Ethereum smart contract transaction input data decoder

Demo

https://lab.miguelmota.com/ethereum-input-data-decoder

Install

npm install ethereum-input-data-decoder

Usage

Pass ABI file path to decoder constructor:

const InputDataDecoder = require('ethereum-input-data-decoder');
const decoder = new InputDataDecoder(`${__dirname}/abi.json`);

Alternatively, you can pass ABI array object to constructor;

const abi = [{ ... }]
const decoder = new InputDataDecoder(abi);

example abi

Then you can decode input data:

const data = `0x67043cae0000000000000000000000005a9dac9315fdd1c3d13ef8af7fdfeb522db08f020000000000000000000000000000000000000000000000000000000058a20230000000000000000000000000000000000000000000000000000000000040293400000000000000000000000000000000000000000000000000000000000000a0f3df64775a2dfb6bc9e09dced96d0816ff5055bf95da13ce5b6c3f53b97071c800000000000000000000000000000000000000000000000000000000000000034254430000000000000000000000000000000000000000000000000000000000`;

const result = decoder.decodeData(data);

console.log(result);

{
  "name": "registerOffChainDonation",
  "types": [
    "address",
    "uint256",
    "uint256",
    "string",
    "bytes32"
    ],
    "inputs": [
      <BN: 5a9dac9315fdd1c3d13ef8af7fdfeb522db08f02>,
      <BN: 58a20230>,
      <BN: 402934>,
      "BTC",
      <Buffer f3 df ... 71 c8>
    ]
}

Example using input response from web3.getTransaction:

web3.eth.getTransaction(txHash, (error, txResult) => {
  const result = decoder.decodeData(txResult.input);
  console.log(result);
});

Decoding Big Numbers

All numbers are returned in big number format to preserve precision.

Here's an example of how to convert the big number to a human readable format.

console.log(result.inputs[0].toString(10)) // "5"
console.log(result.inputs[0].toNumber()) // 55

Please keep in mind that JavaScript only supports numbers up to 64 bits. Solidity numbers can be up to 256 bits, so you run the risk of truncation when casting or having the big number library error out when trying to parse a large number to a JavaScript Number type.

const n = new BN("543534254523452352345234523455")
console.log(n.toString(10)) // "543534254523452352345234523455"
console.log(n.toNumber()) // ERROR!

Test

npm test

FAQ

• Q: How can I retrieve the ABI?

  • A: You can generate the ABI from the solidity source files using the Solidity Compiler.

    solc --abi MyContract.sol -o build

• Q: Can this library decode contract creation input data?

  • A: Yes, it can decode contract creation input data.

License

MIT