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

use std::cell::RefCell;
use std::collections::HashMap;
use std::sync::{Arc, RwLock};

#[macro_use]
extern crate lazy_static;

lazy_static! {
    static ref GIDMap: Arc<RwLock<IDMap>> = Arc::new(RwLock::new(IDMap::new()));
}

struct IDMap(HashMap<String, u64>);

impl IDMap {
    pub fn new() -> IDMap {
        IDMap(HashMap::new())
    }

    pub fn current(&mut self, key: &str) -> u64 {
        if let Some(x) = self.0.get_mut(key) {
            *x
        } else {
            let v = 0;
            self.0.insert(key.to_string(), v);
            v
        }
    }

    pub fn next(&mut self, key: &str) -> u64 {
        let next = self.current(key) + 1;
        self.0.insert(key.to_string(), next);
        next
    }
}

#[cfg(test)]
mod tests {
    #[test]
    fn it_works() {
        use super::GIDMap;
        use std::thread;

        let r1 = GIDMap.clone();
        let r2 = GIDMap.clone();
        let r3 = GIDMap.clone();
        let r4 = GIDMap.clone();
        let r5 = GIDMap.clone();
        let th1 = thread::spawn(move || {
            println!("{}", r1.write().unwrap().current("hello"));
        });
        let th2 = thread::spawn(move || {
            println!("{}", r2.write().unwrap().current("hello"));
        });
        th1.join();
        th2.join();

        let th3 = thread::spawn(move || {
            println!("{}", r3.write().unwrap().next("hello"));
        });
        let th4 = thread::spawn(move || {
            println!("{}", r4.write().unwrap().next("hello"));
        });
        let th5 = thread::spawn(move || {
            println!("{}", r5.write().unwrap().current("hello"));
        });
        th3.join();
        th4.join();
        th5.join();
    }
}