1 use super::plumbing::*;
2 use super::*;
3 
4 use std::fmt::{self, Debug};
5 
6 /// `Positions` takes a predicate `predicate` and filters out elements that match,
7 /// yielding their indices.
8 ///
9 /// This struct is created by the [`positions()`] method on [`IndexedParallelIterator`]
10 ///
11 /// [`positions()`]: trait.IndexedParallelIterator.html#method.positions
12 /// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
13 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
14 #[derive(Clone)]
15 pub struct Positions<I: IndexedParallelIterator, P> {
16     base: I,
17     predicate: P,
18 }
19 
20 impl<I: IndexedParallelIterator + Debug, P> Debug for Positions<I, P> {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result21     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
22         f.debug_struct("Positions")
23             .field("base", &self.base)
24             .finish()
25     }
26 }
27 
28 impl<I, P> Positions<I, P>
29 where
30     I: IndexedParallelIterator,
31 {
32     /// Create a new `Positions` iterator.
new(base: I, predicate: P) -> Self33     pub(super) fn new(base: I, predicate: P) -> Self {
34         Positions { base, predicate }
35     }
36 }
37 
38 impl<I, P> ParallelIterator for Positions<I, P>
39 where
40     I: IndexedParallelIterator,
41     P: Fn(I::Item) -> bool + Sync + Send,
42 {
43     type Item = usize;
44 
drive_unindexed<C>(self, consumer: C) -> C::Result where C: UnindexedConsumer<Self::Item>,45     fn drive_unindexed<C>(self, consumer: C) -> C::Result
46     where
47         C: UnindexedConsumer<Self::Item>,
48     {
49         let consumer1 = PositionsConsumer::new(consumer, &self.predicate, 0);
50         self.base.drive(consumer1)
51     }
52 }
53 
54 /// ////////////////////////////////////////////////////////////////////////
55 /// Consumer implementation
56 
57 struct PositionsConsumer<'p, C, P> {
58     base: C,
59     predicate: &'p P,
60     offset: usize,
61 }
62 
63 impl<'p, C, P> PositionsConsumer<'p, C, P> {
new(base: C, predicate: &'p P, offset: usize) -> Self64     fn new(base: C, predicate: &'p P, offset: usize) -> Self {
65         PositionsConsumer {
66             base,
67             predicate,
68             offset,
69         }
70     }
71 }
72 
73 impl<'p, T, C, P> Consumer<T> for PositionsConsumer<'p, C, P>
74 where
75     C: Consumer<usize>,
76     P: Fn(T) -> bool + Sync,
77 {
78     type Folder = PositionsFolder<'p, C::Folder, P>;
79     type Reducer = C::Reducer;
80     type Result = C::Result;
81 
split_at(self, index: usize) -> (Self, Self, C::Reducer)82     fn split_at(self, index: usize) -> (Self, Self, C::Reducer) {
83         let (left, right, reducer) = self.base.split_at(index);
84         (
85             PositionsConsumer::new(left, self.predicate, self.offset),
86             PositionsConsumer::new(right, self.predicate, self.offset + index),
87             reducer,
88         )
89     }
90 
into_folder(self) -> Self::Folder91     fn into_folder(self) -> Self::Folder {
92         PositionsFolder {
93             base: self.base.into_folder(),
94             predicate: self.predicate,
95             offset: self.offset,
96         }
97     }
98 
full(&self) -> bool99     fn full(&self) -> bool {
100         self.base.full()
101     }
102 }
103 
104 struct PositionsFolder<'p, F, P> {
105     base: F,
106     predicate: &'p P,
107     offset: usize,
108 }
109 
110 impl<F, P, T> Folder<T> for PositionsFolder<'_, F, P>
111 where
112     F: Folder<usize>,
113     P: Fn(T) -> bool,
114 {
115     type Result = F::Result;
116 
consume(mut self, item: T) -> Self117     fn consume(mut self, item: T) -> Self {
118         let index = self.offset;
119         self.offset += 1;
120         if (self.predicate)(item) {
121             self.base = self.base.consume(index);
122         }
123         self
124     }
125 
126     // This cannot easily specialize `consume_iter` to be better than
127     // the default, because that requires checking `self.base.full()`
128     // during a call to `self.base.consume_iter()`. (#632)
129 
complete(self) -> Self::Result130     fn complete(self) -> Self::Result {
131         self.base.complete()
132     }
133 
full(&self) -> bool134     fn full(&self) -> bool {
135         self.base.full()
136     }
137 }
138