Version: 2.1.x

Class: Synchronizer

The synchronizer is used to construct the Unirep state. After events are emitted from the Unirep contract, the synchronizer will verify the events and then save the states.

Example

import { Synchronizer } from '@unirep/core'

const state = new Synchronizer({
  unirepAddress: '0xaabbccaabbccaabbccaabbccaabbccaabbccaaaa',
  provider, // an ethers.js provider
})

// start the synchronizer deamon
await state.start()
await state.waitForSync()

// stop the synchronizer deamon
state.stop()

Hierarchy

EventEmitter
↳ Synchronizer

Constructors

constructor

• new Synchronizer(config)

Parameters

Name	Type
`config`	`Object`
`config.attesterId?`	`bigint` \| `bigint`[]
`config.db?`	`DB`
`config.genesisBlock?`	`number`
`config.provider`	`Provider`
`config.unirepAddress`	`string`

Overrides

EventEmitter.constructor

Defined in

packages/core/src/Synchronizer.ts:168

Properties

_attesterId

• Private _attesterId: bigint[] = []

The array of attester IDs which are synchronized in the synchronizer.

Defined in

packages/core/src/Synchronizer.ts:79

_attesterSettings

• Private _attesterSettings: Object = {}

The settings of attesters. There are startTimestamp and epochLength of each attester.

Index signature

▪ [key: string]: AttesterSetting

Defined in

packages/core/src/Synchronizer.ts:89

_blockEnd

• Private _blockEnd: Number = 0

The latest completed block number.

Defined in

packages/core/src/Synchronizer.ts:166

_blocks

• Private _blocks: any[] = []

Unprocessed events.

Defined in

packages/core/src/Synchronizer.ts:161

_db

• Private _db: DB

The database object.

Defined in

packages/core/src/Synchronizer.ts:64

_eventFilters

• Private _eventFilters: any

The mapping of a contract address and its event filters.

Defined in

packages/core/src/Synchronizer.ts:115

_eventHandlers

• Private _eventHandlers: any

The mapping of the event name and its handler

Defined in

packages/core/src/Synchronizer.ts:110

_genesisBlock

• Private _genesisBlock: number = 0

Allow passing the genesis block as the starting block for querying events

Defined in

packages/core/src/Synchronizer.ts:133

_provider

• Private _provider: Provider

The provider which is connected in the synchronizer.

Defined in

packages/core/src/Synchronizer.ts:69

_settings

• Private _settings: any

The circuits settings.

Defined in

packages/core/src/Synchronizer.ts:84

_syncAll

• Private _syncAll: boolean = false

Indicates if the synchronizer is to sync with all Unirep attesters.

Defined in

packages/core/src/Synchronizer.ts:104

_unirepContract

• Private _unirepContract: Contract

The UniRep smart contract object which is connected in the synchronizer.

Defined in

packages/core/src/Synchronizer.ts:74

blockRate

• blockRate: number = 10000

How many blocks the synchronizer will query on each poll. Default: 100000

Defined in

packages/core/src/Synchronizer.ts:129

defaultEpochTreeLeaf

• Protected defaultEpochTreeLeaf: bigint

The default zero epoch tree leaf.

Defined in

packages/core/src/Synchronizer.ts:99

defaultStateTreeLeaf

• Protected defaultStateTreeLeaf: bigint

The default zero state tree leaf.

Defined in

packages/core/src/Synchronizer.ts:94

lock

• Private lock: any

Lock on poll event.

Defined in

packages/core/src/Synchronizer.ts:150

pollId

• Private pollId: null | string = null

The id of the poll event.

Defined in

packages/core/src/Synchronizer.ts:121

pollRate

• pollRate: number = 5000

How frequently the synchronizer will poll the blockchain for new events (specified in milliseconds). Default: 5000

Defined in

packages/core/src/Synchronizer.ts:125

promises

• Private promises: any[] = []

Load events promises.

Defined in

packages/core/src/Synchronizer.ts:156

setupComplete

• Private setupComplete: boolean = false

Check if a setup is completed or not.

Defined in

packages/core/src/Synchronizer.ts:139

setupPromise

• Private setupPromise: any

If a setup is not completed, there will be a setup promise.

Defined in

packages/core/src/Synchronizer.ts:144

captureRejectionSymbol

▪ Static Readonly captureRejectionSymbol: typeof captureRejectionSymbol

Value: Symbol.for('nodejs.rejection')

See how to write a custom rejection handler.

Since

v13.4.0, v12.16.0

Inherited from

EventEmitter.captureRejectionSymbol

Defined in

node_modules/@types/node/events.d.ts:402

captureRejections

▪ Static captureRejections: boolean

Value: boolean

Change the default captureRejections option on all new EventEmitter objects.

Since

v13.4.0, v12.16.0

Inherited from

EventEmitter.captureRejections

Defined in

node_modules/@types/node/events.d.ts:409

defaultMaxListeners

▪ Static defaultMaxListeners: number

By default, a maximum of 10 listeners can be registered for any single event. This limit can be changed for individual EventEmitter instances using the emitter.setMaxListeners(n) method. To change the default for allEventEmitter instances, the events.defaultMaxListenersproperty can be used. If this value is not a positive number, a RangeErroris thrown.

