sf/
ctx.rs

1use super::defs::MAX_SEQ;
2use super::utils::ms_since_epoch;
3use super::Id;
4use std::sync::{Arc, Mutex};
5
6struct State {
7    seq: u16, // sequence in milliseconds
8    ts: u64,  // timestamp in milliseconds
9}
10
11#[derive(Clone)]
12pub struct Context {
13    epoch: u128,    // time offset from start of unix time in milliseconds
14    worker_id: u16, // 10 bits worker id
15    state: Arc<Mutex<State>>, // shared state
16}
17
18impl Context {
19    pub fn new(epoch: u128, worker_id: u16) -> Result<Context, String> {
20        let now = ms_since_epoch()?;
21
22        if now < epoch {
23            return Err(format!("bad epoch {}", epoch));
24        }
25
26        // Make sure timestamp of Id is now 0 and so Id must be not nil.
27        if now == epoch {
28            loop {
29                if ms_since_epoch()? != epoch {
30                    break;
31                }
32            }
33        }
34
35        Ok(Context {
36            epoch,
37            worker_id,
38            state: Arc::new(Mutex::new(State { seq: 0, ts: 0 })),
39        })
40    }
41
42    pub fn next(&self) -> Result<Id, String> {
43        let mut state = self.state.lock().unwrap();
44        let ts = self.get_ts()?;
45
46        if ts == state.ts {
47            (*state).seq += 1;
48        } else {
49            (*state).seq = 0;
50            (*state).ts = ts;
51        };
52
53        let seq = state.seq;
54
55        if seq >= MAX_SEQ {
56            return Err(format!("bad seq {}", seq));
57        }
58
59        Ok(Id::new(ts, self.worker_id, seq))
60    }
61
62    pub fn next_id(&self) -> Id {
63        loop {
64            if let Ok(id) = self.next() {
65                return id;
66            }
67        }
68    }
69
70    fn get_ts(&self) -> Result<u64, String> {
71        let now = ms_since_epoch()?;
72        Ok((now - self.epoch) as u64)
73    }
74}
75
76#[cfg(test)]
77mod tests {
78    use super::Context;
79
80    #[test]
81    fn test_create_context_fail() {
82        let context = Context::new(!0, 0);
83
84        assert!(context.is_err());
85    }
86
87    #[test]
88    fn test_create_context_success() {
89        let context = Context::new(1_234_567_891_011, 0);
90
91        assert!(context.is_ok());
92
93        let context = Context::new(0, 0);
94
95        assert!(context.is_ok());
96    }
97
98    #[test]
99    fn test_generate_id_success() {
100        let context = Context::new(1_548_067_209_841, 0).unwrap();
101        let id = context.next_id();
102
103        assert_ne!(id, 0.into());
104    }
105}
sf/ctx.rs

sf/
ctx.rs
