84 lines
1.8 KiB
Rust
84 lines
1.8 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use std::cell::Cell;
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use std::ops::{Deref, DerefMut};
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#[derive(PartialEq)]
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struct DerefCounter<T> {
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count_imm: Cell<usize>,
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count_mut: usize,
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value: T
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}
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impl<T> DerefCounter<T> {
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fn new(value: T) -> DerefCounter<T> {
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DerefCounter {
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count_imm: Cell::new(0),
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count_mut: 0,
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value: value
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}
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}
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fn counts(&self) -> (usize, usize) {
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(self.count_imm.get(), self.count_mut)
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}
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}
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impl<T> Deref for DerefCounter<T> {
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type Target = T;
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fn deref(&self) -> &T {
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self.count_imm.set(self.count_imm.get() + 1);
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&self.value
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}
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}
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impl<T> DerefMut for DerefCounter<T> {
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fn deref_mut(&mut self) -> &mut T {
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self.count_mut += 1;
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&mut self.value
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}
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}
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#[derive(PartialEq, Debug)]
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struct Point {
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x: isize,
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y: isize
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}
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impl Point {
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fn get(&self) -> (isize, isize) {
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(self.x, self.y)
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}
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}
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pub fn main() {
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let mut p = DerefCounter::new(Point {x: 0, y: 0});
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let _ = p.x;
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assert_eq!(p.counts(), (1, 0));
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let _ = &p.x;
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assert_eq!(p.counts(), (2, 0));
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let _ = &mut p.y;
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assert_eq!(p.counts(), (2, 1));
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p.x += 3;
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assert_eq!(p.counts(), (2, 2));
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p.get();
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assert_eq!(p.counts(), (3, 2));
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// Check the final state.
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assert_eq!(*p, Point {x: 3, y: 0});
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}
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