nodedb_types/
lsn.rs

1//! Log Sequence Number — monotonically increasing identifier for WAL records.
2//!
3//! LSNs are the universal ordering primitive across both Origin and Lite.
4//! On Origin: WAL record ordering. On Lite: sync watermark tracking.
5
6use std::fmt;
7
8use serde::{Deserialize, Serialize};
9
10/// Log Sequence Number.
11///
12/// On Origin: anchors every write, snapshot, and consistency check.
13/// On Lite: tracks sync progress (last-seen LSN from Origin).
14#[derive(
15    Debug,
16    Clone,
17    Copy,
18    PartialEq,
19    Eq,
20    PartialOrd,
21    Ord,
22    Hash,
23    Serialize,
24    Deserialize,
25    rkyv::Archive,
26    rkyv::Serialize,
27    rkyv::Deserialize,
28)]
29pub struct Lsn(u64);
30
31impl Lsn {
32    pub const ZERO: Lsn = Lsn(0);
33
34    pub const fn new(value: u64) -> Self {
35        Self(value)
36    }
37
38    pub const fn as_u64(self) -> u64 {
39        self.0
40    }
41
42    /// Returns the next LSN (self + 1).
43    pub const fn next(self) -> Self {
44        Self(self.0 + 1)
45    }
46
47    /// Returns true if this LSN is ahead of `other`.
48    pub const fn is_ahead_of(self, other: Self) -> bool {
49        self.0 > other.0
50    }
51}
52
53impl fmt::Display for Lsn {
54    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
55        write!(f, "lsn:{}", self.0)
56    }
57}
58
59#[cfg(test)]
60mod tests {
61    use super::*;
62
63    #[test]
64    fn lsn_ordering() {
65        let a = Lsn::new(1);
66        let b = Lsn::new(2);
67        assert!(a < b);
68        assert_eq!(a.next(), b);
69        assert!(b.is_ahead_of(a));
70        assert!(!a.is_ahead_of(b));
71    }
72
73    #[test]
74    fn lsn_display() {
75        assert_eq!(Lsn::new(42).to_string(), "lsn:42");
76    }
77
78    #[test]
79    fn lsn_zero() {
80        assert_eq!(Lsn::ZERO.as_u64(), 0);
81    }
82}
nodedb_types/lsn.rs

nodedb_types/
lsn.rs
