7720a571fc
A `DoubleEndedIterator` needs to track both a forward position and a reverse position, so that `next_back()` can pop from the back of the sequence.
118 lines
2.8 KiB
Rust
118 lines
2.8 KiB
Rust
//! A double-ended iterator over entity references and entities.
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use EntityRef;
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use std::marker::PhantomData;
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use std::slice;
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/// Iterate over all keys in order.
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pub struct Iter<'a, K: EntityRef, V>
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where
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V: 'a,
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{
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pos: usize,
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rev_pos: usize,
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iter: slice::Iter<'a, V>,
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unused: PhantomData<K>,
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}
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impl<'a, K: EntityRef, V> Iter<'a, K, V> {
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/// Create an `Iter` iterator that visits the `PrimaryMap` keys and values
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/// of `iter`.
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pub fn new(iter: slice::Iter<'a, V>) -> Self {
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Self {
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pos: 0,
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rev_pos: iter.len(),
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iter,
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unused: PhantomData,
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}
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}
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}
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impl<'a, K: EntityRef, V> Iterator for Iter<'a, K, V> {
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type Item = (K, &'a V);
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fn next(&mut self) -> Option<Self::Item> {
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if let Some(next) = self.iter.next() {
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let pos = self.pos;
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self.pos += 1;
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Some((K::new(pos), next))
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} else {
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None
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}
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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self.iter.size_hint()
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}
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}
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impl<'a, K: EntityRef, V> DoubleEndedIterator for Iter<'a, K, V> {
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fn next_back(&mut self) -> Option<Self::Item> {
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if let Some(next_back) = self.iter.next_back() {
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let rev_pos = self.rev_pos - 1;
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self.rev_pos -= 1;
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Some((K::new(rev_pos), next_back))
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} else {
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None
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}
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}
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}
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impl<'a, K: EntityRef, V> ExactSizeIterator for Iter<'a, K, V> {}
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/// Iterate over all keys in order.
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pub struct IterMut<'a, K: EntityRef, V>
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where
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V: 'a,
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{
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pos: usize,
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rev_pos: usize,
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iter: slice::IterMut<'a, V>,
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unused: PhantomData<K>,
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}
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impl<'a, K: EntityRef, V> IterMut<'a, K, V> {
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/// Create an `IterMut` iterator that visits the `PrimaryMap` keys and values
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/// of `iter`.
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pub fn new(iter: slice::IterMut<'a, V>) -> Self {
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Self {
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pos: 0,
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rev_pos: iter.len(),
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iter,
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unused: PhantomData,
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}
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}
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}
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impl<'a, K: EntityRef, V> Iterator for IterMut<'a, K, V> {
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type Item = (K, &'a mut V);
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fn next(&mut self) -> Option<Self::Item> {
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if let Some(next) = self.iter.next() {
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let pos = self.pos;
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self.pos += 1;
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Some((K::new(pos), next))
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} else {
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None
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}
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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self.iter.size_hint()
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}
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}
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impl<'a, K: EntityRef, V> DoubleEndedIterator for IterMut<'a, K, V> {
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fn next_back(&mut self) -> Option<Self::Item> {
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if let Some(next_back) = self.iter.next_back() {
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let rev_pos = self.rev_pos - 1;
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self.rev_pos -= 1;
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Some((K::new(rev_pos), next_back))
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} else {
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None
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}
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}
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}
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impl<'a, K: EntityRef, V> ExactSizeIterator for IterMut<'a, K, V> {}
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