bulks 0.11.3

Amazing bulks! They are like iterators, but in bulk, and therefore support collection into arrays.
Documentation 
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
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150

use core::{
    pin::Pin,
    task::{Context, Poll}
};

use array_trait::AsSlice;

use crate::{
    BulkLength,
    util::{Buffer, BufferableBulk, MaybeDone}
};

pub struct ReduceAsync<B, F>
where
    B: BufferableBulk,
    F: FnMut<(B::Item, B::Item), Output: Future<Output = B::Item>>
{
    queue: B::IntoIter,
    tasks: Buffer<MaybeDone<F::Output>, BulkLength<B>>,
    action: F
}
impl<B, F> ReduceAsync<B, F>
where
    B: BufferableBulk,
    F: FnMut<(B::Item, B::Item), Output: Future<Output = B::Item>>
{
    pub(crate) fn new(bulk: B, action: F) -> Self
    where
        B: IntoIterator
    {
        let len = bulk.length();
        Self {
            queue: bulk.into_iter(),
            tasks: Buffer::new(len),
            action
        }
    }

    fn tasks(self: Pin<&mut Self>) -> Pin<&mut [MaybeDone<F::Output>]>
    {
        unsafe { self.map_unchecked_mut(|this| this.tasks.as_mut_slice()) }
    }

    fn task(self: Pin<&mut Self>, i: usize) -> Pin<&mut MaybeDone<F::Output>>
    {
        unsafe { self.tasks().map_unchecked_mut(|tasks| &mut tasks[i]) }
    }

    fn action(self: Pin<&mut Self>) -> &mut F
    {
        unsafe { &mut self.get_unchecked_mut().action }
    }

    fn queue(self: Pin<&mut Self>) -> &mut B::IntoIter
    {
        unsafe { &mut self.get_unchecked_mut().queue }
    }

    fn push_task(self: Pin<&mut Self>, lhs: B::Item, rhs: Option<B::Item>) -> Pin<&mut MaybeDone<F::Output>>
    {
        match rhs
        {
            Some(rhs) =>
            unsafe { self.map_unchecked_mut(|this| this.tasks.push_mut(MaybeDone::Future((this.action)(lhs, rhs)))) },
            None =>
            unsafe { self.map_unchecked_mut(|this| this.tasks.push_mut(MaybeDone::Done(lhs))) }
        }
    }
}

impl<B, F> Future for ReduceAsync<B, F>
where
    B: BufferableBulk,
    F: FnMut<(B::Item, B::Item), Output: Future<Output = B::Item>>
{
    type Output = Option<B::Item>;

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>
    {
        let mut ready = true;
        while let Some(lhs) = self.as_mut().queue().next()
        {
            let rhs = self.as_mut().queue().next();
            let task = self.as_mut().push_task(lhs, rhs);
            ready &= task.poll(cx).is_ready()
        }

        let len = self.tasks.len();

        let mut i = 0;
        let mut j = None;
        while i < len
        {
            if !self.as_mut().task(i).is_taken()
            {
                if self.as_mut().task(i).poll(cx).is_ready()
                {
                    match j.take()
                    {
                        None => j = Some(i),
                        Some(j) =>
                        {
                            let lhs = self.as_mut().task(j).take_output().unwrap();
                            let rhs = self.as_mut().task(i).take_output().unwrap();
                            let future = self.as_mut().action()(lhs, rhs);
                            self.as_mut().task(i).restart(future);
                            continue;
                        }
                    }
                }
                else
                {
                    ready = false
                }
            }
            i += 1
        }

        if ready
        {
            match j
            {
                Some(j) => Poll::Ready(self.task(j).take_output()),
                None => Poll::Ready(None)
            }
        }
        else
        {
            Poll::Pending
        }
    }
}

#[cfg(test)]
mod test
{
    use crate::{Bulk, IntoBulk};

    #[test]
    fn it_works()
    {
        let a = [1, 2, 3];

        tokio::runtime::Builder::new_multi_thread().enable_all().build().unwrap().block_on(async {
            let n = a.into_bulk().reduce_async(async |a, b| a + b).await;

            assert_eq!(n, Some(1 + 2 + 3))
        })
    }
}