Using Remix IDE

📜 TL;DR:

  • In this section, we’ll deploy a small contract in Remix IDE with a single method which calls the Bitcoin Balance precompile and returns the balance as a uint256.

  • Ensure to use Solidity version 0.8.19 or earlier for compatibility with the Hemi testnet environment.


🏁 Prerequisites

  • To follow along, you’ll need:

    • Metamask (or another Remix-supported web wallet) connected to Hemi testnet as a custom network;

    • A nonzero ETH balance tunneled over to a Hemi address in your wallet you want to deploy the demo contract with to pay deployment gas fees.


📚 Tutorial

1. Create Contract

  • To start, open Remix, delete any existing contracts in the “contracts” folder,.

  • Create a new contract file, which for our example we’ll call “BitcoinBalDemo.sol”.

  • Paste in the following code:

pragma solidity ^0.8.0;

contract BitcoinBalDemo {
    function getBitcoinAddressBalance(string calldata btcAddress) public view returns (uint256 balance) {
    bytes memory converted = bytes(btcAddress);
    (bool ok, bytes memory out) = address(0x40).staticcall(converted);
    require(ok, "Failed to Call Bitcoin Balance hVM Precompile (0x40)");
    
    return uint64(bytes8(out));
  }
}

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