Sha256: b8c2fba26dee15bf3d1880bb2b41e8d66fe1428d242ee6d9fd30ee94bbd0407d
Contents?: true
Size: 1.39 KB
Versions: 39
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Stored size: 1.39 KB
Contents
//! A double-ended iterator over entity references.
//!
//! When `core::iter::Step` is stabilized, `Keys` could be implemented as a wrapper around
//! `core::ops::Range`, but for now, we implement it manually.
use crate::EntityRef;
use core::marker::PhantomData;
/// Iterate over all keys in order.
pub struct Keys<K: EntityRef> {
pos: usize,
rev_pos: usize,
unused: PhantomData<K>,
}
impl<K: EntityRef> Keys<K> {
/// Create a `Keys` iterator that visits `len` entities starting from 0.
pub fn with_len(len: usize) -> Self {
Self {
pos: 0,
rev_pos: len,
unused: PhantomData,
}
}
}
impl<K: EntityRef> Iterator for Keys<K> {
type Item = K;
fn next(&mut self) -> Option<Self::Item> {
if self.pos < self.rev_pos {
let k = K::new(self.pos);
self.pos += 1;
Some(k)
} else {
None
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let size = self.rev_pos - self.pos;
(size, Some(size))
}
}
impl<K: EntityRef> DoubleEndedIterator for Keys<K> {
fn next_back(&mut self) -> Option<Self::Item> {
if self.rev_pos > self.pos {
let k = K::new(self.rev_pos - 1);
self.rev_pos -= 1;
Some(k)
} else {
None
}
}
}
impl<K: EntityRef> ExactSizeIterator for Keys<K> {}
Version data entries
39 entries across 39 versions & 1 rubygems