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87 lines
2.3 KiB
Rust
87 lines
2.3 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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use std::vec::Vec;
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struct DerefCounter<T> {
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count_imm: Cell<uint>,
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count_mut: uint,
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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) -> (uint, uint) {
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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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pub fn main() {
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let mut n = DerefCounter::new(0i);
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let mut v = DerefCounter::new(Vec::new());
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let _ = *n; // Immutable deref + copy a POD.
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assert_eq!(n.counts(), (1, 0));
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let _ = (&*n, &*v); // Immutable deref + borrow.
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assert_eq!(n.counts(), (2, 0)); assert_eq!(v.counts(), (1, 0));
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let _ = (&mut *n, &mut *v); // Mutable deref + mutable borrow.
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assert_eq!(n.counts(), (2, 1)); assert_eq!(v.counts(), (1, 1));
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let mut v2 = Vec::new();
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v2.push(1i);
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*n = 5; *v = v2; // Mutable deref + assignment.
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assert_eq!(n.counts(), (2, 2)); assert_eq!(v.counts(), (1, 2));
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*n -= 3; // Mutable deref + assignment with binary operation.
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assert_eq!(n.counts(), (2, 3));
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// Immutable deref used for calling a method taking &self. (The
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// typechecker is smarter now about doing this.)
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(*n).to_string();
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assert_eq!(n.counts(), (3, 3));
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// Mutable deref used for calling a method taking &mut self.
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(*v).push(2);
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assert_eq!(v.counts(), (1, 3));
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// Check the final states.
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assert_eq!(*n, 2);
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let expected: &[_] = &[1, 2];
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assert_eq!((*v).as_slice(), expected);
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}
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