1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131

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),
        }
    }
}