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use std::{iter, ops::ControlFlow};
use crate::collector::{Collector, CollectorBase};
use super::Fuse;
/// A collector that lets both collectors collect the same item.
///
/// This `struct` is created by [`CollectorBase::tee_funnel()`].
/// See its documentation for more.
#[derive(Debug, Clone)]
pub struct TeeFunnel<C1, C2> {
collector1: Fuse<C1>,
collector2: Fuse<C2>,
}
impl<C1, C2> TeeFunnel<C1, C2>
where
C1: CollectorBase,
C2: CollectorBase,
{
pub(in crate::collector) fn new(collector1: C1, collector2: C2) -> Self {
Self {
collector1: Fuse::new(collector1),
collector2: Fuse::new(collector2),
}
}
}
impl<C1, C2> CollectorBase for TeeFunnel<C1, C2>
where
C1: CollectorBase,
C2: CollectorBase,
{
type Output = (C1::Output, C2::Output);
#[inline]
fn finish(self) -> Self::Output {
(self.collector1.finish(), self.collector2.finish())
}
#[inline]
fn break_hint(&self) -> ControlFlow<()> {
// We're sure that whether this collector has finished or not is
// entirely based on the 2nd collector.
// Also, by this method being called it is assumed that
// this collector has not finished, which mean the 2nd collector
// has not finished, which means it's always sound to call here.
//
// Since the 1st collector is fused, we won't cause any unsoundness
// by repeatedly calling it.
if self.collector1.break_hint().is_break() && self.collector2.break_hint().is_break() {
ControlFlow::Break(())
} else {
ControlFlow::Continue(())
}
}
}
impl<T, C1, C2> Collector<T> for TeeFunnel<C1, C2>
where
C1: for<'a> Collector<&'a mut T>,
C2: Collector<T>,
{
#[inline]
fn collect(&mut self, mut item: T) -> ControlFlow<()> {
match (
self.collector1.collect(&mut item),
self.collector2.collect(item),
) {
(ControlFlow::Break(_), ControlFlow::Break(_)) => ControlFlow::Break(()),
_ => ControlFlow::Continue(()),
}
}
// fn reserve(&mut self, additional_min: usize, additional_max: Option<usize>) {
// let (lower1, upper1) = self.collector1.size_hint();
// // Both have the same theme: the 2nd collector reserves the left-over amount.
// let (reserve_lower1, reserve_lower2) = if additional_min > lower1 {
// (lower1, additional_min - lower1)
// } else {
// (additional_min, 0)
// };
// let (reserve_upper1, reserve_upper2) = match (additional_max, upper1) {
// (Some(additional_max), Some(upper1)) if additional_max > upper1 => {
// (Some(upper1), Some(additional_max - upper1))
// }
// (additional_max, _) => (additional_max, Some(0)),
// };
// self.collector1.reserve(reserve_lower1, reserve_upper1);
// self.collector2.reserve(reserve_lower2, reserve_upper2);
// }
// fn size_hint(&self) -> (usize, Option<usize>) {
// let (lower1, upper1) = self.collector1.size_hint();
// let (lower2, upper2) = self.collector2.size_hint();
// (
// lower1.saturating_add(lower2),
// (|| upper1?.checked_add(upper2?))(),
// )
// }
// fn inactivity_hint(&self) -> Option<usize> {
// match (
// self.collector1.inactivity_hint(),
// self.collector2.inactivity_hint(),
// ) {
// (Some(count1), Some(count2)) => Some(count1.min(count2)),
// (Some(count), None) | (None, Some(count)) => Some(count),
// (None, None) => None,
// }
// }
// fn skip_till_active(&mut self, max: Option<usize>) {
// match (
// self.collector1.inactivity_hint(),
// self.collector2.inactivity_hint(),
// ) {
// (Some(count1), Some(count2)) => {
// let max = match max {
// Some(max) => max.min(count1.min(count2)),
// None => count1.min(count2),
// };
// self.collector1.skip_till_active(Some(max));
// self.collector2.skip_till_active(Some(max));
// }
// (Some(_), None) => {
// self.collector1.skip_till_active(max);
// }
// (None, Some(_)) => {
// self.collector2.skip_till_active(max);
// }
// (None, None) => {}
// }
// }
fn collect_many(&mut self, items: impl IntoIterator<Item = T>) -> ControlFlow<()> {
self.break_hint()?;
let mut items = items.into_iter();
match items.try_for_each(|mut item| {
// We don't need to check like the `collect` implementation.
