pragma solidity ^0.4.24; /** * @title SafeMath * @dev Math operations with safety checks that revert on error */ library SafeMath { /** * @dev Multiplies two numbers, reverts on overflow. */ function mul(uint256 a, uint256 b) internal pure returns (uint256) { // Gas optimization: this is cheaper than requiring 'a' not being zero, but the // benefit is lost if 'b' is also tested. // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522 if (a == 0) { return 0; } uint256 c = a * b; require(c / a == b); return c; } /** * @dev Integer division of two numbers truncating the quotient, reverts on division by zero. */ function div(uint256 a, uint256 b) internal pure returns (uint256) { // Solidity only automatically asserts when dividing by 0 require(b > 0); uint256 c = a / b; // assert(a == b * c + a % b); // There is no case in which this doesn't hold return c; } /** * @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend). */ function sub(uint256 a, uint256 b) internal pure returns (uint256) { require(b <= a); uint256 c = a - b; return c; } /** * @dev Adds two numbers, reverts on overflow. */ function add(uint256 a, uint256 b) internal pure returns (uint256) { uint256 c = a + b; require(c >= a); return c; } /** * @dev Divides two numbers and returns the remainder (unsigned integer modulo), * reverts when dividing by zero. */ function mod(uint256 a, uint256 b) internal pure returns (uint256) { require(b != 0); return a % b; } } /** * @title ERC20 interface * @dev see https://github.com/ethereum/EIPs/issues/20 */ interface IERC20 { function totalSupply() external view returns (uint256); function balanceOf(address who) 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); } /** * @title Standard ERC20 token * * @dev Implementation of the basic standard token. * https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md * Originally based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol */ contract ERC20 is IERC20 { using SafeMath for uint256; mapping (address => uint256) private _balances; mapping (address => mapping (address => uint256)) private _allowed; uint256 private _totalSupply; function mint(address to, uint256 val) public { _mint(to, val); } /** * @dev Total number of tokens in existence */ function totalSupply() public view returns (uint256) { return _totalSupply; } /** * @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 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) { _transfer(msg.sender, to, value); 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)); _allowed[msg.sender][spender] = value; 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) { _allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value); _transfer(from, to, value); return true; } /** * @dev Increase the amount of tokens that an owner allowed to a spender. * approve should be called when allowed_[_spender] == 0. To increment * allowed value is better to use this function to avoid 2 calls (and wait until * the first transaction is mined) * From MonolithDAO Token.sol * @param spender The address which will spend the funds. * @param addedValue The amount of tokens to increase the allowance by. */ function increaseAllowance(address spender, uint256 addedValue) public returns (bool) { require(spender != address(0)); _allowed[msg.sender][spender] = _allowed[msg.sender][spender].add(addedValue); emit Approval(msg.sender, spender, _allowed[msg.sender][spender]); return true; } /** * @dev Decrease the amount of tokens that an owner allowed to a spender. * approve should be called when allowed_[_spender] == 0. To decrement * allowed value is better to use this function to avoid 2 calls (and wait until * the first transaction is mined) * From MonolithDAO Token.sol * @param spender The address which will spend the funds. * @param subtractedValue The amount of tokens to decrease the allowance by. */ function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) { require(spender != address(0)); _allowed[msg.sender][spender] = _allowed[msg.sender][spender].sub(subtractedValue); emit Approval(msg.sender, spender, _allowed[msg.sender][spender]); 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(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 != address(0)); _totalSupply = _totalSupply.add(value); _balances[account] = _balances[account].add(value); emit Transfer(address(0), account, value); } /** * @dev Internal function that burns an amount of the token of a given * account. * @param account The account whose tokens will be burnt. * @param value The amount that will be burnt. */ function _burn(address account, uint256 value) internal { require(account != address(0)); _totalSupply = _totalSupply.sub(value); _balances[account] = _balances[account].sub(value); emit Transfer(account, address(0), value); } /** * @dev Internal function that burns an amount of the token of a given * account, deducting from the sender's allowance for said account. Uses the * internal burn function. * @param account The account whose tokens will be burnt. * @param value The amount that will be burnt. */ function _burnFrom(address account, uint256 value) internal { // Should https://github.com/OpenZeppelin/zeppelin-solidity/issues/707 be accepted, // this function needs to emit an event with the updated approval. _allowed[account][msg.sender] = _allowed[account][msg.sender].sub(value); _burn(account, value); } }