1 use super::plumbing::*;
2 use super::*;
3 use std::sync::atomic::{AtomicBool, Ordering};
4 use std::thread;
5 
6 /// `PanicFuse` is an adaptor that wraps an iterator with a fuse in case
7 /// of panics, to halt all threads as soon as possible.
8 ///
9 /// This struct is created by the [`panic_fuse()`] method on [`ParallelIterator`]
10 ///
11 /// [`panic_fuse()`]: trait.ParallelIterator.html#method.panic_fuse
12 /// [`ParallelIterator`]: trait.ParallelIterator.html
13 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
14 #[derive(Debug, Clone)]
15 pub struct PanicFuse<I: ParallelIterator> {
16     base: I,
17 }
18 
19 /// Helper that sets a bool to `true` if dropped while unwinding.
20 #[derive(Clone)]
21 struct Fuse<'a>(&'a AtomicBool);
22 
23 impl<'a> Drop for Fuse<'a> {
24     #[inline]
drop(&mut self)25     fn drop(&mut self) {
26         if thread::panicking() {
27             self.0.store(true, Ordering::Relaxed);
28         }
29     }
30 }
31 
32 impl<'a> Fuse<'a> {
33     #[inline]
panicked(&self) -> bool34     fn panicked(&self) -> bool {
35         self.0.load(Ordering::Relaxed)
36     }
37 }
38 
39 impl<I> PanicFuse<I>
40 where
41     I: ParallelIterator,
42 {
43     /// Creates a new `PanicFuse` iterator.
new(base: I) -> PanicFuse<I>44     pub(super) fn new(base: I) -> PanicFuse<I> {
45         PanicFuse { base }
46     }
47 }
48 
49 impl<I> ParallelIterator for PanicFuse<I>
50 where
51     I: ParallelIterator,
52 {
53     type Item = I::Item;
54 
drive_unindexed<C>(self, consumer: C) -> C::Result where C: UnindexedConsumer<Self::Item>,55     fn drive_unindexed<C>(self, consumer: C) -> C::Result
56     where
57         C: UnindexedConsumer<Self::Item>,
58     {
59         let panicked = AtomicBool::new(false);
60         let consumer1 = PanicFuseConsumer {
61             base: consumer,
62             fuse: Fuse(&panicked),
63         };
64         self.base.drive_unindexed(consumer1)
65     }
66 
opt_len(&self) -> Option<usize>67     fn opt_len(&self) -> Option<usize> {
68         self.base.opt_len()
69     }
70 }
71 
72 impl<I> IndexedParallelIterator for PanicFuse<I>
73 where
74     I: IndexedParallelIterator,
75 {
drive<C>(self, consumer: C) -> C::Result where C: Consumer<Self::Item>,76     fn drive<C>(self, consumer: C) -> C::Result
77     where
78         C: Consumer<Self::Item>,
79     {
80         let panicked = AtomicBool::new(false);
81         let consumer1 = PanicFuseConsumer {
82             base: consumer,
83             fuse: Fuse(&panicked),
84         };
85         self.base.drive(consumer1)
86     }
87 
len(&self) -> usize88     fn len(&self) -> usize {
89         self.base.len()
90     }
91 
with_producer<CB>(self, callback: CB) -> CB::Output where CB: ProducerCallback<Self::Item>,92     fn with_producer<CB>(self, callback: CB) -> CB::Output
93     where
94         CB: ProducerCallback<Self::Item>,
95     {
96         return self.base.with_producer(Callback { callback });
97 
98         struct Callback<CB> {
99             callback: CB,
100         }
101 
102         impl<T, CB> ProducerCallback<T> for Callback<CB>
103         where
104             CB: ProducerCallback<T>,
105         {
106             type Output = CB::Output;
107 
108             fn callback<P>(self, base: P) -> CB::Output
109             where
110                 P: Producer<Item = T>,
111             {
112                 let panicked = AtomicBool::new(false);
113                 let producer = PanicFuseProducer {
114                     base,
115                     fuse: Fuse(&panicked),
116                 };
117                 self.callback.callback(producer)
118             }
119         }
120     }
121 }
122 
123 /// ////////////////////////////////////////////////////////////////////////
124 /// Producer implementation
125 
126 struct PanicFuseProducer<'a, P> {
127     base: P,
128     fuse: Fuse<'a>,
129 }
130 
131 impl<'a, P> Producer for PanicFuseProducer<'a, P>
132 where
133     P: Producer,
134 {
135     type Item = P::Item;
136     type IntoIter = PanicFuseIter<'a, P::IntoIter>;
137 
into_iter(self) -> Self::IntoIter138     fn into_iter(self) -> Self::IntoIter {
139         PanicFuseIter {
140             base: self.base.into_iter(),
141             fuse: self.fuse,
142         }
143     }
144 
min_len(&self) -> usize145     fn min_len(&self) -> usize {
146         self.base.min_len()
147     }
max_len(&self) -> usize148     fn max_len(&self) -> usize {
149         self.base.max_len()
150     }
151 
split_at(self, index: usize) -> (Self, Self)152     fn split_at(self, index: usize) -> (Self, Self) {
153         let (left, right) = self.base.split_at(index);
154         (
155             PanicFuseProducer {
156                 base: left,
157                 fuse: self.fuse.clone(),
158             },
159             PanicFuseProducer {
160                 base: right,
161                 fuse: self.fuse,
162             },
163         )
164     }
165 
