Contract Source Code:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "./interfaces/IBRC20Factory.sol";
contract BRC20 {
string public name;
string public symbol;
uint8 public immutable decimals;
address public immutable factory;
uint256 public totalSupply;
mapping (address => uint256) public balanceOf;
mapping (address => mapping(address => uint256)) public allowance;
mapping (address => uint256) public nonces;
bytes32 public DOMAIN_SEPARATOR;
bytes32 public constant PERMIT_TYPEHASH = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
bytes32 public constant DOMAIN_TYPEHASH = keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)");
event Approval(address indexed owner, address indexed spender, uint256 value);
event Transfer(address indexed from, address indexed to, uint256 value);
constructor() {
(name, symbol, decimals) = IBRC20Factory(msg.sender).parameters();
factory = msg.sender;
uint256 chainId;
assembly {
chainId := chainid()
}
DOMAIN_SEPARATOR = keccak256(abi.encode(DOMAIN_TYPEHASH, keccak256(bytes(name)), keccak256(bytes('1')), chainId, address(this)));
}
function mint(address to, uint256 amount) external {
require(msg.sender == factory, "unauthorized");
_mint(to, amount);
}
function burn(uint256 amount) external {
require(msg.sender == factory, "unauthorized");
_burn(msg.sender, amount);
}
function approve(address spender, uint256 amount) external returns (bool) {
allowance[msg.sender][spender] = amount;
emit Approval(msg.sender, spender, amount);
return true;
}
function transfer(address to, uint256 amount) external returns (bool) {
balanceOf[msg.sender] -= amount;
unchecked {
balanceOf[to] += amount;
}
emit Transfer(msg.sender, to, amount);
return true;
}
function transferFrom(address from, address to, uint256 amount) external returns (bool) {
uint256 allowed = allowance[from][msg.sender];
if (allowed != type(uint256).max) allowance[from][msg.sender] = allowed - amount;
balanceOf[from] -= amount;
unchecked {
balanceOf[to] += amount;
}
emit Transfer(from, to, amount);
return true;
}
function permit(address owner, address spender, uint256 value, uint256 deadline, uint8 v, bytes32 r, bytes32 s) external {
require(deadline >= block.timestamp, 'EXPIRED');
unchecked {
bytes32 digest = keccak256(
abi.encodePacked(
'\x19\x01',
DOMAIN_SEPARATOR,
keccak256(abi.encode(PERMIT_TYPEHASH, owner, spender, value, nonces[owner]++, deadline))
)
);
address recoveredAddress = ecrecover(digest, v, r, s);
require(recoveredAddress != address(0) && recoveredAddress == owner, 'INVALID_SIGNATURE');
allowance[recoveredAddress][spender] = value;
}
emit Approval(owner, spender, value);
}
function _mint(address to, uint256 amount) internal {
totalSupply += amount;
unchecked {
balanceOf[to] += amount;
}
emit Transfer(address(0), to, amount);
}
function _burn(address from, uint256 amount) internal {
balanceOf[from] -= amount;
unchecked {
totalSupply -= amount;
}
emit Transfer(from, address(0), amount);
}
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
interface IBRC20Factory {
function parameters() external view returns (string memory name, string memory symbol, uint8 decimals);
}