Take caution when setting the events.defaultMaxListeners because the change affects allEventEmitter instances, including those created before the change is made. However, calling emitter.setMaxListeners(n) still has precedence over events.defaultMaxListeners.

This is not a hard limit. The EventEmitter instance will allow more listeners to be added but will output a trace warning to stderr indicating that a "possible EventEmitter memory leak" has been detected. For any singleEventEmitter, the emitter.getMaxListeners() and emitter.setMaxListeners()methods can be used to temporarily avoid this warning:

import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.setMaxListeners(emitter.getMaxListeners() + 1);
emitter.once('event', () => {
  // do stuff
  emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));
});

The --trace-warnings command-line flag can be used to display the stack trace for such warnings.

The emitted warning can be inspected with process.on('warning') and will have the additional emitter, type, and count properties, referring to the event emitter instance, the event's name and the number of attached listeners, respectively. Its name property is set to 'MaxListenersExceededWarning'.

Since

v0.11.2

Inherited from

EventEmitter.defaultMaxListeners

Defined in

node_modules/@types/node/events.d.ts:446

errorMonitor

▪ Static Readonly errorMonitor: typeof errorMonitor

This symbol shall be used to install a listener for only monitoring 'error'events. Listeners installed using this symbol are called before the regular'error' listeners are called.

Installing a listener using this symbol does not change the behavior once an'error' event is emitted. Therefore, the process will still crash if no regular 'error' listener is installed.

Since

v13.6.0, v12.17.0

Inherited from

EventEmitter.errorMonitor

Defined in

node_modules/@types/node/events.d.ts:395

Accessors

attesterId

• get attesterId(): bigint

The default attester ID that is set when constructed. If there is a list of attester IDs, then the first one will be the default attester ID. If no attester ID is given during construction, all attesters will be synchronized and the default attesterId will be BigInt(0).

caution

The default attester ID should be checked carefully while synchronizing more than one attester. The default attester ID can be changed with setAttesterId.

Returns

bigint

Defined in

packages/core/src/Synchronizer.ts:331

attestersOrClauses

• get attestersOrClauses(): any[]

Returns

any[]

Defined in

packages/core/src/Synchronizer.ts:336

contracts

• get contracts(): Object

Overwrite this to query events in different attester addresses.

Returns

Object

Example

export class AppSynchronizer extends Synchronizer {
...
  get contracts(){
    return {
      ...super.contracts,
      [this.appContract.address]: {
          contract: this.appContract,
          eventNames: [
            'Event1',
            'Event2',
            'Event3',
            ...
          ]
      }
  }
}

Defined in

packages/core/src/Synchronizer.ts:707

db

• get db(): DB

Read the database object.

Returns

DB

Defined in

packages/core/src/Synchronizer.ts:289

genesisBlock

• get genesisBlock(): number

Read the genesis block of the provider environment.

Returns

number

Defined in

packages/core/src/Synchronizer.ts:317

provider

• get provider(): Provider

Read the provider which is connected in the synchronizer.

Returns

Provider

Defined in

packages/core/src/Synchronizer.ts:296

settings

• get settings(): any

Read the settings of the UniRep smart contract.

Returns

any

Defined in

packages/core/src/Synchronizer.ts:310

unirepContract

• get unirepContract(): Contract

Read the UniRep smart contract object which is connected in the synchronizer.

Returns

Contract

Defined in

packages/core/src/Synchronizer.ts:303

Methods

[captureRejectionSymbol]

▸ Optional [captureRejectionSymbol](error, event, ...args): void

Parameters

Name	Type
`error`	`Error`
`event`	`string`
`...args`	`any`[]

Returns

void

Inherited from

EventEmitter.[captureRejectionSymbol]

Defined in

node_modules/@types/node/events.d.ts:112

_findStartBlock

▸ Private _findStartBlock(): Promise<void>

Find the attester's genesis block in the Unirep smart contract. Then store the startTimestamp and epochLength in database and in the memory.

Returns

Promise<void>

Defined in

packages/core/src/Synchronizer.ts:429

_poll

▸ Private _poll(): Promise<{ complete: boolean }>

Execute polling events and processing events.

Returns

Promise<{ complete: boolean }>

Defined in

packages/core/src/Synchronizer.ts:552

_setup

▸ _setup(): Promise<void>

Query settings from smart contract and setup event handlers.

Returns

Promise<void>

Defined in

packages/core/src/Synchronizer.ts:408

addListener

▸ addListener(eventName, listener): Synchronizer

Alias for emitter.on(eventName, listener).

Parameters

Name	Type
`eventName`	`string` \| `symbol`
`listener`	(...`args`: `any`[]) => `void`

Returns

Synchronizer

Since

v0.1.26

Inherited from

EventEmitter.addListener

Defined in

node_modules/@types/node/events.d.ts:510

attesterExist

▸ attesterExist(attesterId): boolean

Check if attester events are synchronized in this synchronizer.

Parameters

Name	Type	Description
`attesterId`	`string` \| `bigint`	The queried attester ID.

