Chainsaw

Chainsaw

Chainsaw is ethereum based log extracting and log decoding library with a periodic polling feature.

Usage of Chainsaw .

1. Build Chainsaw :

Run the below command in the chainsaw directory .

npm run build

2. Importing the chainsaw :

For non babel transpiled es6 :

const Chainsaw = require('../build/chainsaw.js').Chainsaw

if your server is a es6 babel transpiled file , import in the following way:

import { Chainsaw } from '../lib/chainsaw.js'

3. Instantiating chainsaw, initializing with web3 provider and deployed contract address :

const Web3 = require('web3')
const web3 = new Web3(new Web3.providers.HttpProvider('http://localhost:8545'))
// web3 , list of contract address
const chainsaw = new Chainsaw(web3, [List of contract address])

// Add abi of your contracts to chainsaw,so chainsaw is able to decode the logs.
chainsaw.addABI(testContract.abi) 

4. Event callback and Turn On Chainsaw Polling :

Define event callback .

// Chainsaw event callback functions
const eventCallBack = (error, eventData) => {
  if (!error && eventData.length > 0) {
    console.log('Chainsaw eventCallBack', eventData)
  }
}

Turn on Polling in the following way :

// Chainsaw turn on polling to listen to events
chainsaw.turnOnPolling(eventCallBack)

6. Complete Working Example of Usage :

// Importing Chainsaw
const Chainsaw = require('../build/chainsaw.js').Chainsaw
const setup = require('../build/setup.js')

const Web3 = require('web3')
const app = require('express')()

const web3 = new Web3(new Web3.providers.HttpProvider('http://localhost:8545'))

// Chainsaw event callback functions
const eventCallBack = (error, eventData) => {
  if (!error && eventData.length > 0) {
    console.log('Chainsaw eventCallBack', eventData)
  }
}

const initChainsaw = async () => {
  // Following deploys a test contract. Its responsibility
  // of the client of chainsaw to deploy their respective contracts.
  // Chainsaw does not have configs , it only has initializaiton
  // parameters when you instantiate a class .
  const testContract = await setup.default({
    testRPCProvider: 'http://localhost:8545/'
  })

  // Initialize with web3 provider and contract address to watch.
  const chainsaw = new Chainsaw(web3, [testContract.address])

  // Add abi of the contract to chainsaw.
  chainsaw.addABI(testContract.abi)

  // Chainsaw turn on polling to listen to events
  chainsaw.turnOnPolling(eventCallBack)

  // Now call your contract methods to receive event data
  // in the callback. Following is just a test example
  await testContract.deposit('0xabc', {value: 20} )
}

initChainsaw()

app.listen(3000, function () {
  console.log('Chainsaw Example Usage ')
})

Other Implemented Methods:

Get undecoded logs by block number:

Function:

/**
  ** Given the blocknumber return the array of logs for each transaction.
  ** blockNumber -> Block: [ txHash1, txHash2] -> Logs: [logs1, logs2]
  **/
  getLogsByBlockNumber (blockNumber)

Example Usage :

chainsaw.getLogsByBlockNumber(web3.eth.blockNumber)

Get decoded logs by block rannge:

Function:

/**
  ** Given an startBlock and endBlock range, decoded logs are returned.
  ** Params -
  **  startBlock: Starting block to read the block. (default: latest block)
  **  endBlock: End block to read the block.(default: latest block)
  **/
  getLogs (startBlock = this.eth.blockNumber, endBlock = this.eth.blockNumber)

Example Usage : Reads from block 100 to latestBlock .

chainsaw.getLogsByBlockNumber(100, web3.eth.blockNumber)