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// Copyright 2018 The Rust Project Developers. See the COPYRIGHT | ||
// file at the top-level directory of this distribution and at | ||
// http://rust-lang.org/COPYRIGHT. | ||
// | ||
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
// option. This file may not be copied, modified, or distributed | ||
// except according to those terms. | ||
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//! A singly-linked list. | ||
//! | ||
//! Using this data structure only makes sense under very specific | ||
//! circumstances: | ||
//! | ||
//! - If you have a list that rarely stores more than one element, then this | ||
//! data-structure can store the element without allocating and only uses as | ||
//! much space as a `Option<(T, usize)>`. If T can double as the `Option` | ||
//! discriminant, it will even only be as large as `T, usize`. | ||
//! | ||
//! If you expect to store more than 1 element in the common case, steer clear | ||
//! and use a `Vec<T>`, `Box<[T]>`, or a `SmallVec<T>`. | ||
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use std::mem; | ||
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#[derive(Clone, Hash, Debug, PartialEq)] | ||
pub struct TinyList<T: PartialEq> { | ||
head: Option<Element<T>> | ||
} | ||
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impl<T: PartialEq> TinyList<T> { | ||
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#[inline] | ||
pub fn new() -> TinyList<T> { | ||
TinyList { | ||
head: None | ||
} | ||
} | ||
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#[inline] | ||
pub fn new_single(data: T) -> TinyList<T> { | ||
TinyList { | ||
head: Some(Element { | ||
data, | ||
next: None, | ||
}) | ||
} | ||
} | ||
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#[inline] | ||
pub fn insert(&mut self, data: T) { | ||
let current_head = mem::replace(&mut self.head, None); | ||
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if let Some(current_head) = current_head { | ||
let current_head = Box::new(current_head); | ||
self.head = Some(Element { | ||
data, | ||
next: Some(current_head) | ||
}); | ||
} else { | ||
self.head = Some(Element { | ||
data, | ||
next: None, | ||
}) | ||
} | ||
} | ||
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#[inline] | ||
pub fn remove(&mut self, data: &T) -> bool { | ||
let remove_head = if let Some(ref mut head) = self.head { | ||
if head.data == *data { | ||
Some(mem::replace(&mut head.next, None)) | ||
} else { | ||
None | ||
} | ||
} else { | ||
return false | ||
}; | ||
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if let Some(remove_head) = remove_head { | ||
if let Some(next) = remove_head { | ||
self.head = Some(*next); | ||
} else { | ||
self.head = None; | ||
} | ||
return true | ||
} | ||
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self.head.as_mut().unwrap().remove_next(data) | ||
} | ||
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#[inline] | ||
pub fn contains(&self, data: &T) -> bool { | ||
if let Some(ref head) = self.head { | ||
head.contains(data) | ||
} else { | ||
false | ||
} | ||
} | ||
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#[inline] | ||
pub fn len(&self) -> usize { | ||
if let Some(ref head) = self.head { | ||
head.len() | ||
} else { | ||
0 | ||
} | ||
} | ||
} | ||
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#[derive(Clone, Hash, Debug, PartialEq)] | ||
struct Element<T: PartialEq> { | ||
data: T, | ||
next: Option<Box<Element<T>>>, | ||
} | ||
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impl<T: PartialEq> Element<T> { | ||
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fn remove_next(&mut self, data: &T) -> bool { | ||
let new_next = if let Some(ref mut next) = self.next { | ||
if next.data != *data { | ||
return next.remove_next(data) | ||
} else { | ||
mem::replace(&mut next.next, None) | ||
} | ||
} else { | ||
return false | ||
}; | ||
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self.next = new_next; | ||
return true | ||
} | ||
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fn len(&self) -> usize { | ||
if let Some(ref next) = self.next { | ||
1 + next.len() | ||
} else { | ||
1 | ||
} | ||
} | ||
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fn contains(&self, data: &T) -> bool { | ||
if self.data == *data { | ||
return true | ||
} | ||
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if let Some(ref next) = self.next { | ||
next.contains(data) | ||
} else { | ||
false | ||
} | ||
} | ||
} | ||
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#[cfg(test)] | ||
mod test { | ||
use super::*; | ||
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#[test] | ||
fn test_contains_and_insert() { | ||
fn do_insert(i : u32) -> bool { | ||
i % 2 == 0 | ||
} | ||
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let mut list = TinyList::new(); | ||
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for i in 0 .. 10 { | ||
for j in 0 .. i { | ||
if do_insert(j) { | ||
assert!(list.contains(&j)); | ||
} else { | ||
assert!(!list.contains(&j)); | ||
} | ||
} | ||
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assert!(!list.contains(i)); | ||
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if do_insert(i) { | ||
list.insert(i); | ||
assert!(list.contains(&i)); | ||
} | ||
} | ||
} | ||
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#[test] | ||
fn test_remove_first() { | ||
let mut list = TinyList::new(); | ||
list.insert(1); | ||
list.insert(2); | ||
list.insert(3); | ||
list.insert(4); | ||
assert_eq!(list.len(), 4); | ||
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assert!(list.remove(&4)); | ||
assert!(!list.contains(&4)); | ||
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assert_eq!(list.len(), 3); | ||
assert!(list.contains(&1)); | ||
assert!(list.contains(&2)); | ||
assert!(list.contains(&3)); | ||
} | ||
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#[test] | ||
fn test_remove_last() { | ||
let mut list = TinyList::new(); | ||
list.insert(1); | ||
list.insert(2); | ||
list.insert(3); | ||
list.insert(4); | ||
assert_eq!(list.len(), 4); | ||
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assert!(list.remove(&1)); | ||
assert!(!list.contains(&1)); | ||
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assert_eq!(list.len(), 3); | ||
assert!(list.contains(&2)); | ||
assert!(list.contains(&3)); | ||
assert!(list.contains(&4)); | ||
} | ||
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#[test] | ||
fn test_remove_middle() { | ||
let mut list = TinyList::new(); | ||
list.insert(1); | ||
list.insert(2); | ||
list.insert(3); | ||
list.insert(4); | ||
assert_eq!(list.len(), 4); | ||
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assert!(list.remove(&2)); | ||
assert!(!list.contains(&2)); | ||
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assert_eq!(list.len(), 3); | ||
assert!(list.contains(&1)); | ||
assert!(list.contains(&3)); | ||
assert!(list.contains(&4)); | ||
} | ||
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#[test] | ||
fn test_remove_single() { | ||
let mut list = TinyList::new(); | ||
list.insert(1); | ||
assert_eq!(list.len(), 1); | ||
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assert!(list.remove(&1)); | ||
assert!(!list.contains(&1)); | ||
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assert_eq!(list.len(), 0); | ||
} | ||
} |