// `self.break_hint()?` has already handled it,
// and we trust that both underlying collectors
// return `Break` as soon as it can't afford more items.
if self.collector1.collect(&mut item).is_break() {
ControlFlow::Break(Which::First(item))
} else {
self.collector2.collect(item).map_break(|_| Which::Second)
}
}) {
ControlFlow::Break(Which::First(item)) => {
self.collector2.collect_many(iter::once(item).chain(items))
}
ControlFlow::Break(Which::Second) => {
// Sadly, we cannot use `collect_many` since we have an iterator of `T`,
// but the collector expects `&mut T`, and we have no way to
// map from `T` to `&mut T`.
items.try_for_each(|mut item| self.collector1.collect(&mut item))
}
ControlFlow::Continue(_) => ControlFlow::Continue(()),
}
}
fn collect_then_finish(mut self, items: impl IntoIterator<Item = T>) -> Self::Output {
if self.break_hint().is_break() {
return self.finish();
}
let mut items = items.into_iter();
match items.try_for_each(|mut item| {
// We don't need to check like the `collect` implementation.
// `self.break_hint()?` has already handled it,
// and we trust that both underlying collectors
// return `Break` as soon as it can't afford more items.
if self.collector1.collect(&mut item).is_break() {
ControlFlow::Break(Which::First(item))
} else {
self.collector2.collect(item).map_break(|_| Which::Second)
}
}) {
// If one of the collectors has stopped, we can avoid cloning
// for the rest of the items!
ControlFlow::Break(Which::First(item)) => (
self.collector1.finish(),
self.collector2
.collect_then_finish(iter::once(item).chain(items)),
),
ControlFlow::Break(Which::Second) => {
let _ = items.try_for_each(|mut item| self.collector1.collect(&mut item));
self.finish()
}
ControlFlow::Continue(_) => self.finish(),
}
}
}
enum Which<T> {
First(T),
Second,
}
#[cfg(all(test, feature = "std"))]
mod proptests {
use proptest::collection::vec as propvec;
use proptest::prelude::*;
use proptest::test_runner::TestCaseResult;
use crate::prelude::*;
use crate::test_utils::{BasicCollectorTester, CollectorTesterExt, PredError};
proptest! {
/// Precondition:
/// - [`crate::collector::Collector::take()`]
/// - [`crate::vec::IntoCollector`]
#[test]
fn all_collect_methods(
nums in propvec(any::<i32>(), ..=4),
first_count in ..=4_usize,
second_count in ..=4_usize,
) {
all_collect_methods_impl(nums, first_count, second_count)?;
}
}
fn all_collect_methods_impl(
nums: Vec<i32>,
first_count: usize,
second_count: usize,
) -> TestCaseResult {
BasicCollectorTester {
iter_factory: || nums.iter().copied(),
collector_factory: || {
vec![]
.into_collector()
.copying()
.take(first_count)
.tee_funnel(vec![].into_collector().take(second_count))
},
should_break_pred: |iter| iter.count() >= first_count.max(second_count),
pred: |iter, output, remaining| {
let first = iter.clone().take(first_count).collect::<Vec<_>>();
let second = iter.clone().take(second_count).collect::<Vec<_>>();
let max_len = first_count.max(second_count);
if output != (first, second) {
Err(PredError::IncorrectOutput)
} else if iter.skip(max_len).ne(remaining) {
Err(PredError::IncorrectIterConsumption)
} else {
Ok(())
}
},
}
.test_collector()
}
}