Returns

boolean

True if the attester events are synced, false otherwise.

Defined in

packages/core/src/Synchronizer.ts:369

buildEventHandlers

▸ Private buildEventHandlers(): void

Returns

void

Defined in

packages/core/src/Synchronizer.ts:211

calcCurrentEpoch

▸ calcCurrentEpoch(attesterId?): number

Calculate the current epoch determining the amount of time since the attester registration timestamp. This operation is synchronous and does not involve any database operations.

Parameters

Name	Type	Description
`attesterId`	`string` \| `bigint`	The queried attester Id.

Returns

number

The number of current calculated epoch.

Defined in

packages/core/src/Synchronizer.ts:834

calcEpochRemainingTime

▸ calcEpochRemainingTime(attesterId?): number

Calculate the amount of time remaining in the current epoch. This operation is synchronous and does not involve any database operations.

Parameters

Name	Type	Description
`attesterId`	`string` \| `bigint`	The queried attester Id.

Returns

number

Current calculated time to the next epoch.

Defined in

packages/core/src/Synchronizer.ts:851

checkAttesterId

▸ checkAttesterId(attesterId): void

Check if attester events are synchronized in this synchronizer. It will throw an error if the attester is not synchronized.

Parameters

Name	Type	Description
`attesterId`	`string` \| `bigint`	The queried attester ID.

Returns

void

Defined in

packages/core/src/Synchronizer.ts:377

emit

▸ emit(eventName, ...args): boolean

Synchronously calls each of the listeners registered for the event namedeventName, in the order they were registered, passing the supplied arguments to each.

Returns true if the event had listeners, false otherwise.

import { EventEmitter } from 'node:events';
const myEmitter = new EventEmitter();

// First listener
myEmitter.on('event', function firstListener() {
  console.log('Helloooo! first listener');
});
// Second listener
myEmitter.on('event', function secondListener(arg1, arg2) {
  console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
});
// Third listener
myEmitter.on('event', function thirdListener(...args) {
  const parameters = args.join(', ');
  console.log(`event with parameters ${parameters} in third listener`);
});

console.log(myEmitter.listeners('event'));

myEmitter.emit('event', 1, 2, 3, 4, 5);

// Prints:
// [
//   [Function: firstListener],
//   [Function: secondListener],
//   [Function: thirdListener]
// ]
// Helloooo! first listener
// event with parameters 1, 2 in second listener
// event with parameters 1, 2, 3, 4, 5 in third listener

Parameters

Name	Type
`eventName`	`string` \| `symbol`
`...args`	`any`[]

Returns

boolean

Since

v0.1.26

Inherited from

EventEmitter.emit

Defined in

node_modules/@types/node/events.d.ts:772

epochTreeProof

▸ epochTreeProof(epoch, leafIndex, attesterId?): Promise<MerkleProof>

Build a merkle inclusion proof for the tree from a certain epoch.

Parameters

Name	Type	Description
`epoch`	`number`	The epoch to be queried.
`leafIndex`	`any`	The leaf index to be queried.
`attesterId`	`string` \| `bigint`	The attester to be queried.

Returns

Promise<MerkleProof>

The merkle proof of the epoch tree index.

Defined in

packages/core/src/Synchronizer.ts:895

epochTreeRoot

▸ epochTreeRoot(epoch, attesterId?): Promise<any>

Get the epoch tree root for a certain epoch.

Parameters

Name	Type	Description
`epoch`	`number`	The epoch to be queried.
`attesterId`	`string` \| `bigint`	The attester to be queried.

Returns

Promise<any>

The epoch tree root.

Defined in

packages/core/src/Synchronizer.ts:881

epochTreeRootExists

▸ epochTreeRootExists(root, epoch, attesterId?): Promise<boolean>

Check if the epoch tree root is stored in the database.

Parameters

Name	Type	Description
`root`	`string` \| `bigint`	The queried epoch tree root
`epoch`	`number`	The queried epoch of the epoch tree
`attesterId`	`string` \| `bigint`	The attester to be queried.

Returns

Promise<boolean>

True if the epoch tree root is in the database, false otherwise.

Note

caution

Epoch tree root of current epoch might change frequently and the tree root is not stored everytime. Try use this function when querying the epoch tree in the previous epoch.

Defined in

packages/core/src/Synchronizer.ts:1033

eventNames

▸ eventNames(): (string | symbol)[]

Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.

import { EventEmitter } from 'node:events';

const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});

const sym = Symbol('symbol');
myEE.on(sym, () => {});

console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]

Returns

(string | symbol)[]

Since

v6.0.0

Inherited from

EventEmitter.eventNames

Defined in

node_modules/@types/node/events.d.ts:835

genEpochTree

▸ genEpochTree(epoch, attesterId?): Promise<IncrementalMerkleTree>

Build the latest epoch tree for a certain epoch.

Parameters

Name	Type	Description
`epoch`	`number` \| `bigint`	The epoch to be queried.
`attesterId`	`string` \| `bigint`	The attester to be queried.

Returns

Promise<IncrementalMerkleTree>

The epoch tree.

