parallel_worker 0.1.3

A parallel worker implementation in Rust. Allows to start tasks in parallel and receive the results blocking or non-blocking.
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

use std::{
    collections::VecDeque,
    sync::{Arc, Condvar, Mutex},
};

struct InnerTaskQueue<T> {
    tasks: Mutex<VecDeque<T>>,
    condvar: Condvar,
}

impl<T> InnerTaskQueue<T> {
    fn clear_queue(&self) -> usize {
        self.tasks.lock().unwrap().drain(..).len()
    }

    fn new() -> InnerTaskQueue<T> {
        InnerTaskQueue {
            tasks: Mutex::new(VecDeque::new()),
            condvar: Condvar::new(),
        }
    }

    fn push(&self, task: T) {
        self.tasks.lock().unwrap().push_back(task);
        self.condvar.notify_one();
    }

    fn extend(&self, new_tasks: impl IntoIterator<Item = T>) -> usize {
        let num_new = {
            let mut tasks = self.tasks.lock().unwrap();
            let len = tasks.len();
            tasks.extend(new_tasks);
            tasks.len() - len
        };
        match num_new {
            0 => (),
            1 => self.condvar.notify_one(),
            _ => self.condvar.notify_all(),
        }
        num_new
    }

    fn wait_for_task_and_then(&self, f: impl Fn()) -> T {
        let mut tasks = self.tasks.lock().unwrap();
        loop {
            match tasks.pop_front() {
                Some(task) => {
                    f();
                    return task;
                }
                None => tasks = self.condvar.wait(tasks).unwrap(),
            }
        }
    }

    fn len(&self) -> usize {
        self.tasks.lock().unwrap().len()
    }
}

pub struct TaskQueue<T> {
    inner: Arc<InnerTaskQueue<T>>,
}

impl<T> TaskQueue<T> {
    pub fn new() -> TaskQueue<T> {
        TaskQueue {
            inner: Arc::new(InnerTaskQueue::new()),
        }
    }

    pub fn clear_queue(&self) -> usize {
        self.inner.clear_queue()
    }

    pub fn push(&self, task: T) {
        self.inner.push(task);
    }

    pub fn extend(&self, new_tasks: impl IntoIterator<Item = T>) -> usize {
        self.inner.extend(new_tasks)
    }

    pub fn wait_for_task_and_then(&self, f: impl Fn()) -> T {
        self.inner.wait_for_task_and_then(f)
    }

    pub fn len(&self) -> usize {
        self.inner.len()
    }
}

impl<T> Clone for TaskQueue<T> {
    fn clone(&self) -> TaskQueue<T> {
        TaskQueue {
            inner: self.inner.clone(),
        }
    }
}

#[cfg(test)]
mod tests {
    use std::{thread::sleep, time::Duration};

    use super::*;

    #[test]
    fn test_task_queue() {
        let task_queue = TaskQueue::new();
        assert_eq!(task_queue.inner.tasks.lock().unwrap().len(), 0);
        task_queue.push(1);
        assert_eq!(task_queue.inner.tasks.lock().unwrap().len(), 1);
        task_queue.push(2);
        assert_eq!(task_queue.inner.tasks.lock().unwrap().len(), 2);
        assert_eq!(task_queue.wait_for_task_and_then(|| ()), 1);
        assert_eq!(task_queue.inner.tasks.lock().unwrap().len(), 1);
        assert_eq!(task_queue.wait_for_task_and_then(|| ()), 2);
        assert_eq!(task_queue.inner.tasks.lock().unwrap().len(), 0);

        let task_queue_clone = task_queue.clone();
        let t = std::thread::spawn(move || task_queue_clone.wait_for_task_and_then(|| ()));

        sleep(Duration::from_millis(500));
        assert!(!t.is_finished());

        task_queue.push(1);
        assert!(t.join().is_ok());

        let threads = (0..10)
            .map(|_| {
                let task_queue_clone = task_queue.clone();
                std::thread::spawn(move || {
                    task_queue_clone.wait_for_task_and_then(|| ());
                })
            })
            .collect::<Vec<_>>();

        assert!(threads.iter().all(|t| !t.is_finished()));
        task_queue.extend(0..1);
        assert!(threads.iter().any(|t| !t.is_finished()));
        task_queue.extend(0..0);
        assert!(threads.iter().any(|t| !t.is_finished()));
        task_queue.extend(0..8);
        assert!(threads.iter().any(|t| !t.is_finished()));
        task_queue.extend(0..1);

        assert!(threads.into_iter().all(|t| t.join().is_ok()));
    }
}