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Feed lists

Purpose

Feed lists are list-like data structures and APIs built on top of raw Swarm feeds.

Installation

npm install @erebos/feed-list

The various feed list classes must be injected a BzzFeed instance, so @erebos/bzz-feed must also be installed alongside.

Usage

Chunk lists

Feed chunks have a maximum size of 3963 bytes (4KB minus headers and signature)

import { BzzFeed } from '@erebos/bzz-feed'
import { BzzNode } from '@erebos/bzz-node'
import { ChunkListReader, ChunkListWriter } from '@erebos/feed-list'
import { pubKeyToAddress } from '@erebos/keccak256'
import { createKeyPair, sign } from '@erebos/secp256k1'

// This setup is meant for demonstration purpose only - keys and signatures security must be handled by the application
const keyPair = createKeyPair()
const signBytes = async bytes => sign(bytes, keyPair)
const bzz = new BzzNode({ url: 'http://localhost:8500' })
const bzzFeed = new BzzFeed({ bzz, signBytes })

const aliceAddress = pubKeyToAddress(keyPair.getPublic('array'))
const aliceWriter = new ChunkListWriter({
  bzz: bzzFeed,
  feed: { user: aliceAddress, name: 'alice-bob' },
})
await aliceWriter.push('one')
await aliceWriter.push('two')

const feed = aliceWriter.getID()
const bobReader = new ChunkListReader({ bzz: bzzFeed, feed })
const chunk = await bobReader.load(1)
const text = chunk.toString() // 'two'

Data lists

Data lists store entries in JSON files and reference them in feed chunks

import { BzzFeed } from '@erebos/bzz-feed'
import { BzzNode } from '@erebos/bzz-node'
import { DataListReader, DataListWriter } from '@erebos/feed-list'
import { pubKeyToAddress } from '@erebos/keccak256'
import { createKeyPair, sign } from '@erebos/secp256k1'

// This setup is meant for demonstration purpose only - keys and signatures security must be handled by the application
const keyPair = createKeyPair()
const signBytes = async bytes => sign(bytes, keyPair)
const bzz = new BzzNode({ url: 'http://localhost:8500' })
const bzzFeed = new BzzFeed({ bzz, signBytes })

const aliceAddress = pubKeyToAddress(keyPair.getPublic('array'))
const aliceWriter = new DataListWriter({
  bzz: bzzFeed,
  feed: { user: aliceAddress, name: 'alice-bob' },
})
await aliceWriter.push({ hello: 'world' })
await aliceWriter.push({ hello: 'Bob' })

const feed = aliceWriter.getID()
const bobReader = new DataListReader({ bzz: bzzFeed, feed })
const data = await bobReader.load(1) // { hello: 'Bob' }

Interfaces and types

Hex

Hex class instance as exported by the @erebos/hex package.

ForwardsChunkIterator

interface ForwardsChunkIterator<T> extends AsyncIterator<T> {
  length: number
}

ListReaderConfig

The BzzFeed class, FeedID class, FeedParams are exported by the @erebos/bzz-feed package.

The and FetchOptions interface is exported by the @erebos/bzz package.

export interface ListReaderConfig<
  B extends BzzFeed<any,  Response<any> = BzzFeed<any,  Response<any>
> {
  bzz: B
  feed: FeedID | FeedParams
  fetchOptions?: FetchOptions
}

ListWriterConfig

Extends ListReaderConfig

export interface ListWriterConfig<
  B extends BzzFeed<any,  Response<any> = BzzFeed<any,  Response<any>
> extends ListReaderConfig<B> {
  signParams?: any
}

ChunkListReader class

new ChunkListReader()

Arguments

  1. config: ListReaderConfig

.load()

Arguments

  1. index: number

Returns Hex | null

.createBackwardsIterator()

Arguments

  1. maxIndex: number
  2. minIndex?: number = 0

Returns AsyncIterator<Hex | null>

.createForwardsIterator()

Arguments

  1. minIndex?: number = 0
  2. maxIndex?: number

Returns ForwardsChunkIterator<Hex>

ChunkListWriter class

Extends ChunkListReader

new ChunkListWriter()

Arguments

  1. config: ListWriterConfig

.length

Returns number

.getID()

Returns FeedID

.push()

Arguments

  1. data: hexInput

Returns Promise<void>

DataListReader class

Types

  • T = any: the type of the list data

new DataListReader()

Arguments

  1. config: ListReaderConfig

.load()

Arguments

  1. index: number

Returns T

.createBackwardsIterator()

Arguments

  1. maxIndex: number
  2. minIndex?: number = 0

Returns AsyncIterator<T | null>

.createForwardsIterator()

Arguments

  1. minIndex?: number = 0
  2. maxIndex?: number

Returns ForwardsChunkIterator<T>

DataListWriter class

Extends DataListReader

Types

  • T = any: the type of the list data

new DataListWriter()

Arguments

  1. config: ListWriterConfig

.length

Returns number

.getID()

Returns FeedID

.push()

Arguments

  1. data: T

Returns Promise<void>

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