iota.js persistence inteface
npm install @iota/persistencePersistence module allows to persist a state of last key index, bundles and CDAs*.
Access to a database is done with adapters that implement the PersistenceAdapter interface. An implementation of it is @iota/persistence-adapter-level which uses an :abstract-level store (leveldown, leveljs, memdown or others...).
* CDAs = Conditional Deposit Adresses
JS
import { persistence, persistenceID } from '@iota/persistence'
import { createPersistenceAdapter } from '@iota/persistence-adapter-level'
import leveldown from 'leveldown';(async function (seed) {
const adapter = persistenceAdapter({
persistenceID: persistenceID(seed),
persistencePath: './test/temp', // test directory
store: leveldown // default store
})
try {
const {
nextIndex,
writeBundle,
deleteBundle,
writeCDA,
deleteCDA,
batch,
state.read,
createStateReadStream,
history.read,
history.delete,
createHistoryReadStream,
} = await persistence(adapter)
return nextIndex()
} catch (error) {
// deal with errors here...
return error
}
})('SOME9SEED') // Shoud output 1
`
PersistenceAdapter interface
TS
export interface PersistenceAdapter {
readonly read: (key: K) => Promise
readonly write: (key: K, value: V) => Promise
readonly delete: (key: K) => Promise
readonly batch: (ops: ReadonlyArray>) => Promise
readonly createReadStream: (options?: PersistenceIteratorOptions) => NodeJS.ReadableStream
}
`
$3
reads & streams persisted bundles & CDAs as key-value pairs.
`JS
import { CDA_LENGTH, deserializeCDA } from '@iota/cda'
import { isMultipleOfTransactionLength } from '@iota/transaction'createReadStream
.on('data', value => {
if (value.length === CDA_LENGTH) {
// It's a CDA
const {
address,
timeoutAt,
expectedBalance,
checksum,
index,
security,
} = deserializeCDA(value)
} else if (isMultipleOfTransactionLength(value)) {
// It's a bundle
const bundle = transaction.bundle(value)
}
})
.on('error', error => {
// handle errors here
})
.on('close', () => {})
.on('end', () => {})
`
Persistence Events
Persistence module emits events after every sucessful modification of the state.JS
persistence.on('writeBundle', bundle => {})
persistence.on('deleteBundle', bundle => {})
persistence.on('writeCDA', cda => {})
persistence.on('deleteCDA', cda => {})
``