Struct ditto::counter::Counter

pub struct Counter { /* fields omitted */ }

A Counter is an i64 value that can be incremented and decremented via the increment function.

Internally, Counter is a variant of GCounter that allows op-based replication via execute_op and state-based replication via merge. Both replication methods are idempotent and can handle out-of-order delivery.

Counter has a spatial complexity of O(S), where S is the number of sites that have incremented the Counter. It has the following performance characteristics:

• increment: O(1)
• execute_op: O(1)
• merge: O(S), where S is the number of sites that have incremented the Counter

Methods

impl Counter

pub fn new(value: i64) -> Self

Constructs and returns a new Counter with site id 1.

pub fn get(&self) -> i64

Returns the counter value.

pub fn increment(&mut self, amount: i64) -> Result<Op, Error>

Increments the counter by the given amount and returns an op that can be replicated to other sites. If the counter does not have a site id, it caches the op and returns an AwaitingSiteId error.

pub fn site_id(&self) -> SiteId

Returns the Counter's site id.

pub fn state(&self) -> CounterState

Returns a reference to the Counter state.

pub fn clone_state(&self) -> CounterState<'static>

Clones and returns the Counter state.

pub fn into_state(self) -> CounterState<'static>

Consumes the Counter and returns its state.

pub fn from_state(
    state: CounterState,
    site_id: Option<SiteId>
) -> Result<Self, Error>

Constructs a new Counter from a state and optional site id. If the site is given, it must be nonzero.

pub fn execute_op(&mut self, op: &Op) -> Option<i64>

Executes an Op and returns the equivalent increment. If the op has already been executed or superceded, nothing is done.

pub fn validate_and_execute_op(
    &mut self,
    op: &Op,
    site_id: SiteId
) -> Result<Option<i64>, Error>

Validates that an op comes from a specific site id, then executes the op.

pub fn merge(&mut self, other: CounterState)

Merges remote state into the Counter.

pub fn add_site_id(&mut self, site_id: SiteId) -> Result<Option<Op>, Error>

Assigns a site id and returns a cached op if it exists.

Trait Implementations

impl Debug for Counter

fn fmt(&self, __arg_0: &mut Formatter) -> Result

Formats the value using the given formatter.

impl Clone for Counter

fn clone(&self) -> Counter

Returns a copy of the value.

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

Performs copy-assignment from source.

impl PartialEq for Counter

fn eq(&self, __arg_0: &Counter) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, __arg_0: &Counter) -> bool

This method tests for !=.