94 lines
2.3 KiB
Rust
94 lines
2.3 KiB
Rust
use super::noop::NoopConsumer;
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use super::plumbing::*;
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use super::*;
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/// `Skip` is an iterator that skips over the first `n` elements.
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/// This struct is created by the [`skip()`] method on [`IndexedParallelIterator`]
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///
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/// [`skip()`]: IndexedParallelIterator::skip()
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#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
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#[derive(Debug, Clone)]
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pub struct Skip<I> {
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base: I,
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n: usize,
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}
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impl<I> Skip<I>
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where
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I: IndexedParallelIterator,
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{
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/// Creates a new `Skip` iterator.
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pub(super) fn new(base: I, n: usize) -> Self {
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let n = Ord::min(base.len(), n);
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Skip { base, n }
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}
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}
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impl<I> ParallelIterator for Skip<I>
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where
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I: IndexedParallelIterator,
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{
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type Item = I::Item;
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fn drive_unindexed<C>(self, consumer: C) -> C::Result
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where
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C: UnindexedConsumer<Self::Item>,
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{
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bridge(self, consumer)
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}
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fn opt_len(&self) -> Option<usize> {
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Some(self.len())
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}
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}
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impl<I> IndexedParallelIterator for Skip<I>
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where
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I: IndexedParallelIterator,
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{
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fn len(&self) -> usize {
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self.base.len() - self.n
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}
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fn drive<C: Consumer<Self::Item>>(self, consumer: C) -> C::Result {
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bridge(self, consumer)
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}
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fn with_producer<CB>(self, callback: CB) -> CB::Output
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where
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CB: ProducerCallback<Self::Item>,
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{
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return self.base.with_producer(Callback {
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callback,
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n: self.n,
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});
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struct Callback<CB> {
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callback: CB,
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n: usize,
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}
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impl<T, CB> ProducerCallback<T> for Callback<CB>
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where
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CB: ProducerCallback<T>,
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{
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type Output = CB::Output;
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fn callback<P>(self, base: P) -> CB::Output
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where
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P: Producer<Item = T>,
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{
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crate::in_place_scope(|scope| {
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let Self { callback, n } = self;
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let (before_skip, after_skip) = base.split_at(n);
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// Run the skipped part separately for side effects.
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// We'll still get any panics propagated back by the scope.
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scope.spawn(move |_| bridge_producer_consumer(n, before_skip, NoopConsumer));
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callback.callback(after_skip)
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})
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}
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}
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}
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}
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