Defined in

packages/core/src/Synchronizer.ts:977

genHistoryTree

▸ genHistoryTree(attesterId?): Promise<IncrementalMerkleTree>

Build the latest history tree for the current attester.

Parameters

Name	Type	Description
`attesterId`	`string` \| `bigint`	The attester to be queried.

Returns

Promise<IncrementalMerkleTree>

The history tree.

Defined in

packages/core/src/Synchronizer.ts:951

genStateTree

▸ genStateTree(epoch, attesterId?): Promise<IncrementalMerkleTree>

Build the latest state tree for a certain epoch.

Parameters

Name	Type	Description
`epoch`	`number` \| `bigint`	The epoch to be queried.
`attesterId`	`string` \| `bigint`	The attester to be queried.

Returns

Promise<IncrementalMerkleTree>

The state tree.

Defined in

packages/core/src/Synchronizer.ts:921

getMaxListeners

▸ getMaxListeners(): number

Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to defaultMaxListeners.

Returns

number

Since

v1.0.0

Inherited from

EventEmitter.getMaxListeners

Defined in

node_modules/@types/node/events.d.ts:687

handleAttestation

▸ handleAttestation(args): Promise<undefined | true>

Handle attestation event

Parameters

Name	Type	Description
`args`	`EventHandlerArgs`	`EventHandlerArgs` type arguments.

Returns

Promise<undefined | true>

True if succeeds, false otherwise.

Defined in

packages/core/src/Synchronizer.ts:1155

handleAttesterSignedUp

▸ handleAttesterSignedUp(args): Promise<undefined | true>

Handle attester signup event

Parameters

Name	Type	Description
`args`	`EventHandlerArgs`	`EventHandlerArgs` type arguments.

Returns

Promise<undefined | true>

True if succeeds, false otherwise.

Defined in

packages/core/src/Synchronizer.ts:1295

handleEpochEnded

▸ handleEpochEnded(args): Promise<undefined | true>

Handle epoch ended event

Parameters

Name	Type	Description
`args`	`EventHandlerArgs`	`EventHandlerArgs` type arguments.

Returns

Promise<undefined | true>

True if succeeds, false otherwise.

Defined in

packages/core/src/Synchronizer.ts:1245

handleEpochTreeLeaf

▸ handleEpochTreeLeaf(args): Promise<undefined | true>

Handle epoch tree leaf event

Parameters

Name	Type	Description
`args`	`EventHandlerArgs`	`EventHandlerArgs` type arguments.

Returns

Promise<undefined | true>

True if succeeds, false otherwise.

Defined in

packages/core/src/Synchronizer.ts:1094

handleHistoryTreeLeaf

▸ handleHistoryTreeLeaf(args): Promise<undefined | true>

Handle history tree leaf event

Parameters

Name	Type	Description
`args`	`EventHandlerArgs`	`EventHandlerArgs` type arguments.

Returns

Promise<undefined | true>

True if succeeds, false otherwise.

Defined in

packages/core/src/Synchronizer.ts:1338

handleStateTreeLeaf

▸ handleStateTreeLeaf(args): Promise<undefined | true>

Handle state tree leaf event

Parameters

Name	Type	Description
`args`	`EventHandlerArgs`	`EventHandlerArgs` type arguments.

Returns

Promise<undefined | true>

True if succeeds, false otherwise.

Defined in

packages/core/src/Synchronizer.ts:1067

handleUserSignedUp

▸ handleUserSignedUp(args): Promise<undefined | true>

Handle user signup event

Parameters

Name	Type	Description
`args`	`EventHandlerArgs`	`EventHandlerArgs` type arguments.

Returns

Promise<undefined | true>

True if succeeds, false otherwise.

Defined in

packages/core/src/Synchronizer.ts:1127

handleUserStateTransitioned

▸ handleUserStateTransitioned(args): Promise<undefined | true>

Handle user state transition event

Parameters

Name	Type	Description
`args`	`EventHandlerArgs`	`EventHandlerArgs` type arguments.

Returns

Promise<undefined | true>

True if succeeds, false otherwise.

Defined in

packages/core/src/Synchronizer.ts:1213

listenerCount

▸ listenerCount(eventName, listener?): number

Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

Parameters

Name	Type	Description
`eventName`	`string` \| `symbol`	The name of the event being listened for
`listener?`	`Function`	The event handler function

Returns

number

Since

v3.2.0

Inherited from

EventEmitter.listenerCount

Defined in

node_modules/@types/node/events.d.ts:781

listeners

▸ listeners(eventName): Function[]

Returns a copy of the array of listeners for the event named eventName.

server.on('connection', (stream) => {
  console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]

Parameters

Name	Type
`eventName`	`string` \| `symbol`

Returns

Function[]

Since

v0.1.26

Inherited from

EventEmitter.listeners

Defined in

node_modules/@types/node/events.d.ts:700

loadBlocks

▸ loadBlocks(n): Promise<void>

Load more events from the smart contract.

Parameters

Name	Type	Description
`n`	`number`	How many blocks will be loaded.

