1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
use std::ptr::NonNull;
#[derive(Debug)]
pub struct DoublyLinkedList<T> {
head: Option<NonNull<Node<T>>>,
tail: Option<NonNull<Node<T>>>,
elements: usize,
}
#[derive(Debug)]
pub struct Node<T> {
pub elem: T,
pub next: Option<NonNull<Node<T>>>,
pub prev: Option<NonNull<Node<T>>>,
}
#[cfg(feature = "matecito")]
unsafe impl<T> Send for DoublyLinkedList<T> {}
#[cfg(feature = "matecito")]
unsafe impl<T> Sync for DoublyLinkedList<T> {}
impl<T> DoublyLinkedList<T> {
pub fn new() -> Self {
Self {
head: None,
tail: None,
elements: 0,
}
}
pub fn delete(&mut self, non_null_node: NonNull<Node<T>>) -> Option<T> {
let mut non_null_node = non_null_node;
let node = unsafe { non_null_node.as_mut() };
let prev_node = match node.prev {
None => None,
Some(mut pnode) => NonNull::new(unsafe { pnode.as_mut() }),
};
let next_node = match node.next {
None => None,
Some(mut pnode) => NonNull::new(unsafe { pnode.as_mut() }),
};
match next_node {
None => {
self.tail = prev_node;
}
Some(mut nnode_opt) => {
let next_node = unsafe { nnode_opt.as_mut() };
next_node.prev = prev_node;
}
}
match prev_node {
None => {
self.head = next_node;
}
Some(nnode_opt) => {
let prev_node = unsafe { nnode_opt.as_ptr().as_mut().unwrap() };
prev_node.next = next_node;
}
}
let node = unsafe { Box::from_raw(node) };
self.elements -= 1;
Some(node.elem)
}
pub fn push_back(&mut self, elem: T) -> NonNull<Node<T>> {
let node = Node {
elem,
next: None,
prev: None,
};
let boxed_node = Box::into_raw(Box::new(node));
let node = NonNull::new(boxed_node);
let raw_old_head = self.head;
if self.head.is_none() {
self.head = node;
self.tail = node;
self.elements += 1;
return self.head.unwrap();
}
self.head = node;
match raw_old_head {
None => (),
Some(mut non_null_node) => unsafe {
non_null_node.as_mut().prev = node;
self.head.unwrap().as_mut().next = raw_old_head;
},
};
self.elements += 1;
return self.head.unwrap();
}
pub fn pop_front(&mut self) -> Option<T> {
if self.tail.is_none() {
return None;
}
let old_tail = self.tail;
self.tail = match old_tail {
None => return None,
Some(mut non_null_node) => unsafe { non_null_node.as_mut().prev },
};
if self.tail.is_none() {
self.head = None;
}
let old_tail = unsafe { Box::from_raw(old_tail.unwrap().as_ptr()) };
self.elements -= 1;
Some(old_tail.elem)
}
#[allow(dead_code)]
pub fn pop_back(&mut self) -> Option<T> {
if self.head.is_none() {
return None;
}
let old_head = self.head;
self.head = match old_head {
None => return None,
Some(mut non_null_node) => unsafe { non_null_node.as_mut().next },
};
if self.head.is_none() {
self.tail = None;
}
let result = unsafe { Box::from_raw(old_head.unwrap().as_ptr()) };
self.elements -= 1;
Some(result.elem)
}
#[allow(dead_code)]
pub fn peek_front(&self) -> Option<&NonNull<Node<T>>> {
if self.tail.is_none() {
return None;
}
self.tail.as_ref()
}
pub fn is_empty(&self) -> bool {
self.elements == 0
}
pub fn num_elements(&self) -> usize {
self.elements
}
}
impl<T> Drop for DoublyLinkedList<T> {
fn drop(&mut self) {
while !self.is_empty() {
self.pop_front();
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn push_front_and_pop_front() {
let mut dll = DoublyLinkedList::new();
assert_eq!(None, dll.pop_front());
