Struct PnCounter 

pub struct PnCounter { /* private fields */ }

An increment/decrement counter: a pair of G-Counters (increments P, decrements N), join = componentwise.

Model: Crdt.PNCounter ι = (ι → ℕ) × (ι → ℕ) with the Prod lattice. Deltas bump one side, one coordinate (SafeMesh.deltaBumpP / deltaBumpN); each side accumulates exactly as a delta G-Counter (SafeMesh.deltaPNCounter_correct_P / _N), and equal state gives an equal read (SafeMesh.deltaPNCounter_value_matches).

Implementations

impl PnCounter

pub fn new(n: usize) -> Self

Fresh counter for n replicas — the lattice bottom (⊥, ⊥).

Panics

Panics above GCounter::MAX_REPLICAS or if either side cannot be allocated. Use Self::try_new for a fallible width check.

pub fn try_new(n: usize) -> Result<Self, CoordinateError>

Reject counts above GCounter::MAX_REPLICAS (4,096) before allocation. This matches the wire author limit and bounds both sides to 64 KiB. Allocate both sides through the zeroed allocator path, as on main. Admitted allocation exhaustion follows the allocator’s out-of-memory policy.

pub fn apply_inc(&mut self, replica: usize, tally: u64)

Apply SafeMesh.deltaBumpP replica tally — increment side, one coordinate on the wire, ⊥ on the other side. Out-of-range indices are ignored; use Self::try_apply_inc for an error.

pub fn try_apply_inc( &mut self, replica: usize, tally: u64, ) -> Result<(), CoordinateError>

Apply an increment-side delta with a checked replica coordinate.

Returns CoordinateError::ReplicaOutOfRange before any mutation if the index is invalid. Both sides remain unchanged on error. Valid input has the same effect as Self::apply_inc.

pub fn apply_dec(&mut self, replica: usize, tally: u64)

Apply SafeMesh.deltaBumpN replica tally — decrement side. Out-of-range indices are ignored; use Self::try_apply_dec for an error.

pub fn try_apply_dec( &mut self, replica: usize, tally: u64, ) -> Result<(), CoordinateError>

Apply a decrement-side delta with a checked replica coordinate.

Returns CoordinateError::ReplicaOutOfRange before any mutation if the index is invalid. Both sides remain unchanged on error. Valid input has the same effect as Self::apply_dec.

pub fn try_merge(&mut self, other: &PnCounter) -> Result<(), MergeError>

Checked full-state merge: componentwise checked G-Counter merge, erroring on a replica-count mismatch on either side instead of silently truncating (WS1). Both sides are length-checked before any mutation, so the operation is all-or-nothing: on error self is left unchanged.

pub fn merge(&mut self, other: &PnCounter) -> Result<(), MergeError>

Full-state merge: componentwise G-Counter merge — Crdt.pncounter_merge_apply.

Returns MergeError::ReplicaCountMismatch without changing either side if the replica counts differ, just like PnCounter::try_merge.

pub fn p_state(&self) -> &[u64]

Increment-side state.

pub fn n_state(&self) -> &[u64]

Decrement-side state.

pub fn value(&self) -> i128

The counter’s read: (sum of increments) − (sum of decrements) — Crdt.pncounterValue, an integer with no bound in the model.

The read is exact for every representable state: each side’s total is below 2^127 (see GCounter::value), so both fit in i128 and their difference lies strictly inside i128’s range. No conversion here can change the sign or wrap; a positive total always reads positive.

Trait Implementations

impl Clone for PnCounter

fn clone(&self) -> PnCounter

Returns a duplicate of the value. Read more

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

Performs copy-assignment from source. Read more

impl Crdt for PnCounter

type Delta = PnCounterDelta

fn validate_record( &self, id: RecordId, delta: &Self::Delta, ) -> Result<(), WireError>

Validate a decoded record before admission or replay into this carrier.

fn replica_count(&self) -> Option<usize>

Fixed replica domain, or None for CRDTs without a fixed arity.

fn apply_delta(&mut self, delta: Self::Delta)

impl Debug for PnCounter

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

Formats the value using the given formatter. Read more

impl Mergeable for PnCounter

fn merge(&mut self, other: &Self) -> Result<(), MergeError>

Join compatible states, returning an error if their replica domains differ.

impl PartialEq for PnCounter

fn eq(&self, other: &PnCounter) -> 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 Eq for PnCounter

impl StructuralPartialEq for PnCounter