Returns

Promise<void>

Defined in

packages/core/src/Synchronizer.ts:607

loadCurrentEpoch

▸ loadCurrentEpoch(attesterId?): Promise<number>

Load the current epoch number from the blockchain.

tip

Use this function in test environments where the blockchain timestamp may not match the real timestamp (e.g. due to snapshot/revert patterns).

Parameters

Name	Type	Description
`attesterId`	`string` \| `bigint`	The queried attester Id.

Returns

Promise<number>

The number of current epoch on-chain.

Defined in

packages/core/src/Synchronizer.ts:870

loadNewEvents

▸ loadNewEvents(fromBlock, toBlock): Promise<any[]>

Load new event from smart contract.

Parameters

Name	Type	Description
`fromBlock`	`number`	From which block number.
`toBlock`	`number`	To which block number.

Returns

Promise<any[]>

All events in the block range.

Defined in

packages/core/src/Synchronizer.ts:653

nullifierExist

▸ nullifierExist(nullifier): Promise<any>

Determine if a nullifier exists. All nullifiers are stored in a single mapping and expected to be globally unique.

Parameters

Name	Type	Description
`nullifier`	`any`	A nullifier to be queried.

Returns

Promise<any>

True if the nullifier exists on-chain before, false otherwise.

Defined in

packages/core/src/Synchronizer.ts:910

numStateTreeLeaves

▸ numStateTreeLeaves(epoch, attesterId?): Promise<number>

Get the number of state tree leaves in a certain epoch.

Parameters

Name	Type	Description
`epoch`	`number`	The queried epoch.
`attesterId`	`string` \| `bigint`	-

Returns

Promise<number>

The number of the state tree leaves.

Defined in

packages/core/src/Synchronizer.ts:1050

off

▸ off(eventName, listener): Synchronizer

Alias for emitter.removeListener().

Parameters

Name	Type
`eventName`	`string` \| `symbol`
`listener`	(...`args`: `any`[]) => `void`

Returns

Synchronizer

Since

v10.0.0

Inherited from

EventEmitter.off

Defined in

node_modules/@types/node/events.d.ts:660

on

▸ on(eventName, listener): Synchronizer

Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple times.

server.on('connection', (stream) => {
  console.log('someone connected!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. Theemitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
//   b
//   a

Parameters

Name	Type	Description
`eventName`	`string` \| `symbol`	The name of the event.
`listener`	(...`args`: `any`[]) => `void`	The callback function

Returns

Synchronizer

Since

v0.1.101

Inherited from

EventEmitter.on

Defined in

node_modules/@types/node/events.d.ts:542

once

▸ once(eventName, listener): Synchronizer

Adds a one-timelistener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

server.once('connection', (stream) => {
  console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. Theemitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
//   b
//   a

Parameters

Name	Type	Description
`eventName`	`string` \| `symbol`	The name of the event.
`listener`	(...`args`: `any`[]) => `void`	The callback function

Returns

Synchronizer

Since

v0.3.0

Inherited from

EventEmitter.once

Defined in

node_modules/@types/node/events.d.ts:572

poll

▸ poll(): Promise<{ complete: boolean }>

Manually poll for new events. Returns a boolean indicating whether the synchronizer has synced to the head of the blockchain.

Returns

Promise<{ complete: boolean }>

Defined in

packages/core/src/Synchronizer.ts:544

prependListener

▸ prependListener(eventName, listener): Synchronizer

Adds the listener function to the beginning of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple times.

server.prependListener('connection', (stream) => {
  console.log('someone connected!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

Name	Type	Description
`eventName`	`string` \| `symbol`	The name of the event.
`listener`	(...`args`: `any`[]) => `void`	The callback function

Returns

Synchronizer

Since

v6.0.0

Inherited from

EventEmitter.prependListener

Defined in

node_modules/@types/node/events.d.ts:799

prependOnceListener

▸ prependOnceListener(eventName, listener): Synchronizer

Adds a one-timelistener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

server.prependOnceListener('connection', (stream) => {
  console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

Name	Type	Description
`eventName`	`string` \| `symbol`	The name of the event.
`listener`	(...`args`: `any`[]) => `void`	The callback function

Returns

Synchronizer

Since

v6.0.0

Inherited from

EventEmitter.prependOnceListener

Defined in

node_modules/@types/node/events.d.ts:815

processEvents

▸ Private processEvents(events): Promise<void>

Process events with each event handler.

Parameters

Name	Type	Description
`events`	`Event`[]	The array of events will be proccessed.

Returns

Promise<void>

Defined in

packages/core/src/Synchronizer.ts:729

rawListeners

▸ rawListeners(eventName): Function[]

Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));

// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];

// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();

// Logs "log once" to the console and removes the listener
logFnWrapper();

emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');

// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');

Parameters

Name	Type
`eventName`	`string` \| `symbol`

Returns

Function[]

Since

v9.4.0

Inherited from

EventEmitter.rawListeners

Defined in

node_modules/@types/node/events.d.ts:731

readCurrentEpoch

▸ readCurrentEpoch(attesterId?): Promise<any>

Get the latest processed epoch from the database.

caution

This value may mismatch the onchain value depending on synchronization status.

Parameters

Name	Type	Description
`attesterId`	`string` \| `bigint`	The queried attester Id.

