//! Parallel iterator types for [results][std::result]
//!
//! You will rarely need to interact with this module directly unless you need
//! to name one of the iterator types.
//!
//! [std::result]:
https://doc.rust-lang.org/stable/std/result/
use crate::iter::plumbing::*;
use crate::iter::*;
use std::sync::Mutex;
use crate::option;
/// Parallel iterator over a result
#[derive(Debug, Clone)]
pub struct IntoIter<T: Send> {
inner: option::IntoIter<T>,
}
impl<T: Send, E> IntoParallelIterator for Result<T, E> {
type Item = T;
type Iter = IntoIter<T>;
fn into_par_iter(self) -> Self::Iter {
IntoIter {
inner: self.ok().into_par_iter(),
}
}
}
delegate_indexed_iterator! {
IntoIter<T> => T,
impl<T: Send>
}
/// Parallel iterator over an immutable reference to a result
#[derive(Debug)]
pub struct Iter<'a, T: Sync> {
inner: option::IntoIter<&'a T>,
}
impl<'a, T: Sync> Clone for Iter<'a, T> {
fn clone(&self) -> Self {
Iter {
inner: self.inner.clone(),
}
}
}
impl<'a, T: Sync, E> IntoParallelIterator for &'a Result<T, E> {
type Item = &'a T;
type Iter = Iter<'a, T>;
fn into_par_iter(self) -> Self::Iter {
Iter {
inner: self.as_ref().ok().into_par_iter(),
}
}
}
delegate_indexed_iterator! {
Iter<'a, T> => &'a T,
impl<'a, T: Sync + 'a>
}
/// Parallel iterator over a mutable reference to a result
#[derive(Debug)]
pub struct IterMut<'a, T: Send> {
inner: option::IntoIter<&'a mut T>,
}
impl<'a, T: Send, E> IntoParallelIterator for &'a mut Result<T, E> {
type Item = &'a mut T;
type Iter = IterMut<'a, T>;
fn into_par_iter(self) -> Self::Iter {
IterMut {
inner: self.as_mut().ok().into_par_iter(),
}
}
}
delegate_indexed_iterator! {
IterMut<'a, T> => &'a mut T,
impl<'a, T: Send + 'a>
}
/// Collect an arbitrary `Result`-wrapped collection.
///
/// If any item is `Err`, then all previous `Ok` items collected are
/// discarded, and it returns that error. If there are multiple errors, the
/// one returned is not deterministic.
impl<C, T, E> FromParallelIterator<Result<T, E>> for Result<C, E>
where
C: FromParallelIterator<T>,
T: Send,
E: Send,
{
fn from_par_iter<I>(par_iter: I) -> Self
where
I: IntoParallelIterator<Item = Result<T, E>>,
{
fn ok<T, E>(saved: &Mutex<Option<E>>) -> impl Fn(Result<T, E>) -> Option<T> + '_ {
move |item| match item {
Ok(item) => Some(item),
Err(error) => {
// We don't need a blocking `lock()`, as anybody
// else holding the lock will also be writing
// `Some(error)`, and then ours is irrelevant.
if let Ok(mut guard) = saved.try_lock() {
if guard.is_none() {
*guard = Some(error);
}
}
None
}
}
}
let saved_error = Mutex::new(None);
let collection = par_iter
.into_par_iter()
.map(ok(&saved_error))
.while_some()
.collect();
match saved_error.into_inner().unwrap() {
Some(error) => Err(error),
None => Ok(collection),
}
}
}
