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.

• We recommend you use Solidity version 0.8.25 or later, but previous versions are also expected to work.

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🏁 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.

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📚 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 ^0.8.25;

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));
  }
}

You can now compile and deploy this contract, and try out calling it with a Bitcoin address string to see the address's balance (in satoshis) returned by hVM.