Returns

Promise<any>

{number: number, sealed: boolean}

Defined in

packages/core/src/Synchronizer.ts:811

removeAllListeners

▸ removeAllListeners(event?): Synchronizer

Removes all listeners, or those of the specified eventName.

It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

Name	Type
`event?`	`string` \| `symbol`

Returns

Synchronizer

Since

v0.1.26

Inherited from

EventEmitter.removeAllListeners

Defined in

node_modules/@types/node/events.d.ts:671

removeListener

▸ removeListener(eventName, listener): Synchronizer

Removes the specified listener from the listener array for the event namedeventName.

const callback = (stream) => {
  console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);

removeListener() will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener() must be called multiple times to remove each instance.

Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that anyremoveListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them fromemit() in progress. Subsequent events behave as expected.

import { EventEmitter } from 'node:events';
class MyEmitter extends EventEmitter {}
const myEmitter = new MyEmitter();

const callbackA = () => {
  console.log('A');
  myEmitter.removeListener('event', callbackB);
};

const callbackB = () => {
  console.log('B');
};

myEmitter.on('event', callbackA);

myEmitter.on('event', callbackB);

// callbackA removes listener callbackB but it will still be called.
// Internal listener array at time of emit [callbackA, callbackB]
myEmitter.emit('event');
// Prints:
//   A
//   B

// callbackB is now removed.
// Internal listener array [callbackA]
myEmitter.emit('event');
// Prints:
//   A

Because listeners are managed using an internal array, calling this will change the position indices of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping')listener is removed:

import { EventEmitter } from 'node:events';
const ee = new EventEmitter();

function pong() {
  console.log('pong');
}

ee.on('ping', pong);
ee.once('ping', pong);
ee.removeListener('ping', pong);

ee.emit('ping');
ee.emit('ping');

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

Name	Type
`eventName`	`string` \| `symbol`
`listener`	(...`args`: `any`[]) => `void`

Returns

Synchronizer

Since

v0.1.26

Inherited from

EventEmitter.removeListener

Defined in

node_modules/@types/node/events.d.ts:655

setAttesterId

▸ setAttesterId(attesterId): void

Change default attesterId to another attester ID. It will fail if an attesterId is not synchronized during construction.

Parameters

Name	Type	Description
`attesterId`	`string` \| `bigint`	The default attester Id to be set.

Returns

void

Defined in

packages/core/src/Synchronizer.ts:351

setMaxListeners

▸ setMaxListeners(n): Synchronizer

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set toInfinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

Name	Type
`n`	`number`

Returns

Synchronizer

Since

v0.3.5

Inherited from

EventEmitter.setMaxListeners

Defined in

node_modules/@types/node/events.d.ts:681

setup

▸ setup(): Promise<any>

Run setup promises.

Returns

Promise<any>

Setup promises.

Defined in

packages/core/src/Synchronizer.ts:394

start

▸ start(): Promise<void>

Start the synchronizer daemon. Start polling the blockchain for new events. If we're behind the HEAD block we'll poll many times quickly

Returns

Promise<void>

Defined in

packages/core/src/Synchronizer.ts:491

stateTreeRootExists

▸ stateTreeRootExists(root, epoch, attesterId?): Promise<any>

Determine if a state root exists in a certain epoch.

Parameters

Name	Type	Description
`root`	`string` \| `bigint`	The queried global state tree root
`epoch`	`number`	The queried epoch of the global state tree
`attesterId`	`string` \| `bigint`	The attester to be queried.

Returns

Promise<any>

True if the global state tree root exists, false otherwise.

Defined in

packages/core/src/Synchronizer.ts:1009

stop

▸ stop(): void

Stop synchronizing with Unirep contract.

Returns

void

Defined in

packages/core/src/Synchronizer.ts:536

waitForSync

▸ waitForSync(blockNumber?): Promise<void>

Wait for the synchronizer to sync up to a certain block. By default this will wait until the current latest known block (according to the provider).

Parameters

Name	Type	Description
`blockNumber?`	`number`	The block number to be synced to.

Returns

Promise<void>

Defined in

packages/core/src/Synchronizer.ts:785

addAbortListener

▸ Static addAbortListener(signal, resource): Disposable

Listens once to the abort event on the provided signal.

Listening to the abort event on abort signals is unsafe and may lead to resource leaks since another third party with the signal can call e.stopImmediatePropagation(). Unfortunately Node.js cannot change this since it would violate the web standard. Additionally, the original API makes it easy to forget to remove listeners.

This API allows safely using AbortSignals in Node.js APIs by solving these two issues by listening to the event such that stopImmediatePropagation does not prevent the listener from running.

Returns a disposable so that it may be unsubscribed from more easily.

import { addAbortListener } from 'node:events';

function example(signal) {
  let disposable;
  try {
    signal.addEventListener('abort', (e) => e.stopImmediatePropagation());
    disposable = addAbortListener(signal, (e) => {
      // Do something when signal is aborted.
    });
  } finally {
    disposable?.[Symbol.dispose]();
  }
}

Parameters

Name	Type
`signal`	`AbortSignal`
`resource`	(`event`: `Event`) => `void`

Returns

Disposable

Disposable that removes the abort listener.

