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

use std::alloc::{dealloc, Layout, realloc};
use std::ptr;
use crate::utils::{closest_pow2, rotate_inc};

pub struct Queue<T>
where
    T: Copy + Sized,
{
    capacity: usize,
    len: usize,
    layout: Layout,
    data: *mut T,
    front: usize,
    end: usize,
}
impl<T> Queue<T>
where
    T: Copy + Sized,
{
    pub fn new_pow2_sized(capacity: usize) -> Self {
        let capacity = closest_pow2(capacity);
        let layout = Layout::array::<T>(capacity).expect("Failed to create layout");
        let data = unsafe { std::alloc::alloc(layout) as *mut T };
        if data.is_null() {
            panic!("Failed to allocate memory");
        }

        Queue {
            capacity,
            layout,
            data,
            len: 0,
            front: 0,
            end: 0,
        }
    }

    #[inline(always)]
    pub fn is_empty(&self) -> bool {
        self.len == 0
    }

    pub fn extend_pow2_sized(&mut self, capacity_pow: usize) {
        let new_capacity = closest_pow2(capacity_pow);
        if new_capacity <= self.capacity {
            panic!("New capacity is less than or equal to current capacity");
        }

        let new_layout = Layout::array::<T>(new_capacity).expect("Failed to create layout");
        // Data can only wrap if data actually exists. We need to do len check.
        if self.front >= self.end && self.len > 0{
            let new_data = unsafe { std::alloc::alloc(new_layout) as *mut T };
            if new_data.is_null() {
                panic!("Failed to allocate memory");
            }
            let from_front_to_array_end_len = self.capacity() - self.front;
            let from_start_to_end_len = self.front;
            unsafe { ptr::copy_nonoverlapping(self.data.add(self.front), new_data, from_front_to_array_end_len) }; // After Front
            unsafe { ptr::copy_nonoverlapping(self.data, new_data.add(from_front_to_array_end_len), from_start_to_end_len) }; // Before Front

            unsafe { dealloc(self.data as *mut u8, self.layout) };
            self.capacity = new_capacity;
            self.data = new_data;
            self.front = 0;
            self.end = from_front_to_array_end_len + from_start_to_end_len;
            return;
        }

        unsafe {
            self.data = realloc(self.data as *mut u8, new_layout, new_layout.size()) as *mut T;
            if self.data.is_null() {
                panic!("Failed to reallocate memory");
            }
            self.capacity = new_capacity;
        }

    }
    #[inline(always)]
    pub fn extend_pow2_sized_by(&mut self, capacity_pow: usize) {
        if self.capacity < self.capacity + capacity_pow {
            return;
        }
        let new_capacity = closest_pow2(self.capacity + capacity_pow);
        self.extend_pow2_sized(new_capacity)
    }
    #[inline(always)]
    pub fn capacity(&self) -> usize {
        self.capacity
    }
    #[inline(always)]
    pub fn len(&self) -> usize {
        self.len
    }

    #[inline(always)]
    pub fn push(&mut self, value: T) {
        if self.len == self.capacity {
            panic!("Queue is full");
        }
        unsafe {
            self.data.add(self.end).write(value);
            self.len += 1;
            self.end = rotate_inc(self.end, self.capacity - 1);
        }
    }
    #[inline(always)]
    pub fn front(&self) -> Option<&T> {
        if self.len == 0 {
            return None;
        }
        unsafe {
            Some(self.data.add(self.front).as_ref().unwrap())
        }
    }
    #[inline(always)]
    pub fn front_mut(&mut self) -> Option<&mut T> {
        if self.len == 0 {
            return None;
        }
        unsafe {
            Some(self.data.add(self.front).as_mut().unwrap())
        }
    }
    #[inline(always)]
    pub fn dequeue(&mut self) -> Option<T> {
        if self.len == 0 {
            return None;
        }
        unsafe {
            let result = Some(self.data.add(self.front).read());
            self.len -= 1;
            self.front = rotate_inc(self.front, self.capacity - 1);
            result
        }
    }
}

impl<T> Drop for Queue<T>
where
    T: Copy + Sized,
{
    fn drop(&mut self) {
        unsafe {
            dealloc(self.data as *mut u8, self.layout);
        }
    }
}