naga/arena/
handlevec.rs

1//! The [`HandleVec`] type and associated definitions.
2
3use super::handle::Handle;
4use alloc::{vec, vec::Vec};
5
6use core::marker::PhantomData;
7use core::ops;
8
9/// A [`Vec`] indexed by [`Handle`]s.
10///
11/// A `HandleVec<T, U>` is a [`Vec<U>`] indexed by values of type `Handle<T>`,
12/// rather than `usize`.
13///
14/// Rather than a `push` method, `HandleVec` has an [`insert`] method, analogous
15/// to [`HashMap::insert`], that requires you to provide the handle at which the
16/// new value should appear. However, since `HandleVec` only supports insertion
17/// at the end, the given handle's index must be equal to the the `HandleVec`'s
18/// current length; otherwise, the insertion will panic.
19///
20/// [`insert`]: HandleVec::insert
21/// [`HashMap::insert`]: hashbrown::HashMap::insert
22#[derive(Debug)]
23pub(crate) struct HandleVec<T, U> {
24    inner: Vec<U>,
25    as_keys: PhantomData<T>,
26}
27
28impl<T, U> Default for HandleVec<T, U> {
29    fn default() -> Self {
30        Self {
31            inner: vec![],
32            as_keys: PhantomData,
33        }
34    }
35}
36
37#[allow(dead_code)]
38impl<T, U> HandleVec<T, U> {
39    pub(crate) const fn new() -> Self {
40        Self {
41            inner: vec![],
42            as_keys: PhantomData,
43        }
44    }
45
46    pub(crate) fn with_capacity(capacity: usize) -> Self {
47        Self {
48            inner: Vec::with_capacity(capacity),
49            as_keys: PhantomData,
50        }
51    }
52
53    pub(crate) fn len(&self) -> usize {
54        self.inner.len()
55    }
56
57    /// Insert a mapping from `handle` to `value`.
58    ///
59    /// Unlike a [`HashMap`], a `HandleVec` can only have new entries inserted at
60    /// the end, like [`Vec::push`]. So the index of `handle` must equal
61    /// [`self.len()`].
62    ///
63    /// [`HashMap`]: hashbrown::HashMap
64    /// [`self.len()`]: HandleVec::len
65    pub(crate) fn insert(&mut self, handle: Handle<T>, value: U) {
66        assert_eq!(handle.index(), self.inner.len());
67        self.inner.push(value);
68    }
69
70    pub(crate) fn get(&self, handle: Handle<T>) -> Option<&U> {
71        self.inner.get(handle.index())
72    }
73
74    pub(crate) fn clear(&mut self) {
75        self.inner.clear()
76    }
77
78    pub(crate) fn resize(&mut self, len: usize, fill: U)
79    where
80        U: Clone,
81    {
82        self.inner.resize(len, fill);
83    }
84
85    pub(crate) fn iter(&self) -> impl Iterator<Item = &U> {
86        self.inner.iter()
87    }
88
89    pub(crate) fn iter_mut(&mut self) -> impl Iterator<Item = &mut U> {
90        self.inner.iter_mut()
91    }
92}
93
94impl<T, U> ops::Index<Handle<T>> for HandleVec<T, U> {
95    type Output = U;
96
97    fn index(&self, handle: Handle<T>) -> &Self::Output {
98        &self.inner[handle.index()]
99    }
100}
101
102impl<T, U> ops::IndexMut<Handle<T>> for HandleVec<T, U> {
103    fn index_mut(&mut self, handle: Handle<T>) -> &mut Self::Output {
104        &mut self.inner[handle.index()]
105    }
106}
naga/arena/handlevec.rs

naga/arena/
handlevec.rs
