que 0.4.5

A high performance channel with optional backpressure, interprocess capability, and a multiconsumer mode.
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
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

//! TODO: audit

pub mod consumer;
pub mod producer;

use crate::Channel;

const fn burst_amount<const N: usize>() -> usize {
    // Producer can write up to 1/4 of the buffer at a time
    const BURST_DENOM: usize = 4;

    let x = N / BURST_DENOM;

    if x == 0 {
        1
    } else {
        x
    }
}

#[cfg(test)]
mod tests {
    use bytemuck::AnyBitPattern;
    use consumer::Consumer;
    use producer::Producer;

    use super::*;
    use crate::test_utils::{new_spsc_buffer, Alloc};

    use std::{
        ptr::NonNull,
        sync::atomic::{AtomicU64, Ordering},
    };

    pub(crate) fn new_spsc_pair<T: AnyBitPattern, const N: usize>(
    ) -> (Alloc, Producer<T, N>, Consumer<T, N>) {
        let alloc = new_spsc_buffer::<T, N>();

        let producer =
            unsafe { Producer::initialize_in(alloc.ptr).unwrap() };
        let consumer = unsafe { Consumer::join(alloc.ptr).unwrap() };

        (alloc, producer, consumer)
    }

    #[test]
    fn test_push_pop_multiple() {
        let (_alloc, mut producer, mut consumer) =
            new_spsc_pair::<u64, 16>();

        producer.push(&69).unwrap();
        producer.push(&70).unwrap();
        assert_eq!(consumer.pop(), None);

        producer.sync();
        assert_eq!(consumer.pop(), Some(69));
        assert_eq!(consumer.pop(), Some(70));
    }

    #[test]
    fn test_push_pop_overrun() {
        let (_alloc, mut producer, mut consumer) =
            new_spsc_pair::<u64, 4>();

        assert!(producer.push(&69).is_ok());
        assert!(producer.push(&70).is_ok());
        assert!(producer.push(&71).is_ok());
        assert!(producer.push(&72).is_ok());
        assert!(producer.push(&73).is_err());

        assert_eq!(consumer.pop(), Some(69));
        assert_eq!(consumer.pop(), Some(70));
        assert_eq!(consumer.pop(), Some(71));
        assert_eq!(consumer.pop(), Some(72));

        // This should now succeed, along with next read
        assert!(producer.push(&73).is_ok());
        assert_eq!(consumer.pop(), Some(73));
    }

    #[test]
    fn test_restart_producer() {
        let alloc = new_spsc_buffer::<u64, 16>();
        let mut producer: Producer<u64, 16> =
            unsafe { Producer::initialize_in(alloc.ptr).unwrap() };
        let mut consumer: Consumer<u64, 16> =
            unsafe { Consumer::join(alloc.ptr).unwrap() };

        producer.push(&69).unwrap();
        producer.push(&70).unwrap();
        producer.sync();
        drop(producer);

        // Restart producer, last values should be kept
        let mut producer =
            unsafe { Producer::<u64, 16>::join(alloc.ptr).unwrap() };

        assert_eq!(consumer.pop(), Some(69));

        // No value published until sync
        assert_eq!(consumer.pop(), Some(70));

        // Push
        producer.push(&71).unwrap();
        assert_eq!(consumer.pop(), None);

        // Publish
        producer.sync();
        assert_eq!(consumer.pop(), Some(71));
    }

    #[test]
    fn test_detect_offline_consumer() {
        let alloc = new_spsc_buffer::<u64, 4>();
        let mut producer: Producer<u64, 4> =
            unsafe { Producer::initialize_in(alloc.ptr).unwrap() };
        assert!(!producer.consumer_heartbeat());

        let consumer: Consumer<u64, 4> =
            unsafe { Consumer::join(alloc.ptr).unwrap() };
        consumer.beat();
        assert!(producer.consumer_heartbeat());

        assert!(!producer.consumer_heartbeat());
    }

    #[test]
    fn test_synchronized_metadata() {
        struct SendPtr(NonNull<u8>);
        unsafe impl Send for SendPtr {}

        let alloc = new_spsc_buffer::<u64, 4>();
        let buffer = SendPtr(NonNull::new(alloc.ptr).unwrap());
        let producer: Producer<u64, 4> = unsafe {
            Producer::initialize_in(buffer.0.as_ptr()).unwrap()
        };

        // Start up thread to read metadata
        let read = std::thread::spawn(move || {
            let buffer = buffer;
            let consumer: Consumer<u64, 4> =
                unsafe { Consumer::join(buffer.0.as_ptr()).unwrap() };
            let metadata: &AtomicU64 = unsafe {
                &*consumer
                    .get_padding_ptr()
                    .cast()
                    .as_ptr()
            };
            loop {
                let value = metadata.load(Ordering::Acquire);
                if value != 0 {
                    return value;
                }
            }
        });

        // Set metadata (padding is 128-byte aligned)
        let metadata: u64 = 12345_u64;
        let padding_ptr: NonNull<[u8; 112]> =
            producer.get_padding_ptr();
        unsafe {
            (*padding_ptr.as_ptr().cast::<AtomicU64>())
                .store(metadata, Ordering::Release);
        }

        assert_eq!(read.join().unwrap(), metadata);
    }
}