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

use std::alloc::{Layout, realloc};
use std::ops::{Index, IndexMut};
use std::ptr;

pub struct Stack<T> {
    capacity: usize,
    len: usize,
    layout: Layout,
    data: *mut T,
    top: *mut T,
    end: *mut T,

}

impl<T> Stack<T> {
    #[inline(always)]
    pub fn capacity(&self) -> usize {
        return self.capacity;
    }
    #[inline(always)]
    pub fn len(&self) -> usize {
        return self.len;
    }
    pub fn new(capacity: usize) -> Self {
        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");
        }

        return Stack {
            capacity,
            layout,
            data,
            len: 0,
            top: unsafe{data.offset(-1)},
            end: unsafe { data.offset(capacity as isize) },
        };
    }

    pub fn extend(&mut self, new_capacity: usize) {
        let new_layout = Layout::array::<T>(new_capacity).expect("Failed to create layout");
        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.end = self.data.add(new_capacity);
            self.top = self.data.offset((self.len as isize) - 1);
        }
        self.capacity = new_capacity;
        self.layout = new_layout;
    }
    #[inline(always)]
    pub fn extend_by(&mut self, additional_capacity: usize) {
        self.extend(self.capacity + additional_capacity);
    }
    #[inline(always)]
    pub fn top(&self) -> Option<&T> {
        if self.len == 0 {
            return None;
        }
        unsafe {
            Some(self.top.as_ref().unwrap())
        }
    }
    #[inline(always)]
    pub fn top_mut(&mut self) -> Option<&mut T> {
        if self.len == 0 {
            return None;
        }
        unsafe {
            Some(self.top.as_mut().unwrap())
        }
    }
    // #[inline(always)]
    pub fn push(&mut self, value: T) {
        let new_top = unsafe{self.top.offset(1)};
        if new_top == self.end {
            panic!("Stack over capacity!");
        }

        self.top = new_top;
        unsafe {self.top.write(value)};
        self.len += 1;
    }
    #[inline(always)]
    pub fn pop(&mut self) -> Option<T> {
        if self.len == 0 {
            return None;
        }

        unsafe {
            let result = Some(ptr::read(self.top));
            self.top = self.top.offset(-1);
            self.len -= 1;
            result
        }
    }
}

impl<T> Index<isize> for Stack<T> {
    type Output = T;
    #[inline(always)]
    fn index(&self, index: isize) -> &Self::Output {
        if index > 0{
            panic!("Index out of bounds");
        }

        if index <= self.len as isize * -1{
            panic!("Index out of bounds");
        }

        let indexed_data = unsafe{self.top.offset(index)};
        unsafe {indexed_data.as_ref().unwrap()}
    }
}

impl<T> IndexMut<isize> for Stack<T>{
    #[inline(always)]
    fn index_mut(&mut self, index: isize) -> &mut Self::Output {
        if index > 0{
            panic!("Index out of bounds");
        }

        if index < self.len as isize * -1{
            panic!("Index out of bounds");
        }

        let indexed_data = unsafe{self.top.offset(index)};
        unsafe {indexed_data.as_mut().unwrap()}
    }
}

impl<T> Drop for Stack<T> {
    fn drop(&mut self) {
        unsafe {
            std::alloc::dealloc(self.data as *mut u8, self.layout);
        }
    }
}