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//! Arena.
#[cfg(not(feature = "std"))]
use core::ops::{Index, IndexMut};
#[cfg(feature = "std")]
use std::ops::{Index, IndexMut};
use generational_arena::Arena as GenerationalArena;
#[cfg(feature = "deser")]
use serde::{Deserialize, Serialize};
#[cfg(feature = "par_iter")]
use rayon::prelude::*;
use crate::{Node, NodeId};
#[derive(Clone)]
#[cfg_attr(feature = "deser", derive(Deserialize, Serialize))]
/// An `Arena` structure containing certain [`Node`]s.
///
/// [`Node`]: struct.Node.html
pub struct Arena<T> {
pub(crate) nodes: GenerationalArena<Node<T>>,
}
impl<T> Arena<T> {
/// Creates a new empty `Arena`.
pub fn new() -> Arena<T> {
Self::default()
}
/// Create a new empty `Arena` with pre-allocated memory for `n` items.
pub fn with_capacity(n: usize) -> Arena<T> {
Self {
nodes: GenerationalArena::with_capacity(n),
}
}
/// Creates a new node from its associated data.
///
/// # Panics
///
/// Panics if the arena already has `usize::max_value()` nodes.
///
/// # Examples
///
/// ```
/// # use generational_indextree::Arena;
/// let mut arena = Arena::new();
/// let foo = arena.new_node("foo");
///
/// assert_eq!(*arena[foo].get(), "foo");
/// ```
pub fn new_node(&mut self, data: T) -> NodeId {
NodeId::from_index(self.nodes.insert(Node::new(data)))
}
/// Creates a new node via specified `create` function.
///
/// `create` is called with the new node's node ID, allowing nodes that know their own ID.
///
/// # Panics
///
/// Panics if the arena already has `usize::max_value()` nodes.
///
/// # Examples
///
/// ```
/// # use generational_indextree::{Arena, NodeId};
/// let mut arena = Arena::new();
/// struct A { id: NodeId, val: u32 }
/// let foo = arena.new_node_with(|id| A { id, val: 10 });
///
/// assert_eq!(arena[foo].get().val, 10);
/// assert_eq!(arena[foo].get().id, foo);
/// ```
pub fn new_node_with(&mut self, create: impl FnOnce(NodeId) -> T) -> NodeId {
NodeId::from_index(
self.nodes
.insert_with(|idx| Node::new(create(NodeId::from_index(idx)))),
)
}
/// Counts the number of nodes in arena and returns it.
///
/// # Examples
///
/// ```
/// # use generational_indextree::Arena;
/// let mut arena = Arena::new();
/// let foo = arena.new_node("foo");
/// let _bar = arena.new_node("bar");
/// assert_eq!(arena.count(), 2);
///
/// foo.remove(&mut arena);
/// assert_eq!(arena.count(), 1);
/// ```
pub fn count(&self) -> usize {
self.nodes.len()
}
/// Returns `true` if arena has no nodes, `false` otherwise.
///
/// # Examples
///
/// ```
/// # use generational_indextree::Arena;
/// let mut arena = Arena::new();
/// assert!(arena.is_empty());
///
/// let foo = arena.new_node("foo");
/// assert!(!arena.is_empty());
///
/// foo.remove(&mut arena);
/// assert!(arena.is_empty());
/// ```
pub fn is_empty(&self) -> bool {
self.count() == 0
}
/// Returns a reference to the node with the given id if in the arena.
///
/// Returns `None` if not available.
///
/// # Examples
///
/// ```
/// # use generational_indextree::{Arena, NodeId};
/// let mut arena = Arena::new();
/// let foo = arena.new_node("foo");
/// assert_eq!(arena.get(foo).map(|node| *node.get()), Some("foo"));
/// ```
///
/// Note that this does not check whether the given node ID is created by
/// the arena.
///
/// ```
/// # use generational_indextree::Arena;
/// let mut arena = Arena::new();
/// let foo = arena.new_node("foo");
/// let bar = arena.new_node("bar");
/// assert_eq!(arena.get(foo).map(|node| *node.get()), Some("foo"));
///
/// let mut another_arena = Arena::new();
/// let _ = another_arena.new_node("Another arena");
/// assert_eq!(another_arena.get(foo).map(|node| *node.get()), Some("Another arena"));
/// assert!(another_arena.get(bar).is_none());
/// ```
pub fn get(&self, id: NodeId) -> Option<&Node<T>> {
self.nodes.get(id.get_index())
}
/// Returns a mutable reference to the node with the given id if in the
/// arena.
///
/// Returns `None` if not available.
///
/// # Examples
///
/// ```
/// # use generational_indextree::{Arena, NodeId};
/// let mut arena = Arena::new();
/// let foo = arena.new_node("foo");
/// assert_eq!(arena.get(foo).map(|node| *node.get()), Some("foo"));
///
/// *arena.get_mut(foo).expect("The `foo` node exists").get_mut() = "FOO!";
/// assert_eq!(arena.get(foo).map(|node| *node.get()), Some("FOO!"));
/// ```
pub fn get_mut(&mut self, id: NodeId) -> Option<&mut Node<T>> {
self.nodes.get_mut(id.get_index())
}
/// Get a pair of exclusive references to the elements at index `i1` and `i2` if it is in the
/// arena.
///
/// If the element at index `i1` or `i2` is not in the arena, then `None` is returned for this
/// element.
///
/// # Panics
///
/// Panics if `i1` and `i2` are pointing to the same item of the arena.
