2_mut_same_slot_different_generation() {
let mut arena = Arena::new();
let foo = arena.insert(100);
let mut foo1 = foo;
foo1.generation = foo1.generation.next();
let (foo_handle, foo1_handle) = arena.get2_mut(foo, foo1);
assert!(foo_handle.is_some());
assert!(foo1_handle.is_none());
}
#[test]
#[should_panic]
fn get2_mut_panics() {
let mut arena = Arena::new();
let foo = arena.insert(100);
arena.get2_mut(foo, foo);
}
#[test]
fn insert_remove_insert_capacity() {
let mut arena = Arena::with_capacity(2);
assert_eq!(arena.capacity(), 2);
let a = arena.insert("a");
let b = arena.insert("b");
assert_eq!(arena.len(), 2);
assert_eq!(arena.capacity(), 2);
arena.remove(a);
arena.remove(b);
assert_eq!(arena.len(), 0);
assert_eq!(arena.capacity(), 2);
let _a2 = arena.insert("a2");
let _b2 = arena.insert("b2");
assert_eq!(arena.len(), 2);
assert_eq!(arena.capacity(), 2);
}
#[test]
fn invalidate() {
let mut arena = Arena::new();
let a = arena.insert("a");
assert_eq!(arena.get(a), Some(&"a"));
let new_a = arena.invalidate(a).unwrap();
assert_eq!(arena.get(a), None);
assert_eq!(arena.get(new_a), Some(&"a"));
}
#[test]
fn retain() {
let mut arena = Arena::new();
for i in 0..100 {
arena.insert(i);
}
arena.retain(|_, &mut i| i % 2 == 1);
for (_, i) in arena.iter() {
assert_eq!(i % 2, 1);
}
assert_eq!(arena.len(), 50);
}
#[test]
fn index_bits_roundtrip() {
let index = Index::from_bits(0x1BAD_CAFE_DEAD_BEEF).unwrap();
assert_eq!(index.to_bits(), 0x1BAD_CAFE_DEAD_BEEF);
}
#[test]
fn index_bits_none_on_zero_generation() {
let index = Index::from_bits(0x0000_0000_DEAD_BEEF);
assert_eq!(index, None);
}
}