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use super::plumbing::*;
use super::ParallelIterator;
use super::Try;
use std::ops::ControlFlow::{self, Break, Continue};
use std::sync::atomic::{AtomicBool, Ordering};
pub(super) fn try_reduce<PI, R, ID, T>(pi: PI, identity: ID, reduce_op: R) -> T
where
PI: ParallelIterator<Item = T>,
R: Fn(T::Output, T::Output) -> T + Sync,
ID: Fn() -> T::Output + Sync,
T: Try + Send,
{
let full = AtomicBool::new(false);
let consumer = TryReduceConsumer {
identity: &identity,
reduce_op: &reduce_op,
full: &full,
};
pi.drive_unindexed(consumer)
}
struct TryReduceConsumer<'r, R, ID> {
identity: &'r ID,
reduce_op: &'r R,
full: &'r AtomicBool,
}
impl<'r, R, ID> Copy for TryReduceConsumer<'r, R, ID> {}
impl<'r, R, ID> Clone for TryReduceConsumer<'r, R, ID> {
fn clone(&self) -> Self {
*self
}
}
impl<'r, R, ID, T> Consumer<T> for TryReduceConsumer<'r, R, ID>
where
R: Fn(T::Output, T::Output) -> T + Sync,
ID: Fn() -> T::Output + Sync,
T: Try + Send,
{
type Folder = TryReduceFolder<'r, R, T>;
type Reducer = Self;
type Result = T;
fn split_at(self, _index: usize) -> (Self, Self, Self) {
(self, self, self)
}
fn into_folder(self) -> Self::Folder {
TryReduceFolder {
reduce_op: self.reduce_op,
control: Continue((self.identity)()),
full: self.full,
}
}
fn full(&self) -> bool {
self.full.load(Ordering::Relaxed)
}
}
impl<'r, R, ID, T> UnindexedConsumer<T> for TryReduceConsumer<'r, R, ID>
where
R: Fn(T::Output, T::Output) -> T + Sync,
ID: Fn() -> T::Output + Sync,
T: Try + Send,
{
fn split_off_left(&self) -> Self {
*self
}
fn to_reducer(&self) -> Self::Reducer {
*self
}
}
impl<'r, R, ID, T> Reducer<T> for TryReduceConsumer<'r, R, ID>
where
R: Fn(T::Output, T::Output) -> T + Sync,
T: Try,
{
fn reduce(self, left: T, right: T) -> T {
match (left.branch(), right.branch()) {
(Continue(left), Continue(right)) => (self.reduce_op)(left, right),
(Break(r), _) | (_, Break(r)) => T::from_residual(r),
}
}
}
struct TryReduceFolder<'r, R, T: Try> {
reduce_op: &'r R,
control: ControlFlow<T::Residual, T::Output>,
full: &'r AtomicBool,
}
impl<'r, R, T> Folder<T> for TryReduceFolder<'r, R, T>
where
R: Fn(T::Output, T::Output) -> T,
T: Try,
{
type Result = T;
fn consume(mut self, item: T) -> Self {
let reduce_op = self.reduce_op;
self.control = match (self.control, item.branch()) {
(Continue(left), Continue(right)) => reduce_op(left, right).branch(),
(control @ Break(_), _) | (_, control @ Break(_)) => control,
};
if let Break(_) = self.control {
self.full.store(true, Ordering::Relaxed);
}
self
}
fn complete(self) -> T {
match self.control {
Continue(c) => T::from_output(c),
Break(r) => T::from_residual(r),
}
}
fn full(&self) -> bool {
match self.control {
Break(_) => true,
_ => self.full.load(Ordering::Relaxed),
}
}
}