cranelift_entity/
keys.rs

1//! A double-ended iterator over entity references.
2//!
3//! When `core::iter::Step` is stabilized, `Keys` could be implemented as a wrapper around
4//! `core::ops::Range`, but for now, we implement it manually.
5
6use crate::EntityRef;
7use core::marker::PhantomData;
8
9/// Iterate over all keys in order.
10pub struct Keys<K: EntityRef> {
11    pos: usize,
12    rev_pos: usize,
13    unused: PhantomData<K>,
14}
15
16impl<K: EntityRef> Keys<K> {
17    /// Create a `Keys` iterator that visits `len` entities starting from 0.
18    pub fn with_len(len: usize) -> Self {
19        Self {
20            pos: 0,
21            rev_pos: len,
22            unused: PhantomData,
23        }
24    }
25}
26
27impl<K: EntityRef> Iterator for Keys<K> {
28    type Item = K;
29
30    fn next(&mut self) -> Option<Self::Item> {
31        if self.pos < self.rev_pos {
32            let k = K::new(self.pos);
33            self.pos += 1;
34            Some(k)
35        } else {
36            None
37        }
38    }
39
40    fn size_hint(&self) -> (usize, Option<usize>) {
41        let size = self.rev_pos - self.pos;
42        (size, Some(size))
43    }
44}
45
46impl<K: EntityRef> DoubleEndedIterator for Keys<K> {
47    fn next_back(&mut self) -> Option<Self::Item> {
48        if self.rev_pos > self.pos {
49            let k = K::new(self.rev_pos - 1);
50            self.rev_pos -= 1;
51            Some(k)
52        } else {
53            None
54        }
55    }
56}
57
58impl<K: EntityRef> ExactSizeIterator for Keys<K> {}
cranelift_entity/keys.rs

cranelift_entity/
keys.rs
