Correctly address Smart Contract storage address using web3js 1.0.0 library functions

Question

A short while ago, I found a fantastic Medium article explaining Smart Contract storage.

The examples in this article have helped me to understand how to read a Smart Contract's storage values from the command line / console.

However, with the version 1.0.0 of web3js going into Beta - and the NPM version of web3js being installed by default being the 1.0.0 Beta version, I thought that I would upgrade my code using the information from the aforementioned article to the new library.

The problem is that I can't replicate the same behavior of web3.sha3 using the new version of the library; web3Utils.sha3.

To clarify, here are some examples - starting with the output that I get from the stable, but pre-V1.0.0 web3.sha3 function and then from the new, Beta version of the web3js library:

To give you some context, the test is based on accessing the mappings data in this contrived Smart Contract:

pragma solidity ^0.4.0;

contract StorageTest {
    mapping(address => uint256) public storedData;

    function addDataToMapping(address account, uint256 amount) public {
        storedData[account] = amount;
    }
}

The way that I determine how to access the mapping's data for the address 0x90F8bf6A479f320ead074411a4B0e7944Ea8c9C1 is by using the following pre-V1.0.0 web3js call:

web3.sha3("00000000000000000000000x90F8bf6A479f320ead074411a4B0e7944Ea8c9C10000000000000000000000000000000000000000000000000000000000000000", {"encoding":"hex"})

This results in the hash value

0xbbf27a261d686d37ad5c6299e09a73a2a829c9c10eaf9c5c19e6ff2488e52f20

Now, if we simply port this over to the V1.0.0 library then the code looks like this:

web3Utils.sha3("00000000000000000000000x90F8bf6A479f320ead074411a4B0e7944Ea8c9C10000000000000000000000000000000000000000000000000000000000000000", {"encoding":"hex"})   

However, this results in the following (different) hash being output:

0x02d38ce98b8dae9d7cc32b64bb52580b4989cb56d07114b95037da4af5f500cf

I tried removing the {"encoding":"hex"} parameter (because this isn't mentioned in the documentation:

web3Utils.sha3("00000000000000000000000x90F8bf6A479f320ead074411a4B0e7944Ea8c9C10000000000000000000000000000000000000000000000000000000000000000")

But unfortunately, I still get the same output:

0x02d38ce98b8dae9d7cc32b64bb52580b4989cb56d07114b95037da4af5f500cf

The documentation mentions a web3Utils.soliditySha3 function that sounded like it might do the trick, so I switched this function call in instead:

web3Utils.soliditySha3("00000000000000000000000x90F8bf6A479f320ead074411a4B0e7944Ea8c9C10000000000000000000000000000000000000000000000000000000000000000", {"encoding":"hex"})

This time I got a different value, but it is not the one that I am looking for:

0x0780d226e6d7ac5576d20e78b8c3a2122ace468d419adefef1e79c49d7f4116f

I also tried removing the {"encoding":"hex"} parameter (because this also isn't mentioned in the documentation:

web3Utils.soliditySha3("00000000000000000000000x90F8bf6A479f320ead074411a4B0e7944Ea8c9C10000000000000000000000000000000000000000000000000000000000000000");

But this just results in the same, incorrect, value as the web3Utils.sha3 function calls:

0x02d38ce98b8dae9d7cc32b64bb52580b4989cb56d07114b95037da4af5f500cf

I have also tried various permutations of the "Any type, or an object with {type: 'uint', value: '123456'}" parameter format:

web3Utils.soliditySha3({type: 'string', value: "00000000000000000000000x90F8bf6A479f320ead074411a4B0e7944Ea8c9C10000000000000000000000000000000000000000000000000000000000000000"})

And yet I still can't get the correct value.

Does anyone know how to correctly address a mapping or struct storage address using the latest web3js library functions?

Answer 1

Removing the extra 'x' in the key and prefixing with '0x' it returns the same value in

const Web3 = require('web3')
const web3 = new Web3();

const index = "0000000000000000000000000000000000000000000000000000000000000000"
const key =   "00000000000000000000000090F8bf6A479f320ead074411a4B0e7944Ea8c9C1";
const newKey =  web3.utils.sha3("0x" + key + index)
console.log(newKey)

0xbbf27a261d686d37ad5c6299e09a73a2a829c9c10eaf9c5c19e6ff2488e52f20