omango 0.2.6

Concurrency collections
Documentation 
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

// Copyright (c) 2024 Trung Tran <tqtrungse@gmail.com>
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

use std::{
    cell::UnsafeCell,
    mem::MaybeUninit,
    sync::atomic::{AtomicU32, Ordering},
};

/// Element for bounded queue.
pub(crate) struct ElemArr<T> {
    lap: AtomicU32,
    msg: UnsafeCell<MaybeUninit<T>>,
}

impl<T> Default for ElemArr<T> {
    #[inline(always)]
    fn default() -> Self {
        Self {
            lap: AtomicU32::new(0),
            msg: UnsafeCell::new(MaybeUninit::uninit()),
        }
    }
}

impl<T> ElemArr<T> {
    #[inline(always)]
    pub(crate) fn load_lap(&self) -> u32 {
        self.lap.load(Ordering::Acquire)
    }

    #[inline(always)]
    pub(crate) fn write(&self, lap: u32, msg: T) {
        unsafe { 
            self.msg.get().write(MaybeUninit::new(msg)); 
        }
        // Make the element available for reading.
        self.lap.store(lap, Ordering::Release);
    }

    #[inline(always)]
    pub(crate) fn read(&self, lap: u32) -> T {
        // We own the element, do non-atomic read and remove.
        let msg: T;
        unsafe { 
            msg = self.msg.get().read().assume_init(); 
        }

        // Make the element available for writing.
        self.lap.store(lap, Ordering::Release);
        msg
    }

    #[inline(always)]
    pub(crate) fn atom_lap(&self) -> *const AtomicU32 {
        &self.lap
    }
}

impl<T> Drop for ElemArr<T> {
    /// Because [`MaybeUninit`] will not drop contained data, we need to manually drop.
    /// 
    /// The concurrent queues don't provide `drop` function, [`ElemArr`] is dropped
    /// if and only if the queues are out of scope (aka automatically dropped).
    /// 
    /// It is not thread safe, so it is your responsibility to make sure that there are 
    /// no any operations in the queues at the dropped time. 
    /// 
    /// [`MaybeUninit`]: MaybeUninit
    /// [`ElemArr`]: elem::ElemArr
    fn drop(&mut self) {
        unsafe {
            let raw_data = self.msg.get_mut().as_mut_ptr();
            if !raw_data.is_null() {
                std::ptr::drop_in_place(raw_data);
            }
        }
    }
}