Since

v20.5.0

Inherited from

EventEmitter.addAbortListener

Defined in

node_modules/@types/node/events.d.ts:387

getEventListeners

▸ Static getEventListeners(emitter, name): Function[]

Returns a copy of the array of listeners for the event named eventName.

For EventEmitters this behaves exactly the same as calling .listeners on the emitter.

For EventTargets this is the only way to get the event listeners for the event target. This is useful for debugging and diagnostic purposes.

import { getEventListeners, EventEmitter } from 'node:events';

{
  const ee = new EventEmitter();
  const listener = () => console.log('Events are fun');
  ee.on('foo', listener);
  console.log(getEventListeners(ee, 'foo')); // [ [Function: listener] ]
}
{
  const et = new EventTarget();
  const listener = () => console.log('Events are fun');
  et.addEventListener('foo', listener);
  console.log(getEventListeners(et, 'foo')); // [ [Function: listener] ]
}

Parameters

Name	Type
`emitter`	`EventEmitter` \| `_DOMEventTarget`
`name`	`string` \| `symbol`

Returns

Function[]

Since

v15.2.0, v14.17.0

Inherited from

EventEmitter.getEventListeners

Defined in

node_modules/@types/node/events.d.ts:308

getMaxListeners

▸ Static getMaxListeners(emitter): number

Returns the currently set max amount of listeners.

For EventEmitters this behaves exactly the same as calling .getMaxListeners on the emitter.

For EventTargets this is the only way to get the max event listeners for the event target. If the number of event handlers on a single EventTarget exceeds the max set, the EventTarget will print a warning.

import { getMaxListeners, setMaxListeners, EventEmitter } from 'node:events';

{
  const ee = new EventEmitter();
  console.log(getMaxListeners(ee)); // 10
  setMaxListeners(11, ee);
  console.log(getMaxListeners(ee)); // 11
}
{
  const et = new EventTarget();
  console.log(getMaxListeners(et)); // 10
  setMaxListeners(11, et);
  console.log(getMaxListeners(et)); // 11
}

Parameters

Name	Type
`emitter`	`EventEmitter` \| `_DOMEventTarget`

Returns

number

Since

v19.9.0

Inherited from

EventEmitter.getMaxListeners

Defined in

node_modules/@types/node/events.d.ts:337

listenerCount

▸ Static listenerCount(emitter, eventName): number

A class method that returns the number of listeners for the given eventNameregistered on the given emitter.

import { EventEmitter, listenerCount } from 'node:events';

const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2

Parameters

Name	Type	Description
`emitter`	`EventEmitter`	The emitter to query
`eventName`	`string` \| `symbol`	The event name

Returns

number

Since

v0.9.12

Deprecated

Since v3.2.0 - Use listenerCount instead.

Inherited from

EventEmitter.listenerCount

Defined in

node_modules/@types/node/events.d.ts:280

on

▸ Static on(emitter, eventName, options?): AsyncIterableIterator<any>

import { on, EventEmitter } from 'node:events';
import process from 'node:process';

const ee = new EventEmitter();

// Emit later on
process.nextTick(() => {
  ee.emit('foo', 'bar');
  ee.emit('foo', 42);
});

for await (const event of on(ee, 'foo')) {
  // The execution of this inner block is synchronous and it
  // processes one event at a time (even with await). Do not use
  // if concurrent execution is required.
  console.log(event); // prints ['bar'] [42]
}
// Unreachable here

Returns an AsyncIterator that iterates eventName events. It will throw if the EventEmitter emits 'error'. It removes all listeners when exiting the loop. The value returned by each iteration is an array composed of the emitted event arguments.

An AbortSignal can be used to cancel waiting on events:

import { on, EventEmitter } from 'node:events';
import process from 'node:process';

const ac = new AbortController();

(async () => {
  const ee = new EventEmitter();

  // Emit later on
  process.nextTick(() => {
    ee.emit('foo', 'bar');
    ee.emit('foo', 42);
  });

  for await (const event of on(ee, 'foo', { signal: ac.signal })) {
    // The execution of this inner block is synchronous and it
    // processes one event at a time (even with await). Do not use
    // if concurrent execution is required.
    console.log(event); // prints ['bar'] [42]
  }
  // Unreachable here
})();

process.nextTick(() => ac.abort());

Parameters

Name	Type	Description
`emitter`	`EventEmitter`	-
`eventName`	`string`	The name of the event being listened for
`options?`	`StaticEventEmitterOptions`	-

Returns

AsyncIterableIterator<any>

that iterates eventName events emitted by the emitter

Since

v13.6.0, v12.16.0

Inherited from

EventEmitter.on

Defined in

node_modules/@types/node/events.d.ts:258

once

▸ Static once(emitter, eventName, options?): Promise<any[]>

Creates a Promise that is fulfilled when the EventEmitter emits the given event or that is rejected if the EventEmitter emits 'error' while waiting. The Promise will resolve with an array of all the arguments emitted to the given event.