let range = std::ops::Range {
start: 10,
end: 100,
};
for num in 0..range.len() {
dll.push_back(num);
}
for num in 0..range.len() {
assert_eq!(Some(num), dll.pop_front());
}
assert_eq!(None, dll.pop_front());
}
#[test]
fn push_front_and_pop_back() {
let mut dll = DoublyLinkedList::new();
assert_eq!(None, dll.pop_back());
let range = std::ops::Range {
start: 10,
end: 100,
};
for num in range.clone() {
dll.push_back(num);
}
for num in range.clone().rev().clone() {
assert_eq!(Some(num), dll.pop_back());
}
assert_eq!(None, dll.pop_back());
}
#[test]
fn populate_and_delete() {
let mut dll = DoublyLinkedList::new();
let range = std::ops::Range { start: 0, end: 3 };
let mut elements = vec![];
for num in range.clone() {
let node = dll.push_back(num as i32);
elements.push(node);
}
dll.delete(elements[1]);
dll.delete(elements[0]);
assert_eq!(Some(2), dll.pop_front());
assert!(dll.is_empty());
assert_eq!(None, dll.pop_front());
}
#[test]
fn num_elements() {
let mut dll = DoublyLinkedList::new();
let range = std::ops::Range { start: 0, end: 3 };
let mut num_elements = range.len();
let mut elements = vec![];
for num in range.clone() {
let node = dll.push_back(num as i32);
elements.push(node);
}
for num in range.clone() {
dll.delete(elements[num]);
num_elements -= 1;
assert_eq!(num_elements, dll.num_elements());
}
let mut num_elements = range.len();
for num in range.clone() {
dll.push_back(num as i32);
}
for _ in range.clone() {
dll.pop_front();
num_elements -= 1;
assert_eq!(num_elements, dll.num_elements());
}
let mut num_elements = range.len();
for num in range.clone() {
dll.push_back(num as i32);
}
for _ in range.clone() {
dll.pop_back();
num_elements -= 1;
assert_eq!(num_elements, dll.num_elements());
}
}
#[test]
fn edge_case_push_after_emptied_delete_and_empty_again() {
let mut dll = DoublyLinkedList::new();
let n1 = dll.push_back(1);
let n2 = dll.push_back(2);
let n3 = dll.push_back(3);
dll.delete(n1);
assert_eq!(2, dll.num_elements());
dll.delete(n2);
assert_eq!(1, dll.num_elements());
dll.delete(n3);
assert_eq!(0, dll.num_elements());
assert!(dll.is_empty());
let n1 = dll.push_back(1);
assert_eq!(1, dll.num_elements());
dll.delete(n1);
assert_eq!(0, dll.num_elements());
assert!(dll.is_empty());
}
#[test]
fn edge_case_push_after_emptied_pop_front_and_empty_again() {
let mut dll = DoublyLinkedList::new();
dll.push_back(1);
dll.push_back(2);
dll.push_back(3);
dll.pop_front();
assert_eq!(2, dll.num_elements());
dll.pop_front();
assert_eq!(1, dll.num_elements());
dll.pop_front();
assert_eq!(0, dll.num_elements());
assert!(dll.is_empty());
dll.push_back(1);
assert_eq!(1, dll.num_elements());
dll.pop_front();
assert_eq!(0, dll.num_elements());
assert!(dll.is_empty());
}
#[test]
fn edge_case_push_after_emptied_pop_back_and_empty_again() {
let mut dll = DoublyLinkedList::new();
dll.push_back(1);
dll.push_back(2);
dll.push_back(3);
dll.pop_back();
assert_eq!(2, dll.num_elements());
dll.pop_back();
assert_eq!(1, dll.num_elements());
dll.pop_back();
assert_eq!(0, dll.num_elements());
assert!(dll.is_empty());
dll.push_back(1);
assert_eq!(1, dll.num_elements());
dll.pop_back();
assert_eq!(0, dll.num_elements());
assert_eq!(None, dll.pop_back());
assert!(dll.is_empty());
}
}