Pure-Evm

A browser and node compatible EVM interpreter for pure function calls compiled to WebAssembly.

Usage

npm install pure-evm

The interface pure_evm.exec() takes in a contract's bytecode along with a transaction's data field and returns a Uint8Array of the resultant transaction output. Note that the bytecode should be the bytecode stored onchain, i.e., not the initcode. data is simply the data field of the transaction to invoke the pure function, i.e., the method's sighash followed by abi encoded arguments.

Browser

Because pure-evm is loaded as a WebAssembly module in browser, it must be loaded asynchronously.

For example,

import('pure-evm').then((pure_evm) => {

  let output = pure_evm.exec(bytecode(), data())

  console.log(output);
});

/**
 * Deployed bytecode *not* the initcode for the following contract.
 *
 * pragma solidity ^0.5.0;
 * contract AddThree {
 *   function addThree(uint256 a) public pure returns (uint256) {
 *     return a + 3;
 *     }
 * }
 */
function bytecode() {
  let bytecode = '608060405260043610603f576000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff16806308316796146044575b600080fd5b348015604f57600080fd5b50607960048036036020811015606457600080fd5b8101908080359060200190929190505050608f565b6040518082815260200191505060405180910390f35b600060038201905091905056fea165627a7a723058200e912ad05dca5252a91d1ce28dda0451a49092178c344ac1a40ccf9c9d5d46150029';
  return Uint8Array.from(Buffer.from(bytecode, 'hex'));
}

/**
 * Data field for transaction to `addThree` function with a = 4.
 */
function data() {
  let data = '083167960000000000000000000000000000000000000000000000000000000000000004';
  return Uint8Array.from(Buffer.from(data, 'hex'));
}

Node

In node environments, pure-evm can be used in a similar way.

const pure_evm = require('pure-evm');
...

See the examples here.