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use super::plumbing::*;
use super::*;
use std::fmt::{self, Debug};
/// `Positions` takes a predicate `predicate` and filters out elements that match,
/// yielding their indices.
///
/// This struct is created by the [`positions()`] method on [`IndexedParallelIterator`]
///
/// [`positions()`]: trait.IndexedParallelIterator.html#method.positions
/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Clone)]
pub struct Positions<I: IndexedParallelIterator, P> {
base: I,
predicate: P,
}
impl<I: IndexedParallelIterator + Debug, P> Debug for Positions<I, P> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Positions")
.field("base", &self.base)
.finish()
}
}
impl<I, P> Positions<I, P>
where
I: IndexedParallelIterator,
{
/// Create a new `Positions` iterator.
pub(super) fn new(base: I, predicate: P) -> Self {
Positions { base, predicate }
}
}
impl<I, P> ParallelIterator for Positions<I, P>
where
I: IndexedParallelIterator,
P: Fn(I::Item) -> bool + Sync + Send,
{
type Item = usize;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
let consumer1 = PositionsConsumer::new(consumer, &self.predicate, 0);
self.base.drive(consumer1)
}
}
/// ////////////////////////////////////////////////////////////////////////
/// Consumer implementation
struct PositionsConsumer<'p, C, P> {
base: C,
predicate: &'p P,
offset: usize,
}
impl<'p, C, P> PositionsConsumer<'p, C, P> {
fn new(base: C, predicate: &'p P, offset: usize) -> Self {
PositionsConsumer {
base,
predicate,
offset,
}
}
}
impl<'p, T, C, P> Consumer<T> for PositionsConsumer<'p, C, P>
where
C: Consumer<usize>,
P: Fn(T) -> bool + Sync,
{
type Folder = PositionsFolder<'p, C::Folder, P>;
type Reducer = C::Reducer;
type Result = C::Result;
fn split_at(self, index: usize) -> (Self, Self, C::Reducer) {
let (left, right, reducer) = self.base.split_at(index);
(
PositionsConsumer::new(left, self.predicate, self.offset),
PositionsConsumer::new(right, self.predicate, self.offset + index),
reducer,
)
}
fn into_folder(self) -> Self::Folder {
PositionsFolder {
base: self.base.into_folder(),
predicate: self.predicate,
offset: self.offset,
}
}
fn full(&self) -> bool {
self.base.full()
}
}
struct PositionsFolder<'p, F, P> {
base: F,
predicate: &'p P,
offset: usize,
}
impl<F, P, T> Folder<T> for PositionsFolder<'_, F, P>
where
F: Folder<usize>,
P: Fn(T) -> bool,
{
type Result = F::Result;
fn consume(mut self, item: T) -> Self {
let index = self.offset;
self.offset += 1;
if (self.predicate)(item) {
self.base = self.base.consume(index);
}
self
}
// This cannot easily specialize `consume_iter` to be better than
// the default, because that requires checking `self.base.full()`
// during a call to `self.base.consume_iter()`. (#632)
fn complete(self) -> Self::Result {
self.base.complete()
}
fn full(&self) -> bool {
self.base.full()
}
}