Struct Lsn 

pub struct Lsn(/* private fields */);

Log sequence number.

Monotonically increasing within a single WAL generation; reset to zero across checkpoints (the salt rotation disambiguates). The sentinel value Lsn::ZERO represents “no LSN” — returned by crate::pager::Pager::commit for an empty transaction and by crate::pager::Pager::reader_snapshot for in-memory pagers that have no WAL.

Lsn is a #[repr(transparent)] newtype over u64 so the type-system rejects implicit confusion with page counts, byte offsets, or page ids (Power-of-Ten Rule 5). The serde encoding is #[serde(transparent)] — an Lsn round-trips byte-identically to the bare u64 it wraps, which preserves wire compatibility with any future on-disk record that names it directly.

Lsn deliberately does NOT implement Add<u64> / AddAssign<u64> or any other arithmetic trait. Step it through the explicit Lsn::checked_next / Lsn::prev_saturating helpers so every mutation is auditable.

Implementations

impl Lsn

pub const ZERO: Self

The sentinel “no LSN” value. Returned by crate::pager::Pager::commit when the transaction was empty and by crate::pager::Pager::reader_snapshot on in-memory pagers (no WAL exists).

pub const ONE: Self

The LSN handed out for the first frame of a fresh WAL generation.

pub const fn new(raw: u64) -> Self

Construct an Lsn from a raw u64. The underlying u64 has no invariants — any value (including 0) is valid — so this is a total function.

pub const fn get(self) -> u64

The raw u64 LSN value. Use this only when crossing into hand-rolled byte serialization (see crate::wal::frame::FrameHeader::lsn) or when emitting diagnostics; arithmetic should go through the explicit step helpers below.

pub fn checked_next(self) -> Result<Self>

Monotonic step: return the next LSN, or Error::InvalidArgument on u64 overflow.

Errors

Returns Error::InvalidArgument when the underlying counter would wrap past u64::MAX. At 10⁶ commits/sec this is ~584 000 years; the check is defensive (Power-of-Ten Rule 7) and extremely cheap.

pub const fn prev_saturating(self) -> Self

Predecessor LSN, saturating at Lsn::ZERO.

Used by crate::pager::Pager::commit / reader_snapshot to report the LSN of the last committed frame as next_lsn - 1, with the special case next_lsn == ZERO mapping back to ZERO rather than wrapping.

Trait Implementations

impl Clone for Lsn

fn clone(&self) -> Lsn

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Lsn

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Lsn

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Hash for Lsn

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Lsn

fn cmp(&self, other: &Lsn) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Lsn

fn eq(&self, other: &Lsn) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Lsn

fn partial_cmp(&self, other: &Lsn) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Serialize for Lsn

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Copy for Lsn

impl Eq for Lsn

impl StructuralPartialEq for Lsn