1use super::plumbing::*;
2use super::*;
3
4use std::fmt::{self, Debug};
5
6/// `FlatMap` maps each element to a parallel iterator, then flattens these iterators together.
7/// This struct is created by the [`flat_map()`] method on [`ParallelIterator`]
8///
9/// [`flat_map()`]: trait.ParallelIterator.html#method.flat_map
10/// [`ParallelIterator`]: trait.ParallelIterator.html
11#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
12#[derive(Clone)]
13pub struct FlatMap<I: ParallelIterator, F> {
14 base: I,
15 map_op: F,
16}
17
18impl<I: ParallelIterator + Debug, F> Debug for FlatMap<I, F> {
19 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
20 f.debug_struct("FlatMap").field(name:"base", &self.base).finish()
21 }
22}
23
24impl<I: ParallelIterator, F> FlatMap<I, F> {
25 /// Creates a new `FlatMap` iterator.
26 pub(super) fn new(base: I, map_op: F) -> Self {
27 FlatMap { base, map_op }
28 }
29}
30
31impl<I, F, PI> ParallelIterator for FlatMap<I, F>
32where
33 I: ParallelIterator,
34 F: Fn(I::Item) -> PI + Sync + Send,
35 PI: IntoParallelIterator,
36{
37 type Item = PI::Item;
38
39 fn drive_unindexed<C>(self, consumer: C) -> C::Result
40 where
41 C: UnindexedConsumer<Self::Item>,
42 {
43 let consumer: FlatMapConsumer<'_, C, F> = FlatMapConsumer::new(base:consumer, &self.map_op);
44 self.base.drive_unindexed(consumer)
45 }
46}
47
48/// ////////////////////////////////////////////////////////////////////////
49/// Consumer implementation
50
51struct FlatMapConsumer<'f, C, F> {
52 base: C,
53 map_op: &'f F,
54}
55
56impl<'f, C, F> FlatMapConsumer<'f, C, F> {
57 fn new(base: C, map_op: &'f F) -> Self {
58 FlatMapConsumer { base, map_op }
59 }
60}
61
62impl<'f, T, U, C, F> Consumer<T> for FlatMapConsumer<'f, C, F>
63where
64 C: UnindexedConsumer<U::Item>,
65 F: Fn(T) -> U + Sync,
66 U: IntoParallelIterator,
67{
68 type Folder = FlatMapFolder<'f, C, F, C::Result>;
69 type Reducer = C::Reducer;
70 type Result = C::Result;
71
72 fn split_at(self, index: usize) -> (Self, Self, C::Reducer) {
73 let (left, right, reducer) = self.base.split_at(index);
74 (
75 FlatMapConsumer::new(left, self.map_op),
76 FlatMapConsumer::new(right, self.map_op),
77 reducer,
78 )
79 }
80
81 fn into_folder(self) -> Self::Folder {
82 FlatMapFolder {
83 base: self.base,
84 map_op: self.map_op,
85 previous: None,
86 }
87 }
88
89 fn full(&self) -> bool {
90 self.base.full()
91 }
92}
93
94impl<'f, T, U, C, F> UnindexedConsumer<T> for FlatMapConsumer<'f, C, F>
95where
96 C: UnindexedConsumer<U::Item>,
97 F: Fn(T) -> U + Sync,
98 U: IntoParallelIterator,
99{
100 fn split_off_left(&self) -> Self {
101 FlatMapConsumer::new(self.base.split_off_left(), self.map_op)
102 }
103
104 fn to_reducer(&self) -> Self::Reducer {
105 self.base.to_reducer()
106 }
107}
108
109struct FlatMapFolder<'f, C, F, R> {
110 base: C,
111 map_op: &'f F,
112 previous: Option<R>,
113}
114
115impl<'f, T, U, C, F> Folder<T> for FlatMapFolder<'f, C, F, C::Result>
116where
117 C: UnindexedConsumer<U::Item>,
118 F: Fn(T) -> U + Sync,
119 U: IntoParallelIterator,
120{
121 type Result = C::Result;
122
123 fn consume(self, item: T) -> Self {
124 let map_op = self.map_op;
125 let par_iter = map_op(item).into_par_iter();
126 let consumer = self.base.split_off_left();
127 let result = par_iter.drive_unindexed(consumer);
128
129 let previous = match self.previous {
130 None => Some(result),
131 Some(previous) => {
132 let reducer = self.base.to_reducer();
133 Some(reducer.reduce(previous, result))
134 }
135 };
136
137 FlatMapFolder {
138 base: self.base,
139 map_op,
140 previous,
141 }
142 }
143
144 fn complete(self) -> Self::Result {
145 match self.previous {
146 Some(previous) => previous,
147 None => self.base.into_folder().complete(),
148 }
149 }
150
151 fn full(&self) -> bool {
152 self.base.full()
153 }
154}
155