This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event semantics and does not listen to the 'error' event.

import { once, EventEmitter } from 'node:events';
import process from 'node:process';

const ee = new EventEmitter();

process.nextTick(() => {
  ee.emit('myevent', 42);
});

const [value] = await once(ee, 'myevent');
console.log(value);

const err = new Error('kaboom');
process.nextTick(() => {
  ee.emit('error', err);
});

try {
  await once(ee, 'myevent');
} catch (err) {
  console.error('error happened', err);
}

The special handling of the 'error' event is only used when events.once()is used to wait for another event. If events.once() is used to wait for the 'error' event itself, then it is treated as any other kind of event without special handling:

import { EventEmitter, once } from 'node:events';

const ee = new EventEmitter();

once(ee, 'error')
  .then(([err]) => console.log('ok', err.message))
  .catch((err) => console.error('error', err.message));

ee.emit('error', new Error('boom'));

// Prints: ok boom

An AbortSignal can be used to cancel waiting for the event:

import { EventEmitter, once } from 'node:events';

const ee = new EventEmitter();
const ac = new AbortController();

async function foo(emitter, event, signal) {
  try {
    await once(emitter, event, { signal });
    console.log('event emitted!');
  } catch (error) {
    if (error.name === 'AbortError') {
      console.error('Waiting for the event was canceled!');
    } else {
      console.error('There was an error', error.message);
    }
  }
}

foo(ee, 'foo', ac.signal);
ac.abort(); // Abort waiting for the event
ee.emit('foo'); // Prints: Waiting for the event was canceled!

Parameters

Name	Type
`emitter`	`_NodeEventTarget`
`eventName`	`string` \| `symbol`
`options?`	`StaticEventEmitterOptions`

Returns

Promise<any[]>

Since

v11.13.0, v10.16.0

Inherited from

EventEmitter.once

Defined in

node_modules/@types/node/events.d.ts:193

▸ Static once(emitter, eventName, options?): Promise<any[]>

Parameters

Name	Type
`emitter`	`_DOMEventTarget`
`eventName`	`string`
`options?`	`StaticEventEmitterOptions`

Returns

Promise<any[]>

Inherited from

EventEmitter.once

Defined in

node_modules/@types/node/events.d.ts:198

setMaxListeners

▸ Static setMaxListeners(n?, ...eventTargets): void

import { setMaxListeners, EventEmitter } from 'node:events';

const target = new EventTarget();
const emitter = new EventEmitter();

setMaxListeners(5, target, emitter);

Parameters

Name	Type	Description
`n?`	`number`	A non-negative number. The maximum number of listeners per `EventTarget` event.
`...eventTargets`	(`EventEmitter` \| `_DOMEventTarget`)[]	-

Returns

void

Since

v15.4.0

Inherited from

EventEmitter.setMaxListeners

Defined in

node_modules/@types/node/events.d.ts:352

Hierarchy​

Constructors​

constructor​

Parameters​

Overrides​

Defined in​

Properties​

_attesterId​

Defined in​

_attesterSettings​

Index signature​

Defined in​

_blockEnd​

Defined in​

_blocks​

Defined in​

_db​

Defined in​

_eventFilters​

Defined in​

_eventHandlers​

Defined in​

_genesisBlock​

Defined in​

_provider​

Defined in​

_settings​

Defined in​

_syncAll​

Defined in​

_unirepContract​

Defined in​

blockRate​

Defined in​

defaultEpochTreeLeaf​

Defined in​

defaultStateTreeLeaf​

Defined in​

lock​

Defined in​

pollId​

Defined in​

pollRate​

Defined in​

promises​

Defined in​

setupComplete​

Defined in​

setupPromise​

Defined in​

captureRejectionSymbol​

Inherited from​

Defined in​

captureRejections​

Inherited from​

Defined in​

defaultMaxListeners​

Inherited from​

Defined in​

errorMonitor​

Inherited from​

Defined in​

Accessors​

attesterId​

Returns​

Defined in​

attestersOrClauses​

Returns​

Defined in​

contracts​

Returns​

Defined in​

db​

Returns​

Defined in​

genesisBlock​

Returns​

Defined in​

provider​

Returns​

Hierarchy

Constructors

constructor

Parameters

Overrides

Defined in

Properties

_attesterId

Defined in

_attesterSettings

Index signature

Defined in

_blockEnd

Defined in

_blocks

Defined in

_db

Defined in

_eventFilters

Defined in

_eventHandlers

Defined in

_genesisBlock

Defined in

_provider

Defined in

_settings

Defined in

_syncAll

Defined in

_unirepContract

Defined in

blockRate

Defined in

defaultEpochTreeLeaf

Defined in

defaultStateTreeLeaf

Defined in

lock

Defined in

pollId

Defined in

pollRate

Defined in

promises

Defined in

setupComplete

Defined in

setupPromise

Defined in

captureRejectionSymbol

Inherited from

Defined in

captureRejections

Inherited from

Defined in

defaultMaxListeners

Inherited from

Defined in

errorMonitor

Inherited from

Defined in

Accessors

attesterId

Returns

Defined in

attestersOrClauses

Returns

Defined in

contracts

Returns

Defined in

db

Returns

Defined in

genesisBlock

Returns

Defined in

provider

Returns