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//! Yet another index-based arena.
#![warn(missing_docs)]
use std::{
fmt,
hash::{Hash, Hasher},
iter::FromIterator,
marker::PhantomData,
ops::{Index, IndexMut},
};
mod map;
pub use map::ArenaMap;
/// The raw index of a value in an arena.
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct RawIdx(u32);
impl From<RawIdx> for u32 {
fn from(raw: RawIdx) -> u32 {
raw.0
}
}
impl From<u32> for RawIdx {
fn from(idx: u32) -> RawIdx {
RawIdx(idx)
}
}
impl fmt::Debug for RawIdx {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
self.0.fmt(f)
}
}
impl fmt::Display for RawIdx {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
self.0.fmt(f)
}
}
/// The index of a value allocated in an arena that holds `T`s.
pub struct Idx<T> {
raw: RawIdx,
_ty: PhantomData<fn() -> T>,
}
impl<T> Clone for Idx<T> {
fn clone(&self) -> Self {
*self
}
}
impl<T> Copy for Idx<T> {}
impl<T> PartialEq for Idx<T> {
fn eq(&self, other: &Idx<T>) -> bool {
self.raw == other.raw
}
}
impl<T> Eq for Idx<T> {}
impl<T> Hash for Idx<T> {
fn hash<H: Hasher>(&self, state: &mut H) {
self.raw.hash(state)
}
}
impl<T> fmt::Debug for Idx<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut type_name = std::any::type_name::<T>();
if let Some(idx) = type_name.rfind(':') {
type_name = &type_name[idx + 1..]
}
write!(f, "Idx::<{}>({})", type_name, self.raw)
}
}
impl<T> Idx<T> {
/// Creates a new index from a [`RawIdx`].
pub fn from_raw(raw: RawIdx) -> Self {
Idx { raw, _ty: PhantomData }
}
/// Converts this index into the underlying [`RawIdx`].
pub fn into_raw(self) -> RawIdx {
self.raw
}
}
/// Yet another index-based arena.
#[derive(Clone, PartialEq, Eq)]
pub struct Arena<T> {
data: Vec<T>,
}
impl<T: fmt::Debug> fmt::Debug for Arena<T> {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
fmt.debug_struct("Arena").field("len", &self.len()).field("data", &self.data).finish()
}
}
impl<T> Arena<T> {
/// Creates a new empty arena.
///
/// ```
/// let arena: la_arena::Arena<i32> = la_arena::Arena::new();
/// assert!(arena.is_empty());
/// ```
pub const fn new() -> Arena<T> {
Arena { data: Vec::new() }
}
/// Empties the arena, removing all contained values.
///
/// ```
/// let mut arena = la_arena::Arena::new();
///
/// arena.alloc(1);
/// arena.alloc(2);
/// arena.alloc(3);
/// assert_eq!(arena.len(), 3);
///
/// arena.clear();
/// assert!(arena.is_empty());
/// ```
pub fn clear(&mut self) {
self.data.clear();
}
/// Returns the length of the arena.
///
/// ```
/// let mut arena = la_arena::Arena::new();
/// assert_eq!(arena.len(), 0);
///
/// arena.alloc("foo");
/// assert_eq!(arena.len(), 1);
///
/// arena.alloc("bar");
/// assert_eq!(arena.len(), 2);
///
/// arena.alloc("baz");
/// assert_eq!(arena.len(), 3);
/// ```
pub fn len(&self) -> usize {
self.data.len()
}
/// Returns whether the arena contains no elements.
///
/// ```
/// let mut arena = la_arena::Arena::new();
/// assert!(arena.is_empty());
///
/// arena.alloc(0.5);
/// assert!(!arena.is_empty());
/// ```
pub fn is_empty(&self) -> bool {
self.data.is_empty()
}
/// Allocates a new value on the arena, returning the value’s index.
///
/// ```
/// let mut arena = la_arena::Arena::new();
/// let idx = arena.alloc(50);
///
/// assert_eq!(arena[idx], 50);
/// ```
pub fn alloc(&mut self, value: T) -> Idx<T> {
let idx = RawIdx(self.data.len() as u32);
self.data.push(value);
Idx::from_raw(idx)
}
/// Returns an iterator over the arena’s elements.
///
/// ```
/// let mut arena = la_arena::Arena::new();
/// let idx1 = arena.alloc(20);
/// let idx2 = arena.alloc(40);
/// let idx3 = arena.alloc(60);
///
/// let mut iterator = arena.iter();
/// assert_eq!(iterator.next(), Some((idx1, &20)));
/// assert_eq!(iterator.next(), Some((idx2, &40)));
/// assert_eq!(iterator.next(), Some((idx3, &60)));
/// ```
pub fn iter(
&self,
) -> impl Iterator<Item = (Idx<T>, &T)> + ExactSizeIterator + DoubleEndedIterator {
self.data.iter().enumerate().map(|(idx, value)| (Idx::from_raw(RawIdx(idx as u32)), value))
}
/// Reallocates the arena to make it take up as little space as possible.
pub fn shrink_to_fit(&mut self) {
self.data.shrink_to_fit();
}
}
impl<T> Default for Arena<T> {
fn default() -> Arena<T> {
Arena { data: Vec::new() }
}
}
impl<T> Index<Idx<T>> for Arena<T> {
type Output = T;
fn index(&self, idx: Idx<T>) -> &T {
let idx = idx.into_raw().0 as usize;
&self.data[idx]
}
}
impl<T> IndexMut<Idx<T>> for Arena<T> {
fn index_mut(&mut self, idx: Idx<T>) -> &mut T {
let idx = idx.into_raw().0 as usize;
&mut self.data[idx]
}
}
impl<T> FromIterator<T> for Arena<T> {
fn from_iter<I>(iter: I) -> Self
where
I: IntoIterator<Item = T>,
{
Arena { data: Vec::from_iter(iter) }
}
}
|