fold_with<G>(self, folder: G) -> G where G: Folder<Self::Item>,166     fn fold_with<G>(self, folder: G) -> G
167     where
168         G: Folder<Self::Item>,
169     {
170         let folder1 = PanicFuseFolder {
171             base: folder,
172             fuse: self.fuse,
173         };
174         self.base.fold_with(folder1).base
175     }
176 }
177 
178 struct PanicFuseIter<'a, I> {
179     base: I,
180     fuse: Fuse<'a>,
181 }
182 
183 impl<'a, I> Iterator for PanicFuseIter<'a, I>
184 where
185     I: Iterator,
186 {
187     type Item = I::Item;
188 
next(&mut self) -> Option<Self::Item>189     fn next(&mut self) -> Option<Self::Item> {
190         if self.fuse.panicked() {
191             None
192         } else {
193             self.base.next()
194         }
195     }
196 
size_hint(&self) -> (usize, Option<usize>)197     fn size_hint(&self) -> (usize, Option<usize>) {
198         self.base.size_hint()
199     }
200 }
201 
202 impl<'a, I> DoubleEndedIterator for PanicFuseIter<'a, I>
203 where
204     I: DoubleEndedIterator,
205 {
next_back(&mut self) -> Option<Self::Item>206     fn next_back(&mut self) -> Option<Self::Item> {
207         if self.fuse.panicked() {
208             None
209         } else {
210             self.base.next_back()
211         }
212     }
213 }
214 
215 impl<'a, I> ExactSizeIterator for PanicFuseIter<'a, I>
216 where
217     I: ExactSizeIterator,
218 {
len(&self) -> usize219     fn len(&self) -> usize {
220         self.base.len()
221     }
222 }
223 
224 /// ////////////////////////////////////////////////////////////////////////
225 /// Consumer implementation
226 
227 struct PanicFuseConsumer<'a, C> {
228     base: C,
229     fuse: Fuse<'a>,
230 }
231 
232 impl<'a, T, C> Consumer<T> for PanicFuseConsumer<'a, C>
233 where
234     C: Consumer<T>,
235 {
236     type Folder = PanicFuseFolder<'a, C::Folder>;
237     type Reducer = PanicFuseReducer<'a, C::Reducer>;
238     type Result = C::Result;
239 
split_at(self, index: usize) -> (Self, Self, Self::Reducer)240     fn split_at(self, index: usize) -> (Self, Self, Self::Reducer) {
241         let (left, right, reducer) = self.base.split_at(index);
242         (
243             PanicFuseConsumer {
244                 base: left,
245                 fuse: self.fuse.clone(),
246             },
247             PanicFuseConsumer {
248                 base: right,
249                 fuse: self.fuse.clone(),
250             },
251             PanicFuseReducer {
252                 base: reducer,
253                 _fuse: self.fuse,
254             },
255         )
256     }
257 
into_folder(self) -> Self::Folder258     fn into_folder(self) -> Self::Folder {
259         PanicFuseFolder {
260             base: self.base.into_folder(),
261             fuse: self.fuse,
262         }
263     }
264 
full(&self) -> bool265     fn full(&self) -> bool {
266         self.fuse.panicked() || self.base.full()
267     }
268 }
269 
270 impl<'a, T, C> UnindexedConsumer<T> for PanicFuseConsumer<'a, C>
271 where
272     C: UnindexedConsumer<T>,
273 {
split_off_left(&self) -> Self274     fn split_off_left(&self) -> Self {
275         PanicFuseConsumer {
276             base: self.base.split_off_left(),
277             fuse: self.fuse.clone(),
278         }
279     }
280 
to_reducer(&self) -> Self::Reducer281     fn to_reducer(&self) -> Self::Reducer {
282         PanicFuseReducer {
283             base: self.base.to_reducer(),
284             _fuse: self.fuse.clone(),
285         }
286     }
287 }
288 
289 struct PanicFuseFolder<'a, C> {
290     base: C,
291     fuse: Fuse<'a>,
292 }
293 
294 impl<'a, T, C> Folder<T> for PanicFuseFolder<'a, C>
295 where
296     C: Folder<T>,
297 {
298     type Result = C::Result;
299 
consume(mut self, item: T) -> Self300     fn consume(mut self, item: T) -> Self {
301         self.base = self.base.consume(item);
302         self
303     }
304 
consume_iter<I>(mut self, iter: I) -> Self where I: IntoIterator<Item = T>,305     fn consume_iter<I>(mut self, iter: I) -> Self
306     where
307         I: IntoIterator<Item = T>,
308     {
309         fn cool<'a, T>(fuse: &'a Fuse<'_>) -> impl Fn(&T) -> bool + 'a {
310             move |_| !fuse.panicked()
311         }
312 
313         self.base = {
314             let fuse = &self.fuse;
315             let iter = iter.into_iter().take_while(cool(fuse));
316             self.base.consume_iter(iter)
317         };
318         self
319     }
320 
complete(self) -> C::Result321     fn complete(self) -> C::Result {
322         self.base.complete()
323     }
324 
full(&self) -> bool325     fn full(&self) -> bool {
326         self.fuse.panicked() || self.base.full()
327     }
328 }
329 
330 struct PanicFuseReducer<'a, C> {
331     base: C,
332     _fuse: Fuse<'a>,
333 }
334 
335 impl<'a, T, C> Reducer<T> for PanicFuseReducer<'a, C>
336 where
337     C: Reducer<T>,
338 {
reduce(self, left: T, right: T) -> T339     fn reduce(self, left: T, right: T) -> T {
340         self.base.reduce(left, right)
341     }
342 }
343