Comment on page
Tokens (BTC-20)
The BTC-20 token standard on Bitcoin is similar to ERC-20 on Ethereum. It can represent virtually anything in Bitcoin:
- a cryptocurrency a share in a company voting rights in a DAO a fiat currency like USD an ounce of gold loyalty points and more
Write a BTC-20 smart contract
Extending the OpenZeppelin ERC-20 contract, we can create a governance token (BIT) for a hypothetical DEX (Bitswap) on Bitcoin.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
contract Bitswap is ERC20 {
constructor(uint256 initialSupply) ERC20("Bitswap", "BIT") {
_mint(msg.sender, initialSupply);
}
}
Clone the smart contract examples
We've prepared a few different examples for you to get started.
git clone https://github.com/bitcoinevm/smart-contract-examples.git
Compile the contracts
To compile your contracts, use the built-in hardhat compile task.
cd smart-contract-examples
npm install
npx hardhat compile
Deploy the contracts
Review config file hardhat.config.ts. The network configs should look like this.
networks: {
mynw: {
url: "http://localhost:10002",
accounts: {
mnemonic: "<your mnemonic with funds>"
},
timeout: 100_000,
},
blockscoutVerify: {
blockscoutURL: "http://localhost:4000", // your explorer URL
...
}
}
Run the deploy scripts using hardhat-deploy.
npx hardhat deploy --tags ERC20
Make sure the accounts in hardhat.config.ts have some BTC.
Interact with the contracts
Once the contracts are deployed, you can interact with them. We've prepared a few hardhat tasks to make it easy for you to interact with the contracts.
npx hardhat balanceERC20
npx hardhat transferERC20 --from <your-address> --amount 0.1 --to <your-address>
//// SPDX-License-Identifier: MIT
// Contract by Bitcoin EVM.
pragma solidity ^0.4.23;
contract owned {
address public owner;
constructor() public {
owner = msg.sender;
}
modifier onlyOwner {
require(msg.sender == owner);
_;
}
function transferOwnership(address newOwner) onlyOwner public {
owner = newOwner;
}
}
interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; }
contract TokenERC20 {
string public name;
string public symbol;
uint8 public decimals = 18;
uint256 public totalSupply;
mapping (address => uint256) public balanceOf;
mapping (address => mapping (address => uint256)) public allowance;
event Transfer(address indexed from, address indexed to, uint256 value);
event Approval(address indexed _owner, address indexed _spender, uint256 _value);
event Burn(address indexed from, uint256 value);
constructor(
uint256 initialSupply,
string tokenName,
string tokenSymbol
) public {
totalSupply = initialSupply * 10 ** uint256(decimals);
balanceOf[msg.sender] = totalSupply;
name = tokenName;
symbol = tokenSymbol;
}
function _transfer(address _from, address _to, uint _value) internal {
require(_to != 0x0);
require(balanceOf[_from] >= _value);
require(balanceOf[_to] + _value > balanceOf[_to]);
uint previousBalances = balanceOf[_from] + balanceOf[_to];
balanceOf[_from] -= _value;
balanceOf[_to] += _value;
emit Transfer(_from, _to, _value);
assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
}
function transfer(address _to, uint256 _value) public returns (bool success) {
_transfer(msg.sender, _to, _value);
return true;
}
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
require(_value <= allowance[_from][msg.sender]);
allowance[_from][msg.sender] -= _value;
_transfer(_from, _to, _value);
return true;
}
function approve(address _spender, uint256 _value) public
returns (bool success) {
allowance[msg.sender][_spender] = _value;
emit Approval(msg.sender, _spender, _value);
return true;
}
function approveAndCall(address _spender, uint256 _value, bytes _extraData)
public
returns (bool success) {
tokenRecipient spender = tokenRecipient(_spender);
if (approve(_spender, _value)) {
spender.receiveApproval(msg.sender, _value, this, _extraData);
return true;
}
}
function burn(uint256 _value) public returns (bool success) {
require(balanceOf[msg.sender] >= _value);
balanceOf[msg.sender] -= _value;
totalSupply -= _value;
emit Burn(msg.sender, _value);
return true;
}
function burnFrom(address _from, uint256 _value) public returns (bool success) {
require(balanceOf[_from] >= _value);
require(_value <= allowance[_from][msg.sender]);
balanceOf[_from] -= _value;
allowance[_from][msg.sender] -= _value;
totalSupply -= _value;
emit Burn(_from, _value);
return true;
}
}
contract ERC20Token is owned, TokenERC20 {
uint256 public sellPrice;
uint256 public buyPrice;
mapping (address => bool) public frozenAccount;
event FrozenFunds(address target, bool frozen);
constructor(
uint256 initialSupply,
string tokenName,
string tokenSymbol
) TokenERC20(initialSupply, tokenName, tokenSymbol) public {}
function _transfer(address _from, address _to, uint _value) internal {
require (_to != 0x0);
require (balanceOf[_from] >= _value);
require (balanceOf[_to] + _value >= balanceOf[_to]);
require(!frozenAccount[_from]);
require(!frozenAccount[_to]);
balanceOf[_from] -= _value;
balanceOf[_to] += _value;
emit Transfer(_from, _to, _value);
}
function mintToken(address target, uint256 mintedAmount) onlyOwner public {
balanceOf[target] += mintedAmount;
totalSupply += mintedAmount;
emit Transfer(0, this, mintedAmount);
emit Transfer(this, target, mintedAmount);
}
function freezeAccount(address target, bool freeze) onlyOwner public {
frozenAccount[target] = freeze;
emit FrozenFunds(target, freeze);
}
function setPrices(uint256 newSellPrice, uint256 newBuyPrice) onlyOwner public {
sellPrice = newSellPrice;
buyPrice = newBuyPrice;
}
function buy() payable public {
uint amount = msg.value / buyPrice;
_transfer(this, msg.sender, amount);
}
function sell(uint256 amount) public {
address myAddress = this;
require(myAddress.balance >= amount * sellPrice);
_transfer(msg.sender, this, amount);
msg.sender.transfer(amount * sellPrice);
}
}
Last modified 7mo ago