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    zerompk::ToMessagePack,
29    zerompk::FromMessagePack,
30)]
31pub struct Lsn(u64);
32
33impl Lsn {
34    pub const ZERO: Lsn = Lsn(0);
35
36    pub const fn new(value: u64) -> Self {
37        Self(value)
38    }
39
40    pub const fn as_u64(self) -> u64 {
41        self.0
42    }
43
44    /// Returns the next LSN (self + 1).
45    pub const fn next(self) -> Self {
46        Self(self.0 + 1)
47    }
48
49    /// Returns true if this LSN is ahead of `other`.
50    pub const fn is_ahead_of(self, other: Self) -> bool {
51        self.0 > other.0
52    }
53}
54
55impl fmt::Display for Lsn {
56    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
57        write!(f, "lsn:{}", self.0)
58    }
59}
60
61#[cfg(test)]
62mod tests {
63    use super::*;
64
65    #[test]
66    fn lsn_ordering() {
67        let a = Lsn::new(1);
68        let b = Lsn::new(2);
69        assert!(a < b);
70        assert_eq!(a.next(), b);
71        assert!(b.is_ahead_of(a));
72        assert!(!a.is_ahead_of(b));
73    }
74
75    #[test]
76    fn lsn_display() {
77        assert_eq!(Lsn::new(42).to_string(), "lsn:42");
78    }
79
80    #[test]
81    fn lsn_zero() {
82        assert_eq!(Lsn::ZERO.as_u64(), 0);
83    }
84}
nodedb_types/lsn.rs

nodedb_types/
lsn.rs
