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