go-ethereum/contracts/trc21issuer/contract/TRC21.sol

pragma solidity ^0.4.24;
import "./libs/SafeMath.sol";

/**
 * @title TRC21 interface
 */
interface ITRC21 {
	function totalSupply() external view returns (uint256);

	function balanceOf(address who) external view returns (uint256);

	function estimateFee(uint256 value) external view returns (uint256);

	function allowance(address owner, address spender) external view returns (uint256);

	function transfer(address to, uint256 value) external returns (bool);

	function approve(address spender, uint256 value) external returns (bool);

	function transferFrom(address from, address to, uint256 value) external returns (bool);

	event Transfer(address indexed from, address indexed to, uint256 value);

	event Approval(address indexed owner, address indexed spender, uint256 value);

	event Fee(address indexed from, address indexed to, address indexed issuer, uint256 value);
}

/**
 * @title Standard TRC21 token
 * @dev Implementation of the basic standard token.
 */
contract TRC21 is ITRC21 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;
    uint256 private _minFee;
    address private _issuer;
    mapping (address => mapping (address => uint256)) private _allowed;
    uint256 private _totalSupply;

    /**
     * @dev Total number of tokens in existence
     */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev  The amount fee that will be lost when transferring.
     */
    function minFee() public view returns (uint256) {
        return _minFee;
    }

    /**
     * @dev token's foundation
     */
    function issuer() public view returns (address) {
        return _issuer;
    }

    /**
     * @dev Gets the balance of the specified address.
     * @param owner The address to query the balance of.
     * @return An uint256 representing the amount owned by the passed address.
     */
    function balanceOf(address owner) public view returns (uint256) {
        return _balances[owner];
    }

    /**
     * @dev Estimate transaction fee.
     * @param value amount tokens sent
     */
    function estimateFee(uint256 value) public view returns (uint256) {
        return value.mul(0).add(_minFee);
    }

    /**
     * @dev Function to check the amount of tokens that an owner allowed to a spender.
     * @param owner address The address which owns the funds.
     * @param spender address The address which will spend the funds.
     * @return A uint256 specifying the amount of tokens still available for the spender.
     */
    function allowance(address owner,address spender) public	view returns (uint256){
        return _allowed[owner][spender];
    }

    /**
     * @dev Transfer token for a specified address
     * @param to The address to transfer to.
     * @param value The amount to be transferred.
     */
    function transfer(address to, uint256 value) public returns (bool) {
        uint256 total = value.add(_minFee);
        require(to != address(0));
        require(value <= total);
        _transfer(msg.sender, to, value);
        _transfer(msg.sender, _issuer, _minFee);
        emit Fee(msg.sender, to, _issuer, _minFee);
        return true;
    }

    /**
     * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
     * Beware that changing an allowance with this method brings the risk that someone may use both the old
     * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
     * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     * @param spender The address which will spend the funds.
     * @param value The amount of tokens to be spent.
     */
    function approve(address spender, uint256 value) public returns (bool) {
        require(spender != address(0));
        require(_balances[msg.sender]>=_minFee);
        _allowed[msg.sender][spender] = value;
        _transfer(msg.sender, _issuer, _minFee);
        emit Approval(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev Transfer tokens from one address to another
     * @param from address The address which you want to send tokens from
     * @param to address The address which you want to transfer to
     * @param value uint256 the amount of tokens to be transferred
     */
    function transferFrom(address from,	address to,	uint256 value)	public returns (bool) {
        uint256 total = value.add(_minFee);
        require(to != address(0));
        require(value <= total);
        require(total <= _allowed[from][msg.sender]);

        _allowed[from][msg.sender] = _allowed[from][msg.sender].sub(total);
        _transfer(from, to, value);
        _transfer(from, _issuer, _minFee);
        emit Fee(msg.sender, to, _issuer, _minFee);
        return true;
    }

    /**
     * @dev Transfer token for a specified addresses
     * @param from The address to transfer from.
     * @param to The address to transfer to.
     * @param value The amount to be transferred.
     */
    function _transfer(address from, address to, uint256 value) internal {
        require(value <= _balances[from]);
        require(to != address(0));
        _balances[from] = _balances[from].sub(value);
        _balances[to] = _balances[to].add(value);
        emit Transfer(from, to, value);
    }

    /**
     * @dev Internal function that mints an amount of the token and assigns it to
     * an account. This encapsulates the modification of balances such that the
     * proper events are emitted.
     * @param account The account that will receive the created tokens.
     * @param value The amount that will be created.
     */
    function _mint(address account, uint256 value) internal {
        require(account != 0);
        _totalSupply = _totalSupply.add(value);
        _balances[account] = _balances[account].add(value);
        emit Transfer(address(0), account, value);
    }

    /**
     * @dev Transfers token's foundation to new issuer
     * @param newIssuer The address to transfer ownership to.
     */
    function _changeIssuer(address newIssuer) internal {
        require(newIssuer != address(0));
        _issuer = newIssuer;
    }

    /**
     * @dev Change minFee
     * @param value minFee
     */
    function _changeMinFee(uint256 value) internal {
        _minFee = value;
    }

}

contract MyTRC21 is TRC21 {
    string private _name;
    string private _symbol;
    uint8 private _decimals;

    constructor (string memory name, string memory symbol, uint8 decimals, uint256 cap, uint256 minFee) public {
        _name = name;
        _symbol = symbol;
        _decimals = decimals;
        _mint(msg.sender, cap);
        _changeIssuer(msg.sender);
        _changeMinFee(minFee);
    }

    /**
     * @return the name of the token.
     */
    function name() public view returns (string memory) {
        return _name;
    }

    /**
     * @return the symbol of the token.
     */
    function symbol() public view returns (string memory) {
        return _symbol;
    }

    /**
     * @return the number of decimals of the token.
     */
    function decimals() public view returns (uint8) {
        return _decimals;
    }

}