Convert transaction log hash to readable format

Question

I am trying to convert transaction logs in text (human readable format) tried 2 methods

1. using web3.toAscii(receipt.logs[0].topics[0])

2.Using coder.js according to this answer

While using 2nd method I get error :

Cannot find module 'file:///C:/Users/user1/node_modules/web3/lib/solidity/coder.js'

Path where my coder.js file resides C:/Users/user1/node_modules/web3/lib/solidity/coder.js

Is there any other way to parse the transaction log and get the data in human readable format.

code used to access coder.js

var SolidityCoder = require('file:///C:/Users/user1/node_modules/web3/lib/solidity/coder.js');

also tried

var SolidityCoder = require('C:\\Users\\user1\\node_modules\\web3\\lib\\solidity\\coder.js');

Answer 1

Using web3.toAscii

That function is not what you're looking for, at least not for topics[0] of a log entry. The first entry in the "topics" array is the signature of what type of log entry it is. So it's a hash, and won't resolve to anything useful just converting it to ASCII.

If you already have the ABI of a contract, which includes the definition of the Events it uses, then you can calculate the hash that the log entry uses:

let events = [
  {
    type: 'event',
    name: 'HelloWorld',
    anonymous: false,
    inputs: [{"indexed":false,"name":"call_address","type":"address"}]
  },
  // List out all the events you care about
];

function getEventSignature(eventAbi) {
  var signature = eventAbi.name + '(' + eventAbi.inputs.map(function(input) { return input.type; }).join(',') + ')';
  var hash = web3.sha3(signature);
  return {
    signature: signature,
    hash: hash,
    abi: eventAbi
  };
}

var topicMap = {};
events.map(eventAbi => {
  var signature = getEventSignature(eventAbi);
  topicMap[signature.hash] = signature;
});
console.log(topicMap);

If you only have the log's topic[0] value, you cannot go backwards from that to figure out the Event's name, since it is a hash (which by its definition is only one-way).

That other question references the coder.js library as a way to parse the data of the log entry, which is different than its topics.