62 lines
1.6 KiB
Rust
62 lines
1.6 KiB
Rust
// Copyright 2016 Mozilla
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
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// this file except in compliance with the License. You may obtain a copy of the
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// License at http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software distributed
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// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
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// CONDITIONS OF ANY KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations under the License.
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use std::cell::Cell;
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use std::rc::Rc;
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#[derive(Clone)]
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pub struct RcCounter {
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c: Rc<Cell<usize>>,
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}
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/// A simple shared counter.
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impl RcCounter {
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pub fn with_initial(value: usize) -> Self {
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RcCounter { c: Rc::new(Cell::new(value)) }
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}
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pub fn new() -> Self {
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RcCounter { c: Rc::new(Cell::new(0)) }
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}
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/// Return the next value in the sequence.
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///
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/// ```
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/// use mentat_core::counter::RcCounter;
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///
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/// let c = RcCounter::with_initial(3);
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/// assert_eq!(c.next(), 3);
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/// assert_eq!(c.next(), 4);
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/// let d = c.clone();
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/// assert_eq!(d.next(), 5);
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/// assert_eq!(c.next(), 6);
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/// ```
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pub fn next(&self) -> usize {
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let current = self.c.get();
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self.c.replace(current + 1)
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}
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}
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#[cfg(test)]
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mod tests {
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use super::RcCounter;
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#[test]
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fn test_rc_counter() {
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let c = RcCounter::new();
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assert_eq!(c.next(), 0);
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assert_eq!(c.next(), 1);
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let d = c.clone();
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assert_eq!(d.next(), 2);
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assert_eq!(c.next(), 3);
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}
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}
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