///
/// # Examples
///
/// ```
/// use generational_indextree::Arena;
///
/// let mut arena = Arena::new();
/// let idx1 = arena.new_node("foo");
/// let idx2 = arena.new_node("bar");
///
/// {
/// let (item1, item2) = arena.get2_mut(idx1, idx2);
///
/// *item1.unwrap().get_mut() = "jig";
/// *item2.unwrap().get_mut() = "saw";
/// }
///
/// assert_eq!(arena[idx1].get(), &"jig");
/// assert_eq!(arena[idx2].get(), &"saw");
/// ```
pub fn get2_mut(
&mut self,
i1: NodeId,
i2: NodeId,
) -> (Option<&mut Node<T>>, Option<&mut Node<T>>) {
self.nodes.get2_mut(i1.get_index(), i2.get_index())
}
/// Returns an iterator of all nodes in the arena in storage-order.
///
/// # Examples
///
/// ```
/// # use generational_indextree::Arena;
/// let mut arena = Arena::new();
/// let _foo = arena.new_node("foo");
/// let _bar = arena.new_node("bar");
///
/// let mut iter = arena.iter();
/// assert_eq!(iter.next().map(|node| *node.get()), Some("foo"));
/// assert_eq!(iter.next().map(|node| *node.get()), Some("bar"));
/// assert_eq!(iter.next().map(|node| *node.get()), None);
/// ```
///
/// ```
/// # use generational_indextree::Arena;
/// let mut arena = Arena::new();
/// let _foo = arena.new_node("foo");
/// let bar = arena.new_node("bar");
/// bar.remove(&mut arena);
///
/// let mut iter = arena.iter();
/// assert_eq!(iter.next().map(|node| *node.get()), Some("foo"));
/// assert_eq!(iter.next().map(|node| *node.get()), None);
/// ```
pub fn iter(&self) -> impl Iterator<Item = &Node<T>> {
self.nodes.iter().map(|pair| pair.1)
}
/// Returns an iterator of all pairs (NodeId, &Node<T>) in the arena in storage-order.
///
/// ```
/// # use generational_indextree::Arena;
/// let mut arena = Arena::new();
/// let _foo = arena.new_node("foo");
/// let _bar = arena.new_node("bar");
///
/// let mut iter = arena.iter_pairs();
/// assert_eq!(iter.next().map(|node| (node.0, *node.1.get())), Some((_foo, "foo")));
/// assert_eq!(iter.next().map(|node| (node.0, *node.1.get())), Some((_bar, "bar")));
/// assert_eq!(iter.next().map(|node| (node.0, *node.1.get())), None);
/// ```
pub fn iter_pairs(&self) -> impl Iterator<Item = (NodeId, &Node<T>)> {
self.nodes
.iter()
.map(|pair| (NodeId::from_index(pair.0), pair.1))
}
}
impl<T> Default for Arena<T> {
fn default() -> Self {
Self {
nodes: GenerationalArena::new(),
}
}
}
impl<T: core::fmt::Debug> core::fmt::Debug for Arena<T> {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
f.debug_list()
.entries(self.nodes.iter().map(|(idx, node)| (idx, &node.data)))
.finish()
}
}
impl<T> Index<NodeId> for Arena<T> {
type Output = Node<T>;
fn index(&self, node: NodeId) -> &Node<T> {
&self.nodes[node.get_index()]
}
}
impl<T> IndexMut<NodeId> for Arena<T> {
fn index_mut(&mut self, node: NodeId) -> &mut Node<T> {
&mut self.nodes[node.get_index()]
}
}
impl<T: PartialEq> PartialEq for Arena<T> {
fn eq(&self, other: &Self) -> bool {
let mut equal = self.nodes.len() == other.nodes.len();
let mut self_iter = self.iter();
let mut other_iter = other.iter();
while equal {
let lhs = self_iter.next();
let rhs = other_iter.next();
equal = lhs == rhs;
if lhs.is_none() {
break;
}
}
equal
}
}
impl<T: PartialEq> Eq for Arena<T> {}
#[test]
fn reuse_node() {
let mut arena = Arena::with_capacity(3);
let n1_id = arena.new_node("1");
let n2_id = arena.new_node("2");
let n3_id = arena.new_node("3");
n1_id.remove(&mut arena);
n2_id.remove(&mut arena);
n3_id.remove(&mut arena);
let new_n1_id = arena.new_node("1");
let new_n2_id = arena.new_node("2");
let new_n3_id = arena.new_node("3");
assert_eq!(arena.nodes.len(), 3);
assert_ne!(n1_id, new_n1_id);
assert_ne!(n2_id, new_n2_id);
assert_ne!(n3_id, new_n3_id);
}
#[cfg(feature = "std")]
#[test]
fn debug_arena() {
let mut arena = Arena::with_capacity(10);
let _n1_id = arena.new_node("1");
let n2_id = arena.new_node("2");
let n3_id = arena.new_node("3");
let n4_id = arena.new_node("4");
let _n5_id = arena.new_node("5");
n2_id.remove(&mut arena);
n3_id.remove(&mut arena);
n4_id.remove(&mut arena);
let _n6_id = arena.new_node("6");
assert_eq!(
format!("{:?}", arena),
"[(Index { index: 0, generation: 0 }, \"1\"), (Index { index: 3, generation: 3 }, \"6\"), (Index { index: 4, generation: 0 }, \"5\")]"
);
}