Ethereum smart contract transaction input data decoder

npm install @arcblock/abi-decoder

Pass ABI file path to decoder constructor:

const Decoder = require('@arcblock/abi-decoder');
const decoder = new Decoder(`${__dirname}/abi.json`);

Alternatively, you can pass ABI array object to constructor;

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

example abi

Then you can decode input data:

const data = `0x67043cae0000000000000000000000005a9dac9315fdd1c3d13ef8af7fdfeb522db08f020000000000000000000000000000000000000000000000000000000058a20230000000000000000000000000000000000000000000000000000000000040293400000000000000000000000000000000000000000000000000000000000000a0f3df64775a2dfb6bc9e09dced96d0816ff5055bf95da13ce5b6c3f53b97071c800000000000000000000000000000000000000000000000000000000000000034254430000000000000000000000000000000000000000000000000000000000`;

const result = decoder.decodeData(data);

console.log(result);

{
  "method": "registerOffChainDonation",
  "types": [
    "address",
    "uint256",
    "uint256",
    "string",
    "bytes32"
    ],
    "inputs": [
      <BN: 5a9dac9315fdd1c3d13ef8af7fdfeb522db08f02>,
      <BN: 58a20230>,
      <BN: 402934>,
      "BTC",
      <Buffer f3 df ... 71 c8>
    ],
    "names": [
      "addr",
      "timestamp",
      "chfCents",
      "currency",
      "memo"
    ]
}

Example using input response from web3.getTransaction:

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

Where OrderData is

struct OrderData {
  uint256 amount;
  address buyer;
}

Decoding input to a method someMethod(address,OrderData,OrderData[]) returns data in format

{
  method: 'someMethod',
  types: ['address', '(uint256,address)', '(uint256,address)[]'],
  inputs: [
    '0x81c55017F7Ce6E72451cEd49FF7bAB1e3DF64d0C',
    [100, '0xA37dE6790861B5541b0dAa7d0C0e651F44c6f4D9']
    [[274, '0xea674fdde714fd979de3edf0f56aa9716b898ec8']]
  ],
  names: ['sender', ['order', ['amount', 'buyer']], ['allOrders', ['amount', 'buyer']]]
}

• In the types field, tuples are represented as a string containing types contained in the tuple
• In the inputs field, tuples are represented as an array containing values contained in the tuple
• In the names field, tuples are represented as an array with 2 items. Item 1 is the name of the tuple, item 2 is an array containing the names of the values contained in the tuple.

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!

npm install -g @arcblock/abi-decoder

$ ethereum_input_data_decoder --help

  Ethereum smart contract transaction input data decoder

  Usage
    $ ethereum_input_data_decoder [flags] [input]

  Options
    --abi, -a  ABI file path
    --input, -i Input data file path

  Examples
    $ ethereum_input_data_decoder --abi token.abi --input data.txt
    $ ethereum_input_data_decoder --abi token.abi "0x23b872dd..."

Pass ABI file and input data as file:

$ ethereum_input_data_decoder --abi abi.json --input data.tx

method   registerOffChainDonation

address  addr       0x5a9dac9315fdd1c3d13ef8af7fdfeb522db08f02
uint256  timestamp  1487012400
uint256  chfCents   4204852
string   currency   BTC
bytes32  memo       0xf3df64775a2dfb6bc9e09dced96d0816ff5055bf95da13ce5b6c3f53b97071c8

Pass ABI file and input data as string:

$ ethereum_input_data_decoder --abi abi.json 0x67043cae0...000000

method   registerOffChainDonation

address  addr       0x5a9dac9315fdd1c3d13ef8af7fdfeb522db08f02
uint256  timestamp  1487012400
uint256  chfCents   4204852
string   currency   BTC
bytes32  memo       0xf3df64775a2dfb6bc9e09dced96d0816ff5055bf95da13ce5b6c3f53b97071c8

You can also pipe the input data:

$ cat data.txt | ethereum_input_data_decoder --abi abi.json

method   registerOffChainDonation

address  addr       0x5a9dac9315fdd1c3d13ef8af7fdfeb522db08f02
uint256  timestamp  1487012400
uint256  chfCents   4204852
string   currency   BTC
bytes32  memo       0xf3df64775a2dfb6bc9e09dced96d0816ff5055bf95da13ce5b6c3f53b97071c8

npm test

1. Clone repository:

git clone [email protected]:miguelmota/@arcblock/abi-decoder.git

cd @arcblock/abi-decoder/

2. Install dependencies:

npm install

3. Make changes.

4. Run tests:

npm test

5. Run linter:

npm run lint

Pull requests are welcome!

For contributions please create a new branch and submit a pull request for review.

Many thanks to all the contributors for making this a better library for everyone 🙏

• 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.

• Q: Does this library support ABIEncoderV2?

  • A: Yes, but it's buggy. Please submit a bug report if you encounter issues.

MIT